title: Negative regulation of the retinoic acid-inducible gene I-induced antiviral state by the ubiquitin-editing protein A20.
abstract: Activation of the interferon regulatory factors (IRFs) 3 and 7 transcription factors is essential for the induction of type I interferon (IFN) and development of the innate antiviral response. Retinoic acid-inducible gene I has been shown to contribute to virus-induced IFN production independent of the Toll-like receptor pathways in response to a variety of RNA viruses and double-stranded RNA. In the present study, we demonstrate that the NF-kappaB-inducible, anti-apoptotic protein A20 efficiently blocks RIG-I-mediated activation of NF-kappaB-, IRF-3-, and IRF-7-dependent promoters but only weakly interferes with TRIF-TLR-3-mediated IFN activation. Expression of A20 completely blocked CARD domain containing DeltaRIG-I-induced IRF-3 Ser-396 phosphorylation, homodimerization, and DNA binding. The level of A20 inhibition was upstream of the TBK1/IKKepsilon kinases that phosphorylate IRF3 and IRF7 and paradoxically, A20 selectively degraded the TRIF protein but not RIG-I. A20 possesses two ubiquitin-editing domains, an N-terminal deubiquitination domain and a C-terminal ubiquitin ligase domain consisting of seven zinc finger domains. Deletion of the N-terminal de-ubiquitination domain had no significant effect on the inhibitory effect of A20, whereas deletion or mutation of zinc finger motif 7 ablated the inhibitory function of A20 on IRF- or NF-kappaB-mediated gene expression. Furthermore, cells stably expressing the active form of RIG-I induced an antiviral state that interfered with replication of vesicular stomatitis virus, an effect that was reversed by stable co-expression of A20. These results suggest that the virus-inducible, NF-kappaB-dependent activation of A20 functions as a negative regulator of RIG-I-mediated induction of the antiviral state.
authors.affiliation: Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, and Department of Microbiology, McGill University, Montreal, Quebec H3T 1E2, Canada. rongtuan.lin@mcgill.ca
authors.forename: Rongtuan
authors.initials: R
authors.lastname: Lin
authors.forename: Long
authors.initials: L
authors.lastname: Yang
authors.forename: Peyman
authors.initials: P
authors.lastname: Nakhaei
authors.forename: Qiang
authors.initials: Q
authors.lastname: Sun
authors.forename: Ehssan
authors.initials: E
authors.lastname: Sharif-Askari
authors.forename: Ilkka
authors.initials: I
authors.lastname: Julkunen
authors.forename: John
authors.initials: J
authors.lastname: Hiscott
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000998:Antiviral Agents / Q000737:chemistry; D015153:Blotting, Western; D002460:Cell Line; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D004268:DNA-Binding Proteins; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006801:Humans; D047468:Immunoprecipitation; D007372:Interferons / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008156:Luciferases / Q000378:metabolism; D016296:Mutagenesis; D016328:NF-kappa B / Q000378:metabolism*; D009687:Nuclear Proteins; D016366:Open Reading Frames; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism / Q000502:physiology*; D020365:RNA Helicases / Q000502:physiology*; D012328:RNA Viruses / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000737:chemistry; D011971:Receptors, Immunologic; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry; D015533:Transcriptional Activation; D014162:Transfection; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D025801:Ubiquitin / Q000737:chemistry*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry; D014721:Vesicular stomatitis Indiana virus / Q000378:metabolism; D016335:Zinc Fingers
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D000998:Antiviral Agents; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D011506:Proteins; D012330:RNA, Double-Stranded; D011971:Receptors, Immunologic; C470409:TICAM1 protein, human; D051193:Toll-Like Receptors; D014157:Transcription Factors; D025801:Ubiquitin; D007372:Interferons; D008156:Luciferases; D044767:Ubiquitin-Protein Ligases; C076529:TNFAIP3 protein, human; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases