Elucidating the mechanisms that govern replication restart efficiency and fidelity

点击翻译按钮获取中文摘要

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 is performed by complex, multi-component protein machines known as replisomes, 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 cell cycle, multiple origins along every chromosome "fire", each releasing a pair of "replication forks" that travel in opposite directions away from their origin. DNA replication is completed when forks from adjacent origins merge. The failure of even a single pair of forks to merge results in a region of unreplicated DNA that can lead to DNA breakage, and ultimately genetic mutations that cause diseases such as cancer. The many proteins that bind chromosomal DNA threaten successful completion of replication by physically impeding the progress of the replication fork. When a replication fork encounters such a barrier, it can undergo a process termed fork collapse in which its replisome partially or completely dissociates from the DNA. Following fork collapse, cells seem to make use of two different mechanisms to ensure completion of DNA replication: 1) passive DNA replication by an opposing fork, which may be promoted by the firing of normally dormant origins nearby; and 2) restart of the failed fork by a poorly understood process that depends on proteins that catalyse DNA recombination. Intriguingly, restarting replication can itself cause harmful mutations and chromosomal rearrangements and, therefore, is presumably strictly regulated to limit its deleterious effects. To better understand how cells deal with failed replication forks, we aim to identify the factors that affect the efficiency and fidelity of replication restart. We also aim to discover whether dormant replication origins fire in response to a single collapsed replication fork, and whether this is an active or passive process. By deciphering these fundamental processes, we will gain a better understanding of the molecular basis of diseases, such as cancer, whose development and progression are often rooted in problems that arise during DNA replication. Ultimately, the knowledge obtained from this project will underpin future endeavours to develop new diagnostics and therapeutics for clinical use.