Host protein synthesis shutdown and evasion of the innate immune response by SARS-CoV-2 NSP14 3153

Abstract Description Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of COVID-19. Subversion of host protein synthesis is a common strategy that pathogenic viruses use to replicate and propagate in their host. This not only facilitates the hijacking of the host translation machinery for viral protein synthesis but also attenuates the synthesis of antiviral proteins. In this study, we show that SARS-CoV-2 shuts down host protein synthesis, primarily through the activity of its nonstructural protein NSP14. The crucial role of NSP14 in viral replication is attributed to its exoribonuclease (ExoN) and guanine N7-methyltransferase (N7-MTase) activities. Mutations in the active sites of either the ExoN or N7-MTase domains of NSP14 abolish its translation inhibition activity. Additionally, using site-specific mutagenesis and co-immunoprecipitation, we demonstrate that the formation of the NSP14-NSP10 complex enhances the translation inhibition activity. Using a recombinant NSP14-NSP10 complex, we further show that it catalyzes the conversion of guanosine triphosphate (GTP) into N7-methylguanosine triphosphate (m7GTP), which in turn inhibits cap-dependent translation. This inhibition suppresses the type I interferon-mediated induction of interferon-stimulated genes (ISGs), thereby dampening the innate immune response. Overall, our findings reveal how SARS-CoV-2 disrupts host immune defenses through translation inhibition, offering new insights into its pathogenesis. Funding Sources Supported by NIH/NIAID K22AI168257; NIH/NIAID RO1 AI059167; NIH/NHLBI T32HL007974; Rubicon 680-50-1531 Topic Categories Viral Immunology (VIR)