Small-scale agarose gel electrophoresis. 32P-labeled, ERE-containing oligos were incubated without (lane 1) or with ERα (lanes 2, 4–8) and/or HeLa nuclear extracts (NX, lanes 3–8). Nonspecific (NS) antibody (lane 5), ERα-specific antibody (lane 6), unlabeled oligos containing a nonspecific (NS) DNA sequence (lane 7), or unlabeled ERE-containing oligos (lane 8) were added to the binding reactions to confirm that the complexes formed were specific. 17β-estradiol (E2) was included in all binding reactions. Complexes were resolved on an agarose gel and visualized by autoradiography.