Specific interactions and potential functions of human TAF(II)100

Human transcription initiation factor TFIID contains the TATA-binding protein (TBP) and several TBP-associated factors (TAFs), To investigate the structural organization and function of TFIID, we have cloned and expressed a cDNA encoding the third largest human TFIID subunit, hTAF(II)100, Immunoprecipitation studies demonstrate that hTAF(II)100 is an integral subunit that is associated with all transcriptionally-competent forms of TFIID, They further suggest that at least part of the N-terminal region lies on the surface of TFIID, while a C-terminal region containing conserved WD-40 repeats appears inaccessible, Both in vivo and in vitro assays indicate that hTAF,100 interacts strongly with the histone H4-related hTAF(II)80 and the histone H3-related hTAF(II)31, as well as a stable complex comprised of both hTAF(II)80 and hTAF(II)31, Apparently weaker interactions of hTAF(II)100 with TBP, hTAF(II)250, hTAF(II)28, and hTAF(II)20, but not hTAF(II)55, also have been observed. These results suggest a role for hTAF,100 in stabilizing interactions of TAFs, especially the histone-like TAFs, in TFIID, In addition, functional studies show that anti-hTAF(II)100 antibodies selectively inhibit basal transcription from a TATA-less initiator-containing promoter, relative to a TATA containing promoter, suggesting a possible core promoter-specific function for hTAF(II)100.