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Diverse effects of BCL3 phosphorylation on its modulation of NF-kappaB p52 homodimer binding to DNA

D L Bundy1, T W McKeithan

  • 1Departments of Pathology and of Radiation and Cellular Oncology, University of Chicago, Chicago, Illinois 60637, USA.

The Journal of Biological Chemistry
|January 31, 1998
PubMed

Insights

BCL3 protein

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • Nuclear factor-kappa B (NF-kappaB) transcription factors regulate gene expression.
  • IkappaB proteins modulate NF-kappaB activity and localization.
  • BCL3 is a unique nuclear IkappaB protein with complex regulatory functions.

Purpose of the Study:

  • To investigate the role of BCL3 in regulating NF-kappaB p52 homodimer DNA binding.
  • To determine how BCL3 phosphorylation and concentration affect its interaction with p52.
  • To elucidate the mechanisms by which BCL3 modulates NF-kappaB-dependent transcription.

Main Methods:

  • Gel shift analysis to assess DNA-binding activity.
  • Tagged protein and tagged DNA coprecipitation to study complex formation.
  • Analysis of BCL3 phosphoforms and their interactions with p52 homodimers.

Main Results:

  • BCL3 forms a kappaB-binding complex with p52 homodimers at intermediate ratios, dependent on BCL3 phosphorylation.
  • At low BCL3/p52 ratios, BCL3 enhances p52 homodimer binding to nonconsensus DNA sites.
  • At high BCL3/p52 ratios, BCL3 forms an inhibitory complex with p52 homodimers.

Conclusions:

  • BCL3's function in regulating NF-kappaB p52 homodimer binding is concentration-dependent.
  • BCL3 phosphorylation is critical for its ability to modulate p52 complex formation and DNA binding.
  • These findings suggest that BCL3 phosphorylation influences NF-kappaB-dependent transcription in vivo.

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