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)

Altered sequences were determined of 52 independent spontaneous mutations occurring in a cDNA of the human hypoxanthine phosphoribosyltransferase (hprt) gene, which was integrated into chromosomal DNA of the mouse cell as a part of the retroviral shuttle vector. Spontaneous mutations comprised a variety of events: base substitutions, frameshifts, deletions, duplications, and complex mutational events, and were distributed randomly over the coding region of the gene. Frameshifts were the most frequent mutational event (38%), and base substitutions were the next most frequent (25%), followed by deletions (19%). Frameshift and deletion mutations commonly occurred preferentially at sites flanked by short direct repeats. Short inverted repeats were frequently found to be associated with duplication and complex mutational events. Analysis of the sequence alterations in the mutant genes suggests that misalignment mutagenesis represents an important molecular mechanism for the generation of spontaneous mutations in eukaryotic cells.
Mol Gen Genet 1989 Nov
PMID:Spectrum of spontaneous mutations in a cDNA of the human hprt gene integrated in chromosomal DNA. 262 50

Genetic toxicology studies were conducted on organic dyes and mixtures used in colored smoke munitions. The dyes studied included Solvent Red 1; two different batches (Lot 1 and Lot 2) of Disperse Red 11; terephthalic acid; and a mixture of 25 parts Solvent Red 1, 5 parts Disperse Red 11, and 16 parts terephthalic acid. The dyes were evaluated for their ability to produce mutations in Salmonella bacterial strains and in Chinese hamster ovary (CHO) cells. The dyes were also tested in CHO cells to determine cytotoxicity and the induction of sister chromatid exchanges and chromosome aberration. None of the dyes were genotoxic in the standard Ames assay using bacterial strain TA1535 or TA100 with or without the addition of S-9 or in TA98 and TA1538 without S-9. With S-9, Disperse Red 11 (Lot 2) showed significant mutagenic activity in TA98 and TA1538 which increased as a function of S-9 concentration. However, the maximum level of mutagenic activity detected was low (3.8 revertants/micrograms). The azo dye Solvent Red 1 was also negative in a pre-incubation assay designed to reduce azo compounds to free amines. Solvent Red 1 was cytotoxic to mammalian cells, caused a significant increase in SCE, but was not mutagenic or clastogenic. Disperse Red 11 (Lot 1 and Lot 2) were not cytotoxic or clastogenic but produced an increase in cell cycle time and SCE frequency. Only Disperse Red 11 (Lot 2) increased mutations in the CHO/hypoxanthine-guanine phosphoribosyltransferase (HGPRT) assay. The mutagenic activity of the dye mixture was not significant, suggesting no synergistic interaction between the dyes. These studies demonstrated that none of the dyes was clastogenic and that a contaminant in Disperse Red 11 (Lot 2) may be responsible for the weak mutagenic activity in both mammalian and bacterial cell systems.
Environ Mol Mutagen 1989
PMID:In vitro genotoxicity of dyes present in colored smoke munitions. 266 Dec 23

The adenine phosphoribosyltransferase (APRTase) and hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) activities from promastigotes of Leishmania donovani have been purified to homogeneity using ammonium sulfate precipitation, DEAE-cellulose exclusion, and either AMP-agarose (APRTase) or GTP-agarose (HGPRTase) affinity chromatography. The specific activities of the affinity-purified APRTase and HGPRTase fractions were 326-fold and 1341-fold greater than those in the 40-80% ammonium sulfate precipitate, respectively. The purified APRTase migrated as a single band on sodium dodecyl sulfate (SDS) polyacrylamide gels with a size of 29 kDa, while HGPRTase was also determined to be homogeneous by SDS gel electrophoresis with a size of 24 kDa. In addition, a mutant cell line, APPB2, partially deficient in APRTase activity, still contained quantities of purifiable APRTase protein, while a clonal secondary derivative of the APPB2 cell line that is completely deficient in APRTase activity, APPB2-640A3, failed to express purifiable APRTase protein. The homogeneous enzymes possessed apparent Km values for their nucleobase substrates between 2.0 and 5.0 microM, and both enzymes were inhibited by their immediate or ultimate reaction endproducts, APRTase by AMP and PPi and HGPRTase by GMP, GTP, and PPi. The generation of homogeneous preparations of APRTase and HGPRTase protein will serve as a prerequisite for the generation of immunological and molecular biological probes to analyze the leishmanial phosphoribosyltransferases.
Mol Biochem Parasitol 1989 Mar 15
PMID:Purification and characterization of the adenine phosphoribosyltransferase and hypoxanthine-guanine phosphoribosyltransferase activities from Leishmania donovani. 270 89

Part of the higher-order structure of chromatin is achieved by constraining DNA in loops ranging in size from 30 to 100 kilobase pairs; these loops have been implicated in defining functional domains and replicons and possibly in facilitating transcription. Because the human active and inactive X chromosomes differ in transcriptional activity and replication, we looked for differences in their chromatin loop structures. Since the islands of CpG-rich DNA at the 5' ends of X-linked housekeeping genes are the regions where functional differences in DNA methylation and nuclease sensitivity are found, we looked for scaffold association of these sequences after extraction of histones with lithium diiodosalicylate. Specifically, we examined the 5' CpG islands within the hypoxanthine phosphoribosyltransferase, glucose 6-phosphate dehydrogenase, P3, GdX, phosphoglycerate kinase type 1, and alpha-galactosidase loci in human lymphoblasts obtained from individuals with 1 to 4 X chromosomes. Although we detected no scaffold-associated regions near these genes, we found several such regions at the ornithine transcarbamylase and blood clotting factor IX loci. Our results suggest that the CpG islands are excluded from the nuclear scaffold and that even though transcriptionally active, housekeeping genes are less likely than X-linked tissue-specific genes to be scaffold associated. In all cases, the pattern of scaffold association was the same for loci on active and inactive X chromosomes.
Mol Cell Biol 1989 Jun
PMID:Chromatin loop structure of the human X chromosome: relevance to X inactivation and CpG clusters. 276 35

We investigated the conformation of the X-linked mouse hypoxanthine-guanine phosphoribosyltransferase gene (HPRT) promoter region both in chromatin from the active and inactive X chromosomes with DNase I and in naked supercoiled DNA with S1 nuclease. A direct comparison of the chromatin structures of the active and inactive mouse HPRT promoter regions was performed by simultaneous DNase I treatment of the active and inactive X chromosomes in the nucleus of interspecies hybrid cells from Mus musculus and Mus caroli. Using a restriction fragment length polymorphism to distinguish between the active and inactive HPRT promoters, we found a small but very distinct difference in the DNase I sensitivity of active versus inactive chromatin. We also observed a single DNase I-hypersensitive site in the immediate area of the promoter which was present only on the active X chromosome. Analysis of the promoter region by S1 nuclease digestion of supercoiled plasmid DNA showed an S1-sensitive site which maps adjacent to or within the DNase I-hypersensitive site found in chromatin but upstream of the region minimally required for normal HPRT gene expression.
Mol Cell Biol 1987 Aug
PMID:Nuclease sensitivity of the mouse HPRT gene promoter region: differential sensitivity on the active and inactive X chromosomes. 282 12

The virtually complete deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) results in a devastating neurological disease, Lesch-Nyhan syndrome. Transfer of the HPRT gene into fibroblasts and lymphoblasts in vitro and into hematopoietic cells in vivo has been accomplished by other groups with retroviral-derived vectors. It appears to be necessary, however, to transfer the HPRT gene into neuronal cells to correct the neurological dysfunction of this disorder. The neurotropic virus herpes simplex virus type 1 has features that make it suitable for use as a vector to transfer the HPRT gene into neuronal tissue. This report describes the isolation of an HPRT-deficient rat neuroma cell line, designated B103-4C, and the construction of a recombinant herpes simplex virus type 1 that contained human HPRT cDNA. These recombinant viruses were used to infect B103-4C cells. Infected cells expressed HPRT activity which was human in origin.
Mol Cell Biol 1988 Jan
PMID:Herpes simplex virus-mediated human hypoxanthine-guanine phosphoribosyltransferase gene transfer into neuronal cells. 282 6

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.
Mol Cell Biol 1987 Dec
PMID:A new genetic approach for studying hormonal regulation of urokinase-type plasminogen activator gene expression in LLC-PK1 cells. 283 Apr 99

To examine the association between chromatin structure and gene expression at the human hypoxanthine phosphoribosyltransferase (HPRT) locus, DNase I sensitivity of active and inactive genes was analyzed. In a set of human-hamster hybrid lines containing either an active or an inactive human X chromosome, or a derivative of the latter in which the HPRT gene was reactivated by 5-azacytidine treatment, only the promoter region of the gene was found to contain a hypersensitive domain, and its presence was strictly correlated with gene activity. An S1 nuclease-sensitive site was mapped upstream from the DNase I hypersensitive domain using supercoiled plasmids. The overall level of DNase I sensitivity in the interior of the HPRT gene was also assessed by comparing the degradation of polymorphic restriction fragments on active and inactive alleles in both polyclonal and monoclonal lines of female human cells. In these internally controlled experiments, the active X chromosome was found to be approximately twofold more susceptible to DNase I digestion than the inactive X chromosome.
Somat Cell Mol Genet 1988 May
PMID:Comparative study of DNase I sensitivity at the X-linked human HPRT locus. 283 22

Molecular analysis of an unusual patient with the Lesch-Nyhan syndrome has suggested that the mutation is due to a partial HPRT gene duplication. We now report the cloning and sequencing of the mutant HPRT cDNA which shows the precise duplication of exons 2 and 3. This mutation is the result of an internal duplication of 16-20 kilobases of the gene. The structure of the mutant gene suggests that the duplication was not generated by a single unequal crossing-over event between two normal HPRT alleles. Growth of Epstein-Barr virus-transformed lymphoblasts from this patient in selective medium has permitted isolation of spontaneous HPRT+ revertants of this mutation. The reversion event involves a second major HPRT gene rearrangement where most or all of the duplicated portion of the mutant gene is deleted. The original mutation therefore has the potential for spontaneous somatic reversion. This may explain the relatively mild symptoms of the Lesch-Nyhan syndrome exhibited by this patient.
Somat Cell Mol Genet 1988 May
PMID:Spontaneous reversion of novel Lesch-Nyhan mutation by HPRT gene rearrangement. 283 25

A sequence that supports extrachromosomal replication of plasmids in yeast has been identified within the first intron of the human hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene. This represents the first isolation of such an autonomously replicating sequence (ARS) from an exactly known position in the human genome. This ARS shares similarities of imparted yeast phenotype and DNA sequence with other heterologous ARSs. In addition, this sequence is found to be a matrix association region (MAR) on the basis of specific binding to nuclear matrices prepared from several mammalian cell types. It also exhibits anomalous electrophoretic behavior, characteristic of bent DNA, on polyacrylamide gels. The coincidence of these properties supports the possibility that this region may play a role in DNA replication within its normal chromosomal context.
Mol Gen Genet 1988 May
PMID:Yeast ARS function and nuclear matrix association coincide in a short sequence from the human HPRT locus. 284 70


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