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- Michaela U. Gack
- Department of Microbiology and Molecular Genetics, New England Primate Research Center, Harvard Medical School, One Pine Hill Drive, Southborough, Massachusetts 01772-9102
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- Estanislao Nistal-Villán
- Department of Microbiology
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- Kyung-Soo Inn
- Department of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Harlyne J. Norris Cancer Research Tower, 1450 Biggy Street, Los Angeles, California 90033
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- Adolfo García-Sastre
- Department of Microbiology
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- Jae U. Jung
- Department of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Harlyne J. Norris Cancer Research Tower, 1450 Biggy Street, Los Angeles, California 90033
説明
<jats:title>ABSTRACT</jats:title> <jats:p>Recognition of invading viruses by the host is elicited by cellular sensors which trigger signaling cascades that lead to type I interferon (IFN) gene expression. Retinoic acid-inducible gene I (RIG-I) has emerged as a key receptor for the detection of viral RNA in the cytosol, inducing IFN-mediated innate immune responses to limit viral replication through its interaction with MAVS (also called IPS-1, CARDIF, or VISA). Upon the recognition of viral RNA, the Lys-172 residue of RIG-I undergoes ubiquitination induced by tripartite motif protein 25 (TRIM25), an essential protein for antiviral signal transduction. Here we demonstrate that phosphorylation represents another regulatory mechanism for RIG-I-mediated antiviral activity. Using protein purification and mass spectrometry analysis, we identified three phosphorylation sites in the amino-terminal caspase recruitment domains (CARDs) of RIG-I. One of these residues, Thr-170, is located in close proximity to Lys-172, and we speculated that its phosphorylation may affect Lys-172 ubiquitination and functional activation of RIG-I. Indeed, a RIG-I mutant carrying a phosphomimetic Glu residue in place of Thr-170 loses TRIM25 binding, Lys-172 ubiquitination, MAVS binding, and downstream signaling ability. This suggests that phosphorylation of RIG-I at Thr-170 inhibits RIG-I-mediated antiviral signal transduction. Immunoblot analysis with a phospho-specific antibody showed that the phosphorylation of the RIG-I Thr-170 residue is present under normal conditions but rapidly declines upon viral infection. Our results indicate that Thr-170 phosphorylation and TRIM25-mediated Lys-172 ubiquitination of RIG-I functionally antagonize each other. While Thr-170 phosphorylation keeps RIG-I latent, Lys-172 ubiquitination enables RIG-I to form a stable complex with MAVS, thereby inducing IFN signal transduction.</jats:p>
収録刊行物
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- Journal of Virology
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Journal of Virology 84 (7), 3220-3229, 2010-04
American Society for Microbiology