Intracellular hepatitis C virus RNA-dependent RNA polymerase activity.

Hepatitis C virus (HCV) infection represents a significant health concern in over 170 million individuals worldwide. Recently, Huh7 cell-based hepatitis C virus replicon systems, which rely upon the expression and cooperation of viral nonstructural proteins to mediate replication of the entire hepatitis C virus genome, were shown to be useful for studying viral replication and antiviral agents. We report that expression of the viral RNA-dependent RNA polymerase (RdRp) in yeast cells, independent of other viral proteins, is necessary and sufficient for initiation of RNA synthesis in cis from 3'-nontranslated hepatitis C virus RNA. Furthermore, expression of the polymerase alone appears incapable of transcribing across the entire viral genome, most likely due to the secondary structure of the RNA. Other viral polypeptides, such as helicase, which are presumed to be present in the functional replicase complex, are predicted to facilitate RNA synthesis across highly structured regions.