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

Mammalian X chromosome inactivation is generally considered to be a good example of stable transcriptional repression; however, there has been no satisfactory evidence for transcriptional control. We have made a test of the hypothesis of transcriptional control by Northern blot analysis of RNA from a woman heterozygous for a mutant Hpt allele which shows no detectable transcription of wild-type mRNA. Cells from this Hpt+ Hpt- woman were separated into HPRT+ and HPRT- subpopulations by selection in HAT or thioguanine. The HPRT+ population (in which the Hpt+ is on the active X) transcribed normal Hpt mRNA, while the HPRT- population (in which the Hpt+ allele is on the inactive X) did not. These results provide strong support for the hypothesis of transcriptional control.
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PMID:Mammalian X chromosome inactivation: testing the hypothesis of transcriptional control. 345 56

The loci for steroid sulfatase (STS), the deficiency of which causes X-linked ichthyosis, the cell surface antigen 12E7 (MIC2X), and the blood group antigen Xg (Xg) have been mapped to Xp22.3. These loci are of particular interest since they do not appear to undergo X-chromosome inactivation. In an attempt to establish the relative order of STS and MIC2X, fibroblasts from carriers of four different X/Y translocations and an X/10 translocation were obtained and fused with mouse cell lines deficient in hypoxanthine phosphoribosyltransferase. The breakpoints on the X chromosome in these five translocations are in Xp22. Several independent clones from each fusion were isolated in HAT medium. The clones were examined cytogenetically, and in each case at least two independent clones were identified that have an active X/Y or X/10 translocation chromosome in the absence of other X or Y material. These clones were then tested for STS and 12E7 expression. In two of the X/Y translocations, the markers, STS and 12E7, were both absent. In the X/10 and a third X/Y translocation, both markers were retained. In each of three clones containing the fourth X/Y translocation, STS activity was retained but 12E7 antigenicity was lost. Assuming that this is a simple translocation and does not represent a more complex rearrangement, these results suggest that MIC2X is distal to STS.
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PMID:Fine mapping of the distal short arm of the human X chromosome using X/Y translocations. 346 Mar 34

Proteose peptone-induced peritoneal macrophages from CBA/J (H-2k) mice have been fused to a hypoxanthine phosphoribosyltransferase-negative variant of the P388D1 (H-2d) murine macrophage cell line. Six hybrid clones were isolated following HAT selection and further characterized. Five of the six clones express class I antigens of both parental haplotypes by microelisa and by flow cytometric analysis. Class II antigen expression of both haplotypes was apparent following a 72-hr incubation of the hybrids with concanavalin A-stimulated rat spleen cell supernatant. However, I-Ad was expressed in all hybrids to a greater extent than I-Ak. Three clones with the highest level of I-Ak expression, E5, C2, and C4, were capable of antigen presentation to the I-Ak-restricted T-cell line, D10.G4.1. LPS induction of the hybrids resulted in a 2- to 15-fold increase in the amount of IL-1 produced relative to the P388D1 parent. Finally, in distinction to P388D1, all hybrids demonstrated increased Fc-mediated erythrophagocytosis of chromium-labeled antibody-coated erythrocytes. These murine macrophage hybrids appear stable and should serve as useful models in understanding the regulation of macrophage function.
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PMID:Establishment and characterization of murine macrophage hybrids. 349 85

The study deals with intragenic complementation between clones of Chinese hamster cells carrying mutations in the HPRT gene. All clones were of independent origin, selected in media containing one of three purine bases: 8-azaguanine (8 AG), 6-mercaptopurine (6MP), or 6-thioguanine (6TG). Some of the clones were spontaneous, others were induced by various mutagens. To make the study less time-consuming, an experimental set-up was proposed for simultaneous complementation testing of up to 10 clones. As a result, about 400 combinations of clones have been analyzed. Twelve pairs of complementating mutants have been identified in HAT medium. A linear complementation map has been constructed for the HPRT locus, showing five complementation groups. The changes in kinetic and other characteristics observed for mutant HPRT show that all the mutants studied carry structural gene mutations. Analysis of the biochemical characteristics of HPRT has revealed considerable differences between mutant enzymes in clones belonging to different complementation groups (three groups were examined). At the same time, the four mutant clones of complementation group II show similar HPRT characteristics, suggesting a relative similarity of their structural variants of the enzyme. The hybrid nature of HPRT in clones resulting from the fusion of mutant cells confirms the intragenic nature of complementation.
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PMID:Complementation analysis of locus for hypoxanthine guanine phosphoribosyltransferase in Chinese hamster cells. 385 54

An aryl hydrocarbon hydroxylase (AHH)-deficient gene A- mutant of the mouse line Hepa-1 was treated with calcium phosphate precipitates of DNA from Hepa-1, the rat line H4IIEC3, or an A- -human hybrid in which the A- mutation is complemented by the corresponding human gene. AHH+ transfectants were isolated by selection with benzo[ghi]perylene plus near UV. In addition, a gene A- mutant which also carries a mutation for hypoxanthine phosphoribosyltransferase deficiency was treated with the above genomic DNAs together with pSV2-gpt DNA, and cotransfectants were isolated after treatment with both benzo[ghi]pereylene and HAT. All transfectants and cotransfectants were inducible for AHH by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Both transfectants and cotransfectants were unstable during culture, rapidly losing AHH activity. Rat DNA-derived transfectants were probed in Southern blots with a cDNA probe to mouse cytochrome P1-450 that cross-hybridizes to the corresponding rat gene. All rat DNA-derived transfectants contained the rat P1-450 gene. In half of the transfectants, the rat gene was amplified four- to sevenfold. In one transfectant, the rat gene was truncated at the 3' end. The proportion of rat DNA in different transfectants, as determined by hybridization to a rat repetitive sequence, ranged from less than 1% to 5%. AHH activity and the rat P1-450 gene segregated together in subclones of one of the transfectants. These results demonstrate that the A gene is either the structural gene for cytochrome P1-450, or another very closely linked gene. Previous results (O. Hankinson et al., J. Biol. Chem. 260:1790-1795, 1985) favor the former alternative.
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PMID:Transfection by genomic DNA of cytochrome P1-450 enzymatic activity and inducibility. 399 Jun 91

Fusion of hypoxanthine phosphoribosyltransferase (HPRT)(-) rat hepatoma cells with HPRT(+) human fibroblasts yielded hybrid clones that grew in HAT selective medium and contained all the rat chromosomes and one to nine human chromosomes. Among the retained chromosomes was the human X chromosome. In all clones backselected in medium containing 8-azaguanine, human X chromosome was absent. Electrophoretic analysis revealed that, without exception, hybrid clones growing in HAT medium had an active HPRT enzyme, either human or rat, or both. When these clones were backselected in 8-azaguanine, they did not show HPRT enzyme activity. Hybrids that contained the human X chromosome also had human glucose-6-phosphate dehydrogenase. The observed reexpression of rat HPRT in hybrid cells derived from HPRT(-) rat cells suggests that a genetic factor from the human cell determined the expression of the rat structural gene for HPRT.
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PMID:Reexpression of the rat hypoxanthine phosphoribosyltransferase gene in rat-human hybrids. 435 57

Transfection of mammalian cells with genomic DNA and cloned genes is now relatively routine. However, the vast majority of studies have used rodent cells as recipients. Here we describe efficient transfection of two human cell lines, the hypoxanthine guanine phosphoribosyltransferase (HPRT)-deficient HeLa line, D98/AH-2, and the adenine phosphoribosyltransferase (APRT)-deficient HT1080 line, HTD114. D98/AH-2 cells were transfected with the pSV2-gpt plasmid of Mulligan and Berg, which contains the E. coli xanthine-guanine phosphoribosyltransferase (gpt) gene, and Gpt + transfectants were selected in HAT medium. HTD114 cells were transfected with (1) genomic hamster DNA, and ouabain resistant transfectants were selected in 5 X 10(-7)M ouabain; (2) with hamster and mouse genomic DNA, and Aprt + cells were selected in AAA medium; (3) with plasmids containing either the cloned hamster or mouse APRT genes, and Aprt + cells were selected; and (4) with phage particles containing a cloned mouse APRT gene, and Aprt + cells were selected. Transfection efficiencies ranged from 0.25 to 1.5 X 10(3) transfectants per microgram DNA, and in certain cases secondary transfections were done. Foreign DNA in recipients was detected by blot hybridization, and the expression of foreign genes was detected by cell growth in selective media and the expression of enzymes characteristic of the species of the donor DNA. The majority of transfectants showed stable expression of the transgenome.
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PMID:Plasmid, phage, and genomic DNA-mediated transfer and expression of prokaryotic and eukaryotic genes in cultured human cells. 623 89

Bovine embryonic trachea cells were hybridized with mouse A9 cells deficient in hypoxanthine phosphoribosyltransferase, and cattle-mouse hybrid cells clones were isolated after HAT/ouabain selection. In these interspecific cell hybrids, bovine glucose-6-phosphate dehydrogenase, alpha-galactosidase, and phosphoglycerate kinase were expressed concordantly with bovine HPRT. Their expression depended on the presence of bovine X chromosome. These data indicated that the genes for G6PD, PGK, and HPRT are linked and can be assigned to the bovine X chromosome.
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PMID:The bovine genes for phosphoglycerate kinase, glucose-6-phosphate dehydrogenase, alpha-galactosidase, and hypoxanthine phosphoribosyltransferase are linked to the X chromosome in cattle-mouse cell hybrids. 625 51

Primary nasopharyngeal carcinoma (NPC) cells were fused to hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-defective cells derived from adenoid tissues using Sendai virus. Some of the fused cells developed into epithelial-like hybrid cells in a selective HAT medium. The hybrid cells (NPC-KT) were Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA)-positive cells. There have been no reports on the establishment of EBNA-positive epithelial cell lines derived from NPC. Thus, the epithelial-like hybrid cells might serve as an in vitro model for studying the biologic activity of NPC-associated EBV.
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PMID:Establishment of Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA)-positive nasopharyngeal carcinoma hybrid cell line (NPC-KT). 631 11

Human epidermoid carcinoma A431 cells, possessing an extraordinarily high number of epidermal growth factor (EGF) receptors (1), were found to be hypotetraploid in their chromosome constitution and to contain two copies of intact chromosome 7 and two types of the translocation chromosomes involving chromosome 7 (M4 and M14) as well as several other rearranged chromosomes. The A431 cells were fused with mouse A9 cells, which lack EGF receptors (2) and are deficient in hypoxanthine phosphoribosyltransferase (3), and the human-mouse cell hybrid (AA series) were selected in HAT/ouabain medium (3, 4). The expression of high EGF binding ability was correlated with the presence of human translocation chromosome M4. AA hybrid clones that contained intact human chromosome 7 but not the marker chromosome M4 expressed only ordinary levels of EGF receptors. The EGF receptors expressed in the AA hybrids were proven to be of human nature by immunoprecipitation of the receptors cross-linked with [125I]EGF. These observations and our previous gene assignment of the EGF receptor to human chromosome 7 (2, 5) suggest that the marker chromosome M4 may carry an alteration(s) in the gene(s) involved in EGF receptor biosynthesis.
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PMID:Genetic analysis of hyperproduction of epidermal growth factor receptors in human epidermoid carcinoma A431 cells. 632 59


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