ABSTRACT
The hepatitis C virus (HCV) co-opts a number of cellular elements – including proteins, lipids, and microRNAs – to complete its viral life cycle. The cellular RNA-binding protein poly(rC)-binding protein 1 (PCBP1) had previously been reported to bind the HCV genome 5’ untranslated region (UTR), but its importance in the viral life cycle has remained unclear. Herein, we aimed to clarify the role of PCBP1 in the HCV life cycle. Using the HCV cell culture (HCVcc) system, we found that endogenous PCBP1 knockdown decreased viral RNA accumulation yet increased extracellular virus titers. To dissect PCBP1’s specific role in the viral life cycle, we carried out assays for viral entry, translation, genome stability, RNA replication, virion assembly and egress. We found that PCBP1 did not affect viral entry, translation, RNA stability, or RNA replication in the absence of efficient virion assembly. To specifically examine virion assembly and egress, we inhibited viral RNA replication with an RNA-dependent RNA polymerase inhibitor and tracked both intracellular and extracellular viral titers over time. We found that when viral RNA accumulation was inhibited, knockdown of PCBP1 still resulted in an overall increase in HCV particle secretion. We therefore propose a model where endogenous PCBP1 limits virion assembly and egress, thereby indirectly enhancing viral RNA accumulation in infected cells. This model furthers our understanding of how cellular RNA-binding proteins modulate HCV genomic RNA utilization during the viral life cycle.
IMPORTANCE Hepatitis C virus (HCV) is a positive-sense RNA virus, and as such, its genome must be a template for multiple mutually exclusive steps of the viral life cycle, namely translation, RNA replication, and virion assembly. However, the mechanism(s) that regulate how the viral genome is used throughout the viral life cycle still remain unclear. A cellular RNA-binding protein – PCBP1 – had previously been reported to bind the HCV genome, but its precise role in the viral life cycle was not known. In this study, we found that depleting PCBP1 decreased viral RNA accumulation but increased virus secretion. We ruled out a role for PCBP1 in virus entry, translation, genome stability or RNA replication, and demonstrate that PCBP1 knockdown enhances virus secretion when RNA replication is inhibited. We conclude that PCBP1 normally prevents virus assembly and egress, which allows more of the viral genomic RNA to be available for translation and viral RNA replication.
Competing Interest Statement
The authors have declared no competing interest.
