title: TRIM13 is a negative regulator of MDA5-mediated type I interferon production.
abstract: Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are essential intracellular detectors of viral RNA. They contribute to the type I interferon (IFN) response that is crucial for host defense against viral infections. Given the potent antiviral and proinflammatory activities elicited by the type I IFNs, induction of the type I IFN response is tightly regulated. Members of the tripartite motif (TRIM) family of proteins have recently emerged as key regulators of antiviral immunity. We show that TRIM13, an E3 ubiquitin ligase, is expressed in immune cells and is upregulated in bone marrow-derived macrophages upon stimulation with inducers of type I IFN. TRIM13 interacts with MDA5 and negatively regulates MDA5-mediated type I IFN production in vitro, acting upstream of IFN regulatory factor 3. We generated Trim13(-/-) mice and show that upon lethal challenge with encephalomyocarditis virus (EMCV), which is sensed by MDA5, Trim13(-/-) mice produce increased amounts of type I IFNs and survive longer than wild-type mice. Trim13(-/-) murine embryonic fibroblasts (MEFs) challenged with EMCV or poly(I · C) also show a significant increase in beta IFN (IFN-β) levels, but, in contrast, IFN-β responses to the RIG-I-detected Sendai virus were diminished, suggesting that TRIM13 may play a role in positively regulating RIG-I function. Together, these results demonstrate that TRIM13 regulates the type I IFN response through inhibition of MDA5 activity and that it functions nonredundantly to modulate MDA5 during EMCV infection.
  
  
  OBJECTIVE
  The type I interferon (IFN) response is crucial for host defense against viral infections, and proper regulation of this pathway contributes to maintaining immune homeostasis. Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are intracellular detectors of viral RNA that induce the type I IFN response. In this study, we show that expression of the gene tripartite motif 13 (Trim13) is upregulated in response to inducers of type I IFN and that TRIM13 interacts with both MDA5 and RIG-I in vitro. Through the use of multiple in vitro and in vivo model systems, we show that TRIM13 is a negative regulator of MDA5-mediated type I IFN production and may also impact RIG-I-mediated type I IFN production by enhancing RIG-I activity. This places TRIM13 at a key junction within the viral response pathway and identifies it as one of the few known modulators of MDA5 activity.
authors.affiliation: Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Narayan
authors.affiliation: Division of Infectious Diseases and Immunology, Program in Innate Immunity, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Waggoner
authors.affiliation: Division of Infectious Diseases and Immunology, Program in Innate Immunity, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Serena T
authors.initials: ST
authors.lastname: Pham
authors.affiliation: Division of Infectious Diseases and Immunology, Program in Innate Immunity, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Gabriel L
authors.initials: GL
authors.lastname: Hendricks
authors.affiliation: Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Waggoner
authors.affiliation: Division of Infectious Diseases and Immunology, Program in Innate Immunity, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Conlon
authors.affiliation: Division of Infectious Diseases and Immunology, Program in Innate Immunity, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Jennifer P
authors.initials: JP
authors.lastname: Wang
authors.affiliation: Division of Infectious Diseases and Immunology, Program in Innate Immunity, University of Massachusetts Medical School, Worcester, Massachusetts, USA Kate.Fitzgerald@umassmed.edu Joonsoo.Kang@umassmed.edu.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Fitzgerald
authors.affiliation: Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, USA Kate.Fitzgerald@umassmed.edu Joonsoo.Kang@umassmed.edu.
authors.forename: Joonsoo
authors.initials: J
authors.lastname: Kang
mesh_terms: D000818:Animals; D018188:Cardiovirus Infections / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000821:virology; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004686:Encephalomyocarditis virus / Q000502:physiology*; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism / Q000821:virology; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000235:genetics / Q000378:metabolism; D000072640:Interferon-Induced Helicase, IFIH1; D016898:Interferon-alpha / Q000235:genetics / Q000378:metabolism*; D016899:Interferon-beta / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D050838:Interferon Regulatory Factor-3; D016898:Interferon-alpha; D000070584:Tripartite Motif Proteins; D016899:Interferon-beta; C000594665:TRIM13 protein, mouse; D044767:Ubiquitin-Protein Ligases; C510592:Ifih1 protein, mouse; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1