351
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Abstract
Two new studies show that Aurora B kinase corrects improperly attached chromosomes by recruiting molecules necessary for eliminating the bad attachments and by regulating the turnover of the kinetochore fiber.
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Affiliation(s)
- Xin Zhang
- Medical Sciences, Indiana University, 915 E. 3rd Street, Myers Hall 262, Bloomington, Indiana 47405, USA
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352
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Altieri DC. The case for survivin as a regulator of microtubule dynamics and cell-death decisions. Curr Opin Cell Biol 2006; 18:609-15. [PMID: 16934447 DOI: 10.1016/j.ceb.2006.08.015] [Citation(s) in RCA: 220] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2006] [Accepted: 08/03/2006] [Indexed: 01/08/2023]
Abstract
Survivin has aroused keen interest in disparate areas of basic and translational research. This stems from the complexity of a 'survivin network', which appears to intersect multiple pathways of cell division, resistance to apoptosis, surveillance checkpoints and adaptation to unfavorable environments. Such intricacy has also engendered different models for survivin function and its implications. As antagonists of survivin are being evaluated in the clinic, a critical reassessment of the pathway, especially with respect to cell division and cell survival, is now a priority. Building a unifying model to reconcile the differing views on survivin will aid in the design and interpretation of molecularly based clinical trials targeting this network in humans.
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Affiliation(s)
- Dario C Altieri
- Department of Cancer Biology and Cancer Center, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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353
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Nguyen HG, Ravid K. Tetraploidy/aneuploidy and stem cells in cancer promotion: The role of chromosome passenger proteins. J Cell Physiol 2006; 208:12-22. [PMID: 16331679 DOI: 10.1002/jcp.20565] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
While polyploidy, a state of having fully duplicated sets of chromosomes per cell, has been described in normally developing bone marrow megakaryocytes or as an adaptive response in other cell types, aneuploidy is never detected in normal cells. Tetraploidy or aneuploidy can be induced by several signals and it is highly prevalent in different forms of cancers, suggesting a role for this cell cycle state in promoting cellular transformation. Investigations suggested that loss of heterozygosity of cancer-related genes in stem cells might contribute to genetic instability in progeny cells and to subsequent cancer development. Deregulated expression of chromosome passenger proteins, such as Aurora kinases or Survivin, is a hallmark of various cancers, and experimentally induced changes in these regulators can promote tetraploidy or aneuploidy and loss of heterozygosity. Our studies described an induction of tetraploidy/aneuploidy by a stable form of Aurora-B, leading to acquisition of transformation properties. It is intriguing to speculate that in some cancers, tetraploidy/aneuploidy induced by deregulated expression of a mitotic regulator represents a primary event that leads to unbalanced expression of a cluster of crucial genes and to cellular transformation.
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Affiliation(s)
- Hao G Nguyen
- Department of Biochemistry and Medicine, Cancer Center, Boston University School of Medicine, Boston, Massachusetts, USA
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354
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Parra MT, Gómez R, Viera A, Page J, Calvente A, Wordeman L, Rufas JS, Suja JA. A perikinetochoric ring defined by MCAK and Aurora-B as a novel centromere domain. PLoS Genet 2006; 2:e84. [PMID: 16741559 PMCID: PMC1472701 DOI: 10.1371/journal.pgen.0020084] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Accepted: 04/20/2006] [Indexed: 11/18/2022] Open
Abstract
Mitotic Centromere-Associated Kinesin (MCAK) is a member of the kinesin-13 subfamily of kinesin-related proteins. In mitosis, this microtubule-depolymerising kinesin seems to be implicated in chromosome segregation and in the correction of improper kinetochore-microtubule interactions, and its activity is regulated by the Aurora-B kinase. However, there are no published data on its behaviour and function during mammalian meiosis. We have analysed by immunofluorescence in squashed mouse spermatocytes, the distribution and possible function of MCAK, together with Aurora-B, during both meiotic divisions. Our results demonstrate that MCAK and Aurora-B colocalise at the inner domain of metaphase I centromeres. Thus, MCAK shows a “cone”-like three-dimensional distribution beneath and surrounding the closely associated sister kinetochores. During the second meiotic division, MCAK and Aurora-B also colocalise at the inner centromere domain as a band that joins sister kinetochores, but only during prometaphase II in unattached chromosomes. During chromosome congression to the metaphase II plate, MCAK relocalises and appears as a ring below each sister kinetochore. Aurora-B also relocalises to appear as a ring surrounding and beneath kinetochores but during late metaphase II. Our results demonstrate that the redistribution of MCAK at prometaphase II/metaphase II centromeres depends on tension across the centromere and/or on the interaction of microtubules with kinetochores. We propose that the perikinetochoric rings of MCAK and Aurora-B define a novel transient centromere domain at least in mouse chromosomes during meiosis. We discuss the possible functions of MCAK at the inner centromere domain and at the perikinetochoric ring during both meiotic divisions. The centromere is a chromosome domain essential for the correct partitioning of chromosomes during mitotic and meiotic cell divisions. MCAK is a centromeric protein that depolymerises microtubules, and seems to be implicated in chromosome segregation, and in the correction of improper microtubule interactions with the chromosome. However, there are no published data on its behaviour and function during meiotic divisions. Here, Parra et al. analyse the pattern of distribution of MCAK during male mouse meiosis in relation to Aurora-B, a kinase that regulates its activity. They show that MCAK and Aurora-B appear at the inner domain of metaphase I bivalents and unaligned metaphase II chromosomes. Most importantly, the authors discovered that these proteins relocalise to a novel perikinetochoric ring in aligned metaphase II chromosomes. The discovery of this novel structure adds a new dimension to the understanding of kinetochore structure and biology. The authors propose that, at least for mouse centromeres, the perikinetochoric ring represents a transient centromere domain whose appearance depends on tension across centromeres once microtubules interact with both sister kinetochores. This study shows that the analysis of the behaviour of different centromere proteins during meiosis can offer new insights concerning the centromere functionality.
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Affiliation(s)
- María Teresa Parra
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain.
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355
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Klein UR, Nigg EA, Gruneberg U. Centromere targeting of the chromosomal passenger complex requires a ternary subcomplex of Borealin, Survivin, and the N-terminal domain of INCENP. Mol Biol Cell 2006; 17:2547-58. [PMID: 16571674 PMCID: PMC1474794 DOI: 10.1091/mbc.e05-12-1133] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The chromosomal passenger complex (CPC), consisting of the serine/threonine kinase Aurora B, the inner centromere protein INCENP, Survivin, and Borealin/DasraB, has essential functions at the centromere in ensuring correct chromosome alignment and segregation. Despite observations that small interfering RNA-mediated knockdown of any one member of the CPC abolishes localization of the other subunits, it remains unclear how the complex is targeted to the centromere. We have now identified a ternary subcomplex of the CPC comprising Survivin, Borealin, and the N-terminal 58 amino acids of INCENP in vitro and in vivo. This subcomplex was found to be essential and sufficient for targeting to the centromere. Notably, Aurora B kinase, the enzymatic core of the CPC, was not required for centromere localization of the subcomplex. We demonstrate that CPC targeting to the centromere does not depend on CENP-A and hMis12, two core components for kinetochore/centromere assembly, and provide evidence that the CPC may be directed to centromeric DNA directly via the Borealin subunit. Our findings thus establish a functional module within the CPC that assembles on the N terminus of INCENP and controls centromere recruitment.
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Affiliation(s)
- Ulf R. Klein
- Department of Cell Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Erich A. Nigg
- Department of Cell Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Ulrike Gruneberg
- Department of Cell Biology, Max-Planck Institute of Biochemistry, 82152 Martinsried, Germany
- Address correspondence to: Ulrike Gruneberg (
)
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356
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Gadea BB, Ruderman JV. Aurora B is required for mitotic chromatin-induced phosphorylation of Op18/Stathmin. Proc Natl Acad Sci U S A 2006; 103:4493-8. [PMID: 16537398 PMCID: PMC1401233 DOI: 10.1073/pnas.0600702103] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Oncoprotein 18/Stathmin (Op18) is a microtubule-destabilizing protein that is inhibited by phosphorylation in response to many types of signals. During mitosis, phosphorylation of Op18 by cdc2 is necessary but not sufficient for Op18 inhibition. The presence of mitotic chromosomes is additionally required and involves phosphorylation of Ser-16 in Xenopus Op18 (and/or Ser-63 in human). Given that Ser-16 is an excellent Aurora A (Aur-A) kinase consensus phosphorylation site and the Aurora kinase inhibitor ZM447439 (ZM) blocks phosphorylation in the activation loop of Aur-A, we asked whether either Aur-A or Aurora B (Aur-B) might regulate Op18. We find that ZM blocks the ability of mitotic chromatin to induce Op18 hyperphosphorylation in Xenopus egg extracts. Depletion of Aur-B, but not Aur-A, blocks hyperphosphorylation of Op18, and chromatin assembled in the absence of Aur-B fails to induce hyperphosphorylation. These results suggest that Aur-B, which concentrates at centromeres of metaphase chromosomes, contributes to localized regulation of Op18 during the process of spindle assembly.
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Affiliation(s)
- Bedrick B. Gadea
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Joan V. Ruderman
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
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357
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Civelekoglu-Scholey G, Sharp DJ, Mogilner A, Scholey JM. Model of chromosome motility in Drosophila embryos: adaptation of a general mechanism for rapid mitosis. Biophys J 2006; 90:3966-82. [PMID: 16533843 PMCID: PMC1459506 DOI: 10.1529/biophysj.105.078691] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During mitosis, ensembles of dynamic MTs and motors exert forces that coordinate chromosome segregation. Typically, chromosomes align at the metaphase spindle equator where they oscillate along the pole-pole axis before disjoining and moving poleward during anaphase A, but spindles in different cell types display differences in MT dynamicity, in the amplitude of chromosome oscillations and in rates of chromatid-to-pole motion. Drosophila embryonic mitotic spindles, for example, display remarkably dynamic MTs, barely detectable metaphase chromosome oscillations, and a rapid rate of "flux-pacman-dependent" anaphase chromatid-to-pole motility. Here we develop a force-balance model that describes Drosophila embryo chromosome motility in terms of a balance of forces acting on kinetochores and kMTs that is generated by multiple polymer ratchets and mitotic motors coupled to tension-dependent kMT dynamics. The model shows that i), multiple MTs displaying high dynamic instability can drive steady and rapid chromosome motion; ii), chromosome motility during metaphase and anaphase A can be described by a single mechanism; iii), high kinetochore dynein activity is deployed to dampen metaphase oscillations, to augment the basic flux-pacman mechanism, and to drive rapid anaphase A; iv), modulation of the MT rescue frequency by the kinetochore-associated kinesin-13 depolymerase promotes metaphase chromosome oscillations; and v), this basic mechanism can be adapted to a broad range of spindles.
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Affiliation(s)
- G Civelekoglu-Scholey
- Laboratory of Cell and Computational Biology, Center for Genetics and Development, University of California-Davis, 1 Shields Avenue, Davis, CA 95616, USA
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358
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Tang CJC, Lin CY, Tang TK. Dynamic localization and functional implications of Aurora-C kinase during male mouse meiosis. Dev Biol 2006; 290:398-410. [PMID: 16386730 DOI: 10.1016/j.ydbio.2005.11.036] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 10/19/2005] [Accepted: 11/18/2005] [Indexed: 11/21/2022]
Abstract
Aurora-C was first identified during screening for kinases expressed in mouse sperm and eggs. Herein, we report for the first time the precise subcellular localization of endogenous Aurora-C during male meiotic division. The localization of Aurora-C was analyzed by immunofluorescence staining on chromosome spreads of mouse spermatocytes or in squashed seminiferous tubules. Aurora-C was first detected at clusters of chromocenters in diplotene spermatocytes and was concentrated at centromeres in metaphase I and II. Interestingly, Aurora-C was also found along the chromosome axes, including both the regions of centromeres and the chromosome arms in diakinesis. During the anaphase I/telophase I and anaphase II/telophase II transitions, Aurora-C was relocalized to the spindle midzone and midbody. A similar distribution pattern was also observed for Aurora-B during male meiotic divisions. Surprisingly, we detected no Aurora-C in mitotic spermatogonia. Furthermore, immunoprecipitation analyses revealed that INCENP associated with Aurora-C in the male testis. We propose that INCENP recruits Aurora-C (or some other factor(s) recruit INCENP and Aurora-C) to meiotic chromosomes, while Aurora-C may either work alone or cooperate with Aurora-B to regulate chromosome segregation during male meiosis.
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Affiliation(s)
- Chieh-Ju C Tang
- Institute of Biomedical Sciences, Academia Sinica, 128 Yen-Chiu-Yuan Rd., Sec. 2, Taipei 11529, Taiwan
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359
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Kinoshita K, Noetzel TL, Arnal I, Drechsel DN, Hyman AA. Global and local control of microtubule destabilization promoted by a catastrophe kinesin MCAK/XKCM1. J Muscle Res Cell Motil 2006; 27:107-14. [PMID: 16450057 DOI: 10.1007/s10974-005-9045-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Accepted: 10/26/2005] [Indexed: 12/14/2022]
Abstract
Traditionally, kinesins have been identified as proteins that use the energy of ATP to translocate along microtubules. However, in the last decade some kinesin-like proteins were found to destabilize microtubule ends. The kinesins that destabilize microtubules are known as "catastrophe kinesins". Analyses of a Xenopus member of the catastrophe kinesins called MCAK/XKCM1 have shown that, in fact, catastrophe kinesins are essential for controlling the distribution of microtubules by inducing their depolymerization. Therefore, unraveling the mechanisms of how microtubule destabilization promoted by these catastrophe kinesins is controlled is essential for understanding how microtubules in a cell are distributed. Here we give an overview of the studies that have focused on the global and local control of microtubule destabilization promoted by MCAK/XKCM1.
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Affiliation(s)
- Kazuhisa Kinoshita
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Pfotenhauerstrasse 108, 01307, Dresden, Germany.
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360
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Hoffmann I. Protein kinases involved in mitotic spindle checkpoint regulation. Results Probl Cell Differ 2006; 42:93-109. [PMID: 16903209 DOI: 10.1007/b138827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A number of checkpoint controls function to preserve the genome by restraining cell cycle progression until prerequisite events have been properly completed. Chromosome attachment to the mitotic spindle is monitored by the spindle assembly checkpoint. Sister chromatid separation in anaphase is initiated only once all chromosomes have been attached to both poles of the spindle. Premature separation of sister chromatids leads to the loss or gain of chromosomes in daughter cells (aneuploidy), a prevalent form of genetic instability of human cancer. The spindle assembly checkpoint ensures that cells with misaligned chromosomes do not exit mitosis and divide to form aneuploid cells. A number of protein kinases and checkpoint phosphoproteins are required for the function of the spindle assembly checkpoint. This review discusses the recent progress in understanding the role of protein kinases of the mitotic checkpoint complex in the surveillance pathway of the checkpoint.
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Affiliation(s)
- Ingrid Hoffmann
- Cell Cycle Control and Carcinogenesis, German Cancer Research Center, Heidelberg.
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361
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Cimini D, Degrassi F. Aneuploidy: a matter of bad connections. Trends Cell Biol 2005; 15:442-51. [PMID: 16023855 DOI: 10.1016/j.tcb.2005.06.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/06/2005] [Accepted: 06/29/2005] [Indexed: 11/20/2022]
Abstract
Proper chromosome segregation is required to maintain the appropriate number of chromosomes from one cell generation to the next and to prevent aneuploidy, the condition in which a cell has gained or lost one or several chromosomes during cell division. Aneuploidy is a hallmark associated with birth defects and cancer, and is observed at relatively high frequencies in human somatic cells. Recent studies in mammalian tissue culture cells suggest that the persistence of kinetochore-microtubule misattachments through mitosis is a major cause of chromosome mis-segregation and aneuploidy. Furthermore, studies in mice and humans suggest that small changes in the expression, rather than complete inactivation, of genes encoding specific proteins might be associated with aneuploidy in living organisms. In this article (which is part of the Chromosome Segregation and Aneuploidy series), we survey the outcome of these studies, focusing on the importance of kinetochore misattachments in producing aneuploid cells.
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Affiliation(s)
- Daniela Cimini
- Department of Biology, University of North Carolina at Chapel Hill, 607 Fordham Hall, Chapel Hill, NC 27599, USA
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362
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Chen Q, Li H, De Lozanne A. Contractile ring-independent localization of DdINCENP, a protein important for spindle stability and cytokinesis. Mol Biol Cell 2005; 17:779-88. [PMID: 16339076 PMCID: PMC1356588 DOI: 10.1091/mbc.e05-08-0704] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Dictyostelium DdINCENP is a chromosomal passenger protein associated with centromeres, the spindle midzone, and poles during mitosis and the cleavage furrow during cytokinesis. Disruption of the single DdINCENP gene revealed important roles for this protein in mitosis and cytokinesis. DdINCENP null cells lack a robust spindle midzone and are hypersensitive to microtubule-depolymerizing drugs, suggesting that their spindles may not be stable. Furthermore DdCP224, a protein homologous to the microtubule-stabilizing protein TOGp/XMAP215, was absent from the spindle midzone of DdINCENP null cells. Overexpression of DdCP224 rescued the weak spindle midzone defect of DdINCENP null cells. Although not required for the localization of the myosin II contractile ring and subsequent formation of a cleavage furrow, DdINCENP is important for the abscission of daughter cells at the end of cytokinesis. Finally, we show that the localization of DdINCENP at the cleavage furrow is modulated by myosin II but it occurs by a mechanism different from that controlling the formation of the contractile ring.
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Affiliation(s)
- Qian Chen
- Institute of Cellular and Molecular Biology and Department of Molecular, Cellular, and Developmental Biology, University of Texas at Austin, Austin, TX 78712, USA
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363
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Vong QP, Cao K, Li HY, Iglesias PA, Zheng Y. Chromosome alignment and segregation regulated by ubiquitination of survivin. Science 2005; 310:1499-504. [PMID: 16322459 DOI: 10.1126/science.1120160] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Proper chromosome segregation requires the attachment of sister kinetochores to microtubules from opposite spindle poles to form bi-oriented chromosomes on the metaphase spindle. The chromosome passenger complex containing Survivin and the kinase Aurora B regulates this process from the centromeres. We report that a de-ubiquitinating enzyme, hFAM, regulates chromosome alignment and segregation by controlling both the dynamic association of Survivin with centromeres and the proper targeting of Survivin and Aurora B to centromeres. Survivin is ubiquitinated in mitosis through both Lys(48) and Lys(63) ubiquitin linkages. Lys(63) de-ubiquitination mediated by hFAM is required for the dissociation of Survivin from centromeres, whereas Lys(63) ubiquitination mediated by the ubiquitin binding protein Ufd1 is required for the association of Survivin with centromeres. Thus, ubiquitinaton regulates dynamic protein-protein interactions and chromosome segregation independently of protein degradation.
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Affiliation(s)
- Queenie P Vong
- Department of Embryology, Carnegie Institution of Washington and Howard Hughes Medical Institute, 3520 San Martin Drive, Baltimore, MD 21218, USA
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364
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Kanda A, Kawai H, Suto S, Kitajima S, Sato S, Takata T, Tatsuka M. Aurora-B/AIM-1 kinase activity is involved in Ras-mediated cell transformation. Oncogene 2005; 24:7266-72. [PMID: 16027732 DOI: 10.1038/sj.onc.1208884] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Aurora-B, previously known as AIM-1, is a conserved eukaryotic mitotic protein kinase. In mammals, this kinase plays an essential role in chromosomal segregation processes, including chromosome condensation, alignment, control of spindle checkpoints, chromosome segregation, and cytokinesis. Aurora-B is overexpressed in various cancer cells, suggesting that the kinase activity perturbs chromosomal segregation processes. Its forced overexpression induces chromosomal number instability and progressive tumorigenicity in rodent cells in vitro and in vivo. Nevertheless, based on focus formation in BALB/c 3T3 A31-1-1 cells, Aurora-B is not oncogenic. Here, we show that Aurora-B kinase activity augments Ras-mediated cell transformation. RNA interference with short hairpin RNA inhibits transformation by Ras and its upstream oncogene Src, but not by the downstream oncogene Raf. In addition, the inner centromere protein, which is a passenger protein associated with Aurora-B, has a similar ability to potentiate the activity of oncogenic Ras. These data indicate that elevated Aurora-B activity promotes transformation by oncogenic Ras by enhancing oncogenic signaling and by converting chromosome number-stable cells to aneuploid cells.
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Affiliation(s)
- Akifumi Kanda
- Department of Molecular Radiobiology, Division of Genome Biology, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734, Japan
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365
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Spence JM, Mills W, Mann K, Huxley C, Farr CJ. Increased missegregation and chromosome loss with decreasing chromosome size in vertebrate cells. Chromosoma 2005; 115:60-74. [PMID: 16267674 DOI: 10.1007/s00412-005-0032-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2005] [Revised: 09/01/2005] [Accepted: 09/19/2005] [Indexed: 11/24/2022]
Abstract
Chromosome engineering has allowed the generation of an extensive and well-defined series of linear human X centromere-based minichromosomes, which has been used to investigate the influence of size and structure on chromosome segregation in vertebrate cells. A clear relationship between overall chromosome size and mitotic stability was detected, with decreasing size associated with increasing loss rates. In chicken DT40, the lower size limit for prolonged mitotic stability is approximately 550 kb: at 450 kb, there was a dramatic increase in chromosome loss, while structures of approximately 200 kb could not be recovered. In human HT1080 cells, the size threshold for mitotic stability is approximately 1.6 Mb. Minichromosomes of 0.55-1.0 Mb can be recovered, but display high loss rates. However, all minichromosomes examined exhibited more segregation errors than normal chromosomes in HT1080 cells. This error rate increases with decreased size and correlates with reduced levels of CENP-A and Aurora B. In mouse LA-9 and Indian muntjac FM7 cells, the size requirements for mitotic stability are much greater. In mouse, a human 2.7-Mb minichromosome is rarely able to propagate a kinetochore and behaves acentrically. In Indian muntjac, CENP-C associates with the human minichromosome, but the mitotic apparatus appears unable to handle its segregation.
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366
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Giet R, Petretti C, Prigent C. Aurora kinases, aneuploidy and cancer, a coincidence or a real link? Trends Cell Biol 2005; 15:241-50. [PMID: 15866028 DOI: 10.1016/j.tcb.2005.03.004] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
As Aurora kinases are overexpressed in a large number of cancers, and ectopic expression of Aurora generates polyploid cells containing multiple centrosomes, it has been tempting to suggest that Aurora overexpression provokes genetic instability underlying the tumorigenesis. However, examination of the evidence suggests a more complex relationship. Overexpression of Aurora-A readily transforms rat-1 and NIH3T3 cells, but not primary cells, whereas overexpression of Aurora-B induces metastasis after implantation of tumors in nude mice. Why do polyploid cells containing abnormal centrosome numbers induced by Aurora not get eliminated at cell-cycle checkpoints? Does this phenotype determine the origin of cancer or does it only promote tumor progression? Would drugs against Aurora family members be of any help for cancer treatment? These and related questions are addressed in this review (which is part of the Chromosome Segregation and Aneuploidy series).
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Affiliation(s)
- Régis Giet
- CNRS UMR6061 Université de Rennes 1, Groupe Cycle Cellulaire, Equipe Labellisée LNCC, Université de Rennes 1, IFR140 GFAS, Faculté de Médecine, 2 Avenue du Pr Léon Bernard, CS 3417, Rennes cedex, France
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367
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Morrow CJ, Tighe A, Johnson VL, Scott MIF, Ditchfield C, Taylor SS. Bub1 and aurora B cooperate to maintain BubR1-mediated inhibition of APC/CCdc20. J Cell Sci 2005; 118:3639-52. [PMID: 16046481 DOI: 10.1242/jcs.02487] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The spindle checkpoint maintains genome stability by inhibiting Cdc20-mediated activation of the anaphase promoting complex/cyclosome (APC/C) until all the chromosomes correctly align on the microtubule spindle apparatus via their kinetochores. BubR1, an essential component of this checkpoint, localises to kinetochores and its kinase activity is regulated by the kinesin-related motor protein Cenp-E. BubR1 also inhibits APC/CCdc20 in vitro, thus providing a molecular link between kinetochore-microtubule interactions and the proteolytic machinery that regulates mitotic progression. Several other protein kinases, including Bub1 and members of the Ipl1/aurora family, also regulate anaphase onset. However, in human somatic cells Bub1 and aurora B kinase activity do not appear to be essential for spindle checkpoint function. Specifically, when Bub1 is inhibited by RNA interference, or aurora kinase activity is inhibited with the small molecule ZM447439, cells arrest transiently in mitosis following exposure to spindle toxins that prevent microtubule polymerisation. Here, we show that mitotic arrest of Bub1-deficient cells is dependent on aurora kinase activity, and vice versa. We suggest therefore that the checkpoint is composed of two arms, one dependent on Bub1, the other on aurora B. Analysis of BubR1 complexes suggests that both of these arms converge on the mitotic checkpoint complex (MCC), which includes BubR1, Bub3, Mad2 and Cdc20. Although it is known that MCC components can bind and inhibit the APC/C, we show here for the first time that the binding of the MCC to the APC/C is dependent on an active checkpoint signal. Furthermore, we show that both Bub1 and aurora kinase activity are required to promote binding of the MCC to the APC/C. These observations provide a simple explanation of why BubR1 and Mad2 are essential for checkpoint function following spindle destruction, yet Bub1 and aurora B kinase activity are not. Taken together with other observations, we suggest that these two arms respond to different spindle cues: whereas the Bub1 arm monitors kinetochore-microtubule attachment, the aurora B arm monitors biorientation. This bifurcation in the signalling mechanism may help explain why many tumour cells mount a robust checkpoint response following spindle damage, despite exhibiting chromosome instability.
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Affiliation(s)
- Christopher J Morrow
- Faculty of Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
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368
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Moore AT, Rankin KE, von Dassow G, Peris L, Wagenbach M, Ovechkina Y, Andrieux A, Job D, Wordeman L. MCAK associates with the tips of polymerizing microtubules. ACTA ACUST UNITED AC 2005; 169:391-7. [PMID: 15883193 PMCID: PMC2171944 DOI: 10.1083/jcb.200411089] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
MCAK is a member of the kinesin-13 family of microtubule (MT)-depolymerizing kinesins. We show that the potent MT depolymerizer MCAK tracks (treadmills) with the tips of polymerizing MTs in living cells. Tip tracking of MCAK is inhibited by phosphorylation and is dependent on the extreme COOH-terminal tail of MCAK. Tip tracking is not essential for MCAK's MT-depolymerizing activity. We propose that tip tracking is a mechanism by which MCAK is preferentially localized to regions of the cell that modulate the plus ends of MTs.
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Affiliation(s)
- Ayana T Moore
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
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369
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Sanchez-Perez I, Renwick SJ, Crawley K, Karig I, Buck V, Meadows JC, Franco-Sanchez A, Fleig U, Toda T, Millar JBA. The DASH complex and Klp5/Klp6 kinesin coordinate bipolar chromosome attachment in fission yeast. EMBO J 2005; 24:2931-43. [PMID: 16079915 PMCID: PMC1187944 DOI: 10.1038/sj.emboj.7600761] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Accepted: 07/11/2005] [Indexed: 11/08/2022] Open
Abstract
We identified a truncated allele of dam1 as a multicopy suppressor of the sensitivity of cdc13-117 (cyclin B) and mal3-1 (EB-1) cells to thiabendazole, a microtubule poison. We find that Dam1 binds to the plus end of spindle microtubules and kinetochores as cells enter mitosis and this is dependent on other components of the fission yeast DASH complex, including Ask1, Duo1, Spc34 and Dad1. By contrast, Dad1 remains bound to kinetochores throughout the cell cycle and its association is dependent on the Mis6 and Mal2, but not Mis12, Nuf2 or Cnp1, kinetochore proteins. In cells lacking Dam1, or other components of the DASH complex, anaphase is delayed due to activation of the spindle assembly checkpoint and lagging sister chromatids are frequently observed and occasionally sister chromatid pairs segregate to the same spindle pole. We find that the mitotic centromere-associated Klp5/Klp6 kinesin complex is essential in cells lacking components of the DASH complex. Cells lacking both Dam1 and Klp5 undergo a first cell cycle arrest in mitosis due to a failure to establish bipolar chromosome attachment.
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Affiliation(s)
| | - Steven J Renwick
- Division of Yeast Genetics, National Institute for Medical Research, London, UK
| | - Karen Crawley
- Laboratory of Cell Regulation, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, London, UK
| | - Inga Karig
- Institut für Mikrobiologie, Heinrich-Heine-Universitat Düsseldorf, Düsseldorf, Germany
| | - Vicky Buck
- Division of Yeast Genetics, National Institute for Medical Research, London, UK
| | - John C Meadows
- Division of Yeast Genetics, National Institute for Medical Research, London, UK
| | | | - Ursula Fleig
- Institut für Mikrobiologie, Heinrich-Heine-Universitat Düsseldorf, Düsseldorf, Germany
| | - Takashi Toda
- Laboratory of Cell Regulation, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, London, UK
| | - Jonathan B A Millar
- Division of Yeast Genetics, National Institute for Medical Research, London, UK
- Division of Yeast Genetics, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK. Tel.: +44 208 816 2367; Fax: +44 208 816 2523; E-mail:
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370
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Srayko M, Kaya A, Stamford J, Hyman AA. Identification and Characterization of Factors Required for Microtubule Growth and Nucleation in the Early C. elegans Embryo. Dev Cell 2005; 9:223-36. [PMID: 16054029 DOI: 10.1016/j.devcel.2005.07.003] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Revised: 06/10/2005] [Accepted: 07/08/2005] [Indexed: 11/19/2022]
Abstract
Microtubules (MTs) are dynamic polymers that undergo cell cycle and position-sensitive regulation of polymerization and depolymerization. Although many different factors that regulate MT dynamics have been described, to date there has been no systematic analysis of genes required for MT dynamics in a single system. Here, we use a transgenic EB1::GFP strain, which labels the growing plus ends of MTs, to analyze the growth rate, nucleation rate, and distribution of growing MTs in the Caenorhabditis elegans embryo. We also present the results from an RNAi screen of 40 genes previously implicated in MT-based processes. Our findings suggest that fast microtubule growth is dependent on the amount of free tubulin and the ZYG-9-TAC-1 complex. Robust MT nucleation by centrosomes requires AIR-1, SPD-2, SPD-5, and gamma-tubulin. However, we found that centrosomes do not nucleate MTs to saturation; rather, the depolymerizing kinesin-13 subfamily member KLP-7 is required to limit microtubule outgrowth from centrosomes.
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Affiliation(s)
- Martin Srayko
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307 Dresden, Germany.
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371
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Abstract
The Aurora kinases have been implicated in tumorigenesis and are important regulators of diverse cell cycle events, ranging from the entry into mitosis, centrosome function, mitotic spindle formation, chromosome biorientation and segregation, and cytokinesis. The recent identification of novel binding partners and key downstream effectors, together with new small-molecule inhibitors that display efficacy against tumours, heralds an upsurge of interest in these critical kinases. This review details new developments in the field and analyses the potential of Aurora kinases as anticancer targets.
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Affiliation(s)
- Paul D Andrews
- Division of Gene Regulation and Expression, Wellcome Trust Biocentre, University of Dundee, Dundee, DD1 5EH, UK.
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372
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Green RA, Wollman R, Kaplan KB. APC and EB1 function together in mitosis to regulate spindle dynamics and chromosome alignment. Mol Biol Cell 2005; 16:4609-22. [PMID: 16030254 PMCID: PMC1237068 DOI: 10.1091/mbc.e05-03-0259] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Recently, we have shown that a cancer causing truncation in adenomatous polyposis coli (APC) (APC(1-1450)) dominantly interferes with mitotic spindle function, suggesting APC regulates microtubule dynamics during mitosis. Here, we examine the possibility that APC mutants interfere with the function of EB1, a plus-end microtubule-binding protein that interacts with APC and is required for normal microtubule dynamics. We show that siRNA-mediated inhibition of APC, EB1, or APC and EB1 together give rise to similar defects in mitotic spindles and chromosome alignment without arresting cells in mitosis; in contrast inhibition of CLIP170 or LIS1 cause distinct spindle defects and mitotic arrest. We show that APC(1-1450) acts as a dominant negative by forming a hetero-oligomer with the full-length APC and preventing it from interacting with EB1, which is consistent with a functional relationship between APC and EB1. Live-imaging of mitotic cells expressing EB1-GFP demonstrates that APC(1-1450) compromises the dynamics of EB1-comets, increasing the frequency of EB1-GFP pausing. Together these data provide novel insight into how APC may regulate mitotic spindle function and how errors in chromosome segregation are tolerated in tumor cells.
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Affiliation(s)
- Rebecca A Green
- Section of Molecular and Cellular Biology, University of California-Davis, Davis, CA 95616, USA
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373
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Craig JM, Choo KHA. Kiss and break up—a safe passage to anaphase in mitosis and meiosis. Chromosoma 2005; 114:252-62. [PMID: 16012859 DOI: 10.1007/s00412-005-0010-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Revised: 05/20/2005] [Accepted: 05/24/2005] [Indexed: 01/15/2023]
Abstract
Eukaryotic chromosomes have many challenges to overcome between DNA replication and sister chromatid segregation. If these challenges are not met, cell death or unregulated cell division (cancer) may result. During prophase, chromosomes condense, the nuclear membrane breaks down and cohesins are removed from chromosome arms. In prometaphase, initial spindle attachments are made by sister kinetochores followed by correction of erroneous attachments, centromere oscillation between spindle poles and congression towards the cell's equator. In metaphase, all chromosomes attain stable bipolar spindle attachments and align at the metaphase plate, ready for the metaphase-anaphase transition when all ties between sister chromatids are broken. This review concentrates on recent developments that have revealed the intricacies of these processes. We now know more about how the mechanisms of cohesin removal differ between prophase and the metaphase-anaphase transition, the processes for detection and correction of improper spindle-kinetochore attachments and the concept that tension between sister kinetochores is the driving factor for satisfying the spindle checkpoint. We are also beginning to gain some understanding of the mechanisms behind the co-segregation of sister chromatids at the first meiotic division.
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Affiliation(s)
- Jeffrey M Craig
- Chromosome Research Group, Department of Paediatrics, Murdoch Childrens Research Institute, Royal Children's Hospital, University of Melbourne, Flemington Road, Parkville 3052, Australia.
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374
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Kline-Smith SL, Sandall S, Desai A. Kinetochore-spindle microtubule interactions during mitosis. Curr Opin Cell Biol 2005; 17:35-46. [PMID: 15661517 PMCID: PMC8184134 DOI: 10.1016/j.ceb.2004.12.009] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The kinetochore is a proteinaceous structure that assembles onto centromeric DNA and mediates chromosome attachment to microtubules during mitosis. This description is deceivingly simple: recent proteomic studies suggest that the diminutive kinetochores of Saccharomyces cerevisiae are comprised of at least 60 proteins organized into as many as 14 different subcomplexes. Many of these proteins, such as the centromeric histone variant CENP-A, and entire subcomplexes, such as the Ndc80(Hec1) complex, are conserved from yeast to humans despite the diverse nature of the DNA sequences on which they assemble. There have recently been advances in our understanding of the molecular basis of how kinetochores establish dynamic attachments to spindle microtubules, and how these attachments are correctly oriented to ensure segregation of sister chromatids to daughter cells.
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Affiliation(s)
- Susan L Kline-Smith
- Ludwig Institute for Cancer Research, Department of Cellular & Molecular Medicine, University of California, San Diego, 9500 Gilman Dr, CMM-East, Rm 3080, La Jolla, California 92093, USA
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375
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Gatt MK, Savoian MS, Riparbelli MG, Massarelli C, Callaini G, Glover DM. Klp67A destabilises pre-anaphase microtubules but subsequently is required to stabilise the central spindle. J Cell Sci 2005; 118:2671-82. [PMID: 15928044 DOI: 10.1242/jcs.02410] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Klp67A is a member of the Kip3 subfamily of microtubule destabilising kinesins, the loss of which results in abnormally long and stable pre-anaphase microtubules. Here we examine its role during cytokinesis in Drosophila primary spermatocytes that require the coordinated interaction of an interior and peripheral set of central spindle microtubules. In mutants anaphase B spindles elongated with normal kinetics but bent towards the cortex. Both peripheral and interior spindle microtubules then formed diminished bundles of abnormally positioned central spindle microtubules associated with the pavarotti-KLP and KLP3A motor proteins. The minus ends of these were poorly aligned as revealed by Asp protein localisation. Furrows always initiated at the sites of central spindle bundles but could be unilateral or nonequatorially positioned. Ectopic furrows were stimulated by the interior central spindle and formed only after this structure buckled and contacted the cortex. Furrows often halted and regressed as they could not be sustained by the central spindles that became increasing unstable over time and often completely degraded. Consistent with this, actin and anillin failed to form homogenous bands. Thus, the Klp67A microtubule catastrophe factor is required for cytokinesis by regulating both the formation and stability of the central spindle.
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376
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Zhu C, Zhao J, Bibikova M, Leverson JD, Bossy-Wetzel E, Fan JB, Abraham RT, Jiang W. Functional analysis of human microtubule-based motor proteins, the kinesins and dyneins, in mitosis/cytokinesis using RNA interference. Mol Biol Cell 2005; 16:3187-99. [PMID: 15843429 PMCID: PMC1165403 DOI: 10.1091/mbc.e05-02-0167] [Citation(s) in RCA: 317] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Microtubule (MT)-based motor proteins, kinesins and dyneins, play important roles in multiple cellular processes including cell division. In this study, we describe the generation and use of an Escherichia coli RNase III-prepared human kinesin/dynein esiRNA library to systematically analyze the functions of all human kinesin/dynein MT motor proteins. Our results indicate that at least 12 kinesins are involved in mitosis and cytokinesis. Eg5 (a member of the kinesin-5 family), Kif2A (a member of the kinesin-13 family), and KifC1 (a member of the kinesin-14 family) are crucial for spindle formation; KifC1, MCAK (a member of the kinesin-13 family), CENP-E (a member of the kinesin-7 family), Kif14 (a member of the kinesin-3 family), Kif18 (a member of the kinesin-8 family), and Kid (a member of the kinesin-10 family) are required for chromosome congression and alignment; Kif4A and Kif4B (members of the kinesin-4 family) have roles in anaphase spindle dynamics; and Kif4A, Kif4B, MKLP1, and MKLP2 (members of the kinesin-6 family) are essential for cytokinesis. Using immunofluorescence analysis, time-lapse microscopy, and rescue experiments, we investigate the roles of these 12 kinesins in detail.
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377
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Pryde F, Khalili S, Robertson K, Selfridge J, Ritchie AM, Melton DW, Jullien D, Adachi Y. 53BP1 exchanges slowly at the sites of DNA damage and appears to require RNA for its association with chromatin. J Cell Sci 2005; 118:2043-55. [PMID: 15840649 DOI: 10.1242/jcs.02336] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
53BP1 protein is re-localized to the sites of DNA damage after ionizing radiation (IR) and is involved in DNA-damage-checkpoint signal transduction. We examined the dynamics of GFP-53BP1 in living cells. The protein starts to accumulate at the sites of DNA damage 2-3 minutes after damage induction. Fluorescence recovery after photobleaching experiments showed that GFP-53BP1 is highly mobile in non-irradiated cells. Upon binding to the IR-induced nuclear foci, the mobility of 53BP1 reduces greatly. The minimum (M) domain of 53BP1 essential for targeting to IR induced foci consists of residues 1220-1703. GFP-M protein forms foci in mouse embryonic fibroblast cells lacking functional endogenous 53BP1. The M domain contains a tandem repeat of Tudor motifs and an arginine- and glycine-rich domain (RG stretch), which are often found in proteins involved in RNA metabolism, the former being essential for targeting. RNase A treatment dissociates 53BP1 from IR-induced foci. In HeLa cells, dissociation of the M domain without the RG stretch by RNase A treatment can be restored by re-addition of nuclear RNA in the early stages of post-irradiation. 53BP1 immunoprecipitates contain some RNA molecules. Our results suggest a possible involvement of RNA in the binding of 53BP1 to chromatin damaged by IR.
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Affiliation(s)
- Fiona Pryde
- The Wellcome Trust Centre for Cell Biology, The Institute of Cell and Molecular Biology, The University of Edinburgh, The King's Buildings, Edinburgh, EH9 3JR, UK
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378
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Maiato H, DeLuca J, Salmon ED, Earnshaw WC. The dynamic kinetochore-microtubule interface. J Cell Sci 2005; 117:5461-77. [PMID: 15509863 DOI: 10.1242/jcs.01536] [Citation(s) in RCA: 282] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The kinetochore is a control module that both powers and regulates chromosome segregation in mitosis and meiosis. The kinetochore-microtubule interface is remarkably fluid, with the microtubules growing and shrinking at their point of attachment to the kinetochore. Furthermore, the kinetochore itself is highly dynamic, its makeup changing as cells enter mitosis and as it encounters microtubules. Active kinetochores have yet to be isolated or reconstituted, and so the structure remains enigmatic. Nonetheless, recent advances in genetic, bioinformatic and imaging technology mean we are now beginning to understand how kinetochores assemble, bind to microtubules and release them when the connections made are inappropriate, and also how they influence microtubule behaviour. Recent work has begun to elucidate a pathway of kinetochore assembly in animal cells; the work has revealed that many kinetochore components are highly dynamic and that some cycle between kinetochores and spindle poles along microtubules. Further studies of the kinetochore-microtubule interface are illuminating: (1) the role of the Ndc80 complex and components of the Ran-GTPase system in microtubule attachment, force generation and microtubule-dependent inactivation of kinetochore spindle checkpoint activity; (2) the role of chromosomal passenger proteins in the correction of kinetochore attachment errors; and (3) the function of microtubule plus-end tracking proteins, motor depolymerases and other proteins in kinetochore movement on microtubules and movement coupled to microtubule poleward flux.
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Affiliation(s)
- Helder Maiato
- Laboratory of Cell Regulation, NYSDH-Division of Molecular Medicine, Wadsworth Center, Empire State Plaza, PO Box 509, Albany, NY 12201-0509, USA
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379
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Guse A, Mishima M, Glotzer M. Phosphorylation of ZEN-4/MKLP1 by Aurora B Regulates Completion of Cytokinesis. Curr Biol 2005; 15:778-86. [PMID: 15854913 DOI: 10.1016/j.cub.2005.03.041] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 02/11/2005] [Accepted: 03/01/2005] [Indexed: 11/26/2022]
Abstract
The central spindle regulates the formation and positioning of the contractile ring and is essential for completion of cytokinesis [1]. Central spindle assembly begins in early anaphase with the bundling of overlapping, antiparallel, nonkinetochore microtubules [2, 3], and these bundles become compacted and mature into the midbody. Prominent components of the central spindle include aurora B kinase and centralspindlin, a complex containing a Kinesin-6 protein (ZEN-4/MKLP1) and a Rho family GAP (CYK-4/MgcRacGAP) that is essential for central spindle assembly [4]. Centralspindlin localization depends on aurora B kinase [5]. Aurora B concentrates in the midbody and persists between daughter cells. Here, we show that in C. elegans embryos and in cultured human cells, respectively, ZEN-4 and MKLP1 are phosphorylated by aurora B in vitro and in vivo on conserved C-terminal serine residues. In C. elegans embryos, a nonphosphorylatable mutant of ZEN-4 localizes properly but does not efficiently support completion of cytokinesis. In mammalian cells, an inhibitor of aurora kinase acutely attenuates phosphorylation of MKLP1. Inhibition of aurora B in late anaphase causes cytokinesis defects without disrupting the central spindle. These data indicate a conserved role for aurora-B-mediated phosphorylation of ZEN-4/MKLP1 in the completion of cytokinesis.
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Affiliation(s)
- Annika Guse
- Research Institute of Molecular Pathology, Vienna, Austria
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380
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Abstract
For proper chromosome segregation, sister kinetochores must attach to microtubules extending from opposite spindle poles prior to anaphase onset. This state is called sister kinetochore bi-orientation or chromosome bi-orientation. The mechanism ensuring chromosome bi-orientation lies at the heart of chromosome segregation, but is still poorly understood. Recent evidence suggests that mal-oriented kinetochore-to-pole connections are corrected in a tension-dependent mechanism. The cohesin complex and the Ipl1/Aurora B protein kinase seem to be key regulators for this correction. In this article, I discuss how cells ensure sister kinetochore bi-orientation for all chromosomes, mainly focusing on our recent findings in budding yeast.
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Affiliation(s)
- Tomoyuki U Tanaka
- School of Life Sciences, University of Dundee, Wellcome Trust Biocentre, Dow Street, Dundee DD1 5EH, Scotland, UK.
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381
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Holmfeldt P, Zhang X, Stenmark S, Walczak CE, Gullberg M. CaMKIIgamma-mediated inactivation of the Kin I kinesin MCAK is essential for bipolar spindle formation. EMBO J 2005; 24:1256-66. [PMID: 15775983 PMCID: PMC556404 DOI: 10.1038/sj.emboj.7600601] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Accepted: 02/07/2005] [Indexed: 11/09/2022] Open
Abstract
MCAK, a member of the kinesin-13 family, is a microtubule (MT) depolymerase that is necessary to ensure proper kinetochore MT attachment during spindle formation. Regulation of MCAK activity and localization is controlled in part by Aurora B kinase at the centromere. Here we analyzed human cells depleted of the ubiquitous Ca(2+)/calmodulin-dependent protein kinase IIgamma isoform (CaMKIIgamma) by RNA interference and found that CaMKIIgamma was necessary to suppress MCAK depolymerase activity in vivo. A functional overlap with TOGp, a MT regulator known to counteract MCAK, was suggested by similar CaMKIIgamma- and TOGp-depletion phenotypes, namely disorganized multipolar spindles. A replicating vector system, which permits inducible overexpression in cells that simultaneously synthesize interfering short hairpin RNAs, was used to dissect the functional interplay between CaMKIIgamma, TOGp, and MCAK. Our results revealed two distinct but functionally overlapping mechanisms for negative regulation of the cytosolic/centrosomal pool of MCAK. These two mechanisms, involving CaMKIIgamma and TOGp, respectively, are both essential for spindle bipolarity in a normal physiological context, but not in MCAK-depleted cells.
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Affiliation(s)
- Per Holmfeldt
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Xin Zhang
- Department of Biology, Indiana University, Bloomington, IN, USA
| | - Sonja Stenmark
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Claire E Walczak
- Departments of Biochemistry and Molecular Biology,Indiana University, Bloomington, IN, USA
| | - Martin Gullberg
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Department of Molecular Biology, Umeå University, S-901 87 Umeå, Sweden. Tel.: +46 90 785 67 03; Fax: +46 90 77 14 20; E-mail:
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382
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Moore A, Wordeman L. The mechanism, function and regulation of depolymerizing kinesins during mitosis. Trends Cell Biol 2005; 14:537-46. [PMID: 15450976 DOI: 10.1016/j.tcb.2004.09.001] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Kinesins are motor proteins that use the hydrolysis of ATP to do mechanical work. Most of these motors translocate cargo along the surface of the microtubule (MT). However, a subfamily of these motors (Kin-I kinesins) can destabilize MTs directly from their ends. This distinct ability makes their activity crucial during mitosis, when reordering of the MT cytoskeleton is most evident. Recently, much work has been done to elucidate the structure and mechanism of depolymerizing kinesins, particularly those of the mammalian kinesin mitotic centromere-associated kinesin (MCAK). In addition, new regulatory factors have been discovered that shed light on the regulation and precise role of Kin-I kinesins during mitosis.
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Affiliation(s)
- Ayana Moore
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA.
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383
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Mennella V, Rogers GC, Rogers SL, Buster DW, Vale RD, Sharp DJ. Functionally distinct kinesin-13 family members cooperate to regulate microtubule dynamics during interphase. Nat Cell Biol 2005; 7:235-45. [PMID: 15723056 DOI: 10.1038/ncb1222] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Accepted: 01/26/2005] [Indexed: 12/20/2022]
Abstract
Regulation of microtubule polymerization and depolymerization is required for proper cell development. Here, we report that two proteins of the Drosophila melanogaster kinesin-13 family, KLP10A and KLP59C, cooperate to drive microtubule depolymerization in interphase cells. Analyses of microtubule dynamics in S2 cells depleted of these proteins indicate that both proteins stimulate depolymerization, but alter distinct parameters of dynamic instability; KLP10A stimulates catastrophe (a switch from growth to shrinkage) whereas KLP59C suppresses rescue (a switch from shrinkage to growth). Moreover, immunofluorescence and live analyses of cells expressing tagged kinesins reveal that KLP10A and KLP59C target to polymerizing and depolymerizing microtubule plus ends, respectively. Our data also suggest that KLP10A is deposited on microtubules by the plus-end tracking protein, EB1. Our findings support a model in which these two members of the kinesin-13 family divide the labour of microtubule depolymerization.
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Affiliation(s)
- Vito Mennella
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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384
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Maiato H, Sampaio P, Sunkel CE. Microtubule-associated proteins and their essential roles during mitosis. ACTA ACUST UNITED AC 2005; 241:53-153. [PMID: 15548419 DOI: 10.1016/s0074-7696(04)41002-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Microtubules play essential roles during mitosis, including chromosome capture, congression, and segregation. In addition, microtubules are also required for successful cytokinesis. At the heart of these processes is the ability of microtubules to do work, a property that derives from their intrinsic dynamic behavior. However, if microtubule dynamics were not properly regulated, it is certain that microtubules alone could not accomplish any of these tasks. In vivo, the regulation of microtubule dynamics is the responsibility of microtubule-associated proteins. Among these, we can distinguish several classes according to their function: (1) promotion and stabilization of microtubule polymerization, (2) destabilization or severance of microtubules, (3) functioning as linkers between various structures, or (4) motility-related functions. Here we discuss how the various properties of microtubule-associated proteins can be used to assemble an efficient mitotic apparatus capable of ensuring the bona fide transmission of the genetic information in animal cells.
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Affiliation(s)
- Hélder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal
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385
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Yen TJ, Kao GD. Mitotic checkpoint, aneuploidy and cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2005; 570:477-499. [PMID: 18727512 DOI: 10.1007/1-4020-3764-3_17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Tim J Yen
- Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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386
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Gadea BB, Ruderman JV. Aurora kinase inhibitor ZM447439 blocks chromosome-induced spindle assembly, the completion of chromosome condensation, and the establishment of the spindle integrity checkpoint in Xenopus egg extracts. Mol Biol Cell 2004; 16:1305-18. [PMID: 15616188 PMCID: PMC551494 DOI: 10.1091/mbc.e04-10-0891] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Aurora family kinases contribute to accurate progression through several mitotic events. ZM447439 ("ZM"), the first Aurora family kinase inhibitor to be developed and characterized, was previously found to interfere with the mitotic spindle integrity checkpoint and chromosome segregation. Here, we have used extracts of Xenopus eggs, which normally proceed through the early embryonic cell cycles in the absence of functional checkpoints, to distinguish between ZM's effects on the basic cell cycle machinery and its effects on checkpoints. ZM clearly had no effect on either the kinetics or amplitude in the oscillations of activity of several key cell cycle regulators. It did, however, have striking effects on chromosome morphology. In the presence of ZM, chromosome condensation began on schedule but then failed to progress properly; instead, the chromosomes underwent premature decondensation during mid-mitosis. ZM strongly interfered with mitotic spindle assembly by inhibiting the formation of microtubules that are nucleated/stabilized by chromatin. By contrast, ZM had little effect on the assembly of microtubules by centrosomes at the spindle poles. Finally, under conditions where the spindle integrity checkpoint was experimentally induced, ZM blocked the establishment, but not the maintenance, of the checkpoint, at a point upstream of the checkpoint protein Mad2. These results show that Aurora kinase activity is required to ensure the maintenance of condensed chromosomes, the generation of chromosome-induced spindle microtubules, and activation of the spindle integrity checkpoint.
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Affiliation(s)
- Bedrick B Gadea
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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387
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Abstract
Kinetochores are the major point of contact between spindle microtubules and chromosomes. They are assemblies of more than 50 different proteins and take part in regulating and controlling their own interaction with the spindle. We review recent advance in understanding how kinetochores are properly placed onto the chromosome, and how their interaction with the microtubules of the spindle is regulated. Kinetochore orientation in meiosis I shows some particular features, and we also discuss similarities and differences between mitosis and meiosis I.
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Affiliation(s)
- Silke Hauf
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi, Bunkyo-Ku, Tokyo 113-0032, Japan.
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388
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Lampson MA, Kapoor TM. The human mitotic checkpoint protein BubR1 regulates chromosome–spindle attachments. Nat Cell Biol 2004; 7:93-8. [DOI: 10.1038/ncb1208] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Accepted: 11/18/2004] [Indexed: 12/17/2022]
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389
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Banks JD, Heald R. Adenomatous Polyposis Coli Associates with the Microtubule-Destabilizing Protein XMCAK. Curr Biol 2004; 14:2033-8. [PMID: 15556866 DOI: 10.1016/j.cub.2004.10.049] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Revised: 09/21/2004] [Accepted: 09/23/2004] [Indexed: 11/18/2022]
Abstract
During cell division, the proper formation of a bipolar spindle and its function to segregate chromosomes requires precise coordination of microtubule-stabilizing and destabilizing activities. Globally destabilized, dynamic microtubules radiating from duplicated centrosomes are locally regulated by chromosomes. Proteins at the kinetochore of each sister chromatid mediate a dynamic attachment, allowing chromosome movement coupled to microtubule polymerization/depolymerization and error-correction mechanisms for improperly attached chromosomes. The tumor suppressor protein adenomatous polyposis coli (APC) stabilizes microtubules both in vitro and in vivo and is implicated in mitosis, although its mechanisms of action are not well characterized. Here, we show that in mitotic Xenopus egg extracts, the carboxyl-terminus of APC can associate with the amino terminus of the microtubule-destabilizing KinI, Xenopus mitotic centromere-associated kinesin (XMCAK), in a cytoplasmic complex. We find that like XMCAK, APC can localize to the centromere as well as the kinetochore region of mitotic chromosomes and does not require microtubules for chromosomal targeting in Xenopus egg extracts. We propose that the presence of these proteins in a complex brings together both positive and negative microtubule effectors, whose opposing activities may be regulated by additional factors, thereby providing precise control of both global and local microtubule dynamics.
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Affiliation(s)
- Jennifer D Banks
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA
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390
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Kline-Smith SL, Walczak CE. Mitotic spindle assembly and chromosome segregation: refocusing on microtubule dynamics. Mol Cell 2004; 15:317-27. [PMID: 15304213 DOI: 10.1016/j.molcel.2004.07.012] [Citation(s) in RCA: 229] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The quest to find the underlying mechanisms of mitosis has taken many turns, which have largely been directed by the development of sensitive microscopes, enhanced microtubule-labeling techniques, advances in tubulin biochemistry, and genome-wide surveys to find the molecular "missing pieces" to the puzzle. Much of the work over the past decade has focused on the role of molecular motors in producing the necessary forces for spindle assembly and chromosome segregation. Recently, there has been a resurgence in research directed at understanding the intricate regulation of microtubule dynamics and organization during mitosis. This comes in part from the identification of new proteins involved in microtubule regulation as well as advances in fluorescence imaging that allow visualization of mitotic processes that previously have never been observed.
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Affiliation(s)
- Susan L Kline-Smith
- Department of Anatomy and Cell Biology, Indiana University Medical Sciences Program, Bloomington, IN 47405, USA
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391
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Vagnarelli P, Earnshaw WC. Chromosomal passengers: the four-dimensional regulation of mitotic events. Chromosoma 2004; 113:211-22. [PMID: 15351889 DOI: 10.1007/s00412-004-0307-3] [Citation(s) in RCA: 242] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Revised: 07/06/2004] [Accepted: 07/06/2004] [Indexed: 01/13/2023]
Abstract
Chromosomal passengers are proteins that are involved in coordinating the chromosomal and cytoskeletal events of mitosis. The passengers are present in cells as a complex with at least four members: Aurora B, a protein kinase; inner centromeric protein, an activation and targeting subunit; Survivin (function unknown) and Borealin (function also unknown). The kinase is activated at the onset of mitosis, at least partly accomplished by regulation of the levels of its constituents. As mitosis progresses, the kinase complex moves to a highly choreographed series of locations in the mitotic cell, activating key substrates at precise locations and specific times. Functions that require chromosomal passenger activity include chromatin modification (phosphorylation of histone H3), correction of kinetochore attachment errors, aspects of the spindle assembly checkpoint, assembly of a stable bipolar spindle and the completion of cytokinesis. The chromosomal passenger complex provides an essential mechanism for mitotic regulation.
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Affiliation(s)
- Paola Vagnarelli
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh, EH9 3JR, UK.
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392
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Sampath SC, Ohi R, Leismann O, Salic A, Pozniakovski A, Funabiki H. The chromosomal passenger complex is required for chromatin-induced microtubule stabilization and spindle assembly. Cell 2004; 118:187-202. [PMID: 15260989 DOI: 10.1016/j.cell.2004.06.026] [Citation(s) in RCA: 323] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Revised: 06/08/2004] [Accepted: 06/11/2004] [Indexed: 11/16/2022]
Abstract
In cells lacking centrosomes, such as those found in female meiosis, chromosomes must nucleate and stabilize microtubules in order to form a bipolar spindle. Here we report the identification of Dasra A and Dasra B, two new components of the vertebrate chromosomal passenger complex containing Incenp, Survivin, and the kinase Aurora B, and demonstrate that this complex is required for chromatin-induced microtubule stabilization and spindle formation. The failure of microtubule stabilization caused by depletion of the chromosomal passenger complex was rescued by codepletion of the microtubule-depolymerizing kinesin MCAK, whose activity is negatively regulated by Aurora B. By contrast, we present evidence that the Ran-GTP pathway of chromatin-induced microtubule nucleation does not require the chromosomal passenger complex, indicating that the mechanisms of microtubule assembly by these two pathways are distinct. We propose that the chromosomal passenger complex regulates local MCAK activity to permit spindle formation via stabilization of chromatin-associated microtubules.
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Affiliation(s)
- Srinath C Sampath
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10021, USA
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393
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Abstract
In all eukaryotes, morphogenesis of the microtubule cytoskeleton into a bipolar spindle is required for the faithful transmission of the genome to the two daughter cells during division. This process is facilitated by the intrinsic polarity and dynamic properties of microtubules and involves many proteins that modulate microtubule organization and stability. Recent work has begun to uncover the molecular mechanisms behind these dynamic events. Here we describe current models and discuss some of the complex repertoire of factors required for spindle assembly and chromosome segregation.
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Affiliation(s)
- Sharat Gadde
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720-3200, USA
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394
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Acquaviva C, Herzog F, Kraft C, Pines J. The anaphase promoting complex/cyclosome is recruited to centromeres by the spindle assembly checkpoint. Nat Cell Biol 2004; 6:892-8. [PMID: 15322556 DOI: 10.1038/ncb1167] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Accepted: 07/23/2004] [Indexed: 11/08/2022]
Abstract
The anaphase promoting complex/cyclosome (APC/C) is crucial to the control of cell division (for a review, see ref. 1). It is a multi-subunit ubiquitin ligase that, at defined points during mitosis, targets specific proteins for proteasomal degradation. The APC/C is itself regulated by the spindle or kinetochore checkpoint, which has an important role in maintaining genomic stability by preventing sister chromatid separation until all chromosomes are correctly aligned on the mitotic spindle. The spindle checkpoint regulates the APC/C by inactivating Cdc20, an important co-activator of the APC/C. There is also evidence to indicate that the spindle checkpoint components and Cdc20 are spatially regulated by the mitotic apparatus, in particular they are recruited to improperly attached kinetochores. Here, we show that the APC/C itself co-localizes with components of the spindle checkpoint to improperly attached kinetochores. Indeed, we provide evidence that the spindle checkpoint machinery is required to recruit the APC/C to kinetochores. Our data indicate that the APC/C could be regulated directly by the spindle checkpoint.
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Affiliation(s)
- Claire Acquaviva
- Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
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395
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Wang Q, Hirohashi Y, Furuuchi K, Zhao H, Liu Q, Zhang H, Murali R, Berezov A, Du X, Li B, Greene MI. The Centrosome in Normal and Transformed Cells. DNA Cell Biol 2004; 23:475-89. [PMID: 15307950 DOI: 10.1089/1044549041562276] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The centrosome is a unique organelle that functions as the microtubule organizing center in most animal cells. During cell division, the centrosomes form the poles of the bipolar mitotic spindle. In addition, the centrosomes are also needed for cytokinesis. Each mammalian somatic cell typically contains one centrosome, which is duplicated in coordination with DNA replication. Just like the chromosomes, the centrosome is precisely reproduced once and only once during each cell cycle. However, it remains a mystery how this protein-based structure undergoes accurate duplication in a semiconservative manner. Intriguingly, amplification of the centrosome has been found in numerous forms of cancers. Cells with multiple centrosomes tend to form multipolar spindles, which result in abnormal chromosome segregation during mitosis. It has therefore been postulated that centrosome aberration may compromise the fidelity of cell division and cause chromosome instability. Here we review the current understanding of how the centrosome is assembled and duplicated. We also discuss the possible mechanisms by which centrosome abnormality contributes to the development of malignant phenotype.
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Affiliation(s)
- Qiang Wang
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
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396
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Mishima M, Pavicic V, Grüneberg U, Nigg EA, Glotzer M. Cell cycle regulation of central spindle assembly. Nature 2004; 430:908-13. [PMID: 15282614 DOI: 10.1038/nature02767] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2004] [Accepted: 06/16/2004] [Indexed: 11/09/2022]
Abstract
The bipolar mitotic spindle is responsible for segregating sister chromatids at anaphase. Microtubule motor proteins generate spindle bipolarity and enable the spindle to perform mechanical work. A major change in spindle architecture occurs at anaphase onset when central spindle assembly begins. This structure regulates the initiation of cytokinesis and is essential for its completion. Central spindle assembly requires the centralspindlin complex composed of the Caenorhabditis elegans ZEN-4 (mammalian orthologue MKLP1) kinesin-like protein and the Rho family GAP CYK-4 (MgcRacGAP). Here we describe a regulatory mechanism that controls the timing of central spindle assembly. The mitotic kinase Cdk1/cyclin B phosphorylates the motor domain of ZEN-4 on a conserved site within a basic amino-terminal extension characteristic of the MKLP1 subfamily. Phosphorylation by Cdk1 diminishes the motor activity of ZEN-4 by reducing its affinity for microtubules. Preventing Cdk1 phosphorylation of ZEN-4/MKLP1 causes enhanced metaphase spindle localization and defects in chromosome segregation. Thus, phosphoregulation of the motor domain of MKLP1 kinesin ensures that central spindle assembly occurs at the appropriate time in the cell cycle and maintains genomic stability.
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Affiliation(s)
- Masanori Mishima
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria
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397
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Gassmann R, Carvalho A, Henzing AJ, Ruchaud S, Hudson DF, Honda R, Nigg EA, Gerloff DL, Earnshaw WC. Borealin: a novel chromosomal passenger required for stability of the bipolar mitotic spindle. ACTA ACUST UNITED AC 2004; 166:179-91. [PMID: 15249581 PMCID: PMC2172304 DOI: 10.1083/jcb.200404001] [Citation(s) in RCA: 324] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The chromosomal passenger complex of Aurora B kinase, INCENP, and Survivin has essential regulatory roles at centromeres and the central spindle in mitosis. Here, we describe Borealin, a novel member of the complex. Approximately half of Aurora B in mitotic cells is complexed with INCENP, Borealin, and Survivin; and Borealin binds Survivin and INCENP in vitro. A second complex contains Aurora B and INCENP, but no Borealin or Survivin. Depletion of Borealin by RNA interference delays mitotic progression and results in kinetochore–spindle misattachments and an increase in bipolar spindles associated with ectopic asters. The extra poles, which apparently form after chromosomes achieve a bipolar orientation, severely disrupt the partitioning of chromosomes in anaphase. Borealin depletion has little effect on histone H3 serine10 phosphorylation. These results implicate the chromosomal passenger holocomplex in the maintenance of spindle integrity and suggest that histone H3 serine10 phosphorylation is performed by an Aurora B–INCENP subcomplex.
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Affiliation(s)
- Reto Gassmann
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Kings Buildings, Mayfield Rd., Edinburgh EH9 3JR, Scotland, UK
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398
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Ono T, Fang Y, Spector DL, Hirano T. Spatial and temporal regulation of Condensins I and II in mitotic chromosome assembly in human cells. Mol Biol Cell 2004; 15:3296-308. [PMID: 15146063 PMCID: PMC452584 DOI: 10.1091/mbc.e04-03-0242] [Citation(s) in RCA: 283] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Two different condensin complexes make distinct contributions to metaphase chromosome architecture in vertebrate cells. We show here that the spatial and temporal distributions of condensins I and II are differentially regulated during the cell cycle in HeLa cells. Condensin II is predominantly nuclear during interphase and contributes to early stages of chromosome assembly in prophase. In contrast, condensin I is sequestered in the cytoplasm from interphase through prophase and gains access to chromosomes only after the nuclear envelope breaks down in prometaphase. The two complexes alternate along the axis of metaphase chromatids, but they are arranged into a unique geometry at the centromere/kinetochore region, with condensin II enriched near the inner kinetochore plate. This region-specific distribution of condensins I and II is severely disrupted upon depletion of Aurora B, although their association with the chromosome arm is not. Depletion of condensin subunits causes defects in kinetochore structure and function, leading to aberrant chromosome alignment and segregation. Our results suggest that the two condensin complexes act sequentially to initiate the assembly of mitotic chromosomes and that their specialized distribution at the centromere/kinetochore region may play a crucial role in placing sister kinetochores into the back-to-back orientation.
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Affiliation(s)
- Takao Ono
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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399
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Abstract
Two new studies show that phosphorylation by Aurora B kinase controls the centromere localization and catalytic activity of the microtubule depolymerase MCAK. Physical tension from microtubule attachment may influence access of MCAK to Aurora B kinase and its opposing phosphatases.
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Affiliation(s)
- Gary J Gorbsky
- Molecular, Cell and Developmental Biology, Oklahoma Medical Research Foundation, 825 Northeast 13th Street, Oklahoma City, Oklahoma 73104, USA
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400
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Ohi R, Sapra T, Howard J, Mitchison TJ. Differentiation of cytoplasmic and meiotic spindle assembly MCAK functions by Aurora B-dependent phosphorylation. Mol Biol Cell 2004; 15:2895-906. [PMID: 15064354 PMCID: PMC420112 DOI: 10.1091/mbc.e04-02-0082] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The KinI kinesin MCAK is a microtubule depolymerase important for governing spindle microtubule dynamics during chromosome segregation. The dynamic nature of spindle assembly and chromosome-microtubule interactions suggest that mechanisms must exist that modulate the activity of MCAK, both spatially and temporally. In Xenopus extracts, MCAK associates with and is stimulated by the inner centromere protein ICIS. The inner centromere kinase Aurora B also interacts with ICIS and MCAK raising the possibility that Aurora B may regulate MCAK activity as well. Herein, we demonstrate that recombinant Aurora B-INCENP inhibits Xenopus MCAK activity in vitro in a phosphorylation-dependent manner. Substituting endogenous MCAK in Xenopus extracts with the alanine mutant XMCAK-4A, which is resistant to inhibition by Aurora B-INCENP, led to assembly of mono-astral and monopolar structures instead of bipolar spindles. The size of these structures and extent of tubulin polymerization in XMCAK-4A extracts indicate that XM-CAK-4A is not defective for microtubule dynamics regulation throughout the cytoplasm. We further demonstrate that the ability of XMCAK-4A to localize to inner centromeres is abolished. Our results show that MCAK regulation of cytoplasmic and spindle-associated microtubules can be differentiated by Aurora B-dependent phosphorylation, and they further demonstrate that this regulation is required for bipolar meiotic spindle assembly.
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Affiliation(s)
- Ryoma Ohi
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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