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Mol Cell. 2008 Feb 1;29(2):169-79. doi: 10.1016/j.molcel.2007.10.032.

The C-terminal regulatory domain is the RNA 5'-triphosphate sensor of RIG-I.

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1
Gene Center, Department of Chemistry and Biochemistry, Ludwig-Maximilians-University of Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.

Abstract

The ATPase RIG-I senses viral RNAs that contain 5'-triphosphates in the cytoplasm. It initiates a signaling cascade that activates innate immune response by interferon and cytokine production, providing essential antiviral protection for the host. The mode of RNA 5'-triphosphate sensing by RIG-I remains elusive. We show that the C-terminal regulatory domain RD of RIG-I binds viral RNA in a 5'-triphosphate-dependent manner and activates the RIG-I ATPase by RNA-dependent dimerization. The crystal structure of RD reveals a zinc-binding domain that is structurally related to GDP/GTP exchange factors of Rab-like GTPases. The zinc coordination site is essential for RIG-I signaling and is also conserved in MDA5 and LGP2, suggesting related RD domains in all three enzymes. Structure-guided mutagenesis identifies a positively charged groove as likely 5'-triphosphate-binding site of RIG-I. This groove is distinct in MDA5 and LGP2, raising the possibility that RD confers ligand specificity.

PMID:
18243112
DOI:
10.1016/j.molcel.2007.10.032
[Indexed for MEDLINE]
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