Regular ArticleStructure of the Human Receptor Tyrosine Phosphatase Gamma Gene (PTPRG) and Relation to the Familial RCC t(3;8) Chromosome Translocation
Abstract
The receptor protein tyrosine phosphatase γ gene, PTPγ (locus namePTPRG), was previously mapped to chromosome region 3p14.2, within a 2- to 4-Mb region centromeric to the 3p14.2 breakpoint of the t(3;8) familial renal cell carcinoma (RCC)-associated constitutional chromosome translocation. Because of its chromosomal position, its enzymatic properties as a receptor phosphatase, which might oppose a growth activating kinase activity, its homozygous deletion in murine L cells, and its transcriptional activity in numerous normal tissues, including kidney, the PTPγ gene was an attractive tumor suppressor gene candidate for renal cell carcinoma. To determine whether the PTPγ gene was a target of loss of heterozygosity or mutation in RCCs and to determine its map position relative to the t(3;8) break at 3p14.2, we have isolated YAC and λ genomic clones for the PTPγ gene and other 3p14.2 markers and determined the relative positions of the t(3;8) break, a 3p14.2de novobreak possibly in a fragile site, and the 5′ end of the PTPγ gene. Additionally, the genomic structure, position of the proximal promotor, and intron–exon border sequences of the 30-exon ∼780-kb PTPγ gene have been determined, which will facilitate analysis of the PTPγ gene in tumors.
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Multiclonal pattern of Jaagsiekte sheep retrovirus integration sites in ovine pulmonary adenocarcinoma
2006, Virus ResearchInsertional mutagenesis and envelope (Env)-mediated oncogenesis are hypothesized mechanisms by which Jaagsiekte sheep retrovirus (JSRV) causes ovine pulmonary adenocarcinoma (OPA). Twenty-eight JSRV integration sites in lung tumors (LTs) from four sheep with OPA were cloned and sequenced by a multiple step gene walking technique. Using nested PCR, clonal expansion of these integration sites could be detected, if at all, only in the localized regions of LT from which the integration sites were derived. One sheep had a viral integration site in a sequence with 85 and 81% identity, respectively, over 100 bp to exon 2 of the human and mouse receptor protein tyrosine phosphatase γ genes. Clonal integration of Jaagsiekte sheep retrovirus in this gene was demonstrated by nested PCR and Southern blot hybridization in the DNA sample from which the integration site was cloned, but not in other LT or kidney DNA samples from the same sheep. OPA may develop from multiple independent oncogenic events and a role for insertional mutagenesis cannot be ruled out.
Tyrosine kinases and phosphatases are regulators of the steady-state levels of phosphotyrosine proteins and, in this way, are key players in determining the functional state of the cell. As a unique member of the protein tyrosine phosphatase (PTP) superfamily, osteotesticular PTP (OST-PTP) is a receptor protein whose expression is highly regulated during osteoblast differentiation and in response to modulators of bone remodeling such as parathyroid hormone and vitamin D3. To explore the molecular mechanisms and signaling pathways important in the regulation of this gene, we characterized the structural organization of the mouse OST-PTP cDNA and gene and determined its chromosomal localization. The mouse cDNA is ∼5.5 kb including 5.1 kb of coding sequence, 315 bp 5′ UTR and 102 bp 3′ UTR. It is expressed as a single ∼5.8 kb transcript in day 8 differentiated MC3T3 osteoblasts. Although highly homologous to the rat OST-PTP cDNA, the mouse cDNA possesses a 74 bp insert in the 5′ UTR which contains several potential transcription factor binding sites such as AP-2 and NFκB. The mouse OST-PTP (mOST-PTP) gene is a single copy gene encompassing 35 exons and spanning only 20.65 kb. As such, it is the smallest gene of the characterized receptor PTP genes. This is due to the lack of large introns and the conserved spatial organization of exons which encode specific protein motifs in the mOST-PTP molecule. Sequence analysis of the putative mOST-PTP promoter revealed basal elements as well as many potential cis-acting regulatory elements with relevance to gene regulation in bone. Of particular interest is the single osteoblast specific element known as osteocalcin specific element 2 (OSE2) found at position −1867, as well as numerous VDRE and NFκB sites found throughout the promoter and the 5′ UTR. Fluorescence in situ hybridization studies have shown that mOST-PTP localizes to mouse chromosome 1, region F–G which is syntenic to the segment of human chromosome 1q32–33. This characterization of the mOST-PTP cDNA and gene will facilitate future experiments exploring the mechanisms of regulation of this phosphatase during osteogenesis.
Reduced expression of protein tyrosine phosphatase gamma in lung and ovarian tumors
1999, Cancer LettersBased on LOH studies protein tyrosine phosphataseγ (PTPγ) has been suggested as a candidate tumor suppressor gene involved in the oncogenesis of lung and renal cancers. In order to assess the involvement of PTPγ in tumor development we developed a PTPγ-specific monoclonal antibody (γTL1) (IgM isotype) by immunization with a synthetic peptide of 15 amino acids corresponding to the amino acid sequence nos. 1423–1438 just outside the phosphatase domain-II. In line with the fact that the antibody was raised to an intracellular domain of the PTPγ molecule the antibody labeled the cell membrane of fixed cells but did not stain the outside of the cell membrane in the immunofluorescence assay. The Mab γTL1 recognized a full-length baculovirus recombinant PTPγ protein of 185 kDa, in addition to putative cleavage products of 120 kDa, 114/110 kDa and 80 kDa, on Western blots of lysates of PTPγ-gene transfected Sf9 insect cells but not of tumor cell lysates. Based on immunoperoxidase and immunofluorescence assays on cryostat sections, however, PTPγ was expressed in more than 90% of both normal, human tissue samples and in the (non-) tumor cells of carcinoma samples. However, PTPγ was not found in 28% of the overall lung tumor samples, i.e. in 50% of the lung adenocarcinoma samples, while the expression was weak and heterogeneous in 71% of squamous lung cell carcinomas. PTPγ was not suppressed in the normal cells between the lung carcinoma cells. The presence of PTPγ, assayed by immunofluorescence in lung tumor cell lines (H69, H128, H82, C3) was confirmed by RT–PCR assay. Interestingly, the 90% expression score of PTPγ protein in normal ovarian tissue samples was reduced dramatically to 44 and 38% in both the non-tumorous and tumorous cells, respectively, in ovarian tumor samples. PTPγ was absent in the HT29 human colon carcinoma cell line both by immunofluorescence and RT–PCR assay. In summary, we have developed a PTPγ-specific monoclonal antibody, that demonstrated that the expression of PTPγ is severely reduced (>50%) in lung tumors and ovarian tumors.
Identification of a 700-kb region of common allelic loss in chromosome bands 3p14.3-p21.1 in Human renal cell carcinoma
1998, Cancer Genetics and CytogeneticsThe short arm of chromosome 3 is considered to harbor one or more of the tumor suppressor genes taking part in the genesis of renal cell carcinoma (RCC). To define the localization of such putative tumor suppressor gene(s), we studied specific allelic loss on chromosome 3p by using 84 samples of RCC with nine microsatellite markers. We defined two commonly deleted regions in 3p14.3–p21.2: (1) region A, a 2-cM region between D3S1313 and D3S1592, and (2) region B, a 2-cM region between D3S1581 and D3S1289. The most frequent loss of heterozygosity was observed at D3S1067 (33 of 59, 55.9%), which is within region A. We further focused on region A and constructed a yeast artificial chromosome (YAC) contig and found that one YAC clone, which was 700-kb in size, harbored the entire region A. Using cosmid clones isolated from this contig, we also performed fluorescence in situ hybridization analysis and found that two of the tumors were homozygously deleted in this region. Our results strongly suggest the existence of a tumor suppressor gene in this region.
Protein Tyrosine Phosphatase Receptor Gamma as Potential Therapeutic Target for Chronic Myeloid Leukemia Patients
2022, Cancer ControlGene Expression Landscape of Chronic Myeloid Leukemia K562 Cells Overexpressing the Tumor Suppressor Gene PTPRG
2022, International Journal of Molecular Sciences