title: Hepatitis B virus X protein disrupts DNA interstrand crosslinking agent mitomycin C induced ATR dependent intra-S-phase checkpoint.
abstract: Chronic infection of hepatitis B virus (HBV) is one of the major causes of hepatocellular carcinoma (HCC) in the world. The hepatitis B virus X protein (HBx) is implicated in HCC development, although its oncogenic role remains controversial. HBx is a multifunctional regulator that modulates transcription, signal transduction, cell cycle progress, and DNA repair by directly or indirectly interacting with host factors. We constructed the HBx stably expressing HepG2 cell line to investigate the impact of HBx on intra-S-phase checkpoint induced by mitomycin C (MMC). The HBx transformed HepG2 cells are more sensitive to MMC treatment and showed defective radioresistant DNA synthesis compared to the control cell line transformed with empty vector. With DNA content assay, HBx transformed cells showed defective S phase arrest and a consequent G2/M arrest after MMC treatment. HBx impaired the ATR dependent phosphorylation of Chk1 and monoubiquitination of FANCD2. Overexpression of ATR reverted the MMC induced phenotype of Chk1 and FANCD2 in HBx transformed cells. The defect of intra-S-phase checkpoint resulted in accumulation of genomic instability. In conclusion, HBx disrupts intra-S-phase checkpoint induced by MMC through ATR-Chk1 and ATR-FANCD2 pathways.
authors.affiliation: Department of Pathology, Sir Run Run Shaw Hospital, Affiliated with School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Xiao-Ye
authors.initials: XY
authors.lastname: Wu
authors.forename: Jia-Jie
authors.initials: JJ
authors.lastname: Qian
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
authors.forename: Ming-Hua
authors.initials: MH
authors.lastname: Zheng
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000821:virology; D000071877:Checkpoint Kinase 1; D004249:DNA Damage / Q000187:drug effects*; D019694:Hepatitis B, Chronic / Q000150:complications; D006801:Humans; D008113:Liver Neoplasms / Q000821:virology; D016685:Mitomycin / Q000494:pharmacology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism; D016196:S Phase / Q000187:drug effects*; D015534:Trans-Activators / Q000494:pharmacology*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D016685:Mitomycin; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1