Subcellular localization of SARS-CoV E and N proteins. (A) Subcellular localization of wt or mutant SARS-CoV E proteins. HeLa cells were co-transfected with the indicated HA-tagged wt or mutant E expression vectors plus pGolgi-ECFP, which encodes a Golgi apparatus labeling marker. (B) Co-localization of SARS-CoV E and N proteins. HeLa cells were co-transfected with SARS-CoV N bearing carboxyl-terminal tagged EGFP (N-EGFP) and HA-tagged wt or Δ76V expression vectors. At 18 h post-transfection, cells were fixed and labeled with a primary anti-HA antibody and a secondary rhodamine-conjugated anti-mouse antibody. Images represent the most prevalent phenotypes. Merged red/blue or red/green fluorescent images are shown in right-hand column panels. Mock-transfected cells failed to yield any signal (data not shown).