Bressan D A, Baxter B K, Petrini J H
Laboratory of Genetics, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA.
Mol Cell Biol. 1999 Nov;19(11):7681-7. doi: 10.1128/MCB.19.11.7681.
Saccharomyces cerevisiae mre11Delta mutants are profoundly deficient in double-strand break (DSB) repair, indicating that the Mre11-Rad50-Xrs2 protein complex plays a central role in the cellular response to DNA DSBs. In this study, we examined the role of the complex in homologous recombination, the primary mode of DSB repair in yeast. We measured survival in synchronous cultures following irradiation and scored sister chromatid and interhomologue recombination genetically. mre11Delta strains were profoundly sensitive to ionizing radiation (IR) throughout the cell cycle. Mutant strains exhibited decreased frequencies of IR-induced sister chromatid and interhomologue recombination, indicating a general deficiency in homologous recombination-based DSB repair. Since a nuclease-deficient mre11 mutant was not impaired in these assays, it appears that the role of the S. cerevisiae Mre11-Rad50-Xrs2 protein complex in facilitating homologous recombination is independent of its nuclease activities.
酿酒酵母mre11Δ突变体在双链断裂（DSB）修复方面存在严重缺陷，这表明Mre11-Rad50-Xrs2蛋白复合体在细胞对DNA双链断裂的应答中起核心作用。在本研究中，我们检测了该复合体在同源重组（酵母中DSB修复的主要方式）中的作用。我们测定了辐照后同步培养物中的存活率，并通过遗传学方法对姐妹染色单体和同源染色体间的重组进行了评分。mre11Δ菌株在整个细胞周期中对电离辐射（IR）都极为敏感。突变菌株中IR诱导的姐妹染色单体和同源染色体间重组频率降低，表明基于同源重组的DSB修复普遍存在缺陷。由于核酸酶缺陷型mre11突变体在这些实验中未受影响，看来酿酒酵母Mre11-Rad50-Xrs2蛋白复合体在促进同源重组中的作用与其核酸酶活性无关。
