CMG Helicase Disassembly is Controlled by Replication Fork DNA, Replisome Components and a Ubiquitin Threshold
Affiliations
The eukaryotic replisome assembles around the CMG helicase, which stably associates with DNA replication forks throughout elongation. When replication terminates, CMG is ubiquitylated on its Mcm7 subunit and disassembled by the Cdc48/p97 ATPase. Until now, the regulation that restricts CMG ubiquitylation to termination was unknown, as was the mechanism of disassembly. By reconstituting these processes with purified budding yeast proteins, we show that ubiquitylation is tightly repressed throughout elongation by the Y-shaped DNA structure of replication forks. Termination removes the repressive DNA structure, whereupon long K48-linked ubiquitin chains are conjugated to CMG-Mcm7, dependent on multiple replisome components that bind to the ubiquitin ligase SCF. This mechanism pushes CMG beyond a '5-ubiquitin threshold' that is inherent to Cdc48, which specifically unfolds ubiquitylated Mcm7 and thereby disassembles CMG. These findings explain the exquisite regulation of CMG disassembly and provide a general model for the disassembly of ubiquitylated protein complexes by Cdc48.
TTF2 promotes replisome eviction from stalled forks in mitosis.
Can G, Shyian M, Krishnamoorthy A, Lim Y, Wu R, Zaher M bioRxiv. 2024; .
PMID: 39651145 PMC: 11623681. DOI: 10.1101/2024.11.30.626186.
Ahmed S, Sasikumar J, Laha S, Das S Cancer Metastasis Rev. 2024; 43(4):1353-1371.
PMID: 39240414 DOI: 10.1007/s10555-024-10209-3.
Dynamics of Replication-Associated Protein Levels through the Cell Cycle.
Atemin A, Ivanova A, Kanev P, Uzunova S, Nedelcheva-Veleva M, Stoynov S Int J Mol Sci. 2024; 25(15).
PMID: 39125800 PMC: 11311332. DOI: 10.3390/ijms25158230.
Characterizing replisome disassembly in human cells.
Jones R, Ruiz J, Scaramuzza S, Nath S, Liu C, Henklewska M iScience. 2024; 27(7):110260.
PMID: 39055910 PMC: 11269944. DOI: 10.1016/j.isci.2024.110260.
Olson O, Pelliciari S, Heron E, Deegan T EMBO J. 2024; 43(18):3846-3875.
PMID: 39039288 PMC: 11405395. DOI: 10.1038/s44318-024-00168-4.