EVOLUTIONARY CONSERVATION OF HUMAN TATA-BINDING-POLYPEPTIDE-ASSOCIATED FACTORS TAF(II)31 AND TAF(II)80 AND INTERACTIONS OF TAF(II)80 WITH OTHER TAFS AND WITH GENERAL TRANSCRIPTION FACTORS

Human transcription initiation factor TFIID is composed of the TATA-binding polypeptide (TBP) and at least 13 TBP-associated factors (TAFs) that collectively or individually are involved in activator-dependent transcription. To investigate protein-protein interactions involved in TFIID assembly and in TAF-mediated activator functions, we have cloned and expressed cDNAs encoding human TAF(II)80 and TAF(II)31. Coimmunoprecipitation assays showed that TAF(II)80 interacted with TAF(II)250, TAF(II)31, TAF(II)20, and TBP, but not with TAF(II)55. Similar assays showed that TAF(II)80 interacted with TFIIE alpha and with TFIIF alpha (RAP74) but not with TFIIB, TFIIE beta, or TFIIF beta (RAP30). Further studies with TAF(II)80 mutations revealed three distinct interaction domains which fall within regions conserved in human TAF(II)80, Drosophila TAF(II)60, and yeast TAF(II)60. The N terminus of TAF(II)80 (residues 1-100) interacts with both TAF(II)31 and TAF(II)20, while two C-terminal regions are involved, respectively, in interactions with TAF(II)250 and TPIIF alpha (RAP74) (residues 203-276) and with TBIP and TFIIE alpha (residues 377-505). The interactions between TAF(II)80 and general factors TFIIE alpha and TFIIF alpha (RAP74) could be important for recruitment of GTFs during activator-dependent transcription, Because TAPs 80, 31, and 20 show sequence similarities to histones H4, H3, and H2B, as well as some parallel interactions, this subset of TAFs may form a related core structure within TFIID.