NF-κB activation by MALT1 and API2-MALT1 is necessary for resistance to FAS-mediated apoptosis and proliferation. (A) BJAB cells expressing no primary transgene (WT) or expressing MALT1 or API2-MALT1 were secondarily infected with empty vector or IκBα superrepressor (SR) and incubated in triplicates with soluble FAS-L. Cell viability was assayed after 16 hours. The results are representative of 2 independent experiments. (B) Cell proliferation was measured by incorporation of ³[H]-thymidine measured in single clones or pools of BJAB cells expressing no transgene (WT), MALT1, or API2-MALT1. Results are shown as cpm, with error bars representing standard deviation obtained from triplicate samples. (C) The same BJAB cells as in panel A with empty second vector (□) or IκBα superrepressor (▪) were assayed for ³[H]-thymidine incorporation as described above. The data shown are 1 of 3 independent experiments. (D) Lysates of equal numbers of the above BJAB cells were immunoblotted against the N-terminal FLAG epitope tag of SR-IκBα to show specific and equal expression.