Harris S D, Pringle J R
Department of Biology, University of Michigan, Ann Arbor 48109.
Genetics. 1991 Feb;127(2):279-85. doi: 10.1093/genetics/127.2.279.
In a previous attempt to identify as many as possible of the essential genes on Saccharomyces cerevisiae chromosome I, temperature-sensitive (Ts-) lethal mutations that had been induced by ethyl methane-sulfonate or nitrosoguanidine were analyzed. Thirty-two independently isolated mutations that mapped to chromosome I identified only three complementation groups, all of which had been known previously. In contrast, molecular analyses of segments of the chromosome have suggested the presence of numerous additional essential genes. In order to assess the degree to which problems of mutagen specificity had limited the set of genes detected using Ts- lethal mutations, we isolated a new set of such mutations after mutagenesis with UV or nitrogen mustard. Surprisingly, of 21 independently isolated mutations that mapped to chromosome I, 17 were again in the same three complementation groups as identified previously, and two of the remaining four mutations were apparently in a known gene involved in cysteine biosynthesis. Of the remaining two mutations, one was in one of the essential genes identified in the molecular analyses, and the other was too leaky to be mapped. These results suggest that only a minority of the essential genes in yeast can be identified using Ts- lethal mutations, regardless of the mutagen used, and thus emphasize the need to use multiple genetic strategies in the investigation of cellular processes.
在先前一次尽可能鉴定出酿酒酵母1号染色体上必需基因的尝试中，对由甲基磺酸乙酯或亚硝基胍诱导产生的温度敏感（Ts-）致死突变进行了分析。定位到1号染色体上的32个独立分离的突变仅鉴定出3个互补群，所有这些互补群此前均已为人所知。相比之下，对该染色体片段的分子分析表明存在许多其他必需基因。为了评估诱变特异性问题在多大程度上限制了使用Ts-致死突变检测到的基因集，我们在用紫外线或氮芥诱变后分离出了一组新的此类突变。令人惊讶的是，在定位到1号染色体上的21个独立分离的突变中，有17个再次位于先前鉴定出的相同3个互补群中，其余4个突变中的2个显然位于一个参与半胱氨酸生物合成的已知基因中。在其余2个突变中，一个位于分子分析中鉴定出的必需基因之一中，另一个渗漏性太强而无法定位。这些结果表明，无论使用何种诱变剂，利用Ts-致死突变只能鉴定出酵母中少数必需基因，因此强调了在细胞过程研究中需要使用多种遗传策略。
