Mechanism of metazoan replisome assembly in health and disease

Regulated assembly of the eukaryotic replisome ensures that chromosomes are duplicated just once per cell cycle. In humans, defects in replisome assembly cause Meier Gorlin Syndrome and are an important feature of early cancer development. We have found that metazoan replisome assembly requires a protein called DONSON, which is mutated in Meier Gorlin Syndrome. DONSON was lost during fungal evolution and so is absent in budding yeast that has dominated studies of eukaryotic replisome assembly. In Aim 1, we will use C. elegans to elucidate the mechanism and regulation by which DONSON and other factors assemble the CMG helicase upon entry into S-phase (CMG = CDC45-MCM-GINS: the three helicase subassemblies around which the replisome forms). In Aim 2, we will characterise the factors that activate the newly assembled CMG helicase in metazoa. In Aim 3, we will analyse how DONSON and other factors assemble CMG in mammalian cells, searching for new factors mutated in Meier Gorlin syndrome, and screening for synthetic lethality between CMG assembly defects and disease-linked mutations in human cells. These studies address an issue of fundamental importance in animal cell biology and will explore the potential of CMG assembly as a target for future anti-cancer therapies.