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:24065767, PubMed:27939640). Plays a key role in HBO1 complex by directing KAT7/HBO1 specificity towards histone H3 ‘Lys-14’ acetylation (H3K14ac) (PubMed:24065767). Some HAT complexes preferentially mediate histone H3 ‘Lys-23’ (H3K23ac) acetylation (PubMed:27939640). Positively regulates the transcription of RUNX1 and RUNX2 (PubMed:18794358).