CHID1 positively regulates RLR antiviral signaling by targeting the RIG-I/VISA signalosome

Retinoic acid-inducible gene-I (RIG-I) belongs to the RIGI-like receptors (RLRs), a class of primary pattern recognition receptors. It senses viral double-strand RNA in the cytoplasm and delivers the activated signal to its adaptor virus-induced signaling adapter (VISA), which then recruits the downstream TNF receptor-associated factors and kinases, triggering a downstream signal cascade that leads to the production of proinflammatory cytokines and antiviral interferons (IFNs). However, the mechanism of RIG-I-mediated antiviral signaling is not fully understood. Here, we demonstrate that chitinase domain-containing 1 (CHID1), a member of the chitinase family, positively regulates the RLR antiviral signaling pathway by targeting the RIG-I/VISA signalosome. CHID1 overexpression enhances the activation of nuclear factor kappa B (NF-kB) and interferon regulatory factor 3 (IRF3) triggered by Sendai virus (SeV) by promoting the polyubiquitination of RIG-I and VISA, thereby potentiating IFN-beta production. CHID1 knockdown in human 239T cells inhibits SeV-induced activation of IRF3 and NF-kappa B and the induction of IFN-beta. These results indicate that CHID1 positively regulates RLR antiviral signal, revealing the novel mechanism of the RIG-I antiviral signaling pathway.