Cousineau, S. E. | bioRxiv Science

bioRxiv2022

The cellular poly(rC)-binding protein 2 prevents the early steps of hepatitis C virus virion assembly

Poly(rC)-binding protein 2 (PCBP2) was previously shown to bind to the hepatitis C virus (HCV) genome; however, its precise role in the viral life cycle remained unclear. Herein, we found that PCBP2 does not directly affect viral entry, translation, genome stability, replication, or virion egress. Rather, our data suggests that endogenous PCBP2 normally limits virion assembly, thereby indirectly promoting translation and replication by increasing the translating/replicating pool of viral RNAs. Additionally, we found that an alternative RNA conformation (SLIIalt) was important for efficient virion assembly, but functions in a PCBP2-independent manner. The latter may explain why the Japanese fulminant hepatitis 1 isolate is able to produce infectious particles in cell culture, while other HCV isolates are lost in translation. Taken together, our results suggest that PCBP2 and SLIIalt independently modulate HCV genome packaging and alter the balance of viral RNAs in the translating/replicating pool and those engaged in virion assembly. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

molecular biology↗

bioRxiv2021

Poly(rC)-binding protein 1 limits hepatitis C virus assembly and egress

The hepatitis C virus (HCV) co-opts numerous cellular elements - including proteins, lipids, and microRNAs - to complete its viral life cycle. The cellular RNA-binding protein, poly(rC)-binding protein 1 (PCBP1), was previously reported to bind to the 5 untranslated region (UTR) of the HCV genome; however, its importance in the viral life cycle has remained unclear. Herein, we sought to clarify the role of PCBP1 in the HCV life cycle. Using the HCV cell culture (HCVcc) system, we found that knockdown of endogenous PCBP1 resulted in an overall decrease in viral RNA accumulation, yet resulted in an increase in extracellular viral titers. To dissect PCBP1s specific role in the HCV life cycle, we carried out assays for viral entry, translation, genome stability, RNA replication, as well as virion assembly and secretion. We found that PCBP1 knockdown did not directly affect viral entry, translation, RNA stability, or RNA replication, but resulted in an overall increase in infectious particle secretion. This increase in virion secretion was evident even when viral RNA synthesis was inhibited, and blocking virus secretion could partially restore the viral RNA accumulation decreased by PCBP1 knockdown. We therefore propose a model where endogenous PCBP1 normally limits virion assembly and secretion, which increases viral RNA accumulation in infected cells by preventing the departure of viral genomes packaged into virions. Overall, our findings improve our understanding of how cellular RNA-binding proteins influence viral genomic RNA utilization during the HCV life cycle.

microbiology↗