The oncogenic potential of hepatitis C virus NS5A sequence variants is associated with PKR regulation.
The NS5A protein of hepatitis C virus (HCV) confers cell growth regulation and has been implicated in viral oncogenesis. Here, we investigated whether highly divergent NS5A proteins obtained from HCV-infected patients presented an oncogenic potential when expressed in mammalian cells. In general, NS5A expression was associated with increased rates of cell growth and culture proliferation. Immortalized primary hepatocyte and immortalized fibroblast cell lines expressing a subset of these sequences exhibited a significant increase in protein synthetic rate, culture saturation density, and a transformed cellular phenotype, as shown by anchorage-independent cell growth and colony formation in soft agar assays. Oncogenic transformation correlated with inhibition of protein kinase R (PKR) activity and concomitant reduction of eukaryotic initiation factor 2alpha (elF2alpha) phosphorylation levels that caused stimulation of mRNA translation. The extent of sequence variation throughout NS5A or within the previously characterized PKR-binding domain was not a predictive indicator of this cellular phenotype, suggesting that sequences outside this region contribute to PKR regulation. Our data indicate that NS5A oncogenic potential is conditional through viral sequence variation. These results provide further evidence to define the PKR pathway as a mediator of cell growth control and suggest that viral regulation of PKR may contribute to hepatocyte growth deregulation during chronic HCV infection.
Giménez-Barcons
Mireia
M
Servei de Hepatologia, Institut de Malalties Digestives, Departament de Medicina, University of Barcelona and Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic, 08036 Barcelona, Spain.
Wang
Chunfu
C
Chen
Ming
M
Sánchez-Tapias
José-María
JM
Sáiz
Juan-Carlos
JC
Gale
Michael
M
D000595:Amino Acid Sequence; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000209:etiology; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D002472:Cell Transformation, Viral / Q000235:genetics / Q000502:physiology; D014644:Genetic Variation; D016174:Hepacivirus / Q000235:genetics* / Q000472:pathogenicity*; D006801:Humans; D008113:Liver Neoplasms / Q000209:etiology; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D017386:Sequence Homology, Amino Acid; D017361:Viral Nonstructural Proteins / Q000235:genetics* / Q000502:physiology; D019892:eIF-2 Kinase / Q000502:physiology*; D012324:RNA-Dependent RNA Polymerase
D017361:Viral Nonstructural Proteins; D019892:eIF-2 Kinase; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase