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)

The Chinese hamster ovary (CHO) assay, which measures newly induced mutations at the hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus, has been widely used for mutagenesis testing. The insensitivity of the standard assay to some genotoxic agents has been speculated to be due to the relatively small number of cells used in the assay. In the present study, we have compared the standard monolayer assay with a suspension adapted CHO assay that uses cell numbers comparable to that of the L5178Y mouse lymphoma assay. Nine compounds, ethyl methanesulfonate (EMS), methyl methanesulfonate (MMS), 2-methoxy-6-chloro-9-[3-(ethyl-2-chloroethyl)-aminopropylamino]-acridine 2HCl (ICR 170), methyl acrylate, ethyl acrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, 2-ethylhexyl acrylate and dicyclopentenyloxyethyl methacrylate were evaluated in the monolayer and suspension assays. Both assays gave the same overall qualitative results for the test compounds. There were some quantitative differences in the mutant frequency for the three compounds found to be mutagenic (EMS, MMS and ICR 170). The acrylates (many of which appear to exert their genotoxic effect through a clastogenic mechanism) were negative in both test systems. The use of the suspension assay did not improve the ability of the hgprt locus to detect the genotoxicity of the acrylates. Thus, increasing the number of cells does not improve the ability of the CHO/HGPRT assay to detect compounds that act primarily by a clastogenic mechanism.
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PMID:Comparison of mutagenicity results for nine compounds evaluated at the hgprt locus in the standard and suspension CHO assays. 171 14

The in vivo frequency of mutants resulting from mutation at the hprt locus in human T-lymphocytes was determined with a cloning assay. T-lymphocytes were obtained from 14 individuals diagnosed with schizophrenia and 5 controls. No significant difference in mutant frequency was observed between the 2 groups. In addition, DNA-repair capacity was measured with the unscheduled DNA synthesis technique in lymphocytes from 7 individuals diagnosed with schizophrenia and 7 controls. Repair capacity was determined following treatment with MMS, MNNG, and 20 J/m2 ultraviolet light. No significant differences in DNA repair were observed between the patient and control groups in response to any of the 3 DNA-damaging agents. These results argue against differences between normal and schizophrenic individuals with respect to in vivo mutant frequency or their capacity to repair DNA lesions induced by MMS, MNNG, or ultraviolet radiation.
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PMID:DNA repair and mutant frequency in schizophrenia. 171 95

Alkylating agent damage was quantified in human T-lymphocytes by calculating gene-specific lesion frequencies and repair rates. At 3 time points after exposure to methyl methanesulfonate (0, 6, and 24 h), T-lymphocyte DNA was extracted, digested with HindIII, and divided into 2 aliquots. Apurinic sites were formed in the DNA fragments of both aliquots by heat-induced liberation of the N-methylpurines. The methoxyamine-treated aliquot provided gene fragments which were refractory to alkaline hydrolysis (full-length fragments), while the fragments in the untreated aliquot were cleaved at apurinic sites by hydroxide. After Southern blotting, lesion frequencies were calculated by comparing the band intensity of the full-length fragment to its unprotected counterpart. The restriction fragments analyzed were from the constitutively active dihydrofolate reductase (dhfr) plus hypoxanthine phosphoribosyltransferase (hprt) genes and from the transcriptionally inactive Duchenne muscular dystrophy gene (dmd). In decreasing order, the fragments containing the most lesions per kb of DNA were: hprt greater than dhfr greater than dmd. T-Lymphocytes from 2 females had 30% more heat-labile N-methylpurines in the active X-linked hprt gene than in the inactive X-linked dmd gene. The lesion frequency found in the male's lone hprt allele was the highest observed. These lesion frequency differences are discussed in terms of chromatin structure. After 6 and 24 h, no significant repair rate differences were observed among the 3 genes.
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PMID:Two expressed human genes sustain slightly more DNA damage after alkylating agent treatment than an inactive gene. 171 96

Southern blot analyses were performed on DNA from at least 10 large and 10 small colony thymidine kinase-deficient (tk -/-) mutants induced by each of 10 mutagens [2-amino-N6-hydroxyadenine (AHA), ethyl methanesulfonate (EMS), methyl methanesulfonate, 2-acetylaminofluorene, methotrexate, caffeine, methapyrilene, 4-(9-acridinylamino)-methanesulfo-m-anisidide, hycanthone methanesulfonate and procarbazine]. Two molecular mutant genotypes were recognized upon digestion with NcoI and subsequent probing with a 1.1 kb cDNA insert from plasmid pMtk 4: (i) no detectable alteration, and (ii) the absence of the functional tkb allele as indicated by the absence of the 6.3 kb fragment. In combination with the previously established chromosomal nature of most small colony tk -/- mutants, this permitted the classification of these 10 mutagens according to the relative proportions of each of four classes of genetic damage they induced. AHA and EMS gave mutational spectra consistent with their point mutational effects in other systems. The other eight mutagens induced mostly small colony mutants, most of which had lost the entire original tkb allele. Methotrexate induced high frequencies of large colony mutants at the tk locus, most of which lacked the tkb allele, although it is weakly or non-mutagenic at the hemizygous hprt locus in these same cells. At least three of these mutagens-methotrexate, caffeine, methapyrilene (and possibly procarbazine)--lack structural alerts for DNA reactivity, implying a major class of non-DNA primary targets for mutagenicity in mammalian cells that interact secondarily with the chromosome. These results are discussed in relation to the known differences in sensitivity among various short-term tests for genotoxicity.
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PMID:Molecular aspects of chemical mutagenesis in L5178Y/tk +/- mouse lymphoma cells. 218 74

Recent reports by several laboratories indicate that not all non-essential target loci are equally capable of detecting chromosomal mutations. The present study was undertaken to determine if both the tk locus in mouse lymphoma cells and the hgprt locus in Chinese hamster ovary (CHO) cells can be used to quantitate chromosomal mutations. Seven known mutagens for the tk locus were selected. These compounds were evaluated in the mouse lymphoma assay and in a suspension adapted CHO assay for their mutagenicity. In addition to the specific locus mutagenesis analysis, mouse lymphoma and CHO cells were evaluated for the frequency of gross chromosome aberrations. From these investigations, it appears that only those compounds [2-methoxy-6-chloro-9-(3-[ethyl-2-chloroethyl] aminopropylamino)-acridine-dihydrochloride (ICR 170), ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS)] that induce significant numbers of large-colony thymidine kinase (TK) mutants also induce significant numbers of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) mutants. The four acrylates evaluated (methyl acrylate, ethyl acrylate, trimethylolpropane triacrylate and tetraethyleneglycol diacrylate) induced almost exclusively small-colony TK mutants and very few if any HGPRT mutants. Aberration analysis revealed that both the mouse lymphoma and CHO cells responded to the clastogenicity of the compounds (except for ICR 170 which was not positive in CHO cells) and that neither cell line was clearly more sensitive than the other to the clastogens tested. It is significant that the four acrylates give little or no evidence of genotoxicity when evaluated using selection for HGPRT-deficient mutants, yet are clearly clastogenic to the same cells in the same experiment. These results are consistent with the hypothesis that the hgprt locus may not be useful as a marker to evaluate the clastogenic component of a genotoxic compound. The present study adds to the increasing number of studies that support the view that the hemizygous nature of the hgprt locus permits the recovery of mutations primarily affecting the function of a single gene; whereas the heterozygous nature of the tk locus permits the recovery of both single gene and chromosomal mutations.
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PMID:Differential mutant quantitation at the mouse lymphoma tk and CHO hgprt loci. 268 35

Pretreatment of sodium arsenite reduces hypoxanthine-guanine phosphoribosyltransferase mutagenicity and overcomes the inhibition of mitosis and cell proliferation but has no apparent effect on the cytotoxicity and clastogenicity in methyl methanesulfonate (MMS)-treated Chinese hamster ovary cells. Posttreatment of sodium arsenite drastically increases the cytotoxicity, clastogenicity, hypoxanthine-guanine phosphoribosyltransferase mutagenicity, and inhibition of mitosis and cell proliferation induced by MMS. Sodium arsenite either pre- or posttreatment has no apparent effect on the MMS-induced sister chromatid exchanges. The present results indicate that pretreatment of sodium arsenite not only does no harm but may even benefit the MMS-treated cells. On the contrary, posttreatment of sodium arsenite is cogenotoxic.
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PMID:Differential effects of pre- and posttreatment of sodium arsenite on the genotoxicity of methyl methanesulfonate in Chinese hamster ovary cells. 375 97

The influence of inhibitors of poly(ADP-ribose) polymerase such as 3-aminobenzamide (3AB) and benzamide (B) on the spontaneously occurring as well as mutagen induced chromosomal aberrations, sister chromatid exchanges (SCEs) and point mutations has been studied. In addition, we have measured the influence of 3AB on DNA repair following treatment with physical and chemical mutagens. Post treatment of X-irradiated mammalian cells with 3AB increases the frequencies of induced chromosomal aberrations by a factor of 2 to 3. Both acentric fragments and exchanges increase indicating that the presence of 3AB slows down the repair of DNA strand breaks (probably DNA double strand breaks), thus making breaks available for interaction with each other to give rise to exchanges. 3AB, when present in the medium containing bromodeoxyuridine(BrdUrd) during two cell cycles, increases the frequencies of SCEs in Chinese hamster ovary cells (CHO) in a concentration dependent manner leading to about a 10-fold increase at 10 mM concentration. Most 3AB induced SCEs occur during the second cell cycle, in which DNA containing bromouridine (BU) is used as template for replication. BU containing DNA appears to be prone to errors during replication. The extent of increase in the frequencies of SCEs by 3AB is correlated with the amount of BU incorporated in the DNA of the cells. The frequencies of spontaneously occurring DNA single strand breaks in cells grown in BrdUrd containing medium are higher than in the cells grown in normal medium and this increase depends on the amount of BU incorporated in the DNA of these cells. We have studied the extent of increase in the frequencies of SCEs due to 1 mM 3AB in several human cell lines, including those derived from patients suffering from genetic diseases such as ataxia telangiectasia (A-T), Fanconi's anemia (FA), and Huntington's chorea. None of these syndromes showed any increased response when compared to normal cells. 3AB, however, increased the frequencies of spontaneously occurring chromosomal aberrations in A-T and FA cells. 3AB does not influence the frequencies of SCEs induced by UV or mitomycin C (MMC) in CHO cells. However, it increases the frequencies of SCEs induced by ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS). Under the conditions in which 3AB increases the frequencies of spontaneously occurring as well as induced SCEs, it does not increase the frequencies of point mutations in hypoxanthine-guanine phosphoribosyltransferase (HGPRT) locus. 3AB does not influence the amount of repair replication following dimethylsulphate (DMS) treatment of human fibroblasts, or UV irradiated human lymphocytes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Influence of inhibitors of poly(ADP-ribose) polymerase on DNA repair, chromosomal alterations, and mutations. 631 38

Using a multi-locus minisatellite Per-6 DNA probe, we performed DNA fingerprint analysis. Chinese hamster lung (CHL) cells were treated with six model chemicals: N-methyl-N'-nitro-N-nitrosoguanidine, mitomycin C, methyl methanesulfonate, furylfuramide, 2-acetylamino-fluorene, and cyclophosphamide, with or without S9 mix. 771 hypoxanthine phosphoribosyltransferase deficient clones (749 from mutagen-treated cells and 22 from untreated cells) and 90 unselected clones from untreated cells were isolated and analyzed. The spontaneous mutation frequency at CHL cell minisatellite loci was 0.31-0.63%. All the chemicals increased mutation frequencies. Almost all mutations localized to the three specific minisatellite loci corresponding to 4.2, 3.8, and 2.4 kb bands, suggesting that these regions are more unstable and susceptible to mutation. DNA fingerprint analysis is a promising technique for detecting mutations at neutral DNA regions, especially recombinational mutations, and may be useful for surveying genetic instability related to heritable defects or aging.
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PMID:DNA fingerprint analysis in chemically mutagenized Chinese hamster lung cells. 756 85

A major portion of new cases of cancer may be linked to environmental carcinogens. The Ames (Salmonella) test is currently the most widely used short-term test to predict carcinogenic properties of compounds. However, approximately 50% of all carcinogens have been sufficiently tested in long-term animal bioassays do not induce mutations in the Salmonella assay, and many of these carcinogens are also not detectable by other short-term assays. In the work described here we determined the effect of carcinogen exposure on intrachromosomal recombination in a human cell line. The recombination events caused the deletion of one copy of a duplication of exons 2 and 3 of the hprt gene. We found that these deletion events were induced by exposure to the Salmonella assay positive carcinogens UV, gamma-rays and methyl methanesulfonate, as well as the Salmonella assay negative carcinogens Aroclor 1221, benzene and thiourea. These data may further support the accumulating evidence that recombination and deletions may be important in carcinogenesis.
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PMID:Carcinogens induce intrachromosomal recombination in human cells. 758 7

The radiosensitive Chinese hamster cell line XR-V15B was used to study the effect of decreased rejoining of DNA double-strand breaks (DSBs) on gene mutations and chromosome aberrations. XR-V15B cells are hypersensitive to the cytotoxic effects of neocarzinostatin (NCS) and methyl methanesulfonate (MMS). Both mutagens induced more chromosome aberrations in XR-V15B cells than in the parental cell strain. The clastogenic action of NCS was characterized by the induction of predominantly chromosome-type aberrations in cells of both strains, whereas MMS induced mainly chromatid aberrations. The frequency of induced gene mutations at the hprt locus was not increased compared to the parental V79 cells when considering the same survival level. Molecular analysis by multiplex polymerase chain reaction (PCR) of mutants induced by NCS revealed a high frequency of deletions in cells of both cell lines. Methyl methane-sulfonate induced mainly mutations without visible changes in the PCR pattern, which probably represent point mutations. Our findings suggest a link between a defect in DNA DSB repair and increased cytotoxic and clastogenic effects. However, a decreased ability to rejoin DNA DSBs does not seem to influence the incidence and types of gene mutations at the hprt locus induced by NCS and MMS.
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PMID:The effect of defective DNA double-strand break repair on mutations and chromosome aberrations in the Chinese hamster cell mutant XR-V15B. 763 Oct 7


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