Mutant IκBα expression inhibits TNF-α-induced NF-κB activation in tal-1/scl tumors.Tal-1 tumor cells were electrophorated with lck-IκBα RR-AA-F-PEST and a plasmid encoding the neomycin resistance gene. Cells were selected for resistance to G418 and subsequently treated with TNFα for the time periods indicated. Nuclear extracts prepared from these cells were incubated with a radiolabeled NF-κB consensus oligonucleotide and fractionated on a 5% nondenaturing polyacrylamide gel.