(a) E1B 19K and Bcl-xL abrogate FADD-mediated apoptosis. HeLa cells were transfected with FADD alone or cotransfected with Bcl-2, Bcl-xL, or E1B 19K. Bcl-2, Bcl-xL, and E1B 19K were also each expressed individually as controls. A β-gal viability assay was performed 48 h posttransfection. The percentage of viable cells was compared with 7dl transfected vector control cells. The values represent data from a single experiment that was reproducible in three independent experiments. (b) E1B 19K and Bcl-xL block FLICE-mediated cell death only in the presence of the FADD adaptor molecule. HeLa cells were transfected with FLICE alone or coexpressed with Bcl-2, Bcl-xL, E1B 19K, or FADD. Cells were transfected with FADD and FLICE in the presence of Bcl-2, Bcl-xL, or E1B 19K. Bcl-2, Bcl-xL, and E1B 19K were also each expressed alone as a control. Viability was assessed 48 h posttransfection and compared with the 7dl vector control.