A distinct role of Riplet-mediated K63-Linked polyubiquitination of the RIG-I repressor domain in human antiviral innate immune responses.
The innate immune system is essential for controlling viral infections, but several viruses have evolved strategies to escape innate immunity. RIG-I is a cytoplasmic viral RNA sensor that triggers the signal to induce type I interferon production in response to viral infection. RIG-I activation is regulated by the K63-linked polyubiquitin chain mediated by Riplet and TRIM25 ubiquitin ligases. TRIM25 is required for RIG-I oligomerization and interaction with the IPS-1 adaptor molecule. A knockout study revealed that Riplet was essential for RIG-I activation. However the molecular mechanism underlying RIG-I activation by Riplet remains unclear, and the functional differences between Riplet and TRIM25 are also unknown. A genetic study and a pull-down assay indicated that Riplet was dispensable for RIG-I RNA binding activity but required for TRIM25 to activate RIG-I. Mutational analysis demonstrated that Lys-788 within the RIG-I repressor domain was critical for Riplet-mediated K63-linked polyubiquitination and that Riplet was required for the release of RIG-I autorepression of its N-terminal CARDs, which leads to the association of RIG-I with TRIM25 ubiquitin ligase and TBK1 protein kinase. Our data indicate that Riplet is a prerequisite for TRIM25 to activate RIG-I signaling. We investigated the biological importance of this mechanism in human cells and found that hepatitis C virus (HCV) abrogated this mechanism. Interestingly, HCV NS3-4A proteases targeted the Riplet protein and abrogated endogenous RIG-I polyubiquitination and association with TRIM25 and TBK1, emphasizing the biological importance of this mechanism in human antiviral innate immunity. In conclusion, our results establish that Riplet-mediated K63-linked polyubiquitination released RIG-I RD autorepression, which allowed the access of positive factors to the RIG-I protein.
Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Kita-ku, Sapporo, Japan. oshiumi@med.hokudai.ac.jp
Hiroyuki
H
Oshiumi
Moeko
M
Miyashita
Misako
M
Matsumoto
Tsukasa
T
Seya
D019943:Amino Acid Substitution; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002522:Chlorocebus aethiops; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D057809:HEK293 Cells; D056945:Hep G2 Cells; D016174:Hepacivirus / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006526:Hepatitis C / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D018345:Mice, Knockout; D020125:Mutation, Missense; D017434:Protein Structure, Tertiary; D011971:Receptors, Immunologic; D014157:Transcription Factors / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D054875:Ubiquitination / Q000502:physiology*; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D000085242:Viral Proteases
D002352:Carrier Proteins; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011971:Receptors, Immunologic; D014157:Transcription Factors; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D000085242:Viral Proteases; C455041:NS4A cofactor peptide, Hepatitis C virus; C490034:Trim25 protein, mouse; C522809:RNF135 protein, human; C557200:Rnf135 protein, mouse; C084523:TRIM25 protein, human; C452820:RIGI protein, human; C503356:Ddx58 protein, mouse