Bressan D A, Olivares H A, Nelms B E, Petrini J H
Laboratory of Genetics, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA.
Genetics. 1998 Oct;150(2):591-600. doi: 10.1093/genetics/150.2.591.
Saccharomyces cerevisiae Mre11, Rad50, and Xrs2 function in a protein complex that is important for nonhomologous recombination. Null mutants of MRE11, RAD50, and XRS2 are characterized by ionizing radiation sensitivity and mitotic interhomologue hyperrecombination. We mutagenized the four highly conserved phosphoesterase signature motifs of Mre11 to create mre11-11, mre11-2, mre11-3, and mre11-4 and assessed the functional consequences of these mutant alleles with respect to mitotic interhomologue recombination, chromosome loss, ionizing radiation sensitivity, double-strand break repair, and protein interaction. We found that mre11 mutants that behaved as the null were sensitive to ionizing radiation and deficient in double-strand break repair. We also observed that these null mutants exhibited a hyperrecombination phenotype in mitotic cells, consistent with previous reports, but did not exhibit an increased frequency of chromosome loss. Differential ionizing radiation sensitivities among the hypomorphic mre11 alleles correlated with the trends observed in the other phenotypes examined. Two-hybrid interaction testing showed that all but one of the mre11 mutations disrupted the Mre11-Rad50 interaction. Mutagenesis of the phosphoesterase signatures in Mre11 thus demonstrated the importance of these conserved motifs for recombinational DNA repair.
酿酒酵母的Mre11、Rad50和Xrs2在一个对非同源重组很重要的蛋白质复合物中发挥作用。MRE11、RAD50和XRS2的缺失突变体表现出对电离辐射敏感以及有丝分裂同源染色体间超重组的特征。我们对Mre11的四个高度保守的磷酸二酯酶特征基序进行诱变，创建了mre11-11、mre11-2、mre11-3和mre11-4，并评估了这些突变等位基因在有丝分裂同源染色体间重组、染色体丢失、电离辐射敏感性、双链断裂修复和蛋白质相互作用方面的功能后果。我们发现表现为缺失型的mre11突变体对电离辐射敏感且双链断裂修复存在缺陷。我们还观察到这些缺失突变体在有丝分裂细胞中表现出超重组表型，这与之前的报道一致，但未表现出染色体丢失频率增加。亚效等位基因mre11之间不同的电离辐射敏感性与在其他所检测表型中观察到的趋势相关。双杂交相互作用测试表明，除一个mre11突变外，其他所有突变均破坏了Mre11-Rad50相互作用。因此，对Mre11中磷酸二酯酶特征基序的诱变证明了这些保守基序对重组DNA修复的重要性。
