DEAD/H BOX 3 (DDX3) helicase binds the RIG-I adaptor IPS-1 to up-regulate IFN-beta-inducing potential

Eur J Immunol. 2010 Apr;40(4):940-8. doi: 10.1002/eji.200940203.

Abstract

Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLR) are members of the DEAD box helicases, and recognize viral RNA in the cytoplasm, leading to IFN-beta induction through the adaptor IFN-beta promoter stimulator-1 (IPS-1) (also known as Cardif, mitochondrial antiviral signaling protein or virus-induced signaling adaptor). Since uninfected cells usually harbor a trace of RIG-I, other RNA-binding proteins may participate in assembling viral RNA into the IPS-1 pathway during the initial response to infection. We searched for proteins coupling with human IPS-1 by yeast two-hybrid and identified another DEAD (Asp-Glu-Ala-Asp) box helicase, DDX3 (DEAD/H BOX 3). DDX3 can bind viral RNA to join it in the IPS-1 complex. Unlike RIG-I, DDX3 was constitutively expressed in cells, and some fraction of DDX3 is colocalized with IPS-1 around mitochondria. The 622-662 a.a DDX3 C-terminal region (DDX3-C) directly bound to the IPS-1 CARD-like domain, and the whole DDX3 protein also associated with RLR. By reporter assay, DDX3 helped IPS-1 up-regulate IFN-beta promoter activation and knockdown of DDX3 by siRNA resulted in reduced IFN-beta induction. This activity was conserved on the DDX3-C fragment. DDX3 only marginally enhanced IFN-beta promoter activation induced by transfected TANK-binding kinase 1 (TBK1) or I-kappa-B kinase-epsilon (IKKepsilon). Forced expression of DDX3 augmented virus-mediated IFN-beta induction and host cell protection against virus infection. Hence, DDX3 is an antiviral IPS-1 enhancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / immunology*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Cell Line / drug effects
  • Cell Line / immunology
  • Chlorocebus aethiops
  • DEAD Box Protein 58
  • DEAD-box RNA Helicases / genetics
  • DEAD-box RNA Helicases / immunology*
  • DEAD-box RNA Helicases / metabolism
  • Gene Knockdown Techniques
  • Humans
  • Interferon Inducers / pharmacology
  • Interferon-Induced Helicase, IFIH1
  • Interferon-beta / biosynthesis*
  • Interferon-beta / genetics
  • Multiprotein Complexes
  • Poliovirus / immunology
  • Poly I-C / pharmacology
  • Protein Interaction Mapping
  • Protein Structure, Tertiary
  • RNA Interference
  • RNA, Small Interfering / genetics
  • RNA, Viral / immunology*
  • Recombinant Fusion Proteins / immunology
  • Signal Transduction
  • Vero Cells
  • Vesicular stomatitis Indiana virus / immunology

Substances

  • Adaptor Proteins, Signal Transducing
  • Interferon Inducers
  • MAVS protein, human
  • Multiprotein Complexes
  • RNA, Small Interfering
  • RNA, Viral
  • Recombinant Fusion Proteins
  • Interferon-beta
  • DDX3X protein, human
  • DDX58 protein, human
  • IFIH1 protein, human
  • DEAD Box Protein 58
  • DEAD-box RNA Helicases
  • Interferon-Induced Helicase, IFIH1
  • Poly I-C