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Phosphorylation of NF-kappaB p65 at Ser468 controls its COMMD1-dependent ubiquitination and target gene-specific

Hui Geng1, Tobias Wittwer, Oliver Dittrich-Breiholz

  • 1Institute of Biochemistry, Medical Faculty, Friedrichstrasse 24, Justus-Liebig-University, D-35392 Giessen, Germany.

EMBO Reports
|March 10, 2009
PubMed

Insights

A new switch involving phosphorylation and ubiquitination regulates the NF-kappaB p65 subunit's stability. This mechanism controls the termination of NF-kappaB gene expression, particularly for genes like Icam1.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Gene Regulation

Background:

  • The nuclear factor-kappaB (NF-kappaB) transcription factor system regulates critical biological functions.
  • Effective termination mechanisms are essential for controlling NF-kappaB activity.

Purpose of the Study:

  • To identify novel regulatory mechanisms controlling the termination of NF-kappaB activity.
  • To investigate the role of post-translational modifications in regulating NF-kappaB p65 subunit stability and function.

Main Methods:

  • Phosphorylation site mutagenesis of the NF-kappaB p65 subunit (Ser468).
  • Analysis of p65 ubiquitination and proteasomal degradation.
  • Chromatin immunoprecipitation (ChIP) assays to assess promoter recruitment.
  • Investigation of protein-protein interactions involving COMMD1 and cullin 2.

Main Results:

  • Tumor necrosis factor (TNF)-induced phosphorylation of p65 at Ser468 facilitates binding of COMMD1 and cullin 2.
  • This interaction leads to p65 ubiquitination and proteasomal degradation.
  • Mutation at Ser468 impairs p65 ubiquitination and degradation.
  • Selective elimination of chromatin-bound p65 occurs at specific NF-kappaB target genes, such as Icam1.
  • Ser468-phosphorylated p65 and COMMD1 are selectively recruited to the Icam1 promoter.

Conclusions:

  • A novel phosphorylation/ubiquitination switch at Ser468 of p65 controls its stability.
  • This switch mediates the selective termination of NF-kappaB-dependent gene expression through ubiquitin/proteasome-dependent removal of p65 from chromatin.

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