A Host YB-1 Ribonucleoprotein Complex Is Hijacked by Hepatitis C Virus for the Control of NS3-Dependent Particle Production

Abstract

dHepatitis C virus (HCV) orchestrates the different stages of its life cycle in time and space through the sequential participation of HCV proteins and cellular machineries; hence, these represent tractable molecular host targets for HCV elimination by combination therapies. We recently identified multifunctional Y-box-binding protein 1 (YB-1 or YBX1) as an interacting partner of NS3/4A protein and HCV genomic RNA that negatively regulates the equilibrium between viral translation/replication and particle production. To identify novel host factors that regulate the production of infectious particles, we elucidated the YB-1 interactome in human hepatoma cells by a quantitative mass spectrometry approach. We identified 71 YB-1-associated proteins that included previously reported HCV regulators DDX3, heterogeneous nuclear RNP A1, and ILF2. Of the potential YB-1 interactors, 26 proteins significantly modulated HCV replication in a gene-silencing screening. Following extensive interaction and functional validation, we identified three YB-1 partners, C1QBP, LARP-1, and IGF2BP2, that redistribute to the surface of corecontaining lipid droplets in HCV JFH-1-expressing cells, similarly to YB-1 and DDX6. Importantly, knockdown of these proteins stimulated the release and/or egress of HCV particles without affecting virus assembly, suggesting a functional YB-1 protein complex that negatively regulates virus production. Furthermore, a JFH-1 strain with the NS3 Q221L mutation, which promotes virus production, was less sensitive to this negative regulation, suggesting that this HCV-specific YB-1 protein complex modulates an NS3-dependent step in virus production. Overall, our data support a model in which HCV hijacks host cell machinery containing numerous RNA-binding proteins to control the equilibrium between viral RNA replication and NS3-dependent late steps in particle production.

Y-Box Binding Protein 1 Stabilizes Hepatitis C Virus NS5A via Phosphorylation-Mediated Interaction with NS5A To Regulate Viral Propagation

“…2F). The results substantiate that YB-1 is essential for the HCV life cycle, as reported by Chatel-Chaix et al (43,44).…”

“…7E) conceivably suggests that YB-1 is important for the production of infectious HCV particles. Interestingly, by using a plasmid-derived JFH-1-expressing system, Chatel-Chaix et al showed that knockdown of YB-1 promoted infectious virus production (43,44). Notably, the kinetics of the plasmid-derived JFH-1 expression is much slower than that of cell culture-derived HCV (HCVcc) infection adopted in our study (22,43).…”

“…Among the HCV proteins, core protein, NS3, and NS5A have notably been shown to have a larger number of cellular interacting partners (51). In view of the fact that both core/YB-1 and NS3/YB-1 interactions have been extensively studied (43,44), we turned our attention to examining the interaction between NS5A and YB-1. To this end, coimmunoprecipitation was performed with Huh-7.5.1 cell extracts coexpressing HA-YB-1 and Flag-tagged NS5A (JFH1) of genotype 2a in the presence of RNase A. Interaction between NS5A and YB-1 was observed, as were the known NS3-YB-1 and core-YB-1 interactions (Fig.…”

“…Coincident with its RNA binding activity, YB-1 has been identified as a HCV 3= NTR-binding protein (42) and interacts with HCV RNA during infection (43). Recent studies suggested that YB-1 interacts and colocalizes with NS3/4A, core, and several HCV cellular cofactors, including DDX3 (43,44). YB-1 also supports HCV RNA replication while transiently suppressing virion release in an early stage of a plasmid-driven infection system (43,44).…”

“…Recent studies suggested that YB-1 interacts and colocalizes with NS3/4A, core, and several HCV cellular cofactors, including DDX3 (43,44). YB-1 also supports HCV RNA replication while transiently suppressing virion release in an early stage of a plasmid-driven infection system (43,44).…”