Redox cycling of viral RNA polymerase controls picornavirus replication.

Picornaviruses, including foot-and-mouth disease virus (FMDV), enterovirus 71 (EV71) and encephalomyocarditis virus (EMCV), are important pathogens that cause fever, herpes, and myocarditis in humans and animals. The interplay between picornaviruses and their hosts remains enigmatic. Here we perform porcine genome-wide CRISPR/Cas9 screens and identify methionine sulfoxide reductase B3 (MSRB3) as an essential factor for FMDV. MSRB3 deficiency inhibits FMDV replication. Mechanistically, MSRB3 eliminates methionine oxidation of FMDV 3D polymerase and stabilizes its expression. Further studies show that radical SAM domain-containing protein 1 (RSAD1) catalyzes methionine oxidation of FMDV 3D polymerase and promotes its aggregation and subsequent degradation through the autophagy-lysosome pathway. Importantly, RSAD1-MSRB3-mediated redox modification also affects the stability of 3D polymerases of EV71 and EMCV, and regulates their infectivity and pathogenesis both in vitro and in vivo. Collectively, this study corroborates that RSAD1-MSRB3-mediated redox cycling of 3D polymerase plays a conserved function in modulating picornavirus infection, providing insights into viral pathogenesis and broad-spectrum antiviral development.