FIG. 4.

DNase I footprinting defines regions of the noncoding strand that are involved in DBD binding. Increasing concentrations of purified DBD were incubated with A2 or pS2 ERE-containing DNA fragments which had been labeled on the noncoding strand. The binding reaction was subjected to limited DNase I digestion, and the cleaved DNA was fractionated on a denaturing acrylamide gel. The gel was dried and subjected to autoradiography. The positions and sequences of the A2 and pS2 EREs are indicated.