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)

We have investigated the roles of reactive oxygen species (ROS) in bleomycin (BLM)-induced gene mutations in Chinese hamster ovary (CHO) cells using a superoxide dismutase (SOD) inhibitor, triethylenetetramine (TRIEN), and a SOD mimic, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEM-POL), to lower and increase intracellular 'SOD activity', respectively. Pretreatment of CHO cells with TRIEN (1 mM) for 1 h enhanced the mutagenic response of BLM (5-50 micrograms/ml, 1 h treatment) in the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in CHO cell clone K1-BH4 (CHO/HPRT assay) and the xanthine-guanine phosphoribosyltransferase (gpt) gene in a CHO-K1 cell derivative AS52 (AS52/GPT assay). Pretreatment with TEMPOL (1 mM) for 1 h decreased the BLM (20-100 micrograms/ml, 1 h treatment) mutagenicity in the AS52/GPT assay. The mutagenic response of BLM appears to be modulated by the intracellular level of 'SOD activity' and hence the intracellular level of ROS. These data provide further evidence for the involvement of ROS in bleomycin mutagenesis in mammalian cells.
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PMID:Effects of an inhibitor and a mimic of superoxide dismutase on bleomycin mutagenesis in Chinese hamster ovary cells. 138 33

We have studied the mutagenicity and toxicity of physical and chemical agents in the Chinese hamster ovary (CHO) cell line K1-BH4 and its transformant, AS52. The AS52 cells lack the normal X-linked mammalian hypoxanthine-guanine phosphoribosyltransferase (hprt) gene but instead contain a single autosomally integrated copy of the bacterial equivalent, the xanthine-guanine phosphoribosyltransferase (gpt) gene. We found that X-rays and neutrons appear to be equitoxic to both cell types; however, these physical agents are approximately 10 times more mutagenic to the gpt gene of AS52 cells than to the hprt gene of K1-BH4 cells. We reasoned that if reactive oxygens were to mediate the mutagenic effects of both radiomimetic chemicals and radiation, then reactive oxygen-producing chemicals, such as streptonigrin and bleomycin, and oxidizing agents such as potassium superoxide and hydrogen peroxide, would exhibit similar levels of toxicity but different frequencies of mutants when assayed with the two cell lines. Our experiments fulfill such predictions. We postulate that the apparent hypermutability of AS52 cells probably results from a higher recovery of multi-locus deletion mutants in AS52 cells than in K1-BH4 cells, rather than a higher yield of induced mutants. Preliminary studies, using Southern blot and the polymerase chain reaction to analyze the mutational spectrum of the mutants, support our hypothesis that reactive oxygens induce deletion mutations in mammalian cells.
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PMID:Molecular analysis of reactive oxygen-species-induced mammalian gene mutation. 197 50

We have studied the mutagenicity (by selecting for mutants resistant to 6-thioguanine) and cytotoxicity (by determining cellular cloning efficiency) of physical and chemical agents in Chinese hamster ovary (CHO) cells, clone CHO-K1-BH4 (K1-BH4), and its radiation-hypersensitive transformant, AS52. AS52 cells contain a single functional copy of a bacterial gene, the xanthine/guanine phosphoribosyltransferase (gpt) gene instead of its mammalian equivalent, the hypoxanthine/guanine phosphoribosyltransferase (hprt) gene. We found that x-ray and neutron irradiations are equally toxic to both cell types; however, these physical agents are approximately equal to 10 times more mutagenic to AS52 cells than to K1-BH4 cells. Our earlier studies using Southern blot analysis showed that x-irradiation produces mostly or exclusively deletion mutations in both cell types. If reactive oxygen species mediate the mutagenic effects of radiations and chemicals, then radiomimetic compounds such as streptonigrin and bleomycin, which exert their biological effects via reactive oxygen species, and oxidizing compounds such as potassium superoxide and hydrogen peroxide should elicit a similar differential mutagenic response in both cell types. On the other hand, agents such as ethyl methanesulfonate, ICR 191, and UV light, which do not produce reactive oxygen species, should not elicit differential mutagenicity. Our results fulfill such predictions. The apparent hypermutability of AS52 cells probably results from a higher recovery of multilocus deletion mutants in AS52 cells than in K1-BH4 cells, rather than a higher yield of induced mutants.
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PMID:Evidence for reactive oxygen species inducing mutations in mammalian cells. 243 98

We have developed a system to study mutations which affect expression of the E. coli xanthine-guanine phosphoribosyl transferase (XPRT) gene (gpt) in hypoxanthine-guanine phosphoribosyl transferase-deficient (HPRT-) Chinese hamster ovary (CHO) cells that have been transformed by the plasmid pSV2gpt. Several gpt-transformed cell lines have been isolated and characterized with respect to integrated pSV2gpt sequences, expression of the gpt gene, and cytotoxic and mutagenic responses to UV light. While the gpt-transformed CHO and wild-type CHO-K1-BH4 cell lines have similar cytotoxic responses to UV light, the gpt-transformed cell lines respond differently from the parental CHO-K1-BH4 cell line in terms of mutation induction. As with CHO-K1-BH4 HPRT mutants, spontaneous or induced XPRT mutants derived from the gpt+ cell lines can be selected for 6-thioguanine resistance (TGr). Analysis of cell-free extracts from a number of these TGr clones indicates that the mutant phenotype is due to the absence of XPRT activity. One transformant, designated AS52, has previously been described in limited detail. Here we describe additional characteristics of this cell line, as well as several related transformants.
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PMID:Analyses of mutation in pSV2gpt-transformed CHO cells. 300 50

2-Methoxyethanol (ethylene glycol monomethyl ether) (EGME), is one of the most commonly used solvents for industrial and consumer products. Although the solvent has been shown to be a reproductive toxin the genotoxic activities of EGME especially its metabolites, have not been adequately investigated. The mutagenicity and cytotoxicity of EGME and its major metabolites, methoxyacetaldehyde (MALD) and methoxyacetic acid (MAA) in Chinese hamster ovary (CHO) cells were therefore examined by us. We have determined the mutagenicity of these compounds at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in CHO-K1-BH4 cells (CHO/HPRT assay) and the xanthine-guanine phosphoribosyl transferase (gpt) locus in CHO AS52 cells (AS52/GPT assay). The results show that these chemicals are not mutagenic to the hprt locus in CHO-K1-BH4 cells either with or without rat liver S9 mix as the metabolic activating system. With AS52 cells, only MALD is mutagenic in the absence of S9. It induced a dose-dependent mutagenic response. A dose-dependent cytotoxicity was induced by all compounds in both cell lines. MALD is the most and EGME is the least cytotoxic compounds. Our study shows that a metabolite of EGME, MALD, is highly cytotoxic and likely induces deletion-type mutations in AS52 cells. The genotoxic effect of EGME is, therefore, dependent upon its metabolism and its detection is dependent upon the assays used.
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PMID:Mutagenicity and cytotoxicity of 2-methoxyethanol and its metabolites in Chinese hamster cells (the CHO/HPRT and AS52/GPT assays). 767 57

Bleomycin-induced 6-thioguanine-resistant mutants pretreated with or without TRIEN (triethylenetetramine), a superoxide dismutase (SOD) inhibitor, or TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), an SOD mimic, were analyzed by polymerase chain reaction (PCR)-based deletion screening in a Chinese hamster ovary (CHO) clone K1-BH4 and its derivative AS52 cells. As we proposed earlier, TRIEN would decrease and TEMPOL would increase the intracellular level of hydroxyl radical leading to a higher and lower recovery of deletion mutants. We found that the proportion of the deletion mutants induced by bleomycin at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in K1-BH4 cells was 45.5% (25/55). The proportion of deletion HPRT- mutants induced by bleomycin pretreated with TRIEN was 31.0% (9/29) and with TEMPOL was 50.0% (14/28). The proportion of deletion mutants induced by bleomycin on the xanthine-guanine phosphoribosyltransferase (gpt) gene in AS52 cells was 61.0% (36/59). The proportion of deletion GPT- mutants induced by bleomycin pretreated with TRIEN was 56.8% (21/37) and with TEMPOL was 61.4% (27/44). The trend of the change of the proportion of bleomycin-induced deletion mutants as affected by TRIEN and by TEMPOL provides molecular evidence for the involvement of reactive oxygen species (ROS) in bleomycin mutagenesis in mammalian cells, in which deletion is a major type of induced mutation.
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PMID:Polymerase chain reaction-based deletion screening of bleomycin induced 6-thioguanine-resistant mutants in Chinese hamster ovary cells: the effects of an inhibitor and a mimic of superoxide dismutase. 769 Aug 90

Mammalian cells in culture have been used to study the genetic effects of physical and chemical agents. We have used Chinese hamster ovary (CHO) cells, clone K1-BH4, to quantify mutations at the X-linked, large (35 kb) hypoxanthine-guanine phosphoribosyltransferase (hprt) locus (the CHO/HPRT assay) induced by environmental agents. By transfecting an hprt-deletion mutant CHO cell line with the plasmid vector pSV2gpt, we isolated a transformant, AS52. AS52 cells carry a single functional copy of an autosomal, small (456 bp) xanthine-guanine phosphoribosyltransferase (gpt) gene (the bacterial equivalent of the mammalian hprt gene; AS52/GPT assay). We found that ionizing radiations such as X-rays and neutrons and oxidative genotoxic chemicals such as Adriamycin, bleomycin, hydrogen peroxide, and potassium superoxide are much more mutagenic to the gpt gene in AS52 cells than to the hprt locus in K1-BH4 cells. The hypermutability of the gpt gene probably results from a higher recovery of multilocus deletion mutants in AS52 cells than in K1-BH4 cells, rather than a higher yield of induced mutants. These results demonstrate that the use of the hprt locus alone could lead to an underestimate of the genetic risk of these agents. Analyses of the mutation spectrum using a polymerase chain reaction-based deletion screening and DNA sequencing procedure showed that a high proportion of HPRT- and GPT- mutants induced by X-rays carry deletion mutations. Thus, both the mutant frequency and mutation spectrum need to be considered in assessing the genetic risk of ionizing radiation and oxidative genotoxic chemicals.
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PMID:Quantitative and molecular analyses of genetic risk: a study with ionizing radiation. 814 20

Bleomycin is one of the radiomimetic antibiotics which induces DNA double-strand breaks by highly specific free radical attack on deoxyribose moieties in DNA. Earlier, we have shown that bleomycin induces a high proportion of large deletions involving one or more exons in the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in a Chinese hamster ovary (CHO) cell line CHO K1-BH4, in which no spontaneously occurring large deletions were detected by a polymerase chain reaction (PCR)-based deletion screening assay. Here we report the molecular nature of another class of mutants in which we did not observe any abnormal exon pattern. We refer to these mutants as the "nondeletion" type. Since bleomycin is a reactive oxygen species (ROS)-generating agent, we also studied whether the change of intracellular levels of ROS may affect the bleomycin-induced mutation spectra. We therefore also investigated the hprt mutation spectra induced by bleomycin with pretreatment by TRIEN (triethylenetetramine), a superoxide dismutase (SOD) inhibitor, and TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a SOD mimic. Analysis of these three bleomycin-induced "nondeletion" mutation spectra revealed that 5'-GTC-3' or 5'-GCC-3' sequences were the hot spots for single basepair deletions. Other types of mutation include abnormal cDNA or no cDNA amplification on the hprt locus. Due to the small sample size, we are unable to draw a definitive conclusion about the effects of TRIEN and TEMPOL on bleomycin-induced spectrum of "nondeletion" type hprt mutations.
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PMID:PCR-directed DNA sequencing of "nondeletion" HPRT-mutants induced by bleomycin in CHO K1-BH4 cells. 981 39