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Science. 2009 Feb 20;323(5917):1070-4. doi: 10.1126/science.1168352. Epub 2009 Jan 1.

Cytosolic viral sensor RIG-I is a 5'-triphosphate-dependent translocase on double-stranded RNA.

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Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Champaign, IL 61801, USA.


Retinoic acid inducible-gene I (RIG-I) is a cytosolic multidomain protein that detects viral RNA and elicits an antiviral immune response. Two N-terminal caspase activation and recruitment domains (CARDs) transmit the signal, and the regulatory domain prevents signaling in the absence of viral RNA. 5'-triphosphate and double-stranded RNA (dsRNA) are two molecular patterns that enable RIG-I to discriminate pathogenic from self-RNA. However, the function of the DExH box helicase domain that is also required for activity is less clear. Using single-molecule protein-induced fluorescence enhancement, we discovered a robust adenosine 5'-triphosphate-powered dsRNA translocation activity of RIG-I. The CARDs dramatically suppress translocation in the absence of 5'-triphosphate, and the activation by 5'-triphosphate triggers RIG-I to translocate preferentially on dsRNA in cis. This functional integration of two RNA molecular patterns may provide a means to specifically sense and counteract replicating viruses.

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