DNA binding reactions (25 µl) containing 10 mM HEPES pH 7.9, 10 µg/ml BSA, 2 mM DTT, 30% glycerol, 20% Ficoll-400, 1 µg poly (dI-dC), 6 µg of nuclear extracts and 10,000 to 20,000 cpm (0.05 to 0.2 ng) of radiolabelled probe were performed for 20 minutes at room temperature.