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Mechanism and regulation of RNA Polymerase II transcription
Author(s) -
Hahn Steven
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.186.1
Subject(s) - transcription factor ii f , transcription factor ii a , coactivator , transcription factor ii e , transcription preinitiation complex , transcription factor ii b , general transcription factor , transcription factor ii d , rna polymerase ii , rna polymerase ii holoenzyme , transcription (linguistics) , biology , activator (genetics) , protein subunit , eukaryotic transcription , rna polymerase , microbiology and biotechnology , transcription factor , chemistry , biochemistry , promoter , rna , gene , gene expression , linguistics , philosophy
Recruitment of the RNA polymerase II (Pol II) transcription machinery at promoters involves the coordinated action of transcription activators and coactivators that facilitate positioning of Pol II and the general transcription factors at a promoter. This preinitiation complex (PIC) is poised to undergo a conformational change into an active conformation (open complex) with the melted template DNA strand in the enzyme active site. To understand the recruitment and transcription initiation steps, we have solved the structure of an activator‐coactivator complex and used biochemical probes to model the architecture of the PIC containing the general factor TFIIF. The yeast activator Gcn4 contains tandem acidic activation domains that interact with the Mediator coactivator subunit Gal11/Med15. The central Gcn4 activation domain adopts a helical structure when bound to Gal11 with three hydrophobic residues contacting a small hydrophobic surface of Gal11 with micromolar affinity. Unlike other activator‐target structures, there are no observed electrostatic interactions to help determine Gcn4 orientation. This simple and versatile interface can explain how acidic activators interact with multiple targets. The general transcription factor TFIIF functions at several steps in transcription initiation including PIC formation and start site selection. We find that in the PIC, two structured TFIIF domains bind Pol II at separate locations far from the active site with the TFIIF dimerization domain on the Pol II lobe and the winged helix domain of the TFIIF small subunit Tfg2 above the Pol II protrusion. Anchoring of these two structured TFIIF domains at separate sites locates an essential and unstructured region of Tfg2 near the Pol II cleft where it is in a position to interact with flexible regions of Pol II and the general factor TFIIB to promote initiation and start site selection.