Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have developed a method for the direct analysis of a hypoxanthine-guanine phosphoribosyltransferase (HPRT) allele associated with a deficiency of enzyme activity and an early onset of gout. The functionally abnormal enzyme coded for by this mutant allele (HPRTToronto) differs from the normal enzyme by an arginine-to-glycine substitution at position 50. A single base change in the codon for arginine 50 can explain this substitution. Direct analysis of this point mutation is based on the observation that it abolishes a Taq I recognition site in HPRT DNA. As predicted, DNA from individuals with the HPRTToronto allele exhibited an abnormal restriction pattern when digested with Taq I and probed with HPRT complimentary DNA: a normal 2.0-kb fragment is replaced by a 4.0-kb fragment. The 4.0/2.0-kb restriction fragment variation was used to detect the HPRTToronto allele in a heterozygote that was otherwise normal with respect to the classical techniques used to diagnose heterozygosity in HPRT deficiency.
J Clin Invest 1983 Sep
PMID:Human hypoxanthine-guanine phosphoribosyltransferase. Detection of a mutant allele by restriction endonuclease analysis. 630 10

The effect of diethylstilbestrol (DES) on sister chromatid exchange (SCE) induction was measured in four cell lines to determine whether metabolic activation of DES is a factor in its genotoxic potential. Two of these, cell lines derived from a human hepatoblastoma (HepG2-GW) and a rat hepatoma (H4-AG), have been shown previously in our laboratory to be capable of metabolizing several procarcinogens to their active forms. DES, in a dose range of 1 X 10(-8) M to 1 X 10(-5) M, increased SCE frequencies by 50 to 60% in both the rat and human hepatoma lines but had no effect on SCE induction in Chinese hamster lung fibroblasts (V79-GW) or human diploid skin fibroblasts (MGH 2C-GW), both of which are nonmetabolizing cell lines. Furthermore, pretreatment of the responsive cell lines (H4-AG and HepG2-GW) with indomethacin, an inhibitor of prostaglandin synthetase-mediated metabolism of DES, effectively prevented the induction of SCE by DES. DES failed to increase the frequency of hypoxanthine-guanine phosphoribosyltransferase locus mutants in H4-AG cells, over a dose range which induced SCE. These observations suggest that DES induces SCE but does not induce gene mutation. These data strongly support growing evidence that metabolic activation of DES may be an important factor in its genotoxic and carcinogenic mechanisms.
Cancer Res 1984 Sep
PMID:Induction of sister chromatid exchange by diethylstilbestrol in metabolically competent hepatoma cell lines but not in fibroblasts. 633 58

As a first step in the development of a multiple-marker, mammalian cell mutagenesis assay system, we have isolated a Chinese hamster ovary (CHO) cell line that is heterozygous for both the adenine phosphoribosyltransferase (aprt) and thymidine kinase (tk) loci. Presumptive aprt+/- heterozygotes with intermediate levels of APRT activity were selected from unmutagenized CHO cell populations on the basis of resistance to low concentrations of the adenine analog, 8-azaadenine. a functional aprt+/ heterozygote with approximately 50% wild-type APRT activity was subsequently used to derive sublines that were also heterozygous for the tk locus. Biochemical and genetic characterization of one such subline, CHO-AT3-2, indicated that it was indeed heterozygous at both the aprt and tk loci. CHO-AT3-2 cells permitted single-step selection of mutants resistant for 8-azaadenine or 5-fluorodeoxyuridine, allowing quantitation and direct comparison of mutation induction at the autosomal aprt or tk loci, as well as in the gene involved in ouabain resistance or at the X-linked, hypoxanthine--guanine phosphoribosyltransferase (hgprt) locus. Significant dose-dependent increases in mutation frequency were observed for all 4 genetic markers after treatment of CHO-AT3-2 cells with ethyl methanesulfonate.
Mutat Res 1980 Sep
PMID:Mutagenicity testing in mammalian cells. I. Derivation of a Chinese hamster ovary cell line heterozygous for the adenine phosphoribosyltransferase and thymidine kinase loci. 644 63

The transplantable murine Dunn osteosarcoma has no detectable hypoxanthine:guanine phosphoribosyltransferase (EC 2.4.2.8) activity. This was established from the tumors directly and from tissue culture cell lines derived from the tumor using a variety of assays: e.g., no [3H]hypoxanthine uptake into tumor or tissue culture cells, no conversion of [3H]hypoxanthine to [3H]IMP by cell extracts from tumors or tissue culture cells, no growth of tissue culture cells in hypoxanthine:aminopterin:thymidine medium, and normal growth of these cells in 10 microM 6-mercaptopurine. Ten human osteosarcomas have been assayed, and two have no apparent hypoxanthine:guanine phosphoribosyltransferase enzyme activity. After high-dose methotrexate treatment in vivo, murine tumors could be selectively killed and normal tissues could be spared by using a rescue regimen of hypoxanthine-thymidine-allopurinol.
Cancer Res 1983 Sep
PMID:Absence of hypoxanthine:guanine phosphoribosyltransferase activity in murine Dunn osteosarcoma. 657 63

A novel mechanism of resistance to the antileukemic agent 6-thioguanine (TGua) was demonstrated in a clone (TGuo-30-2) derived from HL-60 human acute promyelocytic leukemia cells. The clone was isolated by prescreening mutagenized HL-60 cells in hypoxanthine-amethopterin-thymidine medium, followed by selection with 6-thioguanosine. TGuo-30-2 cells were cross-resistant to TGua and beta-2'-deoxythioguanosine. TGuo-30-2 cells exhibited a marked decrease in the capacity to accumulate intracellular TGua nucleotides after treatment with TGua. The decrease in accumulation was not caused by a defect in transport, a lack or alteration of hypoxanthine-guanine phosphoribosyltransferase activity, or enhanced degradation of TGua nucleotides but appeared to be due to the maintenance of a lowered level of 5-phosphoribosyl 1-pyrophosphate (PRPP) in the resistant variant, which corresponded to 20% of the parental concentration. Despite the decrease in PRPP levels, incorporation of glycine into purine nucleotides was greater in TGuo-30-2 than in parental cells. Measurement of PRPP amidotransferase activity using cell homogenates revealed altered kinetics for the enzyme from TGuo-30-2 cells, which included significant loss of sensitivity to feedback inhibition by 6-thioguanosine 5'-phosphate and greater catalytic activity at low concentrations of PRPP.
Cancer Res 1984 Sep
PMID:Altered 5-phosphoribosyl 1-pyrophosphate amidotransferase activity in 6-thioguanine-resistant HL-60 human acute promyelocytic leukemia cells. 658 43

Delayed growth arrest was observed in HL-60 acute promyelocytic leukemia cells after exposure to 6-thioguanine (TG). This growth arrest occurred in both wild-type HL-60 cells exposed to 2 microM TG and an HL-60 clone lacking hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity at a 500-fold higher concentration of drug. Both cell lines continued replication during an initial 4-day period of exposure to TG; however, upon removal of the purine antimetabolite and reincubation in fresh medium in the absence of drug, no further increase in cell number was observed over the next 4 days. Extensive differentiation, as measured by the reduction of nitroblue tetrazolium, occurred in TG-treated, HL-60 HGPRT-negative cells, whereas no significant increase in the number of nitroblue tetrazolium-positive cells was observed in wild-type HL-60 cells exposed to the purinethiol. Thus, termination of proliferation in wild-type cells appeared to be an expression of cytotoxicity, while in the HGPRT-negative clone, cell replication was apparently terminated by conversion of cells to end-stage forms with a mature phenotype. In support of this conclusion, differences occurred in the stage of the cell cycle arrest, determined on Day 6 after exposure to TG. Approximately 85% of parental HL-60 cells treated with TG were present in the S and G2 + M phases of the cell cycle, with the greatest proportional change from untreated controls being in the G2-M phase (i.e., a 63% increase over untreated controls). In contrast, HL-60 HGPRT-negative cells treated with TG accumulated in G1, with 68% of the population located in this phase (i.e., an 80% increase compared to controls), as might be expected for a differentiated population. Dimethyl sulfoxide, which produced differentiation in both parental HL-60 and HL-60 HGPRT-negative cells, was used as a positive control. Both cell lines responded identically to dimethyl sulfoxide, with growth arrest being due at least in part to differentiation, which corresponded to an increase in G1 cells.
Cancer Res 1984 Sep
PMID:Cell cycle events associated with the termination of proliferation by cytotoxic and differentiation-inducing actions of 6-thioguanine on HL-60 cells. 658 46

Inactivation of the X chromosome during mammalian spermatogenesis has been postulated to occur by the same mechanism that controls female somatic X chromosome inactivation. We have used DNA-mediated transformation of HPRT- cells to test this idea, because it has been shown previously that inactive X chromosome DNA from somatic cells will not transform HPRT- cells. Isolated DNA from the mature sperm of five mammals (human, mouse, horse, bull, rabbit) were all capable of HPRT transformation, and transformants were confirmed electrophoretically. Measures were taken to ensure that the transformation frequencies observed could not be due to somatic contamination. The positive HPRT transformation result indicates that mature sperm X chromosomal DNA is not modified in the same manner as that of female inactive X chromosomal DNA. Since there is evidence for methylation of the somatic inactive X chromosome, it is possible that methylation, at least for the genes studied, is not involved in sperm X chromosome inactivation.
Somatic Cell Genet 1983 Sep
PMID:Transformation of Hprt gene with sperm DNA. 668 98

Chloramphenicol-resistant (CAPr) reconstituted cells and cybrids were isolated by fusion of karyoplasts (or intact cells) of mouse amelanotic melanoma B16 cells with cytoplasts of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) -deficient, CAPr rat myoblastic cells, L6TG.CAPr, and double selection in HAT medium containing CAP. Reconstituted cells or cybrids exhibited unique cellular arrangement, and about one third of the isolated clones expressed high tyrosinase activity and marked melanin synthesis, although the parental mouse cells expressed low tyrosinase activity and the parental rat cells did not express tyrosinase activity. These phenotypic changes have been stable for more than a year. The phenotypic reversions of these clonal cells were induced by treatment with a tumor promoter. There were changes in the morphology of the treated cells to that of the mouse B16 cells and extinction of tyrosinase activity and melanin synthesis in pigmented clonal cells. These phenotypic changes and reversions induced by a promoter were repeatedly reversible.
Somatic Cell Genet 1982 Sep
PMID:Induction of supermelanin synthesis and morphological changes in interspecific reconstituted cells and its reversal by tumor promoter. 681 81

We have examined contact-mediated intercellular communication by measuring the transfer of thioguanine sensitivity to a hypoxanthine phosphoribosyltransferase (EC 2.4.2.8)-negative clone (66cl-4) selected from one subline isolated previously from a spontaneously arising mammary tumor of a BALB/cfC3H mouse. We tested other sublines from the same tumor and unrelated cell types for their ability to serve as 6-thioguanine nucleotide donors to 66cl-4 cells. The degree of communication, measured by the number of donor cells required to reduce the number of thioguanine-resistant colonies, varied with the donor cell type. The 66cl-4 line communicated with the parent cell line from which the thioguanine-resistant cell was selected and with other sublines from the parent tumor, with some unrelated tumor cells, and with some nonneoplastic cells (3T3, hamster kidney and lung fibroblasts, and mouse mammary epithelial cells). There was a quantitative difference in the amount of communication which took place with the various cells tested, but no pattern of difference could be discerned. Line 66cl-4 did not preferentially communicate with cells of epithelial versus fibroblast morphology, nor with tumor versus nontumor cells. The 66cl-4 cells retained the ability of their parent line to form metastatic tumors when injected s.c. into BALB/c mice. A quantitative selectivity of communication is thus expressed in these malignant metastatic cells, but it is apparently unrelated to either the morphological or malignant phenotype of the donor. Contact-mediated communication between tumor subpopulations may differentially affect growth and drug sensitivity within a tumor.
Cancer Res 1983 Sep
PMID:Quantitative selectivity of contact-mediated intercellular communication in a metastatic mouse mammary tumor line. 687 51

Complementation studies were performed with ts2, a mouse 3T3 cell mutant temperature sensitive (ts) for cell and viral DNA synthesis. The ts phenotype is corrected by non-ts mouse or human cells and a non-DNA ts mutant. This gene had been localized to a region on the human X chromosome near the HPRT locus based on isozyme and karyotype analysis of hybrids. Unusually rapid loss and fragmentation of human chromosomes occurs in hybrids with ts2. Hybrids between ts2 and other DNA- ts mutants of mouse cells did not show complementation of the growth phenotype.
Somatic Cell Genet 1980 Sep
PMID:Temperature-sensitive mutants of BALB/3T3 cells. III. Hybrids between ts2 and other mouse mutant cells affected in DNA synthesis and correction of ts2 defect by human X chromosome. 693 1


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