Fedorova I V, Gracheva L M, Kovaltzova S V, Evstuhina T A, Alekseev S Y, Korolev V G
B. P. Konstantinov Petersburg Nuclear Physics Institute, Russian Academy of Science, Gatchina, Leningrad District.
Genetics. 1998 Mar;148(3):963-73. doi: 10.1093/genetics/148.3.963.
Mutants with enhanced spontaneous mutability (hsm) to canavanine resistance were induced by N-methyl-N-nitrosourea in Saccharomyces cerevisiae. One bearing the hsm3-1 mutation was used for this study. This mutation does not increase sensitivity to the lethal action of different mutagens. The hsm3-1 mutation produces a mutator phenotype, enhancing the rates of spontaneous mutation to canavanine resistance and reversions of lys1-1 and his1-7. This mutation increases the rate of intragenic mitotic recombination at the ADE2 gene. The ability of the hsm3 mutant to correct DNA heteroduplex is reduced in comparison with the wild-type strain. All these phenotypes are similar to ones caused by pms1, mlhl and msh2 mutations. In contrast to these mutations, hsm3-1 increases the frequency of ade mutations induced by 6-HAP and UV light. Epistasis analysis of double mutants shows that the PMS1 and HSM3 genes control different mismatch repair systems. The HSM3 gene maps to the right arm of chromosome II, 25 cM distal to the HIS7 gene. Strains that bear a deleted open reading frame YBR272c have the genetic properties of the hsm3 mutant. The HSM3 product shows weak similarity to predicted products of the yeast MSH genes (homologs of the Escherichia coli mutS gene). The HSM3 gene may be a member of the yeast MutS homolog family, but its function in DNA metabolism differs from the functions of other yeast MutS homologs.
用N-甲基-N-亚硝基脲在酿酒酵母中诱导出对刀豆氨酸抗性具有增强的自发突变率（hsm）的突变体。本研究使用了一个携带hsm3-1突变的突变体。该突变不会增加对不同诱变剂致死作用的敏感性。hsm3-1突变产生了一个诱变表型，提高了对刀豆氨酸抗性的自发突变率以及lys1-1和his1-7的回复突变率。该突变增加了ADE2基因处的基因内有丝分裂重组率。与野生型菌株相比，hsm3突变体纠正DNA异源双链的能力降低。所有这些表型都与由pms1、mlhl和msh2突变引起的表型相似。与这些突变不同的是，hsm3-1增加了由6-HAP和紫外线诱导的ade突变的频率。双突变体的上位性分析表明，PMS1和HSM3基因控制不同的错配修复系统。HSM3基因定位于染色体II的右臂，在HIS7基因远端25 cM处。携带缺失的开放阅读框YBR272c的菌株具有hsm3突变体的遗传特性。HSM3产物与酵母MSH基因（大肠杆菌mutS基因的同源物）的预测产物显示出弱相似性。HSM3基因可能是酵母MutS同源物家族的成员，但其在DNA代谢中的功能不同于其他酵母MutS同源物的功能。
