Elucidating the Rad51-independent pathway of recombination-dependent replication

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Before a cell can divide, it must first replicate its genetic material so that each new daughter cell can receive a copy. The DNA replication process that achieves this feat depends on complex multi-protein machines called 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. DNA lesions, and 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. To help ensure the successful completion of DNA replication during the cell cycle, eukaryotic cells use two alternative enzymatic pathways to repair and restart replication forks that collapse following collision with a barrier. The goal of this project is to understand how these restart pathways work, focusing on the least understood of the two, which has been implicated in promoting cancer cell survival. We will identify the components of the pathway and study how they function. To achieve these objectives, we will exploit the genetic tractability of a simple model eukaryote. However, the fundamental aspects of biology that will be studied are highly conserved and, therefore, our discoveries will provide a valuable paradigm to guide future research in human cells. Ultimately, our work will contribute to a greater understanding of replication restart - knowledge that will be vital for guiding the development of novel cancer therapies.