Transcript Structure of a six-finger transcription factor IIIA complex

Structure of a six-finger
transcription factor IIIA complex
In DNA recognition
Hui 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.
Proc 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
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Zinc fingers
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TFIIIA complex
(transcription factor IIIA complex )
The tripartite promoter containing
* box A
* intermediate element (IE)
* box C sequences
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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
Different configuration
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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
Crystallographic assignment of zinc fingers and DNA
bases to locations within the complex
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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
DNA majorgroove
contacts with
each of the
zinc fingers 1,
2, 3, and 5
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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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