Practice question

TFIIB recognition elements BREu with consensus SSRCGCC and BREd RTDKKKK flank TATA box upstream and downstream respectively. They are recognized not by TBP but by TFIIB C-terminal cyclin domains that make major and minor groove contacts. Binding of TFIIB to BRE helps orient preinitiation complex and can confer directionality, as BREu upstream of TATA favors transcription in one orientation. BRE interaction also influences TFIIB-TBP affinity and modulates activation by activators. Many promoters lack BRE, using TATA alone for TFIIB recruitment via protein-protein interactions.