A Conserved Histidine in the RNA Sensor RIG-I Controls Immune Tolerance to N1-2′O-Methylated Self RNA

• DOI: 10.1016/j.immuni.2015.06.015
• Publication Date: 2015-07-15T00:03:41Z
• Authors: Christine Schuber...; Janos Ludwig; Ann Kristin Bruder; Anna-Maria Herzner; Thomas Zillinger; Marion Goldeck; Tobias Schmidt; Jonathan L. Schmi...; Romy Kerber; Steven Wolter; Jan-Philip Stümpel; Andreas Roth; Eva Bartok; Christian Drosten; Christoph Coch; Veit Hornung; Winfried Barchet; Beate M. Kümmerer; Gunther Hartmann; Martin Schlee
• Keywords: mRNA; Immunology; immune recognition of RNA; virus; cap; Methylation; Article; RIG-I; DEAD-box RNA Helicases; Mice; Immune Tolerance; Immunology and Allergy; Animals; Humans; MTr1; Histidine; Amino Acid Sequence; RNA Processing, Post-Transcriptional; Receptors, Immunologic; Cells, Cultured; 2′O-methyl; Methyltransferases; Protein Structure, Tertiary; 3. Good health; Enzyme Activation; Infectious Diseases; 5′-triphosphate RNA; DEAD Box Protein 58; RNA; RNA, Viral; innate immune tolerance mechanism; Yellow fever virus

The cytosolic helicase retinoic acid-inducible gene-I (RIG-I) initiates immune responses to most RNA viruses by detecting viral 5'-triphosphorylated RNA (pppRNA). Although endogenous mRNA is also 5'-triphosphorylated, backbone modifications and the 5'-ppp-linked methylguanosine ((m7)G) cap prevent immunorecognition. Here we show that the methylation status of endogenous capped mRNA at the 5'-terminal nucleotide (N1) was crucial to prevent RIG-I activation. Moreover, we identified a single conserved amino acid (H830) in the RIG-I RNA binding pocket as the mediator of steric exclusion of N1-2'O-methylated RNA. H830A alteration (RIG-I(H830A)) restored binding of N1-2'O-methylated pppRNA. Consequently, endogenous mRNA activated the RIG-I(H830A) mutant but not wild-type RIG-I. Similarly, knockdown of the endogenous N1-2'O-methyltransferase led to considerable RIG-I stimulation in the absence of exogenous stimuli. Studies involving yellow-fever-virus-encoded 2'O-methyltransferase and RIG-I(H830A) revealed that viruses exploit this mechanism to escape RIG-I. Our data reveal a new role for cap N1-2'O-methylation in RIG-I tolerance of self-RNA.