EP300 and Familial prostate cancer: Surprisingly, while both CCS1477 and GNE-049 significantly decreased the p300/CBP-catalyzed H3K27ac mark, we saw modest to no decrease in the abundance of H2BNTac in the treated prostate cancer cells (Figures 3A and S2A), suggesting that reader bromodomain inhibitors lead to only a partial inhibition of p300/CBP activity.