Department of Molecular Genetics and Preparative Molecular Biology, Institute for Microbiology and Genetics, University of Göttingen, D-37077 Göttingen, Germany.
Yeast. 2010 Jan;27(1):11-27. doi: 10.1002/yea.1727.
In yeast as in human, DNA helicases play critical roles in assisting replication fork progression. The Saccharomyces cerevisiae MPH1 gene, homologue of human FANCM, has been involved in homologous recombination and DNA repair. We describe a synthetic growth defect of an mph1 deletion if combined with an srs2 deletion that can result-depending on the genetic background-in synthetic lethality. The lethality is suppressed by mutations in homologous recombination (rad51, rad52, rad55, rad57) and in the DNA damage checkpoint (rad9, rad24, rad17). Importantly, rad54 and mph1, epistatic for damage sensitivity, are subadditive for spontaneous mutator phenotype. Therefore, Mph1 could be placed at the Rad51-mediated strand invasion process, with a function distinct from Rad54. Moreover, siz1 mutation is viable with mph1 and additive for DNA damage sensitivity. mph1 srs2 double mutants, isolated in a background where they are viable, are synergistically sensitive to DNA damage. Moderate overexpression of SGS1 partially suppresses this sensitivity. Finally, we observe an epistatic relationship in terms of sensitivity to camptothecin of mms4 or mus81 to mph1. Overall, our results support a role of Mph1 in assisting replication progression. We propose two models for the resumption of DNA synthesis under replicative stress where Mph1 is placed at the sister chromatid interaction step.
在酵母和人类中，DNA 解旋酶在协助复制叉进展方面起着关键作用。酿酒酵母 MPH1 基因是人类 FANCM 的同源物，参与同源重组和 DNA 修复。我们描述了 mph1 缺失与 srs2 缺失组合的合成生长缺陷，如果组合的遗传背景不同，可能会导致合成致死。这种致死性可以通过同源重组（rad51、rad52、rad55、rad57）和 DNA 损伤检查点（rad9、rad24、rad17）的突变来抑制。重要的是，rad54 和 mph1 对损伤敏感性是上位的，对于自发突变表型是亚加性的。因此，Mph1 可能位于 Rad51 介导的链入侵过程中，其功能不同于 Rad54。此外，siz1 突变与 mph1 共存且对 DNA 损伤敏感性具有加性。在可行的背景下分离出的 mph1 srs2 双突变体对 DNA 损伤敏感具有协同性。适度过表达 SGS1 部分抑制了这种敏感性。最后，我们观察到 mms4 或 mus81 对 mph1 的敏感性在卡铂方面存在上位性关系。总的来说，我们的结果支持 Mph1 在协助复制进展方面的作用。我们提出了两种模型，即在复制应激下，Mph1 位于姐妹染色单体相互作用步骤，以恢复 DNA 合成。
