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Hori T, Shang WH, Takeuchi K, Fukagawa T. The CCAN recruits CENP-A to the centromere and forms the structural core for kinetochore assembly. ACTA ACUST UNITED AC 2012; 200:45-60. [PMID: 23277427 PMCID: PMC3542802 DOI: 10.1083/jcb.201210106] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Engineered kinetochores reveal distinct functions of the CCAN in recruiting CENP-A to the centromere and acting as a structural core to directly recruit kinetochore proteins. CENP-A acts as an important epigenetic marker for kinetochore specification. However, the mechanisms by which CENP-A is incorporated into centromeres and the structural basis for kinetochore formation downstream of CENP-A remain unclear. Here, we used a unique chromosome-engineering system in which kinetochore proteins are targeted to a noncentromeric site after the endogenous centromere is conditionally removed. Using this system, we created two distinct types of engineered kinetochores, both of which were stably maintained in chicken DT40 cells. Ectopic targeting of full-length HJURP, CENP-C, CENP-I, or the CENP-C C terminus generated engineered kinetochores containing major kinetochore components, including CENP-A. In contrast, ectopic targeting of the CENP-T or CENP-C N terminus generated functional kinetochores that recruit the microtubule-binding Ndc80 complex and chromosome passenger complex (CPC), but lack CENP-A and most constitutive centromere-associated network (CCAN) proteins. Based on the analysis of these different engineered kinetochores, we conclude that the CCAN has two distinct roles: recruiting CENP-A to establish the kinetochore and serving as a structural core to directly recruit kinetochore proteins.
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Affiliation(s)
- Tetsuya Hori
- Department of Molecular Genetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
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52
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Abstract
The centromere is essential for accurate chromosome segregation during mitosis and meiosis to achieve transmission of genetic information to daughter cells. To facilitate accurate chromosome segregation, the centromere serves several specific functions, including microtubule binding, spindle-checkpoint control, and sister chromatid cohesion. The kinetochore is formed on the centromere to achieve these functions. To understand kinetochore structure and function, it is critical to identify the protein components of the kinetochore and characterize the functional properties of each component. Here, we review recent progress with regard to the molecular architecture of the kinetochore and discuss the future directions for centromere biology.
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53
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Quénet D, Dalal Y. The CENP-A nucleosome: a dynamic structure and role at the centromere. Chromosome Res 2012; 20:465-79. [PMID: 22825424 DOI: 10.1007/s10577-012-9301-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The centromere is a specialized locus that directs the formation of the kinetochore protein complex for correct chromosome segregation. The specific centromere histone H3 variant CENP-A has been described as the epigenetic mark of this chromatin region. Several laboratories have explored its properties, its partners, and its role in centromere formation. Specifically, two types of CENP-A nucleosomes have been described, suggesting there may be more complexity involved in centromere structure than previously thought. Recent work adds to this paradox by questioning the role of CENP-A as a unique centromeric mark and highlighting the assembly of a functional kinetochore in the absence of CENP-A. In this review, we discuss recent literature on the CENP-A nucleosomes and the debate on its role in kinetochore formation and centromere identity.
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Affiliation(s)
- Delphine Quénet
- Laboratory of Receptor Biology & Gene Expression-NCI-NIH, Building 41, Room B901, 41 Library Drive MSC 5055, Bethesda, MD 20892, USA
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54
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Pereira AJ, Maiato H. Maturation of the kinetochore-microtubule interface and the meaning of metaphase. Chromosome Res 2012; 20:563-77. [PMID: 22801775 DOI: 10.1007/s10577-012-9298-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Chromosome positioning at the equator of the mitotic spindle emerges out of a relatively entropic background. At this moment, termed metaphase, all kinetochores have typically captured microtubules leading to satisfaction of the spindle-assembly checkpoint, but the cell does not enter anaphase immediately. The waiting time in metaphase is related to the kinetics of securin and cyclin B1 degradation, which trigger sister-chromatid separation and promote anaphase processivity, respectively. Yet, as judged by metaphase duration, such kinetics vary widely between cell types and organisms, with no evident correlation to ploidy or cell size. During metaphase, many animal and plant spindles are also characterized by a conspicuous "flux" activity characterized by continuous poleward translocation of spindle microtubules, which maintain steady-state length and position. Whether spindle microtubule flux plays a specific role during metaphase remains arguable. Based on known experimental parameters, we have performed a comparative analysis amongst different cell types from different organisms and show that spindle length, metaphase duration and flux velocity combine within each system to obey a quasi-universal rule. As so, knowledge of two of these parameters is enough to estimate the third. This trend indicates that metaphase duration is tuned to allow approximately one kinetochore-to-pole round of microtubule flux. We propose that the time cells spend in metaphase evolved as a quality enhancement step that allows for the uniform stabilization/correction of kinetochore-microtubule attachments, thereby promoting mitotic fidelity.
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Affiliation(s)
- António J Pereira
- Chromosome Instability and Dynamics Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
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55
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Buljan VA, Damian Holsinger RM, Hambly BD, Banati RB, Ivanova EP. Intrinsic microtubule GTP-cap dynamics in semi-confined systems: kinetochore-microtubule interface. J Biol Phys 2012; 39:81-98. [PMID: 23860835 DOI: 10.1007/s10867-012-9287-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 09/07/2012] [Indexed: 11/24/2022] Open
Abstract
In order to quantify the intrinsic dynamics associated with the tip of a GTP-cap under semi-confined conditions, such as those within a neuronal cone and at a kinetochore-microtubule interface, we propose a novel quantitative concept of critical nano local GTP-tubulin concentration (CNLC). A simulation of a rate constant of GTP-tubulin hydrolysis, under varying conditions based on this concept, generates results in the range of 0-420 s(-1). These results are in agreement with published experimental data, validating our model. The major outcome of this model is the prediction of 11 random and distinct outbursts of GTP hydrolysis per single layer of a GTP-cap. GTP hydrolysis is accompanied by an energy release and the formation of discrete expanding zones, built by less-stable, skewed GDP-tubulin subunits. We suggest that the front of these expanding zones within the walls of the microtubule represent soliton-like movements of local deformation triggered by energy released from an outburst of hydrolysis. We propose that these solitons might be helpful in addressing a long-standing question relating to the mechanism underlying how GTP-tubulin hydrolysis controls dynamic instability. This result strongly supports the prediction that large conformational movements in tubulin subunits, termed dynamic transitions, occur as a result of the conversion of chemical energy that is triggered by GTP hydrolysis (Satarić et al., Electromagn Biol Med 24:255-264, 2005). Although simple, the concept of CNLC enables the formulation of a rationale to explain the intrinsic nature of the "push-and-pull" mechanism associated with a kinetochore-microtubule complex. In addition, the capacity of the microtubule wall to produce and mediate localized spatio-temporal excitations, i.e., soliton-like bursts of energy coupled with an abundance of microtubules in dendritic spines supports the hypothesis that microtubule dynamics may underlie neural information processing including neurocomputation (Hameroff, J Biol Phys 36:71-93, 2010; Hameroff, Cognit Sci 31:1035-1045, 2007; Hameroff and Watt, J Theor Biol 98:549-561, 1982).
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Affiliation(s)
- Vlado A Buljan
- Brain and Mind Research Institute, Sydney Medical School, The University of Sydney, Sydney, NSW, 2050, Australia.
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56
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Suijkerbuijk SJE, Vleugel M, Teixeira A, Kops GJPL. Integration of kinase and phosphatase activities by BUBR1 ensures formation of stable kinetochore-microtubule attachments. Dev Cell 2012; 23:745-55. [PMID: 23079597 DOI: 10.1016/j.devcel.2012.09.005] [Citation(s) in RCA: 202] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 08/22/2012] [Accepted: 09/11/2012] [Indexed: 01/16/2023]
Abstract
Maintenance of chromosomal stability depends on error-free chromosome segregation. The pseudokinase BUBR1 is essential for this, because it is a core component of the mitotic checkpoint and is required for formation of stable kinetochore-microtubule attachments. We have identified a conserved and highly phosphorylated domain (KARD) in BUBR1 that is crucial for formation of kinetochore-microtubule attachments. Deletion of this domain or prevention of its phosphorylation abolishes formation of kinetochore microtubules, which can be reverted by inhibiting Aurora B activity. Phosphorylation of KARD by PLK1 promotes direct interaction of BUBR1 with the PP2A-B56α phosphatase that counters excessive Aurora B activity at kinetochores. As a result, removal of BUBR1 from mitotic cells or inhibition of PLK1 reduces PP2A-B56α kinetochore binding and elevates phosphorylation of Aurora B substrates on the outer kinetochore. We propose that PLK1 and BUBR1 cooperate to stabilize kinetochore-microtubule interactions by regulating PP2A-B56α-mediated dephosphorylation of Aurora B substrates at the kinetochore-microtubule interface.
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Affiliation(s)
- Saskia J E Suijkerbuijk
- Molecular Cancer Research and Cancer Genomics Centre, UMC Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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57
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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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58
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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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59
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Abstract
The kinetochore is formed on centromeric DNA as a key interface with microtubules from the mitotic spindle to achieve accurate chromosome segregation during mitosis. However, in contrast to other regions of the chromosome, the position of the kinetochore is specified by sequence-independent epigenetic mechanisms. Most recent work on kinetochore specification has focused on the centromere-specific histone H3-variant CENP-A. Whereas CENP-A is an important epigenetic marker for the kinetochore specification, it is unclear how centromeric chromatin structure is organized. To understand centromeric chromatin structure, we focused on additional centromere proteins that have an intrinsic DNA binding activity and identified the DNA binding CENP-T-W-S-X complex. Tetramer formation of CENP-T-W-S-X is essential for functional kinetochore assembly in vertebrate cells. Our structural and biochemical analysis reveals that the CENP-T-W-S-X complex is composed of four histone-fold domains with structural similarity to nucleosomes and displays DNA supercoiling activity. These results suggest that the CENP-T-W-S-X complex forms a unique nucleosome-like structure at centromeric chromatin. In addition, CENP-S and CENP-X function at non-centromeric sites. The intriguing histone-like properties of these proteins suggest that they may form nucleosome-like structures at various genome loci, extending the chromatin code beyond classical histone variants.
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Affiliation(s)
- Tatsuo Fukagawa
- Department of Molecular Genetics, National Institute of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima, Japan.
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60
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Stellfox ME, Bailey AO, Foltz DR. Putting CENP-A in its place. Cell Mol Life Sci 2012; 70:387-406. [PMID: 22729156 DOI: 10.1007/s00018-012-1048-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 05/15/2012] [Accepted: 06/01/2012] [Indexed: 01/19/2023]
Abstract
The centromere is the chromosomal region that directs kinetochore assembly during mitosis in order to facilitate the faithful segregation of sister chromatids. The location of the human centromere is epigenetically specified. The presence of nucleosomes that contain the histone H3 variant, CENP-A, are thought to be the epigenetic mark that indicates active centromeres. Maintenance of centromeric identity requires the deposition of new CENP-A nucleosomes with each cell cycle. During S-phase, existing CENP-A nucleosomes are divided among the daughter chromosomes, while new CENP-A nucleosomes are deposited during early G1. The specific assembly of CENP-A nucleosomes at centromeres requires the Mis18 complex, which recruits the CENP-A assembly factor, HJURP. We will review the unique features of centromeric chromatin as well as the mechanism of CENP-A nucleosome deposition. We will also highlight a few recent discoveries that begin to elucidate the factors that temporally and spatially control CENP-A deposition.
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Affiliation(s)
- Madison E Stellfox
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical School, PO Box 800733, Charlottesville, VA 22908, USA
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61
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Schleiffer A, Maier M, Litos G, Lampert F, Hornung P, Mechtler K, Westermann S. CENP-T proteins are conserved centromere receptors of the Ndc80 complex. Nat Cell Biol 2012; 14:604-13. [PMID: 22561346 DOI: 10.1038/ncb2493] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 03/30/2012] [Indexed: 12/12/2022]
Abstract
Centromeres direct the assembly of kinetochores, microtubule-attachment sites that allow chromosome segregation on the mitotic spindle. Fundamental differences in size and organization between evolutionarily distant eukaryotic centromeres have in many cases obscured general principles of their function. Here we demonstrate that centromere-binding proteins are highly conserved between budding yeast and humans. We identify the histone-fold protein Cnn1(CENP-T) as a direct centromere receptor of the microtubule-binding Ndc80 complex. The amino terminus of Cnn1 contains a conserved peptide motif that mediates stoichiometric binding to the Spc24-25 domain of the Ndc80 complex. Consistent with the critical role of this interaction, artificial tethering of the Ndc80 complex through Cnn1 allows mini-chromosomes to segregate in the absence of a natural centromere. Our results reveal the molecular function of CENP-T proteins and demonstrate how the Ndc80 complex is anchored to centromeres in a manner that couples chromosome movement to spindle dynamics.
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Affiliation(s)
- Alexander Schleiffer
- IMP/IMBA Bioinformatics Core Facility, Research Institute of Molecular Pathology, Dr. Bohr Gasse 7, 1030 Vienna, Austria
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62
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Nishino T, Takeuchi K, Gascoigne KE, Suzuki A, Hori T, Oyama T, Morikawa K, Cheeseman IM, Fukagawa T. CENP-T-W-S-X forms a unique centromeric chromatin structure with a histone-like fold. Cell 2012; 148:487-501. [PMID: 22304917 DOI: 10.1016/j.cell.2011.11.061] [Citation(s) in RCA: 190] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 08/30/2011] [Accepted: 11/28/2011] [Indexed: 11/26/2022]
Abstract
The multiprotein kinetochore complex must assemble at a specific site on each chromosome to achieve accurate chromosome segregation. Defining the nature of the DNA-protein interactions that specify the position of the kinetochore and provide a scaffold for kinetochore formation remain key goals. Here, we demonstrate that the centromeric histone-fold-containing CENP-T-W and CENP-S-X complexes coassemble to form a stable CENP-T-W-S-X heterotetramer. High-resolution structural analysis of the individual complexes and the heterotetramer reveals similarity to other histone fold-containing complexes including canonical histones within a nucleosome. The CENP-T-W-S-X heterotetramer binds to and supercoils DNA. Mutants designed to compromise heterotetramerization or the DNA-protein contacts around the heterotetramer strongly reduce the DNA binding and supercoiling activities in vitro and compromise kinetochore assembly in vivo. These data suggest that the CENP-T-W-S-X complex forms a unique nucleosome-like structure to generate contacts with DNA, extending the "histone code" beyond canonical nucleosome proteins.
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Affiliation(s)
- Tatsuya Nishino
- Department of Molecular Genetics, National Institute of Genetics and The Graduate University for Advanced Studies (SOKENDAI), Mishima, Shizuoka 411-8540, Japan
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63
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Abstract
The spindle assembly checkpoint controls cell cycle progression during mitosis, synchronizing it with the attachment of chromosomes to spindle microtubules. After the discovery of the mitotic arrest deficient (MAD) and budding uninhibited by benzymidazole (BUB) genes as crucial checkpoint components in 1991, the second decade of checkpoint studies (2001–2010) witnessed crucial advances in the elucidation of the mechanism through which the checkpoint effector, the mitotic checkpoint complex, targets the anaphase-promoting complex (APC/C) to prevent progression into anaphase. Concomitantly, the discovery that the Ndc80 complex and other components of the microtubule-binding interface of kinetochores are essential for the checkpoint response finally asserted that kinetochores are crucial for the checkpoint response. Nevertheless, the relationship between kinetochores and checkpoint control remains poorly understood. Crucial advances in this area in the third decade of checkpoint studies (2011–2020) are likely to be brought about by the characterization of the mechanism of kinetochore recruitment, activation and inactivation of checkpoint proteins, which remains elusive for the majority of checkpoint components. Here, we take a molecular view on the main challenges hampering this task.
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Affiliation(s)
- Andrea Musacchio
- Department of Experimental Oncology, European Institute of Oncology, Via Adamello 16, 20139 Milan, Italy.
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64
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Takeuchi K, Fukagawa T. Molecular architecture of vertebrate kinetochores. Exp Cell Res 2012; 318:1367-74. [PMID: 22391098 DOI: 10.1016/j.yexcr.2012.02.016] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 02/17/2012] [Accepted: 02/20/2012] [Indexed: 11/17/2022]
Abstract
Kinetochores form a dynamic interface with the microtubules from the mitotic spindle to achieve accurate chromosome segregation. Multiple proteins are assembled on centromeric DNA to form the kinetochore structure. Recent insights regarding the mechanism of kinetochore formation in vertebrate cells have come from the identification and characterization of kinetochore proteins using a variety of approaches. Constitutive centromere associated network (CCAN) proteins create a platform for kinetochore formation. Subsequently, CCAN proteins recruit outer kinetochore components such as KNL1, the Mis12 complex and the Ndc80 complex (KMN network) that attach to the spindle microtubules, together comprising the functional kinetochore. In this review, we introduce and discuss putative roles of CCAN and KMN proteins during the process of kinetochore formation.
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Affiliation(s)
- Kozo Takeuchi
- Department of Molecular Genetics, National Institute of Genetics and the Graduate University for Advanced Studies, Mishima, Shizuoka 411-8540, Japan
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65
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Haase J, Stephens A, Verdaasdonk J, Yeh E, Bloom K. Bub1 kinase and Sgo1 modulate pericentric chromatin in response to altered microtubule dynamics. Curr Biol 2012; 22:471-81. [PMID: 22365852 DOI: 10.1016/j.cub.2012.02.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 12/19/2011] [Accepted: 02/03/2012] [Indexed: 01/25/2023]
Abstract
BACKGROUND Tension sensing of bioriented chromosomes is essential for the fidelity of chromosome segregation. The spindle assembly checkpoint (SAC) conveys lack of tension or attachment to the anaphase promoting complex. Components of the SAC (Bub1) phosphorylate histone H2A (S121) and recruit the protector of cohesin, Shugoshin (Sgo1), to the inner centromere. How the chromatin structural modifications of the inner centromere are integrated into the tension sensing mechanisms and the checkpoint are not known. RESULTS We have identified a Bub1/Sgo1-dependent structural change in the geometry and dynamics of kinetochores and the pericentric chromatin upon reduction of microtubule dynamics. The cluster of inner kinetochores contract, whereas the pericentric chromatin and cohesin that encircle spindle microtubules undergo a radial expansion. Despite its increased spatial distribution, the pericentric chromatin is less dynamic. The change in dynamics is due to histone H2A phosphorylation and Sgo1 recruitment to the pericentric chromatin, rather than microtubule dynamics. CONCLUSIONS Bub1 and Sgo1 act as a rheostat to regulate the chromatin spring and maintain force balance. Through histone H2A S121 phosphorylation and recruitment of Sgo1, Bub1 kinase softens the chromatin spring in response to changes in microtubule dynamics. The geometric alteration of all 16 kinetochores and pericentric chromatin reflect global changes in the pericentromeric region and provide mechanisms for mechanically amplifying damage at a single kinetochore microtubule.
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Affiliation(s)
- Julian Haase
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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66
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Abstract
High-speed atomic force microscopy (HS-AFM) is now materialized. It allows direct visualization of dynamic structural changes and dynamic processes of functioning biological molecules in physiological solutions, at high spatiotemporal resolution. Dynamic molecular events unselectively appear in detail in an AFM movie, facilitating our understanding of how biological molecules operate to function. This review describes a historical overview of technical development towards HS-AFM, summarizes elementary devices and techniques used in the current HS-AFM, and then highlights recent imaging studies. Finally, future challenges of HS-AFM studies are briefly discussed.
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Affiliation(s)
- Toshio Ando
- Department of Physics and Bio-AFM Frontier Research Center, Kanazawa University, Kakuma-machi, Kanazawa, Japan
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67
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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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68
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Maddox PS, Corbett KD, Desai A. Structure, assembly and reading of centromeric chromatin. Curr Opin Genet Dev 2011; 22:139-47. [PMID: 22178421 DOI: 10.1016/j.gde.2011.11.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 11/28/2011] [Indexed: 11/28/2022]
Abstract
Centromeres are epigenetically defined chromatin domains marked by the presence of the histone H3 variant CENP-A. Here we review recent structural and biochemical work on CENP-A, and advances in understanding the mechanisms that propagate and read centromeric chromatin domains.
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Affiliation(s)
- Paul S Maddox
- Institute for Research in Immunology and Cancer, Dept of Pathology and Cell Biology, Université de Montréal, Montréal, QC H3C 3J7, Canada.
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69
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Structural organization of the kinetochore-microtubule interface. Curr Opin Cell Biol 2011; 24:48-56. [PMID: 22154944 DOI: 10.1016/j.ceb.2011.11.003] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 11/11/2011] [Indexed: 12/20/2022]
Abstract
Successful mitosis depends on the stable, yet regulated attachment of chromosomes to spindle microtubules. The kinetochore, a large macromolecular structure assembled at sites of centromeric heterochromatin, is responsible for generating and regulating these essential attachments. Over the last several years, concerted experimental efforts have brought the structural view of the kinetochore-microtubule interface more clearly into focus. Here, we review important recent advancements and discuss several unresolved questions regarding how kinetochores dynamically bridge mitotic chromosomes to spindle microtubules.
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70
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Falk SJ, Black BE. Centromeric chromatin and the pathway that drives its propagation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:313-21. [PMID: 22154124 DOI: 10.1016/j.bbagrm.2011.11.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Revised: 11/09/2011] [Accepted: 11/10/2011] [Indexed: 01/03/2023]
Abstract
The centromere is the locus that directs chromosomal inheritance at cell division. While centromeres in diverse eukaryotes are commonly found at sites of repetitive DNA, their location is epigenetically specified. The histone H3 variant CENP-A is the prime candidate for epigenetically marking the centromere, and recent work has uncovered several additional proteins that play key roles in centromere assembly and maintenance. We describe advances in the identification and characterization of proteins that form the centromere, and focus on recent findings that have advanced our understanding of the assembly of functional centromeric chromatin. This article is part of a Special Issue entitled: Histone chaperones and chromatin assembly.
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71
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72
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Visualizing kinetochore architecture. Curr Opin Struct Biol 2011; 21:661-9. [PMID: 21862320 DOI: 10.1016/j.sbi.2011.07.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 07/28/2011] [Accepted: 07/31/2011] [Indexed: 01/03/2023]
Abstract
Kinetochores are large macromolecular assemblies that link chromosomes to spindle microtubules (MTs) during mitosis. Here we review recent advances in the study of core MT-binding kinetochore complexes using electron microcopy methods in vitro and nanometer-accuracy fluorescence microscopy in vivo. We synthesize these findings in novel three-dimensional models of both the budding yeast and vertebrate kinetochore in different stages of mitosis. There is a growing consensus that kinetochores are highly dynamic, supra-molecular machines that undergo dramatic structural rearrangements in response to MT capture and spindle forces during mitosis.
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Perpelescu M, Fukagawa T. The ABCs of CENPs. Chromosoma 2011; 120:425-46. [PMID: 21751032 DOI: 10.1007/s00412-011-0330-0] [Citation(s) in RCA: 151] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 06/28/2011] [Accepted: 06/28/2011] [Indexed: 01/08/2023]
Abstract
Equal distribution of DNA in mitosis requires the assembly of a large proteinaceous ensemble onto the centromeric DNA, called the kinetochore. With few exceptions, kinetochore specification is independent of the DNA sequence and is determined epigenetically by deposition at the centromeric chromatin of special nucleosomes containing an H3-related histone, CENP-A. Onto centromeric CENP-A chromatin is assembled the so-called constitutive centromere-associated network (CCAN) of 16 proteins distributed in several functional groups as follows: CENP-C, CENP-H/CENP-I/CENP-K/, CENP-L/CENP-M/CENP-N, CENP-O/CENP-P/CENP-Q/CENP-R/CENP-U(50), CENP-T/CENP-W, and CENP-S/CENP-X. One role of the CCAN is to recruit outer kinetochore components further, such as KNL1, the Mis12 complex, and the Ndc80 complex (KMN network) to which attach the spindle microtubules with their structural and regulatory proteins. Among the CENPs in CCAN, CENP-C and CENP-T are required in parallel for operational kinetochore specification and spindle attachment. This review presents discussion of the latest structural and functional data on CENP-A and CENPs from the CCAN as well as their interaction with the KMN network.
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Affiliation(s)
- Marinela Perpelescu
- Department of Molecular Genetics, National Institute of Genetics and the Graduate University for Advanced Studies, Mishima, Shizuoka, Japan
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Gascoigne KE, Takeuchi K, Suzuki A, Hori T, Fukagawa T, Cheeseman IM. Induced ectopic kinetochore assembly bypasses the requirement for CENP-A nucleosomes. Cell 2011; 145:410-22. [PMID: 21529714 DOI: 10.1016/j.cell.2011.03.031] [Citation(s) in RCA: 262] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 12/31/2010] [Accepted: 03/17/2011] [Indexed: 12/31/2022]
Abstract
Accurate chromosome segregation requires assembly of the multiprotein kinetochore complex at centromeres. Although prior work identified the centromeric histone H3-variant CENP-A as the important upstream factor necessary for centromere specification, in human cells CENP-A is not sufficient for kinetochore assembly. Here, we demonstrate that two constitutive DNA-binding kinetochore components, CENP-C and CENP-T, function to direct kinetochore formation. Replacing the DNA-binding regions of CENP-C and CENP-T with alternate chromosome-targeting domains recruits these proteins to ectopic loci, resulting in CENP-A-independent kinetochore assembly. These ectopic kinetochore-like foci are functional based on the stoichiometric assembly of multiple kinetochore components, including the microtubule-binding KMN network, the presence of microtubule attachments, the microtubule-sensitive recruitment of the spindle checkpoint protein Mad2, and the segregation behavior of foci-containing chromosomes. We additionally find that CENP-T phosphorylation regulates the mitotic assembly of both endogenous and ectopic kinetochores. Thus, CENP-C and CENP-T form a critical regulated platform for vertebrate kinetochore assembly.
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Affiliation(s)
- Karen E Gascoigne
- Whitehead Institute for Biomedical Research, Department of Biology, Nine Cambridge Center, MA 02142, USA
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Leslie M. Kinetochores feel the pull. J Biophys Biochem Cytol 2011. [PMCID: PMC3082175 DOI: 10.1083/jcb.1931if] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Researchers detail how kinetochores respond to force from spindle.
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