Transcription factor II B

Transcription Factor II B (TFIIB) is a general transcription factor that is involved in the formation of the RNA polymerase II preinitiation complex (PIC) and aids in stimulating transcription initiation. TFIIB is localised to the nucleus and provides a platform for PIC formation by binding and stabilising the DNA-TBP (TATA-binding protein) complex and by recruiting RNA polymerase II and other transcription factors. It is encoded by the TFIIB gene.

Structure

TFIIB is a single 33kDa polypeptide consisting of 316 amino acids. It was originally thought to be essential at all promoters in order to recruit RNA polymerase II and initiate transcription, however recent research has shown that a depletion in TFIIB is not lethal to cells and transcription levels are not significantly affected. This is because over 90% of mammalian promoters do not contain a BRE (B recognition element) or TATA box sequence which are required for TFIIB to bind. In addition to this, TFIIB levels have been shown to fluctuate in different types of cell, and at different points in the cell cycle, supporting the evidence that it is not required for all RNA polymerase II transcription.