1
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Aktar K, Davies T, Leontiou I, Clark I, Spanos C, Wallace E, Tuck L, Jeyaprakash AA, Hardwick KG. Conserved signalling functions for Mps1, Mad1 and Mad2 in the Cryptococcus neoformans spindle checkpoint. PLoS Genet 2024; 20:e1011302. [PMID: 38829899 DOI: 10.1371/journal.pgen.1011302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 05/14/2024] [Indexed: 06/05/2024] Open
Abstract
Cryptococcus neoformans is an opportunistic, human fungal pathogen which undergoes fascinating switches in cell cycle control and ploidy when it encounters stressful environments such as the human lung. Here we carry out a mechanistic analysis of the spindle checkpoint which regulates the metaphase to anaphase transition, focusing on Mps1 kinase and the downstream checkpoint components Mad1 and Mad2. We demonstrate that Cryptococcus mad1Δ or mad2Δ strains are unable to respond to microtubule perturbations, continuing to re-bud and divide, and die as a consequence. Fluorescent tagging of Chromosome 3, using a lacO array and mNeonGreen-lacI fusion protein, demonstrates that mad mutants are unable to maintain sister-chromatid cohesion in the absence of microtubule polymers. Thus, the classic checkpoint functions of the SAC are conserved in Cryptococcus. In interphase, GFP-Mad1 is enriched at the nuclear periphery, and it is recruited to unattached kinetochores in mitosis. Purification of GFP-Mad1 followed by mass spectrometric analysis of associated proteins show that it forms a complex with Mad2 and that it interacts with other checkpoint signalling components (Bub1) and effectors (Cdc20 and APC/C sub-units) in mitosis. We also demonstrate that overexpression of Mps1 kinase is sufficient to arrest Cryptococcus cells in mitosis, and show that this arrest is dependent on both Mad1 and Mad2. We find that a C-terminal fragment of Mad1 is an effective in vitro substrate for Mps1 kinase and map several Mad1 phosphorylation sites. Some sites are highly conserved within the C-terminal Mad1 structure and we demonstrate that mutation of threonine 667 (T667A) leads to loss of checkpoint signalling and abrogation of the GAL-MPS1 arrest. Thus Mps1-dependent phosphorylation of C-terminal Mad1 residues is a critical step in Cryptococcus spindle checkpoint signalling. We conclude that CnMps1 protein kinase, Mad1 and Mad2 proteins have all conserved their important, spindle checkpoint signalling roles helping ensure high fidelity chromosome segregation.
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Affiliation(s)
- Koly Aktar
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Thomas Davies
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Ioanna Leontiou
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Ivan Clark
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Christos Spanos
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Edward Wallace
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Laura Tuck
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - A Arockia Jeyaprakash
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- Gene Center, Department of Biochemistry, Ludwig Maximilians Universitat, Munich, Germany
| | - Kevin G Hardwick
- Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
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2
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Basier C, Nurse P. TOR regulates variability of protein synthesis rates. EMBO J 2024; 43:1618-1633. [PMID: 38499788 PMCID: PMC11021518 DOI: 10.1038/s44318-024-00075-8] [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: 10/23/2023] [Revised: 02/20/2024] [Accepted: 02/23/2024] [Indexed: 03/20/2024] Open
Abstract
Cellular processes are subject to inherent variability, but the extent to which cells can regulate this variability has received little investigation. Here, we explore the characteristics of the rate of cellular protein synthesis in single cells of the eukaryote fission yeast. Strikingly, this rate is highly variable despite protein synthesis being dependent on hundreds of reactions which might be expected to average out at the overall cellular level. The rate is variable over short time scales, and exhibits homoeostatic behaviour at the population level. Cells can regulate the level of variability through processes involving the TOR pathway, suggesting there is an optimal level of variability conferring a selective advantage. While this could be an example of bet-hedging, but we propose an alternative explanation: regulated 'loose' control of complex processes of overall cellular metabolism such as protein synthesis, may lead to this variability. This could ensure cells are fluid in control and agile in response to changing conditions, and may constitute a novel organisational principle of complex metabolic cellular systems.
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Affiliation(s)
- Clovis Basier
- Cell Cycle Laboratory, The Francis Crick Institute, London, NW1 1AT, UK.
| | - Paul Nurse
- Cell Cycle Laboratory, The Francis Crick Institute, London, NW1 1AT, UK
- Laboratory of Yeast Genetics and Cell Biology, Rockefeller University, New York, NY, 10065, USA
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3
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Chen C, Piano V, Alex A, Han SJY, Huis In 't Veld PJ, Roy B, Fergle D, Musacchio A, Joglekar AP. The structural flexibility of MAD1 facilitates the assembly of the Mitotic Checkpoint Complex. Nat Commun 2023; 14:1529. [PMID: 36934097 PMCID: PMC10024682 DOI: 10.1038/s41467-023-37235-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: 06/26/2022] [Accepted: 03/08/2023] [Indexed: 03/20/2023] Open
Abstract
The spindle assembly checkpoint (SAC) safeguards the genome during cell division by generating an effector molecule known as the Mitotic Checkpoint Complex (MCC). The MCC comprises two subcomplexes: BUBR1:BUB3 and CDC20:MAD2, and the formation of CDC20:MAD2 is the rate-limiting step during MCC assembly. Recent studies show that the rate of CDC20:MAD2 formation is significantly accelerated by the cooperative binding of CDC20 to the SAC proteins MAD1 and BUB1. However, the molecular basis for this acceleration is not fully understood. Here, we demonstrate that the structural flexibility of MAD1 at a conserved hinge near the C-terminus is essential for catalytic MCC assembly. This MAD1 hinge enables the MAD1:MAD2 complex to assume a folded conformation in vivo. Importantly, truncating the hinge reduces the rate of MCC assembly in vitro and SAC signaling in vivo. Conversely, mutations that preserve hinge flexibility retain SAC signaling, indicating that the structural flexibility of the hinge, rather than a specific amino acid sequence, is important for SAC signaling. We summarize these observations as the 'knitting model' that explains how the folded conformation of MAD1:MAD2 promotes CDC20:MAD2 assembly.
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Affiliation(s)
- Chu Chen
- Biophysics, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Molecular Genetics of Ageing, Max Planck Institute for Biology of Ageing, Cologne, 50931, Germany
| | - Valentina Piano
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
- Institute of Human Genetics, University Hospital Cologne, Cologne, 50931, Germany
| | - Amal Alex
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
| | - Simon J Y Han
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
- Medical Scientist Training Program, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Pim J Huis In 't Veld
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
| | - Babhrubahan Roy
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Daniel Fergle
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Andrea Musacchio
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, 44227, Germany
- Centre for Medical Biotechnology, Faculty of Biology, University Duisburg-Essen, Essen, 45141, Germany
| | - Ajit P Joglekar
- Biophysics, University of Michigan, Ann Arbor, MI, 48109, USA.
- Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.
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4
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Fischer ES. Kinetochore‐catalyzed MCC
formation: A structural perspective. IUBMB Life 2022; 75:289-310. [PMID: 36518060 DOI: 10.1002/iub.2697] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/08/2022] [Indexed: 12/23/2022]
Abstract
The spindle assembly checkpoint (SAC) is a cellular surveillance mechanism that functions to ensure accurate chromosome segregation during mitosis. Macromolecular complexes known as kinetochores, act as the interface of sister chromatid attachment to spindle microtubules. In response to unattached kinetochores, the SAC activates its effector, the mitotic checkpoint complex (MCC), which delays mitotic exit until all sister chromatid pairs have achieved successful attachment to the bipolar mitotic spindle. Formation of the MCC (composed of Mad2, BubR1, Bub3 and Cdc20) is regulated by an Mps1 kinase-dependent phosphorylation signaling cascade which assembles and repositions components of the MCC onto a catalytic scaffold. This scaffold functions to catalyze the conversion of the HORMA-domain protein Mad2 from an "inactive" open-state (O-Mad2) into an "active" closed-Mad2 (C-Mad2), and simultaneous Cdc20 binding. Here, our current understanding of the molecular mechanisms underlying the kinetic barrier to C-Mad2:Cdc20 formation will be reviewed. Recent progress in elucidating the precise molecular choreography orchestrated by the catalytic scaffold to rapidly assemble the MCC will be examined, and unresolved questions will be highlighted. Ultimately, understanding how the SAC rapidly activates the checkpoint not only provides insights into how cells maintain genomic integrity during mitosis, but also provides a paradigm for how cells can utilize molecular switches, including other HORMA domain-containing proteins, to make rapid changes to a cell's physiological state.
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Affiliation(s)
- Elyse S. Fischer
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus Cambridge UK
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5
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Villarroya-Beltri C, Osorio A, Torres-Ruiz R, Gómez-Sánchez D, Trakala M, Sánchez-Belmonte A, Mercadillo F, Hurtado B, Pitarch B, Hernández-Núñez A, Gómez-Caturla A, Rueda D, Perea J, Rodríguez-Perales S, Malumbres M, Urioste M. Biallelic germline mutations in MAD1L1 induce a syndrome of aneuploidy with high tumor susceptibility. SCIENCE ADVANCES 2022; 8:eabq5914. [PMID: 36322655 PMCID: PMC9629740 DOI: 10.1126/sciadv.abq5914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
Germline mutations leading to aneuploidy are rare, and their tumor-promoting properties are mostly unknown at the molecular level. We report here novel germline biallelic mutations in MAD1L1, encoding the spindle assembly checkpoint (SAC) protein MAD1, in a 36-year-old female with a dozen of neoplasias. Functional studies demonstrated lack of full-length protein and deficient SAC response, resulting in ~30 to 40% of aneuploid blood cells. Single-cell RNA analysis identified mitochondrial stress accompanied by systemic inflammation with enhanced interferon and NFκB signaling both in aneuploid and euploid cells, suggesting a non-cell autonomous response. MAD1L1 mutations resulted in specific clonal expansions of γδ T cells with chromosome 18 gains and enhanced cytotoxic profile as well as intermediate B cells with chromosome 12 gains and transcriptomic signatures characteristic of leukemia cells. These data point to MAD1L1 mutations as the cause of a new variant of mosaic variegated aneuploidy with systemic inflammation and unprecedented tumor susceptibility.
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Affiliation(s)
| | - Ana Osorio
- Familial Cancer Clinical Unit, CNIO, Madrid E-28029, Spain
| | - Raúl Torres-Ruiz
- Cytogenetic Unit, CNIO, Madrid E-28029, Spain
- Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
- Advanced Therapies Unit, Hematopoietic Innovative Therapies Division, Instituto de Investigación Sanitaria Fundacion Jimenez Díaz (IIS-FJD, UAM), Madrid E-28040, Spain
| | - David Gómez-Sánchez
- Hereditary Cancer Laboratory, Doce de Octubre University Hospital, i+12 Research Institute, Madrid, Spain
- Clinical and Translational Lung Cancer Research Unit, i+12 Research Institute and Biomedical Research Networking Center in Oncology (CIBERONC), Madrid, Spain
| | - Marianna Trakala
- Koch Institute, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Agustin Sánchez-Belmonte
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid E-28029, Spain
| | | | - Begoña Hurtado
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid E-28029, Spain
| | - Borja Pitarch
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid E-28029, Spain
| | | | | | - Daniel Rueda
- Hereditary Cancer Laboratory, Doce de Octubre University Hospital, i+12 Research Institute, Madrid, Spain
| | - José Perea
- Molecular Medicine Unit, Department of Medicine, Biomedical Research Institute of Salamanca (IBSAL), Salamanca, Spain
- Surgery Department, Vithas Madrid Arturo Soria Hospital, Madrid, Spain
| | | | - Marcos Malumbres
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid E-28029, Spain
| | - Miguel Urioste
- Familial Cancer Clinical Unit, CNIO, Madrid E-28029, Spain
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6
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Fischer ES, Yu CWH, Hevler JF, McLaughlin SH, Maslen SL, Heck AJR, Freund SMV, Barford D. Juxtaposition of Bub1 and Cdc20 on phosphorylated Mad1 during catalytic mitotic checkpoint complex assembly. Nat Commun 2022; 13:6381. [PMID: 36289199 PMCID: PMC9605988 DOI: 10.1038/s41467-022-34058-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 10/11/2022] [Indexed: 12/25/2022] Open
Abstract
In response to improper kinetochore-microtubule attachments in mitosis, the spindle assembly checkpoint (SAC) assembles the mitotic checkpoint complex (MCC) to inhibit the anaphase-promoting complex/cyclosome, thereby delaying entry into anaphase. The MCC comprises Mad2:Cdc20:BubR1:Bub3. Its assembly is catalysed by unattached kinetochores on a Mad1:Mad2 platform. Mad1-bound closed-Mad2 (C-Mad2) recruits open-Mad2 (O-Mad2) through self-dimerization. This interaction, combined with Mps1 kinase-mediated phosphorylation of Bub1 and Mad1, accelerates MCC assembly, in a process that requires O-Mad2 to C-Mad2 conversion and concomitant binding of Cdc20. How Mad1 phosphorylation catalyses MCC assembly is poorly understood. Here, we characterized Mps1 phosphorylation of Mad1 and obtained structural insights into a phosphorylation-specific Mad1:Cdc20 interaction. This interaction, together with the Mps1-phosphorylation dependent association of Bub1 and Mad1, generates a tripartite assembly of Bub1 and Cdc20 onto the C-terminal domain of Mad1 (Mad1CTD). We additionally identify flexibility of Mad1:Mad2 that suggests how the Cdc20:Mad1CTD interaction brings the Mad2-interacting motif (MIM) of Cdc20 near O-Mad2. Thus, Mps1-dependent formation of the MCC-assembly scaffold functions to position and orient Cdc20 MIM near O-Mad2, thereby catalysing formation of C-Mad2:Cdc20.
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Affiliation(s)
- Elyse S Fischer
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
| | - Conny W H Yu
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Johannes F Hevler
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, 3584 CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, University of Utrecht, 3584 CH, Utrecht, The Netherlands
| | - Stephen H McLaughlin
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Sarah L Maslen
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, 3584 CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, University of Utrecht, 3584 CH, Utrecht, The Netherlands
| | - Stefan M V Freund
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - David Barford
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
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7
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Esposito E, Weidemann DE, Rogers JM, Morton CM, Baybay EK, Chen J, Hauf S. Mitotic checkpoint gene expression is tuned by codon usage bias. EMBO J 2022; 41:e107896. [PMID: 35811551 PMCID: PMC9340482 DOI: 10.15252/embj.2021107896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 05/30/2022] [Accepted: 06/06/2022] [Indexed: 11/09/2022] Open
Abstract
The mitotic checkpoint (also called spindle assembly checkpoint, SAC) is a signaling pathway that safeguards proper chromosome segregation. Correct functioning of the SAC depends on adequate protein concentrations and appropriate stoichiometries between SAC proteins. Yet very little is known about the regulation of SAC gene expression. Here, we show in the fission yeast Schizosaccharomyces pombe that a combination of short mRNA half-lives and long protein half-lives supports stable SAC protein levels. For the SAC genes mad2+ and mad3+ , their short mRNA half-lives are caused, in part, by a high frequency of nonoptimal codons. In contrast, mad1+ mRNA has a short half-life despite a higher frequency of optimal codons, and despite the lack of known RNA-destabilizing motifs. Hence, different SAC genes employ different strategies of expression. We further show that Mad1 homodimers form co-translationally, which may necessitate a certain codon usage pattern. Taken together, we propose that the codon usage of SAC genes is fine-tuned to ensure proper SAC function. Our work shines light on gene expression features that promote spindle assembly checkpoint function and suggests that synonymous mutations may weaken the checkpoint.
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Affiliation(s)
- Eric Esposito
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.,Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, USA
| | - Douglas E Weidemann
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.,Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, USA
| | - Jessie M Rogers
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.,Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, USA
| | - Claire M Morton
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.,Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, USA
| | - Erod Keaton Baybay
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.,Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, USA
| | - Jing Chen
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.,Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, USA
| | - Silke Hauf
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.,Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, USA
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8
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Elowe S, Bolanos-Garcia VM. The spindle checkpoint proteins BUB1 and BUBR1: (SLiM)ming down to the basics. Trends Biochem Sci 2022; 47:352-366. [DOI: 10.1016/j.tibs.2022.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 12/16/2022]
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9
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Lara-Gonzalez P, Pines J, Desai A. Spindle assembly checkpoint activation and silencing at kinetochores. Semin Cell Dev Biol 2021; 117:86-98. [PMID: 34210579 PMCID: PMC8406419 DOI: 10.1016/j.semcdb.2021.06.009] [Citation(s) in RCA: 94] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 06/17/2021] [Accepted: 06/17/2021] [Indexed: 01/01/2023]
Abstract
The spindle assembly checkpoint (SAC) is a surveillance mechanism that promotes accurate chromosome segregation in mitosis. The checkpoint senses the attachment state of kinetochores, the proteinaceous structures that assemble onto chromosomes in mitosis in order to mediate their interaction with spindle microtubules. When unattached, kinetochores generate a diffusible inhibitor that blocks the activity of the anaphase-promoting complex/cyclosome (APC/C), an E3 ubiquitin ligase required for sister chromatid separation and exit from mitosis. Work from the past decade has greatly illuminated our understanding of the mechanisms by which the diffusible inhibitor is assembled and how it inhibits the APC/C. However, less is understood about how SAC proteins are recruited to kinetochores in the absence of microtubule attachment, how the kinetochore catalyzes formation of the diffusible inhibitor, and how attachments silence the SAC at the kinetochore. Here, we summarize current understanding of the mechanisms that activate and silence the SAC at kinetochores and highlight open questions for future investigation.
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Affiliation(s)
- Pablo Lara-Gonzalez
- Ludwig Institute for Cancer Research, USA; Department of Cellular & Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA.
| | | | - Arshad Desai
- Ludwig Institute for Cancer Research, USA; Department of Cellular & Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA.
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10
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Fischer ES, Yu CWH, Bellini D, McLaughlin SH, Orr CM, Wagner A, Freund SMV, Barford D. Molecular mechanism of Mad1 kinetochore targeting by phosphorylated Bub1. EMBO Rep 2021; 22:e52242. [PMID: 34013668 PMCID: PMC8391104 DOI: 10.15252/embr.202052242] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 04/02/2021] [Accepted: 04/13/2021] [Indexed: 01/10/2023] Open
Abstract
During metaphase, in response to improper kinetochore-microtubule attachments, the spindle assembly checkpoint (SAC) activates the mitotic checkpoint complex (MCC), an inhibitor of the anaphase-promoting complex/cyclosome (APC/C). This process is orchestrated by the kinase Mps1, which initiates the assembly of the MCC onto kinetochores through a sequential phosphorylation-dependent signalling cascade. The Mad1-Mad2 complex, which is required to catalyse MCC formation, is targeted to kinetochores through a direct interaction with the phosphorylated conserved domain 1 (CD1) of Bub1. Here, we present the crystal structure of the C-terminal domain of Mad1 (Mad1CTD ) bound to two phosphorylated Bub1CD1 peptides at 1.75 Å resolution. This interaction is mediated by phosphorylated Bub1 Thr461, which not only directly interacts with Arg617 of the Mad1 RLK (Arg-Leu-Lys) motif, but also directly acts as an N-terminal cap to the CD1 α-helix dipole. Surprisingly, only one Bub1CD1 peptide binds to the Mad1 homodimer in solution. We suggest that this stoichiometry is due to inherent asymmetry in the coiled-coil of Mad1CTD and has implications for how the Mad1-Bub1 complex at kinetochores promotes efficient MCC assembly.
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Affiliation(s)
| | | | - Dom Bellini
- MRC Laboratory of Molecular BiologyCambridgeUK
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11
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Lara-Gonzalez P, Kim T, Oegema K, Corbett K, Desai A. A tripartite mechanism catalyzes Mad2-Cdc20 assembly at unattached kinetochores. Science 2021; 371:64-67. [PMID: 33384372 DOI: 10.1126/science.abc1424] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 11/17/2020] [Indexed: 12/22/2022]
Abstract
During cell division, kinetochores couple chromosomes to spindle microtubules. To protect against chromosome gain or loss, kinetochores lacking microtubule attachment locally catalyze association of the checkpoint proteins Cdc20 and Mad2, which is the key event in the formation of a diffusible checkpoint complex that prevents mitotic exit. We elucidated the mechanism of kinetochore-catalyzed Mad2-Cdc20 assembly with a probe that specifically monitors this assembly reaction at kinetochores in living cells. We found that catalysis occurs through a tripartite mechanism that includes localized delivery of Mad2 and Cdc20 substrates and two phosphorylation-dependent interactions that geometrically constrain their positions and prime Cdc20 for interaction with Mad2. These results reveal how unattached kinetochores create a signal that ensures genome integrity during cell division.
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Affiliation(s)
- Pablo Lara-Gonzalez
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA. .,Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA.,Ludwig Institute for Cancer Research, San Diego Branch, 9500 Gilman Drive, La Jolla, CA, USA
| | - Taekyung Kim
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA.,Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA.,Ludwig Institute for Cancer Research, San Diego Branch, 9500 Gilman Drive, La Jolla, CA, USA
| | - Karen Oegema
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA.,Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA.,Ludwig Institute for Cancer Research, San Diego Branch, 9500 Gilman Drive, La Jolla, CA, USA
| | - Kevin Corbett
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA.,Ludwig Institute for Cancer Research, San Diego Branch, 9500 Gilman Drive, La Jolla, CA, USA
| | - Arshad Desai
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA. .,Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, USA.,Ludwig Institute for Cancer Research, San Diego Branch, 9500 Gilman Drive, La Jolla, CA, USA
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12
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Piano V, Alex A, Stege P, Maffini S, Stoppiello GA, Huis In 't Veld PJ, Vetter IR, Musacchio A. CDC20 assists its catalytic incorporation in the mitotic checkpoint complex. Science 2021; 371:67-71. [PMID: 33384373 DOI: 10.1126/science.abc1152] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 11/18/2020] [Indexed: 12/16/2022]
Abstract
Open (O) and closed (C) topologies of HORMA-domain proteins are respectively associated with inactive and active states of fundamental cellular pathways. The HORMA protein O-MAD2 converts to C-MAD2 upon binding CDC20. This is rate limiting for assembly of the mitotic checkpoint complex (MCC), the effector of a checkpoint required for mitotic fidelity. A catalyst assembled at kinetochores accelerates MAD2:CDC20 association through a poorly understood mechanism. Using a reconstituted SAC system, we discovered that CDC20 is an impervious substrate for which access to MAD2 requires simultaneous docking on several sites of the catalytic complex. Our analysis indicates that the checkpoint catalyst is substrate assisted and promotes MCC assembly through spatially and temporally coordinated conformational changes in both MAD2 and CDC20. This may define a paradigm for other HORMA-controlled systems.
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Affiliation(s)
- Valentina Piano
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany.
| | - Amal Alex
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Patricia Stege
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Stefano Maffini
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Gerardo A Stoppiello
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Pim J Huis In 't Veld
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Ingrid R Vetter
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Andrea Musacchio
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany. .,Centre for Medical Biotechnology, Faculty of Biology, University Duisburg-Essen, 45141 Essen, Germany
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13
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Cunha-Silva S, Osswald M, Goemann J, Barbosa J, Santos LM, Resende P, Bange T, Ferrás C, Sunkel CE, Conde C. Mps1-mediated release of Mad1 from nuclear pores ensures the fidelity of chromosome segregation. J Cell Biol 2020; 219:133569. [PMID: 31913420 PMCID: PMC7054998 DOI: 10.1083/jcb.201906039] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 10/20/2019] [Accepted: 11/28/2019] [Indexed: 12/26/2022] Open
Abstract
The spindle assembly checkpoint (SAC) relies on the recruitment of Mad1-C-Mad2 to unattached kinetochores but also on its binding to Megator/Tpr at nuclear pore complexes (NPCs) during interphase. However, the molecular underpinnings controlling the spatiotemporal redistribution of Mad1-C-Mad2 as cells progress into mitosis remain elusive. Here, we show that activation of Mps1 during prophase triggers Mad1 release from NPCs and that this is required for kinetochore localization of Mad1-C-Mad2 and robust SAC signaling. We find that Mps1 phosphorylates Megator/Tpr to reduce its interaction with Mad1 in vitro and in Drosophila cells. Importantly, preventing Mad1 from binding to Megator/Tpr restores Mad1 accumulation at kinetochores, the fidelity of chromosome segregation, and genome stability in larval neuroblasts of mps1-null mutants. Our findings demonstrate that the subcellular localization of Mad1 is tightly coordinated with cell cycle progression by kinetochore-extrinsic activity of Mps1. This ensures that both NPCs in interphase and kinetochores in mitosis can generate anaphase inhibitors to efficiently preserve genomic stability.
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Affiliation(s)
- Sofia Cunha-Silva
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.,Programa Doutoral em Biologia Molecular e Celular (MCbiology), Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Mariana Osswald
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Jana Goemann
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - João Barbosa
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Luis M Santos
- Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Pedro Resende
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Tanja Bange
- Max-Planck-Institut für Molekulare Physiologie, Dortmund, Germany
| | - Cristina Ferrás
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Claudio E Sunkel
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.,Departamento de Biologia Molecular, Instituto de Ciências Biomédicas Abel Salazar, Porto, Portugal
| | - Carlos Conde
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
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14
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Libkind D, Peris D, Cubillos FA, Steenwyk JL, Opulente DA, Langdon QK, Rokas A, Hittinger CT. Into the wild: new yeast genomes from natural environments and new tools for their analysis. FEMS Yeast Res 2020; 20:foaa008. [PMID: 32009143 PMCID: PMC7067299 DOI: 10.1093/femsyr/foaa008] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Accepted: 01/31/2020] [Indexed: 12/16/2022] Open
Abstract
Genomic studies of yeasts from the wild have increased considerably in the past few years. This revolution has been fueled by advances in high-throughput sequencing technologies and a better understanding of yeast ecology and phylogeography, especially for biotechnologically important species. The present review aims to first introduce new bioinformatic tools available for the generation and analysis of yeast genomes. We also assess the accumulated genomic data of wild isolates of industrially relevant species, such as Saccharomyces spp., which provide unique opportunities to further investigate the domestication processes associated with the fermentation industry and opportunistic pathogenesis. The availability of genome sequences of other less conventional yeasts obtained from the wild has also increased substantially, including representatives of the phyla Ascomycota (e.g. Hanseniaspora) and Basidiomycota (e.g. Phaffia). Here, we review salient examples of both fundamental and applied research that demonstrate the importance of continuing to sequence and analyze genomes of wild yeasts.
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Affiliation(s)
- D Libkind
- Centro de Referencia en Levaduras y Tecnología Cervecera (CRELTEC), Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales (IPATEC) – CONICET/Universidad Nacional del Comahue, Quintral 1250 (8400), Bariloche., Argentina
| | - D Peris
- Department of Food Biotechnology, Institute of Agrochemistry and Food Technology-CSIC, Calle Catedrático Dr. D. Agustin Escardino Benlloch n°7, 46980 Paterna, Valencia, Spain
| | - F A Cubillos
- Millennium Institute for Integrative Biology (iBio). General del Canto 51 (7500574), Santiago
- Universidad de Santiago de Chile, Facultad de Química y Biología, Departamento de Biología. Alameda 3363 (9170002). Estación Central. Santiago, Chile
| | - J L Steenwyk
- Department of Biological Sciences, VU Station B#35-1634, Vanderbilt University, Nashville, TN 37235, USA
| | - D A Opulente
- Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Center for Genomic Science Innovation, University of Wisconsin-Madison, 1552 University Avenue, Madison, WI 53726-4084, USA
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, 1552 University Avenue, Madison, I 53726-4084, Madison, WI, USA
| | - Q K Langdon
- Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Center for Genomic Science Innovation, University of Wisconsin-Madison, 1552 University Avenue, Madison, WI 53726-4084, USA
| | - A Rokas
- Department of Biological Sciences, VU Station B#35-1634, Vanderbilt University, Nashville, TN 37235, USA
| | - C T Hittinger
- Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Center for Genomic Science Innovation, University of Wisconsin-Madison, 1552 University Avenue, Madison, WI 53726-4084, USA
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, 1552 University Avenue, Madison, I 53726-4084, Madison, WI, USA
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15
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Leontiou I, London N, May KM, Ma Y, Grzesiak L, Medina-Pritchard B, Amin P, Jeyaprakash AA, Biggins S, Hardwick KG. The Bub1-TPR Domain Interacts Directly with Mad3 to Generate Robust Spindle Checkpoint Arrest. Curr Biol 2019; 29:2407-2414.e7. [PMID: 31257143 PMCID: PMC6657678 DOI: 10.1016/j.cub.2019.06.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Revised: 01/30/2019] [Accepted: 06/04/2019] [Indexed: 12/14/2022]
Abstract
The spindle checkpoint monitors kinetochore-microtubule interactions and generates a “wait anaphase” delay when any defects are apparent [1, 2, 3]. This provides time for cells to correct chromosome attachment errors and ensure high-fidelity chromosome segregation. Checkpoint signals are generated at unattached chromosomes during mitosis. To activate the checkpoint, Mps1Mph1 kinase phosphorylates the kinetochore component KNL1Spc105/Spc7 on conserved MELT motifs to recruit Bub3-Bub1 complexes [4, 5, 6] via a direct Bub3 interaction with phospho-MELT motifs [7, 8]. Mps1Mph1 then phosphorylates Bub1, which strengthens its interaction with Mad1-Mad2 complexes to produce a signaling platform [9, 10]. The Bub1-Mad1 platform is thought to recruit Mad3, Cdc20, and Mad2 to produce the mitotic checkpoint complex (MCC), which is the diffusible wait anaphase signal [9, 11, 12]. The MCC binds and inhibits the mitotic E3 ubiquitin ligase, known as Cdc20-anaphase promoting complex/cyclosome (APC/C), and stabilizes securin and cyclin to delay anaphase onset [13, 14, 15, 16, 17]. Here we demonstrate, in both budding and fission yeast, that kinetochores and KNL1Spc105/Spc7 can be bypassed; simply inducing heterodimers of Mps1Mph1 kinase and Bub1 is sufficient to trigger metaphase arrest that is dependent on Mad1, Mad2, and Mad3. We use this to dissect the domains of Bub1 necessary for arrest, highlighting the need for Bub1-CD1, which binds Mad1 [9], and Bub1’s highly conserved N-terminal tetratricopeptide repeat (TPR) domain [18, 19]. We demonstrate that the Bub1 TPR domain is both necessary and sufficient to bind and recruit Mad3. We propose that this brings Mad3 into close proximity to Mad1-Mad2 and Mps1Mph1 kinase, enabling efficient generation of MCC complexes. Heterodimers of Mps1 and Bub1 generate robust spindle checkpoint arrest in yeasts This arrest is independent of kinetochores but requires Bub1-CD1 and the Bub1-TPR The Bub1-TPR is both necessary and sufficient for Mad3 interaction and recruitment Recombinant fission yeast Bub1-TPR and Mad3 form a stable complex
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Affiliation(s)
- Ioanna Leontiou
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Nitobe London
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Karen M May
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Yingrui Ma
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Lucile Grzesiak
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Bethan Medina-Pritchard
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Priya Amin
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - A Arockia Jeyaprakash
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Sue Biggins
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Kevin G Hardwick
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Max Born Crescent, Edinburgh EH9 3BF, UK.
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16
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Steenwyk JL, Opulente DA, Kominek J, Shen XX, Zhou X, Labella AL, Bradley NP, Eichman BF, Čadež N, Libkind D, DeVirgilio J, Hulfachor AB, Kurtzman CP, Hittinger CT, Rokas A. Extensive loss of cell-cycle and DNA repair genes in an ancient lineage of bipolar budding yeasts. PLoS Biol 2019; 17:e3000255. [PMID: 31112549 PMCID: PMC6528967 DOI: 10.1371/journal.pbio.3000255] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 04/18/2019] [Indexed: 02/06/2023] Open
Abstract
Cell-cycle checkpoints and DNA repair processes protect organisms from potentially lethal mutational damage. Compared to other budding yeasts in the subphylum Saccharomycotina, we noticed that a lineage in the genus Hanseniaspora exhibited very high evolutionary rates, low Guanine-Cytosine (GC) content, small genome sizes, and lower gene numbers. To better understand Hanseniaspora evolution, we analyzed 25 genomes, including 11 newly sequenced, representing 18/21 known species in the genus. Our phylogenomic analyses identify two Hanseniaspora lineages, a faster-evolving lineage (FEL), which began diversifying approximately 87 million years ago (mya), and a slower-evolving lineage (SEL), which began diversifying approximately 54 mya. Remarkably, both lineages lost genes associated with the cell cycle and genome integrity, but these losses were greater in the FEL. E.g., all species lost the cell-cycle regulator WHIskey 5 (WHI5), and the FEL lost components of the spindle checkpoint pathway (e.g., Mitotic Arrest-Deficient 1 [MAD1], Mitotic Arrest-Deficient 2 [MAD2]) and DNA-damage-checkpoint pathway (e.g., Mitosis Entry Checkpoint 3 [MEC3], RADiation sensitive 9 [RAD9]). Similarly, both lineages lost genes involved in DNA repair pathways, including the DNA glycosylase gene 3-MethylAdenine DNA Glycosylase 1 (MAG1), which is part of the base-excision repair pathway, and the DNA photolyase gene PHotoreactivation Repair deficient 1 (PHR1), which is involved in pyrimidine dimer repair. Strikingly, the FEL lost 33 additional genes, including polymerases (i.e., POLymerase 4 [POL4] and POL32) and telomere-associated genes (e.g., Repressor/activator site binding protein-Interacting Factor 1 [RIF1], Replication Factor A 3 [RFA3], Cell Division Cycle 13 [CDC13], Pbp1p Binding Protein [PBP2]). Echoing these losses, molecular evolutionary analyses reveal that, compared to the SEL, the FEL stem lineage underwent a burst of accelerated evolution, which resulted in greater mutational loads, homopolymer instabilities, and higher fractions of mutations associated with the common endogenously damaged base, 8-oxoguanine. We conclude that Hanseniaspora is an ancient lineage that has diversified and thrived, despite lacking many otherwise highly conserved cell-cycle and genome integrity genes and pathways, and may represent a novel, to our knowledge, system for studying cellular life without them.
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Affiliation(s)
- Jacob L Steenwyk
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Dana A Opulente
- Laboratory of Genetics, Genome Center of Wisconsin, DOE Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Wisconsin, United States of America
| | - Jacek Kominek
- Laboratory of Genetics, Genome Center of Wisconsin, DOE Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Wisconsin, United States of America
| | - Xing-Xing Shen
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Xiaofan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Abigail L Labella
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Noah P Bradley
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Brandt F Eichman
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Neža Čadež
- University of Ljubljana Biotechnical Faculty, Department of Food Science and Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Diego Libkind
- Laboratorio de Microbiología Aplicada, Biotecnología y Bioinformática, Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales, Universidad Nacional del Comahue-CONICET, San Carlos de Bariloche, Río Negro, Argentina
| | - Jeremy DeVirgilio
- Mycotoxin Prevention and Applied Microbiology Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, United States Department of Agriculture, Peoria, Illinois, United States of America
| | - Amanda Beth Hulfachor
- Laboratory of Genetics, Genome Center of Wisconsin, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Cletus P Kurtzman
- Mycotoxin Prevention and Applied Microbiology Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, United States Department of Agriculture, Peoria, Illinois, United States of America
| | - Chris Todd Hittinger
- Laboratory of Genetics, Genome Center of Wisconsin, DOE Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Wisconsin, United States of America
| | - Antonis Rokas
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
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17
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18
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Zhang G, Kruse T, Guasch Boldú C, Garvanska DH, Coscia F, Mann M, Barisic M, Nilsson J. Efficient mitotic checkpoint signaling depends on integrated activities of Bub1 and the RZZ complex. EMBO J 2019; 38:embj.2018100977. [PMID: 30782962 DOI: 10.15252/embj.2018100977] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/23/2019] [Accepted: 01/29/2019] [Indexed: 12/11/2022] Open
Abstract
Kinetochore localized Mad1 is essential for generating a "wait anaphase" signal during mitosis, hereby ensuring accurate chromosome segregation. Inconsistent models for the function and quantitative contribution of the two mammalian Mad1 kinetochore receptors: Bub1 and the Rod-Zw10-Zwilch (RZZ) complex exist. By combining genome editing and RNAi, we achieve penetrant removal of Bub1 and Rod in human cells, which reveals that efficient checkpoint signaling depends on the integrated activities of these proteins. Rod removal reduces the proximity of Bub1 and Mad1, and we can bypass the requirement for Rod by tethering Mad1 to kinetochores or increasing the strength of the Bub1-Mad1 interaction. We find that Bub1 has checkpoint functions independent of Mad1 localization that are supported by low levels of Bub1 suggesting a catalytic function. In conclusion, our results support an integrated model for the Mad1 receptors in which the primary role of RZZ is to localize Mad1 at kinetochores to generate the Mad1-Bub1 complex.
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Affiliation(s)
- Gang Zhang
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark .,Cancer Institute, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China.,Qingdao Cancer Institute, Qingdao, Shandong, China
| | - Thomas Kruse
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Claudia Guasch Boldú
- Cell Division Laboratory, Danish Cancer Society Research Center, Copenhagen, Denmark
| | - Dimitriya H Garvanska
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Fabian Coscia
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Matthias Mann
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Marin Barisic
- Cell Division Laboratory, Danish Cancer Society Research Center, Copenhagen, Denmark.,Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jakob Nilsson
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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19
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Cell-Size-Independent Spindle Checkpoint Failure Underlies Chromosome Segregation Error in Mouse Embryos. Curr Biol 2019; 29:865-873.e3. [PMID: 30773364 DOI: 10.1016/j.cub.2018.12.042] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 11/23/2018] [Accepted: 12/21/2018] [Indexed: 12/31/2022]
Abstract
Chromosome segregation errors during mammalian preimplantation development cause "mosaic" embryos comprising a mixture of euploid and aneuploid cells, which reduce the potential for a successful pregnancy [1-5], but why these errors are common is unknown. In most cells, chromosome segregation error is averted by the spindle assembly checkpoint (SAC), which prevents anaphase-promoting complex (APC/C) activation and anaphase onset until chromosomes are aligned with kinetochores attached to spindle microtubules [6, 7], but little is known about the SAC's role in the early mammalian embryo. In C. elegans, the SAC is weak in early embryos, and it strengthens during early embryogenesis as a result of progressively lessening cell size [8, 9]. Here, using live imaging, micromanipulation, gene knockdown, and pharmacological approaches, we show that this is not the case in mammalian embryos. Misaligned chromosomes in the early mouse embryo can recruit SAC components to mount a checkpoint signal, but this signal fails to prevent anaphase onset, leading to high levels of chromosome segregation error. We find that failure of the SAC to prolong mitosis is not attributable to cell size. We show that mild chemical inhibition of APC/C can extend mitosis, thereby allowing more time for correct chromosome alignment and reducing segregation errors. SAC-APC/C disconnect thus presents a mechanistic explanation for frequent chromosome segregation errors in early mammalian embryos. Moreover, our data provide proof of principle that modulation of the SAC-APC/C axis can increase the likelihood of error-free chromosome segregation in cultured mammalian embryos.
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20
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Yang Y, Robertson JA, Guo Z, Martinez J, Coghlan C, Heath LS. MCAT: Motif Combining and Association Tool. J Comput Biol 2019; 26:1-15. [DOI: 10.1089/cmb.2018.0113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Yanshen Yang
- Department of Computer Science, Virginia Tech, Blacksburg, Virginia
| | | | - Zhen Guo
- Department of Computer Science, Virginia Tech, Blacksburg, Virginia
| | - Jake Martinez
- Department of Computer Science, Virginia Tech, Blacksburg, Virginia
| | - Christy Coghlan
- Department of Computer Science, Virginia Tech, Blacksburg, Virginia
| | - Lenwood S. Heath
- Department of Computer Science, Virginia Tech, Blacksburg, Virginia
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21
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Zhang G, Nilsson J. The closed form of Mad2 is bound to Mad1 and Cdc20 at unattached kinetochores. Cell Cycle 2018; 17:1087-1091. [PMID: 29895228 DOI: 10.1080/15384101.2018.1480209] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
Abstract
The spindle assembly checkpoint (SAC) ensures accurate chromosome segregation by delaying anaphase onset in response to unattached kinetochores. Anaphase is delayed by the generation of the mitotic checkpoint complex (MCC) composed of the checkpoint proteins Mad2 and BubR1/Bub3 bound to the protein Cdc20. Current models assume that MCC production is catalyzed at unattached kinetochores and that the Mad1/Mad2 complex is instrumental in the conversion of Mad2 from an open form (O-Mad2) to a closed form (C-Mad2) that can bind to Cdc20. Importantly the levels of Mad2 at kinetochores correlate with SAC activity but whether C-Mad2 at kinetochores exclusively represents its complex with Mad1 is not fully established. Here we use a recently established C-Mad2 specific monoclonal antibody to show that Cdc20 and C-Mad2 levels correlate at kinetochores and that depletion of Cdc20 reduces Mad2 but not Mad1 kinetochore levels. Importantly reintroducing wild type Cdc20 but not Cdc20 R132A, a mutant form that cannot bind Mad2, restores Mad2 levels. In agreement with this live cell imaging of fluorescent tagged Mad2 reveals that Cdc20 depletion strongly reduces Mad2 localization to kinetochores. These results support the presence of Mad2-Cdc20 complexes at kinetochores in agreement with current models of the SAC but also argue that Mad2 levels at kinetochores cannot be used as a direct readout of Mad1 levels.
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Affiliation(s)
- Gang Zhang
- a The Novo Nordisk Foundation Center for Protein Research, Faculty of health and medical sciences , University of Copenhagen , Copenhagen , Denmark.,b Cancer Institute , The Affiliated Hospital of Qingdao University , Qingdao , China.,c Qingdao Cancer Institute , Qingdao , China
| | - Jakob Nilsson
- a The Novo Nordisk Foundation Center for Protein Research, Faculty of health and medical sciences , University of Copenhagen , Copenhagen , Denmark
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22
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Luo Y, Ahmad E, Liu ST. MAD1: Kinetochore Receptors and Catalytic Mechanisms. Front Cell Dev Biol 2018; 6:51. [PMID: 29868582 PMCID: PMC5949338 DOI: 10.3389/fcell.2018.00051] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 04/18/2018] [Indexed: 12/22/2022] Open
Abstract
The mitotic checkpoint monitors kinetochore-microtubule attachment, delays anaphase onset and prevents aneuploidy when unattached or tensionless kinetochores are present in cells. Mitotic arrest deficiency 1 (MAD1) is one of the evolutionarily conserved core mitotic checkpoint proteins. MAD1 forms a cell cycle independent complex with MAD2 through its MAD2 interaction motif (MIM) in the middle region. Such a complex is enriched at unattached kinetochores and functions as an unusual catalyst to promote conformational change of additional MAD2 molecules, constituting a crucial signal amplifying mechanism for the mitotic checkpoint. Only MAD2 in its active conformation can be assembled with BUBR1 and CDC20 to form the Mitotic Checkpoint Complex (MCC), which is a potent inhibitor of anaphase onset. Recent research has shed light on how MAD1 is recruited to unattached kinetochores, and how it carries out its catalytic activity. Here we review these advances and discuss their implications for future research.
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Affiliation(s)
- Yibo Luo
- Department of Biological Sciences, University of Toledo, Toledo, OH, United States
| | - Ejaz Ahmad
- Department of Biological Sciences, University of Toledo, Toledo, OH, United States
| | - Song-Tao Liu
- Department of Biological Sciences, University of Toledo, Toledo, OH, United States
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23
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Meadows JC, Lancaster TC, Buttrick GJ, Sochaj AM, Messin LJ, Del Mar Mora-Santos M, Hardwick KG, Millar JBA. Identification of a Sgo2-Dependent but Mad2-Independent Pathway Controlling Anaphase Onset in Fission Yeast. Cell Rep 2017; 18:1422-1433. [PMID: 28178520 PMCID: PMC5316559 DOI: 10.1016/j.celrep.2017.01.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 12/08/2016] [Accepted: 01/15/2017] [Indexed: 10/28/2022] Open
Abstract
The onset of anaphase is triggered by activation of the anaphase-promoting complex/cyclosome (APC/C) following silencing of the spindle assembly checkpoint (SAC). APC/C triggers ubiquitination of Securin and Cyclin B, which leads to loss of sister chromatid cohesion and inactivation of Cyclin B/Cdk1, respectively. This promotes relocalization of Aurora B kinase and other components of the chromosome passenger complex (CPC) from centromeres to the spindle midzone. In fission yeast, this is mediated by Clp1 phosphatase-dependent interaction of CPC with Klp9/MKLP2 (kinesin-6). When this interaction is disrupted, kinetochores bi-orient normally, but APC/C activation is delayed via a mechanism that requires Sgo2 and some (Bub1, Mph1/Mps1, and Mad3), but not all (Mad1 and Mad2), components of the SAC and the first, but not second, lysine, glutamic acid, glutamine (KEN) box in Mad3. These data indicate that interaction of CPC with Klp9 terminates a Sgo2-dependent, but Mad2-independent, APC/C-inhibitory pathway that is distinct from the canonical SAC.
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Affiliation(s)
- John C Meadows
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK; Institute of Advanced Study, University of Warwick, Coventry CV4 7AL, UK
| | - Theresa C Lancaster
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Graham J Buttrick
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Alicja M Sochaj
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK
| | - Liam J Messin
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Maria Del Mar Mora-Santos
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Kevin G Hardwick
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK
| | - Jonathan B A Millar
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK.
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24
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Ji W, Luo Y, Ahmad E, Liu ST. Direct interactions of mitotic arrest deficient 1 (MAD1) domains with each other and MAD2 conformers are required for mitotic checkpoint signaling. J Biol Chem 2017; 293:484-496. [PMID: 29162720 DOI: 10.1074/jbc.ra117.000555] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 11/15/2017] [Indexed: 11/06/2022] Open
Abstract
As a sensitive signaling system, the mitotic checkpoint ensures faithful chromosome segregation by delaying anaphase onset even when a single kinetochore is unattached to mitotic spindle microtubules. The key signal amplification reaction for the checkpoint is the conformational conversion of "open" mitotic arrest deficient 2 (O-MAD2) into "closed" MAD2 (C-MAD2). The reaction has been suggested to be catalyzed by an unusual catalyst, a MAD1:C-MAD2 tetramer, but how the catalysis is executed and regulated remains elusive. Here, we report that in addition to the well-characterized middle region of MAD1 containing the MAD2-interaction motif (MIM), both N- and C-terminal domains (NTD and CTD) of MAD1 also contribute to mitotic checkpoint signaling. Unlike the MIM, which stably associated only with C-MAD2, the NTD and CTD in MAD1 surprisingly bound both O- and C-MAD2, suggesting that these two domains interact with both substrates and products of the O-to-C conversion. MAD1NTD and MAD1CTD also interacted with each other and with the MPS1 protein kinase, which phosphorylated both NTD and CTD. This phosphorylation decreased the NTD:CTD interaction and also CTD's interaction with MPS1. Of note, mutating the phosphorylation sites in the MAD1CTD, including Thr-716, compromised MAD2 binding and the checkpoint responses. We further noted that Ser-610 and Tyr-634 also contribute to the mitotic checkpoint signaling. Our results have uncovered that the MAD1NTD and MAD1CTD directly interact with each other and with MAD2 conformers and are regulated by MPS1 kinase, providing critical insights into mitotic checkpoint signaling.
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Affiliation(s)
- Wenbin Ji
- From the Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Yibo Luo
- From the Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Ejaz Ahmad
- From the Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Song-Tao Liu
- From the Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
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25
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An Attachment-Independent Biochemical Timer of the Spindle Assembly Checkpoint. Mol Cell 2017; 68:715-730.e5. [DOI: 10.1016/j.molcel.2017.10.011] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 08/24/2017] [Accepted: 10/11/2017] [Indexed: 11/16/2022]
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26
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Overlack K, Bange T, Weissmann F, Faesen AC, Maffini S, Primorac I, Müller F, Peters JM, Musacchio A. BubR1 Promotes Bub3-Dependent APC/C Inhibition during Spindle Assembly Checkpoint Signaling. Curr Biol 2017; 27:2915-2927.e7. [PMID: 28943088 PMCID: PMC5640511 DOI: 10.1016/j.cub.2017.08.033] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/16/2017] [Accepted: 08/15/2017] [Indexed: 12/25/2022]
Abstract
The spindle assembly checkpoint (SAC) prevents premature sister chromatid separation during mitosis. Phosphorylation of unattached kinetochores by the Mps1 kinase promotes recruitment of SAC machinery that catalyzes assembly of the SAC effector mitotic checkpoint complex (MCC). The SAC protein Bub3 is a phospho-amino acid adaptor that forms structurally related stable complexes with functionally distinct paralogs named Bub1 and BubR1. A short motif (“loop”) of Bub1, but not the equivalent loop of BubR1, enhances binding of Bub3 to kinetochore phospho-targets. Here, we asked whether the BubR1 loop directs Bub3 to different phospho-targets. The BubR1 loop is essential for SAC function and cannot be removed or replaced with the Bub1 loop. BubR1 loop mutants bind Bub3 and are normally incorporated in MCC in vitro but have reduced ability to inhibit the MCC target anaphase-promoting complex (APC/C), suggesting that BubR1:Bub3 recognition and inhibition of APC/C requires phosphorylation. Thus, small sequence differences in Bub1 and BubR1 direct Bub3 to different phosphorylated targets in the SAC signaling cascade. The molecular basis of kinetochore recruitment of Bub1 and BubR1 is dissected Bub1 and BubR1 modulate the ability of Bub3 to recognize phosphorylated targets A newly identified BubR1 motif targets Bub3 to the anaphase-promoting complex The newly identified motif of BubR1 is required for checkpoint signaling
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Affiliation(s)
- Katharina Overlack
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Tanja Bange
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Florian Weissmann
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Alex C Faesen
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Stefano Maffini
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Ivana Primorac
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Franziska Müller
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Andrea Musacchio
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany; Centre for Medical Biotechnology, Faculty of Biology, University Duisburg-Essen, Universitätsstrasse, 45141 Essen, Germany.
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27
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Lane SIR, Morgan SL, Wu T, Collins JK, Merriman JA, ElInati E, Turner JM, Jones KT. DNA damage induces a kinetochore-based ATM/ATR-independent SAC arrest unique to the first meiotic division in mouse oocytes. Development 2017; 144:3475-3486. [PMID: 28851706 PMCID: PMC5665484 DOI: 10.1242/dev.153965] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 08/18/2017] [Indexed: 12/31/2022]
Abstract
Mouse oocytes carrying DNA damage arrest in meiosis I, thereby preventing creation of embryos with deleterious mutations. The arrest is dependent on activation of the spindle assembly checkpoint, which results in anaphase-promoting complex (APC) inhibition. However, little is understood about how this checkpoint is engaged following DNA damage. Here, we find that within minutes of DNA damage checkpoint proteins are assembled at the kinetochore, not at damage sites along chromosome arms, such that the APC is fully inhibited within 30 min. Despite this robust response, there is no measurable loss in k-fibres, or tension across the bivalent. Through pharmacological inhibition we observed that the response is dependent on Mps1 kinase, aurora kinase and Haspin. Using oocyte-specific knockouts we find the response does not require the DNA damage response kinases ATM or ATR. Furthermore, checkpoint activation does not occur in response to DNA damage in fully mature eggs during meiosis II, despite the divisions being separated by just a few hours. Therefore, mouse oocytes have a unique ability to sense DNA damage rapidly by activating the checkpoint at their kinetochores.
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Affiliation(s)
- Simon I R Lane
- Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Stephanie L Morgan
- Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Tianyu Wu
- Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Josie K Collins
- Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Julie A Merriman
- Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Elias ElInati
- Sex Chromosome Biology Laboratory, The Francis Crick Institute, London, NW1 1AT, UK
| | - James M Turner
- Sex Chromosome Biology Laboratory, The Francis Crick Institute, London, NW1 1AT, UK
| | - Keith T Jones
- Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, SO17 1BJ, UK
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28
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Bub1 positions Mad1 close to KNL1 MELT repeats to promote checkpoint signalling. Nat Commun 2017; 8:15822. [PMID: 28604727 PMCID: PMC5472792 DOI: 10.1038/ncomms15822] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 05/03/2017] [Indexed: 12/21/2022] Open
Abstract
Proper segregation of chromosomes depends on a functional spindle assembly checkpoint (SAC) and requires kinetochore localization of the Bub1 and Mad1/Mad2 checkpoint proteins. Several aspects of Mad1/Mad2 kinetochore recruitment in human cells are unclear and in particular the underlying direct interactions. Here we show that conserved domain 1 (CD1) in human Bub1 binds directly to Mad1 and a phosphorylation site exists in CD1 that stimulates Mad1 binding and SAC signalling. Importantly, fusion of minimal kinetochore-targeting Bub1 fragments to Mad1 bypasses the need for CD1, revealing that the main function of Bub1 is to position Mad1 close to KNL1 MELT repeats. Furthermore, we identify residues in Mad1 that are critical for Mad1 functionality, but not Bub1 binding, arguing for a direct role of Mad1 in the checkpoint. This work dissects functionally relevant molecular interactions required for spindle assembly checkpoint signalling at kinetochores in human cells. The spindle assembly checkpoint ensures correct chromosome segregation and relies on kinetochore localization of the Bub1 and Mad1/Mad2 checkpoint proteins. Here the authors show that main function of Bub1 is to position Mad1 close to KNL1 MELT repeats in human cells.
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29
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Abstract
The kinase Mps1, long known to be the 'boss' in mitotic checkpoint signaling, phosphorylates multiple proteins in the checkpoint signaling cascade.
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Affiliation(s)
| | - Silke Hauf
- Department of Biological Sciences, Virginia Tech, Blacksburg, United States.,Biocomplexity Institute of Virginia Tech, Blacksburg, United States
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30
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Ji Z, Gao H, Jia L, Li B, Yu H. A sequential multi-target Mps1 phosphorylation cascade promotes spindle checkpoint signaling. eLife 2017; 6. [PMID: 28072388 PMCID: PMC5268738 DOI: 10.7554/elife.22513] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 01/09/2017] [Indexed: 12/18/2022] Open
Abstract
The master spindle checkpoint kinase Mps1 senses kinetochore-microtubule attachment and promotes checkpoint signaling to ensure accurate chromosome segregation. The kinetochore scaffold Knl1, when phosphorylated by Mps1, recruits checkpoint complexes Bub1–Bub3 and BubR1–Bub3 to unattached kinetochores. Active checkpoint signaling ultimately enhances the assembly of the mitotic checkpoint complex (MCC) consisting of BubR1–Bub3, Mad2, and Cdc20, which inhibits the anaphase-promoting complex or cyclosome bound to Cdc20 (APC/CCdc20) to delay anaphase onset. Using in vitro reconstitution, we show that Mps1 promotes APC/C inhibition by MCC components through phosphorylating Bub1 and Mad1. Phosphorylated Bub1 binds to Mad1–Mad2. Phosphorylated Mad1 directly interacts with Cdc20. Mutations of Mps1 phosphorylation sites in Bub1 or Mad1 abrogate the spindle checkpoint in human cells. Therefore, Mps1 promotes checkpoint activation through sequentially phosphorylating Knl1, Bub1, and Mad1. This sequential multi-target phosphorylation cascade makes the checkpoint highly responsive to Mps1 and to kinetochore-microtubule attachment. DOI:http://dx.doi.org/10.7554/eLife.22513.001
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Affiliation(s)
- Zhejian Ji
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Haishan Gao
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Luying Jia
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Bing Li
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Hongtao Yu
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
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31
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Generation of a Spindle Checkpoint Arrest from Synthetic Signaling Assemblies. Curr Biol 2016; 27:137-143. [PMID: 28017606 PMCID: PMC5226922 DOI: 10.1016/j.cub.2016.11.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 10/14/2016] [Accepted: 11/03/2016] [Indexed: 11/24/2022]
Abstract
The spindle checkpoint acts as a mitotic surveillance system, monitoring interactions between kinetochores and spindle microtubules and ensuring high-fidelity chromosome segregation [1, 2, 3]. The checkpoint is activated by unattached kinetochores, and Mps1 kinase phosphorylates KNL1 on conserved MELT motifs to generate a binding site for the Bub3-Bub1 complex [4, 5, 6, 7]. This leads to dynamic kinetochore recruitment of Mad proteins [8, 9], a conformational change in Mad2 [10, 11, 12], and formation of the mitotic checkpoint complex (MCC: Cdc20-Mad3-Mad2 [13, 14, 15]). MCC formation inhibits the anaphase-promoting complex/cyclosome (Cdc20-APC/C), thereby preventing the proteolytic destruction of securin and cyclin and delaying anaphase onset. What happens at kinetochores after Mps1-dependent Bub3-Bub1 recruitment remains mechanistically unclear, and it is not known whether kinetochore proteins other than KNL1 have significant roles to play in checkpoint signaling and MCC generation. Here, we take a reductionist approach, avoiding the complexities of kinetochores, and demonstrate that co-recruitment of KNL1Spc7 and Mps1Mph1 is sufficient to generate a robust checkpoint signal and prolonged mitotic arrest. We demonstrate that a Mad1-Bub1 complex is formed during synthetic checkpoint signaling. Analysis of bub3Δ mutants demonstrates that Bub3 acts to suppress premature checkpoint signaling. This synthetic system will enable detailed, mechanistic dissection of MCC generation and checkpoint silencing. After analyzing several mutants that affect localization of checkpoint complexes, we conclude that spindle checkpoint arrest can be independent of their kinetochore, spindle pole, and nuclear envelope localization. Synthetic signaling scaffolds generate a spindle checkpoint arrest The combination of KNL1Spc7 and Mps1Mph1 kinase generates a robust arrest Kinetochore, spindle, and nuclear envelope enrichment of the scaffold is not required Bub3 acts to inhibit premature checkpoint activation
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32
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Bub3-Bub1 Binding to Spc7/KNL1 Toggles the Spindle Checkpoint Switch by Licensing the Interaction of Bub1 with Mad1-Mad2. Curr Biol 2016; 26:2642-2650. [PMID: 27618268 DOI: 10.1016/j.cub.2016.07.040] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 06/22/2016] [Accepted: 07/15/2016] [Indexed: 01/06/2023]
Abstract
The spindle assembly checkpoint (SAC) ensures that sister chromatids do not separate until all chromosomes are attached to spindle microtubules and bi-oriented. Spindle checkpoint proteins, including Mad1, Mad2, Mad3 (BubR1), Bub1, Bub3, and Mph1 (Mps1), are recruited to unattached and/or tensionless kinetochores. SAC activation catalyzes the conversion of soluble Mad2 (O-Mad2) into a form (C-Mad2) that binds Cdc20, BubR1, and Bub3 to form the mitotic checkpoint complex (MCC), a potent inhibitor of the anaphase-promoting complex (APC/C). SAC silencing de-represses Cdc20-APC/C activity allowing poly-ubiquitination of Securin and Cyclin B, leading to the dissolution of sister chromatids and anaphase onset [1]. Understanding how microtubule interaction at kinetochores influences the timing of anaphase requires an understanding of how spindle checkpoint protein interaction with the kinetochore influences spindle checkpoint signaling. We, and others, recently showed that Mph1 (Mps1) phosphorylates multiple conserved MELT motifs in the Spc7 (Spc105/KNL1) protein to recruit Bub1, Bub3, and Mad3 (BubR1) to kinetochores [2-4]. In budding yeast, Mps1 phosphorylation of a central non-catalytic region of Bub1 promotes its association with the Mad1-Mad2 complex, although this association has not yet been detected in other organisms [5]. Here we report that multisite binding of Bub3 to the Spc7 MELT array toggles the spindle checkpoint switch by permitting Mph1 (Mps1)-dependent interaction of Bub1 with Mad1-Mad2.
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33
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Abstract
The spindle assembly checkpoint (SAC) is a key mechanism to regulate the timing of mitosis and ensure that chromosomes are correctly segregated to daughter cells. The recruitment of the Mad1 and Mad2 proteins to the kinetochore is normally necessary for SAC activation. This recruitment is coordinated by the SAC kinase Mps1, which phosphorylates residues at the kinetochore to facilitate binding of Bub1, Bub3, Mad1, and Mad2. There is evidence that the essential function of Mps1 is to direct recruitment of Mad1/2. To test this model, we have systematically recruited Mad1, Mad2, and Mps1 to most proteins in the yeast kinetochore, and find that, while Mps1 is sufficient for checkpoint activation, recruitment of either Mad1 or Mad2 is not. These data indicate an important role for Mps1 phosphorylation in SAC activation, beyond the direct recruitment of Mad1 and Mad2.
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34
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Abstract
The spindle assembly checkpoint is a safeguard mechanism that coordinates cell-cycle progression during mitosis with the state of chromosome attachment to the mitotic spindle. The checkpoint prevents mitotic cells from exiting mitosis in the presence of unattached or improperly attached chromosomes, thus avoiding whole-chromosome gains or losses and their detrimental effects on cell physiology. Here, I review a considerable body of recent progress in the elucidation of the molecular mechanisms underlying checkpoint signaling, and identify a number of unresolved questions.
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Affiliation(s)
- Andrea Musacchio
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany; Centre for Medical Biotechnology, Faculty of Biology, University Duisburg-Essen, Essen, Germany.
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35
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Silió V, McAinsh A, Millar J. KNL1-Bubs and RZZ Provide Two Separable Pathways for Checkpoint Activation at Human Kinetochores. Dev Cell 2015; 35:600-613. [DOI: 10.1016/j.devcel.2015.11.012] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 09/11/2015] [Accepted: 11/10/2015] [Indexed: 01/17/2023]
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36
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Nelson CR, Hwang T, Chen PH, Bhalla N. TRIP13PCH-2 promotes Mad2 localization to unattached kinetochores in the spindle checkpoint response. J Cell Biol 2015; 211:503-16. [PMID: 26527744 PMCID: PMC4639874 DOI: 10.1083/jcb.201505114] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 09/24/2015] [Indexed: 12/19/2022] Open
Abstract
The ability of the conserved ATPase TRIP13PCH-2 to disassemble a Mad2-containing complex is critical to promote the spindle checkpoint response by contributing to the robust localization of Mad2 to unattached kinetochores. The spindle checkpoint acts during cell division to prevent aneuploidy, a hallmark of cancer. During checkpoint activation, Mad1 recruits Mad2 to kinetochores to generate a signal that delays anaphase onset. Yet, whether additional factors contribute to Mad2’s kinetochore localization remains unclear. Here, we report that the conserved AAA+ ATPase TRIP13PCH-2 localizes to unattached kinetochores and is required for spindle checkpoint activation in Caenorhabditis elegans. pch-2 mutants effectively localized Mad1 to unattached kinetochores, but Mad2 recruitment was significantly reduced. Furthermore, we show that the C. elegans orthologue of the Mad2 inhibitor p31(comet)CMT-1 interacts with TRIP13PCH-2 and is required for its localization to unattached kinetochores. These factors also genetically interact, as loss of p31(comet)CMT-1 partially suppressed the requirement for TRIP13PCH-2 in Mad2 localization and spindle checkpoint signaling. These data support a model in which the ability of TRIP13PCH-2 to disassemble a p31(comet)/Mad2 complex, which has been well characterized in the context of checkpoint silencing, is also critical for spindle checkpoint activation.
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Affiliation(s)
- Christian R Nelson
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Tom Hwang
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Pin-Hsi Chen
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Needhi Bhalla
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
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37
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Zhang G, Lischetti T, Hayward DG, Nilsson J. Distinct domains in Bub1 localize RZZ and BubR1 to kinetochores to regulate the checkpoint. Nat Commun 2015; 6:7162. [PMID: 26031201 PMCID: PMC4458899 DOI: 10.1038/ncomms8162] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 04/10/2015] [Indexed: 12/29/2022] Open
Abstract
The spindle assembly checkpoint (SAC) ensures proper chromosome segregation by delaying anaphase onset in response to unattached kinetochores. Checkpoint signalling requires the kinetochore localization of the Mad1–Mad2 complex that in more complex eukaryotes depends on the Rod–Zwilch–ZW10 (RZZ) complex. The kinetochore protein Zwint has been proposed to be the kinetochore receptor for RZZ, but here we show that Bub1 and not Zwint is required for RZZ recruitment. We find that the middle region of Bub1 encompassing a domain essential for SAC signalling contributes to RZZ localization. In addition, we show that a distinct region in Bub1 mediates kinetochore localization of BubR1 through direct binding, but surprisingly removal of this region increases checkpoint strength. Our work thus uncovers how Bub1 coordinates checkpoint signalling by distinct domains for RZZ and BubR1 recruitment and suggests that Bub1 localizes antagonistic checkpoint activities. The spindle assembly checkpoint (SAC) depends on the recruitment of specific protein complexes to the kinetochore. Here Zhang et al. show that Bub1 recruits the RZZ complex and BubR1 to the kinetochore, and loss of the BubR1 binding sequence enhances checkpoint activity suggesting both SAC activating and silencing roles.
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Affiliation(s)
- Gang Zhang
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Tiziana Lischetti
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Daniel G Hayward
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
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38
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Lischetti T, Nilsson J. Regulation of mitotic progression by the spindle assembly checkpoint. Mol Cell Oncol 2015; 2:e970484. [PMID: 27308407 PMCID: PMC4905242 DOI: 10.4161/23723548.2014.970484] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 09/10/2014] [Accepted: 09/11/2014] [Indexed: 11/25/2022]
Abstract
Equal segregation of sister chromatids during mitosis requires that pairs of kinetochores establish proper attachment to microtubules emanating from opposite poles of the mitotic spindle. The spindle assembly checkpoint (SAC) protects against errors in segregation by delaying sister separation in response to improper kinetochore–microtubule interactions, and certain checkpoint proteins help to establish proper attachments. Anaphase entry is inhibited by the checkpoint through assembly of the mitotic checkpoint complex (MCC) composed of the 2 checkpoint proteins, Mad2 and BubR1, bound to Cdc20. The outer kinetochore acts as a catalyst for MCC production through the recruitment and proper positioning of checkpoint proteins and recently there has been remarkable progress in understanding how this is achieved. Here, we highlight recent advances in our understanding of kinetochore–checkpoint protein interactions and inhibition of the anaphase promoting complex by the MCC.
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Affiliation(s)
- Tiziana Lischetti
- The Novo Nordisk Foundation Center for Protein Research; Faculty of Health and Medical Sciences, University of Copenhagen ; Copenhagen, Denmark
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research; Faculty of Health and Medical Sciences, University of Copenhagen ; Copenhagen, Denmark
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London N, Biggins S. Signalling dynamics in the spindle checkpoint response. Nat Rev Mol Cell Biol 2014; 15:736-47. [PMID: 25303117 DOI: 10.1038/nrm3888] [Citation(s) in RCA: 227] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The spindle checkpoint ensures proper chromosome segregation during cell division. Unravelling checkpoint signalling has been a long-standing challenge owing to the complexity of the structures and forces that regulate chromosome segregation. New reports have now substantially advanced our understanding of checkpoint signalling mechanisms at the kinetochore, the structure that connects microtubules and chromatin. In contrast to the traditional view of a binary checkpoint response - either completely on or off - new findings indicate that the checkpoint response strength is variable. This revised perspective provides insight into how checkpoint bypass can lead to aneuploidy and informs strategies to exploit these errors for cancer treatments.
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Affiliation(s)
- Nitobe London
- 1] Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N., PO Box 19024, Seattle, Washington 98109, USA. [2] Molecular and Cellular Biology Program, University of Washington/Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Sue Biggins
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N., PO Box 19024, Seattle, Washington 98109, USA
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Bimodal activation of BubR1 by Bub3 sustains mitotic checkpoint signaling. Proc Natl Acad Sci U S A 2014; 111:E4185-93. [PMID: 25246557 DOI: 10.1073/pnas.1416277111] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The mitotic checkpoint (also known as the spindle assembly checkpoint) prevents premature anaphase onset through generation of an inhibitor of the E3 ubiquitin ligase APC/C, whose ubiquitination of cyclin B and securin targets them for degradation. Combining in vitro reconstitution and cell-based assays, we now identify dual mechanisms through which Bub3 promotes mitotic checkpoint signaling. Bub3 enhances signaling at unattached kinetochores not only by facilitating binding of BubR1 but also by enhancing Cdc20 recruitment to kinetochores mediated by BubR1's internal Cdc20 binding site. Downstream of kinetochore-produced complexes, Bub3 promotes binding of BubR1's conserved, amino terminal Cdc20 binding domain to a site in Cdc20 that becomes exposed by initial Mad2 binding. This latter Bub3-stimulated event generates the final mitotic checkpoint complex of Bub3-BubR1-Cdc20 that selectively inhibits ubiquitination of securin and cyclin B by APC/C(Cdc20). Thus, Bub3 promotes two distinct BubR1-Cdc20 interactions, involving each of the two Cdc20 binding sites of BubR1 and acting at unattached kinetochores or cytoplasmically, respectively, to facilitate production of the mitotic checkpoint inhibitor.
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Sacristan C, Kops GJPL. Joined at the hip: kinetochores, microtubules, and spindle assembly checkpoint signaling. Trends Cell Biol 2014; 25:21-8. [PMID: 25220181 DOI: 10.1016/j.tcb.2014.08.006] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 01/01/2023]
Abstract
Error-free chromosome segregation relies on stable connections between kinetochores and spindle microtubules. The spindle assembly checkpoint (SAC) monitors such connections and relays their absence to the cell cycle machinery to delay cell division. The molecular network at kinetochores that is responsible for microtubule binding is integrated with the core components of the SAC signaling system. Molecular-mechanistic understanding of how the SAC is coupled to the kinetochore-microtubule interface has advanced significantly in recent years. The latest insights not only provide a striking view of the dynamics and regulation of SAC signaling events at the outer kinetochore but also create a framework for understanding how that signaling may be terminated when kinetochores and microtubules connect.
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Affiliation(s)
- Carlos Sacristan
- Molecular Cancer Research, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - Geert J P L Kops
- Molecular Cancer Research, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands; Center for Molecular Medicine, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands; Cancer Genomics Netherlands, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands.
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Rajanala K, Sarkar A, Jhingan GD, Priyadarshini R, Jalan M, Sengupta S, Nandicoori VK. Phosphorylation of nucleoporin Tpr governs its differential localization and is required for its mitotic function. J Cell Sci 2014; 127:3505-20. [PMID: 24938596 DOI: 10.1242/jcs.149112] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
A major constituent of the nuclear basket region of the nuclear pore complex (NPC), nucleoporin Tpr, plays roles in regulating multiple important processes. We have previously established that Tpr is phosphorylated in both a MAP-kinase-dependent and MAP-kinase-independent manner, and that Tpr acts as both a substrate and as a scaffold for ERK2 (also known as MAPK1). Here, we report the identification of S2059 and S2094 as the major novel ERK-independent phosphorylation sites and T1677, S2020, S2023 and S2034 as additional ERK-independent phosphorylation sites found in the Tpr protein in vivo. Our results suggest that protein kinase A phosphorylates the S2094 residue and that the site is hyperphosphorylated during mitosis. Furthermore, we find that Tpr is phosphorylated at the S2059 residue by CDK1 and the phosphorylated form distinctly localizes with chromatin during telophase. Abrogation of S2059 phosphorylation abolishes the interaction of Tpr with Mad1, thus compromising the localization of both Mad1 and Mad2 proteins, resulting in cell cycle defects. The identification of novel phosphorylation sites on Tpr and the observations presented in this study allow better understanding of Tpr functions.
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Affiliation(s)
- Kalpana Rajanala
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Anshuk Sarkar
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Gagan Deep Jhingan
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Raina Priyadarshini
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Manisha Jalan
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Sagar Sengupta
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
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Abstract
The faithful segregation of chromosomes into daughter cells is essential for cellular and organismal viability. Errors in this process cause aneuploidy, a hallmark of cancer and several congenital diseases. For proper separation, chromosomes attach to microtubules of the mitotic spindle via their kinetochores, large protein structures assembled on centromeric chromatin. Kinetochores are also crucial for a cell cycle feedback mechanism known as the spindle assembly checkpoint (SAC). The SAC forces cells to remain in mitosis until all chromosomes are properly attached to microtubules. At the beginning of mitosis, the SAC proteins--Mad1, Mad2, Bub1, Bub3, BubR1, Mps1, and Cdc20--are recruited to kinetochores in a hierarchical and interdependent fashion (Fig 1A). There they monitor, in ways that are not fully clarified, the formation of kinetochore-microtubule attachments. Two studies recently published in EMBO reports by the groups of Silke Hauf and Jakob Nilsson, and a recent study by London and Biggins in Genes & Development, shed new light on the conserved SAC protein Mad1.
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Affiliation(s)
- Katharina Overlack
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
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Kruse T, Larsen MSY, Sedgwick GG, Sigurdsson JO, Streicher W, Olsen JV, Nilsson J. A direct role of Mad1 in the spindle assembly checkpoint beyond Mad2 kinetochore recruitment. EMBO Rep 2014; 15:282-90. [PMID: 24477933 DOI: 10.1002/embr.201338101] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The spindle assembly checkpoint (SAC) ensures accurate chromosome segregation by delaying entry into anaphase until all sister chromatids have become bi-oriented. A key component of the SAC is the Mad2 protein, which can adopt either an inactive open (O-Mad2) or active closed (C-Mad2) conformation. The conversion of O-Mad2 into C-Mad2 at unattached kinetochores is thought to be a key step in activating the SAC. The "template model" proposes that this is achieved by the recruitment of soluble O-Mad2 to C-Mad2 bound at kinetochores through its interaction with Mad1. Whether Mad1 has additional roles in the SAC beyond recruitment of C-Mad2 to kinetochores has not yet been addressed. Here, we show that Mad1 is required for mitotic arrest even when C-Mad2 is artificially recruited to kinetochores, indicating that it has indeed an additional function in promoting the checkpoint. The C-terminal globular domain of Mad1 and conserved residues in this region are required for this unexpected function of Mad1.
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Affiliation(s)
- Thomas Kruse
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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