Involvement of Hepatitis C Virus NS5A Hyperphosphorylation Mediated by Casein Kinase I-α in Infectious Virus Production

Abstract

Mechanisms regulating NS5A phosphorylation and its exact function in the HCV life cycle have not been clearly defined. By using a high-throughput screening system targeting host protein kinases, we identified CKI-α as an NS5A-associated kinase involved in NS5A hyperphosphorylation and the production of infectious virus. Our results suggest that the impact of CKI-α in the HCV life cycle is more profound on virion assembly than viral replication via mediation of NS5A hyperphosphorylation. CKI-α-dependent hyperphosphorylation of NS5A plays a role in recruiting NS5A to low-density membrane structures around LDs and facilitating its interaction with the core for new virus particle formation. By using proteomic approach, we identified the region within the low-complexity sequence I of NS5A that is involved in NS5A hyperphosphorylation and hyperphosphorylation-dependent regulation of infectious virus production. These findings will provide novel mechanistic insights into the roles of NS5A-associated kinases and NS5A phosphorylation in the HCV life cycle.