Progesterone receptor binding to DNA: studies by sedimentation velocity methods

Area of Science:

• Molecular Endocrinology
• Biochemistry
• Genomics

Background:

• The chicken oviduct progesterone receptor subunit A is crucial for hormone action.
• Understanding its interaction with DNA is key to deciphering gene regulation.

Purpose of the Study:

• To characterize the binding of purified chicken oviduct progesterone receptor subunit A to DNA.
• To investigate the biophysical properties and stoichiometry of these receptor-DNA complexes.

Main Methods:

• Partial purification of [3H]progesterone-labeled progesterone receptor subunit A.
• Sucrose gradient ultracentrifugation to determine sedimentation coefficients.
• Analysis of receptor-DNA complex formation using radiolabeled DNA fragments and double-label counting.

Main Results:

• Progesterone receptor subunit A binds to DNA with an apparent dissociation constant (Kdiss) between 1 and 5 nM.
• Complexes exhibit a half-life exceeding 35 minutes at 0°C.
• Increasing receptor concentration leads to increased DNA sedimentation coefficients, indicating cooperative binding and DNA compaction.

Conclusions:

• Chicken oviduct progesterone receptor subunit A forms stable complexes with DNA.
• Evidence suggests cooperative binding and significant topological changes in DNA structure upon receptor interaction.