Ufd1-Npl4 Recruit Cdc48 for Disassembly of Ubiquitylated CMG Helicase at the End of Chromosome Replication

Publication date: 28 March 2017
Source:Cell Reports, Volume 18, Issue 13
Author(s): Marija Maric, Progya Mukherjee, Michael H. Tatham, Ronald Hay, Karim Labib
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.

Graphical abstract

Teaser

Disassembly of the CMG helicase is the key regulated step during DNA replication termination in eukaryotes, driven by CMG ubiquitylation and the Cdc48 segregase. Maric et al. find that the Ufd1-Npl4 heterodimer is essential for CMG disassembly in budding yeast and is required to recruit Cdc48 to the ubiquitylated helicase.


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