Hepatitis B virus X protein regulates the mEZH2 promoter via the E2Fl-binding site in AML12 cells

• Published in: 癌症 Vol. 30; no. 4; pp. 273 - 279
• Main Author: Xiao-Yan Shi Ying-Ying Zhang Xiao-Wei Zhou Jian-Sheng Lu Ze-Kun Guo Pei-Tang Huang
• Format: Journal Article
• Language: Chinese; English
• Published: Beijing Institute of Biotechnology, Beijing 100071,P. R. China 2011; College of Life Sciences, Northwest A&F University, Yangling,Shaanxi 712100, P. R. China%Beijing Institute of Biotechnology, Beijing 100071,P. R. China%College of Life Sciences, Northwest A&F University, Yangling,Shaanxi 712100, P. R. China
• Subjects: blot分析; 乙型肝炎病毒; 启动子; 组蛋白; 结合位点; 肝细胞癌; 质粒构建; 过度表达; enhancer of zeste homolog 2 of mouse; E2F1; hepatitis B virus X protein; promoter activity; Hepatitis B virus
• ISSN: 1000-467X; 1944-446X

Histone lysine methyltransferase EZH2 has been reported to be frequently overexpressed in hepatocellular carcinoma （HCC） tissues and associated with hepatocarcinogenesis. However, the exact mechanism of EZH2 up-regulation in HCC has not been determined. In this study, we used murine hepatocyte AML12 cells to investigate the role of hepatitis B virus X protein （HBx） in regulating the expression of mEZH2. Western blot analysis demonstrated that the expression level of mEZH2 protein in AML12 cells was up-regulated by HBx in a dose-dependent manner. To further investigate the mechanism of mEZH2 overexpression, the 2500 bp regulatory sequence upstream from the first exon of the mEZH2 gene was amplified from AML12 genomic DNA and constructed into a luciferase reporter plasmid. The luciferase activity of the mEZH2 promoter significantly increased in AML12 cells co-transfected with HBx plasmid, and deleting the -486/-214 promoter region decreased HBx-induced mEZH2 promoter activation by nearly 50%. The -486/-214 region was then analyzed in the TRANSFAC 6.0 database and a typical E2Fl-binding site was found. Mutation of this E2Fl-binding site or knockdown of E2F1 expression by RNAi led to a dramatic decrease in HBx-induced activation of the mEZH2 promoter and mEZH2 overexpression in AML12 cells. These results provide evidence that HBx up-regulates mEZH2 expression by transactivating the mEZH2 promoter through E2F1 transcription factor, thereby providing new epigenetic evidence for the carcinogenic effect of HBx.