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The Bcl-3 oncoprotein acts as a bridging factor between NF-kappaB/Rel and nuclear co-regulators.

The proto-oncoprotein Bcl-3 is a member of the IkappaB family and is present predominantly in the nucleus. To gain insight into specific nuclear functions of Bcl-3 we have isolated proteins that interact with its ankyrin repeat domain. Using the yeast two-hybrid-system we identified four novel binding partners of Bcl-3 in addition to NF-kappaB p50 and p52, previously known to associate with Bcl-3. The novel Bcl-3 interactors Jab1, Pirin, Tip60 and Bard1 are nuclear proteins which also bind to other transcription factors including c-Jun, nuclear factor I (NFI), HIV-1 Tat or the tumor suppressor and PolII holoenzyme component Brca1, respectively. Bcl-3, p50, and either Bard1, Tip60 or Pirin are sequestered into quarternary complexes on NF-kappaB DNA binding sites, whereas Jab1 enhances p50-Bcl-3-DNA complex formation. Furthermore, the histone acetylase Tip60 enhances Bcl-3-p50 activated transcription through an NF-kappaB binding site, indicating that quarternary complexes containing Bcl-3 interactors modulate NF-kappaB driven gene expression. These data implicate Bcl-3 as an adaptor between NF-kappaB p50/p52 and other transcription regulators and suggest that its gene activation function may at least in part be due to recruitment of the Tip60 histone actetylase.

Pubmed ID: 10362352


  • Dechend R
  • Hirano F
  • Lehmann K
  • Heissmeyer V
  • Ansieau S
  • Wulczyn FG
  • Scheidereit C
  • Leutz A



Publication Data

June 3, 1999

Associated Grants


Mesh Terms

  • Acetyltransferases
  • Animals
  • Ankyrins
  • Binding Sites
  • Carrier Proteins
  • DNA-Binding Proteins
  • HeLa Cells
  • Histone Acetyltransferases
  • Humans
  • I-kappa B Proteins
  • Intracellular Signaling Peptides and Proteins
  • Mutation
  • NF-kappa B
  • NF-kappa B p50 Subunit
  • Nuclear Proteins
  • Peptide Hydrolases
  • Proteins
  • Proto-Oncogene Proteins
  • Recombinant Proteins
  • Repetitive Sequences, Amino Acid
  • Transcription Factors
  • Transcriptional Activation
  • Tumor Suppressor Proteins
  • Ubiquitin-Protein Ligases
  • Yeasts