Isolation of mutants of CHO cells resistant to 6 (p-hydroxyphenylazo)-uracil II. Mutants auxotrophic for deoxypyrimidines |
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Authors: | Enrico Arpaia Peter N. Ray Louis Siminovitch |
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Affiliation: | 1. Department of Medical Genetics, University of Toronto and The Hospital for Sick Children, 555 University Avenue, M5G 1X8, Toronto, Ontario, Canada
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Abstract: | Two classes of CHO mutants resistant to the drug 6(p-hydroxyphenylazo)-uracil have been characterized. Both classes exhibited a nutritional requirement that could be satisfied by deoxypyrimidines and uridine but not other ribopyrimidines. A biochemical investigation of these mutants revealed a structural defect in ribonucleotide reductase resulting in a two- to fourfold increase in the Km for UDP and CDP. As a consequence of this lesion, the cells had imbalanced deoxypyrimidine pools and showed an increase in the rate of spontaneous mutation to 6-thioguanine resistance but not emetine resistance. |
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