Structural and functional studies of DNA mismatch repair proteins

DNA的完整性不断受到破坏性损伤的威胁，这些损伤可能导致染色体重排或细胞死亡。我们研究计划的长期目标是了解DNA损伤如何有效修复，从而防止基因组不稳定。DNA损伤反应最吸引人的方面之一是修复蛋白如何在不考虑环境的情况下找到损伤，从而确保每个损伤的修复。我们的实验室研究了基于其形状切割DNA的蛋白质（称为结构特异性核酸酶）如何识别和切割其靶DNA。我们的总体假设是，结构特异性核酸酶使用共同的DNA结合机制，但通过与途径特异性因子的相互作用实现特异性。为了探索这个想法，我们将使用生物化学，生物物理学和结构生物学技术的组合来研究两种DNA修复途径中的结构特异性核酸酶如何结合和切割DNA。DNA错配修复可以纠正DNA复制时发生的错误。两个保守的蛋白质是必不可少的这个过程：MutS和MutL。多年来，我的实验室为MutL的功能做出了关键贡献。然而，MutL看起来不像任何其他核酸酶，因此，我们还不知道它如何切割DNA。在接下来的五年里，我们将通过确定与DNA结合的MutL的三维结构来解决这个问题。利用我们在MutL方面的经验，我们最近扩大了研究计划的范围，以表征其他修复途径中的结构特异性核酸酶。影响两条DNA链的断裂是最危险的损伤形式，因为断裂的片段不保留其背景信息。单链退火修复相邻重复序列之间的双链断裂。虽然这种修复机制会导致遗传信息的丢失，但由于我们基因组中存在高频率的同源重复序列，它在人类中很普遍。我们将确定衔接蛋白Saw 1如何招募结构特异性核酸酶Rad 1-Rad 10来修复中间体。这一点很重要，因为Rad 1-Rad 10可以处理几种类型的损伤，因此，衔接蛋白决定了要处理的损伤。我们的工作将为这两种核酸酶在DNA修复和基因组维护中的作用提供基本的机制见解。后者对健康老龄化特别重要。加拿大被描述为一个“老龄化国家”，因为它有更多的65岁以上的人比15岁以下的人，强调了我们的研究的间接效益。

The integrity of DNA is constantly threatened by damaging insults that can lead to chromosomal rearrangements or cell death. The long-term goal of our research program is to understand how DNA damage is efficiently repaired, in turn preventing genome instability. One of the most fascinating aspects of the DNA damage response is how repair proteins find the lesions regardless of context, thereby ensuring the repair of each and every lesion. Our laboratory studies how the proteins that cut DNA based on its shape (known as structure-specific nucleases) recognize and cut their target DNA. Our overarching hypothesis is that structure-specific nucleases use common DNA binding mechanisms, but achieve specificity through their interaction with pathway-specific factors. To probe this idea, we will use a combination of biochemical, biophysical and structural biology techniques to study how structure-specific nucleases in two DNA repair pathways bind and cut DNA. DNA mismatch repair corrects errors that occur while DNA is being copied. Two conserved proteins are essential for this process: MutS and MutL. Over the years, my laboratory has made key contributions to the functions of MutL. However, MutL does not look like any other nuclease and, therefore, we do not understand how it cuts DNA yet. In the next five years, we will address this question by determining the 3-dimensional structure of MutL bound to DNA. Leveraging our experience with MutL, we have recently broaden the scope of our research program to characterize structure-specific nucleases in other repair pathways. Breaks affecting both DNA strands are the most dangerous form of damage because the broken pieces do not retain information of their context. Single strand-annealing repairs double-strand breaks between adjacent repeat sequences. Although this repair mechanism causes the loss of genetic information, it is prevalent in humans, due to the high frequency of homologous repeat sequences present in our genome. We will determine how the adaptor protein Saw1 recruits the structure-specific nuclease Rad1-Rad10 to repair intermediates. This is important because Rad1-Rad10 can process several types of damage and, therefore, the adaptor proteins determine the lesion to be processed. Our work will provide fundamental mechanistic insights into the roles of these two nucleases in DNA repair and genome maintenance. The latter is specially important for healthy aging. Canada has been described as a “greying nation” because it has more people over 65 than under 15, underscoring the indirect benefits of our research.