Initiation of transcription by RNA polymerase II requiresthe assistance of TATA box-binding protein (TBP, MIM 600075) andTBP-associated factors, or TAFs (e.g., TAF2B, MIM 604912), in 2distinct complexes, TFIID and B-TFIID. The TFIID complex iscomposed of TBP and more than 8 TAFs. However, the majority of TBPis present in the B-TFIID complex, which is composed of TBP andTAFII170, also called TAF172, and has DNA-dependent ATPaseactivity.