Hepatitis C virus core protein binds to a C-terminal region of NS5B RNA polymerase

Hepatitis C virus (HCV) NS5B has been shown to exhibit RNA-dependent RNA polymerase activity for its viral RNA replication. In this study, we demonstrated the formation of a complex between NS5B and the core protein (NS5B-core protein complex) in mammalian cells, as determined by indirect immunofluorescence and immunoprecipitation analyses. The localization of the core protein was observed to change to the same locus in ER as NS5B locates by its coexpression with NS5B, indicating that the localization of the core protein is determined by NS5B. The truncated NS5B molecule lacking the C-terminal region did not form a complex with the core protein, suggesting that the C-terminal region of NS5B is essential for its interaction with the core protein. Moreover, the change in NS5B localization because of C-terminal deletion indicates that this region includes a certain signal for NS5B retention in ER.