THE TAF(II)250 SUBUNIT OF TFIID HAS HISTONE ACETYLTRANSFERASE ACTIVITY

The transcription initiation factor TFIID is a multimeric protein comp lex composed of TATA box-binding protein (TBP) and many TBP-associated factors (TAF(II)s). TAF(II)s are important cofactors that mediate act ivated transcription by providing interaction sites for distinct activ ators. Here, we present evidence that human TAF(II)250 and its homolog s in Drosophila and yeast have histone acetyltransferase (HAT) activit y in vitro. HAT activity maps to the central, most conserved portion o f dTAF(II)230 and yTAF(II)130. The HAT activity of dTAF(II)230 resembl es that of yeast and human GCN5 in that it is specific for histones H3 and H4 in vitro. Our findings suggest that targeted histone acetylati on at specific promoters by TAF(II)250 may be involved in mechanisms b y which TFIID gains access to transcriptionally repressed chromatin.