Acetylation of histone H3 at lysine 9 by ethanol in rat hepatocytes

Histone acetylation plays an important role in transcriptional activation. We have investigated the effect of ethanol on nuclear histone H3 acetylation in rat hepatocytes. Hepatocytes were incubated with ethanol (5-200 mM) for 24h and then acetylation states of nuclear histone H3 at specific lysine residues (Lys(9) and Lys(14)) were measured by immunoblot analysis using site-specific antibodies. Ethanol increased acetylation of histone H3 at Lys(9) in a dose-dependent manner; 3-fold at 5mM and maximum of 8-fold at 100mM. Sensitivity to low dose of ethanol was remarkable. This ethanol-induced acetylation was also time-dependent, showing a maximal response at 24h. Ethanol did not alter the level of histone H3 expression. Trichostatin A, a histone deacetylase inhibitor, was used as a positive control and it also increased acetylation. However, acetylation at Lys(14) was not affected by ethanol. Treatment of cells with ethanol metabolizing enzyme inhibitors (4-methylpyrazole and cyanamide) decreased ethanol-induced histone H3 acetylation at Lys(9). This is the first report of ethanol-induced selective, post-translational acetylation of histone H3 at Lys(9). This is not due to increased histone expression or a direct physical effect of ethanol but is dependent on ethanol metabolism.