TFIID is a general transcription factor which initiates preinitiation complex assembly through direct interaction with the TATA promoter element. It is a multisubunit complex consisting of a small TATA-binding polypeptide andother TATA-binding protein (TBP)-associated factors (TAFs). Although native TFIID can mediate both activator-independent (basal) and activator-dependent transcription in reconstituted systems, TBP can mediate only basal transcription. TAF II p100 (TBP-associated factor II100), also known as TAF5 or TAFII100, is the third largest subunit of human TFIID. It contains six WD40 repeats at the C-terminus and has an N-terminus capable of forming a flexible dimer. TAF II p100 plays an important role in forming the scaffold that is crucial for the assembly of the TFIID complex. TAF II p100 may also be involved in the stabilization of TAF interactions.