STAT3 DNA binding is constitutively activated in B9-WT and B9-TD cells.

Nuclear extracts were prepared from B9, B9 MINV, B9-WT#3, and B9-TD#14 stimulated with and without interleukin-6 for 10 minutes at 37°C. Complexes were resolved on a 5% native polyacrylamide gel. The specificity of DNA binding was determined by the addition of unlabeled IRF-1 oligonucleotide (S) or a nonspecific oligonucleotide from the T14 promoter (N) and by incubation with a peptide-specific STAT3 antibody. (The absence of supershifting in B9-MINV and B9-WT cells is likely technical in nature.)