The nucleocytoplasmic rabies virus P protein counteracts interferon signaling by inhibiting both nuclear accumulation and DNA binding of STAT1

J Virol. 2007 Apr;81(8):4255-63. doi: 10.1128/JVI.01930-06. Epub 2007 Feb 7.

Abstract

Rabies virus P protein inhibits alpha interferon (IFN-alpha)- and IFN-gamma-stimulated Jak-STAT signaling by retaining phosphorylated STAT1 in the cytoplasm. Here, we show that P also blocks an intranuclear step that is the STAT1 binding to the DNA promoter of IFN-responsive genes. As P is a nucleocytoplasmic shuttling protein, we first investigated the effect of the cellular distribution of P on the localization of STAT1 and consequently on IFN signaling. We show that the localization of STAT1 is correlated with the localization of P: in cells expressing a nuclear form of P (the short P3 isoform or the complete P in the presence of the export inhibitor leptomycin B), STAT1 is nuclear, whereas in cells expressing a cytoplasmic form of P, STAT1 is cytoplasmic. However, the expression of nuclear forms of P inhibits the signaling of both IFN-gamma and IFN-alpha, demonstrating that the retention of STAT1 in the cytoplasm is not the only mechanism involved in the inhibition of IFN signaling. Electrophoretic mobility shift analysis indicates that P expression in the cell extracts of infected cells or in stable cell lines prevents IFN-induced DNA binding of STAT1. The loss of the DNA binding of STAT1 and ISGF3 was also observed when purified recombinant P or P3 was added to the extracts of IFN-gamma- or IFN-alpha-treated cells, indicating that P directly affects the DNA binding activity of STAT1. Then products of the rabies virus P gene are able to counteract IFN signaling by creating both cytoplasmic and nuclear blocks for STAT1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • DNA / metabolism
  • Electrophoretic Mobility Shift Assay
  • Immunohistochemistry
  • Interferon-Stimulated Gene Factor 3, gamma Subunit / antagonists & inhibitors
  • Interferons / immunology*
  • Interferons / metabolism
  • Microscopy, Confocal
  • Molecular Chaperones
  • Phosphoproteins / physiology*
  • Protein Binding
  • Rabies virus / physiology*
  • STAT1 Transcription Factor / metabolism
  • Signal Transduction
  • Viral Structural Proteins / physiology*

Substances

  • IRF9 protein, human
  • Interferon-Stimulated Gene Factor 3, gamma Subunit
  • Molecular Chaperones
  • P phosphoprotein, Rabies virus
  • Phosphoproteins
  • STAT1 Transcription Factor
  • STAT1 protein, human
  • Viral Structural Proteins
  • DNA
  • Interferons