Fig. 3.

The signaling pathways for RLRs. After RNA virus or DNA virus infection, RIG-I recognizes 5’-ppp-dsRNA, 5’-ppp-ssRNA, and short dsRNA, while MDA-5 recognizes long dsRNA. Then RIG-I and MDA5 undergo lysine 63-linked polyubiquitin modification and form homotetramerization, respectively. Afterward, the homotetramerization recruits the MAVS and activates TRAF, which further activates TRAF3-TBK1-IKKε-IRF3/IRF7 pathway to produce type I IFNs, and activates RIP1-IKK complex-NF-κB pathway to induce proinflammatory cytokines secretion, including IL-1β, IL-6, IL-8 and TNF-α