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Reverse Yeast Two-hybrid System to Identify Mammalian Nuclear Receptor Residues that Interact with Ligands and/or Antagonists
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Molecular determinants of the interactions between SRC-1 and LXR/RXR heterodimers

You Lee Son1, Young Chul Lee

  • 1Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, South Korea.

FEBS Letters
|August 5, 2010
PubMed

Insights

Liver X receptor (LXR) and retinoid X receptor (RXR) interactions with coactivator SRC-1 were analyzed. LXR, not RXR, directly binds SRC-1, with NR boxes 2 and 3 being key for LXR activity.

Area of Science:

  • Molecular Endocrinology
  • Nuclear Receptor Signaling
  • Lipid Metabolism

Background:

  • Liver X receptor (LXR) and retinoid X receptor (RXR) form heterodimers crucial for cholesterol and lipid metabolism.
  • Steroid receptor coactivator-1 (SRC-1) is a key coactivator protein that interacts with nuclear receptors.

Purpose of the Study:

  • To comparatively analyze the binding contributions of LXR and RXR to SRC-1.
  • To elucidate the specific roles of LXR and RXR in coactivator recruitment and transcriptional regulation.

Main Methods:

  • Comparative analysis of LXR and RXR binding to SRC-1.
  • Identification of critical NR box motifs within SRC-1.
  • In vitro binding assays to assess competitive binding interactions.

Main Results:

  • The coactivator-binding surface of LXR, but not RXR, is essential for physical and functional interaction with SRC-1.
  • RXR acts as an allosteric activator of the SRC-1-LXR interaction.
  • NR boxes 2 and 3 of SRC-1 are identified as critical binding targets for SRC-1-mediated stimulation of LXR transactivity.
  • Competitive in vitro binding of NR boxes 2 and 3 to LXR was observed.

Conclusions:

  • LXR directly interacts with SRC-1 via specific NR boxes, while RXR modulates this interaction.
  • Understanding these specific binding dynamics is crucial for deciphering LXR/RXR-mediated gene regulation in lipid metabolism.

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