DNA replication errors generate complex chromosomal rearrangements and thereby contribute to tumorigenesis and other human diseases. One mechanism that triggers these errors is mitotic entry before the completion of DNA replication. To address how mitosis might affect DNA replication, we used Xenopus egg extracts. When mitotic CDK (Cyclin B1- CDK1) is used to drive interphase egg extracts into a mitotic state, the replicative CMG (CDC45/MCM2-7/ GINS) helicase undergoes ubiquitylation on its MCM7 subunit, dependent on the E3 ubiquitin ligase TRAIP. Whether replisomes have stalled or undergone termination, CMG ubiquitylation is followed by its extraction from chromatin by the CDC48/p97 ATPase. TRAIPdependent CMG unloading during mitosis is also seen in C. elegans early embryos. At stalled forks, CMG removal results in fork breakage and end joining events involving deletions and templated insertions. Our results identify a mitotic pathway of global replisome disassembly that can trigger replication fork collapse and DNA rearrangements. INTRODUCTION Genome evolution occurs through the gradual accrual of genetic changes or in a saltatory manner, with bursts of chromosomal alterations originating from single catastrophic events (Holland and Cleveland, 2012; Leibowitz et al., 2015; Liu et al., 2011; Stephens et al., 2011). Many chromosomal alterations can be traced to DNA breaks that arise during DNA replication (Hills and Diffley, 2014; Mankouri et al., 2013; Te´ cher et al., 2017). However, when and how replication fork breakage is triggered remains incompletely understood (Toledo et al., 2017).