Meuth M, L'Heureux-Huard N, Trudel M
Proc Natl Acad Sci U S A. 1979 Dec;76(12):6505-9. doi: 10.1073/pnas.76.12.6505.
We have recently reported the isolation of a class of mutants (called thy-) that is both resistant to arabinosyl cytosine and auxotrophic for thymidine. thy- mutants have a 5- to 10-fold elevated pool of dCTP and are deficient in the synthesis of dTTP as an apparent consequence of a single mutation in the gene for ribonucleoside-diphosphate reductase (2'-deoxyribonucleoside-diphosphate:oxidized-thioredoxin 2'-oxidoreductase, EC 1.17.4.1). Here we show that three independent thy- lines have a 5- to 50-fold higher frequency and rate of spontaneous mutation for two genetic markers, 6-thioguanine resistance and ouabain resistance. The higher rate of mutation is site specific because two other genetic markers, reversion of proline auxotrophy to proline prototrophy and emetine resistance, are unaffected. Ouabain- and 6-thioguanine-resistant mutations occur at a much lower rate in revertants of thy- to the wild-type state, so the increased rate of mutation is the consequence of the thy- mutation. Both the increased mutational rate and the increased intracellular pools of dCTP are dominant or codominant in hybrid cells, and alterations of the ratio of the pools of dCTP to dTTP in thy- 49 produce corresponding changes in the rate of mutation. Thus, thy- is a mutator gene in Chinese hamster ovary cells, apparently as a consequence of the imbalance of deoxynucleoside triphosphate pools created by the expanded pool of dCTP.
我们最近报道了一类突变体（称为thy-）的分离，这类突变体对阿糖胞苷具有抗性且对胸苷营养缺陷。thy-突变体的dCTP池升高了5至10倍，并且由于核糖核苷二磷酸还原酶（2'-脱氧核糖核苷二磷酸：氧化型硫氧还蛋白2'-氧化还原酶，EC 1.17.4.1）基因中的单个突变，dTTP的合成存在缺陷。在此我们表明，三个独立的thy-品系对于两种遗传标记物，即6-硫鸟嘌呤抗性和哇巴因抗性，具有自发突变频率和速率高5至50倍的情况。较高的突变率是位点特异性的，因为另外两个遗传标记物，脯氨酸营养缺陷型回复为脯氨酸原养型和依米丁抗性，未受影响。在thy-回复为野生型状态的回复体中，哇巴因和6-硫鸟嘌呤抗性突变的发生率要低得多，因此突变率的增加是thy-突变的结果。在杂交细胞中，增加的突变率和增加的dCTP细胞内池都是显性或共显性的，并且在thy- 49中dCTP池与dTTP池的比例变化会导致突变率产生相应变化。因此，thy-是中国仓鼠卵巢细胞中的一个诱变基因，显然是由dCTP池扩大导致的脱氧核苷三磷酸池失衡的结果。
