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Li N, Gao N, Zhai Y. DDK promotes DNA replication initiation: Mechanistic and structural insights. Curr Opin Struct Biol 2023; 78:102504. [PMID: 36525878 DOI: 10.1016/j.sbi.2022.102504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/25/2022] [Accepted: 11/15/2022] [Indexed: 12/15/2022]
Abstract
DNA replication initiation in eukaryotes is tightly regulated through two cell-cycle specific processes, replication licensing to install inactive minichromosome maintenance (MCM) double-hexamers (DH) on origins in early G1 phase and origin firing to assemble and activate Cdc45-Mcm2-7-GINS (CMG) helicases upon S phase entry. Two kinases, cyclin-dependent kinase (CDK) and Dbf4-dependent kinase (DDK), are responsible for driving the association of replication factors with the MCM-DH to form CMG helicases for origin melting and DNA unwinding and eventually replisomes for bi-directional DNA synthesis. In recent years, cryo-electron microscopy studies have generated a collection of structural snapshots for the stepwise assembly and remodeling of the replication initiation machineries, creating a framework for understanding the regulation of this fundamental process at a molecular level. Very recent progress is the structural characterization of the elusive MCM-DH-DDK complex, which provides insights into mechanisms of kinase activation, substrate recognition and selection, as well as molecular role of DDK-mediated MCM-DH phosphorylation in helicase activation.
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Affiliation(s)
- Ningning Li
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China; National Biomedical Imaging Center, Peking University, Beijing, China.
| | - Yuanliang Zhai
- School of Biological Sciences, The University of Hong Kong, Hong Kong.
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2
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Böhly N, Schmidt AK, Zhang X, Slusarenko BO, Hennecke M, Kschischo M, Bastians H. Increased replication origin firing links replication stress to whole chromosomal instability in human cancer. Cell Rep 2022; 41:111836. [PMID: 36516748 DOI: 10.1016/j.celrep.2022.111836] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 09/12/2022] [Accepted: 11/22/2022] [Indexed: 12/14/2022] Open
Abstract
Chromosomal instability (CIN) is a hallmark of cancer and comprises structural CIN (S-CIN) and numerical or whole chromosomal CIN (W-CIN). Recent work indicated that replication stress (RS), known to contribute to S-CIN, also affects mitotic chromosome segregation, possibly explaining the common co-existence of S-CIN and W-CIN in human cancer. Here, we show that RS-induced increased origin firing is sufficient to trigger W-CIN in human cancer cells. We discovered that overexpression of origin firing genes, including GINS1 and CDC45, correlates with W-CIN in human cancer specimens and causes W-CIN in otherwise chromosomally stable human cells. Furthermore, modulation of the ATR-CDK1-RIF1 axis increases the number of firing origins and leads to W-CIN. Importantly, chromosome missegregation upon additional origin firing is mediated by increased mitotic microtubule growth rates, a mitotic defect prevalent in chromosomally unstable cancer cells. Thus, our study identifies increased replication origin firing as a cancer-relevant trigger for chromosomal instability.
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Affiliation(s)
- Nicolas Böhly
- Georg August University Göttingen, University Medical Center Göttingen (UMG), Department of Molecular Oncology, Section for Cellular Oncology, 37077 Göttingen, Germany
| | - Ann-Kathrin Schmidt
- Georg August University Göttingen, University Medical Center Göttingen (UMG), Department of Molecular Oncology, Section for Cellular Oncology, 37077 Göttingen, Germany
| | - Xiaoxiao Zhang
- University of Applied Sciences Koblenz, Department of Mathematics and Technology, 53424 Remagen, Germany; Technical University of Munich, Department of Informatics, 81675 Munich, Germany
| | - Benjamin O Slusarenko
- Georg August University Göttingen, University Medical Center Göttingen (UMG), Department of Molecular Oncology, Section for Cellular Oncology, 37077 Göttingen, Germany
| | - Magdalena Hennecke
- Georg August University Göttingen, University Medical Center Göttingen (UMG), Department of Molecular Oncology, Section for Cellular Oncology, 37077 Göttingen, Germany
| | - Maik Kschischo
- University of Applied Sciences Koblenz, Department of Mathematics and Technology, 53424 Remagen, Germany
| | - Holger Bastians
- Georg August University Göttingen, University Medical Center Göttingen (UMG), Department of Molecular Oncology, Section for Cellular Oncology, 37077 Göttingen, Germany.
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Gillespie PJ, Blow JJ. DDK: The Outsourced Kinase of Chromosome Maintenance. BIOLOGY 2022; 11:biology11060877. [PMID: 35741398 PMCID: PMC9220011 DOI: 10.3390/biology11060877] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 05/31/2022] [Accepted: 06/02/2022] [Indexed: 11/16/2022]
Abstract
The maintenance of genomic stability during the mitotic cell-cycle not only demands that the DNA is duplicated and repaired with high fidelity, but that following DNA replication the chromatin composition is perpetuated and that the duplicated chromatids remain tethered until their anaphase segregation. The coordination of these processes during S phase is achieved by both cyclin-dependent kinase, CDK, and Dbf4-dependent kinase, DDK. CDK orchestrates the activation of DDK at the G1-to-S transition, acting as the ‘global’ regulator of S phase and cell-cycle progression, whilst ‘local’ control of the initiation of DNA replication and repair and their coordination with the re-formation of local chromatin environments and the establishment of chromatid cohesion are delegated to DDK. Here, we discuss the regulation and the multiple roles of DDK in ensuring chromosome maintenance. Regulation of replication initiation by DDK has long been known to involve phosphorylation of MCM2-7 subunits, but more recent results have indicated that Treslin:MTBP might also be important substrates. Molecular mechanisms by which DDK regulates replisome stability and replicated chromatid cohesion are less well understood, though important new insights have been reported recently. We discuss how the ‘outsourcing’ of activities required for chromosome maintenance to DDK allows CDK to maintain outright control of S phase progression and the cell-cycle phase transitions whilst permitting ongoing chromatin replication and cohesion establishment to be completed and achieved faithfully.
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Saleh A, Noguchi Y, Aramayo R, Ivanova ME, Stevens KM, Montoya A, Sunidhi S, Carranza NL, Skwark MJ, Speck C. The structural basis of Cdc7-Dbf4 kinase dependent targeting and phosphorylation of the MCM2-7 double hexamer. Nat Commun 2022; 13:2915. [PMID: 35614055 PMCID: PMC9133112 DOI: 10.1038/s41467-022-30576-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 05/06/2022] [Indexed: 12/12/2022] Open
Abstract
The controlled assembly of replication forks is critical for genome stability. The Dbf4-dependent Cdc7 kinase (DDK) initiates replisome assembly by phosphorylating the MCM2-7 replicative helicase at the N-terminal tails of Mcm2, Mcm4 and Mcm6. At present, it remains poorly understood how DDK docks onto the helicase and how the kinase targets distal Mcm subunits for phosphorylation. Using cryo-electron microscopy and biochemical analysis we discovered that an interaction between the HBRCT domain of Dbf4 with Mcm2 serves as an anchoring point, which supports binding of DDK across the MCM2-7 double-hexamer interface and phosphorylation of Mcm4 on the opposite hexamer. Moreover, a rotation of DDK along its anchoring point allows phosphorylation of Mcm2 and Mcm6. In summary, our work provides fundamental insights into DDK structure, control and selective activation of the MCM2-7 helicase during DNA replication. Importantly, these insights can be exploited for development of novel DDK inhibitors.
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Affiliation(s)
- Almutasem Saleh
- DNA Replication Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Yasunori Noguchi
- DNA Replication Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Ricardo Aramayo
- DNA Replication Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Marina E Ivanova
- DNA Replication Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Kathryn M Stevens
- DNA Replication Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK
- MRC London Institute of Medical Sciences (LMS), Du Cane Road, London, W12 0NN, UK
| | - Alex Montoya
- Proteomics and Metabolomics Facility, MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK
| | - S Sunidhi
- InstaDeep Ltd, 5 Merchant Square, London, W2 1AY, UK
| | | | | | - Christian Speck
- DNA Replication Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK.
- MRC London Institute of Medical Sciences (LMS), Du Cane Road, London, W12 0NN, UK.
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Cheng J, Li N, Huo Y, Dang S, Tye BK, Gao N, Zhai Y. Structural Insight into the MCM double hexamer activation by Dbf4-Cdc7 kinase. Nat Commun 2022; 13:1396. [PMID: 35296675 PMCID: PMC8927117 DOI: 10.1038/s41467-022-29070-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 02/24/2022] [Indexed: 12/27/2022] Open
Abstract
The Dbf4-dependent kinase Cdc7 (DDK) regulates DNA replication initiation by phosphorylation of the MCM double hexamer (MCM-DH) to promote helicase activation. Here, we determine a series of cryo electron microscopy (cryo-EM) structures of yeast DDK bound to the MCM-DH. These structures, occupied by one or two DDKs, differ primarily in the conformations of the kinase core. The interactions of DDK with the MCM-DH are mediated exclusively by subunit Dbf4 straddling across the hexamer interface on the three N-terminal domains (NTDs) of subunits Mcm2, Mcm6, and Mcm4. This arrangement brings Cdc7 close to its only essential substrate, the N-terminal serine/threonine-rich domain (NSD) of Mcm4. Dbf4 further displaces the NSD from its binding site on Mcm4-NTD, facilitating an immediate targeting of this motif by Cdc7. Moreover, the active center of Cdc7 is occupied by a unique Dbf4 inhibitory loop, which is disengaged when the kinase core assumes wobbling conformations. This study elucidates the versatility of Dbf4 in regulating the ordered multisite phosphorylation of the MCM-DH by Cdc7 kinase during helicase activation.
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Affiliation(s)
- Jiaxuan Cheng
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing, 100871, China.,Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Ningning Li
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Yunjing Huo
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Shangyu Dang
- Division of Life Science, The Hong Kong University of Science & Technology, Hong Kong, China
| | - Bik-Kwoon Tye
- Institute for Advanced Study, The Hong Kong University of Science & Technology, Hong Kong, China. .,Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY, 14853, USA.
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing, 100871, China. .,National Biomedical Imaging Center, Peking University, Beijing, 100871, China.
| | - Yuanliang Zhai
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China.
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Structural mechanism for the selective phosphorylation of DNA-loaded MCM double hexamers by the Dbf4-dependent kinase. Nat Struct Mol Biol 2022; 29:10-20. [PMID: 34963704 PMCID: PMC8770131 DOI: 10.1038/s41594-021-00698-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 11/05/2021] [Indexed: 12/04/2022]
Abstract
Loading of the eukaryotic replicative helicase onto replication origins involves two MCM hexamers forming a double hexamer (DH) around duplex DNA. During S phase, helicase activation requires MCM phosphorylation by Dbf4-dependent kinase (DDK), comprising Cdc7 and Dbf4. DDK selectively phosphorylates loaded DHs, but how such fidelity is achieved is unknown. Here, we determine the cryogenic electron microscopy structure of Saccharomyces cerevisiae DDK in the act of phosphorylating a DH. DDK docks onto one MCM ring and phosphorylates the opposed ring. Truncation of the Dbf4 docking domain abrogates DH phosphorylation, yet Cdc7 kinase activity is unaffected. Late origin firing is blocked in response to DNA damage via Dbf4 phosphorylation by the Rad53 checkpoint kinase. DDK phosphorylation by Rad53 impairs DH phosphorylation by blockage of DDK binding to DHs, and also interferes with the Cdc7 active site. Our results explain the structural basis and regulation of the selective phosphorylation of DNA-loaded MCM DHs, which supports bidirectional replication.
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McClure AW, Diffley JF. Rad53 checkpoint kinase regulation of DNA replication fork rate via Mrc1 phosphorylation. eLife 2021; 10:69726. [PMID: 34387546 PMCID: PMC8387023 DOI: 10.7554/elife.69726] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Accepted: 08/12/2021] [Indexed: 12/18/2022] Open
Abstract
The Rad53 DNA checkpoint protein kinase plays multiple roles in the budding yeast cell response to DNA replication stress. Key amongst these is its enigmatic role in safeguarding DNA replication forks. Using DNA replication reactions reconstituted with purified proteins, we show Rad53 phosphorylation of Sld3/7 or Dbf4-dependent kinase blocks replication initiation whilst phosphorylation of Mrc1 or Mcm10 slows elongation. Mrc1 phosphorylation is necessary and sufficient to slow replication forks in complete reactions; Mcm10 phosphorylation can also slow replication forks, but only in the absence of unphosphorylated Mrc1. Mrc1 stimulates the unwinding rate of the replicative helicase, CMG, and Rad53 phosphorylation of Mrc1 prevents this. We show that a phosphorylation-mimicking Mrc1 mutant cannot stimulate replication in vitro and partially rescues the sensitivity of a rad53 null mutant to genotoxic stress in vivo. Our results show that Rad53 protects replication forks in part by antagonising Mrc1 stimulation of CMG unwinding.
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Affiliation(s)
- Allison W McClure
- Chromosome Replication Laboratory, The Francis Crick Institute, London, United Kingdom
| | - John Fx Diffley
- Chromosome Replication Laboratory, The Francis Crick Institute, London, United Kingdom
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Johnson MC, Can G, Santos MM, Alexander D, Zegerman P. Checkpoint inhibition of origin firing prevents inappropriate replication outside of S-phase. eLife 2021; 10:63589. [PMID: 33399537 PMCID: PMC7806266 DOI: 10.7554/elife.63589] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 01/04/2021] [Indexed: 01/02/2023] Open
Abstract
Checkpoints maintain the order of cell cycle events during DNA damage or incomplete replication. How the checkpoint response is tailored to different phases of the cell cycle remains poorly understood. The S-phase checkpoint for example results in the slowing of replication, which in budding yeast occurs by Rad53-dependent inhibition of the initiation factors Sld3 and Dbf4. Despite this, we show here that Rad53 phosphorylates both of these substrates throughout the cell cycle at the same sites as in S-phase, suggesting roles for this pathway beyond S-phase. Indeed, we show that Rad53-dependent inhibition of Sld3 and Dbf4 limits re-replication in G2/M, preventing gene amplification. In addition, we show that inhibition of Sld3 and Dbf4 in G1 prevents premature initiation at all origins at the G1/S transition. This study redefines the scope of the ‘S-phase checkpoint’ with implications for understanding checkpoint function in cancers that lack cell cycle controls.
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Affiliation(s)
- Mark C Johnson
- Wellcome Trust/Cancer Research United Kingdom Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Geylani Can
- Wellcome Trust/Cancer Research United Kingdom Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Miguel Monteiro Santos
- Wellcome Trust/Cancer Research United Kingdom Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Diana Alexander
- Wellcome Trust/Cancer Research United Kingdom Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Philip Zegerman
- Wellcome Trust/Cancer Research United Kingdom Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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De Jesús-Kim L, Friedman LJ, Lõoke M, Ramsoomair CK, Gelles J, Bell SP. DDK regulates replication initiation by controlling the multiplicity of Cdc45-GINS binding to Mcm2-7. eLife 2021; 10:65471. [PMID: 33616038 PMCID: PMC7954526 DOI: 10.7554/elife.65471] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 02/21/2021] [Indexed: 01/07/2023] Open
Abstract
The committed step of eukaryotic DNA replication occurs when the pairs of Mcm2-7 replicative helicases that license each replication origin are activated. Helicase activation requires the recruitment of Cdc45 and GINS to Mcm2-7, forming Cdc45-Mcm2-7-GINS complexes (CMGs). Using single-molecule biochemical assays to monitor CMG formation, we found that Cdc45 and GINS are recruited to loaded Mcm2-7 in two stages. Initially, Cdc45, GINS, and likely additional proteins are recruited to unstructured Mcm2-7 N-terminal tails in a Dbf4-dependent kinase (DDK)-dependent manner, forming Cdc45-tail-GINS intermediates (CtGs). DDK phosphorylation of multiple phosphorylation sites on the Mcm2-7 tails modulates the number of CtGs formed per Mcm2-7. In a second, inefficient event, a subset of CtGs transfer their Cdc45 and GINS components to form CMGs. Importantly, higher CtG multiplicity increases the frequency of CMG formation. Our findings reveal the molecular mechanisms sensitizing helicase activation to DDK levels with implications for control of replication origin efficiency and timing.
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Affiliation(s)
- Lorraine De Jesús-Kim
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Larry J Friedman
- Department of Biochemistry, Brandeis UniversityWalthamUnited States
| | - Marko Lõoke
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Christian K Ramsoomair
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Jeff Gelles
- Department of Biochemistry, Brandeis UniversityWalthamUnited States
| | - Stephen P Bell
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of TechnologyCambridgeUnited States
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