EP300 and cancer: CBP and EP300 are two transcriptional cofactors thatregulate gene expression24−26 through numerous PPIs27 and by acetylating histone and nonhistone proteins.28,29 CBP/EP300 are implicated in a wide range of diseases, such as cancer,inflammation, and developmental disorders.30−34 Several CBP/EP300 PROTACs based on different bromodomain(BRD)35−38 and histone acetyl transferase (HAT)39,40 ligands havebeen reported by our41 and other groups.42−50 In this work, we used high-throughput docking51 to identify an unprecedented 3-methylcinnoline fragmentas an acetyl-lysine mimic.