Guerrero I, Villasante A, Corces V, Pellicer A
Science. 1984 Sep 14;225(4667):1159-62. doi: 10.1126/science.6474169.
Mouse tumors induced by gamma radiation are a useful model system for oncogenesis. DNA from such tumors contains an activated K-ras oncogene that can transform NIH 3T3 cells. This report describes the cloning of a fragment of the mouse K-ras oncogene containing the first exon from both a transformant in rat-2 cells and the brain of the same mouse that developed the tumor. Hybrid constructs containing one of the two pieces were made and only the plasmid including the first exon from the transformant gave rise to foci in NIH 3T3 cells. There was only a single base difference (G----A) in the exonic sequence, which changed glycine to aspartic acid in the transformant. By use of a synthetic oligonucleotide the presence of the mutation was demonstrated in the original tumor, ruling out modifications during DNA-mediated gene transfer and indicating that the alteration was present in the thymic lymphoma but absent from other nonmalignant tissue. The results are compatible with gamma radiation being a source of point mutations.
γ射线诱导的小鼠肿瘤是肿瘤发生研究中一种有用的模型系统。此类肿瘤的DNA含有一个可转化NIH 3T3细胞的活化K-ras癌基因。本报告描述了从小鼠K-ras癌基因中克隆出一个包含第一个外显子的片段，该片段来自大鼠-2细胞中的一个转化体以及产生肿瘤的同一只小鼠的大脑。构建了包含这两个片段之一的杂交质粒，只有包含来自转化体的第一个外显子的质粒能在NIH 3T3细胞中形成集落。外显子序列中只有一个碱基差异（G→A），该差异使转化体中的甘氨酸变为天冬氨酸。通过使用合成寡核苷酸，在原始肿瘤中证实了该突变的存在，排除了DNA介导的基因转移过程中的修饰，并表明该改变存在于胸腺淋巴瘤中，而在其他非恶性组织中不存在。这些结果与γ射线是点突变的来源这一观点相符。
