Effect of SARS-CoV PLpro on localization of IRF3 and IRF3(5D). Plasmids expressing either Flag-tagged IRF3, Flag-tagged IRF3(5D) or HA-tagged PLpro were transfected alone or in combination into HeLa cells and visualized with anti-Flag or anti-HA antibody. A. Flag-tagged IRF3 alone (left) or after SeV infection (middle), Flag-tagged IRF3 co-transfected with HA-tagged PLpro after SeV infection (right) B. Flag-tagged IRF3(5D) alone (left), HA-tagged PLpro alone (middle) and Flag-tagged IRF3(5D) co-transfected with HA-tagged PLpro. All cells fixed in 4% PFA and visualized with Alexa 488 conjugated anti-rabbit or Alexa 594 conjugated anti-mouse antibodies. Nuclei are delineated by white dashed lines.