Uncovering the Role of Exo1 in Meiotic Recombination

项目总结 减数分裂是细胞分裂的一种特殊形式，导致配子的形成。减数分裂重组是一种 在这一过程中的关键步骤，在此过程中，同源染色体在物理上相互作用并交换基因 信息。在这个过程中，最终的重组DNA中间体是双Holliday连接(DHJ)。一个 减数分裂领域的主要问题是dHJ以偏向的方式被解决的机制 在同系物之间创建交叉产品。MLH1-MLH3，负责分解大部分的核酸酶 在萌芽酵母中的dHJ中，似乎没有固有的识别和切割dHJ的能力 有偏见的态度。这一观察结合遗传筛查揭示了各种各样的交叉 促进因子表明，其他蛋白质可能在dHJ相互作用，以促进有偏见的分辨。在这里我瞄准了 询问Exo1，一个在同源中具有公认的核酸酶作用的交叉促进因子 定向修复(HDR)和错配修复(MMR)。有趣的是，尽管在跨界中扮演着重要的角色 形成以前的工作表明，缺乏催化的Exo1突变体在交换中不会减少 频率，这表明Exo1的减数分裂作用与其核酸酶活性无关。在这里，我会 研究Exo1促进交叉形成的机制。我假设Exo1 作为dHJ的支架，通过与DNA和Mlh3的直接相互作用稳定和定向MLH1-Mlh3 MLH1。此外，我将继续我最近的工作，表明外显子1的促一氧化碳活性独立于MLH1 Mlh3函数作用于分辨率的上游。这项工作将对长期存在的问题提供见解 并为未来的研究开辟了令人振奋的新途径。

PROJECT SUMMARY Meiosis is a specialized form of cell division that results in the formation of gametes. Meiotic recombination is a crucial step in this process during which homologous chromosomes physically interact and exchange genetic information. The final recombination DNA intermediate in this process is the double Holliday Junction (dHJ). A major question in the meiosis field is the mechanism through which dHJs are resolved in a biased manner to create crossover products between homologs. Mlh1-Mlh3, the nuclease responsible for resolving the majority of dHJs in budding yeast, does not appear to be intrinsically capable of recognizing and cleaving dHJs in a biased manner. This observation combined with genetic screens revealing a wide variety of crossover promoting factors indicates that other proteins may interact at the dHJ to promote biased resolution. Here I aim to interrogate Exo1, a crossover promoting factor with well-established roles as a nuclease in homology directed repair (HDR) and mismatch repair (MMR). Interestingly, despite playing an important role in crossover formation previous work shows that catalytically deficient exo1 mutants do not suffer reductions in crossover frequencies, suggesting a meiotic role for Exo1 that is independent of its nuclease activity. Here, I will investigate the mechanism through which Exo1 promotes the formation of crossovers. I hypothesize that Exo1 acts as a scaffold at the dHJ to stabilize and orient Mlh1-Mlh3 through direct interaction with both the DNA and Mlh1. Additionally, I will follow up on my recent work indicating a pro-CO activity of Exo1 independent of Mlh1 Mlh3 functions that acts upstream of resolution. This work will provide insight into long-standing questions in the meiosis field and open up exciting new paths for future research.