title: Hepatitis B virus X protein activates the ATM-Chk2 pathway and delays cell cycle progression.
abstract: Genetic instability is intimately associated with tumour development. In particular, liver cancers associated with hepatitis B virus (HBV) exhibit high genetic instability; however, our understanding of the underlying molecular mechanisms remains limited. In this study, we found that γ-H2AX, a marker of DNA double-strand breaks (DSBs), and the levels of phospho-Chk2 (p-Chk2, the activated form) were significantly elevated in HBV-associated hepatocellular carcinomas and neighbouring regenerating nodules. Likewise, introduction of the pHBV or pMyc-HBx plasmids into cells induced accumulation of γ-H2AX foci and increased the p-Chk2 level. In these cells, inhibitory phosphorylation of Cdc25C phosphatase (Ser(216)) and CDK1 (Tyr(15)) was elevated; consequently, cell-cycle progression was delayed at G2/M phase, suggesting that activation of the ATM-Chk2 pathway by the HBV X protein (HBx) induces cell-cycle delay. Accordingly, inhibition of ataxia telangiectasia mutated (ATM) by caffeine or siRNA abolished the increase in the p-Chk2 level and restored the delayed CDK1 kinase activity in ChangX cells. We also found that cytoplasmic HBx, but not nuclear HBx, induced reactive oxygen species (ROS) production and led to the accumulation of γ-H2AX foci and the increased p-Chk2 level. Together, these data indicate that HBx-induced ROS accumulation induces DNA damage that activates the ATM-Chk2 pathway. Our findings provide insight into the mechanisms of HBV pathogenesis.
authors: Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Republic of Korea.
authors: Sujeong
authors: S
authors: Kim
authors: Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Republic of Korea.|Department of Biomedical Sciences, The Graduate School of Ajou University, Suwon, Republic of Korea.
authors: Ho-Soo
authors: HS
authors: Lee
authors: Genomic Instability Research Center, Ajou University School of Medicine, Suwon, Republic of Korea.
authors: Jae-Hoon
authors: JH
authors: Ji
authors: Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Republic of Korea.|Department of Biomedical Sciences, The Graduate School of Ajou University, Suwon, Republic of Korea.
authors: Mi-Young
authors: MY
authors: Cho
authors: Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Republic of Korea.|Department of Biomedical Sciences, The Graduate School of Ajou University, Suwon, Republic of Korea.
authors: Young-Suk
authors: YS
authors: Yoo
authors: Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Republic of Korea.
authors: Yong-Yea
authors: YY
authors: Park
authors: Department of Life Sciences, Sogang University, Seoul, Republic of Korea.
authors: Hyuk-Jin
authors: HJ
authors: Cha
authors: Genomic Instability Research Center, Ajou University School of Medicine, Suwon, Republic of Korea.
authors: Youngsoo
authors: Y
authors: Lee
authors: Department of Pathology, Ajou University School of Medicine, Suwon, Republic of Korea.
authors: Youngbae
authors: Y
authors: Kim
authors: Department of Biomedical Sciences, The Graduate School of Ajou University, Suwon, Republic of Korea.|Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Republic of Korea.|Genomic Instability Research Center, Ajou University School of Medicine, Suwon, Republic of Korea.
authors: Hyeseong
authors: H
authors: Cho
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D064447:Checkpoint Kinase 2 / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D005260:Female; D006509:Hepatitis B / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology / Q000821:virology; D006515:Hepatitis B virus / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D017382:Reactive Oxygen Species / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D006657:Histones; D017382:Reactive Oxygen Species; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D064447:Checkpoint Kinase 2; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human