Epigenetic silencing of NAD(P)H:quinone oxidoreductase 1 by hepatitis B virus X protein increases mitochondrial injury and cellular susceptibility to oxidative stress in hepatoma cells.
NAD(P)H:quinone oxidoreductase 1 (NQO1) is a phase II enzyme that participates in the detoxification of dopamine-derived quinone molecules and reactive oxygen species. Our prior work using a proteomic approach found that NQO1 protein levels were significantly decreased in stable hepatitis B virus (HBV)-producing hepatoma cells relative to the empty-vector-transfected controls. However, the mechanism and biological significance of the NQO1 suppression remain elusive. In this study we demonstrate that HBV X protein (HBx) induces epigenetic silencing of NQO1 in hepatoma cells through promoter hypermethylation via recruitment of DNA methyltransferase DNMT3A to the promoter region of the NQO1 gene. In HBV-related hepatocellular carcinoma (HCC) specimens, HBx expression was correlated negatively to NQO1 transcripts but positively to NQO1 promoter hypermethylation. Downregulation of NQO1 by HBx reduced intracellular glutathione levels, impaired mitochondrial function, and increased susceptibility of hepatoma cells to oxidative stress-induced cell injury. These results suggest a novel mechanism for HBV-mediated pathogenesis of chronic liver diseases, including HCC.
Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350108, China.
Yun-Li
YL
Wu
Department of Hepatobiliary and Pancreatic Surgery, Union Clinical Medical College, Fujian Medical University, Fuzhou 350108, China.
Dong
D
Wang
Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350108, China.
Xian-E
XE
Peng
Department of Hepatobiliary and Pancreatic Surgery, Union Clinical Medical College, Fujian Medical University, Fuzhou 350108, China.
Yan-Ling
YL
Chen
Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350108, China.
Da-Li
DL
Zheng
Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350108, China; Key Laboratory of Tumor Microbiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350108, China.
Wan-Nan
WN
Chen
Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350108, China; Key Laboratory of Tumor Microbiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou 350108, China. Electronic address: linxu@mail.fjmu.edu.cn.
Xu
X
Lin
D006528:Carcinoma, Hepatocellular / Q000821:virology*; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D020868:Gene Silencing; D006509:Hepatitis B / Q000235:genetics; D006801:Humans; D008113:Liver Neoplasms / Q000821:virology*; D008928:Mitochondria / Q000473:pathology; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics*; D018384:Oxidative Stress / Q000235:genetics; D016133:Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human
Epigenetic modification; Free radicals; Hepatitis B virus X protein; Hepatocellular carcinoma; Mitochondrial injury; NAD(P)H:quinone oxidoreductase 1; Redox status