PLK1-ELAVL1/HuR-miR-122 signaling facilitates hepatitis C virus proliferation.

The liver-specific microRNA, miR-122, plays an essential role in the propagation of hepatitis C virus (HCV) by binding directly to the 5'-end of its genomic RNA. Despite its significance for HCV proliferation, the host factors responsible for regulating miR-122 remain largely unknown. In this study, we identified the cellular RNA-binding protein, ELAVL1/HuR (embryonic lethal-abnormal vision-like 1/human antigen R), as critically contributing to miR-122 biogenesis by strong binding to the 3'-end of miR-122. The availability of ELAVL1/HuR was highly correlated with HCV proliferation in replicon, infectious, and chronically infected patient conditions. Furthermore, by screening a kinase inhibitor library, we identified rigosertib, an anticancer agent under clinical trials, as having both miR-122-modulating and anti-HCV activities that were mediated by its ability to target polo-like kinase 1 (PLK1) and subsequently modulate ELAVL1/HuR-miR-122 signaling. The expression of PLK1 was also highly correlated with HCV proliferation and the HCV positivity of HCC patients. ELAVL1/HuR-miR-122 signaling and its mediation of PLK1-dependent HCV proliferation were demonstrated by performing various rescue experiments and utilizing an HCV mutant with low dependency on miR-122. In addition, the HCV-inhibitory effectiveness of rigosertib was validated in various HCV-relevant conditions, including replicons, infected cells, and replicon-harboring mice. Rigosertib was highly effective in inhibiting the proliferation of not only wild-type HCVs, but also sofosbuvir resistance-associated substitution-bearing HCVs. Our study identifies PLK1-ELAVL1/HuR-miR-122 signaling as a regulatory axis that is critical for HCV proliferation, and suggests that a therapeutic approach targeting this host cell signaling pathway could be useful for treating HCV and HCV-associated diseases.