N1 Eukaryotic transcription factors

N2 Examples of transcriptional regulation

Section NmdashRegulation of transcription in eukaryotes

Molecular Biology

N1 Eukaryotic transcription factors

Transcription factor domain structureTranscription factors other than the general transcription factors of the basal transcription complex were firt identified through their affinity for specific motifs in promoters upstream regulatory elements of enhancer regions These factors have two distinct activities Firstly they bind specifically to their DNA-binding site and secondly they activate transcription These activities can be assigned to separate protein domains called activation domains and DNA-binding domains In addition many transcription factor occur as homo- or heterodimers held togather by dimerization domains A few transcription factors have ligand-binding of an accessory small molecule

Molecular Biology

Prokaryotesbull1048766 Helix-turn-helix

Eukaryotesbull1048766 Zinc finger bull1048766 Leucine zipperbull1048766 Helix-loop-helix

Transcription factor domain structure

Molecular Biology

DNA-binding domains The helix-turn-helix domain

Characteristic

bull This domain contains a 60-amino acid homeodomain which is encoded by a sequence called the homeboxbull This domain consists of four alpha-helices in which helices II and III are at right angles to each other and are sparated by a beta-turnbull this domain binds so that one helix know as the recognition helix lies partly in the major groove and interacts with the DNA

Molecular Biology

DNA-binding domains the zinc finger domain

Many many examples10487661048766 estrogen receptor TFIIIA10487661048766 Zn++ coordinated by10487661048766 2 Cys + 2 His = C2H2-type10487661048766 X Cys = CysX X = 4 or 61048766

N-terminal end10487661048766 Often motif repeated 2 to 13 times10487661048766 Bind to DNA major grove10487661048766

Molecular Biology

Zipper every 7th residue is a Leu Hydrophobic interface

Dimerization domains leucine zippers

Leucine Zipper proteins contain a hydrophobic leucine residue at every sventh position in a region that is often at the C-terminal part of the DNA-binding domain These leucines lie in an alpha-helical region and the regular repeat of these residues forms a hydrophobic surface on one side of the alpha-helix with a leucine every second turn of the helix

Molecular Biology

The N-terminal basic domains of each helix form a symmetrical structure in which each basic domain lies along the DNA in opposite directions interacting with a symmetrical DNA recognition site so that the protein in effect forms a clamp around the DNA

Dimerization domains leucine zippers

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

N1 Eukaryotic transcription factors

Transcription factor domain structureTranscription factors other than the general transcription factors of the basal transcription complex were firt identified through their affinity for specific motifs in promoters upstream regulatory elements of enhancer regions These factors have two distinct activities Firstly they bind specifically to their DNA-binding site and secondly they activate transcription These activities can be assigned to separate protein domains called activation domains and DNA-binding domains In addition many transcription factor occur as homo- or heterodimers held togather by dimerization domains A few transcription factors have ligand-binding of an accessory small molecule

Molecular Biology

Prokaryotesbull1048766 Helix-turn-helix

Eukaryotesbull1048766 Zinc finger bull1048766 Leucine zipperbull1048766 Helix-loop-helix

Transcription factor domain structure

Molecular Biology

DNA-binding domains The helix-turn-helix domain

Characteristic

bull This domain contains a 60-amino acid homeodomain which is encoded by a sequence called the homeboxbull This domain consists of four alpha-helices in which helices II and III are at right angles to each other and are sparated by a beta-turnbull this domain binds so that one helix know as the recognition helix lies partly in the major groove and interacts with the DNA

Molecular Biology

DNA-binding domains the zinc finger domain

Many many examples10487661048766 estrogen receptor TFIIIA10487661048766 Zn++ coordinated by10487661048766 2 Cys + 2 His = C2H2-type10487661048766 X Cys = CysX X = 4 or 61048766

N-terminal end10487661048766 Often motif repeated 2 to 13 times10487661048766 Bind to DNA major grove10487661048766

Molecular Biology

Zipper every 7th residue is a Leu Hydrophobic interface

Dimerization domains leucine zippers

Leucine Zipper proteins contain a hydrophobic leucine residue at every sventh position in a region that is often at the C-terminal part of the DNA-binding domain These leucines lie in an alpha-helical region and the regular repeat of these residues forms a hydrophobic surface on one side of the alpha-helix with a leucine every second turn of the helix

Molecular Biology

The N-terminal basic domains of each helix form a symmetrical structure in which each basic domain lies along the DNA in opposite directions interacting with a symmetrical DNA recognition site so that the protein in effect forms a clamp around the DNA

Dimerization domains leucine zippers

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Prokaryotesbull1048766 Helix-turn-helix

Eukaryotesbull1048766 Zinc finger bull1048766 Leucine zipperbull1048766 Helix-loop-helix

Transcription factor domain structure

Molecular Biology

DNA-binding domains The helix-turn-helix domain

Characteristic

bull This domain contains a 60-amino acid homeodomain which is encoded by a sequence called the homeboxbull This domain consists of four alpha-helices in which helices II and III are at right angles to each other and are sparated by a beta-turnbull this domain binds so that one helix know as the recognition helix lies partly in the major groove and interacts with the DNA

Molecular Biology

DNA-binding domains the zinc finger domain

Many many examples10487661048766 estrogen receptor TFIIIA10487661048766 Zn++ coordinated by10487661048766 2 Cys + 2 His = C2H2-type10487661048766 X Cys = CysX X = 4 or 61048766

N-terminal end10487661048766 Often motif repeated 2 to 13 times10487661048766 Bind to DNA major grove10487661048766

Molecular Biology

Zipper every 7th residue is a Leu Hydrophobic interface

Dimerization domains leucine zippers

Leucine Zipper proteins contain a hydrophobic leucine residue at every sventh position in a region that is often at the C-terminal part of the DNA-binding domain These leucines lie in an alpha-helical region and the regular repeat of these residues forms a hydrophobic surface on one side of the alpha-helix with a leucine every second turn of the helix

Molecular Biology

The N-terminal basic domains of each helix form a symmetrical structure in which each basic domain lies along the DNA in opposite directions interacting with a symmetrical DNA recognition site so that the protein in effect forms a clamp around the DNA

Dimerization domains leucine zippers

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

DNA-binding domains The helix-turn-helix domain

Characteristic

bull This domain contains a 60-amino acid homeodomain which is encoded by a sequence called the homeboxbull This domain consists of four alpha-helices in which helices II and III are at right angles to each other and are sparated by a beta-turnbull this domain binds so that one helix know as the recognition helix lies partly in the major groove and interacts with the DNA

Molecular Biology

DNA-binding domains the zinc finger domain

Many many examples10487661048766 estrogen receptor TFIIIA10487661048766 Zn++ coordinated by10487661048766 2 Cys + 2 His = C2H2-type10487661048766 X Cys = CysX X = 4 or 61048766

N-terminal end10487661048766 Often motif repeated 2 to 13 times10487661048766 Bind to DNA major grove10487661048766

Molecular Biology

Zipper every 7th residue is a Leu Hydrophobic interface

Dimerization domains leucine zippers

Leucine Zipper proteins contain a hydrophobic leucine residue at every sventh position in a region that is often at the C-terminal part of the DNA-binding domain These leucines lie in an alpha-helical region and the regular repeat of these residues forms a hydrophobic surface on one side of the alpha-helix with a leucine every second turn of the helix

Molecular Biology

The N-terminal basic domains of each helix form a symmetrical structure in which each basic domain lies along the DNA in opposite directions interacting with a symmetrical DNA recognition site so that the protein in effect forms a clamp around the DNA

Dimerization domains leucine zippers

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

DNA-binding domains the zinc finger domain

Many many examples10487661048766 estrogen receptor TFIIIA10487661048766 Zn++ coordinated by10487661048766 2 Cys + 2 His = C2H2-type10487661048766 X Cys = CysX X = 4 or 61048766

N-terminal end10487661048766 Often motif repeated 2 to 13 times10487661048766 Bind to DNA major grove10487661048766

Molecular Biology

Zipper every 7th residue is a Leu Hydrophobic interface

Dimerization domains leucine zippers

Leucine Zipper proteins contain a hydrophobic leucine residue at every sventh position in a region that is often at the C-terminal part of the DNA-binding domain These leucines lie in an alpha-helical region and the regular repeat of these residues forms a hydrophobic surface on one side of the alpha-helix with a leucine every second turn of the helix

Molecular Biology

The N-terminal basic domains of each helix form a symmetrical structure in which each basic domain lies along the DNA in opposite directions interacting with a symmetrical DNA recognition site so that the protein in effect forms a clamp around the DNA

Dimerization domains leucine zippers

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Zipper every 7th residue is a Leu Hydrophobic interface

Dimerization domains leucine zippers

Leucine Zipper proteins contain a hydrophobic leucine residue at every sventh position in a region that is often at the C-terminal part of the DNA-binding domain These leucines lie in an alpha-helical region and the regular repeat of these residues forms a hydrophobic surface on one side of the alpha-helix with a leucine every second turn of the helix

Molecular Biology

The N-terminal basic domains of each helix form a symmetrical structure in which each basic domain lies along the DNA in opposite directions interacting with a symmetrical DNA recognition site so that the protein in effect forms a clamp around the DNA

Dimerization domains leucine zippers

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

The N-terminal basic domains of each helix form a symmetrical structure in which each basic domain lies along the DNA in opposite directions interacting with a symmetrical DNA recognition site so that the protein in effect forms a clamp around the DNA

Dimerization domains leucine zippers

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

bull acidic activation domains Comparison of the transactivation domains of yeast Gcn4 and Gal4 mammalian glucocorticoid receptor and herpes virus activator VP16 shows that they have a very high proportion of acidic amino acids These have been called acidic activation domains or lsquoacid blobsrsquo or lsquonegative noodlesrsquo and are characteristic of many transcription activation domains It is still uncertain what other features are required for these regions to function as efficient transcription activation domains

bull Glutamine-rich domains were first identified in two activatio regions of the transcription factor SP1 As with acidic domains the proportion of glutamine residues seems to be more important than overall structure Domain swap experiments between glutamine-rich transcactivation regions from the diverse transcription factors SP1 and the Drosophila protein Antennapedia showed that these domains could substitue for each other

bull Proline-rich domains have been identified in several transcription factors As with glutamine a continuous run of proline residues can activate transcription This domain is found for example in the c-Jun AP2 and Oct-2 transcription factors

Transcription activation domains

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Repression of transcription may occur by indirect interference with the function of an activator This may occur by

bull Blocking the activator DNA-binding site

bull Formation of a non-DNA-binding complex

bull Masking of the activation domain without preventing DNA binding

Repressor domains

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Targets for transcriptional regulation

The presence of diverse activation domains raises the question of whether the each have the same target in the basal transcription complex or different target for the activation of transcription They are distinguishable from each other since the acidic activation domain can activate transcription from a downstream enhancer site while the proline domain only activates weakly and the glutamine domain not at all Proposed targets of different transcriptional activators include

bull Chromatin structure

bull Interaction with TFIID through specific TAFIIS

bull Interaction with TFIIB

bull Interaction or modulation of the TFIIH complex activity leading to differential phosphorylation of the CTD of RNA Pol II

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

N2 Examples of transcriptional regulation

Constitutive transcription factors SP1

bull SP1 binds to a GC-rich sequence with the consensus sequence GGGCGC

bull It is a constitutive transcription factor whose binding site is found in the promoter of many housekeeping genesbullIt contains the zinc finger motifs and has been shown to contain two glutamine-rich transactivation domains

bull SP1 have been shown to interact specifically with TAFII 110 onw of thw TAFIIs which bind to the TATA binding protein to make up TFIID

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Hormonal regulation steroid hormone receptorsMany transcription factors are activated by hormones which are secreted by one cell type and transmit a signal to a different cell type One class of hormones the steroid hormones are lipid soluble and can diffuse through cell membranes to interact with transcripton factors called steroid hormine receptors In the absence of the steroid hormone the receptors is bound to an inhibit and located in the cytoplasm The steroid hormone bind to the receptor and releases the receptor from the inhibitor allowing the receptor to dimerize and translocate to the nucleus The DNA-binding domain of the steroid hormone receptor then interacts with its specific DNA-binding sequence or response element and this gives reise to activation of the target gene

steroid

Dissociation and dimerization

Nuclear translocation

Glucocorticoid receptor

Inibitor

(HSP90)

Glucocorticoid response element

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Interferon-γ

INF- γ receptor

Unphosphorylated STAT 1αmonoers Phosphorylation

DmerizationPhosphorylated STAT1α dimer

Nuclear translocation

Response element

Many hormones do not diffuse into the cell Instead they bind to cell-surface receptors and pass a sgnal to proteins within the cell through a process called signal transduction This process often involves protein phosphorylation

Interferon-γ induces phosphorylation of a transcription factor called STAT1α through JAK When STAT1αbecmes phosphorylated at a specific tyrosine residue it is able to form a homodimer which moves from the cytoplasm into the nucleus

Regulation phosphorylation STAT proteins

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Transcription elongation HIV Tat

Initiation complex

Activated TFIIH phosphorylates CTD of RNA Pol II

Polymerase

Cellular factors

Tat

TAR stem-loop structure

Tat-TAR cellular factor complex activates TFIIH

Precious transcript loops backwards to interact with the initiation compex

Human immunodeficiency virus (HIV) encodes an activatir protein called Tat which is required for productive HIV gene expression Tat binds to an RNA stem-loop structuire called TAR which is present in the 5rsquo-untranslated region of all HIV RNAs just after the HIV transcription start site The predominant effect of Tat in mammalian cells lies at the level of transcription elongation

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesmyoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Cell determination myoD

Fig 2110

The cell is now ireversibly determined

The cell is now fully differentiated

myoD is a ldquomaster controlrdquo gene it makes a transcription factor that can activate other muscle specific genes

The embryonic precursor cell is still undifferentiated

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a master regulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

Fig 2110The cell is now fully differentiated

The cell is now ireversibly determined to become a muscle cell

成肌细胞

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

DNA

OFF OFF

OFFmRNA

mRNA mRNA mRNA mRNA

Anothertranscriptionfactor

MyoDMuscle cell(fully differentiated)

MyoD protein(transcription factor)

Myoblast (determined)

Embryonicprecursor cell

Myosin othermuscle proteinsand cell-cycleblocking proteins

Other muscle-specific genesMaster control gene myoDNucleus

Determination Signals from other cells activate a masterregulatory gene myoD

1

Differentiation MyoD protein activatesother muscle-specific transcription factors which in turn activate genes for muscle proteins

2

Determination and differentiation of muscle cells

The cell is now ireversibly determined

The cell is now fully differentiated

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Embryonic development homeodomain proteins

The homeobox is a conserved DNA sequence which encodes the helix-turn-helix DNA binding protein structure called the homeodomain The homeodomain was first discovered in the transcription factors encoded by homeptic genes of Drosophila

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology

Regulatory genes that control organ identity

Conserved from flies to mammals

Homeotic genes

Molecular Biology