Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

In LLC-PK1 cells, a cyclic AMP (cAMP)-elevating peptide hormone, calcitonin, induces urokinase-type plasminogen activator (uPA) gene transcription without concomitant protein synthesis. To understand the molecular mechanism of the uPA gene regulation by cAMP, we developed a system which allows us to obtain mutant cells with modified regulatory proteins. A uPA-gpt hybrid gene was constructed, in which the regulatory region of the uPA gene was linked to a bacterial xanthine-guanine phosphoribosyltransferase gene (gpt), and it was transfected into LLC-PK1 cells. A stably transformed cell line, which expressed gpt only in the presence of calcitonin, was obtained, and then these cells were treated with a chemical mutagen, ethyl methanesulfonate. Cells were screened for constitutive gpt expression and, as mutations in regulatory proteins should affect the two genes at the same time, cells were further screened for an increased basal uPA mRNA level. Several such clones were obtained and none of them had modified cAMP-dependent protein kinase activity, suggesting that mutations were in the post-protein kinase step in the pathway of hormone action. Five clones were fused with the parent LLC-PK1 cells, and all of the fusion cells showed reduced basal uPA mRNA levels, indicating that they were recessive mutants. One clone was analyzed further for sensitivity to calcitonin in the induction of uPA mRNA, and it showed a significantly different dose-response pattern compared with parent cells. These results suggest that the uPA gene is regulated, at least partly, by a negatively regulating factor and that the action of cAMP is linked to this factor.
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PMID:A new genetic approach for studying hormonal regulation of urokinase-type plasminogen activator gene expression in LLC-PK1 cells. 283 Apr 99

BALB/c mouse thymoma-derived T cell line, CAK4.4 (Thy-1+, L3T4-, Lyt-2-), produced a large amount of TCR-gamma mRNA, a trace amount of TCR-beta mRNA but no detectable level of TCR-alpha mRNA. Another BALB/c mouse thymoma-derived T cell line, CAK1.3 (Thy-1+, L3T4+, Lyt-2+), synthesized a high level of TCR-alpha as well as TCR-beta mRNA but did not produce any amount of TCR-gamma mRNA. HAT-sensitive clones were established from the two T cell lines. Azaguanine-resistant, HPRT- CAK4.4 cells and bromodeoxyuridine-resistant, TK- CAK1.3 cells were fused by electrofusion method and the resultant hybrids were analyzed for expression of TCR genes as well as the changes of their cell surface phenotypes. Transcription of TCR-gamma gene was completely suppressed in all hybrids tested, although Southern blot analysis showed that the hybrids maintained TCR-gamma chain genes derived from both parental cells. TCR-alpha gene transcription occurred normally in one hybrid. In two other hybrids, TCR-alpha gene transcription was strongly suppressed. Treatment of the hybrid cells with 12-O-tetradecanoyl phorbol-13-acetate reversed the suppression of TCR-alpha gene transcription, but TCR-gamma gene transcription was not recovered by the same treatment. However, transcription level of TCR-beta gene was not changed in all hybrids. Our results suggested that the different trans-acting regulatory mechanisms control the transcription levels of TCR-alpha and TCR-gamma genes and that such a transcriptional control may play a crucial role in the determination of orderly appearance of TCR-gamma and TCR-alpha gene products during T cell ontogeny in the thymus.
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PMID:Trans-acting regulatory factors for T cell antigen receptor alpha- and gamma-chain gene expression. 283 44

X-chromosome inactivation was investigated in human chorionic villi in the first trimester of pregnancy and cultured cells established from them. Expression of glucose-6-phosphate dehydrogenase (G6PD) was evaluated in these extraembryonic cells from four females heterozygous for the electrophoretic variants (AB) of G6PD. In each case the uncultured villi as well as derived cultured cells expressed the AB phenotype for G6PD with about equal intensity for the A and B bands. Single-cell-derived clones established from two of the four cases expressed either G6PD A or B. One clone expressing G6PD B was fused with mouse cells, and a hybrid clone retaining the inactive human X chromosome was isolated; there was no evidence of human G6PD expression in this clone retaining an inactive human X. DNA methylation in the first intron of the human gene for hypoxanthine phosphoribosyltransferase (HPRT) was evaluated in the four pairs of cultured villi and fetal cells. No differences were detected between the cultured villi and fetal cells as they all showed bands characteristic of an inactive X from somatic cells. These results show that there is no preferential inactivation of an X in the majority of cells that constitute human tertiary chorionic villi or in cultured cells derived from them. Long-term cultures established from chorionic villi appear to be no different from somatic cells with respect to X-chromosome inactivation.
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PMID:X-chromosome inactivation in cultured cells from human chorionic villi. 292 38

An improved method was developed to align related protein sequences and search for homology. A glutamine amide transfer domain was identified in an NH2-terminal segment of GMP synthetase from Escherichia coli. Amino acid residues 1-198 in GMP synthetase are homologous with the glutamine amide transfer domain in trpG X D-encoded anthranilate synthase component II-anthranilate phosphoribosyltransferase and the related pabA-encoded p-aminobenzoate synthase component II. This result supports a model for gene fusion in which a trpG-related glutamine amide transfer domain was recruited to augment the function of a primitive NH3-dependent GMP synthetase. Sequence analyses emphasize that glutamine amide transfer domains are thus far found only at the NH2 terminus of fused proteins. Two rules are formulated to explain trpG and trpG-related fusions. (i) trpG and trpG-related genes must have translocated immediately up-stream of genes destined for fusion in order to position a glutamine amide transfer domain at the NH2 terminus after fusion. (ii) trpG and trpG-related genes could not translocate adjacent to a regulatory region at the 5' end of an operon. These rules explain known trpG-like fusions and explain why trpG and pabA are not fused to trpE and pabB, respectively. Alignment searches of GMP synthetase with two other enzymes that bind GMP, E. coli amidophosphoribosyltransferase and human hypoxanthine-guanine phosphoribosyltransferase, suggest a structurally homologous segment which may constitute a GMP binding site.
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PMID:Identification of a trpG-related glutamine amide transfer domain in Escherichia coli GMP synthetase. 298 57

Sciatic nerve Schwann cells from strain LEC rats, homozygous for the c form of 6-phosphogluconate dehydrogenase (6-PGD), and RN22 rat Schwannoma cells, a subclone of RN2 deficient in hypoxanthine phosphoribosyltransferase and expressing the s form of 6-PGD, were fused to produce 'RNS' hybrid clones which proliferate rapidly in a medium containing hypoxanthine, aminopterin and thymidine (HAT) and express c, s and c/s heterodimeric forms of 6-PGD. RNS cells, like both parents, maintain a high baseline activity of 2', 3'-cyclic nucleotide 3'-phosphohydrolase and, as in RN22, activity of this enzyme is further inducible by 1 mM N6, O2'-dibutyryl 3', 5'-cyclic AMP. The RNS clones resemble normal Schwann cells in the capacity to bind radioiodinated axolemmal fragments to their plasma membranes.
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PMID:Characterization of rat schwannoma-Schwann cell hybrids. 302 58

Sezary's syndrome is a leukemic proliferation of OKT4+ lymphocytes. Sezary cells were isolated by differential centrifugation and fused to CEM.8azar.C, and HGPRTase-lacking clone of CEM. The hybrid cells were studied for their ability to produce soluble mediators of human monocyte cytotoxicity. The product of a single clone, FtF3, which bore the surface phenotype of Sezary cells, was characterized. Monocyte cytotoxicity-inducing factor (MCF) was found to be stable at pH 2 for 1 hr, unlike IFN-gamma, and was found to be more heat stable as well. Moreover, treatment of MCF with antisera to IFN-gamma, IFN-alpha or a combination of IFN-gamma and IFN-alpha failed to neutralize its biologic activity. MCF binds to matrix gel Red A. MCF eluted from this dye-ligand was found to have an apparent m.w. of 11,500 by gel filtration and 14,700 by SDS-polyacrylamide gel electrophoresis. MCF produced by hybridized Sezary cells appear to be neither IFN-gamma nor an altered molecular form of IFN-gamma, yet is a potent inducer of human monocyte cytotoxicity.
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PMID:Identification of a human monocyte cytotoxicity-inducing factor from T cell hybridomas produced from Sezary's cells. 308 3

The clonal rat pituitary tumor cell line GH4C1 secretes PRL but does not respond to dopamine, a physiological inhibitor of PRL. In an attempt to generate a dopamine-responsive cell line, GH4C1 cells, which lack the enzyme hypoxanthine-guanine phosphoribosyltransferase, were fused with cells from the pituitary glands of lactating rats to generate cell hybrids. The GH4C1 cells were fused with dispersed normal pituitary cells by either chemical fusion in 40% polyethylene glycol or electrofusion. The fused cells were grown in medium with hypoxanthine, aminopterin, and thymidine (HAT) for 4 weeks to select for hybrid cells. Control fusions between GH4C1 cells only or normal cells only did not produce viable colonies. Of 36 HAT-selected colonies, 3 responded to 10 nM bromocryptine (BCR) with inhibition of TRH-stimulated PRL release. These hybrid colonies had an inhibitory response similar to that of normal pituitary cells in culture. Both TRH- and vasoactive intestinal peptide-stimulated PRL release were inhibited to basal levels by 10 nM BCR, with an IC50 for BCR of approximately 0.25 nM. Basal hormone release was not inhibited by BCR. The BCR-sensitive hybrid cells grew more slowly than the parental GH4C1 line both in culture and when passaged in female Wistar-Furth rats. The response of the hybrid cells to the dopamine agonist and the characteristic of slow growth were lost after 9 months of continuous culture and after freezing cells. The parental GH4C1 cells were grown in female Wistar-Furth rats, the resulting tumors were dissociated, and the cells were grown in culture. This resulted in a brief establishment of the dopamine response. Stimulated PRL and GH release from freshly dispersed GH4C1 tumor cells was inhibited by BCR at concentrations from 0.1-10 nM, and spiroperidol reversed the inhibition. The inhibitory response to the dopaminergic agonist was lost quickly as the cells were carried in culture. These results demonstrate that GH4C1 cells may have the genetic information necessary for dopaminergic inhibition of PRL synthesis, but that the dopamine response is not observed under standard tissue culture conditions.
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PMID:Transient dopaminergic inhibition of prolactin release from hybrid cells derived by fusion of normal rat pituitary and GH4C1 tumor cells. 312 81

We have developed a bacteriophage lambda vector (lambda NMT) that permits efficient transduction of mammalian cells with a cDNA clone library constructed with the pcD expression vector (H. Okayama and P. Berg, Mol. Cell. Biol. 3:280-289, 1983). The phage vector contains a bacterial gene (neo) fused to the simian virus 40 early-region promoter and RNA processing signals, providing a dominant-acting selectable marker for mammalian transformation. The phage DNA can accommodate pcD-cDNA recombinants with cDNA of up to about 9 kilobases without impairing the ability of the phage DNA to be packaged in vitro and propagated in vivo. Transfecting cells with the lambda NMT-pcD-cDNA recombinant phage yielded G418-resistant clones at high frequency (approximately 10(-2]. Cells that also acquired a particular cDNA segment could be detected among the G418-resistant transformants by a second selection or by a variety of screening protocols. Reconstitution experiments indicated that the vector could transduce 1 in 10(6) cells for a particular phenotype if the corresponding cDNA was present as 1 functional cDNA clone per 10(5) clones in the cDNA library. This expectation was confirmed by obtaining two hypoxanthine-guanine phosphoribosyltransferase (HPRT)-positive transductants after transfecting 10(7) HPRT-deficient mouse L cells with a simian virus 40-transformed human fibroblast cDNA library incorporated into the lambda NMT phage vector. These transductants contained the human HPRT cDNA sequences and expressed active human HPRT.
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PMID:Bacteriophage lambda vector for transducing a cDNA clone library into mammalian cells. 315 4

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


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