Ethanol increases ADP-ribosylation of histones in rat hepatocyte nuclei

Ethanol was shown previously to increase ADP-ribosylation of hepatocyte proteins. The purpose of this study was to determine the effect of ethanol on ADP-ribosylation of histones in hepatocyte nuclei. Freshly isolated hepatocytes were exposed to 100 mM ethanol for 2 h and ADP-ribosylated histones were separated from nonribosylated histones by phenylboronate agarose chromatography. Both histone factions were then separated into the individual histones by 12% acetic-urea-triton polyacrylamide gel electrophoresis. Ethanol did not change the amounts of outer histone H1 or amounts of core histones (H2A, H2B, H3.1, and H4) but increased the histone variants H3.2 and H3.3. The principal effect of ethanol was to increase the ADP-ribosylation of all the above histones. Exposure of hepatocytes in culture to 100 mM ethanol for 3 days did not increase the synthesis of histones as determined by the incorporation of 14C-L-lysine, but increased the ADP-ribosylation of histones, principally histone H2A, determined from the incorporation of 2, 8, 3H adenosine. These results show that ethanol increases the ADP-ribosylation of histones. This is a potential mechanism for effects of ethanol on the regulation of gene expression and cell differentiation.