Figure 4.

 The sequence-specific binding of ER to chromatin is not affected by estrogens or anti-estrogens. Chromatin was assembled onto pERE with the indicated components and then directly subjected to DNase I–primer extension footprinting analysis. The concentrations of ER and ligands are identical to those used in the corresponding transcriptional analyses (Fig. 3), for which the samples were subsequently diluted by a factor of 0.3. The schematic diagrams denote the locations of the EREs, TATA box, and RNA start site. (A) The binding of ER to chromatin is not affected by E₂. The positions of increased (solid arrowheads) and decreased (open arrowheads) sensitivity to DNase I are shown. (B) The binding of ER to chromatin is not affected by anti-estrogens. (C) Both ER and ER(L540Q) bind to chromatin.