title: Hepatitis B Virus X Protein Stabilizes Cyclin D1 and Increases Cyclin D1 Nuclear Accumulation through ERK-Mediated Inactivation of GSK-3β.
abstract: The Hepatitis B virus X protein (HBx) contributes centrally to the pathogenesis of hepatocellular carcinoma (HCC). It has been suggested that the transcriptional activation of cyclin D1 by HBx is implicated in the development of HCC. However, numerous studies have shown that overexpression of cyclin D1 alone is not sufficient to drive oncogenic transformation. Herein, we investigated whether HBx can stabilize cyclin D1 and induce cyclin D1 protein nuclear accumulation, and thereby accelerate hepatocarcinogenesis. The effects of HBx on cyclin D1 stabilization were assessed in cell-based transfection, Western blot, immunoprecipitation, immunocytofluorescence staining, and flow-cytometric assays. The results demonstrated that ectopic expression of HBx in HCC cells could extend the half-life of cyclin D1 protein from 40-60 minutes to 80-110 minutes. HBx stabilized cyclin D1 primarily in the S phase of the cell cycle, in a manner dependent on the inactivation of GSK-3β, which was mediated by ERK activation. HBx also prompted the nuclear accumulation of cyclin D1, and cotransfection of the constitutively active mutant of GSK-3β along with HBx could reverse the nuclear accumulation and subsequent cell proliferation induced by HBx. Further, a positive correlation between HBx and nuclear cyclin D1 level was established in HCC specimens detected by an immunohistochemical assay. Taken together, our results indicated that HBx could stabilize and increase cyclin D1 nuclear accumulation through ERK-mediated inactivation of GSK-3β. This HBx-induced cyclin D1 upregulation might play an important role in HCC development and progression.
authors.affiliation: Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China.
authors.forename: Xiangmei
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Hepatobiliary Surgery, Henan Cancer Hospital, Zhengzhou, P.R. China.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Beijing YouAn hospital, Capital Medical University, Beijing, P.R. China.
authors.forename: Sujun
authors.initials: S
authors.lastname: Zheng
authors.affiliation: Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China.
authors.forename: Meng
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China.
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China.
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Zeng
authors.affiliation: The Pirbright Institute, Pirbright, Woking, United Kingdom.
authors.forename: Malcolm A
authors.initials: MA
authors.lastname: McCrae
authors.affiliation: Department of Pathology, Institute of Infectious Diseases, Beijing 302 Hospital, Beijing, P.R. China.
authors.forename: Jingmin
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhuang
authors.affiliation: Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China. lu.fengmin@hsc.pku.edu.cn.
authors.forename: Fengmin
authors.initials: F
authors.lastname: Lu
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology / Q000821:virology; D002467:Cell Nucleus / Q000378:metabolism*; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism*; D018450:Disease Progression; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology / Q000821:virology; D051379:Mice; D041681:NIH 3T3 Cells; D055550:Protein Stability; D021381:Protein Transport; D015534:Trans-Activators / Q000502:physiology*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: C530104:CCND1 protein, human; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D019938:Cyclin D1; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3