B-cell lymphoma 3-encoded protein is a protein that in humans is encoded by the BCL3 gene.This gene is a proto-oncogene candidate. It is identified by its translocation into the immunoglobulin alpha-locus in some cases of B-cell leukemia.The protein encoded by this gene contains seven ankyrin repeats, which are most closely related to those found in I kappa B proteins.The BCL3 gene is mapped to human chromosome 19. This protein functions as a transcriptional coactivator that activates through its association with NF-kappa B homodimers. The expression of this gene can be induced by NF-kappa B, which forms a part of the autoregulatory loop that controls the nuclear residence of p50 NF-kappa B.