X-ray induction of 8-azaguanine-resistant mutants in synchronous Chinese hamster ovary cells.
X-ray induction of 8-azaguanine-resistant mutants in synchronous Chinese hamster ovary cells.
复制标题
同步中国仓鼠卵巢细胞中 8-氮鸟嘌呤抗性突变体的 X 射线诱导。
作者：
R. Jostes;K. Bushnell;W. Dewey
通过有丝分裂选择获得的同步中国仓鼠卵巢细胞在细胞周期的各个点进行X射线照射，并分析了8-氮鸟嘌呤（AG）耐药突变体的频率。诱导频率在有丝分裂（40 x 10/sup-5/5戈伊）、早期G/sub 1/（30 x 10/sup-5/）和G/sub 1//S边界（30 x 10/sup-5/）中最高;在中期至晚期G/sub 1/（15 x 10/sup-5/）中较低;在S期（6 x 10/sup-5/）中最低。定性而言，细胞周期中诱导突变体的敏感性变化与诱导染色体畸变的报告一致。然而，两个终点的定量比较和存活对数与突变频率或畸变频率的曲线图表明，当细胞在有丝分裂或在G/sub 1//S边界照射时，突变频率远高于预期。观察到一系列突变体，并将其分类为完全突变，即，不能在氮杂丝氨酸-次黄嘌呤培养基中存活并以低于野生型细胞的1%的速率掺入（/sup 3/H）次黄嘌呤（（/sup 3/H）Hx），或作为部分掺入，即，在氮杂丝氨酸-次黄嘌呤培养基中存活并以大于野生型细胞的1%的速率掺入（/sup 3/H）Hx。在30个品种中，被归类为部分突变体的比例为0 - 22%。Mu.. g/ml AG和15 ~ 60%的选择率。Mu.. g/ml AG。然而，部分相对于完整的突变体的数量没有或很少依赖于辐射剂量或照射的细胞周期的阶段。17个突变体（10个部分突变体和7个完全突变体）在AG不存在下培养12至33周，并且如通过AG抗性或（/sup 3/H）Hx的摄取所测定的，只有一个部分突变体恢复为野生型。此外，完全突变体和部分突变体对6-硫鸟嘌呤具有抗性。«少
Synchronous Chinese hamster ovary cells obtained by mitotic selection were x-irradiated at various points in the cell cycle and were analyzed for the frequency of mutants resistant to 8-azaguanine (AG). The induced frequencies were highest in mitosis (40 x 10/sup -5/ for 5 Gy), in early G/sub 1/ (30 x 10/sup -5/), and at the G/sub 1//S border (30 x 10/sup -5/); were low in mid- to late G/sub 1/ (15 x 10/sup -5/); and were lowest in S phase (6 x 10/sup -5/). Qualitatively, the variation in sensitivity during the cell cycle for induction of mutants corresponded with that reported for induction of chromosomal aberrations. However, a quantitative comparison of the two endpoints and plots of the logarithm of survival versus mutant frequencies or aberration frequencies indicates that the mutant frequencies were much higher than expected when the cells were irradiated in mitosis or at the G/sub 1//S border. A spectrum of mutants was observed and classified either as complete, i.e., failing to survive in azaserine-hypoxanthine medium and incorporating (/sup 3/H)hypoxanthine ((/sup 3/H)Hx) at a rate less than 1% of that for wild-type cells, or as partial, i.e., surviving in azaserine-hypoxanthine medium and incorporating (/sup 3/H)Hx at a ratemore » grater than 1% of that for wild-type cells. THe percentage of mutants classified as partials was 0 to 22% for selection in 30 ..mu..g/ml AG and 15 to 60% for selection in 5 ..mu..g/ml AG. However, the number of partial relative to complete mutants had no or little dependence on radiation dose or phase of the cell cycle irradiated. Seventeen mutants (10 partials and 7 completes) were cultured for 12 to 33 weeks in the absence of AG, and only one partial reverted to wild type as assayed by AG resistance or uptake of (/sup 3/H)Hx. Furthermore, the complete mutants and some of the partials were resistant to 6-thioguanine.« less