【Objective】 To investigate the relation between HBx protein expression and H3K4 methylation in hepatocellular carcinoma and its potential mechnism. 【Methods】 Cell line HepG2HBx that is able to stably express HBx and control cell line HepG2vc was constructed and cultured

as well as positive control HepG2.2.15 and negative control HepG2. Histone H3K4 methyltransferase activity was detected by using ultraviolet spectrophotometer

and we explored the effection of HBx on Histone H3K4 methyltransferase activity. Using qRTPCR and Westernblot to evaluate the change of expression level of SMYD3 ( SET and MYND domain containing3 ) in each cell groups. Detecting the expression level of SMYD3 and H3K4me3 with immunohistochemical staining (HbsAg+ 58 cases

HbsAg 26 cases) and finally statistically analyzing the results. 【Results】 Histone H3K4 methyltransferase activity and the expression level of SMYD3 in cell line that express HBx are stably significantly higher than that of negative control groups (P < 0.05). Moreover

the expression of SMYD3 is directly relevant to the HBV infection in HCC tissue sample

and promoting the methylation of histone H3K4. 【Conclusion】 HBx enhance the activity of histone H3K4 methyltransferase in hepatoma cells

and the potential mechanism may be related to HBxregulated expression of SMYD3

which also promote the methylation of histone H3K4 in HCC tissue.