Cloning of an Intrinsic Human TFIID Subunit That Interacts with Multiple Transcriptional Activators

TFIID is a multisubunit protein complex comprised of the TATA-binding protein (TBP) and multiple TBP-associated factors (TAFs). The TAFs in TFIID are essential for activator-dependent transcription. The cloning of a complementary DNA encoding a human TFIID TAF, TAF II 55, that has no known homolog in Drosophila TFIID is now described. TAF II 55 is shown to interact with the largest subunit (TAF II 230) of human TFIID through its central region and with multiple activators—including Sp1, YY1, USF, CTF, adenoviral E1A, and human immunodeficiency virus-type 1 Tat proteins—through a distinct amino-terminal domain. The TAF II 55-interacting region of Sp1 was localized to its DNA-binding domain, which is distinct from the glutamine-rich activation domains previously shown to interact with Drosophila TAF II 110. Thus, this human TFIID TAF may be a co-activator that mediates a response to multiple activators through a distinct mechanism.