Different types of maize histone deacetylases are distinguished by a highly complex substrate and site specificity

Enzymes involved in histone acetylation have been identified as important t ranscriptional regulators. Maize embryos contain three histone deacetylase families: RPD3-type deacetylases (HD1-B), nucleolar phosphoproteins of the HD2 family, and a third form unrelated to RPD3 and HD2 (HD1-A). Here we fir st report on the specificity of deacetylases for core histones, acetylated histone H4 subspecies, and acetylated H4-lysine residues. HD1-A, HD1-B, and HD2 deacetylate all four core histones, although with different specificit y. However, experiments with histones from different sources (hyperacetylat ed MELC and chicken histones) using antibodies specific for individually ac etylated H4-lysine sites indicate that the enzymes recognize highly distinc t acetylation patterns. Only RPD3-type deacetylase HD1-B is able to deacety late the specific H4 di-acetylation pattern (position 12 and 5) introduced by the purified cytoplasmic histone acetyltransferase B after incubation wi th pure nonacetylated H4 subspecies. HD1-A and HD2 exist as phosphorylated forms. Dephosphorylation has dramatic, but opposite effects; whereas HD2 lo ses enzymatic activity upon dephosphorylation, HD1-A is activated with a ch ange of specificity against acetylated H4 subspecies. The data suggest that different types of deacetylases interact with different and highly specifi c acetylation patterns on nucleosomes.