Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
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

A relationship between disordered metabolism of purines and the central nervous system has been established by the Lesch-Nyhan syndrome. In this disorder a virtually complete defect in the activity of HGPRT is associated with a syndrome of severe mental retardation, choreoathetoid cerebral palsy, and bizarre, self-mutilative behavior. In patients with partial defects in HGPRT, two have had symptoms that have been labeled spinocerebellar. Neither were appreciably ataxic, and the relationship between the symptoms and the enzyme defect remains to be established. Analysis of HGPRT in members of a large kindred with spinocerebellar degeneration revealed normal levels of the enzyme. These observations suggest that a relationship between the activity of HGPRT and clinical ataxia is remote.
 ...
PMID:Ataxia and disorders of purine metabolism: defects in hypoxanthine guanine phosphoribosyl transferase and clinical ataxia. 73 27

Mutants of the Chinese hamster ovary cell derived from CHO-K1 have been selected for lack of hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) (HGPRT) without the use of a drug-resistance protocol. The procedure depends on the use of a parental strain carrying a mutation making it unable to synthetize purines and thus dependent upon exogenously added purines for growth. The standard "BUdR-visible-light" procedure is then used to select those cells which can use adenine but cannot use hypoxanthine as a purine source. These cells are shown to be thioguanine resistant, to be unable to incorporate exogenously added hypoxanthine into purine nucleotides, to complement our other adenine-specific purine auxotrophs, Ade-H and Ade-I but not to complement a cell isolated by virtue of thioguanine resistance, and to lack the activity of HGPRT. The use of such multiply marked mutants and cells related to them for further analysis of purine nucleotide biosynthesis and interconversion is discussed.
 ...
PMID:Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism: isolation, selection, and characterization of a mutant lacking hypoxanthine-guanine phosphoribosyltransferase activity by nutritional means. 80 Feb 93

Chinese hamster cells selected for resistance to 8-azaguanine following mutagenesis have hypoxanthine-guanine phosphoribosyltransferase (HGPRT; E.C. 2.4.2.8) with characteristics compatible with different mutations in the structural gene for that enzyme. Using immunopurification and SDS-polyacrylamide electrophoresis, mutants producing antigenically active forms of the enzyme can be analyzed for changes in the molecular weight of HGPRT. Enzyme subunits from mutants RJK3 and RJK39 are reduced in molecular weight by an estimated 4 and 2%, respectively. HGPRT activity is not detectable in RJK39. The enzyme from RJK3 is active but has altered substrate binding properties. Enzymes from two other mutants with altered kinetic properties, RJK44 and RJK47, have normal molecular weights. The genetic alterations of RJK44 and 47 are probably missense mutations, while RJK3 and 39 might contain either deletions or mutations causing premature peptide chain termination. Somatic cell hybridization between RJK39 and a revertant of that strain with HGPRT of normal molecular weight revealed that the revertant probably arose by intragenic mutation rather than extragenic mutation or suppression.
 ...
PMID:Forward and reverse mutations affecting the kinetics and apparent molecular weight of mammalian HGPRT. 91 45

The incorporation of [14C]thymidine and [14C]uridine into the nucleoprotein, and [14C]phenylalanine into the protein by phytohaemagglutinin (PHA) stimulated lymphocytes from a patient with the Lesch-Nyhan syndrome [hypoxanthine-guanine phosphoribosyl transferase (EC 2.4.2.8 HGPRT) deficiency] and controls, was studied over 72 hours of incubation, with and without azaserine to block de novo purine biosynthesis. No difference was observed between the values obtained for Lesch-Nyhan and control lymphocytes, when PHA-stimulated without added azaserine. The percentage reduction in the incorporation of precursors into nucleoprotein and protein after PHA stimulation in the presence of azaserine was more obvious in the lymphocytes of the patient with the Lesch-Nyhan syndrome than in the controls after the shorter incubation periods at the lower rates of synthesis. Blocking the de novo purine biosynthetic pathway, in control PHA stimulated lymphocytes, inhibited transformation, whereas loss of the purine salvage enzyme HGPRT did not have this effect. These results are compatible with the view that the brain and bone-marrow damage that occur in the Lesch-Nyhan syndrome are the result of lack of HGPRT in tissues with little de novo purine biosynthetic capability. Other tissues with both pruine biosynthetic and salvage pathways are less vulnerable to the enzyme defect. Some possible mechanisms by which HGPRT deficiency could act are discussed. We suggest that inability to increase the supply of guanylic acid (GMP) in response to a mitotic stimulus may mediate the effect of HGPRT deficiency.
 ...
PMID:Use of phytohaemagglutinin stimulated lymphocytes to study effects of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency on polynucleotide and protein synthesis in the Lesch-Nyhan syndrome. 93 18

The effectiveness of purines and purine analogues as inducers of erythroid differentiation in cultured murine erythroleukemia cells has been investigated. These cell lines have previously been shown to differentiate in vitro in response to dimethylsulfoxide (DMSO) and a number of other polar solvents. Two purine analogues, 6-thioguanine and 6-mercaptopurine, as well as the naturally occuring purine, purine, hypoxanthine, are shown to be extremely potent inducers. 6-Thioguanine is effective at a concentration of 0.06 mM, 750 fold lower than the DMSO concentration required for equivalent induction. 6-Mercaptopurine and hypoxanthine are effective inducers at a concentration of approximately 2 mM. Accumulation of globin mRNA was monitored during induction with purine inducers and shown to be similar in amount to globin mRNA levels reached in DMSO-induced cultures. Induction of differentiation by all three compounds follows a similar time course to induction with DMSO. All three compounds are potent inducers of HGPRT (hypoxanthine-guanine phosphoribosyltransferase)-negative cell lines; hence incorporation of purines into DNA is not required for induction of differentiation. Comparison of these compounds with other purines and purine analogues suggests a high degree of specificity in their interaction with a cellular target.
 ...
PMID:Induction of erythroid differentiation in vitro by purines and purine analogues. 97 85

Metabolic cooperation, the correction of the mutant phenotype in cells deficient in hypoxanthine phosphoribosyltransferase (HPRT-) by intimate contact with normal cells (HPRT+), represents a form of cell communication that is easily studied with radioautography. In the present study it was found that the formation of cell junctions needed for communication does not require protein synthesis nor is it under the immediate control of the cell nucleus. Enucleated normal cells efficiently communicate with HPRT- mutant cells. The effectiveness of enucleated cells as donors in metabolic cooperation provides evidence that it is the transfer of small molecules, nucleotide, or nucleotide derivatives that is responsible for correction of the mutant phenotype. Karyoplasts (nuclei with small amounts of cytoplasm surrounded by a plasma membrane) are unable to efficiently communicate with intact cells. The utilization of [3H]hypoxanthine by communicating mixtures of HPRT+ and HPRT- human cells is not significantly different than in the normal cells alone. Metabolic cooperation, as studied involves a redistribution of purine-containing compounds among communicating cells.
 ...
PMID:Studies on cell communication with enucleated human fibroblasts. 99 66

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.
 ...
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.
 ...
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.
 ...
PMID:Transfer of the human gene for hypoxanthine-guanine phosphoribosyltransferase via isolated human metaphase chromosomes into mouse L-cells. 105 70


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>