1
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Kixmoeller K, Chang YW, Black BE. Centromeric chromatin clearings demarcate the site of kinetochore formation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.26.591177. [PMID: 38712116 PMCID: PMC11071481 DOI: 10.1101/2024.04.26.591177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
The centromere is the chromosomal locus that recruits the kinetochore, directing faithful propagation of the genome during cell division. The kinetochore has been interrogated by electron microscopy since the middle of the last century, but with methodologies that compromised fine structure. Using cryo-ET on human mitotic chromosomes, we reveal a distinctive architecture at the centromere: clustered 20-25 nm nucleosome-associated complexes within chromatin clearings that delineate them from surrounding chromatin. Centromere components CENP-C and CENP-N are each required for the integrity of the complexes, while CENP-C is also required to maintain the chromatin clearing. We further visualize the scaffold of the fibrous corona, a structure amplified at unattached kinetochores, revealing crescent-shaped parallel arrays of fibrils that extend >1 μm. Thus, we reveal how the organization of centromeric chromatin creates a clearing at the site of kinetochore formation as well as the nature of kinetochore amplification mediated by corona fibrils.
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Affiliation(s)
- Kathryn Kixmoeller
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Biochemistry Biophysics Chemical Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Penn Center for Genome Integrity, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, PA, USA
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Biochemistry Biophysics Chemical Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, PA, USA
| | - Ben E. Black
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Biochemistry Biophysics Chemical Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Penn Center for Genome Integrity, Perelman School of Medicine, University of Pennsylvania, PA, USA
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, PA, USA
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2
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Weber J, Legal T, Lezcano AP, Gluszek-Kustusz A, Paterson C, Eibes S, Barisic M, Davies OR, Welburn JPI. A conserved CENP-E region mediates BubR1-independent recruitment to the outer corona at mitotic onset. Curr Biol 2024; 34:1133-1141.e4. [PMID: 38354735 DOI: 10.1016/j.cub.2024.01.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 11/28/2023] [Accepted: 01/16/2024] [Indexed: 02/16/2024]
Abstract
The outer corona plays an essential role at the onset of mitosis by expanding to maximize microtubule attachment to kinetochores.1,2 The low-density structure of the corona forms through the expansion of unattached kinetochores. It comprises the RZZ complex, the dynein adaptor Spindly, the plus-end directed microtubule motor centromere protein E (CENP-E), and the Mad1/Mad2 spindle-assembly checkpoint proteins.3,4,5,6,7,8,9,10 CENP-E specifically associates with unattached kinetochores to facilitate chromosome congression,11,12,13,14,15,16 interacting with BubR1 at the kinetochore through its C-terminal region (2091-2358).17,18,19,20,21 We recently showed that CENP-E recruitment to BubR1 at the kinetochores is both rapid and essential for correct chromosome alignment. However, CENP-E is also recruited to the outer corona by a second, slower pathway that is currently undefined.19 Here, we show that BubR1-independent localization of CENP-E is mediated by a conserved loop that is essential for outer-corona targeting. We provide a structural model of the entire CENP-E kinetochore-targeting domain combining X-ray crystallography and Alphafold2. We reveal that maximal recruitment of CENP-E to unattached kinetochores critically depends on BubR1 and the outer corona, including dynein. Ectopic expression of the CENP-E C-terminal domain recruits the RZZ complex, Mad1, and Spindly, and prevents kinetochore biorientation in cells. We propose that BubR1-recruited CENP-E, in addition to its essential role in chromosome alignment to the metaphase plate, contributes to the recruitment of outer corona proteins through interactions with the CENP-E corona-targeting domain to facilitate the rapid capture of microtubules for efficient chromosome alignment and mitotic progression.
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Affiliation(s)
- Jeraldine Weber
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3BF, UK
| | - Thibault Legal
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3BF, UK
| | - Alicia Perez Lezcano
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3BF, UK
| | - Agata Gluszek-Kustusz
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3BF, UK
| | - Calum Paterson
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3BF, UK
| | - Susana Eibes
- Cell Division and Cytoskeleton, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Marin Barisic
- Cell Division and Cytoskeleton, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark; Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 3C Blegdamsvej, 2200 Copenhagen N, Denmark
| | - Owen R Davies
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3BF, UK
| | - Julie P I Welburn
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3BF, UK.
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3
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Barrero DJ, Wijeratne SS, Zhao X, Cunningham GF, Rui Y, Nelson CR, Yasuhiro A, Funabiki H, Asbury CL, Yu Z, Subramanian R, Biggins S. Architecture and flexibility of native kinetochores revealed by structural studies utilizing a thermophilic yeast. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.28.582571. [PMID: 38464254 PMCID: PMC10925344 DOI: 10.1101/2024.02.28.582571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Eukaryotic chromosome segregation requires kinetochores, multi-megadalton protein machines that assemble on the centromeres of chromosomes and mediate attachments to dynamic spindle microtubules. Kinetochores are built from numerous complexes, and understanding how they are arranged is key to understanding how kinetochores perform their multiple functions. However, an integrated understanding of kinetochore architecture has not yet been established. To address this, we purified functional, native kinetochores from Kluyveromyces marxianus and examined them by electron microscopy, cryo-electron tomography and atomic force microscopy. The kinetochores are extremely large, flexible assemblies that exhibit features consistent with prior models. We assigned kinetochore polarity by visualizing their interactions with microtubules and locating the microtubule binder Ndc80c. This work shows that isolated kinetochores are more dynamic and complex than what might be anticipated based on the known structures of recombinant subassemblies, and provides the foundation to study the global architecture and functions of kinetochores at a structural level.
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Affiliation(s)
- Daniel J. Barrero
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N., Seattle, WA 98109, USA
- Molecular and Cellular Biology Program, University of Washington, 1705 NE Pacific Street, Seattle, WA 98195, USA
| | - Sithara S. Wijeratne
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Xiaowei Zhao
- Howard Hughes Medical Institute Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Grace F. Cunningham
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Yan Rui
- Howard Hughes Medical Institute Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Christian R. Nelson
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N., Seattle, WA 98109, USA
| | - Arimura Yasuhiro
- The Rockefeller University, 1230 York Ave., New York, NY 10065, USA
| | | | - Charles L. Asbury
- Department of Physiology and Biophysics, 1959 NE Pacific Street, University of Washington, Seattle, WA 98195, USA
| | - Zhiheng Yu
- Howard Hughes Medical Institute Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Radhika Subramanian
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Sue Biggins
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N., Seattle, WA 98109, USA
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4
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Amin MA, Chakraborty M, Wallace DA, Varma D. Coordination between the Ndc80 complex and dynein is essential for microtubule plus-end capture by kinetochores during early mitosis. J Biol Chem 2023; 299:104711. [PMID: 37060995 PMCID: PMC10206188 DOI: 10.1016/j.jbc.2023.104711] [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: 10/27/2022] [Revised: 03/22/2023] [Accepted: 04/02/2023] [Indexed: 04/17/2023] Open
Abstract
Mitotic kinetochores are initially captured by dynamic microtubules via a "search-and-capture" mechanism. The microtubule motor, dynein, is critical for kinetochore capture as it has been shown to transport microtubule-attached chromosomes toward the spindle pole during prometaphase. The microtubule-binding nuclear division cycle 80 (Ndc80) complex that is recruited to kinetochores in prophase is known to play a central role in forming kinetochore-microtubule (kMT) attachments in metaphase. It is not yet clear, however, how Ndc80 contributes to initial kMT capture during prometaphase. Here, by combining CRISPR/Cas9-mediated knockout and RNAi technology with assays specific to study kMT capture, we show that mitotic cells lacking Ndc80 exhibit substantial defects in this function during prometaphase. Rescue experiments show that Ndc80 mutants deficient in microtubule-binding are unable to execute proper kMT capture. While cells inhibited of dynein alone are predominantly able to make initial kMT attachments, cells co-depleted of Ndc80 and dynein show severe defects in kMT capture. Further, we use an in vitro total internal reflection fluorescence microscopy assay to reconstitute microtubule capture events, which suggest that Ndc80 and dynein coordinate with each other for microtubule plus-end capture and that the phosphorylation status of Ndc80 is critical for productive kMT capture. A novel interaction between Ndc80 and dynein that we identify in prometaphase extracts might be critical for efficient plus-end capture. Thus, our studies, for the first time, identify a distinct event in the formation of initial kMT attachments, which is directly mediated by Ndc80 and in coordination with dynein is required for efficient kMT capture and chromosome alignment.
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Affiliation(s)
- Mohammed Abdullahel Amin
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
| | - Manas Chakraborty
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Destiny Ariel Wallace
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Dileep Varma
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
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5
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Kiewisz R, Fabig G, Conway W, Baum D, Needleman DJ, Müller-Reichert T. Three-dimensional structure of kinetochore-fibers in human mitotic spindles. eLife 2022; 11:75459. [PMID: 35894209 PMCID: PMC9365394 DOI: 10.7554/elife.75459] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 07/24/2022] [Indexed: 11/13/2022] Open
Abstract
During cell division, kinetochore microtubules (KMTs) provide a physical linkage between the chromosomes and the rest of the spindle. KMTs in mammalian cells are organized into bundles, so-called kinetochore-fibers (k-fibers), but the ultrastructure of these fibers is currently not well characterized. Here, we show by large-scale electron tomography that each k-fiber in HeLa cells in metaphase is composed of approximately nine KMTs, only half of which reach the spindle pole. Our comprehensive reconstructions allowed us to analyze the three-dimensional (3D) morphology of k-fibers and their surrounding MTs in detail. We found that k-fibers exhibit remarkable variation in circumference and KMT density along their length, with the pole-proximal side showing a broadening. Extending our structural analysis then to other MTs in the spindle, we further observed that the association of KMTs with non-KMTs predominantly occurs in the spindle pole regions. Our 3D reconstructions have implications for KMT growth and k-fiber self-organization models as covered in a parallel publication applying complementary live-cell imaging in combination with biophysical modeling (Conway et al., 2022). Finally, we also introduce a new visualization tool allowing an interactive display of our 3D spindle data that will serve as a resource for further structural studies on mitosis in human cells.
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Affiliation(s)
- Robert Kiewisz
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Gunar Fabig
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - William Conway
- Department of Physics, Harvard University, Cambridge, United States
| | - Daniel Baum
- Department of Visual and Data-Centric Computing, Zuse Institute Berlin, Berlin, Germany
| | - Daniel J Needleman
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Thomas Müller-Reichert
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
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6
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Renda F, Khodjakov A. Role of spatial patterns and kinetochore architecture in spindle morphogenesis. Semin Cell Dev Biol 2021; 117:75-85. [PMID: 33836948 PMCID: PMC8762378 DOI: 10.1016/j.semcdb.2021.03.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/25/2021] [Accepted: 03/25/2021] [Indexed: 12/30/2022]
Abstract
Mitotic spindle is a self-assembling macromolecular machine responsible for the faithful segregation of chromosomes during cell division. Assembly of the spindle is believed to be governed by the 'Search & Capture' (S&C) principle in which dynamic microtubules explore space in search of kinetochores while the latter capture microtubules and thus connect chromosomes to the spindle. Due to the stochastic nature of the encounters between kinetochores and microtubules, the time required for incorporating all chromosomes into the spindle is profoundly affected by geometric constraints, such as the size and shape of kinetochores as well as their distribution in space at the onset of spindle assembly. In recent years, several molecular mechanisms that control these parameters have been discovered. It is now clear that stochastic S&C takes place in structured space, where components are optimally distributed and oriented to minimize steric hindrances. Nucleation of numerous non-centrosomal microtubules near kinetochores accelerates capture, while changes in the kinetochore architecture at various stages of spindle assembly promote proper connection of sister kinetochores to the opposite spindle poles. Here we discuss how the concerted action of multiple facilitating mechanisms ensure that the spindle assembles rapidly yet with a minimal number of errors.
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Affiliation(s)
- Fioranna Renda
- Biggs Laboratory, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12237, United States.
| | - Alexey Khodjakov
- Biggs Laboratory, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12237, United States; Rensselaer Polytechnic Institute, Troy, NY 12180, United States.
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7
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Hara M, Fukagawa T. Dynamics of kinetochore structure and its regulations during mitotic progression. Cell Mol Life Sci 2020; 77:2981-2995. [PMID: 32052088 PMCID: PMC11104943 DOI: 10.1007/s00018-020-03472-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 12/27/2019] [Accepted: 01/28/2020] [Indexed: 12/12/2022]
Abstract
Faithful chromosome segregation during mitosis in eukaryotes requires attachment of the kinetochore, a large protein complex assembled on the centromere of each chromosome, to the spindle microtubules. The kinetochore is a structural interface for the microtubule attachment and provides molecular surveillance mechanisms that monitor and ensure the precise microtubule attachment as well, including error correction and spindle assembly checkpoint. During mitotic progression, the kinetochore undergoes dynamic morphological changes that are observable through electron microscopy as well as through fluorescence microscopy. These structural changes might be associated with the kinetochore function. In this review, we summarize how the dynamics of kinetochore morphology are associated with its functions and discuss recent findings on the switching of protein interaction networks in the kinetochore during cell cycle progression.
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Affiliation(s)
- Masatoshi Hara
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
| | - Tatsuo Fukagawa
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
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8
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Auckland P, Roscioli E, Coker HLE, McAinsh AD. CENP-F stabilizes kinetochore-microtubule attachments and limits dynein stripping of corona cargoes. J Cell Biol 2020; 219:e201905018. [PMID: 32207772 PMCID: PMC7199848 DOI: 10.1083/jcb.201905018] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 11/04/2019] [Accepted: 02/19/2020] [Indexed: 01/14/2023] Open
Abstract
Accurate chromosome segregation demands efficient capture of microtubules by kinetochores and their conversion to stable bioriented attachments that can congress and then segregate chromosomes. An early event is the shedding of the outermost fibrous corona layer of the kinetochore following microtubule attachment. Centromere protein F (CENP-F) is part of the corona, contains two microtubule-binding domains, and physically associates with dynein motor regulators. Here, we have combined CRISPR gene editing and engineered separation-of-function mutants to define how CENP-F contributes to kinetochore function. We show that the two microtubule-binding domains make distinct contributions to attachment stability and force transduction but are dispensable for chromosome congression. We further identify a specialized domain that functions to limit the dynein-mediated stripping of corona cargoes through a direct interaction with Nde1. This antagonistic activity is crucial for maintaining the required corona composition and ensuring efficient kinetochore biorientation.
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Affiliation(s)
- Philip Auckland
- Centre for Mechanochemical Cell Biology & Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
| | - Emanuele Roscioli
- Centre for Mechanochemical Cell Biology & Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
| | - Helena Louise Elvidge Coker
- Computing and Advanced Microscopy Development Unit, Warwick Medical School, University of Warwick, Coventry, UK
| | - Andrew D. McAinsh
- Centre for Mechanochemical Cell Biology & Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
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9
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Ng CT, Deng L, Chen C, Lim HH, Shi J, Surana U, Gan L. Electron cryotomography analysis of Dam1C/DASH at the kinetochore-spindle interface in situ. J Cell Biol 2018; 218:455-473. [PMID: 30504246 PMCID: PMC6363454 DOI: 10.1083/jcb.201809088] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 10/25/2018] [Accepted: 10/31/2018] [Indexed: 01/01/2023] Open
Abstract
In dividing cells, depolymerizing spindle microtubules move chromosomes by pulling at their kinetochores. While kinetochore subcomplexes have been studied extensively in vitro, little is known about their in vivo structure and interactions with microtubules or their response to spindle damage. Here we combine electron cryotomography of serial cryosections with genetic and pharmacological perturbation to study the yeast chromosome segregation machinery in vivo. Each kinetochore microtubule has one (rarely, two) Dam1C/DASH outer kinetochore assemblies. Dam1C/DASH contacts the microtubule walls and does so with its flexible "bridges"; there are no contacts with the protofilaments' curved tips. In metaphase, ∼40% of the Dam1C/DASH assemblies are complete rings; the rest are partial rings. Ring completeness and binding position along the microtubule are sensitive to kinetochore attachment and tension, respectively. Our study and those of others support a model in which each kinetochore must undergo cycles of conformational change to couple microtubule depolymerization to chromosome movement.
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Affiliation(s)
- Cai Tong Ng
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore
| | - Li Deng
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore
| | - Chen Chen
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore
| | - Hong Hwa Lim
- Institute of Molecular and Cell Biology Agency for Science Technology and Research, Singapore.,Bioprocessing Technology Institute, Agency for Science Technology and Research, Singapore
| | - Jian Shi
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore
| | - Uttam Surana
- Institute of Molecular and Cell Biology Agency for Science Technology and Research, Singapore.,Bioprocessing Technology Institute, Agency for Science Technology and Research, Singapore.,Department of Pharmacology, National University of Singapore, Singapore
| | - Lu Gan
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore
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10
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Sacristan C, Ahmad MUD, Keller J, Fermie J, Groenewold V, Tromer E, Fish A, Melero R, Carazo JM, Klumperman J, Musacchio A, Perrakis A, Kops GJ. Dynamic kinetochore size regulation promotes microtubule capture and chromosome biorientation in mitosis. Nat Cell Biol 2018; 20:800-810. [PMID: 29915359 PMCID: PMC6485389 DOI: 10.1038/s41556-018-0130-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 05/22/2018] [Indexed: 01/28/2023]
Abstract
Faithful chromosome segregation depends on the ability of sister kinetochores to attach to spindle microtubules. The outer layer of kinetochores transiently expands in early mitosis to form a fibrous corona, and compacts following microtubule capture. Here we show that the dynein adaptor Spindly and the RZZ (ROD-Zwilch-ZW10) complex drive kinetochore expansion in a dynein-independent manner. C-terminal farnesylation and MPS1 kinase activity cause conformational changes of Spindly that promote oligomerization of RZZ-Spindly complexes into a filamentous meshwork in cells and in vitro. Concurrent with kinetochore expansion, Spindly potentiates kinetochore compaction by recruiting dynein via three conserved short linear motifs. Expanded kinetochores unable to compact engage in extensive, long-lived lateral microtubule interactions that persist to metaphase, and result in merotelic attachments and chromosome segregation errors in anaphase. Thus, dynamic kinetochore size regulation in mitosis is coordinated by a single, Spindly-based mechanism that promotes initial microtubule capture and subsequent correct maturation of attachments.
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Affiliation(s)
- Carlos Sacristan
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht, The Netherlands
| | - Misbha Ud Din Ahmad
- Department of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Jenny Keller
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Job Fermie
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Vincent Groenewold
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Eelco Tromer
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht, The Netherlands
| | - Alexander Fish
- Department of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Roberto Melero
- Biocomputing Unit, National Center for Biotechnology (CSIC), Darwin 3, Campus Universidad Autónoma, Madrid, Spain
| | - José María Carazo
- Biocomputing Unit, National Center for Biotechnology (CSIC), Darwin 3, Campus Universidad Autónoma, Madrid, Spain
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - 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, Universitätsstraße, Essen, Germany
| | - Anastassis Perrakis
- Department of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Geert Jpl Kops
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht, The Netherlands.
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11
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Nechipurenko IV, Sengupta P. The rise and fall of basal bodies in the nematode Caenorhabditis elegans. Cilia 2017; 6:9. [PMID: 28770089 PMCID: PMC5530580 DOI: 10.1186/s13630-017-0053-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 07/11/2017] [Indexed: 11/17/2022] Open
Abstract
The free-living nematode, Caenorhabditis elegans, is a widely used genetic model organism for investigations into centriole and cilia biology. Only sensory neurons are ciliated in C. elegans; morphologically diverse cilia in these neurons are nucleated by basal bodies located at the dendritic endings. C. elegans centrioles comprise a central tube with a symmetric array of nine singlet microtubules. These singlet microtubules remodel in a subset of sensory neurons to form the doublet microtubules of the basal bodies. Following initiation of ciliogenesis, the central tube, but not the outer centriole wall, of the basal body degenerates. Recent ultrastructural characterization of basal body architecture and remodeling have laid the foundation for future studies into mechanisms underlying different aspects of basal body genesis, remodeling, and intracellular positioning.
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Affiliation(s)
- Inna V Nechipurenko
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454 USA
| | - Piali Sengupta
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454 USA
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12
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C. elegans chromosomes connect to centrosomes by anchoring into the spindle network. Nat Commun 2017; 8:15288. [PMID: 28492281 PMCID: PMC5437269 DOI: 10.1038/ncomms15288] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Accepted: 03/10/2017] [Indexed: 11/19/2022] Open
Abstract
The mitotic spindle ensures the faithful segregation of chromosomes. Here we combine the first large-scale serial electron tomography of whole mitotic spindles in early C. elegans embryos with live-cell imaging to reconstruct all microtubules in 3D and identify their plus- and minus-ends. We classify them as kinetochore (KMTs), spindle (SMTs) or astral microtubules (AMTs) according to their positions, and quantify distinct properties of each class. While our light microscopy and mutant studies show that microtubules are nucleated from the centrosomes, we find only a few KMTs directly connected to the centrosomes. Indeed, by quantitatively analysing several models of microtubule growth, we conclude that minus-ends of KMTs have selectively detached and depolymerized from the centrosome. In toto, our results show that the connection between centrosomes and chromosomes is mediated by an anchoring into the entire spindle network and that any direct connections through KMTs are few and likely very transient. A connection between centrosomes and chromosomes is a key feature of mitotic spindles. Here the authors generate 3D reconstructions of whole mitotic spindles in early C. elegans embryos and show that chromosomes are anchored by the entire spindle network and that connections through kinetochore microtubules are few and likely very transient.
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13
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Nechipurenko IV, Berciu C, Sengupta P, Nicastro D. Centriolar remodeling underlies basal body maturation during ciliogenesis in Caenorhabditis elegans. eLife 2017; 6. [PMID: 28411364 PMCID: PMC5392363 DOI: 10.7554/elife.25686] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/15/2017] [Indexed: 12/31/2022] Open
Abstract
The primary cilium is nucleated by the mother centriole-derived basal body (BB) via as yet poorly characterized mechanisms. BBs have been reported to degenerate following ciliogenesis in the C. elegans embryo, although neither BB architecture nor early ciliogenesis steps have been described in this organism. In a previous study (Doroquez et al., 2014), we described the three-dimensional morphologies of sensory neuron cilia in adult C. elegans hermaphrodites at high resolution. Here, we use serial section electron microscopy and tomography of staged C. elegans embryos to demonstrate that BBs remodel to support ciliogenesis in a subset of sensory neurons. We show that centriolar singlet microtubules are converted into BB doublets which subsequently grow asynchronously to template the ciliary axoneme, visualize degeneration of the centriole core, and define the developmental stage at which the transition zone is established. Our work provides a framework for future investigations into the mechanisms underlying BB remodeling. DOI:http://dx.doi.org/10.7554/eLife.25686.001
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Affiliation(s)
- Inna V Nechipurenko
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Cristina Berciu
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States
| | - Piali Sengupta
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Daniela Nicastro
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States.,Departments of Cell Biology and Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
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14
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Abstract
Mutations in cancer cells frequently result in cell cycle alterations that lead to unrestricted growth compared to normal cells. Considering this phenomenon, many drugs have been developed to inhibit different cell-cycle phases. Mitotic phase targeting disturbs mitosis in tumor cells, triggers the spindle assembly checkpoint and frequently results in cell death. The first anti-mitotics to enter clinical trials aimed to target tubulin. Although these drugs improved the treatment of certain cancers, and many anti-microtubule compounds are already approved for clinical use, severe adverse events such as neuropathies were observed. Since then, efforts have been focused on the development of drugs that also target kinases, motor proteins and multi-protein complexes involved in mitosis. In this review, we summarize the major proteins involved in the mitotic phase that can also be targeted for cancer treatment. Finally, we address the activity of anti-mitotic drugs tested in clinical trials in recent years.
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15
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Grishchuk EL. Biophysics of Microtubule End Coupling at the Kinetochore. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2017; 56:397-428. [PMID: 28840247 DOI: 10.1007/978-3-319-58592-5_17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The main physiological function of mitotic kinetochores is to provide durable attachment to spindle microtubules, which segregate chromosomes in order to partition them equally between the two daughter cells. Numerous kinetochore components that can bind directly to microtubules have been identified, including ATP-dependent motors and various microtubule-associated proteins with no motor activity. A major challenge facing the field is to explain chromosome motions based on the biochemical and structural properties of these individual kinetochore components and their assemblies. This chapter reviews the molecular mechanisms responsible for the motions associated with dynamic microtubule tips at the single-molecule level, as well as the activities of multimolecular ensembles called couplers. These couplers enable persistent kinetochore motion even under load, but their exact composition and structure remain unknown. Because no natural or artificial macro-machines function in an analogous manner to these molecular nano-devices, understanding their underlying biophysical mechanisms will require conceptual advances.
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Affiliation(s)
- Ekaterina L Grishchuk
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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16
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Chung HJ, Park JE, Lee NS, Kim H, Jang CY. Phosphorylation of Astrin Regulates Its Kinetochore Function. J Biol Chem 2016; 291:17579-92. [PMID: 27325694 PMCID: PMC5016155 DOI: 10.1074/jbc.m115.712745] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 06/16/2016] [Indexed: 01/09/2023] Open
Abstract
The error-free segregation of chromosomes, which requires the precisely timed search and capture of chromosomes by spindles during early mitotic and meiotic cell division, is responsible for genomic stability and is achieved by the spindle assembly checkpoint in the metaphase-anaphase transition. Mitotic kinases orchestrate M phase events, such as the reorganization of cell architecture and kinetochore (KT) composition with the exquisite phosphorylation of mitotic regulators, to ensure timely and temporal progression. However, the molecular mechanisms underlying the changes of KT composition for stable spindle attachment during mitosis are poorly understood. Here, we show that the sequential action of the kinase Cdk1 and the phosphatase Cdc14A control spindle attachment to KTs. During prophase, the mitotic spindle protein Spag5/Astrin is transported into centrosomes by Kinastrin and phosphorylated at Ser-135 and Ser-249 by Cdk1, which, in prometaphase, is loaded onto the spindle and targeted to KTs. We also demonstrate that Cdc14A dephosphorylates Astrin, and therefore the overexpression of Cdc14A sequesters Astrin in the centrosome and results in aberrant chromosome alignment. Mechanistically, Plk1 acts as an upstream kinase for Astrin phosphorylation by Cdk1 and targeting phospho-Astrin to KTs, leading to the recruitment of outer KT components, such as Cenp-E, and the stable attachment of spindles to KTs. These comprehensive findings reveal a regulatory circuit for protein targeting to KTs that controls the KT composition change of stable spindle attachment and chromosome integrity.
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Affiliation(s)
- Hee Jin Chung
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea and
| | - Ji Eun Park
- Research Center for Cell Fate Control, College of Pharmacy, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Nam Soo Lee
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea and
| | - Hongtae Kim
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea and From the Center for Neuroscience Imaging Research, Institute for Basic Science and
| | - Chang-Young Jang
- Research Center for Cell Fate Control, College of Pharmacy, Sookmyung Women's University, Seoul 04310, Republic of Korea
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17
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Magidson V, He J, Ault JG, O'Connell CB, Yang N, Tikhonenko I, McEwen BF, Sui H, Khodjakov A. Unattached kinetochores rather than intrakinetochore tension arrest mitosis in taxol-treated cells. J Cell Biol 2016; 212:307-19. [PMID: 26833787 PMCID: PMC4748573 DOI: 10.1083/jcb.201412139] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Taxol induces extensive structural reorganization of the mammalian kinetochore; however, this reorganization is not sufficient to maintain a long-term mitotic arrest unless some of the kinetochores completely lose their attachment to microtubules. Kinetochores attach chromosomes to the spindle microtubules and signal the spindle assembly checkpoint to delay mitotic exit until all chromosomes are attached. Light microscopy approaches aimed to indirectly determine distances between various proteins within the kinetochore (termed Delta) suggest that kinetochores become stretched by spindle forces and compact elastically when the force is suppressed. Low Delta is believed to arrest mitotic progression in taxol-treated cells. However, the structural basis of Delta remains unknown. By integrating same-kinetochore light microscopy and electron microscopy, we demonstrate that the value of Delta is affected by the variability in the shape and size of outer kinetochore domains. The outer kinetochore compacts when spindle forces are maximal during metaphase. When the forces are weakened by taxol treatment, the outer kinetochore expands radially and some kinetochores completely lose microtubule attachment, a condition known to arrest mitotic progression. These observations offer an alternative interpretation of intrakinetochore tension and question whether Delta plays a direct role in the control of mitotic progression.
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Affiliation(s)
- Valentin Magidson
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | - Jie He
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | - Jeffrey G Ault
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | | | - Nachen Yang
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | - Irina Tikhonenko
- Wadsworth Center, New York State Department of Health, Albany, NY 12201
| | - Bruce F McEwen
- Wadsworth Center, New York State Department of Health, Albany, NY 12201 School of Public Health, State University of New York, Albany, NY 12201
| | - Haixin Sui
- Wadsworth Center, New York State Department of Health, Albany, NY 12201 School of Public Health, State University of New York, Albany, NY 12201
| | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, NY 12201 Rensselaer Polytechnic Institute, Troy, NY 12180
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18
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Wynne DJ, Funabiki H. Heterogeneous architecture of vertebrate kinetochores revealed by three-dimensional superresolution fluorescence microscopy. Mol Biol Cell 2016; 27:3395-3404. [PMID: 27170176 PMCID: PMC5221576 DOI: 10.1091/mbc.e16-02-0130] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/04/2016] [Indexed: 11/11/2022] Open
Abstract
Superresolution fluorescence microscopy of vertebrate kinetochore proteins reveals that outer kinetochore components assume diverse distribution patterns, including a ring-like configuration encircling the CENP-A–marked centromeric chromatin on the metaphase spindle in Xenopus egg extracts. The kinetochore is often depicted as having a disk-like architecture in which the outer layer of proteins, which engage microtubules and control checkpoint signaling, are built on a static inner layer directly linked to CENP-A chromatin. Here, applying three-dimensional (3D) structural illumination microscopy (SIM) and stochastic optical reconstruction microscopy (STORM) to Xenopus egg extracts and tissue culture cells, we report various distribution patterns of inner and outer kinetochore proteins. In egg extracts, a configuration in which outer kinetochore proteins surround the periphery of CENP-A chromatin is common, forming an ∼200-nm ring-like organization that may engage a bundle of microtubule ends. Similar rings are observed in Xenopus tissue culture cells at a lower frequency but are enriched in conditions in which the spindle is disorganized. Although rings are rare in human cells, the distribution of both inner and outer kinetochore proteins elongates in the absence of microtubule attachment in a manner dependent on Aurora B. We propose a model in which the 3D organization of both the outer and inner kinetochore regions respond to the progression from lateral to end-on microtubule attachments by coalescing into a tight disk from less uniform distributions early in prometaphase.
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Affiliation(s)
- David J Wynne
- Laboratory of Chromosome and Cell Biology, Rockefeller University, New York, NY 10065.,Department of Biology, College of New Jersey, Ewing, NJ 08628
| | - Hironori Funabiki
- Laboratory of Chromosome and Cell Biology, Rockefeller University, New York, NY 10065
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19
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Singleton MR. Getting to the heart of an unusual kinetochore. Open Biol 2016; 6:160040. [PMID: 27249344 PMCID: PMC4852463 DOI: 10.1098/rsob.160040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 03/18/2016] [Indexed: 11/18/2022] Open
Abstract
The Mis12 complex forms the central scaffold of the kinetochore and serves to bridge the chromatin and microtubule-binding activities of the inner and outer layers, respectively. Two recent studies provide new structural insights into the formation of this complex, and highlight some intriguing adaptations found in the Drosophila kinetochore.
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Affiliation(s)
- Martin R Singleton
- Structural Biology of Chromosome Segregation Laboratory, The Francis Crick Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
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20
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Wynne DJ, Funabiki H. Kinetochore function is controlled by a phospho-dependent coexpansion of inner and outer components. J Cell Biol 2015; 210:899-916. [PMID: 26347137 PMCID: PMC4576862 DOI: 10.1083/jcb.201506020] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is widely accepted that the kinetochore is built on CENP-A-marked centromeric chromatin in a hierarchical order from inner to outer kinetochore. Recruitment of many kinetochore proteins depends on microtubule attachment status, but it remains unclear how their assembly/disassembly is orchestrated. Applying 3D structured illumination microscopy to Xenopus laevis egg extracts, here we reveal that in the absence of microtubule attachment, proteins responsible for lateral attachment and spindle checkpoint signaling expand to form micrometer-scale fibrous structures over CENP-A-free chromatin, whereas a core module responsible for end-on attachment (CENP-A, CENP-T, and Ndc80) does not. Both outer kinetochore proteins (Bub1, BubR1, Mad1, and CENP-E) and the inner kinetochore component CENP-C are integral components of the expandable module, whose assembly depends on multiple mitotic kinases (Aurora B, Mps1, and Plx1) and is suppressed by protein phosphatase 1. We propose that phospho-dependent coexpansion of CENP-C and outer kinetochore proteins promotes checkpoint signal amplification and lateral attachment, whereas their selective disassembly enables the transition to end-on attachment.
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21
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Doroquez DB, Berciu C, Anderson JR, Sengupta P, Nicastro D. A high-resolution morphological and ultrastructural map of anterior sensory cilia and glia in Caenorhabditis elegans. eLife 2014; 3:e01948. [PMID: 24668170 PMCID: PMC3965213 DOI: 10.7554/elife.01948] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Accepted: 02/17/2014] [Indexed: 12/22/2022] Open
Abstract
Many primary sensory cilia exhibit unique architectures that are critical for transduction of specific sensory stimuli. Although basic ciliogenic mechanisms are well described, how complex ciliary structures are generated remains unclear. Seminal work performed several decades ago provided an initial but incomplete description of diverse sensory cilia morphologies in C. elegans. To begin to explore the mechanisms that generate these remarkably complex structures, we have taken advantage of advances in electron microscopy and tomography, and reconstructed three-dimensional structures of fifty of sixty sensory cilia in the C. elegans adult hermaphrodite at high resolution. We characterize novel axonemal microtubule organization patterns, clarify structural features at the ciliary base, describe new aspects of cilia-glia interactions, and identify structures suggesting novel mechanisms of ciliary protein trafficking. This complete ultrastructural description of diverse cilia in C. elegans provides the foundation for investigations into underlying ciliogenic pathways, as well as contributions of defined ciliary structures to specific neuronal functions. DOI: http://dx.doi.org/10.7554/eLife.01948.001.
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Affiliation(s)
- David B Doroquez
- Department of Biology, Brandeis University, Waltham, United States
- National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Cristina Berciu
- Department of Biology, Brandeis University, Waltham, United States
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States
| | - James R Anderson
- Department of Ophthalmology, John A Moran Eye Center, University of Utah School of Medicine, Salt Lake City, United States
| | - Piali Sengupta
- Department of Biology, Brandeis University, Waltham, United States
- National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Daniela Nicastro
- Department of Biology, Brandeis University, Waltham, United States
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States
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22
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McIntosh JR, O'Toole E, Zhudenkov K, Morphew M, Schwartz C, Ataullakhanov FI, Grishchuk EL. Conserved and divergent features of kinetochores and spindle microtubule ends from five species. ACTA ACUST UNITED AC 2013; 200:459-74. [PMID: 23420873 PMCID: PMC3575531 DOI: 10.1083/jcb.201209154] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A comprehensive, cross-species electron tomography analysis of kinetochore–microtubule interfaces has provided insight into shared structural features and their likely functional consequences. Interfaces between spindle microtubules and kinetochores were examined in diverse species by electron tomography and image analysis. Overall structures were conserved in a mammal, an alga, a nematode, and two kinds of yeasts; all lacked dense outer plates, and most kinetochore microtubule ends flared into curved protofilaments that were connected to chromatin by slender fibrils. Analyses of curvature on >8,500 protofilaments showed that all classes of spindle microtubules displayed some flaring protofilaments, including those growing in the anaphase interzone. Curved protofilaments on anaphase kinetochore microtubules were no more flared than their metaphase counterparts, but they were longer. Flaring protofilaments in budding yeasts were linked by fibrils to densities that resembled nucleosomes; these are probably the yeast kinetochores. Analogous densities in fission yeast were larger and less well-defined, but both yeasts showed ring- or partial ring-shaped structures girding their kinetochore microtubules. Flaring protofilaments linked to chromatin are well placed to exert force on chromosomes, assuring stable attachment and reliable anaphase segregation.
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Affiliation(s)
- J Richard McIntosh
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
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23
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Tanaka K. Dynamic regulation of kinetochore-microtubule interaction during mitosis. J Biochem 2012; 152:415-24. [DOI: 10.1093/jb/mvs109] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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24
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Akiyoshi B, Biggins S. Reconstituting the kinetochore–microtubule interface: what, why, and how. Chromosoma 2012; 121:235-50. [PMID: 22289864 DOI: 10.1007/s00412-012-0362-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 01/15/2012] [Accepted: 01/16/2012] [Indexed: 10/14/2022]
Abstract
The kinetochore is the proteinaceous complex that governs the movement of duplicated chromosomes by interacting with spindle microtubules during mitosis and meiosis. Faithful chromosome segregation requires that kinetochores form robust load-bearing attachments to the tips of dynamic spindle microtubules, correct microtubule attachment errors, and delay the onset of anaphase until all chromosomes have made proper attachments. To understand how this macromolecular machine operates to segregate duplicated chromosomes with exquisite accuracy, it is critical to reconstitute and study kinetochore–microtubule interactions in vitro using defined components. Here, we review the current status of reconstitution as well as recent progress in understanding the microtubule-binding functions of kinetochores in vivo.
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Affiliation(s)
- Bungo Akiyoshi
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK.
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25
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Yao Y, Dai W. Shugoshins function as a guardian for chromosomal stability in nuclear division. Cell Cycle 2012; 11:2631-42. [PMID: 22732496 PMCID: PMC3850027 DOI: 10.4161/cc.20633] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 05/04/2012] [Indexed: 11/19/2022] Open
Abstract
Accurate chromosome segregation during mitosis and meiosis is regulated and secured by several distinctly different yet intricately connected regulatory mechanisms. As chromosomal instability is a hallmark of a majority of tumors as well as a cause of infertility for germ cells, extensive research in the past has focused on the identification and characterization of molecular components that are crucial for faithful chromosome segregation during cell division. Shugoshins, including Sgo1 and Sgo2, are evolutionarily conserved proteins that function to protect sister chromatid cohesion, thus ensuring chromosomal stability during mitosis and meiosis in eukaryotes. Recent studies reveal that Shugoshins in higher animals play an essential role not only in protecting centromeric cohesion of sister chromatids and assisting bi-orientation attachment at the kinetochores, but also in safeguarding centriole cohesion/engagement during early mitosis. Many molecular components have been identified that play essential roles in modulating/mediating Sgo functions. This review primarily summarizes recent advances on the mechanisms of action of Shugoshins in suppressing chromosomal instability during nuclear division in eukaryotic organisms.
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Affiliation(s)
- Yixin Yao
- Departments of Environmental Medicine and Pharmacology; New York University School of Medicine; Tuxedo, NY USA
| | - Wei Dai
- Departments of Environmental Medicine and Pharmacology; New York University School of Medicine; Tuxedo, NY USA
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26
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Abstract
Mitosis is the process by which eukaryotic cells organize and segregate their chromosomes in preparation for cell division. It is accomplished by a cellular machine composed largely of microtubules (MTs) and their associated proteins. This article reviews literature on mitosis from a biophysical point of view, drawing attention to the assembly and motility processes required to do this complex job with precision. Work from both the recent and the older literature is integrated into a description of relevant biological events and the experiments that probe their mechanisms. Theoretical work on specific subprocesses is also reviewed. Our goal is to provide a document that will expose biophysicists to the fascination of this quite amazing process and provide them with a good background from which they can pursue their own research interests in the subject.
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27
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Kinetochore flexibility: creating a dynamic chromosome-spindle interface. Curr Opin Cell Biol 2012; 24:40-7. [PMID: 22221609 DOI: 10.1016/j.ceb.2011.12.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 12/02/2011] [Accepted: 12/13/2011] [Indexed: 11/23/2022]
Abstract
Kinetochores are complex macromolecular assemblies that link chromosomes to the mitotic spindle, mediate forces for chromosome motion, and generate the checkpoint signal delaying anaphase onset until all chromosomes are incorporated into the spindle. Proper execution of these functions depends on precise interactions between kinetochores and microtubules. While the molecular composition of the kinetochore is well described, structural organization of this organelle at the molecular and atomic levels is just beginning to emerge. Recent structural studies across scales suggest that kinetochores should not be viewed as rigid static scaffolds. Instead, these organelles exhibit a surprising degree of flexibility that enables rapid adaptations to various types of interactions with the mitotic spindle.
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28
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Suzuki A, Hori T, Nishino T, Usukura J, Miyagi A, Morikawa K, Fukagawa T. Spindle microtubules generate tension-dependent changes in the distribution of inner kinetochore proteins. ACTA ACUST UNITED AC 2011; 193:125-40. [PMID: 21464230 PMCID: PMC3082190 DOI: 10.1083/jcb.201012050] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The kinetochore forms a dynamic interface with microtubules from the mitotic spindle. Live-cell light microscopy-based observations on the dynamic structural changes within the kinetochore suggest that molecular rearrangements within the kinetochore occur upon microtubule interaction. However, the source of these rearrangements is still unclear. In this paper, we analyze vertebrate kinetochore ultrastructure by immunoelectron microscopy (EM) in the presence or absence of tension from spindle microtubules. We found that the inner kinetochore region defined by CENP-A, CENP-C, CENP-R, and the C-terminal domain of CENP-T is deformed in the presence of tension, whereas the outer kinetochore region defined by Ndc80, Mis12, and CENP-E is not stretched even under tension. Importantly, based on EM, fluorescence microscopy, and in vitro analyses, we demonstrated that the N and C termini of CENP-T undergo a tension-dependent separation, suggesting that CENP-T elongation is at least partly responsible for changes in the shape of the inner kinetochore.
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Affiliation(s)
- Aussie Suzuki
- Department of Molecular Genetics, National Institute of Genetics, The Graduate University for Advanced Studies, Mishima, Shizuoka 411-8540, Japan
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29
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McIntosh JR, Volkov V, Ataullakhanov FI, Grishchuk EL. Tubulin depolymerization may be an ancient biological motor. J Cell Sci 2011; 123:3425-34. [PMID: 20930138 DOI: 10.1242/jcs.067611] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The motions of mitotic chromosomes are complex and show considerable variety across species. A wealth of evidence supports the idea that microtubule-dependent motor enzymes contribute to this variation and are important both for spindle formation and for the accurate completion of chromosome segregation. Motors that walk towards the spindle pole are, however, dispensable for at least some poleward movements of chromosomes in yeasts, suggesting that depolymerizing spindle microtubules can generate mitotic forces in vivo. Tubulin protofilaments that flare outward in association with microtubule shortening may be the origin of such forces, because they can move objects that are appropriately attached to a microtubule wall. For example, some kinetochore-associated proteins can couple experimental objects, such as microspheres, to shortening microtubules in vitro, moving them over many micrometers. Here, we review recent evidence about such phenomena, highlighting the force-generation mechanisms and different coupling strategies. We also consider bending filaments of the tubulin-like protein FtsZ, which form rings girding bacteria at their sites of cytokinesis. Mechanical similarities between these force-generation systems suggest a deep phylogenetic relationship between tubulin depolymerization in eukaryotic mitosis and FtsZ-mediated ring contraction in bacteria.
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Affiliation(s)
- J Richard McIntosh
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
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30
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Sobol M, Nebesářová J, Hozák P. A method for preserving ultrastructural properties of mitotic cells for subsequent immunogold labeling using low-temperature embedding in LR White resin. Histochem Cell Biol 2010; 135:103-10. [DOI: 10.1007/s00418-010-0771-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
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Comparison of methods of high-pressure freezing and automated freeze-substitution of suspension cells combined with LR White embedding. Histochem Cell Biol 2010; 134:631-41. [DOI: 10.1007/s00418-010-0757-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2010] [Indexed: 10/18/2022]
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McEwen BF, Dong Y. Contrasting models for kinetochore microtubule attachment in mammalian cells. Cell Mol Life Sci 2010; 67:2163-72. [PMID: 20336345 PMCID: PMC2883615 DOI: 10.1007/s00018-010-0322-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 02/17/2010] [Indexed: 12/16/2022]
Abstract
Kinetochore function is mediated through its interaction with microtubule plus ends embedded in the kinetochore outer plate. Here, we compare and evaluate current models for kinetochore microtubule attachment, beginning with a brief review of the molecular, biochemical, cellular, and structural studies upon which these models are based. The majority of these studies strongly support a model in which the kinetochore outer plate is a network of fibers that form multiple weak attachments to each microtubule, chiefly through the Ndc80 complex. Multiple weak attachments enable kinetochores to remain attached to microtubule plus ends that are continually growing and shrinking. It is unlikely that rings or "kinetochore fibrils" have a significant role in kinetochore microtubule attachment, but such entities could have a role in stabilizing attachment, modifying microtubule dynamics, and harnessing the energy released from microtubule disassembly. It is currently unclear whether kinetochores control and coordinate the dynamics of individual kinetochore microtubules.
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Affiliation(s)
- Bruce F McEwen
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA.
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Abstract
For over a century, scientists have strived to understand the mechanisms that govern the accurate segregation of chromosomes during mitosis. The most intriguing feature of this process, which is particularly prominent in higher eukaryotes, is the complex behaviour exhibited by the chromosomes. This behaviour is based on specific and highly regulated interactions between the chromosomes and spindle microtubules. Recent discoveries, enabled by high-resolution imaging combined with the various genetic, molecular, cell biological and chemical tools, support the idea that establishing and controlling the dynamic interaction between chromosomes and microtubules is a major factor in genomic fidelity.
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Bader JR, Vaughan KT. Dynein at the kinetochore: Timing, Interactions and Functions. Semin Cell Dev Biol 2010; 21:269-75. [PMID: 20045078 DOI: 10.1016/j.semcdb.2009.12.015] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 12/22/2009] [Indexed: 01/31/2023]
Abstract
Kinetochores have been proposed to play multiple roles in mitotic chromosome alignment, including initial microtubule (MT) capture, monitoring MT attachments, prometaphase and anaphase chromosome movement and tension generation at metaphase. In addition, kinetochores are essential components of the spindle assembly checkpoint (SAC), and couple chromosome alignment with SAC silencing at metaphase. Although the molecular details of these activities remain under investigation, cytoplasmic dynein has been implicated in several aspects of MT and SAC regulation. Recent work clarifies the contribution of dynein to MT interactions and to events that drive anaphase onset. This review summarizes these studies and provides new models for dynein function.
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Affiliation(s)
- Jason R Bader
- Department of Biological Sciences, University of Notre Dame, Galvin Life Sciences Center, Notre Dame, IN 46556, United States
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McDonald K, Schwarz H, Müller-Reichert T, Webb R, Buser C, Morphew M. "Tips and tricks" for high-pressure freezing of model systems. Methods Cell Biol 2010; 96:671-93. [PMID: 20869543 DOI: 10.1016/s0091-679x(10)96028-7] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
High-pressure freezing (HPF) has been around since the mid-1980s as a cryopreparation technique for biological electron microscopy. It has taken quite some time to "catch on" but with the recent interest in cellular tomography and electron microscopy of vitreous cryosections it has been used more frequently. While HPF is relatively easy to do, there are a number of steps, such as loading the sample into the specimen carrier correctly, that are critical to the success of this method. In this chapter we discuss some of the "little" things that can make the difference between successful or unsuccessful freezing. We cover all aspects of HPF, from specimen loading to removing your sample from the carriers in polymerized resin. Our goal is to make it easier and more reliable for HPF users to get well-frozen samples for their research.
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Affiliation(s)
- Kent McDonald
- Electron Microscope Laboratory, University of California, Berkeley, California 94720, USA
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Martens G, Humphrey EC, Harrison LG, Silva-Moreno B, Ausió J, Kasinsky HE. High-pressure freezing of spermiogenic nuclei supports a dynamic chromatin model for the histone-to-protamine transition. J Cell Biochem 2009; 108:1399-409. [DOI: 10.1002/jcb.22373] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Abstract
Kinetochores are large protein assemblies built on chromosomal loci named centromeres. The main functions of kinetochores can be grouped under four modules. The first module, in the inner kinetochore, contributes a sturdy interface with centromeric chromatin. The second module, the outer kinetochore, contributes a microtubule-binding interface. The third module, the spindle assembly checkpoint, is a feedback control mechanism that monitors the state of kinetochore-microtubule attachment to control the progression of the cell cycle. The fourth module discerns correct from improper attachments, preventing the stabilization of the latter and allowing the selective stabilization of the former. In this review, we discuss how the molecular organization of the four modules allows a dynamic integration of kinetochore-microtubule attachment with the prevention of chromosome segregation errors and cell-cycle progression.
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Affiliation(s)
- Stefano Santaguida
- Department of Experimental Oncology, European Institute of Oncology, Milan, Italy
| | - Andrea Musacchio
- Department of Experimental Oncology, European Institute of Oncology, Milan, Italy
- Research Unit of the Italian Institute of Technology at the IFOM-IEO Campus, Milan, Italy
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38
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Stable kinetochore-microtubule interactions depend on the Ska complex and its new component Ska3/C13Orf3. EMBO J 2009; 28:1442-52. [PMID: 19360002 PMCID: PMC2669960 DOI: 10.1038/emboj.2009.96] [Citation(s) in RCA: 168] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Accepted: 03/20/2009] [Indexed: 01/21/2023] Open
Abstract
Ska1 and Ska2 form a complex at the kinetochore–microtubule (KT–MT) interface and are required for timely progression from metaphase to anaphase. Here, we use mass spectrometry to search for additional components of the Ska complex. We identify C13Orf3 (now termed Ska3) as a novel member of this complex and map the interaction domains among the three known components. Ska3 displays similar characteristics as Ska1 and Ska2: it localizes to the spindle and KT throughout mitosis and its depletion markedly delays anaphase transition. Interestingly, a more complete removal of the Ska complex by concomitant depletion of Ska1 and Ska3 results in a chromosome congression failure followed by cell death. This severe phenotype reflects a destabilization of KT–MT interactions, as demonstrated by reduced cold stability of KT fibres. Yet, the depletion of the Ska complex only marginally impairs KT localization of the KMN network responsible for MT attachment. We propose that the Ska complex functionally complements the KMN, providing an additional layer of stability to KT–MT attachment and possibly signalling completion of attachment to the spindle checkpoint.
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Abstract
Chromosome segregation in eukaryotes requires a large molecular assembly termed the kinetochore to attach chromosomes to spindle microtubules. Recent work has made substantial progress in defining the composition and activities of the kinetochore, but much remains to be learned about its macromolecular structure. This commentary discusses recent insights into structural features of the kinetochore, how these inform our understanding of its biological function, and the key challenges for the future.
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Affiliation(s)
- Julie P I Welburn
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center, Cambridge, MA 02142, USA.
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Whyte J, Bader JR, Tauhata SBF, Raycroft M, Hornick J, Pfister KK, Lane WS, Chan GK, Hinchcliffe EH, Vaughan PS, Vaughan KT. Phosphorylation regulates targeting of cytoplasmic dynein to kinetochores during mitosis. ACTA ACUST UNITED AC 2008; 183:819-34. [PMID: 19029334 PMCID: PMC2592828 DOI: 10.1083/jcb.200804114] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytoplasmic dynein functions at several sites during mitosis; however, the basis of targeting to each site remains unclear. Tandem mass spectrometry analysis of mitotic dynein revealed a phosphorylation site in the dynein intermediate chains (ICs) that mediates binding to kinetochores. IC phosphorylation directs binding to zw10 rather than dynactin, and this interaction is needed for kinetochore dynein localization. Phosphodynein associates with kinetochores from nuclear envelope breakdown to metaphase, but bioriented microtubule (MT) attachment and chromosome alignment induce IC dephosphorylation. IC dephosphorylation stimulates binding to dynactin and poleward streaming. MT depolymerization, release of kinetochore tension, and a PP1-γ mutant each inhibited IC dephosphorylation, leading to the retention of phosphodynein at kinetochores and reduced poleward streaming. The depletion of kinetochore dynactin by moderate levels of p50(dynamitin) expression disrupted the ability of dynein to remove checkpoint proteins by streaming at metaphase but not other aspects of kinetochore dynein activity. Together, these results suggest a new model for localization of kinetochore dynein and the contribution of kinetochore dynactin.
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Affiliation(s)
- Jacqueline Whyte
- Department of Biological Sciences and 2Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, IN 46556, USA
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42
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Dalal Y, Wang H, Lindsay S, Henikoff S. Tetrameric structure of centromeric nucleosomes in interphase Drosophila cells. PLoS Biol 2008; 5:e218. [PMID: 17676993 PMCID: PMC1933458 DOI: 10.1371/journal.pbio.0050218] [Citation(s) in RCA: 197] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Accepted: 06/12/2007] [Indexed: 01/24/2023] Open
Abstract
Centromeres, the specialized chromatin structures that are responsible for equal segregation of chromosomes at mitosis, are epigenetically maintained by a centromere-specific histone H3 variant (CenH3). However, the mechanistic basis for centromere maintenance is unknown. We investigated biochemical properties of CenH3 nucleosomes from Drosophila melanogaster cells. Cross-linking of CenH3 nucleosomes identifies heterotypic tetramers containing one copy of CenH3, H2A, H2B, and H4 each. Interphase CenH3 particles display a stable association of approximately 120 DNA base pairs. Purified centromeric nucleosomal arrays have typical “beads-on-a-string” appearance by electron microscopy but appear to resist condensation under physiological conditions. Atomic force microscopy reveals that native CenH3-containing nucleosomes are only half as high as canonical octameric nucleosomes are, confirming that the tetrameric structure detected by cross-linking comprises the entire interphase nucleosome particle. This demonstration of stable half-nucleosomes in vivo provides a possible basis for the instability of centromeric nucleosomes that are deposited in euchromatic regions, which might help maintain centromere identity. The octameric structure of eukaryotic nucleosomes is universally accepted as the basic unit of chromatin. This is certainly the case for the vast bulk of nucleosomes; however, there have been no reports of the in vivo structure of nucleosomes associated with centromeres. Though centromeres make up only a minute fraction of the genomic landscape, their role in segregating chromosomes during mitosis is essential for maintaining genomic integrity. We report the characterization of centromeric chromatin from Drosophila cells, using detailed biochemical, electron microscopic, and atomic force microscopic analyses. Surprisingly, we found that, in striking contrast to bulk chromatin, centromeric nucleosomes are stable heterotypic tetramers in vivo, with one copy of CenH3 (the centromere-specific H3 variant), H2A, H2B, and H4 each, wrapping one full turn of DNA at interphase (the cell growth phase of the cell cycle). This results in nucleosome particles that are only half as high as bulk nucleosomes. These unexpected findings can help account for the dynamic behavior of CenH3-containing nucleosomes, whereby they are deposited promiscuously but are turned over in noncentromeric regions. Our demonstration of the existence of stable half-nucleosomes at centromeres suggests a novel mechanism for maintaining centromere identity. The centromeric nucleosomes of Drosophila are histone tetramers rather than the canonical octomer of the rest of chromatin. This unprecedented arrangement of stable half-nucleosomes might help maintain centromere identity.
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Affiliation(s)
- Yamini Dalal
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Seattle, Washington, United States of America
| | - Hongda Wang
- Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
| | - Stuart Lindsay
- Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
| | - Steven Henikoff
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Seattle, Washington, United States of America
- * To whom correspondence should be addressed. E-mail:
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43
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Abstract
The spindle checkpoint blocks cell-cycle progression until chromosomes are properly attached to the mitotic spindle. Popular models propose that checkpoint proteins associate with kinetochores to produce a "wait anaphase" signal that inhibits anaphase. Recent data suggest that a two-state switch results from using the same kinetochore proteins to bind microtubules and checkpoint proteins. At least eight protein kinases are implicated in spindle checkpoint signaling, arguing that a traditional signal transduction cascade is integral to spindle checkpoint signaling.
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Affiliation(s)
- Daniel J Burke
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical Center, 1300 Jefferson Park Avenue, Box 800733, Charlottesville, VA 22908-0733, USA
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44
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Cyclin B1 is localized to unattached kinetochores and contributes to efficient microtubule attachment and proper chromosome alignment during mitosis. Cell Res 2008; 18:268-80. [DOI: 10.1038/cr.2008.11] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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45
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McEwen BF, Renken C, Marko M, Mannella C. Chapter 6 Principles and Practice in Electron Tomography. Methods Cell Biol 2008; 89:129-68. [DOI: 10.1016/s0091-679x(08)00606-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
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46
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Tanaka TU, Stark MJR, Tanaka K. Kinetochore capture and bi-orientation on the mitotic spindle. Nat Rev Mol Cell Biol 2007; 6:929-42. [PMID: 16341079 DOI: 10.1038/nrm1764] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Kinetochores are large protein complexes that are formed on chromosome regions known as centromeres. For high-fidelity chromosome segregation, kinetochores must be correctly captured on the mitotic spindle before anaphase onset. During prometaphase, kinetochores are initially captured by a single microtubule that extends from a spindle pole and are then transported poleward along the microtubule. Subsequently, microtubules that extend from the other spindle pole also interact with kinetochores and, eventually, each sister kinetochore attaches to microtubules that extend from opposite poles - this is known as bi-orientation. Here we discuss the molecular mechanisms of these processes, by focusing on budding yeast and drawing comparisons with other organisms.
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Affiliation(s)
- Tomoyuki U Tanaka
- School of Life Sciences, University of Dundee, Wellcome Trust Biocentre, Dow Street, Dundee, DD1 5EH, UK.
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47
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Dalal Y, Furuyama T, Vermaak D, Henikoff S. Structure, dynamics, and evolution of centromeric nucleosomes. Proc Natl Acad Sci U S A 2007; 104:15974-81. [PMID: 17893333 PMCID: PMC1993840 DOI: 10.1073/pnas.0707648104] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Indexed: 12/18/2022] Open
Abstract
Centromeres are defining features of eukaryotic chromosomes, providing sites of attachment for segregation during mitosis and meiosis. The fundamental unit of centromere structure is the centromeric nucleosome, which differs from the conventional nucleosome by the presence of a centromere-specific histone variant (CenH3) in place of canonical H3. We have shown that the CenH3 nucleosome core found in interphase Drosophila cells is a heterotypic tetramer, a "hemisome" consisting of one molecule each of CenH3, H4, H2A, and H2B, rather than the octamer of canonical histones that is found in bulk nucleosomes. The surprising discovery of hemisomes at centromeres calls for a reevaluation of evidence that has long been interpreted in terms of a more conventional nucleosome. We describe how the hemisome structure of centromeric nucleosomes can account for enigmatic properties of centromeres, including kinetochore accessibility, epigenetic inheritance, rapid turnover of misincorporated CenH3, and transcriptional quiescence of pericentric heterochromatin. Structural differences mediated by loop 1 are proposed to account for the formation of stable tetramers containing CenH3 rather than stable octamers containing H3. Asymmetric CenH3 hemisomes might interrupt the global condensation of octameric H3 arrays and present an asymmetric surface for kinetochore formation. We suggest that this simple mechanism for differentiation between centromeric and packaging nucleosomes evolved from an archaea-like ancestor at the dawn of eukaryotic evolution.
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Affiliation(s)
| | - Takehito Furuyama
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109
| | | | - Steven Henikoff
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109
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48
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Ma N, Matsunaga S, Takata H, Ono-Maniwa R, Uchiyama S, Fukui K. Nucleolin functions in nucleolus formation and chromosome congression. J Cell Sci 2007; 120:2091-105. [PMID: 17535846 DOI: 10.1242/jcs.008771] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
A complex structure, designated the chromosome periphery, surrounds each chromosome during mitosis. Although several proteins have been shown to localize to the chromosome periphery, their functions during mitosis remain unclear. Here, we used a combination of high-resolution microscopy and RNA-interference-mediated depletion to study the functions of nucleolin, a nucleolar protein localized at the chromosome periphery, in interphase and mitosis. During mitosis, nucleolin was localized in the peripheral region including the vicinity of the outer kinetochore of chromosomes. Staining with an antibody specific for nucleolin phosphorylated by CDC2 revealed that nucleolin was also associated with the spindle poles from prometaphase to anaphase. Nucleolin depletion resulted in disorganization of the nucleoli at interphase. Furthermore, nucleolin-depleted cells showed a prolonged cell cycle with misaligned chromosomes and defects in spindle organization. The misaligned chromosomes showed syntelic kinetochore-microtubule attachments with reduced centromere stretching. Taken together, our results indicate that nucleolin is required for nucleolus formation, and is also involved in chromosome congression and spindle formation.
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Affiliation(s)
- Nan Ma
- Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Osaka, Japan
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49
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Dong Y, VandenBeldt KJ, Meng X, Khodjakov A, McEwen BF. The outer plate in vertebrate kinetochores is a flexible network with multiple microtubule interactions. Nat Cell Biol 2007; 9:516-22. [PMID: 17435749 PMCID: PMC2895818 DOI: 10.1038/ncb1576] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Accepted: 03/28/2007] [Indexed: 11/09/2022]
Abstract
Intricate interactions between kinetochores and microtubules are essential for the proper distribution of chromosomes during mitosis. A crucial long-standing question is how vertebrate kinetochores generate chromosome motion while maintaining attachments to the dynamic plus ends of the multiple kinetochore MTs (kMTs) in a kinetochore fibre. Here, we demonstrate that individual kMTs in PtK(1) cells are attached to the kinetochore outer plate by several fibres that either embed the microtubule plus-end tips in a radial mesh, or extend out from the outer plate to bind microtubule walls. The extended fibres also interact with the walls of nearby microtubules that are not part of the kinetochore fibre. These structural data, in combination with other recent reports, support a network model of kMT attachment wherein the fibrous network in the unbound outer plate, including the Hec1-Ndc80 complex, dissociates and rearranges to form kMT attachments.
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Affiliation(s)
- Yimin Dong
- Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, Albany, NY 12201, USA
| | | | - Xing Meng
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Alexey Khodjakov
- Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, Albany, NY 12201, USA
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Bruce F. McEwen
- Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, Albany, NY 12201, USA
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
- Correspondence should be addressed to B.F.M ()
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50
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Schittenhelm RB, Heeger S, Althoff F, Walter A, Heidmann S, Mechtler K, Lehner CF. Spatial organization of a ubiquitous eukaryotic kinetochore protein network in Drosophila chromosomes. Chromosoma 2007; 116:385-402. [PMID: 17333235 PMCID: PMC1950589 DOI: 10.1007/s00412-007-0103-y] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 02/04/2007] [Accepted: 02/05/2007] [Indexed: 01/11/2023]
Abstract
Chromosome segregation during meiosis and mitosis depends on the assembly of functional kinetochores within centromeric regions. Centromeric DNA and kinetochore proteins show surprisingly little sequence conservation despite their fundamental biological role. However, our identification in Drosophila melanogaster of the most diverged orthologs identified so far, which encode components of a kinetochore protein network including the Ndc80 and Mis complexes, further emphasizes the notion of a shared eukaryotic kinetochore design. To determine its spatial organization, we have analyzed by quantitative light microscopy hundreds of native chromosomes from transgenic Drosophila strains coexpressing combinations of red and green fluorescent fusion proteins, fully capable of providing the essential wild-type functions. Thereby, Cenp-A/Cid, Cenp-C, Mis12 and the Ndc80 complex were mapped along the inter sister kinetochore axis with a resolution below 10 nm. The C terminus of Cenp-C was found to be near but well separated from the innermost component Cenp-A/Cid. The N terminus of Cenp-C is further out, clustered with Mis12 and the Spc25 end of the rod-like Ndc80 complex, which is known to bind to microtubules at its other more distal Ndc80/Nuf2 end.
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Affiliation(s)
- Ralf B. Schittenhelm
- Department of Genetics, University of Bayreuth, Universitaetsstr. 30, 95447 Bayreuth, Germany
| | - Sebastian Heeger
- Department of Genetics, University of Bayreuth, Universitaetsstr. 30, 95447 Bayreuth, Germany
| | - Friederike Althoff
- Department of Genetics, University of Bayreuth, Universitaetsstr. 30, 95447 Bayreuth, Germany
| | - Anne Walter
- Department of Genetics, University of Bayreuth, Universitaetsstr. 30, 95447 Bayreuth, Germany
| | - Stefan Heidmann
- Department of Genetics, University of Bayreuth, Universitaetsstr. 30, 95447 Bayreuth, Germany
| | - Karl Mechtler
- Institute of Molecular Biotechnology GmbH, IMBA, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Christian F. Lehner
- Department of Genetics, University of Bayreuth, Universitaetsstr. 30, 95447 Bayreuth, Germany
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