Structure of a six-finger transcription factor IIIA
complex In DNA recognitionHui Pengtao
Advisor: Dr. Li
Structure of a six-finger transcription factor IIIA
complex
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Zinc fingers
* Positioned in the major
groove and across the minor groove of DNA
* Span the entire length of the duplex
* Show how TFIIIA can recognize separated DNA sequences in the major groove.
3Proc Natl Acad Sci U S A. 1998 March 17; 95(6): 2938–2943.Differing roles for zinc fingers in DNA recognition: Structure of a six-finger transcription factor IIIA complex
Zinc fingers
4
200
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8 0
2.p
se
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8 0
3.p
se
TFIIIA complex(transcription factor IIIA
complex )
5
The tripartite promoter containing
* box A
* intermediate element (IE)
* box C sequences
Description of TFIIIA Structure
* Six-finger protein stretches along the
entire length of the 31-bp duplex * The current protein model includes
amino acids 10–188 of TFIIIA * fingers 1–2–3 adopt a completely
different configuration than do fingers 4–5–6 (A)
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Six-fingers
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Different configuration2007221107100008 01.pse
Six-fingers* 1 Fingers 1–2–3 are separated by typical linker
sequences, wrap smoothly around the major groove
2 Contacts are made with DNA bases mainly on the noncoding strand of the 5S rRNA gene.
* 1 Fingers 4–5–6, run along one side of the DNA double helix, form an open, extended structure.
2 only finger 5 makes contacts with bases in the major groove.
3 The two flanking fingers, 4 and 6, straddle the neighboring minor grooves.
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Six-fingers
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Crystallographic assignment of zinc fingers and DNA bases to locations within the complex
Six-fingers• Each TFIIIA finger is
folded in the classical way around a Zn(II) ion
• Zinc finger binding there are increases in the depth and width of the major groove
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Linker sequence * The consensus pentapeptide linker
sequence Thr-Gly-Glu-Lys-Pro * associate with major-groove
binding fingers * appear only twice in this NH2-
terminal segment of TFIIIA
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Zinc Finger–DNA Interactions
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DNA major-groove contacts with each of the zinc fingers 1, 2, 3, and 5
TFIIIA–DNA complex The structure of the TFIIIA–DNA complex
shows how zinc fingers have been deployed to bind to separated promoter elements
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--BY HUI PENGTAO
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