BCL3 represses TNF-induced NF-κB–dependent transcription. COS cells were transiently transfected with pGL3-TK-κBPD, pRL-TK and either the BCL3 cDNA in the pEF-BOS plasmid or the empty vector. After 24 hours, cells were stimulated or not stimulated with TNF (10 ng/mL). Luciferase activities were monitored 8 hours later. The results correspond to the mean ± SD of 4 individual transfections and are expressed as arbitrary units of luciferase activity, with 1 U being defined as the luciferase activity in unstimulated cells.