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)

A method for the quantitation of metabolic cooperation between cells is described. The method depends upon measuring the increase in HGPRTase activity that occurs between HGPRT+ cells and the HGPRT-LN (Lesch-Nyhan) cells. The variables upon which this method depends and their effect on the final determination are discussed.
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PMID:Quantitation of metabolic cooperation by measurement of HGPRTase activity. 257 5

The polymerase chain reaction technique is widely employed to amplify short segments of genomic DNA to determine if a specific change has occurred. However, some investigators need to sequence the entire coding region of mammalian genes, e.g., cellular ras genes or the gene encoding hypoxanthine (guanine) phosphoribosyl transferase (HPRT), to determine what specific changes have occurred. To do so, they isolate RNA from large populations of cells, amplify cDNA from the gene of interest, subclone the product, and sequence two or more isolates to determine the common mutation. We have developed a method to simplify this procedure by copying mRNA of the hprt gene directly from the lysate of a clone of mutant diploid human fibroblasts (e.g., 100 cells). We amplified the first and second strand of the cDNA of the gene of interest 10(10)- to 10(11)-fold, obtained 5 to 10 micrograms of DNA in less than 10 h, and sequenced the coding region directly without the need for RNA extraction or DNA template purification. By our method cDNA can be amplified directly from the lysate of just one human cell, but to avoid detecting random changes introduced by the polymerase, we lysed approx. 200 cells from a clone, each containing the identical mutation, amplified the cDNA, and determined the consensus sequence by direct nucleotide sequencing.
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PMID:Amplification and direct nucleotide sequencing of cDNA from the lysate of low numbers of diploid human cells. 268 90

We report the identification of a female patient with the X-linked recessive Lesch-Nyhan syndrome (hypoxanthine phosphoribosyltransferase [HPRT] deficiency). Cytogenetic and carrier studies revealed structurally normal chromosomes for this patient and her parents and demonstrated that this mutation arose through a de novo gametic event. Comparison of this patient's DNA with the DNA of her parents revealed that a microdeletion, which occurred within a maternal gamete and involved the entire HPRT gene, was partially responsible for the disease in this patient. Somatic cell hybrids, generated to separate maternal and paternal X chromosomes, showed that expression of two additional X-linked enzymes, phosphoglycerate kinase and glucose-6-phosphate dehydrogenase, were expressed only in cells that contained the maternal X chromosome, suggesting the presence of a functionally inactive paternal X chromosome. Furthermore, comparison of methylation patterns within a region of the HPRT gene known to be important in gene regulation revealed differences between DNA from the father and the patient, in keeping with an active HPRT locus in the father and an inactive HPRT locus in the patient. Together these data indicate that nonrandom inactivation of the cytogenetically normal paternal X chromosome and a microdeletion of the HPRT gene on an active maternal X chromosome were responsible for the absence of HPRT in this patient.
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PMID:Molecular analysis of a female Lesch-Nyhan patient. 276 Feb 9

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.
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PMID:Spontaneous reversion of novel Lesch-Nyhan mutation by HPRT gene rearrangement. 283 25

Hypoxanthine-guanine phosphoribosyltransferase (HPRT; IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) functions in the purine-metabolic salvage pathway. Two clinical syndromes are associated with a deficiency in HPRT enzyme activity. Virtually complete deficiency leads to the Lesch-Nyhan syndrome, whereas partial deficiency results in hyperuricemia and severe gouty arthritis. Marked heterogeneity in the mutations leading to HPRT deficiency has been found. Mutant enzymes vary with respect to levels of HPRT immunoreactive protein, electrophoretic migration, kinetic properties and amino acid sequence. Analysis of DNA and RNA from patients with HPRT deficiency has revealed point mutations, an internal gene duplication and partial as well as complete gene deletions accounting for the various HPRT mutant enzymes.
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PMID:Genetic analysis of human hypoxanthine-guanine phosphoribosyltransferase deficiency. 289 5

Independent spontaneous or ethyl methanesulphonate (EMS)-induced mutants lacking HPRT enzyme activity were analysed for changes in hprt gene structure. Of 21 spontaneous mutants, 6 had total gene deletions, 2 had partial gene deletions, and 13 were indistinguishable from wild-type by Southern analysis. In contrast a sample of 23 EMS-induced mutants, each of which showed potentially interesting characteristics (e.g. high reversion frequency, X-chromosome rearrangement), showed no detectable hprt gene changes. RNA isolated from 59 mutants with presumptive point mutations (13 spontaneous, 46 EMS-induced) was analysed on dot blots for changes in the amount of hprt mRNA. A wide range of mRNA levels was found, from mutants with undetectable amounts to those with more than wild-type amounts. However, Northern blots of all these mutant RNAs revealed only one (EMS-induced) mutation with a change in hprt mRNA size. Taken with our previously-published data on these mutants, it is argued that they represent a broad range of mutational types, and that the hprt gene mutation system provides a sensitive means of distinguishing mutational spectra of different DNA-damaging agents.
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PMID:Molecular analysis of spontaneous and ethyl methanesulphonate-induced mutations of the hprt gene in hamster cells. 290 64

We have investigated the effects of various dopamine (DA) agonists on induction of abnormal involuntary movements (AIM) in a group of monkeys which had denervated nigro-striatal DA neurons for 10-14 years rendered by a unilateral surgical ventromedial tegmental (VMT) lesion of the brainstem. The surgical lesions were placed when the monkeys were 2-4 years old. The administration of mixed DA agonists, such as L-DOPA, apomorphine (Apo) and abeorphine 201-678, elicit a self-mutilative biting behavior (SMB) of the forelimb digits contralateral to the lesion, and spasticity of the contralateral hindlimb. These dysfunctions resemble, in some aspects, the neurological disturbances associated with Lesch-Nyhan syndrome. The SMB behavior was elicited by mixed DA agonists which predominantly stimulate D1, but not D2 DA receptors, and was prevented or abolished by the D1 DA antagonist SCH 23390 or by the D1 and D2 DA antagonist fluphenazine (Flu), but not by the D2 antagonist (+/-)sulpiride. These results suggest that DA agonist-induced SMB behavior is mediated by D1 and/or by both D1 and D2 DA receptor pathways. To study the relationships between HPRT, the defective enzyme in Lesch-Nyhan syndrome, and the DA neuronal systems, we have measured the effects of nigro-striatal DA degeneration and intrastriatal neuronal degeneration on HPRT activity. The unilateral 6-OHDA-induced nigro-striatal DA degeneration does not significantly alter the HPRT activity on the lesioned side of the striatum, while the quinolinic acid-induced intrastriatal neuronal degeneration significantly reduces the enzyme activity. These results suggest that HPRT is localized on intrastriatal neurons which are also known to contain DA receptors. It is postulated that HPRT deficiency in Lesch-Nyhan syndrome results in abnormal guanine nucleotide metabolism which may affect the regulation of DA receptors.
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PMID:Dopamine agonist induced self-mutilative biting behavior in monkeys with unilateral ventromedial tegmental lesions of the brainstem: possible pharmacological model for Lesch-Nyhan syndrome. 293 64

V79 Chinese hamster cells were cultured in the presence of 3-methylcholanthrene-diolepoxide (10r,9t-dihydroxy-7,8t-epoxy-tetrahydro-3-methylcholanthrene, MCDE) and mutants were selected in medium containing 6-thioguanine (TG). Of 22 TG-resistant mutants examined, 18 were devoid of HPRT (hypoxanthine-guanine phosphoribosyltransferase, EC 2.4.2.8) activity. Two mutants had suffered a total and one a partial gene deletion. The 1.6-kb HPRT mRNA was not detected in these three mutants nor in two others. The remaining mutants did not, however, have a readily demonstrable lesion.
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PMID:On the mechanism of induction of resistance to 6-thioguanine in Chinese hamster V79 cells by 3-methylcholanthrene-diolepoxide. 299 1

DNA from 58 independent HPRT-deficient mutants of V79 hamster cells induced by ionising radiation was analysed by Southern blot hybridization to a full-length hamster hprt cDNA. About half of the gamma-ray-induced mutants (20/43) were apparently total gene deletions, because they lacked all functional hprt gene sequences hybridizing to the cDNA probe. Another 10 mutants showed various partial deletions and/or rearrangements of the hprt gene. The remaining 13 mutants showed no detectable change in comparison to the structure of the normal gene, which correlated well with previous characterization of these mutants indicating that most carry point mutations in the hprt gene. However, it is probable that some of these point mutations occurred spontaneously rather than being radiation-induced. A smaller number of alpha-particle induced mutants gave similar results: out of a total of 15 mutants, 6 appeared to be total gene deletions, 5 had partial deletions and/or rearrangements, and 4 had no detectable changes. Thus, 70% or more of radiation-induced HPRT-deficient mutants arise through large genetic changes, especially deletions of all or part of the hprt gene. This result is to be contrasted with data published previously by ourselves and others indicating that the majority of spontaneous and ethyl methanesulphonate-induced mutations of hprt and similar genes arise by point mutation.
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PMID:The nature of mutants induced by ionising radiation in cultured hamster cells. III. Molecular characterization of HPRT-deficient mutants induced by gamma-rays or alpha-particles showing that the majority have deletions of all or part of the hprt gene. 300 79

The organization of the X-linked gene for human hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8.) has been determined by a combination of restriction endonuclease mapping, heteroduplex analysis and DNA sequence analysis of overlapping genomic clones. The entire gene is 42 kilobases in length and split into 9 exons. The sizes of the 7 internal exons and the exon-intron boundaries are identical to those of mouse HPRT gene. The 5' end of the gene lacks the prototypical 5' transcriptional regulatory sequence elements but contains extremely GC-rich sequences and five GC hexanucleotide motifs (5'-GGCGGG-3'). These structural features are very similar to those found in the mouse HPRT gene and to some of the regulatory signals common to a class of constitutively expressed "housekeeping" genes. Several transcriptional start sites have been identified by nuclease protection studies. Extensive sequence homology between the mouse and human genes is found in the 3' non-coding portion of the gene.
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PMID:The organization of the human HPRT gene. 300 6


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