Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neocarzinostatin (NCS) is mutagenic in bacteria, yeast, fungi, and mammalian cells. In cell-free systems, DNA strand breakage induced by NCS requires a reducing agent like 2-mercaptoethanol, unless very high (greater than 100 micrograms/ml) concentrations of NCS are used. In this study, we have investigated the role of the sulfhydryl compound glutathione (GSH), which is usually the most common intracellular thiol, in the bioactivation of NCS to a toxic and mutagenic species. Chinese hamster V79 cells were pretreated with one of two GSH depleting agents, buthionine sulfoximine or diethyl maleate. These agents deplete GSH via different mechanisms, but both will lower GSH levels within the cell to less than 5% of control (untreated) values. GSH-depleted cells and control cells were then exposed to NCS concentrations of 0.5-2.5 micrograms/ml for 1 h, assayed for survival, and plated for expression of hypoxanthine-guanine phosphoribosyltransferase-negative (HGPRT-) mutants. After an expression period of 7 days, during which the cultures were subcultured twice, HGPRT- mutants were selected by plating in hypoxanthine-free medium containing 5 micrograms of 6-thioguanine per ml, at a density of 2 X 10(5) cells per 100 mm dish. NCS alone decreased the surviving fraction to about 1% at 2.5 micrograms/ml and produced dose-related increases in HGPRT-mutants that reached greater than 10 times the spontaneous mutation frequency at 2.5 micrograms NCS per ml. In GSH-depleted cells, however, NCS was only mildly cytotoxic (60-80% surviving fraction) and did not produce dose-related increases in HGPRT- mutants over cells treated only with diethyl maleate or buthionine sulfoximine. Thus, GSH appears to be the main reducing agent for the bioactivation of NCS to a toxic and mutagenic species in Chinese hamster V79 cells.
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PMID:Glutathione dependence of neocarzinostatin cytotoxicity and mutagenicity in Chinese hamster V-79 cells. 316 10

Spontaneous mutations and neocarzinostatin-induced mutations were investigated in the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene in exponentially growing Chinese hamster ovary cells. Neocarzinostatin (NCS) treatment caused an 4.5-fold increase in mutation frequency. Analysis by multiplex polymerase chain reaction and sequencing of hprt cDNA revealed that spontaneous mutations in this system were characterized by a relatively high rate of large deletions and double-base substitutions, and a low rate of splice mutations compared with data reported in fibroblastic cell lines. NCS hardly affected this spectrum of spontaneous mutations, which indicates the rare incidence of NCS-specific change in the exponential growth phase. This is in contrast to aprt gene mutations reported in plateau phase cells in which base substitutions occur preferentially at sites affected by NCS. These results suggest that differences in the loci assayed or in the processes involved in mammalian mutagenesis in the exponential growth phase and the plateau phase may be the source of the different results.
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PMID:Neocarzinostatin-induced mutations at the hprt locus in exponentially growing CHO cells, compared with spontaneous mutations. 963 64