Three structure-selective endonucleases are essential in the absence of BLM helicase in Drosophila.
Three structure-selective endonucleases are essential in the absence of BLM helicase in Drosophila.
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DOI：
10.1371/journal.pgen.1002315
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发表时间：
2011-10
期刊：
影响因子：
4.5
通讯作者：
Sekelsky J
中科院分区：
文献类型：
--
作者：
Andersen SL;Kuo HK;Savukoski D;Brodsky MH;Sekelsky J
有丝分裂增殖细胞中的DNA修复机制避免产生交叉，这可能导致基因组不稳定。用于产生交叉的大多数模型涉及具有一个或多个四链霍利迪连接（HJ）的中间体，所述四链霍利迪连接（HJ）通过被专门的核酸内切酶切割而分解成双链体分子。在体外研究中，已经发现三种核酶参与了HJ的分解：MUS 81-EME 1/Mms 4、GEN 1/Yen 1和SLX 4-SLX 1。Bloom综合征解旋酶BLM通过阻断HJ中间体的形成或在不裂解的情况下去除HJ，在防止有丝分裂交叉中起关键作用。缺乏Sgs 1（BLM直系同源物）和Mus 81-Mms 4或Slx 4-Slx 1的酿酒酵母突变体是不可存活的，但缺乏Sgs 1和Yen 1的突变体是可行的。目前的观点是，Yen 1主要是作为Mus 81-Mms 4的备份。先前对黑腹果蝇的研究表明，与酵母一样，DmBLM和MUS 81或MUS 312（SLX 4的直系同源物）的缺失是致命的。我们现在已经恢复并分析了果蝇基因突变。在酵母中，基因和mus 81之间存在一些冗余;然而，与酵母中的情况相反，GEN在响应DNA损伤中起着比MUS 81-MMS 4更重要的作用。此外，DmBLM和GEN的缺失导致发育早期的致死性。我们提出了一个比较表型发生在双突变体，缺乏DmBLM和MUS 81，GEN，或MUS 312，包括染色体不稳定性和细胞增殖的缺陷。我们的合成致死性的研究提供了深入了解DmBLM的多种功能，以及当DmBLM不存在时，各种核酸内切酶如何发挥作用。维持稳定的基因组对生物体的生存至关重要。基因组稳定性永远受到自发DNA损伤的威胁，需要DNA修复蛋白以最小化基因组改变的方式准确有效地修复DNA损伤。一些修复途径与基因组变化的风险增加有关。一个例子是与同源染色体之间的交叉产生相关的修复。DNA解旋酶BLM通过促进非交换形式的修复来抑制基因组变化;没有BLM，自发的交换、缺失和基因组重排增加。以果蝇为模型生物，我们的研究揭示了BLM和三种结构选择性内切酶之间复杂的相互作用，这些酶具有重叠的底物特异性和部分功能冗余。BLM和任何一种核酸酶的缺失都会导致严重的基因组不稳定性，细胞增殖减少，最终导致动物死亡。我们的工作表明，这些核酸酶差异拯救与DNA复制过程中出现的问题相关的BLM功能的丧失，阐明了复制过程中维持基因组稳定性所需的修复机制的复杂性。此外，我们的工作提出了复制相关的修复模型的BLM和结构选择性核酸内切酶的具体作用。
DNA repair mechanisms in mitotically proliferating cells avoid generating crossovers, which can contribute to genome instability. Most models for the production of crossovers involve an intermediate with one or more four-stranded Holliday junctions (HJs), which are resolved into duplex molecules through cleavage by specialized endonucleases. In vitro studies have implicated three nuclear enzymes in HJ resolution: MUS81–EME1/Mms4, GEN1/Yen1, and SLX4–SLX1. The Bloom syndrome helicase, BLM, plays key roles in preventing mitotic crossover, either by blocking the formation of HJ intermediates or by removing HJs without cleavage. Saccharomyces cerevisiae mutants that lack Sgs1 (the BLM ortholog) and either Mus81–Mms4 or Slx4–Slx1 are inviable, but mutants that lack Sgs1 and Yen1 are viable. The current view is that Yen1 serves primarily as a backup to Mus81–Mms4. Previous studies with Drosophila melanogaster showed that, as in yeast, loss of both DmBLM and MUS81 or MUS312 (the ortholog of SLX4) is lethal. We have now recovered and analyzed mutations in Drosophila Gen. As in yeast, there is some redundancy between Gen and mus81; however, in contrast to the case in yeast, GEN plays a more predominant role in responding to DNA damage than MUS81–MMS4. Furthermore, loss of DmBLM and GEN leads to lethality early in development. We present a comparison of phenotypes occurring in double mutants that lack DmBLM and either MUS81, GEN, or MUS312, including chromosome instability and deficiencies in cell proliferation. Our studies of synthetic lethality provide insights into the multiple functions of DmBLM and how various endonucleases may function when DmBLM is absent. The maintenance of a stable genome is crucial to organismal survival. Genome stability is perpetually threatened by spontaneous DNA damage, and DNA repair proteins are required to accurately and efficiently repair DNA damage in ways that minimize genome alterations. Some repair pathways are linked to increased risk of genome changes. One example is repair associated with the production of crossovers between homologous chromosomes. The DNA helicase BLM suppresses genome changes by promoting non-crossover forms of repair; without BLM, spontaneous crossovers, deletions, and genome rearrangements increase. Using Drosophila as a model organism, our studies reveal the complex interactions between BLM and three structure-selective endonucleases with overlapping substrate specificities and partial functional redundancy. Loss of BLM and any one of the nucleases results in severe genome instability, reduced cell proliferation, and, ultimately, death of the animal. Our work suggests that these nucleases differentially rescue the loss of functions of BLM associated with problems that arise during DNA replication, illuminating the complexity of repair mechanisms required to maintain genome stability during replication. Further, our work advances models of replication-associated repair by suggesting specific roles for BLM and structure-selective endonucleases.
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影响因子：
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ATMUS81在A. thaliana中对干扰不敏感的交叉中的作用。
影响因子：
4.5
作者：
Berchowitz, Luke E.;Francis, Kirk E.;Bey, Alexandra L.;Copenhaver, Gregory P.
通讯作者：
Copenhaver, Gregory P.