Isolation and partial characterization of three histone-specific acetyltransferases from Artemia

Three histone-specific acetyltransferases have been characterized in Artemia by the criteria of cell compartmentation, chromatographic behaviour, substrate specificity and regulatory properties. Acetyltransferase I is a chromatin-bound enzyme with affinity for DNA-cellulose. This enzyme can acetylate histones H1, H3 and H4, but the acetylation of H1 is markedly inhibited in the presence of H4. Acetyltransferases II and III are cytoplasmic and were resolved by phosphate elution from hydroxyapatite. The isoenzyme II is highly specific for histone H4, whose acetylation is increased in the presence of H1. The acetyltransferase III is active with the three histone fractions, but its specificity is modulated through the cooperation of H4 (as inhibitor of the acetylation of H1) and H1 (as activator of H4 acetylation). Spermine was confirmed as a specific activator of the acetyltransferase I, with subsaturating concentrations of H3 as substrate.