title: Hepatitis C virus core protein expression leads to biphasic regulation of the p21 cdk inhibitor and modulation of hepatocyte cell cycle.
abstract: Hepatitis C virus (HCV) Core protein is implicated in viral pathogenesis by the modulation of hepatocyte gene expression and function. To determine the effect of Core protein on the cell-cycle control of hepatocytes, a HepG2 cell line containing a Flag-tagged Core under the control of an inducible promoter was generated. Initial Core protein expression included the presence of unprocessed (191 aa) and processed (173 aa) forms of the Core proteins with the processed form becoming dominant later. Expression of the 191 aa form of Core protein corresponded to an increase in the expression of the p21, a decrease in cdk2-dependent kinase activity, and a decrease in the percentage of cells in S-phase along with an accumulation of cells in the G(0)/G(1) phase of the cell cycle. As the processed form accumulated, the p21 levels started to decline, suggesting that Core protein regulates p21 expression in a biphasic manner. These findings implicate Core protein in potentially modulating hepatocyte cell cycle differentially in the early stages of infection through biphasic regulation of p21 cdk kinase inhibitor.
authors.affiliation: Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis, CA 95616, USA.
authors.forename: Hau
authors.initials: H
authors.lastname: Nguyen
authors.forename: Maria
authors.initials: M
authors.lastname: Mudryj
authors.forename: Moraima
authors.initials: M
authors.lastname: Guadalupe
authors.forename: Satya
authors.initials: S
authors.lastname: Dandekar
mesh_terms: D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D016174:Hepacivirus / Q000235:genetics; D022781:Hepatocytes / Q000166:cytology* / Q000821:virology*; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016196:S Phase; D014407:Tumor Cells, Cultured; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D014758:Viral Core Proteins; C069130:nucleocapsid protein, Hepatitis C virus; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases