Eukaryotic cells make a single copy of their chromosomes in every cell cycle, using a large molecular machine known as the replisome. To preserve genome integrity, chromosome replication must normally be completed before sister chromatids are segregated during mitosis. However, in eukaryotic species with large genomes, it is hard to ensure that replication is always finished before mitosis has begun. For this reason, animal cells have evolved survival pathways that rapidly process sites of incomplete DNA replication during mitosis, in order to facilitate subsequent chromosome segregation. One such pathway is controlled by the TRAIP ubiquitin ligase, which is an important regulator of genome integrity and is mutated in a rare form of human disease. TRAIP induces replisome disassembly during mitosis, thereby activating a recombination process that is associated with ‘mitotic DNA synthesis’. In this way, the TRAIP pathway prepares partially replicated chromosomes for segregation. We are studying the regulation and mechanisms of such pathways, both in the early embryo of the nematode Caenorhabditis elegans (1-3) and also in mouse embryonic stem cells (4). Using a combination of cutting edge genetic and biochemical approaches, this project will explore how animal cells manage to survive the essential but dangerous business of replicating and segregating their chromosomes in each cell cycle.
1. L. Deng et al., Mitotic CDK Promotes Replisome Disassembly, Fork Breakage, and Complex DNA Rearrangements. Mol Cell 73, 915-929 (2019).
2. R. Sonneville et al., CUL-2(LRR-1) and UBXN-3 drive replisome disassembly during DNA replication termination and mitosis. Nat Cell Biol 19, 468-479 (2017).
3. R. Sonneville et al., TRAIP drives replisome disassembly and mitotic DNA repair synthesis at sites of incomplete DNA replication. Elife 8, e48686. doi: 10.7554 (2019).
4. F. Villa et al., CUL2(LRR1), TRAIP and p97 control CMG helicase disassembly in the mammalian cell cycle. EMBO Rep, e52164 (2021).