Relationship between estrogen structure and conformational changes in estrogen receptor/DNA complexes

Area of Science:

• Molecular Endocrinology
• Structural Biology
• Genomics

Background:

• Estrogen receptor (ER) plays a crucial role in regulating gene expression.
• Estrogen response elements (EREs) are specific DNA sequences that bind to ER.
• Understanding ER-DNA complex conformation is key to deciphering gene regulation.

Purpose of the Study:

• To investigate how estrogen structure affects the conformation of the ER-ERE complex.
• To determine if ligand-induced conformational changes correlate with binding affinity or transcriptional activity.
• To identify specific structural features of estrogens critical for ER-ERE complex mobility.

Main Methods:

• Gel mobility shift assay using MCF-7 cell extracts.
• Characterization of ER-containing complexes using anti-ER antibodies.
• Analysis of ER-ERE complex mobility in the presence of various estrogen analogs and an antiestrogen.

Main Results:

• Three distinct complexes formed with ERE; only one contained ER.
• Estradiol (E2) and certain estrogen analogs increased ER-ERE complex mobility.
• The antiestrogen ICI 164,384 decreased mobility and blocked E2's effect.
• Ligand-induced mobility changes were not directly related to binding affinity or gene activation capacity.
• Specific hydroxyl group positions on the estratriene nucleus influenced ER-ERE complex mobility.

Conclusions:

• Estrogen structure is a critical determinant of ER-ERE complex conformation.
• Conformational changes detected by gel shift assays are mediated by specific estrogen structural features.
• These structural requirements for altered gel mobility differ from those essential for transcriptional activation.