Miller J H, Lebkowski J S, Greisen K S, Calos M P
EMBO J. 1984 Dec 20;3(13):3117-21. doi: 10.1002/j.1460-2075.1984.tb02267.x.
DNA transfected into mammalian cells is subject to the high mutation frequency of approximately 1% per gene. We present data bearing on the derivation of the two main classes of mutations detected, base substitutions and deletions. The DNA sequence change is reported for nearly 100 independent base substitution mutations that occurred in shuttle vectors as a result of passage in simian cells. All of the mutations occur at G:C base pairs and involve either transition to A:T or transversion to T:A. To identify possible mutational intermediates, various topological forms of the vector DNA were introduced separately. Supercoiled and relaxed DNA are mutated at equal frequencies. However, linearized DNA leads to a greatly elevated frequency of deletions. Nicked and gapped templates stimulate both deletions and base substitutions. We discuss a model involving intracellular degradation of the transfected DNA which explains these observations.
转染到哺乳动物细胞中的DNA每个基因的突变频率约为1%，突变频率很高。我们展示了与检测到的两类主要突变（碱基替换和缺失）的起源相关的数据。报告了近100个独立的碱基替换突变导致穿梭载体在猴细胞中传代时发生的DNA序列变化。所有突变都发生在G:C碱基对处，要么转变为A:T，要么颠换为T:A。为了识别可能的突变中间体，分别引入了载体DNA的各种拓扑形式。超螺旋DNA和松弛DNA的突变频率相同。然而，线性化DNA会导致缺失频率大幅升高。带切口和缺口的模板会同时刺激缺失和碱基替换。我们讨论了一个涉及转染DNA细胞内降解的模型，该模型解释了这些观察结果。
