Figure 6.

E1A-induced caspase-8 activity and apoptosis is inhibited by a procaspase-8L DN mutant. (A) KB cells were transiently cotransfected with plasmids encoding 12S E1A and Nex-Flag-EGFP or 12S E1A and Flag-EGFP and 36 h post transfection equivalent amounts of cell lysate were tested for their ability to hydrolyze the caspase-8-preferred substrate IETD-amc. Shown is the mean of four independent experiments. (B) Cell lysates from A were analyzed by SDS/PAGE and immunoblotting with antibodies against E1A or Flag. (C) As in A, except that cells were collected, stained with Annexin V, and analyzed by flow cytometry. Transfection efficiency was estimated to be 20–30% by analyzing EGFP-positive cells by immunofluorescence (not shown).