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

Somatic cell hybrids were constructed between BALB/c-RAG mouse cells and feline lymphoma cells by the hypoxanthine-aminopterin-thymidine selection scheme. RAG cells spontaneously produce an endogenous B-tropic type C virus. Cat-mouse hybrids preferentially segregate feline chromosomes and retain murine chromosomes-demonstrable by karyotypic and isozyme analyses. Despite the presence of the complete mouse genome, including the viral genome, virus production was diminished to 1-5% of the levels observed in RAG parents based upon particle-associated RNA-dependent DNA polymerase (reverse transcriptase) activity in the culture fluid. Thirty-seven hybrids made on four different occasions had suppressed virus levels, and no hybrids expressed parental virus levels. Reverse selection experiments on 6-thioguanine demonstrated that a restriction gene, tentatively named Bvr-1, was linked to the feline structural genes for hypoxanthine phosphoribosyltransferase (IMP:pyrophosphate phosphoribosyltransferase; EC 2.4.4.8) and glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase; EC 1.1.1.49) in cats, probably on the X-chromosome. The genetic mode of action of Bvr-1 is trans dominant in restriction of murine leukemia virus. The restriction locus results in a block late in virus maturation but prior to release, since expression of antigens for viral structural proteins and matrue budding particles is apparent on surfaces of restriced hybrid cells but not in high-speed pellets from culture fluid of restricted cells.
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PMID:Bvr-1, a restriction locus of a type C RNA virus in the feline cellular genome: identification, location, and phenotypic characterization in cat X mouse somatic cell hybrids. 6 49

De novo purine biosynthesis has been studied in lymphocyte cell lines established from Lesch-Nyhan patients deficient in hypoxanthine-guanine phosphoribosyltransferase (HGPRT), in in vitro differentiating erythroleukaemic cell lines cloned from cells charactistic of virus-induced murine leukaemia, and in mutant hamster cells deficient in amidophosphoribosyltransferase. The relationship between cellular phosphoribosylpyrophosphate (PP-ribose-P) metabolism and the activity of the enzymes which catalyse the early steps of de novo purine biosynthesis has been explored. It was found that hamster cells deficient in amidophosphoribosyltransferase did not accumulate PP-ribose-P as do HGPRT-deficient cells. In these model systems, an accelerated rate of de novo purine biosynthesis tended to be associated with an increase in cellular PP-ribose-P cotent, but decreases in this rate results from the reduction in the activity of amidophosphoribosyltransferase. Regulation of ammonia-dependent de novo purine biosynthesis was similar to that of glutamine-dependent purine biosynthesis.
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PMID:Purine biosynthesis in mutant mammalian cells. 20 59

We investigated the effect of high dose methotrexate (HDMTX) therapy on plasma hypoxanthine (Hx) and uridine (UR) concentrations in 12 children with acute lymphoblastic leukemia (ALL) or non-Hodgkin lymphoma (NHL). The initial plasma Hx level before the first administration of HDMTX (1 g/m2) was significantly higher in patients (25.5 +/- 17.5 microM) than that in healthy adult controls (4.0 +/- 1.4 microM). By 48 or 72 hours after the beginning of MTX infusion, the Hx concentration had decreased to 7.9 +/- 7.7 microM and 4.7 +/- 4.1 microM, respectively. This decrease of plasma Hx concentration after MTX infusion was also observed with the second course of HDMTX (3 g/m2) therapy. On the other hand, the plasma UR level did not change significantly. The in vitro treatment with 2 microM MTX of hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-deficient mutant cells selected from HL-60 lowered the excretion of Hx into the culture medium. These data suggest a possible new explanation of the synergism of HDMTX and 6-thiopurines, for example 6-mercaptopurine and 6-thioguanine, since plasma Hx is considered to counteract 6-thiopurine toxicity through competition at the level of HGPRT.
Leukemia 1992 Nov
PMID:Effect of high-dose methotrexate on plasma hypoxanthine and uridine levels in patients with acute leukemia or non-Hodgkin lymphoma in childhood. 143 5

A rapid decrease in expression of the oncogene c-myc has been associated with the induction of differentiation of HL-60 human leukemia cells. In this manner, the treatment of a hypoxanthine phosphoribosyltransferase (HPRT)-deficient HL-60 variant (HL-60/var) with 6-thioguanine (TG) was accompanied by lower c-myc mRNA levels. This occurred in the absence of 6-thioguanosine 5'-monophosphate (TGMP) synthesis and without alterations in cellular nucleotide pool sizes. Paradoxically, inhibition of c-myc expression in the wild type HL-60 (HL-60/wt) cell, which is only weakly induced to differentiate by TG, was 5-fold more sensitive to the thiopurine (IC50 = 35 microM). Furthermore, inosine, which blocks the formation of TGMP and enhances the extent of differentiation of HL-60/wt cells, decreased the sensitivity of c-myc expression in the HL-60/wt to TG. These actions of TG and inosine on c-myc were also observed in the human colon carcinoma cell line COLO 320, further dissociating some of the effects of TG on c-myc expression from granylocytic differentiation. The hematopoietic granulocyte-macrophage colony stimulating factor (GM-CSF) elevated c-myc expression and antagonized the actions of TG on c-myc in the HL-60 cells. GM-CSF more readily antagonized the inhibitory action of TG in the HL-60/var cell line when compared to the HL-60/wt cells, restoring c-myc levels to that of the untreated controls. Hence, TG inhibited c-myc expression by two distinct mechanisms in cells which express high levels of the oncogene: a TGMP-dependent, differentiation-independent process with an IC50 of 35 microM, and a TGMP-independent action with an IC50 of 175 microM that was associated with induction of differentiation and was reversed more readily by GM-CSF.
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PMID:Inhibition of c-myc expression in human promyelocytic leukemia and colon adenocarcinoma cells by 6-thioguanine. 170 32

We analyzed DNA from peripheral-blood and marrow cells from 12 recipients of allogeneic bone marrow transplants to determine whether monoclonal but otherwise normal hematopoiesis occurs in such patients. All patients were being treated for various forms of leukemia or lymphoma. In 10 patients, granulocytes isolated from peripheral-blood samples obtained 28 to 159 days after transplantation were polyclonal. In some, circulating T cells were isolated and also found to be polyclonal. In contrast, two patients had donor-derived monoclonal or oligoclonal hematopoiesis after transplantation. In one, DNA from circulating mononuclear cells obtained 29 days after transplantation revealed a monoclonal pattern on analysis of a restriction-fragment-length polymorphism in the phosphoglycerate kinase gene. In the other, analysis of a restriction-fragment-length polymorphism in the hypoxanthine phosphoribosyltransferase gene suggested the presence of a dominant clone in the granulocytes sampled 36 days after transplantation. When the latter patient was reassessed on day 267, the same clone of donor hematopoietic cells was still predominant and was found to include circulating T cells as well as granulocytes. We conclude that monoclonal hematopoiesis of donor origin may be observed in recipients of allogeneic bone marrow transplants, indicating that stem cells in normal adult human marrow are able to repopulate both lymphoid and myeloid compartments after transplantation.
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PMID:Clonal hematopoiesis demonstrated by X-linked DNA polymorphisms after allogeneic bone marrow transplantation. 262 34

Granulocytic maturation of HL-60 promyelocytic leukemia cells induced by dimethylsulfoxide has been shown to produce a decrease in cellular protein phosphotyrosine residues and increases in both tyrosine kinase and protein phosphotyrosine phosphatase activities (D. A. Frank and A. C. Sartorelli, Biochem. Biophys. Res. Commun., 140: 440-447, 1986). These changes have been shown to not be restricted to dimethylsulfoxide-induced differentiation, since similar changes occur in HL-60 cells initiated with retinoic acid and in HL-60 sublines resistant to dimethylsulfoxide-induced differentiation treated with the retinoid. These regulatory events are not directly coupled to growth arrest, which accompanies terminal maturation, since the anthracycline antibiotics aclacinomycin A and marcellomycin, which induce HL-60 differentiation, cause these changes in phosphotyrosine metabolism, while Adriamycin, at a level which produces an equivalent degree of growth inhibition but does not initiate the maturation of HL-60 cells, does not. Furthermore, an HL-60 subline deficient in hypoxanthine-guanine phosphoribosyltransferase, which differentiates in the presence of 6-thioguanine, produced a decrease in phosphotyrosine residues and increases in tyrosine kinase and phosphotyrosine phosphatase activities in response to the purine antimetabolite, while the parental HL-60 line, in which 6-thioguanine inhibits cellular proliferation but does not induce maturation, does not exhibit these changes. Finally, similar alterations in phosphotyrosine regulation were exhibited during anthracycline-induced differentiation of the murine myelomonocytic leukemia cell line WEHI-3B D+, supporting the concept that the phenomena measured represent a general response to inducers of the granulocytic differentiation of leukemia cells.
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PMID:Alterations in tyrosine phosphorylation during the granulocytic maturation of HL-60 leukemia cells. 282 68

Determination of cellular clonality in hematological malignancies provides fundamental information that is important in understanding the pathogenesis of these disorders. We present here an extension of one approach to accomplish this that is based on the interpretation of different methylation patterns on active and inactive X chromosomes within the region of the hypoxanthine-guanine phosphoribosyltransferase gene spanned by a restriction fragment length polymorphism. The successful application of the method to determine clonality is described for three female patients with acute nonlymphocytic leukemia.
Leukemia 1987 Mar
PMID:Determination of clonality in acute nonlymphocytic leukemia by restriction fragment length polymorphism and methylation analysis. 288 56

Defective ecotropic and amphotropic retroviral vectors containing the cDNA for human hypoxanthine phosphoribosyltransferase (HPRT) were developed for efficient gene transfer and high-level cellular expression of HPRT. Helper cell clones which produced a high viral titer were generated by a simplified method which minimizes cell culture. We used the pZIP-NeoSV(X) vector containing a human hprt cDNA. Viral titers (1 X 10(3) to 5 X 10(4)/ml) of defective SVX HPRT B, a vector containing both the hprt and neo genes, were increased 3- to 10-fold by cocultivation of the ecotropic psi 2 and amphotropic PA-12 helper cells. Higher viral titers (8 X 10(5) to 7.5 X 10(6] were obtained when nonproducer NIH 3T3 cells or psi 2 cells carrying a single copy of SVX HPRT B were either transfected or infected by Moloney leukemia virus. The SVX HPRT B defective virus partially corrected the HPRT deficiency (4 to 56% of normal) of cultured rodent and human Lesch-Nyhan cells. However, instability of HPRT expression was detected in several infected clones. In these unstable variants, both retention and loss of the SVX HPRT B sequences were observed. In the former category, cells which became HPRT- (6-thioguanine resistant [6TGr]) also became G418s, indicative of a cis-acting down regulation of expression. Both hypoxanthine-aminopterin-thymidine resistance (HATr) and G418r could be regained by counterselection in hypoxanthine-aminopterin-thymidine. In vitro mouse bone marrow experiments indicated low-level expression of the neo gene in in vitro CFU assays. Individual CFU were isolated and pooled, and the human hprt gene was shown to be expressed. These studies demonstrated the applicability of vectors like SVX HPRT B for high-titer production of defective retroviruses required for hematopoietic gene transfer and expression.
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PMID:Construction of a defective retrovirus containing the human hypoxanthine phosphoribosyltransferase cDNA and its expression in cultured cells and mouse bone marrow. 346 9

The feasibility of using retroviral gene therapy to overcome drug resistance was assessed by determining the efficiency by which a retrovirus containing the human HGPRT gene could sensitize hypoxanthine-guanine phosphoribosyltransferase (HGPRT) negative human promyelocytic leukemia cells to 6-thioguanine. A single three-hour exposure at a virus to cell ratio of 6 X 2:1 restored sensitivity to 70(+/- 18)% of the clonogenic cells. The efficacy varied as a function of virus concentration and duration of viral exposure; the time allowed for integration and expression between one and five days post-infection had little effect. Cells successfully sensitized contained a proviral insert and expressed HGPRT activity that ranged from 1 to 92% of that in the wild-type cells. The mutation rate of the inserted gene varied from the same as that of the endogenous HGPRT gene to 200-fold greater in different clones. Failure of sensitization following viral exposure was associated with absence of an integrated provirus, and clonogenic cells failing to be sensitized by one virus exposure were sensitized with approximately the same efficiency by a second viral exposure. These results demonstrate the feasibility of transferring a drug sensitivity gene to a human leukemia cell line.
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PMID:Gene therapy for thioguanine-resistant human leukemia. 347 17

1. Guanine-7-oxide is a novel purine antibiotic produced by a Streptomyces species, ATCC 39364. 2. Guanine-7-oxide is cytotoxic to murine and human leukemia cells in vitro at sub-micromolar concentrations. Murine and human carcinoma cells are much less sensitive. 3. Guanine-7-oxide has significant in vivo antitumor activity, particularly against the intraperitoneal and subcutaneous L1210 leukemia systems. 4. Guanine-7-oxide, at highly cytotoxic concentrations, has little effect on biosynthesis of RNA and DNA. 5. There is preliminary evidence for an early effect of guanine-7-oxide on cellular protein synthesis. 6. Guanine, guanosine and hypoxanthine protect cells from the cytotoxicity of guanine-7-oxide. 7. Activation of guanine-7-oxide requires the presence of the enzyme hypoxanthine-guanine phosphoribosyltransferase in the target cells. 8. Cytotoxic concentrations of guanine-7-oxide do not cause depletion of cellular guanine nucleotides during a two hr incubation period. 9. Guanine-7-oxide is converted within mouse and human cells to a metabolite with chromatographic mobility corresponding to a ribonucleoside 5'-triphosphate.
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PMID:Biochemical pharmacology and experimental chemotherapy studies with guanine-7-oxide, a novel purine antibiotic. 367 7


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