SARS-CoV PLpro inhibits IRF3(5D) induction of IFNβ. A. Plasmid expressing SARS-CoV PLpro was tested for the ability to inhibit the induction of an IFNβ promoter/luciferase reporter induced by IRF3(5D). The average induction with standard deviation across 3 transfections is graphed relative to mock transfection. HEK293T cells were transfected with plasmids encoding IFNβ promoter/luciferase, Flag-tagged IRF3(5D), empty GFP vector or HA-tagged SARS-CoV PLpro in the combinations noted. At 18 hours post-transfection cells were lysed and firefly luciferase expression quantified. B. Lysate from each transfection in A was analyzed by western blot to assay protein expression of HA-tagged PLpro and Flag-tagged IRF3(5D).