101
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Savoian MS, Rieder CL. Mitosis in primary cultures ofDrosophila melanogasterlarval neuroblasts. J Cell Sci 2002; 115:3061-72. [PMID: 12118062 DOI: 10.1242/jcs.115.15.3061] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although Drosophila larval neuroblasts are routinely used to define mutations affecting mitosis, the dynamics of karyokinesis in this system remain to be described. Here we outline a simple method for the short-term culturing of neuroblasts, from Drosophila third instar larvae, that allows mitosis to be followed by high-resolution multi-mode light microscopy. At 24°C, spindle formation takes 7±0.5 minutes. Analysis of neuroblasts containing various GFP-tagged proteins (e.g. histone,fizzy, fizzy-related and α-tubulin) reveals that attaching kinetochores exhibit sudden, rapid pole-directed motions and that congressing and metaphase chromosomes do not undergo oscillations. By metaphase, the arms of longer chromosomes can be resolved as two chromatids, and they often extend towards a pole. Anaphase A and B occur concurrently, and during anaphase A chromatids move poleward at 3.2±0.1 μm/minute, whereas during anaphase B the spindle poles separate at 1.6±01 μm/minute. In larger neuroblasts,the spindle undergoes a sudden shift in position during midanaphase, after which the centrally located centrosome preferentially generates a robust aster and stops moving, even while the spindle continues to elongate. Together these two processes contribute to an asymmetric positioning of the spindle midzone,which, in turn, results in an asymmetric cytokinesis. Bipolar spindles form predominately (83%) in association with the separating centrosomes. However,in 17% of the cells, secondary spindles form around chromosomes without respect to centrosome position: in most cases these spindles coalesce with the primary spindle by anaphase, but in a few they remain separate and define additional ectopic poles.
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Affiliation(s)
- Matthew S Savoian
- Division of Molecular Medicine, Wadsworth Center, New York State Department of Health, P.O. Box 509, Albany, New York 12201-0509, USA
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102
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Moisoi N, Erent M, Whyte S, Martin S, Bayley PM. Calmodulin-containing substructures of the centrosomal matrix released by microtubule perturbation. J Cell Sci 2002; 115:2367-79. [PMID: 12006621 DOI: 10.1242/jcs.115.11.2367] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Calmodulin redistribution in MDCK and HeLa cells subjected to microtubule perturbations by antimitotic drugs was followed using a calmodulin-EGFP fusion protein that preserves the Ca2+ affinity, target binding and activation properties of native calmodulin. CaM-EGFP targeting to spindle structures in normal cell division and upon spindle microtubule disruption allows evaluation of the dynamic redistribution of calmodulin in cell division. Under progressive treatment of stably transfected mammalian cells with nocodazole or vinblastine, the centrosomal matrix at the mitotic poles subdivides into numerous small `star-like' structures, with the calmodulin concentrated centrally, and partially distinct from the reduced microtubule mass to which kinetochores and chromosomes are attached. Prolonged vinblastine treatment causes the release of localised calmodulin into a uniform cytoplasmic distribution, and tubulin paracrystal formation. By contrast,paclitaxel treatment of metaphase cells apparently causes limited disassembly of the pericentriolar material into a number of multipolar `ring-like'structures containing calmodulin, each one having multiple attached microtubules terminating in the partially disordered kinetochore/chromosome complex. Thus drugs with opposite effects in either destabilising or stabilising mitotic microtubules cause subdivision of the centrosomal matrix into two distinctive calmodulin-containing structures, namely small punctate`stars' or larger polar `rings' respectively. The `star-like' structures may represent an integral subcomponent for the attachment of kinetochore microtubules to the metaphase centrosome complex. The results imply that microtubules have a role in stabilising the structure of the pericentriolar matrix, involving interaction, either direct or indirect, with one or more proteins that are targets for binding of calmodulin. Possible candidates include the pericentriolar matrix-associated coiled-coil proteins containing calmodulin-binding motifs, such as myosin V, kendrin (PCNT2) and AKAP450.
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Affiliation(s)
- Nicoleta Moisoi
- Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
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103
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Suh MR, Han JW, No YR, Lee J. Transient concentration of a gamma-tubulin-related protein with a pericentrin-related protein in the formation of basal bodies and flagella during the differentiation of Naegleria gruberi. CELL MOTILITY AND THE CYTOSKELETON 2002; 52:66-81. [PMID: 12112149 DOI: 10.1002/cm.10033] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The distribution of two proteins in Naegleria gruberi, N-gammaTRP (Naegleria gamma-tubulin-related protein) and N-PRP (Naegleria pericentrin-related protein), was examined during the de novo formation of basal bodies and flagella that occurs during the differentiation of N. gruberi. After the initiation of differentiation, N-gammaTRP and N-PRP began to concentrate at the same site within cells. The percentage of cells with a concentrated region of N-gammaTRP and N-PRP was maximal (68%) at 40 min when the synthesis of tubulin had just started but no assembled microtubules were visible. When concentrated tubulin became visible (60 min), the region of concentrated N-gammaTRP and N-PRP was co-localized with the tubulin spot and then flagella began to elongate from the region of concentrated tubulin. When cells had elongated flagella, the concentrated N-gammaTRP and N-PRP were translocated to the opposite end of the flagellated cells and disappeared. The transient concentration of N-gammaTRP coincided with the transient formation of an F-actin spot at which N-gammaTRP and alpha-tubulin mRNA were co-localized. The concentration of N-gammaTRP and formation of the F-actin spot occurred without the formation of microtubules but were inhibited by cytochalasin D. These observations suggest that the regional concentration of N-gammaTRP and N-PRP is mediated by actin filaments and might provide a site of microtubule nucleation for the assembly of newly synthesized tubulins into basal bodies and flagella.
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Affiliation(s)
- Mi Ra Suh
- Department of Biology and Institute of Bioscience and Biotechnology, Yonsei University, Seoul 120-749, Korea
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104
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Haren L, Merdes A. Direct binding of NuMA to tubulin is mediated by a novel sequence motif in the tail domain that bundles and stabilizes microtubules. J Cell Sci 2002; 115:1815-24. [PMID: 11956313 DOI: 10.1242/jcs.115.9.1815] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In mitosis, NuMA localises to spindle poles where it contributes to the formation and maintenance of focussed microtubule arrays. Previous work has shown that NuMA is transported to the poles by dynein and dynactin. So far, it is unclear how NuMA accumulates at the spindle poles following transport and how it remains associated throughout mitosis. We show here that NuMA can bind to microtubules independently of dynein/dynactin. We characterise a 100-residue domain located within the C-terminal tail of NuMA that mediates a direct interaction with tubulin in vitro and that is necessary for NuMA association with tubulin in vivo. Moreover, this domain induces bundling and stabilisation of microtubules when expressed in cultured cells and leads to formation of abnormal mitotic spindles with increased microtubule asters or multiple poles. Our results suggest that NuMA organises the poles by stable crosslinking of the microtubule fibers.
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Affiliation(s)
- Laurence Haren
- Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, University of Edinburgh, King's Buildings, Edinburgh, EH9 3JR, UK
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105
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Abstract
An important mechanism for the initiation and progression of atherosclerosis is the loss of endothelial integrity, which is required for normal blood vessel function. The important components of the endothelial cell cytoskeleton system that regulate endothelial integrity include actin microfilaments and microtubules, which are both associated with protein complexes that regulate cell-cell and cell-substratum adhesion. To date, studies have shown that microfilaments are essential in maintaining the structural integrity of the endothelium while microtubules regulate the directional cell migration during repair. When microtubules are disrupted at the onset of wounding, neither centrosome reorientation, which is essential for efficient endothelial cell wound repair, nor cell migration occurs. Disruption of microfilaments is also associated with inefficient endothelial cell migration and repair. How then might these systems be associated with one another? Linker proteins, which may facilitate interaction between microtubules and actin microfilaments, have recently been identified in nonendothelial systems. It is likely that microtubule-microfilament interactions are important in the complex regulation of endothelial integrity and repair especially as they relate to atherosclerotic plaque formation.
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Affiliation(s)
- J S Y Lee
- Department of Pathology, University Health Network, University of Toronto, Ontario, Canada
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106
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Riparbelli MG, Callaini G, Glover DM, Avides MDC. A requirement for the Abnormal Spindle protein to organise microtubules of the central spindle for cytokinesis inDrosophila. J Cell Sci 2002; 115:913-22. [PMID: 11870210 DOI: 10.1242/jcs.115.5.913] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Drosophila abnormal spindle (asp) mutants exhibit a mitotic metaphase checkpoint arrest with abnormal spindle poles, which reflects a requirement for Asp for the integrity of microtubule organising centres (MTOCs). In male meiosis, the absence of a strong spindle integrity checkpoint enables asp mutant cells to proceed through anaphase and telophase. However, the central spindle region is not correctly organised and cells frequently fail to complete cytokinesis. This contrasts with meiosis in wild-type males where at late anaphase a dense array of microtubules forms in the central spindle region that has Asp localised at its border. We speculate that Asp is associated with the minus ends of microtubules that have been released from the spindle poles to form the central spindle. A parallel situation arises in female meiosis where Asp not only associates with the minus ends of microtubules at the acentriolar poles but also with the central spindle pole body that forms between the two tandem spindles of meiosis II. Upon fertilisation, Asp is also recruited to the MTOC that nucleates the sperm aster. Asp is required for growth of the microtubules of the sperm aster,which in asp mutants remains diminutive and so prevents migration of the pronuclei.
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107
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Giet R, McLean D, Descamps S, Lee MJ, Raff JW, Prigent C, Glover DM. Drosophila Aurora A kinase is required to localize D-TACC to centrosomes and to regulate astral microtubules. J Cell Biol 2002; 156:437-51. [PMID: 11827981 PMCID: PMC2173350 DOI: 10.1083/jcb.200108135] [Citation(s) in RCA: 261] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Disruption of the function of the A-type Aurora kinase of Drosophila by mutation or RNAi leads to a reduction in the length of astral microtubules in syncytial embryos, larval neuroblasts, and cultured S2 cells. In neuroblasts, it can also lead to loss of an organized centrosome and its associated aster from one of the spindle poles, whereas the centrosome at the other pole has multiple centrioles. When centrosomes are present at the poles of aurA mutants or aurA RNAi spindles, they retain many antigens but are missing the Drosophila counterpart of mammalian transforming acidic coiled coil (TACC) proteins, D-TACC. We show that a subpopulation of the total Aurora A is present in a complex with D-TACC, which is a substrate for the kinase. We propose that one of the functions of Aurora A kinase is to direct centrosomal organization such that D-TACC complexed to the MSPS/XMAP215 microtubule-associated protein may be recruited, and thus modulate the behavior of astral microtubules.
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Affiliation(s)
- Régis Giet
- Department of Genetics, Cancer Research Campaign Cell Cycle Genetics Group, University of Cambridge, Cambridge CB2 3EH, UK
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108
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Heitz MJ, Petersen J, Valovin S, Hagan IM. MTOC formation during mitotic exit in fission yeast. J Cell Sci 2001; 114:4521-32. [PMID: 11792817 DOI: 10.1242/jcs.114.24.4521] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Microtubules polymerise from nucleation templates containing γ tubulin. These templates are generally concentrated in discrete structures called microtubule organising centres (MTOCs). In Schizosaccharomyces pombe, an equatorial MTOC (EMTOC) forms mid-way through anaphase B and then disassembles during the final stages of cell separation. We show that the EMTOC was generated by recruiting γ tubulin to the equatorial F-actin ring before it constricted to cleave the cell in two during cytokinesis. The EMTOC was not a continuous ring. It had a variable structure ranging from a horseshoe to a number of short bars. EMTOC integrity depended upon the integrity of the F-actin but not the microtubule cytoskeleton. EMTOC assembly required the activity of both the septation-inducing network (SIN) that regulates the onset of cytokinesis and the anaphase-promoting complex. Activation of the SIN in interphase cells induced F-actin ring formation and contraction and the synthesis of the primary septum but did not promote EMTOC assembly. In contrast, overproduction of the polo-like kinase, Plo1, which also induced multiple rounds of septation in interphase cells, induced EMTOC formation. Thus, the network governing EMTOC formation shared many of the regulatory elements that control cytokinesis but was more complex and revealed an additional function for Plo1 during mitotic exit.
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Affiliation(s)
- M J Heitz
- School of Biological Sciences, 2.205 Stopford Building, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK
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109
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Giansanti MG, Bonaccorsi S, Bucciarelli E, Gatti M. Drosophila male meiosis as a model system for the study of cytokinesis in animal cells. Cell Struct Funct 2001; 26:609-17. [PMID: 11942616 DOI: 10.1247/csf.26.609] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Drosophila male meiosis offers unique opportunities for mutational dissection of cytokinesis. This system allows easy and unambiguos identification of mutants defective in cytokinesis through the examination of spermatid morphology. Moreover, cytokinesis defects and protein immunostaining can be analyzed with exquisite cytological resolution because of the large size of meiotic spindles. In the past few years several mutations have been isolated that disrupt meiotic cytokinesis in Drosophila males. These mutations specify genes required for the assembly, proper constriction or disassembly of the contractile ring. Molecular characterization of these genes has identified essential components of the cytokinetic machinery, highlighting the role of the central spindle during cytokinesis. This structure appears to be both necessary and sufficient for signaling cytokinesis. In addition, many data indicate that the central spindle microtubules cooperatively interact with elements of the actomyosin contractile ring, so that impairment of either of these structures prevents the formation of the other.
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Affiliation(s)
- M G Giansanti
- Istituto Pasteur-Fondazione Cenci Bolognetti, Universita' Roma La Sapienza, Italy.
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110
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Abstract
Over the past 100 years, the centrosome has risen in status from an enigmatic organelle, located at the focus of microtubules, to a key player in cell-cycle progression and cellular control. A growing body of evidence indicates that centrosomes might not be essential for spindle assembly, whereas recent data indicate that they might be important for initiating S phase and completing cytokinesis. Molecules that regulate centrosome duplication have been identified, and the expanding list of intriguing centrosome-anchored activities, the functions of which have yet to be determined, promises continued discovery.
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Affiliation(s)
- S Doxsey
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, Massachusetts 01605, USA.
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111
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Lee MJ, Gergely F, Jeffers K, Peak-Chew SY, Raff JW. Msps/XMAP215 interacts with the centrosomal protein D-TACC to regulate microtubule behaviour. Nat Cell Biol 2001; 3:643-9. [PMID: 11433296 DOI: 10.1038/35083033] [Citation(s) in RCA: 221] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The XMAP215/ch-TOG/Msps family of microtubule-associated proteins (MAPs) promote microtubule growth in vitro and are concentrated at centrosomes in vivo. We show here that Msps (mini-spindles protein) interacts with the centrosomal protein D-TACC, and that this interaction strongly influences microtubule behaviour in Drosophila embryos. If D-TACC levels are reduced, Msps does not concentrate at the centrosomes efficiently and the centrosomal microtubules appear to be destabilized. If D-TACC levels are increased, both D-TACC and Msps accumulate around the centrosomes/spindle poles, and the centrosomal microtubules appear to be stabilized. We show that the interaction between D-TACC and Msps is evolutionarily conserved. We propose that D-TACC and Msps normally cooperate to stabilize centrosomal microtubules by binding to their minus ends and binding to their plus ends as they grow out from the centrosome.
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Affiliation(s)
- M J Lee
- Department of Genetics, Wellcome/CRC Institute, Tennis Court Road, Cambridge CB2 1QR, UK
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112
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Donaldson MM, Tavares ÁA, Ohkura H, Deak P, Glover DM. Metaphase arrest with centromere separation in polo mutants of Drosophila. J Cell Biol 2001; 153:663-76. [PMID: 11352929 PMCID: PMC2192380 DOI: 10.1083/jcb.153.4.663] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
The Drosophila gene polo encodes a conserved protein kinase known to be required to organize spindle poles and for cytokinesis. Here we report two strongly hypomorphic mutations of polo that arrest cells of the larval brain at a point in metaphase when the majority of sister kinetochores have separated by between 20–50% of the total spindle length in intact cells. In contrast, analysis of sister chromatid separation in squashed preparations of cells indicates that some 83% of sisters remain attached. This suggests the separation seen in intact cells requires the tension produced by a functional spindle. The point of arrest corresponds to the spindle integrity checkpoint; Bub1 protein and the 3F3/2 epitope are present on the separated kinetochores and the arrest is suppressed by a bub1 mutation. The mutant mitotic spindles are anastral and have assembled upon centrosomes that are associated with Centrosomin and the abnormal spindle protein (Asp), but neither with γ-tubulin nor CP190. We discuss roles for Polo kinase in recruiting centrosomal proteins and in regulating progression through the metaphase–anaphase checkpoint.
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Affiliation(s)
- Mary M. Donaldson
- Cancer Research Campaign Cell Cycle Genetics Research Group, Department of Anatomy and Physiology, University of Dundee, Dundee DD1 4HN, Scotland
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Álvaro A.M. Tavares
- Cancer Research Campaign Cell Cycle Genetics Research Group, Department of Anatomy and Physiology, University of Dundee, Dundee DD1 4HN, Scotland
| | - Hiroyuki Ohkura
- Cancer Research Campaign Cell Cycle Genetics Research Group, Department of Anatomy and Physiology, University of Dundee, Dundee DD1 4HN, Scotland
| | - Peter Deak
- Cancer Research Campaign Cell Cycle Genetics Research Group, Department of Anatomy and Physiology, University of Dundee, Dundee DD1 4HN, Scotland
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - David M. Glover
- Cancer Research Campaign Cell Cycle Genetics Research Group, Department of Anatomy and Physiology, University of Dundee, Dundee DD1 4HN, Scotland
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
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113
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Wakefield JG, Bonaccorsi S, Gatti M. The drosophila protein asp is involved in microtubule organization during spindle formation and cytokinesis. J Cell Biol 2001; 153:637-48. [PMID: 11352927 PMCID: PMC2192390 DOI: 10.1083/jcb.153.4.637] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Abnormal spindle (Asp) is a 220-kD microtubule-associated protein from Drosophila that has been suggested to be involved in microtubule nucleation from the centrosome. Here, we show that Asp is enriched at the poles of meiotic and mitotic spindles and localizes to the minus ends of central spindle microtubules. Localization to these structures is independent of a functional centrosome. Moreover, colchicine treatment disrupts Asp localization to the centrosome, indicating that Asp is not an integral centrosomal protein. In both meiotic and mitotic divisions of asp mutants, microtubule nucleation occurs from the centrosome, and γ-tubulin localizes correctly. However, spindle pole focusing and organization are severely affected. By examining cells that carry mutations both in asp and in asterless, a gene required for centrosome function, we have determined the role of Asp in the absence of centrosomes. Phenotypic analysis of these double mutants shows that Asp is required for the aggregation of microtubules into focused spindle poles, reinforcing the conclusion that its function at the spindle poles is independent of any putative role in microtubule nucleation. Our data also suggest that Asp has a role in the formation of the central spindle. The inability of asp mutants to correctly organize the central spindle leads to disruption of the contractile ring machinery and failure in cytokinesis.
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Affiliation(s)
- James G. Wakefield
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma “La Sapienza,” 00185 Rome, Italy
| | - Silvia Bonaccorsi
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma “La Sapienza,” 00185 Rome, Italy
| | - Maurizio Gatti
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma “La Sapienza,” 00185 Rome, Italy
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114
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de Cárcer G, do Carmo Avides M, Lallena MJ, Glover DM, González C. Requirement of Hsp90 for centrosomal function reflects its regulation of Polo kinase stability. EMBO J 2001; 20:2878-84. [PMID: 11387220 PMCID: PMC125474 DOI: 10.1093/emboj/20.11.2878] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have previously shown that the molecular chaperone heat shock protein 90 (Hsp90) is required to ensure proper centrosome function in Drosophila and vertebrate cells. This observation led to the hypothesis that this chaperone could be required for the stability of one or more centrosomal proteins. We have found that one of these is Polo, a protein kinase known to regulate several aspects of cell division including centrosome maturation and function. Inhibition of Hsp90 results in the inactivation of Polo kinase activity. It also leads to a loss in the ability of cytoplasmic extracts to complement the failure of salt-stripped preparations of centrosomes to nucleate microtubules. This effect can be rescued upon addition of active recombinant POLO: We also show that Polo and Hsp90 are part of a complex and conclude that stabilization of Polo is one of the mechanisms by which Hsp90 contributes to the maintenance of functional centrosomes.
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Affiliation(s)
| | - Maria do Carmo Avides
- Cell Biology and Biophysics, and
Gene Expression Programmes, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany and Cancer Research Campaign Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
| | - María José Lallena
- Cell Biology and Biophysics, and
Gene Expression Programmes, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany and Cancer Research Campaign Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
| | - David M. Glover
- Cell Biology and Biophysics, and
Gene Expression Programmes, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany and Cancer Research Campaign Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
| | - Cayetano González
- Cell Biology and Biophysics, and
Gene Expression Programmes, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany and Cancer Research Campaign Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge CB2 3EH, UK Corresponding author e-mail:
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115
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Abstract
The origin recognition complex (ORC) is a six subunit complex required for eukaryotic DNA replication initiation and for silencing of the heterochromatic mating type loci in Saccharomyces cerevisiae. Our discovery of the Drosophila ORC complex concentrated in the centric heterochromatin of mitotic cells in the early embryo and its interactions with heterochromatin protein 1 (HP-1) lead us to speculate that ORC may play some general role in chromosomal folding. To explore the role of ORC in chromosomal condensation, we have identified a mutant of subunit 5 of the Drosophila melanogaster origin recognition complex (Orc5) and have characterized the phenotypes of both the Orc5 and the previously identified Orc2 mutant, k43. Both Orc mutants died at late larval stages and surprisingly, despite a reduced number of S-phase cells, an increased fraction of cells were also detected in mitosis. For this latter population of cells, Orc mutants arrest in a defective metaphase with shorter and thicker chromosomes that fail to align at the metaphase plate within a poorly assembled mitotic spindle. In addition, sister chromatid cohesion was frequently lost. PCNA and MCM4 mutants had similar phenotypes to Orc mutants. We propose that DNA replication defects trigger the mitotic arrest, due to the fact that frequent fragmentation was observed. Thus, cells have a mitotic checkpoint that senses chromosome integrity. These studies also suggest that the density of functional replication origins and completion of S phase are requirements for proper chromosomal condensation.
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Affiliation(s)
- M F Pflumm
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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116
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do Carmo Avides M, Tavares A, Glover DM. Polo kinase and Asp are needed to promote the mitotic organizing activity of centrosomes. Nat Cell Biol 2001; 3:421-4. [PMID: 11283617 DOI: 10.1038/35070110] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Interfering with the activity of polo-like kinases can lead to the formation of monopolar spindles. Polo-like kinases also regulate mitotic entry, activation of the anaphase-promoting complex and the necessary preconditions for cytokinesis. Similarities between the phenotypes of the Drosophila mutants asp and polo point towards a common role in spindle pole function. The abnormal spindles of asp mutants are bipolar but have disorganized broad poles at which gamma-tubulin has an abnormal distribution. Moreover, the synergism or of polo1 aspE3 double mutants indicates a possible involvement of these genes in a common process. Asp is a microtubule-associated protein of relative molecular mass 220,000 (Mr 220K) found at the face of the centrosome that contacts spindle microtubules. In partially purified centrosomes, it is required with gamma-tubulin to organize microtubule asters. Here, we show that Asp is the previously identified Mr 220K substrate of Polo kinase. Polo phosphorylates Asp in vitro, converting it into an MPM2 epitope. Polo and Asp proteins immunoprecipitate together and exist as part of a 25-38S complex. Extracts of polo-derived embryos are unable to restore the ability of salt-stripped centrosomes to nucleate microtubule asters. This can be rescued by addition of phosphorylated Asp or active Polo kinase.
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Affiliation(s)
- M do Carmo Avides
- Cancer Research Campaign Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge, UK CB2 3EH
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117
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Affiliation(s)
- T Küntziger
- Institut Curie, Section Recherche, UMR 144 CNRS, Paris, France
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118
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Affiliation(s)
- W F Rothwell
- Sinsheimer Laboratories, Department of Biology, University of California, Santa Cruz 95064, USA
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119
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Abstract
In the past, centrosome maturation has been described as the change in microtubule nucleation potential that occurs as cells pass through specific phases of the cell cycle. It is suggested that the idea of centrosome maturation be expanded to include gain of functions that are not necessarily related to microtubule nucleation. Some of these functions could be transient and dependent on the temporary association of molecules with the centrosome as cells progress through the cell cycle. Thus, the centrosome may best be viewed as a site for mediating macromolecular interactions, perhaps as a central processing station within the cell. The centromatrix, a relatively stable lattice of polymers within the centrosome's PCM, could serve as a scaffold for the transient binding of mediator molecules, as well as allow the dynamic exchange of centrosome constituents with a soluble cytoplasmic pool. New evidence adds support to the idea that centrioles are crucial for the maintenance of PCM structure. However, significant evidence indicates that aspects of centrosome structure and function can be maintained in the absence of centrioles. In the case of paternal centrosome maturation, sperm centrioles may not contain an associated centromatrix. It is proposed that regulation of paternal centrioles or centriole associated proteins could mediate centriole-dependent centromatrix assembly following fertilization. Thus, regulation of centromatrix-centriole interactions could be involved in maintaining the integrity of the centrosome's PCM and play an important role in centrosome disassembly during cell differentiation and morphogenesis.
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Affiliation(s)
- R E Palazzo
- Department of Molecular Biosciences, University of Kansas, Lawrence 66045, USA
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120
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Affiliation(s)
- A M Fry
- Department of Biochemistry, University of Leicester, United Kingdom
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121
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Biochemical Genetics. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50029-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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122
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Abstract
Mitosis and cytokinesis are undoubtedly the most spectacular parts of the cell cycle. Errors in the choreography of these processes can lead to aneuploidy or genetic instability, fostering cell death or disease. Here, I give an overview of the many mitotic kinases that regulate cell division and the fidelity of chromosome transmission.
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Affiliation(s)
- E A Nigg
- Max-Planck-Institute for Biochemistry, Department of Cell Biology, Am Klopferspitz 18a, D-82152 Martinsried, Germany.
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123
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Barbosa V, Yamamoto RR, Henderson DS, Glover DM. Mutation of a Drosophila gamma tubulin ring complex subunit encoded by discs degenerate-4 differentially disrupts centrosomal protein localization. Genes Dev 2000; 14:3126-39. [PMID: 11124805 PMCID: PMC317135 DOI: 10.1101/gad.182800] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We have cloned the Drosophila gene discs degenerate-4 (dd4) and find that it encodes a component of the gamma-tubulin ring complex (gammaTuRC) homologous to Spc98 of budding yeast. This provides the first opportunity to study decreased function of a member of the gamma-tubulin ring complex, other than gamma-tubulin itself, in a metazoan cell. gamma-tubulin is no longer at the centrosomes but is dispersed throughout dd4 cells and yet bipolar metaphase spindles do form, although these have a dramatically decreased density of microtubules. Centrosomin (CNN) remains in broad discrete bodies but only at the focused poles of such spindles, whereas Asp (abnormal spindle protein) is always present at the presumptive minus ends of microtubules, whether or not they are focused. This is consistent with the proposed role of Asp in coordinating the nucleation of mitotic microtubule organizing centers. The centrosome associated protein CP190 is partially lost from the spindle poles in dd4 cells supporting a weak interaction with gamma-tubulin, and the displaced protein accumulates in the vicinity of chromosomes. Electron microscopy indicates not only that the poles of dd4 cells have irregular amounts of pericentriolar material, but also that they can have abnormal centrioles. In six dd4 cells subjected to serial sectioning centrioles were missing from one of the two poles. This suggests that in addition to its role in nucleating cytoplasmic and spindle microtubules, the gammaTuRC is also essential to the structure of centrioles and the separation of centrosomes.
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Affiliation(s)
- V Barbosa
- Cancer Research Campaign, Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Cambridge, UK
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124
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Basto R, Gomes R, Karess RE. Rough deal and Zw10 are required for the metaphase checkpoint in Drosophila. Nat Cell Biol 2000; 2:939-43. [PMID: 11146659 DOI: 10.1038/35046592] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The metaphase-anaphase transition during mitosis is carefully regulated in order to assure high-fidelity transmission of genetic information to the daughter cells. A surveillance mechanism known as the metaphase checkpoint (or spindle-assembly checkpoint) monitors the attachment of kinetochores to the spindle microtubules, and inhibits anaphase onset until all chromosomes have achieved a proper bipolar orientation on the spindle. Defects in this checkpoint lead to premature anaphase onset, and consequently to greatly increased rates of aneuploidy. Here we show that the Drosophila kinetochore components Rough deal (Rod) and Zeste-White 10 (Zw10) are required for the proper functioning of the metaphase checkpoint in flies. Drosophila cells lacking either ROD or Zw10 exhibit a phenotype that is similar to that of bub1 mutants - they do not arrest in metaphase in response to spindle damage, but instead separate sister chromatids, degrade cyclin B and exit mitosis. These are the first checkpoint components to be identified that do not have obvious homologues in budding yeast.
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Affiliation(s)
- R Basto
- CNRS, Centre de Génétique Moléculaire, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France
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125
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Cambiazo V, Logarinho E, Pottstock H, Sunkel CE. Microtubule binding of the drosophila DMAP-85 protein is regulated by phosphorylation in vitro. FEBS Lett 2000; 483:37-42. [PMID: 11033352 DOI: 10.1016/s0014-5793(00)02077-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The phosphorylation of microtubule-associated proteins (MAPs) is thought to be a key factor in the regulation of microtubule (MT) stability. Previously we isolated DMAP-85, a Drosophila MAP shown to be associated with stable MTs. In this work we show that DMAP-85 phosphorylated in cell-free early embryo extracts is released from MTs. MPM-2 antibodies recognize the phosphorylated protein. In vitro, DMAP-85 can be phosphorylated by the mitotic kinase Polo affecting its binding to MTs and creating MPM-2 epitopes on the protein. The results suggest that phosphorylation of DMAP-85 might affect its MT stabilizing activity during early mitotic cycles.
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Affiliation(s)
- V Cambiazo
- Laboratorio de Biologia Celular, INTa, Universidad de Chile, Macul 5540 Santiago, Chile.
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126
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Wojcik EJ, Glover DM, Hays TS. The SCF ubiquitin ligase protein slimb regulates centrosome duplication in Drosophila. Curr Biol 2000; 10:1131-4. [PMID: 10996795 DOI: 10.1016/s0960-9822(00)00703-x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The duplication of the centrosome is a key event in the cell-division cycle. Although defects in centrosome duplication are thought to contribute to genomic instability [1-3] and are a hallmark of certain transformed cells and human cancer [4-6], the mechanism responsible for centrosome duplication is not understood. Recent experiments have established that centrosome duplication requires the activity of cyclin-dependent kinase 2 (Cdk2) and cyclins E and A [7-9]. The stability of cyclin E is regulated by the ubiquitin ligase SCF, which is a protein complex composed of Skp1, Cdc53 (Cullin) and F-box proteins [10-12]. The Skp1 and Cullin components have been detected on mammalian centrosomes, and shown to be essential for centrosome duplication and separation in Xenopus [13]. Here, we report that Slimb, an F-box protein that targets proteins to the SCFcomplex [14,15], plays a role in limiting centrosome replication. We found that, in the fruit fly Drosophila, the hypomorphic mutation slimb(crd) causes the appearance of additional centrosomes and mitotic defects in mutant larval neuroblasts.
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Affiliation(s)
- E J Wojcik
- Department of Biology, Virginia Tech University, Blacksburg, Virginia, 24061, USA.
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127
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Young A, Dictenberg JB, Purohit A, Tuft R, Doxsey SJ. Cytoplasmic dynein-mediated assembly of pericentrin and gamma tubulin onto centrosomes. Mol Biol Cell 2000; 11:2047-56. [PMID: 10848628 PMCID: PMC14902 DOI: 10.1091/mbc.11.6.2047] [Citation(s) in RCA: 199] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Centrosome assembly is important for mitotic spindle formation and if defective may contribute to genomic instability in cancer. Here we show that in somatic cells centrosome assembly of two proteins involved in microtubule nucleation, pericentrin and gamma tubulin, is inhibited in the absence of microtubules. A more potent inhibitory effect on centrosome assembly of these proteins is observed after specific disruption of the microtubule motor cytoplasmic dynein by microinjection of dynein antibodies or by overexpression of the dynamitin subunit of the dynein binding complex dynactin. Consistent with these observations is the ability of pericentrin to cosediment with taxol-stabilized microtubules in a dynein- and dynactin-dependent manner. Centrosomes in cells with reduced levels of pericentrin and gamma tubulin have a diminished capacity to nucleate microtubules. In living cells expressing a green fluorescent protein-pericentrin fusion protein, green fluorescent protein particles containing endogenous pericentrin and gamma tubulin move along microtubules at speeds of dynein and dock at centrosomes. In Xenopus extracts where gamma tubulin assembly onto centrioles can occur without microtubules, we find that assembly is enhanced in the presence of microtubules and inhibited by dynein antibodies. From these studies we conclude that pericentrin and gamma tubulin are novel dynein cargoes that can be transported to centrosomes on microtubules and whose assembly contributes to microtubule nucleation.
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Affiliation(s)
- A Young
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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128
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Flory MR, Moser MJ, Monnat RJ, Davis TN. Identification of a human centrosomal calmodulin-binding protein that shares homology with pericentrin. Proc Natl Acad Sci U S A 2000; 97:5919-23. [PMID: 10823944 PMCID: PMC18534 DOI: 10.1073/pnas.97.11.5919] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Eukaryotic chromosome segregation depends on the mitotic spindle apparatus, a bipolar array of microtubules nucleated from centrosomes. Centrosomal microtubule nucleation requires attachment of gamma-tubulin ring complexes to a salt-insoluble centrosomal core, but the factor(s) underlying this attachment remains unknown. In budding yeast, this attachment is provided by the coiled-coil protein Spc110p, which links the yeast gamma-tubulin complex to the core of the yeast centrosome. Here, we show that the large coiled-coil protein kendrin is a human orthologue of Spc110p. We identified kendrin by its C-terminal calmodulin-binding site, which shares homology with the Spc110p calmodulin-binding site. Kendrin localizes specifically to centrosomes throughout the cell cycle. N-terminal regions of kendrin share significant sequence homology with pericentrin, a previously identified murine centrosome component known to interact with gamma-tubulin. In mitotic human breast carcinoma cells containing abundant centrosome-like structures, kendrin is found only at centrosomes associated with spindle microtubules.
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Affiliation(s)
- M R Flory
- Program in Molecular and Cellular Biology, Department of Pathology, University of Washington, Seattle, WA 98195, USA
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129
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Merdes A, Heald R, Samejima K, Earnshaw WC, Cleveland DW. Formation of spindle poles by dynein/dynactin-dependent transport of NuMA. J Cell Biol 2000; 149:851-62. [PMID: 10811826 PMCID: PMC2174573 DOI: 10.1083/jcb.149.4.851] [Citation(s) in RCA: 252] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2000] [Accepted: 03/30/2000] [Indexed: 11/22/2022] Open
Abstract
NuMA is a large nuclear protein whose relocation to the spindle poles is required for bipolar mitotic spindle assembly. We show here that this process depends on directed NuMA transport toward microtubule minus ends powered by cytoplasmic dynein and its activator dynactin. Upon nuclear envelope breakdown, large cytoplasmic aggregates of green fluorescent protein (GFP)-tagged NuMA stream poleward along spindle fibers in association with the actin-related protein 1 (Arp1) protein of the dynactin complex and cytoplasmic dynein. Immunoprecipitations and gel filtration demonstrate the assembly of a reversible, mitosis-specific complex of NuMA with dynein and dynactin. NuMA transport is required for spindle pole assembly and maintenance, since disruption of the dynactin complex (by increasing the amount of the dynamitin subunit) or dynein function (with an antibody) strongly inhibits NuMA translocation and accumulation and disrupts spindle pole assembly.
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Affiliation(s)
- A Merdes
- ICMB, University of Edinburgh, Scotland.
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130
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Affiliation(s)
| | - Claire E. Walczak
- Medical Sciences Program, Indiana University, Bloomington, Indiana 47405
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131
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Lange BM, Bachi A, Wilm M, González C. Hsp90 is a core centrosomal component and is required at different stages of the centrosome cycle in Drosophila and vertebrates. EMBO J 2000; 19:1252-62. [PMID: 10716925 PMCID: PMC305666 DOI: 10.1093/emboj/19.6.1252] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
To determine the molecular composition of the centrosome of a higher eukaryote, we carried out a systematic nano-electrospray tandem or MALDI mass spectrometry analysis of the polypeptides present in highly enriched preparations of immunoisolated Drosophila centrosomes. One of the proteins identified is Hsp83, a member of the highly conserved Hsp90 family including chaperones known to maintain the activity of many proteins but suspected to have other essential, unidentified functions. We have found that a fraction of the total Hsp90 pool is localized at the centrosome throughout the cell cycle at different stages of development in Drosophila and vertebrates. This association between Hsp90 and the centrosome can be observed in purified centrosomes and after treatment with microtubule depolymerizing drugs, two criteria normally used to define core centrosomal components. Disruption of Hsp90 function by mutations in the Drosophila gene or treatment of mammalian cells with the Hsp90 inhibitor geldanamycin, results in abnormal centrosome separation and maturation, aberrant spindles and impaired chromosome segregation. This suggests that another role of Hsp90 might be to ensure proper centrosome function.
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Affiliation(s)
- B M Lange
- Cell Biology and Cell Biophysics Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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132
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Schnackenberg BJ, Hull DR, Balczon RD, Palazzo RE. Reconstitution of microtubule nucleation potential in centrosomes isolated from Spisula solidissima oocytes. J Cell Sci 2000; 113 ( Pt 6):943-53. [PMID: 10683143 DOI: 10.1242/jcs.113.6.943] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Treatment of isolated Spisula solidissima centrosomes with KI removes (gamma)-tubulin, 25 nm rings, and their microtubule nucleation potential, revealing the presence of a filamentous lattice, the ‘centromatrix’. Treatment of this centromatrix with Spisula oocyte extract results in the binding of (gamma)-tubulin and 25 nm rings, and the recovery of microtubule nucleation potential. Fractionation of this extract resulted in the separation of elements that are required for the recovery of microtubule nucleation potential. We show that some, but not all, of the elements needed cosediment with microtubules. Further, extracts prepared from activated (meiotic) and non-activated (interphase) Spisula oocytes, CHO cells blocked in S phase, Drosophila embryos and Xenopus oocytes all support the recovery of microtubule nucleation potential by the Spisula centromatrix. These results demonstrate that components necessary for centrosome-dependent microtubule nucleation are functionally conserved and abundant in both interphase and meiotic/mitotic cytoplasm.
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Affiliation(s)
- B J Schnackenberg
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
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133
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Schiebel E. gamma-tubulin complexes: binding to the centrosome, regulation and microtubule nucleation. Curr Opin Cell Biol 2000; 12:113-8. [PMID: 10679351 DOI: 10.1016/s0955-0674(99)00064-2] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Microtubule assembly is initiated in vivo by gamma-tubulin complexes. Cytoplasmic gamma-tubulin complexes are targeted to centrosomes or to other microtubule organizing centers (MTOCs) via a set of so called gamma-tubulin complex binding proteins (GTBPs) that probably interact with the conserved Spc97p/Spc98p protein family of gamma-tubulin complexes. In other cell types, gamma-tubulin complexes may initiate microtubule formation near chromosomes in a MTOC-independent manner. Recently, major advances have been achieved through the finding that gamma-tubulin, Spc97p and Spc98p form a conserved core that is probably responsible for microtubule nucleation, and by the discovery that a yeast GTBP is regulated in a cell-cycle-dependent manner and in response to an external signal. Furthermore, it was found that the small GTPase Ran in its GDP-bound state may promote spindle assembly. In addition, an essential function of gamma-tubulin in basal body duplication has been demonstrated in Paramecium.
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Affiliation(s)
- E Schiebel
- Beatson Laboratories, The Beatson Institute for Cancer Research, Cancer Research Campaign, Glasgow, G61 1BD, UK. uk
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134
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Gergely F, Kidd D, Jeffers K, Wakefield JG, Raff JW. D-TACC: a novel centrosomal protein required for normal spindle function in the early Drosophila embryo. EMBO J 2000; 19:241-52. [PMID: 10637228 PMCID: PMC305558 DOI: 10.1093/emboj/19.2.241] [Citation(s) in RCA: 176] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/1999] [Revised: 11/10/1999] [Accepted: 11/11/1999] [Indexed: 11/14/2022] Open
Abstract
We identify Drosophila TACC (D-TACC) as a novel protein that is concentrated at centrosomes and interacts with microtubules. We show that D-TACC is essential for normal spindle function in the early embryo; if D-TACC function is perturbed by mutation or antibody injection, the microtubules emanating from centrosomes in embryos are short and chromosomes often fail to segregate properly. The C-terminal region of D-TACC interacts, possibly indirectly, with microtubules, and can target a heterologous fusion protein to centrosomes and microtubules in embryos. This C-terminal region is related to the mammalian transforming, acidic, coiled-coil-containing (TACC) family of proteins. The function of the TACC proteins is unknown, but the genes encoding the known TACC proteins are all associated with genomic regions that are rearranged in certain cancers. We show that at least one of the mammalian TACC proteins appears to be associated with centrosomes and microtubules in human cells. We propose that this conserved C-terminal 'TACC domain' defines a new family of microtubule-interacting proteins.
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Affiliation(s)
- F Gergely
- Wellcome/CRC Institute and Department of Genetics, Tennis Court Road, Cambridge CB2 1QR, UK
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135
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Purohit A, Tynan SH, Vallee R, Doxsey SJ. Direct interaction of pericentrin with cytoplasmic dynein light intermediate chain contributes to mitotic spindle organization. J Cell Biol 1999; 147:481-92. [PMID: 10545494 PMCID: PMC2151190 DOI: 10.1083/jcb.147.3.481] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/1999] [Accepted: 09/27/1999] [Indexed: 11/26/2022] Open
Abstract
Pericentrin is a conserved protein of the centrosome involved in microtubule organization. To better understand pericentrin function, we overexpressed the protein in somatic cells and assayed for changes in the composition and function of mitotic spindles and spindle poles. Spindles in pericentrin-overexpressing cells were disorganized and mispositioned, and chromosomes were misaligned and missegregated during cell division, giving rise to aneuploid cells. We unexpectedly found that levels of the molecular motor cytoplasmic dynein were dramatically reduced at spindle poles. Cytoplasmic dynein was diminished at kinetochores also, and the dynein-mediated organization of the Golgi complex was disrupted. Dynein coimmunoprecipitated with overexpressed pericentrin, suggesting that the motor was sequestered in the cytoplasm and was prevented from associating with its cellular targets. Immunoprecipitation of endogenous pericentrin also pulled down cytoplasmic dynein in untransfected cells. To define the basis for this interaction, pericentrin was coexpressed with cytoplasmic dynein heavy (DHCs), intermediate (DICs), and light intermediate (LICs) chains, and the dynamitin and p150(Glued) subunits of dynactin. Only the LICs coimmunoprecipitated with pericentrin. These results provide the first physiological role for LIC, and they suggest that a pericentrin-dynein interaction in vivo contributes to the assembly, organization, and function of centrosomes and mitotic spindles.
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Affiliation(s)
- Aruna Purohit
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Sharon H. Tynan
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Richard Vallee
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Stephen J. Doxsey
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
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136
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Cullen CF, Deák P, Glover DM, Ohkura H. mini spindles: A gene encoding a conserved microtubule-associated protein required for the integrity of the mitotic spindle in Drosophila. J Cell Biol 1999; 146:1005-18. [PMID: 10477755 PMCID: PMC2169485 DOI: 10.1083/jcb.146.5.1005] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We describe a new Drosophila gene, mini spindles (msps) identified in a cytological screen for mitotic mutant. Mutation in msps disrupts the structural integrity of the mitotic spindle, resulting in the formation of one or more small additional spindles in diploid cells. Nucleation of microtubules from centrosomes, metaphase alignment of chromosomes, or the focusing of spindle poles appears much less affected. The msps gene encodes a 227-kD protein with high similarity to the vertebrate microtubule-associated proteins (MAPs), human TOGp and Xenopus XMAP215, and with limited similarity to the Dis1 and STU2 proteins from fission yeast and budding yeast. Consistent with their sequence similarity, Msps protein also associates with microtubules in vitro. In the embryonic division cycles, Msps protein localizes to centrosomal regions at all mitotic stages, and spreads over the spindles during metaphase and anaphase. The absence of centrosomal staining in interphase of the cellularized embryos suggests that the interactions between Msps protein and microtubules or centrosomes may be regulated during the cell cycle.
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Affiliation(s)
- C. Fiona Cullen
- Institute of Cell and Molecular Biology, The University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
| | - Peter Deák
- Cancer Research Campaign Laboratories, Department of Anatomy and Physiology, The University of Dundee, DD1 4HN, United Kingdom
- Cancer Research Campaign Cell Cycle Genetics Group, Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - David M. Glover
- Cancer Research Campaign Laboratories, Department of Anatomy and Physiology, The University of Dundee, DD1 4HN, United Kingdom
- Cancer Research Campaign Cell Cycle Genetics Group, Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Hiroyuki Ohkura
- Institute of Cell and Molecular Biology, The University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
- Cancer Research Campaign Laboratories, Department of Anatomy and Physiology, The University of Dundee, DD1 4HN, United Kingdom
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