NF-κB competes with STAT3 binding to the γ fibrinogen site II probe.

The in vitro binding assays were performed as described in “Materials and methods.” Nuclear extracts prepared from rat primary hepatocytes stimulated with IL-6 were used as a crude source of activated STAT3 to show STAT3 DNA binding activity. Recombinant NF-κB p50 protein was premixed with nuclear extracts prepared from control cells or IL-6-stimulated cells at increasing amounts (0.1 ng to 5 ng) before normal EMSA procedures. The arrows on the right side indicate the migration positions of STAT3 and NF-κB complexes. The gel was exposed for 2 days.