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Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transformation frequencies of 4 x 10(-5) were obtained in chromosome-mediated gene transfer experiments using human cell line HeLa S3 as donor and mouse cell line A9 as recipient. This high frequency of interspecific transformation was achieved by treating the recipient cells with dimethylsulfoxide in addition to other facilitators. The high frequency of transformation correlated positively with transgenome size on the basis of both co-transfer of linked markers and chromosome analysis. The syntenic human markers glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADP(+) 1-oxidoreductase, EC 1.1.1.49) and phosphoglycerate kinase (ATP:3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) were sometimes transferred together with the selected X-linked prototrophic marker hypoxanthine phosphoribosyltransferase (IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) into murine somatic cells. Donor human chromosome material could be demonstrated cytologically in some of the transformed cell lines. Transformants exhibited various rates of loss of the human hypoxanthine phosphoribosyltransferase marker when grown under nonselective conditions. These results reveal a broader range of possible interspecific transgenome sizes than has been recognized in the past. The largest transgenomes consist of cytologically detectable donor fragments and contain syntenic markers that are not closely linked to the selected marker.
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PMID:Co-transfer of human X-linked markers into murine somatic cells via isolated metaphase chromosomes. 27 34

We produced somatic cell hybrids between HT 1080-6TG human fibrosarcoma cells and either rat white blood cells (WBC) or cells directly derived from rat spleen. Karyologic and isozyme analyses of hybrid cells indicated that they preferentially lose rat chromosomes. Hypoxanthine-aminopterine thymidine-selected hybrid clones expressing rat hypoxanthine phosphoribosyltransferase (HPRT), glucose-6-phosphate dehydrogenase (G6PD), and phosphoglycerate kinase (PGK) and containing the rat X chromosome were counterselected in a medium containing 30 micrograms/ml of 6-thioguanine. Concordant loss of the rat X chromosome and of the expression of rat HPRT and G6PD was observed in the hybrid clones.
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PMID:Segregation of rat chromosomes in somatic cell hybrids between rat cells and HT 1080 human fibrosarcoma cells. 29 42

The behaviour of human cells arrested in mitosis can be severely perturbed so as to generate numerous small minisegregants containing very few chromosomes. These cells can be separated according to size and DNA content and fused with intact cells. In this paper we describe the production and some properties of proliferating cell hybrids generated by fusion of human minisegregant cells derived from a HeLa strain with mouse A9 cells deficient in hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8). The hybrids were shown to contain up to 10 human chromosomes including a single X. Independently derived hybrid clones were quantitatively characterized and compared with the parental phenotypes with respect to HPRT. Human isozymes of each of the 3 enzymes HPRT, glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and phosphoglycerate kinase (EC 2,7.2.3) were found. Tests to evaluate both structure and function of HPRT were utilized. The specific activity of HPRT of more than 10 hybrids tested was approximately 10% that of the HeLa parent. Structural characterization of HPRT from hybrid cells as evidenced by heat inactivation and electrophoretic mobility results in a 'human-like' phenotype. Functional characterization of parental HPRT results in kinetic constants for cofactor and substrate which do not permit distinction of human and of human and mouse enzymes; HPRT from the minisegregant hybrids had normal kinetic constants. The reduced specific activity of HPRT in the hybrids is discussed in terms of the inability of the mouse environment to regulate the full expression of the human structural gene.
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PMID:Transfer of human chromosomes via human minisegregant cells into mouse cells and the quantitation of the expression of hypoxanthine phosphoribosyltransferase in the hybrids. 56 87

Evidence for derepression of the gene for hypoxanthine phosphoribosyltransferase (HPRT; IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) on the human inactive X chromosome was obtained in hybrids of mouse and human cells. The mouse cells lacked HPRT and were also deficient in adenine phosphoribosyltransferase (APRT; AMP: pyrophosphate phosphoribosyltransferase; EC2.4.2.7). The human female fibroblasts were HPRT-deficient as a consequence of a mutation on the active X but contained a normal HPRT gene on the inactive X. The two human X chromosomes were further distinguished by differences in morphology: the inactive X was morphologically normal while the active X included most of the long arm of autosome no. 1 translocated to the distal end of the X long arm. Forty-one hybrid clones were first isolated by selection for the presence of APRT; when these clones were selected for HPRT, six of them yielded derivatives having human HPRT with incidences of about 1 in 10-6 APRT-selected hybrid cells. The HPRT-positive derivatives contained a normal-appearing X chromosome indistinguishable from the inactive X of the parental human fibroblasts. The active X with the translocation was not found in any of the HPRT-positive hybrid cells. Human phosphoglycerokinase (ATP:3-phospho-D-glycerate 1-phosphotransferase. EC 2.7.2.3) and glucose-6-phosphate dehydrogenase (D-glucose 6-phosphate: NADP 1-oxidoreductase, EC 1.1.1.49), which are specified by X-chromosomal loci, were not detected in the hybrids expressing HPRT even though they contained an apparently intact X chromosome. The observations are most simply explained by the infrequent, stable derepression of inactive X chromosome segments that include the HPRT locus but not the phosphoglycerokinase and glucose-6-phosphate dehydrogenase loci.
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PMID:Localized Derepression on the Human Inactive X Chromosone in Mouse-Human Cell Hybrids. 105 21

Human genes coding for hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferase), glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49; D-glucose-6-phosphate:NADP+ 1-oxidoreductase), and phosphoglycerate kinase (PGK, EC 2.7.2.3; ATP:3-phospho-D-glycerate 1-phosphotransferase) have been assigned to specific regions on the long arm of the X chromosome by somatic cell gentic techniques. Gene assignment and linear order were determined by employing human somatic cells possessing an X/9 translocation or an X/22 translocation in man-mouse cell hybridization studies. The X/9 translocation involved the majority of the X long arm translocated to chromosome 9 and the X/22 translocation involved the distal half of the X long arm translocated to 22. In each case these rearrangements appeared to be reciprocal. Concordant segregation of X-linked enzymes and segments of the X chromosome generated by the translocations indicated assignment of the PGK gene to a proximal long arm region (q12-q22) and the HPRT and G6PD genes to the distal half (q22-qter) of the X long arm. Further evidence suggests a gene order on the X long arm of centromere-PGK-HPRT-G6PD.
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PMID:Human X-Linked genes regionally mapped utilizing X-autosome translocations and somatic cell hybrids. 105 18

We have transferred the human gene for hypoxanthine-guanine phosphoribosyltransferase (HPRT, EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferease) via isolated metaphase chromosomes from human HeLa S3 cells into murine A9 cells which lack functional murine HPRT activity, using the technique of McBride and Ozer (Proc, Nat. Acad. Sci. USA 70, 1258-1262, 1973). Three transformed clones were isolated which contained human HPRT activity as determined by electrophoretic and immunochemical assays. Twenty human isozymes other than HPRT whose genes have been assigned to 14 human chromosomes were found to be absent in our transformed clones. Moreover, the human isozymes of hlucose-6-phosphate dehydrogenase (EC 1.1.1.49; D-glucose 6-phosphate:NADP 1-oxidoreductase) and phosphoglycerate kinase (EC 2.7.2.3;ATP:3-phospho-D-glycerate 1-phosphotransferase), whose genes have been linked with the HPRT gene to the long are of the human X chromosome, were also absent. On the basis of the known linkage relationships of the three markers, we thereby suggest that the transferred piece of human genetic material is smaller than 20% of the human X chromosome or less than 1% of the human genome. This estimate assumes a normal syntenic relationship for the long arm of the X chromosome in HeLa S3 cells. In agreement with this conclusion, no human chromosomes could be detected in our transformed clones. When grown under nonselective conditions about 3% of the gene transfer cells lost the human HPRT marker per cell generation. Transformants that had lost human HPRT activity were subjected to hypoxanthine-aminopterin-thymidine selection. The frequency of revertants to the HPRT(+) phenotype was less than 1 x 10(-6), and two revertants that were obtained possessed the mouse electrophoretic phenotype. These results argue against a stable integration of the human donor genetic material into the mouse recipient genome.
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PMID:Transfer of the human gene for hypoxanthine-guanine phosphoribosyltransferase via isolated human metaphase chromosomes into mouse L-cells. 105 70

Permanent transfer of genetic information from chromosomes isolated from human diploid cells to recipient cells has been demonstrated. Human metaphase chromosomes were incubated with mouse A9 fibroblasts deficient in hypoxanthine phosphoribosyltransferase (IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) and adenine phosphoribosyltransferase (AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7). Colonies of cells containing hypoxanthine phosphoribosyltransferase appeared during growth in a selective medium. The hypoxanthine phosphoribosyltransferase gene product in four independent colonies was identified as human donor species by both gel electrophoresis and isoelectric focusing; hence these colonies did not result from reversion of ta9 parental cells. Other X-linked human genes, glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NAD(+) 1-oxidoreductase, EC 1.1.1.49) and phosphoglycerate kinase (ATP:3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3), were not expressed in these same colonies. Dissociation of expression of these X-linked genes probably results from chromosomal fragmentation during uptake, but other mechanisms have not been excluded.
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PMID:Human gene expression in rodent cells after uptake of isolated metaphase chromosomes. 105 70

To determine the clonal nature of hematopoiesis and to assess lineage involvement in patients with myelodysplastic syndromes (MDS), we used restriction fragment length polymorphisms of the X-linked genes phosphoglycerate kinase (PGK1) and hypoxanthine phosphoribosyltransferase (HPRT) and the X-linked probe M27 beta. Eleven female MDS patients heterozygous for at least one of these probes were studied: 3 with refractory anemia (RA), 2 with RA with ringed sideroblasts (RARS), 2 with chronic myelomonocytic leukemia (CMML), and 4 with RA with excess of blasts in transformation (RAEB-t). All exhibited clonal hematopoiesis as determined by Southern analysis of DNA prepared from peripheral blood (PB) and/or bone marrow (BM) cells. In three of the six patients heterozygous for the PGK1 gene, purified cell suspensions of polymorphonuclear cells (PMN), monocytes, lymphocytes, and/or T cells prepared from PB were tested. In addition, five of these patients were analyzed by a polymerase chain reaction (PCR)-based procedure as described recently. This method was slightly adapted to facilitate the analysis of cell lysates of fluorescence-activated cell sorted (FACS) monocytes, T and B lymphocytes, and natural killer (NK) cells. The outcome of Southern and PCR analysis was concordant, showing that PMN and monocytes were clonally derived, whereas circulating T and B lymphocytes and NK cells exhibited random X-chromosome inactivation compatible with a polyclonal pattern. To address the question of whether T cells are derived from unaffected progenitor cells or that their origin had antedated the onset of MDS, naive and memory T cells were analyzed separately. Both subsets showed a polyclonal pattern. However, in one patient analysis of constitutive DNA suggested a skewed methylation, and the presence of clonal lymphocytes against a background of polyclonal lymphoid cells cannot be ruled out in this patient. PCR analysis of PB and BM cells showed a nonrandom, unilateral pattern of X-inactivation, compatible with a mixture of clonally (myeloid) and polyclonally (lymphoid) derived cells. In conclusion, in some patients, MDS represents a disorder with clonal hematopoiesis restricted to cells of myeloid origin, whereas a random X-inactivation pattern is found in lymphoid cells.
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PMID:Clonal involvement of granulocytes and monocytes, but not of T and B lymphocytes and natural killer cells in patients with myelodysplasia: analysis by X-linked restriction fragment length polymorphisms and polymerase chain reaction of the phosphoglycerate kinase gene. 135 10

It is unclear whether Cushing's disease results from a primary pituitary disorder or arises in response to abnormal hypothalamic control of the pituitary gland. Clonal analysis can provide information as to whether neoplastic tissue is derived from a monoclonal proliferation of a genetically altered cell or from a polyclonal expansion of a group of cells affected by a common stimulus. We used X-linked restriction fragment length polymorphisms at the phosphoglycerate kinase, hypoxanthine phosphoribosyltransferase, and DXS255 loci in 11 women with biochemically and pathologically confirmed Cushing's disease to determine the clonal origins of corticotroph adenomas and corticotroph hyperplasia. Tumor tissue from all 10 women with morphologically and immunohistochemically confirmed ACTH-secreting pituitary microadenomas demonstrated a monoclonal pattern. Pathologically confirmed corticotroph hyperplasia in a patient with a CRH-secreting bronchial carcinoid was found to be polyclonal. We conclude that corticotroph microadenomas in Cushing's disease are monoclonal, supporting the theory that a spontaneous somatic mutation is the primary pathogenetic mechanism in this disorder. In addition, the demonstration of polyclonality in corticotroph hyperplasia implies that excess of hypothalamic hormones is an etiologic mechanism in cases of Cushing's syndrome associated with ectopic CRH-secreting tumors.
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PMID:Clonal origins of adrenocorticotropin-secreting pituitary tissue in Cushing's disease. 135 9

Dosage compensation of X-linked genes in male and female mammals is accomplished by random inactivation of one X chromosome in each female somatic cell. As a result, a transcriptionally active allele and a transcriptionally inactive allele of most X-linked genes reside within each female nucleus. To examine the mechanism responsible for maintaining this unique system of differential gene expression, we have analyzed the differential binding of regulatory proteins to the 5' region of the human hypoxanthine phosphoribosyltransferase (HPRT) gene on the active and inactive X chromosomes. Studies of DNA-protein interactions associated with the transcriptionally active and inactive HPRT alleles were carried out in intact cultured cells by in vivo footprinting by using ligation-mediated polymerase chain reaction and dimethyl sulfate. Analysis of the active allele demonstrates at least six footprinted regions, whereas no footprints were detected on the inactive allele. Of the footprints on the active allele, at least four occur over canonical GC boxes or Sp1 consensus binding sites, one is associated with a potential AP-2 binding site, and another is associated with a DNA sequence not previously reported to interact with a sequence-specific DNA-binding factor. While no footprints were observed for the HPRT gene on the inactive X chromosome, reactivation of the inactive allele with 5-azacytidine treatment restored the in vivo footprint pattern found on the active allele. Results of these experiments, in conjunction with recent studies on the X-linked human PGK-1 gene, bear implications for models of X chromosome inactivation.
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PMID:Multiple in vivo footprints are specific to the active allele of the X-linked human hypoxanthine phosphoribosyltransferase gene 5' region: implications for X chromosome inactivation. 144 69


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