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Kellett EA, Bademosi AT, Walker AK. Molecular mechanisms and consequences of TDP-43 phosphorylation in neurodegeneration. Mol Neurodegener 2025; 20:53. [PMID: 40340943 PMCID: PMC12063406 DOI: 10.1186/s13024-025-00839-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2024] [Accepted: 04/10/2025] [Indexed: 05/10/2025] Open
Abstract
Increased phosphorylation of TDP-43 is a pathological hallmark of several neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, the regulation and roles of TDP-43 phosphorylation remain incompletely understood. A variety of techniques have been utilized to understand TDP-43 phosphorylation, including kinase/phosphatase manipulation, phosphomimic variants, and genetic, physical, or chemical inducement in a variety of cell cultures and animal models, and via analyses of post-mortem human tissues. These studies have produced conflicting results: suggesting incongruously that TDP-43 phosphorylation may either drive disease progression or serve a neuroprotective role. In this review, we explore the roles of regulators of TDP-43 phosphorylation including the putative TDP-43 kinases c-Abl, CDC7, CK1, CK2, IKKβ, p38α/MAPK14, MEK1, TTBK1, and TTBK2, and TDP-43 phosphatases PP1, PP2A, and PP2B, in disease. Building on recent studies, we also examine the consequences of TDP-43 phosphorylation on TDP-43 pathology, especially related to TDP-43 mislocalisation, liquid-liquid phase separation, aggregation, and neurotoxicity. By comparing conflicting findings from various techniques and models, this review highlights both the discrepancies and unresolved aspects in the understanding of TDP-43 phosphorylation. We propose that the role of TDP-43 phosphorylation is site and context dependent, and includes regulation of liquid-liquid phase separation, subcellular mislocalisation, and degradation. We further suggest that greater consideration of the normal functions of the regulators of TDP-43 phosphorylation that may be perturbed in disease is warranted. This synthesis aims to build towards a comprehensive understanding of the complex role of TDP-43 phosphorylation in the pathogenesis of neurodegeneration.
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Affiliation(s)
- Elise A Kellett
- Neurodegeneration Pathobiology Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, St Lucia, 4072 QLD, Australia
| | - Adekunle T Bademosi
- Neurodegeneration Pathobiology Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, St Lucia, 4072 QLD, Australia.
| | - Adam K Walker
- Neurodegeneration Pathobiology Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, St Lucia, 4072 QLD, Australia.
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Camperdown, 2006 NSW, Australia.
- Charles Perkins Centre, The University of Sydney, Camperdown, 2006 NSW, Australia.
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2
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Aceves M, Granados J, Leandro AC, Peralta J, Glahn DC, Williams-Blangero S, Curran JE, Blangero J, Kumar S. Role of Neurocellular Endoplasmic Reticulum Stress Response in Alzheimer's Disease and Related Dementias Risk. Genes (Basel) 2024; 15:569. [PMID: 38790197 PMCID: PMC11121587 DOI: 10.3390/genes15050569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 04/24/2024] [Accepted: 04/26/2024] [Indexed: 05/26/2024] Open
Abstract
Currently, more than 55 million people around the world suffer from dementia, and Alzheimer's Disease and Related Dementias (ADRD) accounts for nearly 60-70% of all those cases. The spread of Alzheimer's Disease (AD) pathology and progressive neurodegeneration in the hippocampus and cerebral cortex is strongly correlated with cognitive decline in AD patients; however, the molecular underpinning of ADRD's causality is still unclear. Studies of postmortem AD brains and animal models of AD suggest that elevated endoplasmic reticulum (ER) stress may have a role in ADRD pathology through altered neurocellular homeostasis in brain regions associated with learning and memory. To study the ER stress-associated neurocellular response and its effects on neurocellular homeostasis and neurogenesis, we modeled an ER stress challenge using thapsigargin (TG), a specific inhibitor of sarco/endoplasmic reticulum Ca2+ ATPase (SERCA), in the induced pluripotent stem cell (iPSC)-derived neural stem cells (NSCs) of two individuals from our Mexican American Family Study (MAFS). High-content screening and transcriptomic analysis of the control and ER stress-challenged NSCs showed that the NSCs' ER stress response resulted in a significant decline in NSC self-renewal and an increase in apoptosis and cellular oxidative stress. A total of 2300 genes were significantly (moderated t statistics FDR-corrected p-value ≤ 0.05 and fold change absolute ≥ 2.0) differentially expressed (DE). The pathway enrichment and gene network analysis of DE genes suggests that all three unfolded protein response (UPR) pathways, protein kinase RNA-like ER kinase (PERK), activating transcription factor-6 (ATF-6), and inositol-requiring enzyme-1 (IRE1), were significantly activated and cooperatively regulated the NSCs' transcriptional response to ER stress. Our results show that IRE1/X-box binding protein 1 (XBP1) mediated transcriptional regulation of the E2F transcription factor 1 (E2F1) gene, and its downstream targets have a dominant role in inducing G1/S-phase cell cycle arrest in ER stress-challenged NSCs. The ER stress-challenged NSCs also showed the activation of C/EBP homologous protein (CHOP)-mediated apoptosis and the dysregulation of synaptic plasticity and neurotransmitter homeostasis-associated genes. Overall, our results suggest that the ER stress-associated attenuation of NSC self-renewal, increased apoptosis, and dysregulated synaptic plasticity and neurotransmitter homeostasis plausibly play a role in the causation of ADRD.
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Affiliation(s)
- Miriam Aceves
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, McAllen, TX 78504, USA; (M.A.); (J.G.)
| | - Jose Granados
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, McAllen, TX 78504, USA; (M.A.); (J.G.)
| | - Ana C. Leandro
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX 78520, USA; (A.C.L.); (J.P.); (S.W.-B.); (J.E.C.); (J.B.)
| | - Juan Peralta
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX 78520, USA; (A.C.L.); (J.P.); (S.W.-B.); (J.E.C.); (J.B.)
| | - David C. Glahn
- Department of Psychiatry, Boston Children’s Hospital and Harvard Medical School, Boston, MA 02115, USA;
| | - Sarah Williams-Blangero
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX 78520, USA; (A.C.L.); (J.P.); (S.W.-B.); (J.E.C.); (J.B.)
| | - Joanne E. Curran
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX 78520, USA; (A.C.L.); (J.P.); (S.W.-B.); (J.E.C.); (J.B.)
| | - John Blangero
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX 78520, USA; (A.C.L.); (J.P.); (S.W.-B.); (J.E.C.); (J.B.)
| | - Satish Kumar
- Division of Human Genetics and South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, McAllen, TX 78504, USA; (M.A.); (J.G.)
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3
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Galanti L, Peritore M, Gnügge R, Cannavo E, Heipke J, Palumbieri MD, Steigenberger B, Symington LS, Cejka P, Pfander B. Dbf4-dependent kinase promotes cell cycle controlled resection of DNA double-strand breaks and repair by homologous recombination. Nat Commun 2024; 15:2890. [PMID: 38570537 PMCID: PMC10991553 DOI: 10.1038/s41467-024-46951-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 03/13/2024] [Indexed: 04/05/2024] Open
Abstract
DNA double-strand breaks (DSBs) can be repaired by several pathways. In eukaryotes, DSB repair pathway choice occurs at the level of DNA end resection and is controlled by the cell cycle. Upon cell cycle-dependent activation, cyclin-dependent kinases (CDKs) phosphorylate resection proteins and thereby stimulate end resection and repair by homologous recombination (HR). However, inability of CDK phospho-mimetic mutants to bypass this cell cycle regulation, suggests that additional cell cycle regulators may be important. Here, we identify Dbf4-dependent kinase (DDK) as a second major cell cycle regulator of DNA end resection. Using inducible genetic and chemical inhibition of DDK in budding yeast and human cells, we show that end resection and HR require activation by DDK. Mechanistically, DDK phosphorylates at least two resection nucleases in budding yeast: the Mre11 activator Sae2, which promotes resection initiation, as well as the Dna2 nuclease, which promotes resection elongation. Notably, synthetic activation of DDK allows limited resection and HR in G1 cells, suggesting that DDK is a key component of DSB repair pathway selection.
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Affiliation(s)
- Lorenzo Galanti
- Cell Biology, Dortmund Life Science Center (DOLCE), TU Dortmund University, Faculty of Chemistry and Chemical Biology, Dortmund, Germany
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
- Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
- Institute for Genome Stability in Aging and Disease, University of Cologne, Medical Faculty, CECAD Research Center, Cologne, Germany
| | - Martina Peritore
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
- Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
- Institute for Genome Stability in Aging and Disease, University of Cologne, Medical Faculty, CECAD Research Center, Cologne, Germany
- DSB Repair Metabolism Laboratory, The Francis Crick Institute, London, UK
| | - Robert Gnügge
- Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY, USA
| | - Elda Cannavo
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana (USI), Bellinzona, Switzerland
| | - Johannes Heipke
- Cell Biology, Dortmund Life Science Center (DOLCE), TU Dortmund University, Faculty of Chemistry and Chemical Biology, Dortmund, Germany
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
- Institute for Genome Stability in Aging and Disease, University of Cologne, Medical Faculty, CECAD Research Center, Cologne, Germany
| | - Maria Dilia Palumbieri
- Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
- Institute for Genome Stability in Aging and Disease, University of Cologne, Medical Faculty, CECAD Research Center, Cologne, Germany
- Research Group of Proteomics and ADP-Ribosylation Signaling, Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Barbara Steigenberger
- Mass Spectrometry Core Facility, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Lorraine S Symington
- Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY, USA
- Department of Genetics & Development, Columbia University Irving Medical Center, New York, NY, USA
| | - Petr Cejka
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana (USI), Bellinzona, Switzerland
- Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich, Switzerland
| | - Boris Pfander
- Cell Biology, Dortmund Life Science Center (DOLCE), TU Dortmund University, Faculty of Chemistry and Chemical Biology, Dortmund, Germany.
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany.
- Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.
- Institute for Genome Stability in Aging and Disease, University of Cologne, Medical Faculty, CECAD Research Center, Cologne, Germany.
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Willemsen M, Barber JS, Nieuwenhove EV, Staels F, Gerbaux M, Neumann J, Prezzemolo T, Pasciuto E, Lagou V, Boeckx N, Filtjens J, De Visscher A, Matthys P, Schrijvers R, Tousseyn T, O'Driscoll M, Bucciol G, Schlenner S, Meyts I, Humblet-Baron S, Liston A. Homozygous DBF4 mutation as a cause of severe congenital neutropenia. J Allergy Clin Immunol 2023; 152:266-277. [PMID: 36841265 DOI: 10.1016/j.jaci.2023.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 01/23/2023] [Accepted: 02/16/2023] [Indexed: 02/26/2023]
Abstract
BACKGROUND Severe congenital neutropenia presents with recurrent infections early in life as a result of arrested granulopoiesis. Multiple genetic defects are known to block granulocyte differentiation; however, a genetic cause remains unknown in approximately 40% of cases. OBJECTIVE We aimed to characterize a patient with severe congenital neutropenia and syndromic features without a genetic diagnosis. METHODS Whole exome sequencing results were validated using flow cytometry, Western blotting, coimmunoprecipitation, quantitative PCR, cell cycle and proliferation analysis of lymphocytes and fibroblasts and granulocytic differentiation of primary CD34+ and HL-60 cells. RESULTS We identified a homozygous missense mutation in DBF4 in a patient with mild extra-uterine growth retardation, facial dysmorphism and severe congenital neutropenia. DBF4 is the regulatory subunit of the CDC7 kinase, together known as DBF4-dependent kinase (DDK), the complex essential for DNA replication initiation. The DBF4 variant demonstrated impaired ability to bind CDC7, resulting in decreased DDK-mediated phosphorylation, defective S-phase entry and progression and impaired differentiation of granulocytes associated with activation of the p53-p21 pathway. The introduction of wild-type DBF4 into patient CD34+ cells rescued the promyelocyte differentiation arrest. CONCLUSION Hypomorphic DBF4 mutation causes autosomal-recessive severe congenital neutropenia with syndromic features.
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Affiliation(s)
- Mathijs Willemsen
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium
| | - John S Barber
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium
| | - Erika Van Nieuwenhove
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium; Department of Pediatrics, University Hospitals Leuven, Leuven, Belgium
| | - Frederik Staels
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; Department of Microbiology, Immunology, and Transplantation, Allergy and Clinical Immunology Research Group, KU Leuven, Leuven, Belgium
| | - Margaux Gerbaux
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; Pediatric Department, Academic Children Hospital Queen Fabiola, Université Libre de Bruxelles, Brussels, Belgium
| | - Julika Neumann
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium
| | - Teresa Prezzemolo
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium
| | - Emanuela Pasciuto
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium
| | - Vasiliki Lagou
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium
| | - Nancy Boeckx
- Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
| | - Jessica Filtjens
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Immunobiology, Rega Institute for Medical Research, KU Leuven, Leuve, Belgium
| | - Amber De Visscher
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Immunobiology, Rega Institute for Medical Research, KU Leuven, Leuve, Belgium
| | - Patrick Matthys
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Immunobiology, Rega Institute for Medical Research, KU Leuven, Leuve, Belgium
| | - Rik Schrijvers
- Department of Microbiology, Immunology, and Transplantation, Allergy and Clinical Immunology Research Group, KU Leuven, Leuven, Belgium
| | - Thomas Tousseyn
- Department of Pathology, University Hospitals Leuven, Leuven, Belgium
| | - Mark O'Driscoll
- Human DNA Damage Response Disorders Group, Genome Damage and Stability Centre, University of Sussex, Brighton, United Kingdom
| | - Giorgia Bucciol
- Department of Microbiology, Immunology, and Transplantation, Laboratory for Inborn Errors of Immunity, KU Leuven, Leuven, Belgium; Department of Pediatrics, Division of Primary Immunodeficiencies, University Hospitals Leuven, Leuven
| | - Susan Schlenner
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium
| | - Isabelle Meyts
- Department of Microbiology, Immunology, and Transplantation, Laboratory for Inborn Errors of Immunity, KU Leuven, Leuven, Belgium; Department of Pediatrics, Division of Primary Immunodeficiencies, University Hospitals Leuven, Leuven.
| | - Stephanie Humblet-Baron
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium.
| | - Adrian Liston
- Department of Microbiology, Immunology, and Transplantation, Laboratory of Adaptive Immunity, KU Leuven, Leuven, Belgium; VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium; Immunology Programme, The Babraham Institute, Babraham Research Campus, Cambridge, United Kingdom.
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5
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Reusswig KU, Bittmann J, Peritore M, Courtes M, Pardo B, Wierer M, Mann M, Pfander B. Unscheduled DNA replication in G1 causes genome instability and damage signatures indicative of replication collisions. Nat Commun 2022; 13:7014. [PMID: 36400763 PMCID: PMC9674678 DOI: 10.1038/s41467-022-34379-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 10/24/2022] [Indexed: 11/19/2022] Open
Abstract
DNA replicates once per cell cycle. Interfering with the regulation of DNA replication initiation generates genome instability through over-replication and has been linked to early stages of cancer development. Here, we engineer genetic systems in budding yeast to induce unscheduled replication in a G1-like cell cycle state. Unscheduled G1 replication initiates at canonical S-phase origins. We quantifiy the composition of replisomes in G1- and S-phase and identified firing factors, polymerase α, and histone supply as factors that limit replication outside S-phase. G1 replication per se does not trigger cellular checkpoints. Subsequent replication during S-phase, however, results in over-replication and leads to chromosome breaks and chromosome-wide, strand-biased occurrence of RPA-bound single-stranded DNA, indicating head-to-tail replication collisions as a key mechanism generating genome instability upon G1 replication. Low-level, sporadic induction of G1 replication induces an identical response, indicating findings from synthetic systems are applicable to naturally occurring scenarios of unscheduled replication initiation.
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Affiliation(s)
- Karl-Uwe Reusswig
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.38142.3c000000041936754XPresent Address: Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115 USA ,grid.65499.370000 0001 2106 9910Present Address: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215 USA
| | - Julia Bittmann
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Martina Peritore
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany
| | - Mathilde Courtes
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Benjamin Pardo
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Michael Wierer
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.5254.60000 0001 0674 042XPresent Address: Proteomics Research Infrastructure, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Matthias Mann
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Boris Pfander
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany ,grid.6190.e0000 0000 8580 3777Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Genome Stability in Ageing and Disease, CECAD Research Center, University of Cologne, 50931 Cologne, Germany
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6
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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: 7] [Impact Index Per Article: 2.3] [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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7
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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: 20] [Impact Index Per Article: 6.7] [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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8
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González‐Garrido C, Prado F. Novel insights into the roles of Cdc7 in response to replication stress. FEBS J 2022. [DOI: 10.1111/febs.16456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 03/01/2022] [Accepted: 04/07/2022] [Indexed: 11/26/2022]
Affiliation(s)
- Cristina González‐Garrido
- Centro Andaluz de Biología Molecular y Medicina Regenerativa–CABIMER Consejo Superior de Investigaciones Científicas Universidad de Sevilla Universidad Pablo de Olavide Spain
| | - Félix Prado
- Centro Andaluz de Biología Molecular y Medicina Regenerativa–CABIMER Consejo Superior de Investigaciones Científicas Universidad de Sevilla Universidad Pablo de Olavide Spain
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9
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Mishra PK, Wood H, Stanton J, Au WC, Eisenstatt JR, Boeckmann L, Sclafani RA, Weinreich M, Bloom KS, Thorpe PH, Basrai MA. Cdc7-mediated phosphorylation of Cse4 regulates high-fidelity chromosome segregation in budding yeast. Mol Biol Cell 2021; 32:ar15. [PMID: 34432494 PMCID: PMC8693968 DOI: 10.1091/mbc.e21-06-0323] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/11/2021] [Accepted: 08/18/2021] [Indexed: 12/21/2022] Open
Abstract
Faithful chromosome segregation maintains chromosomal stability as errors in this process contribute to chromosomal instability (CIN), which has been observed in many diseases including cancer. Epigenetic regulation of kinetochore proteins such as Cse4 (CENP-A in humans) plays a critical role in high-fidelity chromosome segregation. Here we show that Cse4 is a substrate of evolutionarily conserved Cdc7 kinase, and that Cdc7-mediated phosphorylation of Cse4 prevents CIN. We determined that Cdc7 phosphorylates Cse4 in vitro and interacts with Cse4 in vivo in a cell cycle-dependent manner. Cdc7 is required for kinetochore integrity as reduced levels of CEN-associated Cse4, a faster exchange of Cse4 at the metaphase kinetochores, and defects in chromosome segregation, are observed in a cdc7-7 strain. Phosphorylation of Cse4 by Cdc7 is important for cell survival as constitutive association of a kinase-dead variant of Cdc7 (cdc7-kd) with Cse4 at the kinetochore leads to growth defects. Moreover, phospho-deficient mutations of Cse4 for consensus Cdc7 target sites contribute to CIN phenotype. In summary, our results have defined a role for Cdc7-mediated phosphorylation of Cse4 in faithful chromosome segregation.
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Affiliation(s)
- Prashant K. Mishra
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Henry Wood
- Queen Mary University of London, London E1 4NS, UK
| | - John Stanton
- University of North Carolina, Chapel Hill, NC 27599
| | - Wei-Chun Au
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Jessica R. Eisenstatt
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Lars Boeckmann
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | | | | | | | | | - Munira A. Basrai
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
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10
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Replication initiation: Implications in genome integrity. DNA Repair (Amst) 2021; 103:103131. [PMID: 33992866 DOI: 10.1016/j.dnarep.2021.103131] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 05/07/2021] [Accepted: 05/07/2021] [Indexed: 02/01/2023]
Abstract
In every cell cycle, billions of nucleotides need to be duplicated within hours, with extraordinary precision and accuracy. The molecular mechanism by which cells regulate the replication event is very complicated, and the entire process begins way before the onset of S phase. During the G1 phase of the cell cycle, cells prepare by assembling essential replication factors to establish the pre-replicative complex at origins, sites that dictate where replication would initiate during S phase. During S phase, the replication process is tightly coupled with the DNA repair system to ensure the fidelity of replication. Defects in replication and any error must be recognized by DNA damage response and checkpoint signaling pathways in order to halt the cell cycle before cells are allowed to divide. The coordination of these processes throughout the cell cycle is therefore critical to achieve genomic integrity and prevent diseases. In this review, we focus on the current understanding of how the replication initiation events are regulated to achieve genome stability.
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11
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Structural Basis for the Activation and Target Site Specificity of CDC7 Kinase. Structure 2020; 28:954-962.e4. [PMID: 32521228 PMCID: PMC7416108 DOI: 10.1016/j.str.2020.05.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 05/11/2020] [Accepted: 05/19/2020] [Indexed: 12/13/2022]
Abstract
CDC7 is an essential Ser/Thr kinase that acts upon the replicative helicase throughout the S phase of the cell cycle and is activated by DBF4. Here, we present crystal structures of a highly active human CDC7-DBF4 construct. The structures reveal a zinc-finger domain at the end of the kinase insert 2 that pins the CDC7 activation loop to motif M of DBF4 and the C lobe of CDC7. These interactions lead to ordering of the substrate-binding platform and full opening of the kinase active site. In a co-crystal structure with a mimic of MCM2 Ser40 phosphorylation target, the invariant CDC7 residues Arg373 and Arg380 engage phospho-Ser41 at substrate P+1 position, explaining the selectivity of the S-phase kinase for Ser/Thr residues followed by a pre-phosphorylated or an acidic residue. Our results clarify the role of DBF4 in activation of CDC7 and elucidate the structural basis for recognition of its preferred substrates. DBF4 activates CDC7 kinase via a two-step mechanism Zinc-finger domain in CDC7 KI2 interacts with DBF4 motif M Invariant CDC7 residues Arg373 and Arg380 engage P+1 substrate site
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12
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Dbf4-Dependent Kinase (DDK)-Mediated Proteolysis of CENP-A Prevents Mislocalization of CENP-A in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2020; 10:2057-2068. [PMID: 32295767 PMCID: PMC7263675 DOI: 10.1534/g3.120.401131] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The evolutionarily conserved centromeric histone H3 variant (Cse4 in budding yeast, CENP-A in humans) is essential for faithful chromosome segregation. Mislocalization of CENP-A to non-centromeric chromatin contributes to chromosomal instability (CIN) in yeast, fly, and human cells and CENP-A is highly expressed and mislocalized in cancers. Defining mechanisms that prevent mislocalization of CENP-A is an area of active investigation. Ubiquitin-mediated proteolysis of overexpressed Cse4 (GALCSE4) by E3 ubiquitin ligases such as Psh1 prevents mislocalization of Cse4, and psh1 Δ strains display synthetic dosage lethality (SDL) with GALCSE4 We previously performed a genome-wide screen and identified five alleles of CDC7 and DBF4 that encode the Dbf4-dependent kinase (DDK) complex, which regulates DNA replication initiation, among the top twelve hits that displayed SDL with GALCSE4 We determined that cdc7 -7 strains exhibit defects in ubiquitin-mediated proteolysis of Cse4 and show mislocalization of Cse4 Mutation of MCM5 (mcm5 -bob1) bypasses the requirement of Cdc7 for replication initiation and rescues replication defects in a cdc7 -7 strain. We determined that mcm5 -bob1 does not rescue the SDL and defects in proteolysis of GALCSE4 in a cdc7 -7 strain, suggesting a DNA replication-independent role for Cdc7 in Cse4 proteolysis. The SDL phenotype, defects in ubiquitin-mediated proteolysis, and the mislocalization pattern of Cse4 in a cdc7 -7 psh1 Δ strain were similar to that of cdc7 -7 and psh1 Δ strains, suggesting that Cdc7 regulates Cse4 in a pathway that overlaps with Psh1 Our results define a DNA replication initiation-independent role of DDK as a regulator of Psh1-mediated proteolysis of Cse4 to prevent mislocalization of Cse4.
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13
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Reed DR, Alexandrow MG. Myc and the Replicative CMG Helicase: The Creation and Destruction of Cancer: Myc Over-Activation of CMG Helicases Drives Tumorigenesis and Creates a Vulnerability in CMGs for Therapeutic Intervention. Bioessays 2020; 42:e1900218. [PMID: 32080866 PMCID: PMC8223603 DOI: 10.1002/bies.201900218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 01/23/2020] [Indexed: 12/27/2022]
Abstract
Myc-driven tumorigenesis involves a non-transcriptional role for Myc in over-activating replicative Cdc45-MCM-GINS (CMG) helicases. Excessive stimulation of CMG helicases by Myc mismanages CMG function by diminishing the number of reserve CMGs necessary for fidelity of DNA replication and recovery from replicative stresses. One potential outcome of these events is the creation of DNA damage that alters genomic structure/function, thereby acting as a driver for tumorigenesis and tumor heterogeneity. Intriguingly, another potential outcome of this Myc-induced CMG helicase over-activation is the creation of a vulnerability in cancer whereby tumor cells specifically lack enough unused reserve CMG helicases to recover from fork-stalling drugs commonly used in chemotherapy. This review provides molecular and clinical support for this provocative hypothesis that excessive activation of CMG helicases by Myc may not only drive tumorigenesis, but also confer an exploitable "reserve CMG helicase vulnerability" that supports developing innovative CMG-focused therapeutic approaches for cancer management.
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Affiliation(s)
- Damon R Reed
- Department of Interdisciplinary Cancer Management, Moffitt Cancer Center and Research Institute, Tampa, FL, 33612, USA
| | - Mark G Alexandrow
- Department of Molecular Oncology, Moffitt Cancer Center and Research Institute, Tampa, FL, 33612, USA
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14
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Zhang H, Petrie MV, He Y, Peace JM, Chiolo IE, Aparicio OM. Dynamic relocalization of replication origins by Fkh1 requires execution of DDK function and Cdc45 loading at origins. eLife 2019; 8:45512. [PMID: 31084713 PMCID: PMC6533057 DOI: 10.7554/elife.45512] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 05/13/2019] [Indexed: 12/11/2022] Open
Abstract
Chromosomal DNA elements are organized into spatial domains within the eukaryotic nucleus. Sites undergoing DNA replication, high-level transcription, and repair of double-strand breaks coalesce into foci, although the significance and mechanisms giving rise to these dynamic structures are poorly understood. In S. cerevisiae, replication origins occupy characteristic subnuclear localizations that anticipate their initiation timing during S phase. Here, we link localization of replication origins in G1 phase with Fkh1 activity, which is required for their early replication timing. Using a Fkh1-dependent origin relocalization assay, we determine that execution of Dbf4-dependent kinase function, including Cdc45 loading, results in dynamic relocalization of a replication origin from the nuclear periphery to the interior in G1 phase. Origin mobility increases substantially with Fkh1-driven relocalization. These findings provide novel molecular insight into the mechanisms that govern dynamics and spatial organization of DNA replication origins and possibly other functional DNA elements.
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Affiliation(s)
- Haiyang Zhang
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Meghan V Petrie
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Yiwei He
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Jared M Peace
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Irene E Chiolo
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Oscar M Aparicio
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, United States
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15
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Control of Eukaryotic DNA Replication Initiation-Mechanisms to Ensure Smooth Transitions. Genes (Basel) 2019; 10:genes10020099. [PMID: 30700044 PMCID: PMC6409694 DOI: 10.3390/genes10020099] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 01/25/2019] [Accepted: 01/25/2019] [Indexed: 02/06/2023] Open
Abstract
DNA replication differs from most other processes in biology in that any error will irreversibly change the nature of the cellular progeny. DNA replication initiation, therefore, is exquisitely controlled. Deregulation of this control can result in over-replication characterized by repeated initiation events at the same replication origin. Over-replication induces DNA damage and causes genomic instability. The principal mechanism counteracting over-replication in eukaryotes is a division of replication initiation into two steps—licensing and firing—which are temporally separated and occur at distinct cell cycle phases. Here, we review this temporal replication control with a specific focus on mechanisms ensuring the faultless transition between licensing and firing phases.
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16
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Torres-Zelada EF, Stephenson RE, Alpsoy A, Anderson BD, Swanson SK, Florens L, Dykhuizen EC, Washburn MP, Weake VM. The Drosophila Dbf4 ortholog Chiffon forms a complex with Gcn5 that is necessary for histone acetylation and viability. J Cell Sci 2019; 132:jcs.214072. [PMID: 30559249 DOI: 10.1242/jcs.214072] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 12/11/2018] [Indexed: 02/05/2023] Open
Abstract
Metazoans contain two homologs of the Gcn5-binding protein Ada2, Ada2a and Ada2b, which nucleate formation of the ATAC and SAGA complexes, respectively. In Drosophila melanogaster, there are two splice isoforms of Ada2b: Ada2b-PA and Ada2b-PB. Here, we show that only the Ada2b-PB isoform is in SAGA; in contrast, Ada2b-PA associates with Gcn5, Ada3, Sgf29 and Chiffon, forming the Chiffon histone acetyltransferase (CHAT) complex. Chiffon is the Drosophila ortholog of Dbf4, which binds and activates the cell cycle kinase Cdc7 to initiate DNA replication. In flies, Chiffon and Cdc7 are required in ovary follicle cells for gene amplification, a specialized form of DNA re-replication. Although chiffon was previously reported to be dispensable for viability, here, we find that Chiffon is required for both histone acetylation and viability in flies. Surprisingly, we show that chiffon is a dicistronic gene that encodes distinct Cdc7- and CHAT-binding polypeptides. Although the Cdc7-binding domain of Chiffon is not required for viability in flies, the CHAT-binding domain is essential for viability, but is not required for gene amplification, arguing against a role in DNA replication.
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Affiliation(s)
| | - Robert E Stephenson
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Aktan Alpsoy
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| | - Benjamin D Anderson
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Selene K Swanson
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
| | - Emily C Dykhuizen
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| | - Michael P Washburn
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA.,Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Vikki M Weake
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA .,Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
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17
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Localization of Cdc7 Protein Kinase During DNA Replication in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2017; 7:3757-3774. [PMID: 28924058 PMCID: PMC5677158 DOI: 10.1534/g3.117.300223] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
DDK, a conserved serine-threonine protein kinase composed of a regulatory subunit, Dbf4, and a catalytic subunit, Cdc7, is essential for DNA replication initiation during S phase of the cell cycle through MCM2-7 helicase phosphorylation. The biological significance of DDK is well characterized, but the full mechanism of how DDK associates with substrates remains unclear. Cdc7 is bound to chromatin in the Saccharomyces cerevisiae genome throughout the cell cycle, but there is little empirical evidence as to specific Cdc7 binding locations. Using biochemical and genetic techniques, this study investigated the specific localization of Cdc7 on chromatin. The Calling Cards method, using Ty5 retrotransposons as a marker for DNA–protein binding, suggests Cdc7 kinase is preferentially bound to genomic DNA known to replicate early in S phase, including centromeres and origins of replication. We also discovered Cdc7 binding throughout the genome, which may be necessary to initiate other cellular processes, including meiotic recombination and translesion synthesis. A kinase dead Cdc7 point mutation increases the Ty5 retrotransposon integration efficiency and a 55-amino acid C-terminal truncation of Cdc7, unable to bind Dbf4, reduces Cdc7 binding suggesting a requirement for Dbf4 to stabilize Cdc7 on chromatin during S phase. Chromatin immunoprecipitation demonstrates that Cdc7 binding near specific origins changes during S phase. Our results suggest a model where Cdc7 is loosely bound to chromatin during G1. At the G1/S transition, Cdc7 binding to chromatin is increased and stabilized, preferentially at sites that may become origins, in order to carry out a variety of cellular processes.
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18
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Roles of CDK and DDK in Genome Duplication and Maintenance: Meiotic Singularities. Genes (Basel) 2017; 8:genes8030105. [PMID: 28335524 PMCID: PMC5368709 DOI: 10.3390/genes8030105] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 03/13/2017] [Accepted: 03/14/2017] [Indexed: 12/16/2022] Open
Abstract
Cells reproduce using two types of divisions: mitosis, which generates two daughter cells each with the same genomic content as the mother cell, and meiosis, which reduces the number of chromosomes of the parent cell by half and gives rise to four gametes. The mechanisms that promote the proper progression of the mitotic and meiotic cycles are highly conserved and controlled. They require the activities of two types of serine-threonine kinases, the cyclin-dependent kinases (CDKs) and the Dbf4-dependent kinase (DDK). CDK and DDK are essential for genome duplication and maintenance in both mitotic and meiotic divisions. In this review, we aim to highlight how these kinases cooperate to orchestrate diverse processes during cellular reproduction, focusing on meiosis-specific adaptions of their regulation and functions in DNA metabolism.
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19
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Parker MW, Botchan MR, Berger JM. Mechanisms and regulation of DNA replication initiation in eukaryotes. Crit Rev Biochem Mol Biol 2017; 52:107-144. [PMID: 28094588 DOI: 10.1080/10409238.2016.1274717] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cellular DNA replication is initiated through the action of multiprotein complexes that recognize replication start sites in the chromosome (termed origins) and facilitate duplex DNA melting within these regions. In a typical cell cycle, initiation occurs only once per origin and each round of replication is tightly coupled to cell division. To avoid aberrant origin firing and re-replication, eukaryotes tightly regulate two events in the initiation process: loading of the replicative helicase, MCM2-7, onto chromatin by the origin recognition complex (ORC), and subsequent activation of the helicase by its incorporation into a complex known as the CMG. Recent work has begun to reveal the details of an orchestrated and sequential exchange of initiation factors on DNA that give rise to a replication-competent complex, the replisome. Here, we review the molecular mechanisms that underpin eukaryotic DNA replication initiation - from selecting replication start sites to replicative helicase loading and activation - and describe how these events are often distinctly regulated across different eukaryotic model organisms.
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Affiliation(s)
- Matthew W Parker
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Michael R Botchan
- b Department of Molecular and Cell Biology , University of California Berkeley , Berkeley , CA , USA
| | - James M Berger
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
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20
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Duncker BP. Mechanisms Governing DDK Regulation of the Initiation of DNA Replication. Genes (Basel) 2016; 8:genes8010003. [PMID: 28025497 PMCID: PMC5294998 DOI: 10.3390/genes8010003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 12/13/2016] [Accepted: 12/16/2016] [Indexed: 12/14/2022] Open
Abstract
The budding yeast Dbf4-dependent kinase (DDK) complex—comprised of cell division cycle (Cdc7) kinase and its regulatory subunit dumbbell former 4 (Dbf4)—is required to trigger the initiation of DNA replication through the phosphorylation of multiple minichromosome maintenance complex subunits 2-7 (Mcm2-7). DDK is also a target of the radiation sensitive 53 (Rad53) checkpoint kinase in response to replication stress. Numerous investigations have determined mechanistic details, including the regions of Mcm2, Mcm4, and Mcm6 phosphorylated by DDK, and a number of DDK docking sites. Similarly, the way in which the Rad53 forkhead-associated 1 (FHA1) domain binds to DDK—involving both canonical and non-canonical interactions—has been elucidated. Recent work has revealed mutual promotion of DDK and synthetic lethal with dpb11-1 3 (Sld3) roles. While DDK phosphorylation of Mcm2-7 subunits facilitates their interaction with Sld3 at origins, Sld3 in turn stimulates DDK phosphorylation of Mcm2. Details of a mutually antagonistic relationship between DDK and Rap1-interacting factor 1 (Rif1) have also recently come to light. While Rif1 is able to reverse DDK-mediated Mcm2-7 complex phosphorylation by targeting the protein phosphatase glycogen 7 (Glc7) to origins, there is evidence to suggest that DDK can counteract this activity by binding to and phosphorylating Rif1.
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Affiliation(s)
- Bernard P Duncker
- Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L3G1, Canada.
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21
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Kylie K, Romero J, Lindamulage IK, Knockleby J, Lee H. Dynamic regulation of histone H3K9 is linked to the switch between replication and transcription at the Dbf4 origin-promoter locus. Cell Cycle 2016; 15:2321-35. [PMID: 27341472 PMCID: PMC5004705 DOI: 10.1080/15384101.2016.1201254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 05/20/2016] [Accepted: 06/08/2016] [Indexed: 02/07/2023] Open
Abstract
The co-regulation of DNA replication and gene transcription is still poorly understood. To gain a better understanding of this important control mechanism, we examined the DNA replication and transcription using the Dbf4 origin-promoter and Dbf4 pseudogene models. We found that origin firing and Dbf4 transcription activity were inversely regulated in a cell cycle-dependent manner. We also found that proteins critical for the regulation of replication (ORC, MCM), transcription (SP1, TFIIB), and cohesin (Smc1, Smc3) and Mediator functions (Med1, Med12) interact with specific sites within and the surrounding regions of the Dbf4 locus in a cell cycle-dependent manner. As expected, replication initiation occurred within a nucleosome-depleted region, and nucleosomes flanked the 2 replication initiation zones. Further, the histone H3 in this region was distinctly acetylated or trimethylated on lysine 9 in a cell cycle-dependent fluctuation pattern: H3K9ac was most prevalent when the Dbf4 transcription level was highest whereas the H3K9me3 level was greatest during and just after replication. The KDM4A histone demethylase, which is responsible for the H3K9me3 modification, was enriched at the Dbf4 origin in a manner coinciding with H3K9me3. Finally, HP1γ, a protein known to interact with H3K9me3 in the heterochromatin was also found enriched at the origin during DNA replication, indicating that H3K9me3 may be required for the regulation of replication at both heterochromatin and euchromatin regions. Taken together, our data show that mammalian cells employ an extremely sophisticated and multilayered co-regulation mechanism for replication and transcription in a highly coordinated manner.
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Affiliation(s)
- Kathleen Kylie
- Tumour Biology Group, Health Sciences North Research Institute, Sudbury, Ontario, Canada
| | - Julia Romero
- Tumour Biology Group, Health Sciences North Research Institute, Sudbury, Ontario, Canada
| | | | - James Knockleby
- Tumour Biology Group, Health Sciences North Research Institute, Sudbury, Ontario, Canada
| | - Hoyun Lee
- Tumour Biology Group, Health Sciences North Research Institute, Sudbury, Ontario, Canada
- Department of Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
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22
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Knockleby J, Kim BJ, Mehta A, Lee H. Cdk1-mediated phosphorylation of Cdc7 suppresses DNA re-replication. Cell Cycle 2016; 15:1494-505. [PMID: 27105124 PMCID: PMC4934051 DOI: 10.1080/15384101.2016.1176658] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 03/23/2016] [Accepted: 04/06/2016] [Indexed: 12/18/2022] Open
Abstract
To maintain genetic stability, the entire mammalian genome must replicate only once per cell cycle. This is largely achieved by strictly regulating the stepwise formation of the pre-replication complex (pre-RC), followed by the activation of individual origins of DNA replication by Cdc7/Dbf4 kinase. However, the mechanism how Cdc7 itself is regulated in the context of cell cycle progression is poorly understood. Here we report that Cdc7 is phosphorylated by a Cdk1-dependent manner during prometaphase on multiple sites, resulting in its dissociation from origins. In contrast, Dbf4 is not removed from origins in prometaphase, nor is it degraded as cells exit mitosis. Our data thus demonstrates that constitutive phosphorylation of Cdc7 at Cdk1 recognition sites, but not the regulation of Dbf4, prevents the initiation of DNA replication in normally cycling cells and under conditions that promote re-replication in G2/M. As cells exit mitosis, PP1α associates with and dephosphorylates Cdc7. Together, our data support a model where Cdc7 (de)phosphorylation is the molecular switch for the activation and inactivation of DNA replication in mitosis, directly connecting Cdc7 and PP1α/Cdk1 to the regulation of once-per-cell cycle DNA replication in mammalian cells.
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Affiliation(s)
- James Knockleby
- Tumour Biology Group, Advanced Medical Research Institute of Canada, Health Sciences North, Sudbury, Ontario, Canada
| | - Byung Ju Kim
- Tumour Biology Group, Advanced Medical Research Institute of Canada, Health Sciences North, Sudbury, Ontario, Canada
| | - Avani Mehta
- Tumour Biology Group, Advanced Medical Research Institute of Canada, Health Sciences North, Sudbury, Ontario, Canada
| | - Hoyun Lee
- Tumour Biology Group, Advanced Medical Research Institute of Canada, Health Sciences North, Sudbury, Ontario, Canada
- Departments of Medicine, the Faculty of Medicine, the University of Ottawa, Ottawa, Ontario, Canada
- Northern Ontario School of Medicine, Sudbury, Ontario, Canada
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23
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Sasi NK, Tiwari K, Soon FF, Bonte D, Wang T, Melcher K, Xu HE, Weinreich M. The potent Cdc7-Dbf4 (DDK) kinase inhibitor XL413 has limited activity in many cancer cell lines and discovery of potential new DDK inhibitor scaffolds. PLoS One 2014; 9:e113300. [PMID: 25412417 PMCID: PMC4239038 DOI: 10.1371/journal.pone.0113300] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 10/23/2014] [Indexed: 12/16/2022] Open
Abstract
Cdc7-Dbf4 kinase or DDK (Dbf4-dependent kinase) is required to initiate DNA replication by phosphorylating and activating the replicative Mcm2-7 DNA helicase. DDK is overexpressed in many tumor cells and is an emerging chemotherapeutic target since DDK inhibition causes apoptosis of diverse cancer cell types but not of normal cells. PHA-767491 and XL413 are among a number of potent DDK inhibitors with low nanomolar IC50 values against the purified kinase. Although XL413 is highly selective for DDK, its activity has not been extensively characterized on cell lines. We measured anti-proliferative and apoptotic effects of XL413 on a panel of tumor cell lines compared to PHA-767491, whose activity is well characterized. Both compounds were effective biochemical DDK inhibitors but surprisingly, their activities in cell lines were highly divergent. Unlike PHA-767491, XL413 had significant anti-proliferative activity against only one of the ten cell lines tested. Since XL413 did not effectively inhibit DDK in multiple cell lines, this compound likely has limited bioavailability. To identify potential leads for additional DDK inhibitors, we also tested the cross-reactivity of ∼400 known kinase inhibitors against DDK using a DDK thermal stability shift assay (TSA). We identified 11 compounds that significantly stabilized DDK. Several inhibited DDK with comparable potency to PHA-767491, including Chk1 and PKR kinase inhibitors, but had divergent chemical scaffolds from known DDK inhibitors. Taken together, these data show that several well-known kinase inhibitors cross-react with DDK and also highlight the opportunity to design additional specific, biologically active DDK inhibitors for use as chemotherapeutic agents.
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Affiliation(s)
- Nanda Kumar Sasi
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute (VARI), Grand Rapids, MI, United States of America
- Graduate Program in Genetics, Michigan State University, East Lansing, MI, United States of America
| | - Kanchan Tiwari
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute (VARI), Grand Rapids, MI, United States of America
| | - Fen-Fen Soon
- Laboratory of Structural Sciences, VARI, Grand Rapids, MI, United States of America
| | - Dorine Bonte
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute (VARI), Grand Rapids, MI, United States of America
| | - Tong Wang
- Translational Drug Development, Inc. (TD2), Scottsdale, AZ, United States of America
| | - Karsten Melcher
- Laboratory of Structural Biology and Biochemistry, VARI, Grand Rapids, MI, United States of America
| | - H. Eric Xu
- Laboratory of Structural Sciences, VARI, Grand Rapids, MI, United States of America
| | - Michael Weinreich
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute (VARI), Grand Rapids, MI, United States of America
- * E-mail:
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Tognetti S, Riera A, Speck C. Switch on the engine: how the eukaryotic replicative helicase MCM2-7 becomes activated. Chromosoma 2014; 124:13-26. [PMID: 25308420 DOI: 10.1007/s00412-014-0489-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Revised: 09/24/2014] [Accepted: 09/25/2014] [Indexed: 12/17/2022]
Abstract
A crucial step during eukaryotic initiation of DNA replication is the correct loading and activation of the replicative DNA helicase, which ensures that each replication origin fires only once. Unregulated DNA helicase loading and activation, as it occurs in cancer, can cause severe DNA damage and genomic instability. The essential mini-chromosome maintenance proteins 2-7 (MCM2-7) represent the core of the eukaryotic replicative helicase that is loaded at DNA replication origins during G1-phase of the cell cycle. The MCM2-7 helicase activity, however, is only triggered during S-phase once the holo-helicase Cdc45-MCM2-7-GINS (CMG) has been formed. A large number of factors and several kinases interact and contribute to CMG formation and helicase activation, though the exact mechanisms remain unclear. Crucially, upon DNA damage, this reaction is temporarily halted to ensure genome integrity. Here, we review the current understanding of helicase activation; we focus on protein interactions during CMG formation, discuss structural changes during helicase activation, and outline similarities and differences of the prokaryotic and eukaryotic helicase activation process.
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Affiliation(s)
- Silvia Tognetti
- DNA Replication Group, Institute of Clinical Science, Imperial College, London, W12 0NN, UK
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Lu D, Hsiao JY, Davey NE, Van Voorhis VA, Foster SA, Tang C, Morgan DO. Multiple mechanisms determine the order of APC/C substrate degradation in mitosis. ACTA ACUST UNITED AC 2014; 207:23-39. [PMID: 25287299 PMCID: PMC4195823 DOI: 10.1083/jcb.201402041] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
To ensure proper mitotic progression, robust ordering of the destruction of APC/CCdc20 substrates is driven by the integration of molecular mechanisms ranging from phosphorylation-dependent interaction with substrates to sensing of the status of the spindle assembly checkpoint. The ubiquitin protein ligase anaphase-promoting complex or cyclosome (APC/C) controls mitosis by promoting ordered degradation of securin, cyclins, and other proteins. The mechanisms underlying the timing of APC/C substrate degradation are poorly understood. We explored these mechanisms using quantitative fluorescence microscopy of GFP-tagged APC/CCdc20 substrates in living budding yeast cells. Degradation of the S cyclin, Clb5, begins early in mitosis, followed 6 min later by the degradation of securin and Dbf4. Anaphase begins when less than half of securin is degraded. The spindle assembly checkpoint delays the onset of Clb5 degradation but does not influence securin degradation. Early Clb5 degradation depends on its interaction with the Cdk1–Cks1 complex and the presence of a Cdc20-binding “ABBA motif” in its N-terminal region. The degradation of securin and Dbf4 is delayed by Cdk1-dependent phosphorylation near their Cdc20-binding sites. Thus, a remarkably diverse array of mechanisms generates robust ordering of APC/CCdc20 substrate destruction.
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Affiliation(s)
- Dan Lu
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Jennifer Y Hsiao
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Norman E Davey
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Vanessa A Van Voorhis
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Scott A Foster
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Chao Tang
- Center for Quantitative Biology and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - David O Morgan
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
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26
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Brandão LN, Ferguson R, Santoro I, Jinks-Robertson S, Sclafani RA. The role of Dbf4-dependent protein kinase in DNA polymerase ζ-dependent mutagenesis in Saccharomyces cerevisiae. Genetics 2014; 197:1111-22. [PMID: 24875188 PMCID: PMC4125387 DOI: 10.1534/genetics.114.165308] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 05/23/2014] [Indexed: 11/18/2022] Open
Abstract
The yeast Dbf4-dependent kinase (DDK) (composed of Dbf4 and Cdc7 subunits) is an essential, conserved Ser/Thr protein kinase that regulates multiple processes in the cell, including DNA replication, recombination and induced mutagenesis. Only DDK substrates important for replication and recombination have been identified. Consequently, the mechanism by which DDK regulates mutagenesis is unknown. The yeast mcm5-bob1 mutation that bypasses DDK's essential role in DNA replication was used here to examine whether loss of DDK affects spontaneous as well as induced mutagenesis. Using the sensitive lys2ΔA746 frameshift reversion assay, we show DDK is required to generate "complex" spontaneous mutations, which are a hallmark of the Polζ translesion synthesis DNA polymerase. DDK co-immunoprecipitated with the Rev7 regulatory, but not with the Rev3 polymerase subunit of Polζ. Conversely, Rev7 bound mainly to the Cdc7 kinase subunit and not to Dbf4. The Rev7 subunit of Polζ may be regulated by DDK phosphorylation as immunoprecipitates of yeast Cdc7 and also recombinant Xenopus DDK phosphorylated GST-Rev7 in vitro. In addition to promoting Polζ-dependent mutagenesis, DDK was also important for generating Polζ-independent large deletions that revert the lys2ΔA746 allele. The decrease in large deletions observed in the absence of DDK likely results from an increase in the rate of replication fork restart after an encounter with spontaneous DNA damage. Finally, nonepistatic, additive/synergistic UV sensitivity was observed in cdc7Δ pol32Δ and cdc7Δ pol30-K127R,K164R double mutants, suggesting that DDK may regulate Rev7 protein during postreplication "gap filling" rather than during "polymerase switching" by ubiquitinated and sumoylated modified Pol30 (PCNA) and Pol32.
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Affiliation(s)
- Luis N Brandão
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Rebecca Ferguson
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Irma Santoro
- Department of Biology, Emory University, Atlanta, Georgia 30322
| | - Sue Jinks-Robertson
- Department of Biology, Emory University, Atlanta, Georgia 30322 Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710
| | - Robert A Sclafani
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045
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Hiraga SI, Alvino GM, Chang F, Lian HY, Sridhar A, Kubota T, Brewer BJ, Weinreich M, Raghuraman MK, Donaldson AD. Rif1 controls DNA replication by directing Protein Phosphatase 1 to reverse Cdc7-mediated phosphorylation of the MCM complex. Genes Dev 2014; 28:372-83. [PMID: 24532715 PMCID: PMC3937515 DOI: 10.1101/gad.231258.113] [Citation(s) in RCA: 180] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Initiation of eukaryotic DNA replication requires phosphorylation of the MCM complex by Dbf4-dependent kinase (DDK), composed of Cdc7 kinase and its activator, Dbf4. We report here that budding yeast Rif1 (Rap1-interacting factor 1) controls DNA replication genome-wide and describe how Rif1 opposes DDK function by directing Protein Phosphatase 1 (PP1)-mediated dephosphorylation of the MCM complex. Deleting RIF1 partially compensates for the limited DDK activity in a cdc7-1 mutant strain by allowing increased, premature phosphorylation of Mcm4. PP1 interaction motifs within the Rif1 N-terminal domain are critical for its repressive effect on replication. We confirm that Rif1 interacts with PP1 and that PP1 prevents premature Mcm4 phosphorylation. Remarkably, our results suggest that replication repression by Rif1 is itself also DDK-regulated through phosphorylation near the PP1-interacting motifs. Based on our findings, we propose that Rif1 is a novel PP1 substrate targeting subunit that counteracts DDK-mediated phosphorylation during replication. Fission yeast and mammalian Rif1 proteins have also been implicated in regulating DNA replication. Since PP1 interaction sites are evolutionarily conserved within the Rif1 sequence, it is likely that replication control by Rif1 through PP1 is a conserved mechanism.
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Affiliation(s)
- Shin-Ichiro Hiraga
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
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28
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Tanaka S, Araki H. Helicase activation and establishment of replication forks at chromosomal origins of replication. Cold Spring Harb Perspect Biol 2013; 5:a010371. [PMID: 23881938 DOI: 10.1101/cshperspect.a010371] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Many replication proteins assemble on the pre-RC-formed replication origins and constitute the pre-initiation complex (pre-IC). This complex formation facilitates the conversion of Mcm2-7 in the pre-RC to an active DNA helicase, the Cdc45-Mcm-GINS (CMG) complex. Two protein kinases, cyclin-dependent kinase (CDK) and Dbf4-dependent kinase (DDK), work to complete the formation of the pre-IC. Each kinase is responsible for a distinct step of the process in yeast; Cdc45 associates with origins in a DDK-dependent manner, whereas the association of GINS with origins depends on CDK. These associations with origins also require specific initiation proteins: Sld3 for Cdc45; and Dpb11, Sld2, and Sld3 for GINS. Functional homologs of these proteins exist in metazoa, although pre-IC formation cannot be separated by requirement of DDK and CDK because of experimental limitations. Once the replicative helicase is activated, the origin DNA is unwound, and bidirectional replication forks are established.
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Affiliation(s)
- Seiji Tanaka
- Division of Microbial Genetics, National Institute of Genetics, and Department of Genetics, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
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29
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Wu X, Zeng H, Zhu X, Ma Q, Hou Y, Wu X. Novel pyrrolopyridinone derivatives as anticancer inhibitors towards Cdc7: QSAR studies based on dockings by solvation score approach. Eur J Pharm Sci 2013; 50:323-34. [DOI: 10.1016/j.ejps.2013.07.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2013] [Revised: 07/11/2013] [Accepted: 07/29/2013] [Indexed: 10/26/2022]
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Abstract
DNA replication is tightly controlled in eukaryotic cells to ensure that an exact copy of the genetic material is inherited by both daughter cells. Oscillating waves of cyclin-dependent kinase (CDK) and anaphase-promoting complex/cyclosome (APC/C) activities provide a binary switch that permits the replication of each chromosome exactly once per cell cycle. Work from several organisms has revealed a conserved strategy whereby inactive replication complexes are assembled onto DNA during periods of low CDK and high APC activity but are competent to execute genome duplication only when these activities are reversed. Periods of high CDK and low APC/C serve an essential function by blocking reassembly of replication complexes, thereby preventing rereplication. Higher eukaryotes have evolved additional CDK-independent mechanisms for preventing rereplication.
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Affiliation(s)
- Khalid Siddiqui
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, United Kingdom
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31
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Liachko NF, McMillan PJ, Guthrie CR, Bird TD, Leverenz JB, Kraemer BC. CDC7 inhibition blocks pathological TDP-43 phosphorylation and neurodegeneration. Ann Neurol 2013; 74:39-52. [PMID: 23424178 DOI: 10.1002/ana.23870] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 12/14/2012] [Accepted: 01/25/2013] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Kinase hyperactivity occurs in both neurodegenerative disease and cancer. Lesions containing hyperphosphorylated aggregated TDP-43 characterize amyotrophic lateral sclerosis and frontotemporal lobar degeneration with TDP-43 inclusions. Dual phosphorylation of TDP-43 at serines 409/410 (S409/410) drives neurotoxicity in disease models; therefore, TDP-43-specific kinases are candidate targets for intervention. METHODS To find therapeutic targets for the prevention of TDP-43 phosphorylation, we assembled and screened a comprehensive RNA interference library targeting kinases in TDP-43 transgenic Caenorhabditis elegans. RESULTS We show CDC7 robustly phosphorylates TDP-43 at pathological residues S409/410 in C. elegans, in vitro, and in human cell culture. In frontotemporal lobar degeneration (FTLD)-TDP cases, CDC7 immunostaining overlaps with the phospho-TDP-43 pathology found in frontal cortex. Furthermore, PHA767491, a small molecule inhibitor of CDC7, reduces TDP-43 phosphorylation and prevents TDP-43-dependent neurodegeneration in TDP-43-transgenic animals. INTERPRETATION Taken together, these data support CDC7 as a novel therapeutic target for TDP-43 proteinopathies, including FTLD-TDP and amyotrophic lateral sclerosis.
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Affiliation(s)
- Nicole F Liachko
- Geriatric Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, WA; Department of Medicine, University of Washington, Seattle, WA
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32
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Zhong Y, Nellimoottil T, Peace JM, Knott SRV, Villwock SK, Yee JM, Jancuska JM, Rege S, Tecklenburg M, Sclafani RA, Tavaré S, Aparicio OM. The level of origin firing inversely affects the rate of replication fork progression. ACTA ACUST UNITED AC 2013; 201:373-83. [PMID: 23629964 PMCID: PMC3639389 DOI: 10.1083/jcb.201208060] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cells with reduced origin firing have an increased rate of replication fork progression, whereas fork progression is slowed in cells with excess origins. DNA damage slows DNA synthesis at replication forks; however, the mechanisms remain unclear. Cdc7 kinase is required for replication origin activation, is a target of the intra-S checkpoint, and is implicated in the response to replication fork stress. Remarkably, we found that replication forks proceed more rapidly in cells lacking Cdc7 function than in wild-type cells. We traced this effect to reduced origin firing, which results in fewer replication forks and a consequent decrease in Rad53 checkpoint signaling. Depletion of Orc1, which acts in origin firing differently than Cdc7, had similar effects as Cdc7 depletion, consistent with decreased origin firing being the source of these defects. In contrast, mec1-100 cells, which initiate excess origins and also are deficient in checkpoint activation, showed slower fork progression, suggesting the number of active forks influences their rate, perhaps as a result of competition for limiting factors.
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Affiliation(s)
- Yuan Zhong
- Molecular and Computational Biology Program, University of Southern California, Los Angeles, CA 90089, USA
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33
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Lyons NA, Fonslow BR, Diedrich JK, Yates JR, Morgan DO. Sequential primed kinases create a damage-responsive phosphodegron on Eco1. Nat Struct Mol Biol 2013; 20:194-201. [PMID: 23314252 PMCID: PMC3565030 DOI: 10.1038/nsmb.2478] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 11/27/2012] [Indexed: 02/06/2023]
Abstract
Sister-chromatid cohesion is established during S phase when Eco1 acetylates cohesin. In budding yeast, Eco1 activity falls after S phase due to Cdk1-dependent phosphorylation, which triggers ubiquitination by SCF(Cdc4). We show here that Eco1 degradation requires the sequential actions of Cdk1 and two additional kinases, Cdc7-Dbf4 and the GSK-3 homolog Mck1. These kinases recognize motifs primed by previous phosphorylation, resulting in an ordered sequence of three phosphorylation events on Eco1. Only the latter two phosphorylation sites are spaced correctly to bind Cdc4, resulting in strict discrimination between phosphates added by Cdk1 and by Cdc7. Inhibition of Cdc7 by the DNA damage response prevents Eco1 destruction, allowing establishment of cohesion after S phase. This elaborate regulatory system, involving three independent kinases and stringent substrate selection by a ubiquitin ligase, enables robust control of cohesion establishment during normal growth and after stress.
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Affiliation(s)
- Nicholas A Lyons
- Department of Physiology, University of California, San Francisco, San Francisco, California, USA
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34
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Rengaraj D, Lee BR, Choi JW, Lee SI, Seo HW, Kim TH, Choi HJ, Song G, Han JY. Gene pathways and cell cycle-related genes in cultured avian primordial germ cells. Poult Sci 2013; 91:3167-77. [PMID: 23155027 DOI: 10.3382/ps.2012-02279] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Primordial germ cells (PGC) from early embryos are applicable to various kinds of research, including the production of transgenic animals. Primordial germ cells eventually migrate and differentiate into germ cells in the gonads, where they settle and rapidly proliferate. However, the proliferation rate of PGC is low in early embryos, and there are many significant pathways that mediate PGC activity. Therefore, in vitro culture of PGC from early embryos with efficient growth factors has been necessary. Recently, we cultured chicken PGC from embryonic d 2.5 with basic fibroblast growth factor and characterized the PGC through analysis of cell morphology, survival, proliferation, and apoptosis. However, large-scale analyses of genes expressed in cultured PGC and the genes involved in associated pathways are limited. The objective of the present investigation was to identify the signaling and metabolic pathways of expressed genes by microarray comparison between PGC and their somatic counterpart, chicken embryonic fibroblasts (CEF). We identified 795 genes that were expressed more predominantly in PGC and 824 genes that were expressed more predominantly in CEF. Among the predominant genes in PGC, 201 were differentially identified in 106 pathways. Among the predominant genes in CEF, 242 were differentially identified in 99 pathways. To further validate the genes involved in at least one candidate pathway, those involved in the cell cycle (12 predominant genes in PGC and 8 predominant genes in CEF) were examined by real-time PCR. To the best of our knowledge, this study is the first to investigate signaling and metabolic pathways in cultured PGC.
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Affiliation(s)
- D Rengaraj
- Department of Agricultural Biotechnology and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea
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35
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Hughes S, Elustondo F, Di Fonzo A, Leroux FG, Wong AC, Snijders AP, Matthews SJ, Cherepanov P. Crystal structure of human CDC7 kinase in complex with its activator DBF4. Nat Struct Mol Biol 2012; 19:1101-7. [PMID: 23064647 DOI: 10.1038/nsmb.2404] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 09/07/2012] [Indexed: 11/09/2022]
Abstract
CDC7 is a serine/threonine kinase that is essential for the initiation of eukaryotic DNA replication. CDC7 activity is controlled by its activator, DBF4. Here we present crystal structures of human CDC7-DBF4 in complex with a nucleotide or ATP-competing small molecules, revealing the active and inhibited forms of the kinase, respectively. DBF4 wraps around CDC7, burying approximately 6,000 Å(2) of hydrophobic molecular surface in a bipartite interface. The effector domain of DBF4, containing conserved motif C, is essential and sufficient to support CDC7 kinase activity by binding to the kinase N-terminal lobe and stabilizing its canonical αC helix. DBF4 motif M latches onto the C-terminal lobe of the kinase, acting as a tethering domain. Our results elucidate the structural basis for binding to and activation of CDC7 by DBF4 and provide a framework for the design of more potent and specific CDC7 inhibitors.
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Affiliation(s)
- Siobhan Hughes
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, Potters Bar, UK
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36
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Gidvani RD, Sudmant P, Li G, DaSilva LF, McConkey BJ, Duncker BP, Ingalls BP. A quantitative model of the initiation of DNA replication in Saccharomyces cerevisiae predicts the effects of system perturbations. BMC SYSTEMS BIOLOGY 2012; 6:78. [PMID: 22738223 PMCID: PMC3439281 DOI: 10.1186/1752-0509-6-78] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 06/05/2012] [Indexed: 11/17/2022]
Abstract
Background Eukaryotic cell proliferation involves DNA replication, a tightly regulated process mediated by a multitude of protein factors. In budding yeast, the initiation of replication is facilitated by the heterohexameric origin recognition complex (ORC). ORC binds to specific origins of replication and then serves as a scaffold for the recruitment of other factors such as Cdt1, Cdc6, the Mcm2-7 complex, Cdc45 and the Dbf4-Cdc7 kinase complex. While many of the mechanisms controlling these associations are well documented, mathematical models are needed to explore the network’s dynamic behaviour. We have developed an ordinary differential equation-based model of the protein-protein interaction network describing replication initiation. Results The model was validated against quantified levels of protein factors over a range of cell cycle timepoints. Using chromatin extracts from synchronized Saccharomyces cerevisiae cell cultures, we were able to monitor the in vivo fluctuations of several of the aforementioned proteins, with additional data obtained from the literature. The model behaviour conforms to perturbation trials previously reported in the literature, and accurately predicts the results of our own knockdown experiments. Furthermore, we successfully incorporated our replication initiation model into an established model of the entire yeast cell cycle, thus providing a comprehensive description of these processes. Conclusions This study establishes a robust model of the processes driving DNA replication initiation. The model was validated against observed cell concentrations of the driving factors, and characterizes the interactions between factors implicated in eukaryotic DNA replication. Finally, this model can serve as a guide in efforts to generate a comprehensive model of the mammalian cell cycle in order to explore cancer-related phenotypes.
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Affiliation(s)
- Rohan D Gidvani
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
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37
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Tanaka S, Araki H. Multiple regulatory mechanisms to inhibit untimely initiation of DNA replication are important for stable genome maintenance. PLoS Genet 2011; 7:e1002136. [PMID: 21698130 PMCID: PMC3116906 DOI: 10.1371/journal.pgen.1002136] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 05/01/2011] [Indexed: 12/28/2022] Open
Abstract
Genomic instability is a hallmark of human cancer cells. To prevent genomic instability, chromosomal DNA is faithfully duplicated in every cell division cycle, and eukaryotic cells have complex regulatory mechanisms to achieve this goal. Here, we show that untimely activation of replication origins during the G1 phase is genotoxic and induces genomic instability in the budding yeast Saccharomyces cerevisiae. Our data indicate that cells preserve a low level of the initiation factor Sld2 to prevent untimely initiation during the normal cell cycle in addition to controlling the phosphorylation of Sld2 and Sld3 by cyclin-dependent kinase. Although untimely activation of origin is inhibited on multiple levels, we show that deregulation of a single pathway can cause genomic instability, such as gross chromosome rearrangements (GCRs). Furthermore, simultaneous deregulation of multiple pathways causes an even more severe phenotype. These findings highlight the importance of having multiple inhibitory mechanisms to prevent the untimely initiation of chromosome replication to preserve stable genome maintenance over generations in eukaryotes. Chromosomal DNA replication occurs as a two-step reaction in eukaryotes. In the first reaction, called licensing, the replicative helicase is loaded onto replication origin in an inactive form during the G1 phase of the cell cycle. In the second reaction, called initiation, the replicative helicase is activated, and replication forks are established. Because of this two-step mechanism, licensing and initiation must occur at different times in the cell cycle. Failure of this two-step regulation will cause heterogeneous re-replication of chromosomal DNA, and genome integrity will be lost. Although previous works have established that multiple regulatory pathways regulate licensing, much less is known about how untimely (premature) initiation is prevented during the G1 phase. In this paper, we show that untimely activation of replication origins during the G1 phase is inhibited on multiple levels. Notably, deregulation of a single pathway can cause genomic instability; simultaneous deregulation of multiple pathways causes a more severe phenotype, such as aneuploidy. Therefore, these findings not only indicate the importance of having multiple inhibitory mechanisms to prevent untimely initiation of chromosome replication but also should help us understand how replication might be deregulated in human cancer cells, in which the genome is frequently destabilized.
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Affiliation(s)
- Seiji Tanaka
- Division of Microbial Genetics, National Institute of Genetics, Mishima, Japan.
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38
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Regulation of the initiation step of DNA replication by cyclin-dependent kinases. Chromosoma 2010; 119:565-74. [DOI: 10.1007/s00412-010-0291-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 07/23/2010] [Accepted: 07/23/2010] [Indexed: 12/20/2022]
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Hughes S, Jenkins V, Dar MJ, Engelman A, Cherepanov P. Transcriptional co-activator LEDGF interacts with Cdc7-activator of S-phase kinase (ASK) and stimulates its enzymatic activity. J Biol Chem 2009; 285:541-54. [PMID: 19864417 DOI: 10.1074/jbc.m109.036491] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Lens epithelium-derived growth factor (LEDGF) is an important co-factor of human immunodeficiency virus DNA integration; however, its cellular functions are poorly characterized. We now report identification of the Cdc7-activator of S-phase kinase (ASK) heterodimer as a novel interactor of LEDGF. Both kinase subunits co-immunoprecipitated with endogenous LEDGF from human cell extracts. Truncation analyses identified the integrase-binding domain of LEDGF as essential and minimally sufficient for the interaction with Cdc7-ASK. Reciprocally, the interaction required autophosphorylation of the kinase and the presence of 50 C-terminal residues of ASK. The kinase phosphorylated LEDGF in vitro, with Ser-206 being the major target, and LEDGF phosphorylated at this residue could be detected during S phase of the cell cycle. LEDGF potently stimulated the enzymatic activity of Cdc7-ASK, increasing phosphorylation of MCM2 in vitro by more than 10-fold. This enzymatic stimulation as well as phosphorylation of LEDGF depended on the protein-protein interaction. Intriguingly, removing the C-terminal region of ASK, involved in the interaction with LEDGF, resulted in a hyperactive kinase. Our results indicate that the interaction with LEDGF relieves autoinhibition of Cdc7-ASK kinase, imposed by the C terminus of ASK.
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Affiliation(s)
- Siobhan Hughes
- Division of Medicine, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, United Kingdom and
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40
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Budding yeast Dbf4 sequences required for Cdc7 kinase activation and identification of a functional relationship between the Dbf4 and Rev1 BRCT domains. Genetics 2009; 183:1269-82. [PMID: 19822727 DOI: 10.1534/genetics.109.110155] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Cdc7-Dbf4 is a two-subunit kinase required for initiating DNA replication. The Dbf4 regulatory subunit is required for Cdc7 kinase activity. Previous studies have shown that the C termini of Dbf4 orthologs encode a single (putative) C(2)H(2) zinc (Zn) finger, referred to as "motif C." By mutational analysis we show that the Zn finger is not required for the essential function of Dbf4. However, deletion and point mutants altering conserved Zn-finger residues exhibit a substantially slowed S-phase, DNA damage sensitivity, and a hypo-mutagenic phenotype following UV irradiation. Using two-hybrid and biochemical assays, we show that the Dbf4 Zn finger interacts with Cdc7 and stimulates its kinase activity. However, a separable Dbf4 region also mediates an interaction with Cdc7 such that only the loss of both Cdc7-interacting regions results in lethality. In contrast, an N-terminal BRCT-like domain is not required for induced mutagenesis nor does it interact with Cdc7. By making chimeric Dbf4 proteins that contain known BRCT domains in Saccharomyces cerevisiae, we show that the BRCT domain from Rev1, a translesion DNA polymerase, can uniquely substitute for the Dbf4 BRCT domain. Thus, we have mapped regions on budding yeast Dbf4 required for binding and activating Cdc7 kinase. Our data also suggest that the Dbf4 and Rev1 BRCT domains interact with a common protein or structure, although the precise function of both domains and their binding partners remains elusive.
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41
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Bruck I, Kaplan D. Dbf4-Cdc7 phosphorylation of Mcm2 is required for cell growth. J Biol Chem 2009; 284:28823-31. [PMID: 19692334 DOI: 10.1074/jbc.m109.039123] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Dbf4-Cdc7 kinase (DDK) is required for the activation of the origins of replication, and DDK phosphorylates Mcm2 in vitro. We find that budding yeast Cdc7 alone exists in solution as a weakly active multimer. Dbf4 forms a likely heterodimer with Cdc7, and this species phosphorylates Mcm2 with substantially higher specific activity. Dbf4 alone binds tightly to Mcm2, whereas Cdc7 alone binds weakly to Mcm2, suggesting that Dbf4 recruits Cdc7 to phosphorylate Mcm2. DDK phosphorylates two serine residues of Mcm2 near the N terminus of the protein, Ser-164 and Ser-170. Expression of mcm2-S170A is lethal to yeast cells that lack endogenous MCM2 (mcm2Delta); however, this lethality is rescued in cells harboring the DDK bypass mutant mcm5-bob1. We conclude that DDK phosphorylation of Mcm2 is required for cell growth.
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Affiliation(s)
- Irina Bruck
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA
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42
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Miller CT, Gabrielse C, Chen YC, Weinreich M. Cdc7p-Dbf4p regulates mitotic exit by inhibiting Polo kinase. PLoS Genet 2009; 5:e1000498. [PMID: 19478884 PMCID: PMC2682205 DOI: 10.1371/journal.pgen.1000498] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 04/29/2009] [Indexed: 01/14/2023] Open
Abstract
Cdc7p-Dbf4p is a conserved protein kinase required for the initiation of DNA replication. The Dbf4p regulatory subunit binds Cdc7p and is essential for Cdc7p kinase activation, however, the N-terminal third of Dbf4p is dispensable for its essential replication activities. Here, we define a short N-terminal Dbf4p region that targets Cdc7p-Dbf4p kinase to Cdc5p, the single Polo kinase in budding yeast that regulates mitotic progression and cytokinesis. Dbf4p mediates an interaction with the Polo substrate-binding domain to inhibit its essential role during mitosis. Although Dbf4p does not inhibit Polo kinase activity, it nonetheless inhibits Polo-mediated activation of the mitotic exit network (MEN), presumably by altering Polo substrate targeting. In addition, although dbf4 mutants defective for interaction with Polo transit S-phase normally, they aberrantly segregate chromosomes following nuclear misorientation. Therefore, Cdc7p-Dbf4p prevents inappropriate exit from mitosis by inhibiting Polo kinase and functions in the spindle position checkpoint. Cdc7p-Dbf4p is a two-subunit enzyme required to copy the genetic material present on every chromosome in a process termed DNA replication. Dbf4p is an essential regulatory subunit of this enzyme that likely directs the Cdc7p subunit to its targets within the cell. We found that Dbf4p physically interacts with another protein called Polo that acts during mitosis, a later step in the cell cycle when the newly copied chromosomes are equally divided to mother and daughter cells. Polo is a master regulator of mitosis and impacts many other proteins required for cell division. We determined that Cdc7p-Dbf4p is a Polo inhibitor and, further, that Cdc7p-Dbf4p delayed or prevented chromosome segregation when errors occurred during the cell division process. Interestingly, Dbf4p may bind the Polo substrate-binding domain using a type of interaction not previously described. Thus, we have uncovered a new activity for Cdc7p-Dbf4p in the cell cycle to inhibit chromosome segregation, and these findings impact multiple fields that investigate how cells accurately copy and segregate their chromosomes.
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Affiliation(s)
- Charles T. Miller
- Graduate Program in Cell and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
- Laboratory of Chromosome Replication, Van Andel Research Institute, Grand Rapids, Michigan, United States of America
| | - Carrie Gabrielse
- Laboratory of Chromosome Replication, Van Andel Research Institute, Grand Rapids, Michigan, United States of America
| | - Ying-Chou Chen
- Laboratory of Chromosome Replication, Van Andel Research Institute, Grand Rapids, Michigan, United States of America
- Graduate Program in Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Michael Weinreich
- Laboratory of Chromosome Replication, Van Andel Research Institute, Grand Rapids, Michigan, United States of America
- * E-mail:
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43
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Kakusho N, Taniyama C, Masai H. Identification of Stimulators and Inhibitors of Cdc7 Kinase in Vitro. J Biol Chem 2008; 283:19211-8. [DOI: 10.1074/jbc.m803113200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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44
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Papamichos-Chronakis M, Peterson CL. The Ino80 chromatin-remodeling enzyme regulates replisome function and stability. Nat Struct Mol Biol 2008; 15:338-45. [PMID: 18376411 DOI: 10.1038/nsmb.1413] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Accepted: 03/04/2008] [Indexed: 12/29/2022]
Abstract
Previous studies have demonstrated essential roles for ATP-dependent chromatin-remodeling and chromatin-modifying enzymes in gene transcription and DNA repair, but few studies have addressed how the replication machinery deals with chromatin. Here we show that the Ino80 remodeling enzyme is recruited to replication origins as cells enter S phase. Inducible degradation of Ino80 shows that it is required continuously for efficient progression of forks, especially when cells are confronted with low levels of replication stress. Furthermore, we show that stalling of replication forks in an ino80 mutant is a lethal event, and that much of the replication machinery dissociates from the stalled fork. Our data indicate that the chromatin-remodeling activity of Ino80 regulates efficient progression of replication forks and that Ino80 has a crucial role in stabilizing a stalled replisome to ensure proper restart of DNA replication.
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Affiliation(s)
- Manolis Papamichos-Chronakis
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Biotechnology 2, Suite 210, Worcester, Massachusetts 01605, USA
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Nambiar S, Mirmohammadsadegh A, Hassan M, Mota R, Marini A, Alaoui A, Tannapfel A, Hegemann JH, Hengge UR. Identification and functional characterization of ASK/Dbf4, a novel cell survival gene in cutaneous melanoma with prognostic relevance. Carcinogenesis 2007; 28:2501-10. [PMID: 17768177 DOI: 10.1093/carcin/bgm197] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Malignant melanoma is one of the most aggressive and invasive metastatic tumors derived from melanocytes that have undergone malignant transformation by acquisition of genetic and epigenetic alterations. Oligonucleotide microarray-based screening of distinct stages in the tumor progression model of cutaneous melanoma identified ASK/Dbf4, as a novel determinant for melanoma development. Quantitative real-time polymerase chain reaction-based confirmation of ASK/Dbf4 on a series of benign nevi, dysplastic nevi, primary cutaneous melanomas and cutaneous melanoma metastases; and a number of other controls using normal human melanocytes as calibrator not only revealed a melanoma-specific over-expression but also revealed that higher ASK/Dbf4-expressing melanomas were associated with lower relapse-free survival. Additionally, we also confirmed the observed over-expression of ASK/Dbf4 in melanoma using western blot analysis and immunohistochemistry. As ASK/Dbf4 is known to be a cyclin-like regulatory subunit of mammalian Cdc7 from the studies in yeast, the present study investigated its role in melanoma cells. In keeping with its expected role, our data suggest that up-regulated ASK/Dbf4 is localized in the nucleus and binds to human Cdc7 to form Cdc7-ASK/Dbf4 complexes in several analyzed melanoma cell lines. Further, we demonstrate that small interfering RNA-mediated depletion of ASK/Dbf4 retarded melanoma cell survival and proliferation. In summary, we report the differential regulation of a novel gene, namely ASK/Dbf4, in melanoma and suggest that up-regulation of ASK/Dbf4 is a novel molecular determinant with prognostic relevance that confers a proliferative advantage in cutaneous melanoma.
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Affiliation(s)
- Sandeep Nambiar
- Department of Dermatology, Heinrich-Heine-University, Moorenstrasse 5, Duesseldorf D-40225, Germany
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Hoang ML, Leon RP, Pessoa-Brandao L, Hunt S, Raghuraman MK, Fangman WL, Brewer BJ, Sclafani RA. Structural changes in Mcm5 protein bypass Cdc7-Dbf4 function and reduce replication origin efficiency in Saccharomyces cerevisiae. Mol Cell Biol 2007; 27:7594-602. [PMID: 17724082 PMCID: PMC2169039 DOI: 10.1128/mcb.00997-07] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Eukaryotic chromosomal replication is a complicated process with many origins firing at different efficiencies and times during S phase. Prereplication complexes are assembled on all origins in G(1) phase, and yet only a subset of complexes is activated during S phase by DDK (for Dbf4-dependent kinase) (Cdc7-Dbf4). The yeast mcm5-bob1 (P83L) mutation bypasses DDK but results in reduced intrinsic firing efficiency at 11 endogenous origins and at origins located on minichromosomes. Origin efficiency may result from Mcm5 protein assuming an altered conformation, as predicted from the atomic structure of an archaeal MCM (for minichromosome maintenance) homologue. Similarly, an intragenic mutation in a residue predicted to interact with P83L suppresses the mcm5-bob1 bypass phenotype. We propose DDK phosphorylation of the MCM complex normally results in a single, highly active conformation of Mcm5, whereas the mcm5-bob1 mutation produces a number of conformations, only one of which is permissive for origin activation. Random adoption of these alternate states by the mcm5-bob1 protein can explain both how origin firing occurs independently of DDK and why origin efficiency is reduced. Because similar mutations in mcm2 and mcm4 cannot bypass DDK, Mcm5 protein may be a unique Mcm protein that is the final target of DDK regulation.
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Affiliation(s)
- Margaret L Hoang
- Department of Genome Sciences, University of Washington, Seattle, USA
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47
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Arias EE, Walter JC. Strength in numbers: preventing rereplication via multiple mechanisms in eukaryotic cells. Genes Dev 2007; 21:497-518. [PMID: 17344412 DOI: 10.1101/gad.1508907] [Citation(s) in RCA: 319] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In eukaryotic cells, prereplication complexes (pre-RCs) are assembled on chromatin in the G1 phase, rendering origins of DNA replication competent to initiate DNA synthesis. When DNA replication commences in S phase, pre-RCs are disassembled, and multiple initiations from the same origin do not occur because new rounds of pre-RC assembly are inhibited. In most experimental organisms, multiple mechanisms that prevent pre-RC assembly have now been identified, and rereplication within the same cell cycle can be induced through defined perturbations of these mechanisms. This review summarizes the diverse array of inhibitory pathways used by different organisms to prevent pre-RC assembly, and focuses on the challenge of understanding how in any one cell type, various mechanisms cooperate to strictly enforce once per cell cycle regulation of DNA replication.
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Affiliation(s)
- Emily E Arias
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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48
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Rubenstein EM, Schmidt MC. Mechanisms regulating the protein kinases of Saccharomyces cerevisiae. EUKARYOTIC CELL 2007; 6:571-83. [PMID: 17337635 PMCID: PMC1865659 DOI: 10.1128/ec.00026-07] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Eric M Rubenstein
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, W1247 Biomedical Science Tower, Pittsburgh, PA 15261, USA
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49
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Abstract
Eukaryotic DNA replication is regulated to ensure all chromosomes replicate once and only once per cell cycle. Replication begins at many origins scattered along each chromosome. Except for budding yeast, origins are not defined DNA sequences and probably are inherited by epigenetic mechanisms. Initiation at origins occurs throughout the S phase according to a temporal program that is important in regulating gene expression during development. Most replication proteins are conserved in evolution in eukaryotes and archaea, but not in bacteria. However, the mechanism of initiation is conserved and consists of origin recognition, assembly of prereplication (pre-RC) initiative complexes, helicase activation, and replisome loading. Cell cycle regulation by protein phosphorylation ensures that pre-RC assembly can only occur in G1 phase, whereas helicase activation and loading can only occur in S phase. Checkpoint regulation maintains high fidelity by stabilizing replication forks and preventing cell cycle progression during replication stress or damage.
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Affiliation(s)
- R. A. Sclafani
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045; ,
| | - T. M. Holzen
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045; ,
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50
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Zegerman P, Diffley JFX. Phosphorylation of Sld2 and Sld3 by cyclin-dependent kinases promotes DNA replication in budding yeast. Nature 2006; 445:281-5. [PMID: 17167417 DOI: 10.1038/nature05432] [Citation(s) in RCA: 380] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Accepted: 11/10/2006] [Indexed: 12/23/2022]
Abstract
Cyclin-dependent kinases (CDKs) drive major cell cycle events including the initiation of chromosomal DNA replication. We identified two S phase CDK (S-CDK) phosphorylation sites in the budding yeast Sld3 protein that, together, are essential for DNA replication. Here we show that, when phosphorylated, these sites bind to the amino-terminal BRCT repeats of Dpb11. An Sld3-Dpb11 fusion construct bypasses the requirement for both Sld3 phosphorylation and the N-terminal BRCT repeats of Dpb11. Co-expression of this fusion with a phospho-mimicking mutant in a second essential CDK substrate, Sld2, promotes DNA replication in the absence of S-CDK. Therefore, Sld2 and Sld3 are the minimal set of S-CDK targets required for DNA replication. DNA replication in cells lacking G1 phase CDK (G1-CDK) required expression of the Cdc7 kinase regulatory subunit, Dbf4, as well as Sld2 and Sld3 bypass. Our results help to explain how G1- and S-CDKs promote DNA replication in yeast.
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Affiliation(s)
- Philip Zegerman
- Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire EN6 3LD, UK
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