The nucleocytoplasmic rabies virus P protein counteracts interferon signaling by inhibiting both nuclear accumulation and DNA binding of STAT1.
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.
Vidy
Aurore
A
Unité Mixte de Virologie Moléculaire et Structurale, UMR 2472, CNRS, 91198 Gif sur Yvette Cedex, France.
El Bougrini
Jamila
J
Chelbi-Alix
Mounira K
MK
Blondel
Danielle
D
D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D007150:Immunohistochemistry; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit / Q000037:antagonists & inhibitors; D007372:Interferons / Q000276:immunology* / Q000378:metabolism; D018613:Microscopy, Confocal; D018832:Molecular Chaperones; D010750:Phosphoproteins / Q000502:physiology*; D011485:Protein Binding; D011820:Rabies virus / Q000502:physiology*; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D015678:Viral Structural Proteins / Q000502:physiology*
C494227:IRF9 protein, human; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D018832:Molecular Chaperones; C103961:P phosphoprotein, Rabies virus; D010750:Phosphoproteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015678:Viral Structural Proteins; D004247:DNA; D007372:Interferons