Histone H3 reader that is required for the ATAC complex- mediated maintenance of histone acetylation and gene activation (PubMed:30217978). Component of the ATAC complex, a complex with histone acetyltransferase activity on histones H3 and H4 (PubMed:19103755). {ECO:0000269|PubMed:19103755, ECO:0000269|PubMed:30217978}. This is the function of ZZZ3 (zinc finger ZZ-type containing 3, Ensembl gene identifier ENSG00000036549).