A Mechanism for Controlled Breakage of Under-replicated Chromosomes during Mitosis

• Published in: Developmental cell Vol. 39; no. 6; pp. 740 - 755
• Main Authors: Duda, Heike, Arter, Meret, Gloggnitzer, Jiradet, Teloni, Federico, Wild, Philipp, Blanco, Miguel G., Altmeyer, Matthias, Matos, Joao
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.12.2016
• Subjects: CDC2 Protein Kinase - metabolism; CDK1; cell cycle; Cell Cycle Proteins - metabolism; Cell Death; Cell Survival; chromosome pulverization; Chromosomes, Human - metabolism; DNA Damage; DNA Fragmentation; DNA Replication; DNA-Binding Proteins - metabolism; EME2; Endonucleases - metabolism; HeLa Cells; Humans; Mitosis; Models, Biological; MUS81; Phosphorylation; PLK1; Protein Binding; Recombinases - metabolism; S Phase; SLX4; WEE1; MUS81; WEE1; DNA replication; SLX4; cell cycle; EME2; PLK1; chromosome pulverization; CDK1
• ISSN: 1534-5807; 1878-1551
• DOI: 10.1016/j.devcel.2016.11.017

While DNA replication and mitosis occur in a sequential manner, precisely how cells maintain their temporal separation and order remains elusive. Here, we unveil a double-negative feedback loop between replication intermediates and an M-phase-specific structure-selective endonuclease, MUS81-SLX4, which renders DNA replication and mitosis mutually exclusive. MUS81 nuclease is constitutively active throughout the cell cycle but requires association with SLX4 for efficient substrate targeting. To preclude toxic processing of replicating chromosomes, WEE1 kinase restrains CDK1 and PLK1-mediated MUS81-SLX4 assembly during S phase. Accordingly, WEE1 inhibition triggers widespread nucleolytic breakage of replication intermediates, halting DNA replication and leading to chromosome pulverization. Unexpectedly, premature entry into mitosis—licensed by unrestrained CDK1 activity during S phase—requires MUS81-SLX4, which inhibits DNA replication. This suggests that ongoing replication assists WEE1 in delaying entry into M phase and, indirectly, in preventing MUS81-SLX4 assembly. Conversely, MUS81-SLX4 activation during mitosis promotes targeted resolution of persistent replication intermediates, which safeguards chromosome segregation. [Display omitted] •CDK1-dependent phosphorylation of SLX4 controls MUS81-SLX4 complex formation•CDK1 activation in S phase drives MUS81-SLX4-mediated chromosome pulverization•WEE1 inhibitors cause cell death partly by MUS81-SLX4-dependent chromosome breakage•DNA replication and WEE1 collaboratively suppress CDK1 activity during S phase MUS81 nuclease resolves persistent replication intermediates at mitotic onset to safeguard chromosome segregation. Duda et al. uncover dynamic regulation of MUS81 function during the cell cycle to protect S-phase chromosomes from unscheduled breakage and pulverization. This regulation ensures that DNA replication and mitosis occur sequentially and in a mutually exclusive manner.