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The transcription initiation factor TFIID is a multimeric protein complex composed of TATA box–binding protein (TBP) and many TBP-associated factors (TAF_IIs). TAF_IIs are important cofactors that mediate activated transcription by providing interaction sites for distinct activators. Here, we present evidence that human TAF_II250 and its homologs in Drosophila and yeast have histone acetyltransferase (HAT) activity in vitro. HAT activity maps to the central, most conserved portion of dTAF_II230 and yTAF_II130. The HAT activity of dTAF_II230 resembles that of yeast and human GCN5 in that it is specific for histones H3 and H4 in vitro. Our findings suggest that targeted histone acetylation at specific promoters by TAF_II250 may be involved in mechanisms by which TFIID gains access to transcriptionally repressed chromatin.