Scaffold subunit of various histone acetyltransferase (HAT) complexes, such as the MOZ/MORF and HBO1 complexes, which have a histone H3 acetyltransferase activity (PubMed:16387653, PubMed:26620551, PubMed:26677226). Plays a role in DNA replication initiation by directing KAT7/HBO1 specificity towards histone H3 'Lys-14' acetylation (H3K14ac), thereby facilitating the activation of replication origins (PubMed:26620551). Component of the MOZ/MORF complex which has a histone H3 acetyltransferase activity (PubMed:16387653). Component of some HBO1 complex composed of KAT7/HBO1, MEAF6, ING4 or ING5, and BRPF3 (PubMed:26620551). Component of the MOZ/MORF complex composed at least of ING5, KAT6A, KAT6B, MEAF6 and one of BRPF1, BRD1/BRPF2 and BRPF3 (PubMed:16387653, PubMed:18794358). Interacts with KAT7/HBO1; the interaction is direct (PubMed:26677226).