Bcl-3, a member of the I kappa B proteins, has distinct specificity towards the Rel family of proteins

Oncogene. 1993 Aug;8(8):2067-73.


Expression of the bcl-3 gene is demonstrated to be elevated in some B-cell chronic lymphocytic leukemias with a chromosomal translocation, t(14;19)(q32;q13.1). Bcl-3 protein has seven tandem ankyrin repeats that are also found in I kappa B proteins, inhibitors of Rel/NF kappa B transcription factors. In this paper, we demonstrate that Bcl-3 is a member of I kappa B family of proteins with a novel specificity. Bcl-3 preferentially associates with the p50 of NF kappa B, and the nuclear localization signal of p50 is required for this association. Bcl-3 inhibits the DNA-binding activity of p50 homodimers but not that of p50-p65 heterodimers. Transient transfection experiments revealed that appropriate expression of Bcl-3 results in inhibition of the function of p50 homodimers but not that of p50-p65 heterodimers, whereas pp40 and I kappa B gamma inhibit the function of both p50 homodimers and p50-p65 heterodimers. These studies suggest that Bcl-3 could modulate the transcription in a way different from pp40 and I kappa B gamma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • B-Cell Lymphoma 3 Protein
  • Base Sequence
  • DNA / metabolism
  • Molecular Sequence Data
  • NF-kappa B / physiology*
  • Proto-Oncogene Proteins / physiology*
  • Proto-Oncogene Proteins c-rel
  • Transcription Factors
  • Transcription, Genetic


  • B-Cell Lymphoma 3 Protein
  • NF-kappa B
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-rel
  • Transcription Factors
  • DNA