Structural basis for the activation of innate immune pattern-recognition receptor RIG-I by viral RNA |
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Authors: | Kowalinski Eva Lunardi Thomas McCarthy Andrew A Louber Jade Brunel Joanna Grigorov Boyan Gerlier Denis Cusack Stephen |
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Affiliation: | 1 European Molecular Biology Laboratory, Grenoble Outstation, 6 rue Jules Horowitz, BP181, 38042 Grenoble Cedex 9, France 2 Unit of Virus Host-Cell Interactions, UJF-EMBL-CNRS, UMI 3265, 6 rue Jules Horowitz, BP181, 38042 Grenoble Cedex 9, France 3 Human Virology, INSERM U758, ENS Lyon, Université Lyon 1, 21 Avenue Tony Garnier, 69007 Lyon, France |
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Abstract: | RIG-I is a key innate immune pattern-recognition receptor that triggers interferon expression upon detection of intracellular 5'triphosphate double-stranded RNA (5'ppp-dsRNA) of viral origin. RIG-I comprises N-terminal caspase activation and recruitment domains (CARDs), a DECH helicase, and a C-terminal domain (CTD). We present crystal structures of the ligand-free, autorepressed, and RNA-bound, activated states of RIG-I. Inactive RIG-I has an open conformation with the CARDs sequestered by a helical domain inserted between the two helicase moieties. ATP and dsRNA binding induce a major rearrangement to a closed conformation in which the helicase and CTD bind the blunt end 5'ppp-dsRNA with perfect complementarity but incompatibly with continued CARD binding. We propose that after initial binding of 5'ppp-dsRNA to the flexibly linked CTD, co-operative tight binding of ATP and RNA to the helicase domain liberates the CARDs for downstream signaling. These findings significantly advance our molecular understanding of the activation of innate immune signaling helicases. |
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