title: Hepatitis B virus pre-S2 mutant large surface protein inhibits DNA double-strand break repair and leads to genome instability in hepatocarcinogenesis.
abstract: Although hepatitis B virus (HBV) has been established to cause hepatocellular carcinoma (HCC), the exact mechanism remains to be clarified. Type II ground glass hepatocytes (GGHs) harbouring the HBV pre-S2 mutant large surface protein (LHBS) have been recognized as a morphologically distinct hallmark of HCC in the advanced stages of chronic HBV infection. Considering its preneoplastic nature, we hypothesized that type II GGH may exhibit high genomic instability, which is important for the carcinogenic process in chronic HBV carriers. In this study we found that pre-S2 mutant LHBS directly interacted with importin α1, the key factor that recognizes cargos undergoing nuclear transportation mediated by the importin α/β-associated nuclear pore complex (NPC). By interacting with importin α1, which inhibits its function as an NPC factor, pre-S2 mutant LHBS blocked nuclear transport of an essential DNA repair and recombination factor, Nijmegen breakage syndrome 1 (NBS1), upon DNA damage, thereby delaying the formation of nuclear foci at the sites of DNA double-strand breaks (DSBs). Pre-S2 mutant LHBS was also found to block NBS1-mediated homologous recombination repair and induce multi-nucleation of cells. In addition, pre-S2 mutant LHBS transgenic mice showed genomic instability, indicated by increased global gene copy number variations (CNVs), which were significantly higher than those in hepatitis B virus X mice, indicating that pre-S2 mutant LHBS is the major viral oncoprotein inducing genomic instability in HBV-infected hepatocytes. Consistently, the human type II GGHs in HCC patients exhibited increased DNA DSBs representing significant genomic instability. In conclusion, type II GGHs harbouring HBV pre-S2 mutant oncoprotein represent a high-risk marker for the loss of genome integrity in chronic HBV carriers and explain the complex chromosome changes in HCCs. Mouse array CGH raw data: GEO Accession No. GSE61378 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE61378).
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Hsieh
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Yu-Ying
authors.initials: YY
authors.lastname: Chang
authors.affiliation: Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Tainan, Taiwan.
authors.forename: Ih-Jen
authors.initials: IJ
authors.lastname: Su
authors.affiliation: Department of Haematology and Oncology, National Cheng Kung University Hospital, Tainan, Taiwan.
authors.forename: Chia-Jui
authors.initials: CJ
authors.lastname: Yen
authors.affiliation: Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Yi-Ru
authors.initials: YR
authors.lastname: Liu
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Ren-Jei
authors.initials: RJ
authors.lastname: Liu
authors.affiliation: Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Tainan, Taiwan.
authors.forename: Wen-Chuan
authors.initials: WC
authors.lastname: Hsieh
authors.affiliation: Department of Pathology, National Cheng Kung University Hospital, Tainan, Taiwan.
authors.forename: Hung-Wen
authors.initials: HW
authors.lastname: Tsai
authors.affiliation: Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Lily Hui-Ching
authors.initials: LH
authors.lastname: Wang
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.|Institute of Basic Medicine, National Cheng Kung University, Tainan, Taiwan.|Centre of Infectious Disease and Signalling Research, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Wenya
authors.initials: W
authors.lastname: Huang
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000821:virology; D045744:Cell Line, Tumor; D002472:Cell Transformation, Viral / Q000235:genetics*; D055028:Comparative Genomic Hybridization; D053903:DNA Breaks, Double-Stranded; D056915:DNA Copy Number Variations; D004249:DNA Damage; D004260:DNA Repair; D005260:Female; D042822:Genomic Instability; D006514:Hepatitis B Surface Antigens / Q000235:genetics* / Q000378:metabolism; D006515:Hepatitis B virus / Q000235:genetics* / Q000378:metabolism; D019694:Hepatitis B, Chronic / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000821:virology; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000821:virology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D006514:Hepatitis B Surface Antigens; C096362:L protein, hepatitis B virus; D011498:Protein Precursors; D014759:Viral Envelope Proteins; C050807:presurface protein 2, hepatitis B surface antigen
keywords: DNA repair; copy number variation; double-strand break; genomic instability; hepatitis B virus; hepatocellular carcinoma; importin α1; pre-S2 mutant LHBS