EP300 and cancer: BRCA1 has been implicated in transcriptional regulation through several mechanisms including direct interactions with the p300/CBP activator complex35 and maintenance of the heterochromatin structure through ubiquitylation of histone H2A.36 Here we show that some of these changes are associated with distinct patterns of chromatin-associated H3K9 and H3K27 acetylated marks, leading to differences in cellular responses to HDACi and to an IFN-γ gene signature detectable in BRCA1-mutated cancer cells.