Two domains of the V protein of virulent canine distemper virus selectively inhibit STAT1 and STAT2 nuclear import.
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.
Röthlisberger
Anne
A
Department of Clinical Research and Veterinary Public Health, Bremgartenstrasse 109a, 3001 Bern, Switzerland.
Wiener
Dominique
D
Schweizer
Matthias
M
Peterhans
Ernst
E
Zurbriggen
Andreas
A
Plattet
Philippe
P
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002522:Chlorocebus aethiops; D004217:Distemper Virus, Canine / Q000235:genetics / Q000472:pathogenicity*; D055786:Gene Knockout Techniques; D057131:Immune Evasion; D016297:Mutagenesis, Site-Directed; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors*; D050795:STAT2 Transcription Factor / Q000037:antagonists & inhibitors*; D017384:Sequence Deletion; D014709:Vero Cells; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D014764:Viral Proteins