N-acetylation of arginine-rich hepatoma histones.

Previous work in this laboratory has shown that decay rates of histones and DNA isolated from deoxyribonucleoprotein of normal and neoplastic rat tissues were approximately equal, indicating that not only DNA but the nucleohistone complex as a whole is metabolically inert. In contrast, the N -acetyl groups in the combined arginine and slightly lysine-rich histones from these same tissues were found to turn over at much faster rates than whole histones or DNA, with exception of the Novikoff hepatoma, in which this turnover was remarkably slow, approaching that of the histones. Studies were therefore carried out on a number of hepatomas with varying growth rates, which indicated that the half-lives of their histone N -acetyl groups were in general an order of magnitude smaller than that of the whole histones and similar to that of most tissues studied thus far. The data derived from very-slow-growing tumors would seem to indicate that the histone N -acetyl groups from hepatocyte histones exhibit a rapid turnover similar to that in other tissues.