TFIIA pol II promoter:TFIID complex pol II promoter:TFIID:TFIIA:TFIIB complex Binding of TFIIA and TFIIB to the pol II promoter:TFIID complex Authored: Reinberg, D, 2003-09-11 07:42:30 Edited: Joshi-Tope, G, 0000-00-00 00:00:00 Pubmed8946909 Reactome Database ID Release 43109637 Reactome, http://www.reactome.org ReactomeREACT_266 The general transcription factor TFIIB is a single polypeptide of approximately 35 kDa. There is a Zn-binding domain near the N terminus of TFIIB, and the C-terminal domain encompasses two imperfect repeats; between the N and C termini is a phylogenetically conserved region. The C terminus interacts with TBP and RNA Polymerase II, whereas the N terminus interacts with factor TFIIF and RNA polymerase II. TFIIB is a sequence-specific factor, and it interacts with the BRE element within the promoter.<p>TFIIB interacts with the Rpb1 subunit of RNA polymerase II to define transcription strat sites. Several activators directly bind TFIIB, and stimulate transcription. The N-terminus and the C-terminus can participate in intramolecular interactions, and this can be disrupted by specific activators by causing a conformational change in TFIIB.<p> TFIIA also binds the preinitiation complex along with TFIIB. However, TFIIA is not required for accurate initiation, but rather functions as a coactivator of transcription.