TRANSCRIPTION FACTOR TFIIB SITES IMPORTANT FOR INTERACTION WITH PROMOTER-BOUND TFIID

Transcription initiation factor TFIIB recruits RNA polymerase II to th e promoter subsequent to interaction with a preformed TFIID-promoter c omplex. The domains of TFIIB required for binding to the TFIID-promote r complex and for transcription initiation have been determined. The c arboxyl-terminal two-thirds of TFIIB, which contains two direct repeat s and two basic residue repeats, is sufficient for interaction with th e TFIID-promoter complex. An extra 84-residue amino-terminal region, w ith no obvious known structural motifs, is required for basal transcri ption activity. Basic residues within the second basic repeat of TFIIB are necessary for stable interaction with the TFIID-promoter complex, whereas the basic character of the first basic repeat is not. Functio nal roles of other potential structural motifs are discussed in light of the present study.