Fig. 6

The coronavirus E proteins induce caspase 3 activity. HEK293 cells were either mock-transfected, transfected with pcDNA3.1( +), transfected with pcDNA3.1( +), and treated with 2 µM staurosporine, or transfected with the vectors expressing the E proteins. At 48 h post-transfection, cells were lysed and analyzed for caspase 3 activity according to the manufacturer’s instructions. Fluorescence was measured using a microplate reader using excitation at 342 nm and emission at 441 nm (A) and the expression of the E proteins using an anti-HA antibody (α-HA) and immunoblots (B). Vectors used to transfect cells are at the top of each lane. Assays were performed at least three times