Hepatitis C virus core protein down-regulates transcription of interferon-induced antiviral genes.
BACKGROUND
Hepatitis C virus (HCV) proteins interfere with the interferon (IFN)-alpha-induced Jak/signal transducer and activator of transcription (STAT) pathway. Which protein is responsible for this effect and whether this interference results in down-regulation of IFN-induced genes remain controversial. We analyzed the effect of HCV core (HCV-Co) protein on expression of IFN-induced antiviral genes.


METHODS
HepG2 cells were transfected with the plasmid pHCV-Co, and, after treatment with IFN-alpha , levels of MxA, protein kinase R (PKR), and 2'-5' oligoadenylate synthetase (2'-5'OAS) mRNA were determined. Chloramphenycol acethyl transferase (CAT) analysis was performed on cells cotransfected with pHCV-Co and pMx4CAT (containing the MxA gene promoter) and treated with IFN. Electrophoretic mobility shift assays were used, and Western-blot analysis of STAT 1 and 2 was performed.


RESULTS
Levels of MxA mRNA in pHCV-Co-transfected cells decreased in a dose-dependent manner, by down-regulation of the MxA gene promoter. HCV-Co protein inhibits binding of IFN-stimulated gene factor 3 (ISGF3) to the IFN-stimulated response element (ISRE). Intracellular distribution of STAT 1 and 2 was not modified after treatment with IFN. Expression of HCV-Co protein also results in down-regulation of expression of PKR and 2'-5'OAS genes.


CONCLUSIONS
HCV-Co protein inhibits IFN-alpha-induced transcription of antiviral genes by decreasing binding of ISGF3 to the ISRE.
de Lucas
Susana
S
Fundación para el Estudio de las Hepatitis Virales, Madrid 28015, Spain.
Bartolome
Javier
J
Carreno
Vicente
V
D015088:2',5'-Oligoadenylate Synthetase / Q000235:genetics; D015153:Blotting, Western; D045744:Cell Line, Tumor; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D019204:GTP-Binding Proteins / Q000235:genetics; D017930:Genes, Reporter; D016174:Hepacivirus / Q000472:pathogenicity*; D006801:Humans; D050832:Interferon-Stimulated Gene Factor 3; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha / Q000235:genetics / Q000276:immunology*; D064547:Myxovirus Resistance Proteins; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000032:analysis; D020218:Response Elements; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014758:Viral Core Proteins / Q000235:genetics / Q000502:physiology*; D019892:eIF-2 Kinase / Q000235:genetics
D004268:DNA-Binding Proteins; C494227:IRF9 protein, human; D050832:Interferon-Stimulated Gene Factor 3; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; D014758:Viral Core Proteins; D015500:Chloramphenicol O-Acetyltransferase; D019892:eIF-2 Kinase; D015088:2',5'-Oligoadenylate Synthetase; D019204:GTP-Binding Proteins