The steady state of histone acetylation is established and maintained by multiple histone acetyltransferases and deacetylases, and this steady state affects chromatin structure and function. The identification of a maize complementary DNA encoding the chromatin-bound deacetylase HD2 is reported. This protein was not homologous to the yeast RPD3 transcriptional regulator. It was expressed throughout embryo germination in correlation with the proliferative activity of cells. Antibodies against recombinant HD2-p39 immunoprecipitated the native enzyme complex, which was composed of phosphorylated p39 subunits. Immunofluorescence microscopy and sequence homologies suggested nucleolar localization. HD2 is an acidic nucleolar phosphoprotein that might regulate ribosomal chromatin structure and function.