Figure 4.

Identification of STAT1 as the NSs target for IFN-γ signaling suppression. (A) Results of mass spectrum analysis. The purified NSs-associated proteins or the agarose bead-binding products (control) were subjected to LC-MS/MS analysis. STAT1, the key transcription factor in IFN-γ signaling pathway, was specifically identified in the NSs coprecipitates. The tandem spectra of two representative peptides (identified with >99% confidence) of STAT1 (accession, NP_009330) were shown. (B) Validation of the NSs-STAT1 interaction. HEK293 cells were transfected with the control plasmid (vector) or plasmids encoding NSs-S or NP-S. At 24 h post-transfection, protein interactions were examined by pulldown assay. Subsequently, pulldown products and cell lysates (lysate input) were subjected to WB analyses using the indicated antibodies.