RIG-I (retinoic acid-inducible gene I) is a RIG-I-like receptordsRNAhelicaseenzyme that is encoded (in humans) by the DDX58gene. RIG-I is part of the RIG-I-like receptor family, which also includes MDA5 and LGP2, and functions as a pattern recognition receptor that is a sensor for viruses such as influenza A, Sendai virus, and flavivirus. Certain retroviruses, such as HIV-1, encode a protease that directs RIG-I to the lysosome for degradation, and thereby evade RIG-I mediated signaling. RIG-I typically recognizes short (< 4000nt) 5′triphosphate uncapped double stranded or single stranded RNA. RIG-I and MDA5 are involved in activating MAVS and triggering an antiviral response. RIG-I is also able to detect non-self 5′-triphosphorylated dsRNA transcribed from AT-rich dsDNA by DNA-dependent RNA polymerase III (Pol III). For many viruses, effective RIG-I-mediated antiviral responses are dependent on functionally active LGP2.
DEAD box proteins, characterized by the conserved motif Asp-Glu-Ala-Asp (DEAD), are putative RNA helicases which are implicated in a number of cellular processes involving RNA binding and alteration of RNA secondary structure. RIG-I contains a RNA helicase-DEAD box motifs and a caspase recruitment domain (CARD). RIG-I is involved in viral double-stranded (ds) RNA recognition and the regulation of immune response.
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