Replication arrest, restart and genome instability (360G-Wellcome-110047_Z_15_Z)

My research aims to understand specific mechanisms underlying replication-dependent genetic instability. DNA replication is remarkably accurate, however errors do occur during DNA replication and the resulting genetic alterations can result in disease, including genetic and somatic disorders(1,2). The most pernicious somatic disorder is cancer. Much of the aetiology of cancer is proposed to be dependent on replication stress-induced genetic instability(3,4). Current models suggest that imbalance d growth due to oncogene activation results in aberrant DNA replication, in part through incorrect E2F regulation, perturbed origin usage and restricted dNTP supplies(5-7). Oncogene-induced replication stress allows the accumulation of the multiple alterations required for cancer and can drive tumour cell evolution. Replication Forks (RFs) can be arrested by a variety of obstacles(8,9), including damaged template bases, DNA bound proteins, specific DNA sequences (those adopting non-canonical structures(10)) and DNA metabolism (i.e. transcription). The first defence is intra-S-phase checkpoint activation to stabilise arrested RFs: the replication machinery remains associated with the nascent DNA and the RF structure is protected from inappropriate DNA metabolism. Stabilised RFs can resume replication when the blockage is removed or bypassed. When replication checkpoint activity fails to stabilise a RF, it collapses. The second defence is the completion of replication by a converging RF. This is not always possible and the third defence to prevent an unreplicated DNA region is restart of the collapsed fork, a process involving homologous recombination (HR)(11). Questions widely investigated in the field include: How are RFs arrested; how does the replication checkpoint prevent RF collapse; what is the structure of the collapsed fork; what happens to associated replication proteins; how is the collapsed fork processed; how does HR restart a collapsed fork? My research q uestions focus on processes that occur after HR restarts replication, the significance of which has only recently been appreciated: What is the protein and DNA architecture of an HR-restarted fork? Which replication/repair proteins complete replication? Why are HR-restarted forks error prone? How do cells merge collapsed/restarted and canonical RFs?