title: The proto-oncogene bcl-3 encodes an I kappa B protein.
abstract: The bcl-3 gene product, overexpressed in chronic lymphocytic leukemia (CLL) patients with the translocation t(14;19), is a member of the I kappa B family. The bcl-3 protein is able to inhibit the DNA binding and trans-activation of authentic NF-kappa B heterodimers p50-p65 and p49-p65, as well as p50 and p49 homodimers. The bcl-3 protein does not inhibit either the DNA-binding activity of the Rel protein or its ability to trans-activate genes linked to the kappa B site. A human 37-kD protein (I kappa B alpha), identified previously as a member of the I kappa B family, is also unable to inhibit DNA-binding activity of the Rel protein. However, unlike bcl-3, the 37-kD (I kappa B alpha) protein has no effect on the DNA-binding activity of p50 or p49 homodimers. Two dimensional phosphotryptic peptide maps of the human bcl-3 and the human 37-kD (I kappa B alpha) proteins reveal that the phosphopeptides from the 37-kD (I kappa B alpha) protein are nested within the bcl-3 protein. Furthermore, bcl-3 antisera immunoprecipitates an in vitro-radiolabeled 37-kD (I kappa B alpha) protein. Proteins of 56 and 38 kD can be identified in HeLa cells stimulated with PMA and immunoprecipitated with bcl-3 antisera. Comparison of tryptic peptide maps of the bcl-3 protein synthesized in vitro, and p56 and p38 from HeLa cells, shows that they are all structurally related. Removal of the amino-terminal sequences of the bcl-3 protein generates a protein that inhibits the DNA binding of the p50-p65 heterodimer but, like the 37-kD (I kappa B alpha) protein, is no longer able to inhibit the binding of the p50 and p49 homodimers with kappa B DNA. We propose that the bcl-3 and 37-kD (I kappa B alpha) proteins are related and are members of the I kappa B family.
authors.affiliation: Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92186.
authors.forename: L D
authors.initials: LD
authors.lastname: Kerr
authors.forename: C S
authors.initials: CS
authors.lastname: Duckett
authors.forename: P
authors.initials: P
authors.lastname: Wamsley
authors.forename: Q
authors.initials: Q
authors.lastname: Zhang
authors.forename: P
authors.initials: P
authors.lastname: Chiao
authors.forename: G
authors.initials: G
authors.lastname: Nabel
authors.forename: T W
authors.initials: TW
authors.lastname: McKeithan
authors.forename: P A
authors.initials: PA
authors.lastname: Baeuerle
authors.forename: I M
authors.initials: IM
authors.lastname: Verma
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000081242:B-Cell Lymphoma 3 Protein; D001483:Base Sequence; D002460:Cell Line; D002645:Chickens; D004247:DNA; D004330:Drosophila; D015180:Electrophoresis, Gel, Two-Dimensional; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D011233:Precipitin Tests; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel; D014157:Transcription Factors; D014158:Transcription, Genetic
chemical_list: D000081242:B-Cell Lymphoma 3 Protein; C000631344:BCL3 protein, human; C000631345:Bcl3 protein, mouse; C000715470:MAS1 protein, human; D016328:NF-kappa B; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D020569:Proto-Oncogene Proteins c-rel; D014157:Transcription Factors; D004247:DNA