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Journal of Virology, April 2007, p. 4255-4263, Vol. 81, No. 8
0022-538X/07/$08.00+0 doi:10.1128/JVI.01930-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Jamila El Bougrini,2,
Mounira K. Chelbi-Alix,2 and
Danielle Blondel1*
CNRS, UMR2472, IFR 115, and INRA, UMR1157, Virologie Moléculaire et Structurale, 91198 Gif sur Yvette, France,1 FRE 2944 CNRS, Institut Lwoff, 7 rue Guy Moquet, 94801 Villejuif, France2
Received 5 September 2006/ Accepted 29 January 2007
Rabies virus P protein inhibits alpha interferon (IFN-
)- and IFN-
-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-
and IFN-
, 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-
- or IFN-
-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.
Published ahead of print on 7 February 2007.
These authors contributed equally to this work.
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