Binding of the estrogen receptor DNA-binding domain to the estrogen response element induces DNA bending

We have used circular permutation analysis to determine whether binding of purified Xenopus laevis estrogen receptor DNA-binding domain (DBD) to a DNA fragment containing an estrogen response element (ERE) causes the DNA to bend. Gel mobility shift assays showed that DBD-DNA complexes formed with fragments containing more centrally located EREs migrated more slowly than complexes formed with fragments containing EREs near the ends of the DNA. DNA bending standards were used to determine that the degree of bending induced by binding of the DBD to an ERE was approximately 34 degrees. A 1.55-fold increase in the degree of bending was observed when two EREs were present in the DNA fragment. These in vitro studies suggest that interaction of nuclear receptors with their hormone response elements in vivo may result in an altered DNA conformation.