title: EFTUD2 Is a Novel Innate Immune Regulator Restricting Hepatitis C Virus Infection through the RIG-I/MDA5 Pathway.
abstract: The elongation factor Tu GTP binding domain-containing protein 2 (EFTUD2) was identified as an anti-hepatitis C virus (HCV) host factor in our recent genome-wide small interfering RNA (siRNA) screen. In this study, we sought to further determine EFTUD2's role in HCV infection and investigate the interaction between EFTUD2 and other regulators involved in HCV innate immune (RIG-I, MDA5, TBK1, and IRF3) and JAK-STAT1 pathways. We found that HCV infection decreased the expression of EFTUD2 and the viral RNA sensors RIG-I and MDA5 in HCV-infected Huh7 and Huh7.5.1 cells and in liver tissue from in HCV-infected patients, suggesting that HCV infection downregulated EFTUD2 expression to circumvent the innate immune response. EFTUD2 inhibited HCV infection by inducing expression of the interferon (IFN)-stimulated genes (ISGs) in Huh7 cells. However, its impact on HCV infection was absent in both RIG-I knockdown Huh7 cells and RIG-I-defective Huh7.5.1 cells, indicating that the antiviral effect of EFTUD2 is dependent on RIG-I. Furthermore, EFTUD2 upregulated the expression of the RIG-I-like receptors (RLRs) RIG-I and MDA5 to enhance the innate immune response by gene splicing. Functional experiments revealed that EFTUD2-induced expression of ISGs was mediated through interaction of the EFTUD2 downstream regulators RIG-I, MDA5, TBK1, and IRF3. Interestingly, the EFTUD2-induced antiviral effect was independent of the classical IFN-induced JAK-STAT pathway. Our data demonstrate that EFTUD2 restricts HCV infection mainly through an RIG-I/MDA5-mediated, JAK-STAT-independent pathway, thereby revealing the participation of EFTUD2 as a novel innate immune regulator and suggesting a potentially targetable antiviral pathway.
  
  
  OBJECTIVE
  Innate immunity is the first line defense against HCV and determines the outcome of HCV infection. Based on a recent high-throughput whole-genome siRNA library screen revealing a network of host factors mediating antiviral effects against HCV, we identified EFTUD2 as a novel innate immune regulator against HCV in the infectious HCV cell culture model and confirmed that its expression in HCV-infected liver tissue is inversely related to HCV infection. Furthermore, we determined that EFTUD2 exerts its antiviral activity mainly through governing its downstream regulators RIG-I and MDA5 by gene splicing to activate IRF3 and induce classical ISG expression independent of the JAT-STAT signaling pathway. This study broadens our understanding of the HCV innate immune response and provides a possible new antiviral strategy targeting this novel regulator of the innate response.
authors: Department of Infectious Disease, Anhui Provincial Hospital, Anhui Medical University, Hefei, Anhui, China Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA Department of Infectious Diseases, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors: Chuanlong
authors: C
authors: Zhu
authors: Department of Infectious Disease, Anhui Provincial Hospital, Anhui Medical University, Hefei, Anhui, China Department of Infectious Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors: Fei
authors: F
authors: Xiao
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Jian
authors: J
authors: Hong
authors: Department of Infectious Disease, Anhui Provincial Hospital, Anhui Medical University, Hefei, Anhui, China.
authors: Kun
authors: K
authors: Wang
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Xiao
authors: X
authors: Liu
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Dachuan
authors: D
authors: Cai
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Dahlene N
authors: DN
authors: Fusco
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Lei
authors: L
authors: Zhao
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Soung Won
authors: SW
authors: Jeong
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Cynthia
authors: C
authors: Brisac
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Pattranuch
authors: P
authors: Chusri
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Esperance A
authors: EA
authors: Schaefer
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA Department of Infectious Diseases, Peking University First Hospital, Beijing, China.
authors: Hong
authors: H
authors: Zhao
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors: Lee F
authors: LF
authors: Peng
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA wlin1@mgh.harvard.edu Chung.Raymond@mgh.harvard.edu.
authors: Wenyu
authors: W
authors: Lin
authors: Liver Center and Gastrointestinal Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA wlin1@mgh.harvard.edu Chung.Raymond@mgh.harvard.edu.
authors: Raymond T
authors: RT
authors: Chung
mesh_terms: D002460:Cell Line; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D016174:Hepacivirus / Q000276:immunology*; D022781:Hepatocytes / Q000276:immunology / Q000821:virology; D006801:Humans; D007113:Immunity, Innate; D007155:Immunologic Factors / Q000378:metabolism*; D000072640:Interferon-Induced Helicase, IFIH1; D010445:Peptide Elongation Factors / Q000378:metabolism*; D011971:Receptors, Immunologic; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000378:metabolism*
chemical_list: C581608:EFTUD2 protein, human; D007155:Immunologic Factors; D010445:Peptide Elongation Factors; D011971:Receptors, Immunologic; D017415:Ribonucleoprotein, U5 Small Nuclear; C452820:RIGI protein, human; C452815:IFIH1 protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1