Two separate NCoR (nuclear receptor corepressor) interaction domains mediate corepressor action on thyroid hormone...

Area of Science:

• Molecular Endocrinology
• Gene Regulation
• Nuclear Receptor Signaling

Background:

• Nuclear corepressor 1 (NCoR) interacts with thyroid hormone receptor (TR) in a ligand-independent manner.
• NCoR-TR binding mediates repression on thyroid hormone response elements (TREs).
• The specific roles of NCoR interaction domains in TR binding and repression on DNA remain unclear.

Purpose of the Study:

• To characterize the interactions between NCoR interaction domains and TR on DNA.
• To investigate the functional significance of NCoR interaction domains in TR-mediated gene regulation.
• To compare the binding affinities of NCoR and SMRT interaction domains for TR.

Main Methods:

• Electrophoretic mobility shift assays (EMSAs) to assess protein-DNA binding.
• Analysis of ligand-independent repression by NCoR on positive and negative TREs.
• Deletion mutagenesis of NCoR interaction domains.

Main Results:

• Both NCoR interaction domains bind TR on TREs.
• NCoR interaction domains exhibit stronger binding to TR compared to SMRT domains.
• Deletion of individual NCoR interaction domains does not abolish ligand-independent repression.
• NCoR interaction domains preferentially bind TR homodimers over TR-retinoid X receptor (RXR) heterodimers.

Conclusions:

• Either NCoR interaction domain is sufficient for mediating ligand-independent TR effects.
• NCoR interaction domains play a crucial role in TR repression, with a preference for TR homodimers.
• These findings elucidate the molecular mechanisms of NCoR-TR interaction in thyroid hormone signaling.