The effect of phenylhexyl isothiocyanate, trichostatin (TSA) and 5-aza-2-deoxycitidine (5-Aza) on histone H3 methylation in primary human leukemia cells. The methylation status of histone H3 lysine 4 (H3K4) and H3 lysine 9 (H3K9) was examined by Western blotting. Panel A shows a dose- and time-related reduction of methylation at histone H3K4 (top group) and H3K9 (lower group) in three patients (P20, P24, P27) after exposure for 3 and 7 hours, respectively, to PHI, TSA, and 5-Aza. The level of methylated H3K4 (panel B) and H3K9 (panel C) of eight patients was quantitated by densitometry. β-actin was used as a loading control (CK). The highest level was marked by the lines.