The CREB binding protein (CBP) contains a bromodomain which recognises the acetylation of lysine 56 of histone H3 (H3K56ac). This model displays the hydrogen bonds and hydrophobic interactions which preferentially anchor the H3K56ac peptide into the bromodomain of CBP over other acetylated histones. CBP also possesses a histone acetyltransferase (HAT) domain which promotes the acetylation of free histones by H3K56ac. Therefore H3K56ac binds to CBP which activates its HAT domain which in turn causes acetylation of free histones and chromatin assembly. This has a dramatic impact on the functioning of the cell by influencing replication, transcription and DNA repair. In addition H3K56ac exchanges H2A with H2AZ and creates stronger binding of H3 to histone chaperone chromatin assembly factor-1 (CAF-1) and RH106, promoting replication coupled nucleosome assembly. Therefore H3K56ac binding to CBP has a dynamic function, working to assemble or disassemble the nucleosome through chromatin remodelling.
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