DDX60 Is Involved in RIG-I-Dependent and Independent Antiviral Responses, and Its Function Is Attenuated by Virus-Induced EGFR Activation.

RIG-I-mediated type I interferon (IFN) production and nuclease-mediated viral RNA degradation are essential for antiviral innate immune responses. DDX60 is an IFN-inducible cytoplasmic helicase. Here, we report that DDX60 is a sentinel for both RIG-I activation and viral RNA degradation. We show that DDX60 is an upstream factor of RIG-I that activates RIG-I signaling in a ligand-specific manner. DDX60 knockout attenuates RIG-I signaling and significantly reduces virus-induced type I IFN production in vivo. In addition, we show that DDX60 is involved in RIG-I-independent viral RNA degradation. DDX60 and RIG-I adaptor MAVS double-knockout mice reveal a role for DDX60-dependent RNA degradation in antiviral responses. Several viruses induced DDX60 phosphorylation via epidermal growth factor receptor (EGFR), leading to attenuation of the DDX60 antiviral activities. Our results define DDX60 as a sentinel for cytoplasmic antiviral response, which is counteracted by virus-mediated EGF receptor activation.