The oncoprotein Bcl-3 directly transactivates through kappa B motifs via association with DNA-binding p50B homodimers

Cell. 1993 Mar 12;72(5):729-39. doi: 10.1016/0092-8674(93)90401-b.


Bcl-3 is an I kappa B-related protein with ankyrin repeat motifs. Its gene is located at a site of recurrent translocations in a subset of B cell chronic lymphocytic leukemias. Bcl-3 associates tightly with p50B (NFKB2, p52) homodimers in cells, and together these proteins form a ternary complex with DNA at kappa B sites. Such an association functionally leads to a novel and potent form of transactivation through the kappa B motif: the tethering of Bcl-3 to DNA via the p50B homodimers allows Bcl-3 to transactivate directly, while p50B homodimers alone cannot. Transactivation mediated by Bcl-3 requires two cooperating domains located amino- and carboxy-terminal to the ankyrin domain. Bcl-3 is localized to the nucleus, and a Bcl-3-p50B complex is detected in certain lymphoid cells. Our data reveal a novel role for Bcl-3, distinct from that of the inhibitor I kappa B. The results have implications for tumorigenesis.

MeSH terms

  • Animals
  • B-Cell Lymphoma 3 Protein
  • Binding Sites
  • Cell Line
  • DNA / metabolism
  • Macromolecular Substances
  • NF-kappa B / metabolism*
  • Protein Precursors / metabolism*
  • Proto-Oncogene Proteins / chemistry
  • Proto-Oncogene Proteins / metabolism*
  • Trans-Activators*
  • Transcription Factors
  • Transcription, Genetic


  • B-Cell Lymphoma 3 Protein
  • BCL3 protein, human
  • Macromolecular Substances
  • NF-kappa B
  • Protein Precursors
  • Proto-Oncogene Proteins
  • Trans-Activators
  • Transcription Factors
  • p50B-p97 protein, human
  • DNA