An explanation for observed estrogen receptor binding to single-stranded estrogen-responsive element DNA

Area of Science:

• Molecular Biology
• Genetics
• Endocrinology

Background:

• Estrogen-inducible genes are regulated by estrogen response elements (EREs).
• The estrogen receptor (ER) is known to bind EREs, but the precise binding mechanism (single-stranded vs. double-stranded DNA) is debated.
• Conflicting evidence suggests ER may prefer binding single-stranded EREs.

Purpose of the Study:

• To reconcile conflicting models of estrogen receptor (ER) binding to the estrogen response element (ERE).
• To investigate the DNA structural basis for ER-ERE interactions.
• To determine the preferred binding mode of ER to EREs in vitro and in vivo.

Main Methods:

• Nuclease sensitivity assays to analyze DNA structure.
• Investigating DNA annealing properties of ERE sequences.
• Assessing ER binding to bimolecular ERE structures.

Main Results:

• Single strands of ERE DNA can anneal in an antiparallel manner to form double-stranded inverted repeats with unannealed tails.
• The extent of this DNA annealing directly correlates with ER binding efficiency.
• Both strands of the ERE sequence are capable of self-annealing for ER binding.

Conclusions:

• Estrogen receptor (ER) exclusively binds to the annealed, double-stranded form of the estrogen response element (ERE).
• This finding clarifies the mechanism of ER-ERE interaction, supporting a double-stranded binding model.
• The study reconciles previous observations by demonstrating that single-stranded EREs can form the preferred double-stranded binding structure.