Hepatitis C virus NS2/3 protease regulates HCV IRES-dependent translation and NS5B RdRp activity.

Chronic hepatitis C virus (HCV) infection often leads to liver cancer. NS2/3 protease is the first of two virally encoded proteases required for HCV polyprotein processing. In this report, we investigated the function of NS2/3 protease on HCV replication and translation. Cells transfected with plasmids encoding wild-type or mutant NS2/3 and a dual-luciferase reporter construct containing an HCV internal ribosome entry site (IRES) were used to examine the effect of NS2/3 protease on translation of HCV RNA. Cells transfected with plasmids encoding wild-type or mutant NS2/3, pcDNA-NS5B and a reporter plasmid were used to examine the effect of NS2/3 protease on HCV replication. The results showed that both autocleavage processing and the uncleaved form of NS2/3 protease specifically decrease HCV IRES-directed translation, while the uncleaved form of NS2/3 protease decreases HCV NS5B RdRp activity (replication), indicating that autoregulation by NS2/3 protease of HCV replication and translation may play an important role in persistent HCV infection.