OBJECTIVETo study the effect of HCV NS5A on the Janus kinase (JAK)/signal transducer and activation of transcription (STAT1) phosphorylation and translocation induced by IFN alpha-2b and to understand the possible molecular mechanism of HCV interferon resistance.

METHODSHepatocellular carcinoma cell line Huh7 was transiently transfected with HCV NS5A protein expression plasmid pCNS5A and blank plasmid pRC/CMV respectively; the cells of the same cell line, without transfection, served as controls. Immunocytochemistry was used to prove the successful transfection. Immunofluorescence and Western blot were performed to observe the difference in STAT1 phosphorylation and nuclear translocation between HCV NS5A-expressed and non-HCV NS5A-expressed cells after 30 minutes of IFN alpha-2b induction.

RESULTSHCV NS5A protein was detected in the cytoplasm of Huh7 cells transfected with pCNS5A, indicating the successful transfection. In comparison to the blank plasmid-transfected and non-transfected group, STAT1 phosphorylation and sequential nuclear import were reduced in the presence of HCV NS5A protein.

CONCLUSIONHCV NS5A can, to some extent, inhibit phosphorylation and nuclear translocation of STAT1 in IFN alpha-2b-induced JAK/STAT pathway, which may be a possible mechanism of HCV interferon resistance.