Dominant negative mutant of SEK prevented ceramide- but not Fas-induced apoptosis. Jurkat cells were transfected with 5 μg of either SEK1(A→L) or pEBG vector, together with 5 μg of pEGFP-N1 (Clontech). Thirty-six hours later, cells were untreated (Ctr) or treated with either C₂-ceramide (5 μmol/L) or anti-Fas antibody CH11 (100 ng/mL) (Induction). Ceramide-induced cell death was analyzed 6 hours later, whereas Fas-induced cell death were quantitated 12 hours later. Data are the average of duplicates.