DNA polymerase ε relies on a unique domain for efficient replisome assembly and strand synthesis

DNA polymerase epsilon (Pol epsilon) is required for genome duplication and tumor suppression. It supports both replisome assembly and leading strand synthesis; however, the underlying mechanisms remain to be elucidated. Here we report that a conserved domain within the Pol epsilon catalytic core influences both of these replication steps in budding yeast. Modeling cancer-associated mutations in this domain reveals its unexpected effect on incorporating Pol epsilon into the four-member pre-loading complex during replisome assembly. In addition, genetic and biochemical data suggest that the examined domain supports Pol epsilon catalytic activity and symmetric movement of replication forks. Contrary to previously characterized Pol epsilon cancer variants, the examined mutants cause genome hyper-rearrangement rather than hyper-mutation. Our work thus suggests a role of the Pol epsilon catalytic core in replisome formation, a reliance of Pol epsilon strand synthesis on a unique domain, and a potential tumor-suppressive effect of Pol epsilon in curbing genome re-arrangements. DNA polymerase epsilon (Pol epsilon) synthesizes half of the genome in every cell cycle. Here the authors uncover a dual role of a unique domain within the Pol epsilon catalytic core in replisome assembly and DNA synthesis and the impact of this domain on genome stability.