Gene regulation Ch 8 pp 280 -292. What will I learn? THAT; 1.Gene regulation is at the heart of...
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Transcript of Gene regulation Ch 8 pp 280 -292. What will I learn? THAT; 1.Gene regulation is at the heart of...
What will I learn?What will I learn?
THAT;
1. Gene regulation is at the heart of development
2. The most important part of a gene is its regulatory region, because;1. It determines how, when, and by how much a
gene is activated
2. The combination of proteins which bind to this region determine activation (or repression)
Definition of gene regulationDefinition of gene regulation
• Regulation of gene expression (gene regulation) is the cellular control of the amount and timing of the appearance of the functional product of a gene.
The Story of ‘Eve’The Story of ‘Eve’
• This example illustrates why gene regulation is fundamental to development
• The Players– Drosophila embryo– Even-skipped gene– Regulatory proteins
• Bicoid• Hunchback• Giant• Kruppel
The setupThe setup
• In Drosophila, the fertilized egg initially performs many rounds of mitosis without cell division - resulting in a cell with many nuclei
• The embryo is 400 um long and 160 um wide• It has anterior (that will eventually develop
into the head) and a posterior (that will develop into the abdomen)
Act 1Act 1
• Removing the cytoplasm from the anterior will result in the failure to develop a head
• Replacing this cytoplasm with some taken from the posterior of another embryo will result in an embryo with two tails
Act 2
• Labeling of the 4 proteins - Bicoid, Hunchback, Giant, Kruppel with fluorescent dyes reveals that they are not randomly located inside the cell...
Act 2 continued
• The nuclei are therefore bathed in differing concentrations of these four proteins - depending on their position in the cell.
Act 3
• Even-skipped - ‘EVE’
• It is a master regulatory gene whose product is a master regulatory protein
• This genes’ promoter region has the ability to bind to all four of the regulatory proteins
Act 4 The Reporter
• A reporter gene is an artificial DNA construct used to reveal information
• Lac Z reporter gene is used extensively• GAL (galactosidase) - Hydrolyzes colorless
galactosides to yield colored products. • Attach different parts of the promoter region of
the ‘eve’ gene to LacZ to determine if that region is bound and activated by proteins.
• Check the web on this please!
08_19_eve.stripe.2.jpg
The same STRIPE 2 region actually has binding sites for all four of regulatory proteins - Bicoid and Hunchback are activators of this region and Giant and Kruppel are repressors.
Curtain
• The regulatory region of ‘Eve’ extends more than 20,000 bp
• It is thought to bind more than 20 different proteins
• It is very sensitive to the position of the gene (nucleus) within the developing giant cell
• The different concentrations of the different proteins impact on the expression of ‘Eve’
Gene Expression
• Regions huge distances from the gene have an effect on the activation (or repression) of that gene
• These regions bind proteins that then interact, by DNA looping, with the local promoter regions
• A combination effect is seen - and thus the term combinatorial control is used
Combinatorial controlCombinatorial control
• Not just by how much are genes regulated but also when.
• It is akin to an orchestra….
• It is fantastic coordination at each gene locus
Maintaining the status quo- with respect to gene
regulation- through cell division
Maintaining the status quo- with respect to gene
regulation- through cell division
08_24_chromatin.state.jpg
Inactive genes are kept inactive by regulatory proteins bound to the DNA, and active genes are kept active! How, see below
08_25_eye.on.leg.jpgActivation of the wrong regulator can have devastating effects
One can move cells to new locations may lead to monsters!!