Histone acetyltransferase which may be involved in transcriptional activation (PubMed:12397079, PubMed:22020126). May influence the function of ATM (PubMed:15923642). As part of the MSL complex it is involved in acetylation of nucleosomal histone H4 producing specifically H4K16ac (PubMed:16227571, PubMed:16543150, PubMed:21217699, PubMed:22547026, PubMed:22020126). As part of the NSL complex it may be involved in acetylation of nucleosomal histone H4 on several lysine residues (PubMed:20018852, PubMed:22547026). That activity is less specific than the one of the MSL complex (PubMed:20018852, PubMed:22547026). Can also acetylate TP53/p53 at 'Lys-120'.