To know how the NSs suppressed the eIF2a phosphorylation activity of the PKR function, a dsRNA-binding assay was performed to test the possibility that the NSs binds to dsRNA, sequesters dsRNA from PKR, and interferes with the dsRNAmediated PKR activation. 293 cells were mock-infected or infected with rMP12-NSs-Flag carrying Flag-tagged NSs, rMP12-rLuc-Flag carrying Flag-tagged rLuc ( Figure 6A ) or rMP12-PKRDE7 ( Figure 5A ). In a separate experiment, 293 cells were transfected with in vitro-synthesized RNA transcripts encoding NSs. Lysates were prepared at 16 h.p.i. or 16 h post-transfection, and incubated with poly I:C beads (dsRNA) or poly (C) beads (ssRNA). Then the dsRNA-bound complexes were analyzed by a Western blot in which we used an anti-Flag antibody or anti-NSs antibody ( Figure 6B ). As expected, dsRNA bound to PKRDE7 [36] , whereas it poorly bound to the NSs from rMP12-NSs-Flaginfected cells and that from the NSs-expressing cells ( Figure 6B ), which suggested that NSs did not suppress PKR activation by its binding to dsRNA.