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This gene encodes the general transcription factor IIB, one of the ubiquitous factors required for transcription initiation by RNA polymerase II. The protein localizes to the nucleus where it forms a complex (the DAB complex) with transcription factors IID and IIA. Transcription factor IIB serves as a bridge between IID, the factor which initially recognizes the promoter sequence, and RNA polymerase II. A TFIIB conformational change is critical for the formation of activator-dependent transcription complexes. Collapse of the transcription bubble defines the RNA polymerase II promoter clearance transition. Data show that human TATA box binding protein (TBP) can use a shared surface to interact with two different transcription factor IIB (TFIIB) family members to initiate transcription by different RNA polymerases. Results identify a small nonconserved surface of the transcription factor TFIIB zinc ribbon that is required for RNA polymerase II (pol II) transcription in vivo and for different types of basal pol II transcription in vitro. TFIIB interacts with SP1/SP3 at the SP1 site, besides its association with EAR3 and the TATA-less core promoter region. The groove in the first cyclin repeat of TFIIB is identified as the FCP1-binding site of TFIIB core domain (TFIIBc), consisting of several hydrophobic and several basic amino acids. The structural role of Zn2+ binding to the the zinc-ribbon domain of TFIIB was analysed. In addition to its role in regulating TBP binding to a TATA box, the TBP surface is unexpectedly involved in TBP association with all three TFIIB family members. Interaction with vitamin D receptor helix H10 residues. Lack of role in bending of TATA-binding protein simultaneously with promotoer DNA.
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