OBJECTIVETo investigate the biological function of the hepatitis C virus (HCV)-encoded F protein in hepatocytes.

METHODSThe full-length F gene was amplified by PCR from HCV genotype 1a and cloned into plasmid pSEB-3Flag by restriction enzyme digestion and ligation. Hepatoma cell lines, Huh7 and SMMC7721, were transfected with the resultant recombinant pSEB-3Flag-F or the original pSEB-3Flag (negative control) and screened with the selective antibiotic, blasticidin. Stable F gene and protein expression was verified by RT-PCR analysis. Analysis of cell growth and cell cycle was carried out by MTS assay, crystal violet staining and flow cytometry.

RESULTSHuh7 and SMMC7721 cells transfected with pSEB-3Flag-F plasmid (Huh7-F and SMMC7721-F, respectively) uniquely expressed the F gene and protein. The Huh7-F and SMMC7721-F cells showed significantly decreased proliferation rates, compared to the respective control groups. A similar HCV F-mediated growth-inhibiting activity was observed by the cell viability assay. Furthermore, cell cycle analysis revealed that the S-phase distribution was much lower in Huh7-F (47.12%) and SMMC7721-F (30.75%) cells than in the respective controls (55.35% and 33.23%, respectively) (P less than 0.05).

CONCLUSIONStable expression of the HCV F gene reduced the in vitro proliferation rate of hepatoma cell lines, indicating that the F protein may function as a growth inhibitor of infected cells.