Histone acetylation in Zea mays.I. Activities of histone acetyltransferases and histone deacetylases

DEAE-Sepharose chromatography of extracts from Zea mays meristematic cells revealed multiple histone acetyltransferase and histone deacetylase enzyme forms. An improved method for nuclear isolation allowed us to discriminate nuclear and cytoplasmic enzymes. Two nuclear histone acetyltransferases, A1 and A2, a cytoplasmic B-enzyme and two nuclear histone deacetylases, HD1 and HD2, have been identified. The histone specificity of the different enzyme forms has been studied in an in vitro system, using chicken erythrocyte histones as substrate. The cytoplasmic histone acetyltransferase B is the predominant enzyme, which acetylates mainly histone H4 and to a lesser extent H2A. The nuclear histone acetyltransferase A1 preferentially acetylates H3 and also H4, whereas enzyme A2 is specific for H3. This substrate specificity was confirmed with homologous Z. mays histones. The two histone deacetylases differ from each other with respect to ionic strength dependence, inhibition by acetate and butyrate, and substrate specificity. The strong inhibitory effect of acetate on histone deacetylases was exploited to distinguish different histone acetyltransferase forms.