Disassembly of the Cdc45-MCM-GINS (CMG) DNA helicase is the key regulated step 
during DNA replication termination in eukaryotes, involving ubiquitylation of 
the Mcm7 helicase subunit, leading to a disassembly process that requires the 
Cdc48 "segregase". Here, we employ a screen to identify partners of budding 
yeast Cdc48 that are important for disassembly of ubiquitylated CMG helicase at 
the end of chromosome replication. We demonstrate that the ubiquitin-binding 
Ufd1-Npl4 complex recruits Cdc48 to ubiquitylated CMG. Ubiquitylation of CMG in 
yeast cell extracts is dependent upon lysine 29 of Mcm7, which is the only 
detectable site of ubiquitylation both in vitro and in vivo (though in vivo 
other sites can be modified when K29 is mutated). Mutation of K29 abrogates 
in vitro recruitment of Ufd1-Npl4-Cdc48 to the CMG helicase, supporting a model 
whereby Ufd1-Npl4 recruits Cdc48 to ubiquitylated CMG at the end of chromosome 
replication, thereby driving the disassembly reaction.