positive charge on lysines. Acetylation of histone H4 on lysine 16 (H4K16ac) is especially important for chromatin structure and function in a variety of eukaryotes and is catalyzed by specific histone lysine acetyltransferases (HATs). H4K16 is particularly interesting because this is the only acetylatable site of the H4 N-terminal tail, and can influence the formation of a compact higher-order chromatin structure. Hypoacetylation of H4K16 appears to cause delayed recruitment of DNA repair proteins to sites of DNA damage in a mouse model of the premature aging syndrome Hutchinson Gilford progeria. H4K16Ac also has roles in transcriptional activation and the maintenance of euchromatin. List of H4 modifications H4S1p H4R3me H4K5ac H4K8ac H4K12ac H4K16ac H4K16adp H4K20me H4S47o-p H4K91ac H4K91ub See also Histone code#Histone H4 References See also nucleosome histone chromatin Other histone proteins involved in chromatin: H1 H2A H2B H3