NF-κB activation in premalignant tal-1/scl transgenic thymocytes. Nuclear extracts were prepared from thymocytes from age-matched wild-type and tal-1 transgenic mice. The extracts were incubated with an oligonucleotide probe containing the NF-κB consensus sequence. The binding reactions were fractionated on a 5% polyacrylamide gel and the DNA-protein complexes were detected by autoradiography. The presence of NF-κB subunits was determined by supershifting with antibodies against p50, p65, and c-rel.