CRL2LRR1 is required for CMG unloading during vertebrate replication termination

A key event during eukaryotic replication termination is the removal of the CMG helicase from chromatin. CMG unloading involves ubiquitylation of its MCM7 subunit and the action of the p97 ATPase. Using a proteomic screen in Xenopus egg extracts, we identified factors that are retained on chromatin when CMG unloading is blocked and identified the E3 ubiquitin ligase CRL2LRR1 and several other potential regulators of termination including a specific p97 complex. We show that CRL2LRR1 recruitment coincides with MCM7 ubiquitylation and occurs only when replisomes converge. In the absence of CRL2LRR1, MCM7 is not ubiquitylated, CMG unloading is inhibited, and many replisome components including DNA pol are retained on DNA. Our data identify CRL2LRR1 as a master regulator of replisome disassembly during vertebrate DNA replication termination.