Epigenetic silencing of interferon-inducible genes is implicated in interferon resistance of hepatitis C virus replicon-harboring cells.
OBJECTIVE
We previously established hepatitis C virus (HCV) replicon-harboring cell lines possessing two interferon (IFN)-resistant phenotypes: a partially resistant phenotype (alphaR series) and a severely resistant phenotype (betaR series). We recently found that the severe IFN resistance of the betaR-series cells is caused by the functional disruption of type I IFN receptors. Here, we aimed to clarify the mechanism(s) underlying the partial IFN resistance of the alphaR-series cells.


METHODS
alphaR-series cells were pre-treated with 5-azacytidine to evaluate the effects of DNA demethylation on IFN resistance. cDNA microarray analysis was carried out in order to compare 1alphaR cells, which belong to the alphaR series, treated with both 5-azacytidine and IFN-alpha with cells treated with 5-azacytidine or IFN-alpha alone.


RESULTS
We found that the IFN-resistant phenotype of alphaR-series cells was impaired by treatment with 5-azacytidine. cDNA microarray analysis identified seven IFN-stimulated genes, which were up-regulated by 5-azacytidine treatment. We demonstrated here that the ectopic expression of each of these seven genes in 1alphaR cells frequently weakened the IFN resistance of these cells.


CONCLUSIONS
The present results suggest that the epigenetic silencing of IFN-stimulated genes is implicated in the acquisition of a partially IFN-resistant phenotype of HCV replicon-harboring cells.
Department of Molecular Biology, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.
Kazuhito
K
Naka
Ken-ichi
K
Abe
Kazunori
K
Takemoto
Hiromichi
H
Dansako
Masanori
M
Ikeda
Kunitada
K
Shimotohno
Nobuyuki
N
Kato
D000998:Antiviral Agents / Q000494:pharmacology*; D001374:Azacitidine / Q000494:pharmacology; D002478:Cells, Cultured; D019175:DNA Methylation; D024882:Drug Resistance, Viral; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000187:drug effects; D015967:Gene Expression Regulation, Viral / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects*; D016174:Hepacivirus / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D006526:Hepatitis C / Q000188:drug therapy* / Q000276:immunology; D006801:Humans; D007372:Interferons / Q000494:pharmacology*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D012093:Replicon / Q000235:genetics; D015854:Up-Regulation
D000998:Antiviral Agents; D004791:Enzyme Inhibitors; D007372:Interferons; D001374:Azacitidine