Gcn4 activator targets Gcn5 histone acetyltransferase to specific promoters independently of transcription

Histone acetylation correlates well with transcriptional activity, and hist one acetyltransferases (HATs) selectively regulate subsets of target genes by mechanisms that remain unclear. Here, we provide in vivo evidence that t he yeast transcriptional activator Gcn4 recruits Gcn5 HAT complexes to sele ctive promoters positioned in natural or ectopic locations, thereby creatin g local domains of histone H3 hyperacetylation and subsequent transcription al activation. A significant portion of the Gcn4-targeted histone acetylati on by Gcn5 is independent of transcriptional activity. These observations p rovide strong evidence for promoter-selective, targeted histone acetylation by Gcn5 that facilitates transcription in a causal fashion. In addition, G cn5 also functions in an untargeted manner to acetylate H3 on a genome-wide scale.