Bcl-3, a member of the I kappa B proteins, has distinct specificity towards the Rel family of proteins.
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.
Inoue
J
J
Department of Experimental Pathology, Cancer Institute, Tokyo, Japan.
Takahara
T
T
Akizawa
T
T
Hino
O
O
D000081242:B-Cell Lymphoma 3 Protein; D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D020569:Proto-Oncogene Proteins c-rel; D014157:Transcription Factors; D014158:Transcription, Genetic
D000081242:B-Cell Lymphoma 3 Protein; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D020569:Proto-Oncogene Proteins c-rel; D014157:Transcription Factors; D004247:DNA