Identification of loss of function mutations in human genes encoding RIG-I and MDA5: implications for resistance to type I diabetes.
Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are essential for detecting viral RNA and triggering antiviral responses, including production of type I interferon. We analyzed the phenotype of non-synonymous mutants of human RIG-I and MDA5 reported in databases by functional complementation in cell cultures. Of seven missense mutations of RIG-I, S183I, which occurs within the second caspase recruitment domain repeat, inactivated this domain and conferred a dominant inhibitory function. Of 10 mutants of MDA5, two exhibited loss of function. A nonsense mutation, E627*, resulted in deletion of the C-terminal region and double-stranded RNA (dsRNA) binding activity. Another loss of function mutation, I923V, which occurs within the C-terminal domain, did not affect dsRNA binding activity, suggesting a novel and essential role for this residue in the signaling. Remarkably, these mutations are implicated in resistance to type I diabetes. However, the A946T mutation of MDA5, which has been implicated in type I diabetes by previous genetic analyses, affected neither dsRNA binding nor IFN gene activation. These results provide new insights into the structure-function relationship of RIG-I-like receptors as well as into human RIG-I-like receptor polymorphisms, antiviral innate immunity, and autoimmune diseases.
Shigemoto
Taeko
T
Laboratory of Molecular Genetics, Institute for Virus Research Kyoto University, Kyoto 606-8507; Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507.
Kageyama
Maiko
M
Laboratory of Molecular Genetics, Institute for Virus Research Kyoto University, Kyoto 606-8507; Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507.
Hirai
Reiko
R
Laboratory of Molecular Genetics, Institute for Virus Research Kyoto University, Kyoto 606-8507.
Zheng
JiPing
J
Laboratory of Molecular Genetics, Institute for Virus Research Kyoto University, Kyoto 606-8507.
Yoneyama
Mitsutoshi
M
Laboratory of Molecular Genetics, Institute for Virus Research Kyoto University, Kyoto 606-8507; Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507; PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan.
Fujita
Takashi
T
Laboratory of Molecular Genetics, Institute for Virus Research Kyoto University, Kyoto 606-8507; Laboratory of Molecular Cell Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507. Electronic address: tfujita@virus.kyoto-u.ac.jp.