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Prediction and Validation of Gene Regulatory Elements Activated During Retinoic Acid Induced Embryonic Stem Cell Differentiation
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Bcl3, an IkappaB protein, as a novel transcription coactivator of the retinoid X receptor

S Y Na1, H S Choi, J W Kim

  • 1Department of Biology, Chonnam National University, Kwangju 500-757, Korea.

The Journal of Biological Chemistry
|November 13, 1998
PubMed

Insights

The IkappaB protein Bcl3 interacts with the retinoid X receptor (RXR) and coactivates its transactivation, unlike IkappaBbeta which inhibits it. Bcl3

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Gene Regulation

Background:

  • Previous research demonstrated IkappaBbeta protein interaction with retinoid X receptor (RXR), inhibiting 9-cis-retinoic acid (RA)-dependent transactivation.
  • The role of other IkappaB proteins in modulating RXR activity remained largely unexplored.

Purpose of the Study:

  • To investigate the interaction between the IkappaB protein Bcl3 and RXR.
  • To elucidate the functional consequences of Bcl3-RXR interaction on 9-cis-RA-induced transactivation.

Main Methods:

  • Yeast two-hybrid assays to detect protein-protein interactions.
  • Glutathione S-transferase (GST) pull-down assays to confirm interactions and map binding sites.
  • Co-transfection experiments to assess functional effects on gene transactivation.

Main Results:

  • Bcl3 directly interacts with RXR through distinct N-terminal and C-terminal domains.
  • Bcl3, unlike IkappaBbeta, coactivates 9-cis-RA-induced RXR transactivation.
  • Bcl3 interacts with general transcription factors TFIIB, TBP, and TFIIA, enhancing RXR activity, particularly with SRC-1 co-expression.

Conclusions:

  • Bcl3 represents a novel coactivator of RXR-mediated transcription.
  • Distinct IkappaB proteins, such as Bcl3 and IkappaBbeta, differentially regulate RXR activity.
  • These findings highlight the complex role of IkappaB proteins in nuclear receptor signaling pathways.

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