Abstract: BACKGROUND ＆ AIM: To investigate the regulation of histone H3 acetylation and the expression of p21WAF1/CIP1 by NS_398 in HepG2 cells. MATERIALS AND METHODS: The effect of NS_398 on the proliferation of HepG2 cells was evaluated by MTT. The apoptotic cells were determined by flow cytometric(FCM)analysis.Total proteins and mRNA were extracted from HepG2 cells treated with or without NS_398 with IC50 200 μmol/L at various time points (4,8,12,24,48 h).By using Western blot, the levels of acetylated histone H3 and p21WAF1/CIP1 protein expression were assayed. RT_PCR was used to detect the expression level of p21WAF1/CIP1 mRNA. RESULTS: NS_398 inhibited cell proliferation and induced apoptosis in HepG2 in a concentration_dependent manner. DNA ploidy analysis showed that S phase cells were significantly decreased with increasing NS_398 concentration.Histone H3 acetylation was obviously increased by NS_398 in a time_dependent manner. The expression levels of p21WAF1/CIP1 mRNA and protein were up_regulated in a time_and dose_dependent manner. CONCLUSION: The level of acetylated histone H3 was up_regulated by NS_398, and the expression of p21WAF1/CIP1 was increased at the same time.

Key words: NS_398, histone acetylation, p21WAF1/ CIP1, HepG2 cell