Jansson Kristina, Warringer Jonas, Farewell Anne, Park Han-Oh, Hoe Kwang-Lae, Kim Dong-Uk, Hayles Jacqueline, Sunnerhagen Per
Department of Cell and Molecular Biology, Lundberg Laboratory, Göteborg University, P.O. Box 462, Göteborg SE-405 30, Sweden.
Mutat Res. 2008 Sep 26;644(1-2):48-55. doi: 10.1016/j.mrfmmm.2008.07.001. Epub 2008 Jul 16.
The DNA glycosylase MutY is strongly conserved in evolution, and homologs are found in most eukaryotes and prokaryotes examined. This protein is implicated in repair of oxidative DNA damage, in particular adenine mispaired opposite 7,8-dihydro-8-oxoguanine. Previous investigations in Escherichia coli, fission yeast, and mammalian cells show an association of mutations in MutY homologs with a mutator phenotype and carcinogenesis. Eukaryotic MutY homologs physically associate with several proteins with a role in replication, DNA repair, and checkpoint signaling, specifically the trimeric 9-1-1 complex. In a genetic investigation of the fission yeast MutY homolog, myh1(+), we show that the myh1 mutation confers a moderately increased UV sensitivity alone and in combination with mutations in several DNA repair genes. The myh1 rad1, and to a lesser degree myh1 rad9, double mutants display a synthetic interaction resulting in enhanced sensitivity to DNA damaging agents and hydroxyurea. UV irradiation of myh1 rad1 double mutants results in severe chromosome segregation defects and visible DNA fragmentation, and a failure to activate the checkpoint. Additionally, myh1 rad1 double mutants exhibit morphological defects in the absence of DNA damaging agents. We also found a moderate suppression of the slow growth and UV sensitivity of rhp51 mutants by the myh1 mutation. Our results implicate fission yeast Myh1 in repair of a wider range of DNA damage than previously thought, and functionally link it to the checkpoint pathway.
DNA糖基化酶MutY在进化过程中高度保守，在所研究的大多数真核生物和原核生物中都能找到其同源物。该蛋白与氧化性DNA损伤的修复有关，特别是与7,8 - 二氢 - 8 - 氧代鸟嘌呤错配的腺嘌呤的修复。先前在大肠杆菌、裂殖酵母和哺乳动物细胞中的研究表明，MutY同源物中的突变与突变表型和致癌作用有关。真核MutY同源物与几种在复制、DNA修复和检查点信号传导中起作用的蛋白质发生物理相互作用，特别是三聚体9-1-1复合物。在对裂殖酵母MutY同源物myh1(+)的基因研究中，我们发现myh1突变单独以及与几个DNA修复基因的突变一起会使紫外线敏感性适度增加。myh1 rad1双突变体，以及程度较轻的myh1 rad9双突变体，表现出合成相互作用，导致对DNA损伤剂和羟基脲的敏感性增强。对myh1 rad1双突变体进行紫外线照射会导致严重的染色体分离缺陷和明显的DNA片段化，并且无法激活检查点。此外，myh1 rad1双突变体在没有DNA损伤剂的情况下表现出形态缺陷。我们还发现myh1突变对rhp51突变体的生长缓慢和紫外线敏感性有适度的抑制作用。我们的结果表明，裂殖酵母Myh1参与修复的DNA损伤范围比以前认为的更广，并在功能上与检查点途径相关联。
