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CMG helicase disassembly is essential and mediated by two pathways in budding yeast

ABSTRACT: The Cdc45-MCM-GINS (CMG) helicase forms the stable core of the eukaryotic replisome and is ubiquitylated and disassembled during DNA replication termination. Fungi and animals use different enzymes to ubiquitylate the Mcm7 subunit of CMG, suggesting that CMG ubiquitylation arose repeatedly during eukaryotic evolution. Until now, it was unclear whether cells also have ubiquitin-independent pathways for helicase disassembly and whether CMG disassembly is essential for cell viability. Using reconstituted assays with budding yeast CMG, we generated the mcm7-10R allele that compromises ubiquitylation by the ubiquitin ligase complex SCFDia2. mcm7-10R delays helicase disassembly in vivo, causing genome instability in the next cell cycle. These data indicate that defective CMG ubiquitylation explains the major phenotypes of cells lacking the F-box protein Dia2. Notably, the viability of mcm7-10R and dia2∆ cells is dependent upon the related Rrm3 and Pif1 DNA helicases that have orthologues in all eukaryotes. We show that Rrm3 acts during S-phase to disassemble old CMG complexes from the previous cell cycle. These findings indicate that CMG disassembly is essential in yeast cells and suggest that Pif1-family helicases might have mediated CMG disassembly in ancestral eukaryotes.

SUBMITTER: Prof. Karim Labib

PROVIDER: S-SCDT-10_1038-S44318-024-00161-X | biostudies-other |

REPOSITORIES: biostudies-other

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CMG helicase disassembly is controlled by replication fork DNA, replisome components and a ubiquitin threshold.

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