Two domains of the V protein of virulent canine distemper virus selectively inhibit STAT1 and STAT2 nuclear import

J Virol. 2010 Jul;84(13):6328-43. doi: 10.1128/JVI.01878-09. Epub 2010 Apr 28.

Abstract

Canine distemper virus (CDV) causes in dogs a severe systemic infection, with a high frequency of demyelinating encephalitis. Among the six genes transcribed by CDV, the P gene encodes the polymerase cofactor protein (P) as well as two additional nonstructural proteins, C and V; of these V was shown to act as a virulence factor. We investigated the molecular mechanisms by which the P gene products of the neurovirulent CDV A75/17 strain disrupt type I interferon (IFN-alpha/beta)-induced signaling that results in the establishment of the antiviral state. Using recombinant knockout A75/17 viruses, the V protein was identified as the main antagonist of IFN-alpha/beta-mediated signaling. Importantly, immunofluorescence analysis illustrated that the inhibition of IFN-alpha/beta-mediated signaling correlated with impaired STAT1/STAT2 nuclear import, whereas the phosphorylation state of these proteins was not affected. Coimmunoprecipitation assays identified the N-terminal region of V (VNT) responsible for STAT1 targeting, which correlated with its ability to inhibit the activity of the IFN-alpha/beta-mediated antiviral state. Conversely, while the C-terminal domain of V (VCT) could not function autonomously, when fused to VNT it optimally interacted with STAT2 and subsequently efficiently suppressed the IFN-alpha/beta-mediated signaling pathway. The latter result was further supported by a single mutation at position 110 within the VNT domain of CDV V protein, resulting in a mutant that lost STAT1 binding while retaining a partial STAT2 association. Taken together, our results identified the CDV VNT and VCT as two essential modules that complement each other to interfere with the antiviral state induced by IFN-alpha/beta-mediated signaling. Hence, our experiments reveal a novel mechanism of IFN-alpha/beta evasion among the morbilliviruses.

MeSH terms

  • Active Transport, Cell Nucleus
  • Animals
  • Chlorocebus aethiops
  • Distemper Virus, Canine / genetics
  • Distemper Virus, Canine / pathogenicity*
  • Gene Knockout Techniques
  • Immune Evasion*
  • Mutagenesis, Site-Directed
  • Protein Interaction Mapping
  • Protein Structure, Tertiary
  • STAT1 Transcription Factor / antagonists & inhibitors*
  • STAT2 Transcription Factor / antagonists & inhibitors*
  • Sequence Deletion
  • Vero Cells
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*

Substances

  • STAT1 Transcription Factor
  • STAT2 Transcription Factor
  • Viral Proteins