Nonhistone chromatin protein phosphorylation during azo-dye carcinogenesis

Abstract

The nonhistone proteins of chromatin are believed to participate in the regulation of gene activity [l-3] . The phosphorylated chromatin proteins are of a particular interest since they display properties compatible with the functions of gene activator or repressor proteins [4,5] . Since the neoplastic disease most likely reflects altered biochemical control mechanisms and abnormal gene expression, knowledge of the effects of chemical carcinogens on the chromatin components in affected tissues may contribute to the eventual control of neoplasia. We report here that the activity of protein phosphokinase enzymes in the rat liver cytoplasm and chromatin increases after the administration of an azo-dye carcinogen, N,N-dimethyl-p(m-tolylazo) aniline (3’-MDAB). Furthermore, the phosphorylation of several nonhistone proteins increases in the liver chromatin of rats fed the azo-dye containing diet. At the same time, the ability of isolated liver chromatin to template for the in vitro RNA synthesis is considerably higher than that of the controls.