title: A novel transcriptional suppressor located within a downstream intron of the BCR gene.
abstract: A reciprocal translocation between chromosomes 9 and 22 creates the Philadelphia (Ph1) chromosome in chronic myelogenous leukemia. This translocation results in the fusion of the ABL and the BCR genes to form a BCR/ABL fusion gene, the product of which has a greatly increased protein tyrosine kinase activity in comparison with the normal ABL protein. The chromosome 22 translocation breakpoints are concentrated within a 5.8-kilobase region named the major break-point cluster region (Mbcr). Gel mobility shift and DNase I footprinting assays have defined binding sites for three proteins, BIF 1-3 (BCR intron factors 1-3), lying within a 427-base pair fragment of the Mbcr. This 427-base pair fragment functions as a transcriptional silencer with both the BCR as well as a heterologous promoter. The silencing is position- and orientation-independent. The transcriptional effects are greatest in chronic myelogenous leukemia cells, decreased in HeLa and B-cells, and absent in T-lymphocytes. Gel mobility shift assays show a corresponding difference in pattern when the T-lymphocyte nuclear extract is compared with other cell lines. The Mbcr appears to contain a novel group of transcriptional silencers that share a common binding motif with a recently described suppressor in the mouse Adh-1 gene.
authors.affiliation: Department of Medicine, Indiana University, Indianapolis 46202-5121.
authors.forename: M J
authors.initials: MJ
authors.lastname: Stewart
authors.forename: G
authors.initials: G
authors.lastname: Cox
authors.forename: A
authors.initials: A
authors.lastname: Reifel-Miller
authors.forename: S Y
authors.initials: SY
authors.lastname: Kim
authors.forename: C A
authors.initials: CA
authors.lastname: Westbrook
authors.forename: D S
authors.initials: DS
authors.lastname: Leibowitz
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D016044:Fusion Proteins, bcr-abl / Q000235:genetics; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051562:Proto-Oncogene Proteins c-bcr; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: D011518:Proto-Oncogene Proteins; D004247:DNA; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; C496613:BCR protein, human; D051562:Proto-Oncogene Proteins c-bcr