[BCL3_HUMAN] Note=A chromosomal aberration involving BCL3 may be a cause of B-cell chronic lymphocytic leukemia (B-CLL). Translocation t(14;19)(q32;q13.1) with immunoglobulin gene regions.
[BCL3_HUMAN] Contributes to the regulation of transcriptional activation of NF-kappa-B target genes. In the cytoplasm, inhibits the nuclear translocation of the NF-kappa-B p50 subunit. In the nucleus, acts as transcriptional activator that promotes transcription of NF-kappa-B target genes. Contributes to the regulation of cell proliferation (By similarity).
IkappaB proteins associate with the transcription factor NF-kappaB via their ankyrin repeat domain. Bcl-3 is an unusual IkappaB protein because it is primarily nucleoplasmic and can lead to enhanced NF-kappaB-dependent transcription, unlike the prototypical IkappaB protein IkappaBalpha, which inhibits NF-kappaB activity by retaining it in the cytoplasm. Here we report the 1.9 A crystal structure of the ankyrin repeat domain of human Bcl-3 and compare it with that of IkappaBalpha bound to NF-kappaB. The two structures are highly similar over the central ankyrin repeats but differ in the N-terminal repeat and at the C-terminus, where Bcl-3 contains a seventh repeat in place of the acidic PEST region of IkappaBalpha. Differences between the two structures suggest why Bcl-3 differs from IkappaBalpha in selectivity towards various NF-kappaB species, why Bcl-3 but not IkappaBalpha can associate with its NF-kappaB partner bound to DNA, and why two molecules of Bcl-3 but only one of IkappaBalpha can bind to its NF-kappaB partner. Comparison of the two structures thus provides an insight into the functional diversity of IkappaB proteins.
Crystal structure of the ankyrin repeat domain of Bcl-3: a unique member of the IkappaB protein family.,Michel F, Soler-Lopez M, Petosa C, Cramer P, Siebenlist U, Muller CW EMBO J. 2001 Nov 15;20(22):6180-90. PMID:11707390
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
↑ Bours V, Franzoso G, Azarenko V, Park S, Kanno T, Brown K, Siebenlist U. 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. PMID:8453667
↑ Michel F, Soler-Lopez M, Petosa C, Cramer P, Siebenlist U, Muller CW. Crystal structure of the ankyrin repeat domain of Bcl-3: a unique member of the IkappaB protein family. EMBO J. 2001 Nov 15;20(22):6180-90. PMID:11707390 doi:10.1093/emboj/20.22.6180