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ABSTRACT: The brk gene encodes a non-receptor tyrosine kinase that has been found to be overexpressed in approximately two thirds of breast tumours. Using a yeast two-hybrid based screen, we have cloned cDNAs encoding a novel protein, BKS, that is a substrate for the kinase activity of BRK and has the characteristics of an adaptor protein. BKS possesses an N-terminal PH-like domain followed by an SH2-like domain. In co-transfection experiments, high levels of phosphotyrosine were observed on BKS and BRK was found to be associated with BKS, both of which were dependent on the catalytic activity of BRK. The phosphorylation of and association with BKS by BRK was also dependent on the SH2-like domain present within BKS. In addition, BKS recruited an unidentified 100 kDa protein that was also phosphorylated on tyrosine residues in the presence of BRK. We have determined that the BKS protein is expressed in most adult human tissues. Oncogene (2000) 19, 4273 - 4282
Oncogene 09/2000; 19(37):4273-82. · 6.37 Impact Factor
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ABSTRACT: The brk gene encodes a non-receptor protein tyrosine kinase that consists of single SH3, SH2 and catalytic domains. Although BRK shows strongest sequence similarity to members of the SRC family of PTKs, there are several key structural and regulatory differences that place it on its own amongst non-receptor PTKs. In this study we have isolated genomic DNA clones corresponding to the human brk locus and used these to determine the intron-exon structure of the brk gene. The genomic structure of brk consists of 8 exons, whose boundaries are distinct from other non-receptor PTK family members, again indicating a structural and functional divergence. Alternate splicing of the primary brk transcript generates a distinct mRNA which encodes a truncated protein consisting of an SH3 domain and a novel C-terminal proline rich sequence. Using an antiserum raised to the SH3 domain, we have demonstrated that the product of this alternate brk transcript is expressed in the human breast tumour cell line T-47D. We have previously reported that expression of a tumour derived brk cDNA in mouse embryonic fibroblasts and human mammary epithelial cells supports anchorage independent growth, and in the latter potentiates the mitogenic response to epidermal growth factor. The protein encoded by the genomic sequence derived from normal human tissue is identical to that encoded by the tumour derived cDNA, and therefore the altered growth regulation is not associated with mutations within brk. In addition, we have identified a 5' genomic region that has promoter activity. The brk gene has been assigned to chromosome 20q 13.3 [corrected] using fluorescence in situ hybridisation (FISH).
Oncogene 10/1997; 15(12):1497-502. · 6.37 Impact Factor
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ABSTRACT: brk (breast tumor kinase) shows homology to the src family of non-receptor protein-tyrosine kinases and is expressed in breast carcinomas. In order to investigate the role of brk in breast tumor development, we have examined the growth and transformation properties of human mammary epithelial cells engineered to overexpress Brk. Interestingly, like c-Src, overexpression of Brk leads to sensitization to EGF, and also results in a partially transformed phenotype. Further investigation of the latter activity was attempted by mutational analysis, targeting key residues known to affect tyrosine kinase activity in Src-like kinases. Mutation of amino acid residue Lys-219 to Met, by analogy to Src, abolished both kinase activity and transformation capacity. Mutation of amino acid residue Tyr-447 to Phe, however, resulted in a decrease in transforming potential without affecting kinase activity. These results suggest that while Src and Brk share some functional properties, they act differently during transformation. These differences are discussed in the context of the mechanisms underlying breast cancer development.
Journal of Biological Chemistry 12/1996; 271(48):30956-63. · 4.77 Impact Factor
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ABSTRACT: We have isolated cDNAs from normal human breast tissue and breast tumour cells that encode a protein (pez) with features of a novel non-receptor tyrosine phosphatase possessing N-terminal sequence homology to the ezrin-band 4.1-merlin-radixin protein family. Northern blot analysis indicates that pez is expressed in a variety of human tissues including kidney, skeletal muscle, lung and placenta. Fluorescence in situ hybridization has mapped pez to chromosome 1 region q32.2-41. Sequence identity to a characterized polymorphic marker confirms this localization.
Biochemical and Biophysical Research Communications 05/1995; 209(3):959-65. · 2.48 Impact Factor
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ABSTRACT: Using a reverse transcriptase-polymerase chain reaction based differential screening procedure, we have identified the discoidin domain receptor as a protein tyrosine kinase that is expressed in lymph nodes containing breast tumour metastases. By Northern blotting and in situ hybridisation we have demonstrated the expression of the discoidin domain receptor in human primary breast tumour samples, metastasis-containing lymph nodes and a number of normal tissues. Direct comparison of malignant breast and adjacent normal epithelial tissue revealed over expression in the tumour cells.
Oncogene 03/1995; 10(3):569-75. · 6.37 Impact Factor
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Oncogene 01/1995; 10:569-575. · 6.37 Impact Factor
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ABSTRACT: Using a polymerase chain reaction based differential screening approach, we have isolated and characterised a cDNA from a human metastatic breast tumour representing a novel protein tyrosine kinase (brk). Sequencing of brk cDNAs isolated from T-47D and MCF-7 human breast tumour cell lines indicate that they encode a protein with the features of a novel nonreceptor tyrosine kinase, including amino terminal SH3 and SH2 domains. When synthesised in recombinant baculovirus and bacterial expression systems, brk protein products are capable of autophosphorylation on tyrosine residues. Initial expression studies have detected low levels of brk transcripts in some human breast tumours and breast tumour cell lines, but not in normal breast tissue.
Oncogene 09/1994; 9(8):2383-90. · 6.37 Impact Factor
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ABSTRACT: We have isolated cDNAs from normal human breast tissue and breast tumour cells that encode a protein () with features of a novel non-receptor tyrosine phosphatase possessing N-terminal sequence homology to the ezrin-band 4.1-merlin-radixin protein family. Northern blot analysis indicates that is expressed in a variety of human tissues including kidney, skeletal muscle, lung and placenta. Fluorescence hybridization has mapped to chromosome 1 region q32.2-41. Sequence identity to a characterized polymorphic marker confirms this localization.
Biochemical and Biophysical Research Communications.
