Structural mechanism underlying variations in DNA binding by the androgen receptor

Area of Science:

• Molecular biology
• Structural biology
• Genetics

Background:

• The androgen receptor (AR) is a crucial transcription factor regulating gene expression.
• AR binds to specific DNA sequences known as androgen response elements (AREs).
• Understanding AR-DNA interactions is vital for comprehending androgen-mediated processes and diseases like androgen insensitivity.

Purpose of the Study:

• To elucidate the structural basis of human AR DNA binding domain (DBD) dimerization on natural AREs.
• To investigate the impact of androgen insensitivity mutations on AR structure, DNA binding, and dimerization.
• To characterize the binding affinity and cooperative binding mechanisms of AR DBD to different DNA motifs.

Main Methods:

• X-ray crystallography to determine AR DBD-DNA complex structures at 2.05 Å and 2.25 Å.
• BioLayer Interferometry (BLI) to measure AR DBD binding affinity to AREs.
• Molecular Dynamics (MD) simulations to validate binding affinities and analyze interactions.

Main Results:

• Reported structures of human AR DBD bound to C3 and MTV AREs in head-to-head dimer conformations.
• Demonstrated that high affinity binding of the first DBD to the canonical 5'-AGAACA-3' motif promotes cooperative binding of the second DBD.
• Identified distinct interactions of AR DBD monomers with canonical and non-canonical hexanucleotides, influenced by DNA occupancy and protein-protein interactions.

Conclusions:

• The study provides structural insights into AR DBD dimerization and DNA recognition.
• Findings explain how AR mutations affect DNA binding and dimerization, potentially leading to androgen insensitivity.
• The observed cooperative binding mechanism has functional implications for AR-mediated transcription regulation.