Inter-Fork Strand Annealing: a novel mechanism that causes genomic deletions during the termination of DNA replication

在细胞分裂之前，它必须复制自己的遗传物质，以便每个新的子细胞都能得到一份拷贝。DNA复制过程发生在细胞周期的s期，由复杂的蛋白质机器完成，这些蛋白质机器被组装到染色体上称为复制起点的DNA上。这些机器解开DNA双螺旋，形成“叉”结构，在那里复制发生。在s阶段，每个起始点“发射”出一对“复制分叉”，它们从起始点向相反方向移动。DNA复制完成时，分叉从相邻的起源合并。众所周知，在复制的起始和延伸阶段发生的问题会导致染色体改变和灾难性突变，这些突变有助于衰老过程和与年龄有关的疾病（如癌症）的发展。然而，当复制分叉合并时，对复制终止的致突变潜力知之甚少。与复制起始不同，复制终止可以发生在基因组的任何位置，这使得研究变得困难。我的实验室率先使用位点特异性复制叉屏障将终止集中在特定的染色体位置。利用这种方法，我们发现了一种新的过程，通过这种过程染色体DNA的缺失可以在复制终止期间发生。这个项目的目的是确定这些缺失是如何产生的，以及控制它们发生的各种因素。染色体DNA的缺失侵蚀了对维持细胞健康和功能至关重要的遗传信息。通过了解导致这些缺失的机制，以及影响其频率的因素，我们将在未来更好地评估个人健康老龄化的能力，并设计出减轻衰老过程最坏影响的措施。

Before a cell divides it has to replicate its genetic material so that each new daughter cell can receive a copy. This process of DNA replication occurs in the S-phase of the cell cycle and is performed by complex protein machines, which are assembled onto DNA at chromosomal sites known as replication origins. These machines unwind the DNA double helix to form "fork" structures, at which the copying occurs. During the S-phase, origins "fire" each releasing a pair of "replication forks" that travel in opposite directions away from their site of initiation. DNA replication is completed when forks from adjacent origins merge. Problems that occur during both the initiation and elongation phases of replication are well known to cause chromosomal alterations and catastrophic mutations that are instrumental in the ageing process, and in the development of age related diseases such as cancer. However, very little is known about the mutagenic potential of replication termination, when replication forks merge. Unlike replication initiation, replication termination can occur at any site in the genome and this makes it difficult to study. My laboratory has pioneered the use of site-specific replication fork barriers to focus termination at specific chromosomal locations. Using this approach we have discovered a novel process by which deletions of chromosomal DNA can occur during replication termination. The aim of this project is to determine exactly how these deletions arise, and the various factors that govern their occurrence. Deletions of chromosomal DNA erode the genetic information that is vital for maintaining the health and function of cells. By understanding the mechanisms that cause these deletions, and the factors that influence their frequency, we will be better placed in the future to assess an individual's capacity for healthy ageing, and to devise measures for assuaging the worst effects of the ageing process.