FIG. 6.

Overexpression of Bcl-2 reduces M protein and actinomycin D-induced activation of caspase-8 and -9. The HeLa cell lines were either transfected with M mRNA (A and B), treated with actinomycin D (C and D), or treated with TRAIL (E and F) and analyzed for the activation of caspase-8-like activity (A, C, and E) or caspase-9-like activity (B, D, and F) with fluorogenic substrates preferentially cleaved by each caspase. The HeLa cell lines were transfected with M mRNA for 18 (open bars) or 24 (solid bars) h. Cells were transfected with yeast RNA as negative controls. Treatment with actinomycin D was for 6 (open bars) or 12 (solid bars) h, and cells harvested at 0 h were negative controls. Treatment with TRAIL was for 6 h, and cells harvested at 0 h were negative controls. Cell lysates were analyzed for caspase-8- or -9-like activities and protein concentrations as described in the legend to Fig. 2. The amount of caspase-8 and -9 activity is expressed in arbitrary fluorescence units per milligram of protein. The data represent the average ± standard deviation of three experiments.