Tripartite motif (TRIM) family proteins are important effectors of innate immunity against viral infections. Here we identified TRIM35 as a regulator of TRAF3 activation. Deficiency in or inhibition of TRIM35 suppressed the production of type I interferon (IFN) in response to viral infection. Trim35-deficient mice were more susceptible to influenza A virus (IAV) infection than were wild-type mice. TRIM35 promoted the RIG-I-mediated signaling by catalyzing Lys63-linked polyubiquitination of TRAF3 and the subsequent formation of a signaling complex with VISA and TBK1. IAV PB2 polymerase countered the innate antiviral immune response by impeding the Lys63-linked polyubiquitination and activation of TRAF3. TRIM35 mediated Lys48-linked polyubiquitination and proteasomal degradation of IAV PB2, thereby antagonizing its suppression of TRAF3 activation. Our in vitro and in vivo findings thus reveal novel roles of TRIM35, through catalyzing Lys63- or Lys48-linked polyubiquitination, in RIG-I antiviral immunity and mechanism of defense against IAV infection.
A549 Cells ; Animals ; Apoptosis Regulatory Proteins/immunology* ; DEAD Box Protein 58/immunology* ; Dogs ; HEK293 Cells ; Humans ; Influenza A Virus, H1N1 Subtype/immunology* ; Madin Darby Canine Kidney Cells ; Mice ; Mice, Knockout ; Orthomyxoviridae Infections/pathology* ; Proteolysis ; RAW 264.7 Cells ; Signal Transduction/immunology* ; THP-1 Cells ; TNF Receptor-Associated Factor 3/immunology* ; Ubiquitination/immunology* ; Viral Proteins/immunology*

Hepatitis B virus (HBV) is regarded as a stealth virus, invading and replicating efficiently in human liver undetected by host innate antiviral immunity. Here, we show that type I interferon (IFN) induction but not its downstream signaling is blocked by HBV replication in HepG2.2.15 cells. This effect may be partially due to HBV X protein (HBx), which impairs IFNβ promoter activation by both Sendai virus (SeV) and components implicated in signaling by viral sensors. As a deubiquitinating enzyme (DUB), HBx cleaves Lys63-linked polyubiquitin chains from many proteins except TANK-binding kinase 1 (TBK1). It binds and deconjugates retinoic acid-inducible gene I (RIG I) and TNF receptor-associated factor 3 (TRAF3), causing their dissociation from the downstream adaptor CARDIF or TBK1 kinase. In addition to RIG I and TRAF3, HBx also interacts with CARDIF, TRIF, NEMO, TBK1, inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase epsilon (IKKi) and interferon regulatory factor 3 (IRF3). Our data indicate that multiple points of signaling pathways can be targeted by HBx to negatively regulate production of type I IFN.
Animals ; B-Lymphocytes ; immunology ; metabolism ; Cell Line ; DEAD Box Protein 58 ; DEAD-box RNA Helicases ; antagonists & inhibitors ; immunology ; metabolism ; Hep G2 Cells ; Hepatitis B virus ; immunology ; metabolism ; Humans ; I-kappa B Kinase ; antagonists & inhibitors ; immunology ; metabolism ; Immune Evasion ; Immunity, Innate ; Interferon Regulatory Factor-3 ; antagonists & inhibitors ; immunology ; metabolism ; Interferon Type I ; antagonists & inhibitors ; immunology ; metabolism ; Mice ; Molecular Targeted Therapy ; Polyubiquitin ; antagonists & inhibitors ; metabolism ; Protein Binding ; immunology ; Sendai virus ; immunology ; metabolism ; Signal Transduction ; immunology ; TNF Receptor-Associated Factor 3 ; antagonists & inhibitors ; immunology ; metabolism ; Trans-Activators ; immunology ; metabolism