Activator-dependent transcription from chromatin in vitro involving targeted histone acetylation by p300

The transcriptional coactivator p300 shows physical and functional interact ions with a diverse group of activators and contains an intrinsic acetyltra nsferase activity whose exact coactivator functions in the acetylation of n ucleosomal histones versus other factors are poorly documented. Here, we sh ow that p300 mediates acetyl-CoA-dependent transcription by GAL4-VP16 from a nucleosomal array template, that this involves p300 targeting by GAL4-VP1 6 and promoter-proximal histone acetylation prior to transcription, and tha t the affinities of different activators for p300 roughly correlate with co rresponding levels of p300-dependent transcription. These results indicate that activators recruit p300 to nucleosomal templates by direct interaction s and that bound p300 stimulates transcription, at least in part, by locali zed histone acetylation.