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

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TFIIIA complex(transcription factor IIIA

complex )

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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