Structure:Function Correlation in the Human DNA Repair Factor CtIP

我们的身体由数十亿个不同类型的细胞组成，它们执行我们生存所需的所有任务。每天，我们的健康细胞不断受到DNA损伤的挑战。由于DNA包含了生命所需的所有信息，因此维持其结构至关重要。DNA损伤会导致称为突变的错误，如果这些错误得不到适当修复，最终可能会导致癌症等疾病。我们对一种特别有害的损伤类型--双链断裂(DSB)感兴趣，在这种损伤类型中，DNA被来自细胞外的损伤剂物理断裂，或者只是由于DNA上正常发生的许多复杂过程的结果。当发生DSB时，关键是两端重新连接在一起，而不会出现错误。这一过程需要许多不同的蛋白质共同作用来桥接DNA末端，修剪掉DNA末端受损时出现的任何笨重的加合物，然后在切割其中一条DNA链的同时解开DNA双螺旋。这暴露了围绕损伤的遗传密码，使细胞能够找到同等的未损伤的DNA部分，用作修复的模板。这一过程的总体方案被称为同源重组，虽然复杂，但已经得到了充分的研究。然而，在了解作为修复因子的单个蛋白质如何共同工作的方式方面缺乏细节，这对我们治疗由DNA修复途径缺陷引起的疾病以及安全地应用新方法编辑人类基因组的能力产生了负面影响。我们特别对一种名为CtIP的蛋白质感兴趣，它特别重要，因为它似乎通过协调断裂的DNA末端与修复它们所需的许多其他因素来充当修复断裂DNA的结构枢纽。此外，当CtIP不能正常工作时，它被认为与癌症以及导致侏儒症和神经系统疾病的罕见的人类疾病塞克尔和贾瓦德综合征有关。尽管CtIP蛋白具有重要意义，但我们对它的结构，它如何与DNA和其他蛋白质相互作用，以及CtIP在疾病状态下的问题所知甚少。在这个项目中，我们召集了一个跨学科的研究团队，应用生物物理、生物化学和细胞生物学的一系列技术，拼凑出这种重要蛋白质的结构和细胞功能之间的关系，以及它与DNA和其他合作伙伴形成的复合体。这一新知识将极大地提高我们对人类DNA断裂修复的理解，对癌症和其他疾病的诊断和治疗以及现代基因编辑技术的进一步完善具有广泛的意义。

Our bodies are composed of billions of cells of many different types that perform all the tasks we need to survive. Every day our healthy cells are constantly being challenged by damage to their DNA. As DNA contains all the information necessary for life, it is crucial that its structure is maintained. DNA damage causes mistakes known as mutations and if these are not repaired properly it can eventually lead to diseases such as cancer. We are interested in a particularly harmful type of damage called double-strand breaks (DSBs), where the DNA is physically broken by damaging agents which come from outside the cell or simply as a result of the many complex processes that occur normally on DNA. When a DSB occurs, it is crucial that the ends are joined back together again without errors. This process requires many different proteins which collaborate to bridge the DNA ends, trim away any bulky adducts at the DNA ends that have arisen when it was damaged, and then unwind the DNA double-helix while cleaving one of the DNA strands. This exposes the genetic code surrounding the damage, allowing the cell to find an equivalent undamaged portion of DNA to use as a template for repair. The overall scheme for this process, which is called Homologous Recombination, is complicated but has been well-studied. However, there is a lack of fine detail in the understanding of the way in which the individual proteins that act as repair factors work together, and this negatively impacts on our ability to treat diseases caused by defective DNA repair pathways, as well as to safely apply new methods for editing human genomes.We are especially interested in a protein called CtIP, which is especially important as it appears to act as a structural hub for repair of broken DNA by co-ordinating the broken DNA ends with many of the other factors required to fix them. Moreover, when CtIP is not working properly, it has been implicated in cancer and the rare human diseases Seckel and Jawad syndromes which cause dwarfism and neurological disorders. Despite its significance, we know very little indeed about the architecture of the CtIP protein, how it interacts with DNA and other proteins, and what is wrong with CtIP in the disease state. In this project, we have assembled a team of interdisciplinary researchers to apply a range of techniques in biophysics, biochemistry and cell biology to piece together the relationship between the structure and cellular function of this important protein and the complexes it forms with DNA and other partners. This new knowledge will dramatically improve our understanding of human DNA break repair with wide ranging implications for the diagnosis and treatment of cancer and other diseases, as well as the further refinement of modern gene editing technology.