FIG. 7.

(A to C) NSs protein blocks promoter activation mediated by IRF-3, NF-κB, and AP-1. 293 cells were cotransfected with expression plasmids for NSs or GFP (as a control) and reporter constructs containing the indicated transcription factor binding sites of the IFN-β promoter. Promoter activation was achieved by coexpression of the constitutively active IRF-3 mutant IRF-3(5D) (A), incubation with tumor necrosis factor alpha (TNF-α) (B), or coexpression of MEK kinase (MEKK) (C). (D) NSs inhibits transcriptional activation of a constitutive promoter. Cells were cotransfected with expression plasmids for NSs or GFP (as a control) and a reporter construct containing a constitutively active SV40 promoter. Promoter-independent activation of transcription was achieved by incubation with TSA. rel., relative.