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Forer A, Berns MW. Elastic Tethers Between Separating Anaphase Chromosomes Regulate the Poleward Speeds of the Attached Chromosomes in Crane-Fly Spermatocytes. Front Mol Biosci 2020; 7:161. [PMID: 32850955 PMCID: PMC7405647 DOI: 10.3389/fmolb.2020.00161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 06/24/2020] [Indexed: 01/09/2023] Open
Abstract
Elastic "tethers" connect separating anaphase chromosomes in most (or all) animal cells. We tested whether tethers are involved in coordinating movements of separating anaphase chromosomes in crane-fly spermatocytes. In these cells the coupled movements of separating chromosomes become uncoupled after the tethers are severed by laser microbeam irradiation of the interzone region between the chromosomes (Sheykhani et al., 2017). While this strongly suggests that tethers are involved with coordinating the poleward chromosome movements, the experiments are open to another interpretation: laser irradiations that cut the tethers also might damage something else in the interzone, and those non-tether components might regulate chromosome movements. In the experiments reported herein we distinguish between those two possibilities by disabling the tethers without cutting the interzone. We cut the arms from individual chromosomes, thereby severing the mechanical connection between separating chromosomes, disconnecting them, without damaging components in the interzone. Disabling tethers in this way uncoupled the movements of the separating chromosomes. We thus conclude that tethers are involved in regulating the speeds of separating anaphase chromosomes in crane-fly spermatocytes.
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Affiliation(s)
- Arthur Forer
- Biology Department, York University, North York, ON, Canada
| | - Michael W. Berns
- Department of Surgery, Biomedical Engineering and Developmental and Cell Biology, Beckman Laser Institute, University of California, Irvine, Irvine, CA, United States
- Department of Bioengineering, Institute for Engineering in Medicine, University of California, San Diego, San Diego, CA, United States
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2
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Amargant F, Barragan M, Vassena R, Vernos I. Insights of the tubulin code in gametes and embryos: from basic research to potential clinical applications in humans†. Biol Reprod 2020; 100:575-589. [PMID: 30247519 DOI: 10.1093/biolre/ioy203] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 07/05/2018] [Accepted: 09/20/2018] [Indexed: 12/14/2022] Open
Abstract
Microtubules are intracellular filaments that define in space and in time a large number of essential cellular functions such as cell division, morphology and motility, intracellular transport and flagella and cilia assembly. They are therefore essential for spermatozoon and oocyte maturation and function, and for embryo development. The dynamic and functional properties of the microtubules are in large part defined by various classes of interacting proteins including MAPs (microtubule associated proteins), microtubule-dependent motors, and severing and modifying enzymes. Multiple mechanisms regulate these interactions. One of them is defined by the high diversity of the microtubules themselves generated by the combination of different tubulin isotypes and by several tubulin post-translational modifications (PTMs). This generates a so-called tubulin code that finely regulates the specific set of proteins that associates with a given microtubule thereby defining the properties and functions of the network. Here we provide an in depth review of the current knowledge on the tubulin isotypes and PTMs in spermatozoa, oocytes, and preimplantation embryos in various model systems and in the human species. We focus on functional implications of the tubulin code for cytoskeletal function, particularly in the field of human reproduction and development, with special emphasis on gamete quality and infertility. Finally, we discuss some of the knowledge gaps and propose future research directions.
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Affiliation(s)
- Farners Amargant
- Clínica EUGIN, Barcelona, Spain.,Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain
| | | | | | - Isabelle Vernos
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain.,Institució Catalana de Recerca I Estudis Avançats (ICREA), Barcelona, Spain
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3
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Forer A, Sheykhani R, Berns MW. Anaphase Chromosomes in Crane-Fly Spermatocytes Treated With Taxol (Paclitaxel) Accelerate When Their Kinetochore Microtubules Are Cut: Evidence for Spindle Matrix Involvement With Spindle Forces. Front Cell Dev Biol 2018; 6:77. [PMID: 30087895 PMCID: PMC6066604 DOI: 10.3389/fcell.2018.00077] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 06/29/2018] [Indexed: 01/01/2023] Open
Abstract
Various experiments have indicated that anaphase chromosomes continue to move after their kinetochore microtubules are severed. The chromosomes move poleward at an accelerated rate after the microtubules are cut but they slow down 1-3 min later and move poleward at near the original speed. There are two published interpretations of chromosome movements with severed kinetochore microtubules. One interpretation is that dynein relocates to the severed microtubule ends and propels them poleward by pushing against non-kinetochore microtubules. The other interpretation is that components of a putative "spindle matrix" normally push kinetochore microtubules poleward and continue to do so after the microtubules are severed from the pole. In this study we distinguish between these interpretations by treating cells with taxol. Taxol eliminates microtubule dynamics, alters spindle microtubule arrangements, and inhibits dynein motor activity in vivo. If the dynein interpretation is correct, taxol should interfere with chromosome movements after kinetochore microtubules are severed because it alters the arrangements of spindle microtubules and because it blocks dynein activity. If the "spindle matrix" interpretation is correct, on the other hand, taxol should not interfere with the accelerated movements. Our results support the spindle matrix interpretation: anaphase chromosomes in taxol-treated crane-fly spermatocytes accelerated after their kinetochore microtubules were severed.
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Affiliation(s)
- Arthur Forer
- Biology Department, York University, North York, ON, Canada
| | | | - Michael W Berns
- Beckman Laser Institute and Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, United States.,Department of Bioengineering and Institute for Engineering in Medicine, University of California, San Diego, San Diego, CA, United States
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4
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Jenkins BV, Saunders HAJ, Record HL, Johnson-Schlitz DM, Wildonger J. Effects of mutating α-tubulin lysine 40 on sensory dendrite development. J Cell Sci 2017; 130:4120-4131. [PMID: 29122984 PMCID: PMC5769580 DOI: 10.1242/jcs.210203] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 11/06/2017] [Indexed: 12/28/2022] Open
Abstract
Microtubules are essential for neuronal structure and function. Axonal and dendritic microtubules are enriched in post-translational modifications that impact microtubule dynamics, transport and microtubule-associated proteins. Acetylation of α-tubulin lysine 40 (K40) is a prominent and conserved modification of neuronal microtubules. However, the cellular role of microtubule acetylation remains controversial. To resolve how microtubule acetylation might affect neuronal morphogenesis, we mutated endogenous α-tubulin in vivo using a new Drosophila strain that facilitates the rapid knock-in of designer αTub84B alleles (the predominant α-tubulin-encoding gene in flies). Leveraging our new strain, we found that microtubule acetylation, as well as polyglutamylation and (de)tyrosination, is not essential for survival. However, we found that dendrite branch refinement in sensory neurons relies on α-tubulin K40. Mutagenesis of K40 reveals moderate yet significant changes in dendritic lysosome transport, microtubule polymerization and Futsch protein distribution in dendrites but not in axons. Our studies point to an unappreciated role for α-tubulin K40 and acetylation in dendrite morphogenesis. While our results are consistent with the idea that acetylation tunes microtubule function within neurons, they also suggest there may be an acetylation-independent requirement for α-tubulin K40. This article has an associated First Person interview with the first author of the paper. Highlighted Article: Neurons are enriched in post-translationally modified microtubules. Targeted mutagenesis of endogenous α-tubulin in flies reveals that dendrite branch refinement is altered by acetylation-blocking mutations.
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Affiliation(s)
- Brian V Jenkins
- Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Harriet A J Saunders
- Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706, USA.,Integrated Program in Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Helena L Record
- Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | | - Jill Wildonger
- Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706, USA
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5
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Microscopy Methods for Analysis of Spindle Dynamics in Meiotic Drosophila Spermatocytes. Methods Mol Biol 2017. [PMID: 28349402 DOI: 10.1007/978-1-4939-6340-9_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The spindle is a microtubule-based structure whose remodeling is required for partitioning the chromosomes and cytoplasm during meiosis. Characterizing microtubule behavior is fundamental to understanding how these tubulin polymers contribute to successful cell division. Here, a procedure is described for the imaging and analysis of spindle microtubule dynamics in cultures of living Drosophila melanogaster primary spermatocytes expressing tubulin tagged with enhanced green fluorescent protein. It employs time-lapse scanning confocal microscopy and the photobleaching of fiduciary marks onto fluorescently tagged microtubules. These labels are subsequently used to determine the sites and rates of kinetochore fiber growth and shrinkage during metaphase. This method can be readily applied to different microtubule populations, meiotic stages, and genetic backgrounds.
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6
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Mechanisms of Chromosome Congression during Mitosis. BIOLOGY 2017; 6:biology6010013. [PMID: 28218637 PMCID: PMC5372006 DOI: 10.3390/biology6010013] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 01/07/2017] [Accepted: 01/28/2017] [Indexed: 12/13/2022]
Abstract
Chromosome congression during prometaphase culminates with the establishment of a metaphase plate, a hallmark of mitosis in metazoans. Classical views resulting from more than 100 years of research on this topic have attempted to explain chromosome congression based on the balance between opposing pulling and/or pushing forces that reach an equilibrium near the spindle equator. However, in mammalian cells, chromosome bi-orientation and force balance at kinetochores are not required for chromosome congression, whereas the mechanisms of chromosome congression are not necessarily involved in the maintenance of chromosome alignment after congression. Thus, chromosome congression and maintenance of alignment are determined by different principles. Moreover, it is now clear that not all chromosomes use the same mechanism for congressing to the spindle equator. Those chromosomes that are favorably positioned between both poles when the nuclear envelope breaks down use the so-called "direct congression" pathway in which chromosomes align after bi-orientation and the establishment of end-on kinetochore-microtubule attachments. This favors the balanced action of kinetochore pulling forces and polar ejection forces along chromosome arms that drive chromosome oscillatory movements during and after congression. The other pathway, which we call "peripheral congression", is independent of end-on kinetochore microtubule-attachments and relies on the dominant and coordinated action of the kinetochore motors Dynein and Centromere Protein E (CENP-E) that mediate the lateral transport of peripheral chromosomes along microtubules, first towards the poles and subsequently towards the equator. How the opposite polarities of kinetochore motors are regulated in space and time to drive congression of peripheral chromosomes only now starts to be understood. This appears to be regulated by position-dependent phosphorylation of both Dynein and CENP-E and by spindle microtubule diversity by means of tubulin post-translational modifications. This so-called "tubulin code" might work as a navigation system that selectively guides kinetochore motors with opposite polarities along specific spindle microtubule populations, ultimately leading to the congression of peripheral chromosomes. We propose an integrated model of chromosome congression in mammalian cells that depends essentially on the following parameters: (1) chromosome position relative to the spindle poles after nuclear envelope breakdown; (2) establishment of stable end-on kinetochore-microtubule attachments and bi-orientation; (3) coordination between kinetochore- and arm-associated motors; and (4) spatial signatures associated with post-translational modifications of specific spindle microtubule populations. The physiological consequences of abnormal chromosome congression, as well as the therapeutic potential of inhibiting chromosome congression are also discussed.
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7
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αTAT1 controls longitudinal spreading of acetylation marks from open microtubules extremities. Sci Rep 2016; 6:35624. [PMID: 27752143 PMCID: PMC5067677 DOI: 10.1038/srep35624] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/27/2016] [Indexed: 01/23/2023] Open
Abstract
Acetylation of the lysine 40 of α-tubulin (K40) is a post-translational modification occurring in the lumen of microtubules (MTs) and is controlled by the α-tubulin acetyl-transferase αTAT1. How αTAT1 accesses the lumen and acetylates α-tubulin there has been an open question. Here, we report that acetylation starts at open ends of MTs and progressively spreads longitudinally from there. We observed acetylation marks at the open ends of in vivo MTs re-growing after a Nocodazole block, and acetylated segments growing in length with time. Bias for MTs extremities was even more pronounced when using non-dynamic MTs extracted from HeLa cells. In contrast, K40 acetylation was mostly uniform along the length of MTs reconstituted from purified tubulin in vitro. Quantitative modelling of luminal diffusion of αTAT1 suggested that the uniform acetylation pattern observed in vitro is consistent with defects in the MT lattice providing lateral access to the lumen. Indeed, we observed that in vitro MTs are permeable to macromolecules along their shaft while cellular MTs are not. Our results demonstrate αTAT1 enters the lumen from open extremities and spreads K40 acetylation marks longitudinally along cellular MTs. This mode of tip-directed microtubule acetylation may allow for selective acetylation of subsets of microtubules.
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8
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Barisic M, Maiato H. The Tubulin Code: A Navigation System for Chromosomes during Mitosis. Trends Cell Biol 2016; 26:766-775. [PMID: 27344407 DOI: 10.1016/j.tcb.2016.06.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/27/2016] [Accepted: 06/02/2016] [Indexed: 10/25/2022]
Abstract
Before chromosomes segregate during mitosis in metazoans, they align at the cell equator by a process known as chromosome congression. This is in part mediated by the coordinated activities of kinetochore motors with opposite directional preferences that transport peripheral chromosomes along distinct spindle microtubule populations. Because spindle microtubules are all made from the same α/β-tubulin heterodimers, a critical longstanding question has been how chromosomes are guided to specific locations during mitosis. This implies the existence of spatial cues/signals on specific spindle microtubules that are read by kinetochore motors on chromosomes and ultimately indicate the way towards the equator. Here, we discuss the emerging concept that tubulin post-translational modifications (PTMs), as part of the so-called tubulin code, work as a navigation system for kinetochore-based chromosome motility during early mitosis.
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Affiliation(s)
- Marin Barisic
- Danish Cancer Society Research Center, Cell Division Laboratory, Strandboulevarden 49, 2100 Copenhagen, Denmark.
| | - Helder Maiato
- Chromosome Instability and Dynamics Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Cell Division Unit, Department of Experimental Biology, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal.
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9
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Savoian MS. Using Photobleaching to Measure Spindle Microtubule Dynamics in Primary Cultures of Dividing Drosophila Meiotic Spermatocytes. J Biomol Tech 2016; 26:66-73. [PMID: 25802491 DOI: 10.7171/jbt.15-2602-004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In dividing animal cells, a microtubule (MT)-based bipolar spindle governs chromosome movement. Current models propose that the spindle facilitates and/or generates translocating forces by regionally depolymerizing the kinetochore fibers (k-fibers) that bind each chromosome. It is unclear how conserved these sites and the resultant chromosome-moving mechanisms are between different dividing cell types because of the technical challenges of quantitatively studying MTs in many specimens. In particular, our knowledge of MT kinetics during the sperm-producing male meiotic divisions remains in its infancy. In this study, I use an easy-to-implement photobleaching-based assay for measuring spindle MT dynamics in primary cultures of meiotic spermatocytes isolated from the fruit fly Drosophila melanogaster. By use of standard scanning confocal microscopy features, fiducial marks were photobleached on fluorescent protein (FP)-tagged MTs. These were followed by time-lapse imaging during different division stages, and their displacement rates were calculated using public domain software. I find that k-fibers continually shorten at their poles during metaphase and anaphase A through the process of MT flux. Anaphase chromosome movement is complemented by Pac-Man, the shortening of the k-fiber at its chromosomal interface. Thus, Drosophila spermatocytes share the sites of spindle dynamism and mechanisms of chromosome movement with mitotic cells. The data reveal the applicability of the photobleaching assay for measuring MT dynamics in primary cultures. This approach can be readily applied to other systems.
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Affiliation(s)
- Matthew S Savoian
- Massey University, Institute of Fundamental Sciences, Palmerston North, New Zealand
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10
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Blaschke M, McKinnon R, Nguyen CH, Holzner S, Zehl M, Atanasov AG, Schelch K, Krieger S, Diaz R, Frisch R, Feistel B, Jäger W, Ecker GF, Dirsch VM, Grusch M, Zupko I, Urban E, Kopp B, Krupitza G. A eudesmane-type sesquiterpene isolated from Pluchea odorata (L.) Cass. combats three hallmarks of cancer cells: Unrestricted proliferation, escape from apoptosis and early metastatic outgrowth in vitro. Mutat Res 2015; 777:79-90. [PMID: 25989051 DOI: 10.1016/j.mrfmmm.2015.04.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 04/05/2015] [Accepted: 04/24/2015] [Indexed: 06/04/2023]
Abstract
Pluchea odorata is ethno pharmaceutically used to treat inflammation-associated disorders. The dichloromethane extract (DME) was tested in the carrageenan-induced rat paw oedema assay investigating its effect on inflammation that was inhibited by 37%. Also an in vitro anti-neoplastic potential was reported. However, rather limited information about the bio-activity of purified compounds and their cellular mechanisms are available. Therefore, two of the most abundant eudesmanes in P. odorata were isolated and their anti-neoplastic and anti-intravasative activities were studied. HL-60 cells were treated with P. odorata compounds and metabolic activity, cell number reduction, cell cycle progression and apoptosis induction were correlated with relevant protein expression. Tumour cell intravasation through lymph endothelial monolayers was measured and potential causal mechanisms were analyzed by Western blotting. Compound PO-1 decreased the metabolic activity of HL-60 cells (IC50 = 8.9 μM after 72 h) and 10 μM PO-1 induced apoptosis, while PO-2 showed just weak anti-neoplastic activities at concentrations beyond 100 μM. PO-1 arrested the cell cycle in G1 and this correlated with induction of JunB expression. Independent of this mechanism 25 μM PO-1 decreased MCF-7 spheroid intravasation through the lymph endothelial barrier. Hence, PO-1 inhibits an early step of metastasis, impairs unrestricted proliferation and induces apoptosis at low micromolar concentrations. These results warrant further testing in vivo to challenge the potential of PO-1 as novel lead compound.
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Affiliation(s)
- Michael Blaschke
- Department of Pharmacognosy, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Department of Clinical Pathology, Medical University of Vienna, Waehringer Guertel 18-20, Austria
| | - Ruxandra McKinnon
- Department of Pharmacognosy, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Chi Huu Nguyen
- Department of Clinical Pathology, Medical University of Vienna, Waehringer Guertel 18-20, Austria; Department of Clinical Pharmacy and Diagnostics, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Silvio Holzner
- Department of Clinical Pathology, Medical University of Vienna, Waehringer Guertel 18-20, Austria
| | - Martin Zehl
- Department of Pharmacognosy, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | | | - Karin Schelch
- Department of Medicine I, Institute of Cancer Research, Comprehensive Cancer Centre Vienna, Medical University of Vienna, Borschkegasse 8a, A-1090 Vienna, Austria
| | - Sigurd Krieger
- Department of Clinical Pathology, Medical University of Vienna, Waehringer Guertel 18-20, Austria
| | - Rene Diaz
- Institute for Ethnobiology, Playa Diana, San José/Petén, Guatemala
| | - Richard Frisch
- Institute for Ethnobiology, Playa Diana, San José/Petén, Guatemala
| | - Björn Feistel
- Finzelberg GmbH & Co. KG, Koblenzer Strasse 48-54, D-56626 Andernach, Germany
| | - Walter Jäger
- Department of Clinical Pharmacy and Diagnostics, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Gerhard F Ecker
- Department of Pharmaceutical Chemistry, Division of Drug Design and Medicinal Chemistry, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria
| | - Verena M Dirsch
- Department of Pharmacognosy, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Michael Grusch
- Department of Medicine I, Institute of Cancer Research, Comprehensive Cancer Centre Vienna, Medical University of Vienna, Borschkegasse 8a, A-1090 Vienna, Austria
| | - Istvan Zupko
- Department of Pharmacodynamics and Biopharmacy, University of Szeged, Eötvös u. 6, H-6720 Szeged, Hungary
| | - Ernst Urban
- Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Brigitte Kopp
- Department of Pharmacognosy, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Georg Krupitza
- Department of Clinical Pathology, Medical University of Vienna, Waehringer Guertel 18-20, Austria.
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11
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Giannoutsou E, Galatis B, Zachariadis M, Apostolakos P. Formation of an endoplasmic reticulum ring associated with acetylated microtubules in the angiosperm preprophase band. Cytoskeleton (Hoboken) 2012; 69:252-65. [DOI: 10.1002/cm.21020] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 12/27/2011] [Accepted: 02/10/2012] [Indexed: 01/12/2023]
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12
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Khan M, Giessrigl B, Vonach C, Madlener S, Prinz S, Herbaceck I, Hölzl C, Bauer S, Viola K, Mikulits W, Quereshi RA, Knasmüller S, Grusch M, Kopp B, Krupitza G. Berberine and a Berberis lycium extract inactivate Cdc25A and induce alpha-tubulin acetylation that correlate with HL-60 cell cycle inhibition and apoptosis. Mutat Res 2010; 683:123-30. [PMID: 19909759 DOI: 10.1016/j.mrfmmm.2009.11.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 10/22/2009] [Accepted: 11/02/2009] [Indexed: 11/30/2022]
Abstract
Berberis lycium Royle (Berberidacea) from Pakistan and its alkaloids berberine and palmatine have been reported to possess beneficial pharmacological properties. In the present study, the anti-neoplastic activities of different B. lycium root extracts and the major constituting alkaloids, berberine and palmatine were investigated in p53-deficient HL-60 cells. The strongest growth inhibitory and pro-apoptotic effects were found in the n-butanol (BuOH) extract followed by the ethyl acetate (EtOAc)-, and the water (H(2)O) extract. The chemical composition of the BuOH extract was analyzed by TLC and quantified by HPLC. 11.1 microg BuOH extract (that was gained from 1mg dried root) contained 2.0 microg berberine and 0.3 microg/ml palmatine. 1.2 microg/ml berberine inhibited cell proliferation significantly, while 0.5 microg/ml palmatine had no effect. Berberine and the BuOH extract caused accumulation of HL-60 cells in S-phase. This was preceded by a strong activation of Chk2, phosphorylation and degradation of Cdc25A, and the subsequent inactivation of Cdc2 (CDK1). Furthermore, berberine and the extract inhibited the expression of the proto-oncogene cyclin D1. Berberine and the BuOH extract induced the acetylation of alpha-tubulin and this correlated with the induction of apoptosis. The data demonstrate that berberine is a potent anti-neoplastic compound that acts via anti-proliferative and pro-apoptotic mechanisms independent of genotoxicity.
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Affiliation(s)
- Musa Khan
- Department of Plant Sciences, Quaid-i-Azam University, Islamabad, Pakistan
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13
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Purev E, Neff L, Horne WC, Baron R. c-Cbl and Cbl-b act redundantly to protect osteoclasts from apoptosis and to displace HDAC6 from beta-tubulin, stabilizing microtubules and podosomes. Mol Biol Cell 2009; 20:4021-30. [PMID: 19641021 DOI: 10.1091/mbc.e09-03-0248] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
c-Cbl and Cbl-b are highly conserved adaptor proteins that participate in integrin signaling, regulating cytoskeletal organization, motility, and bone resorption. Deletion of both c-Cbl and Cbl-b in mice leads to embryonic lethality, indicating that the two proteins perform essential redundant functions. To examine the redundant actions of c-Cbl and Cbl-b in osteoclasts, we depleted c-Cbl in Cbl-b(-/-) osteoclasts by using a short hairpin RNA. Depleting both Cbl proteins disrupted both the podosome belt and the microtubule network and decreased bone-resorbing activity. Stabilizing the microtubules with paclitaxel or inhibiting histone deacetylase 6 (HDAC6), which destabilizes microtubules by deacetylating beta-tubulin, protected both the microtubule network and the podosome belt. Examination of the mechanism involved demonstrated that the conserved four-helix bundle of c-Cbl's tyrosine kinase binding domain bound to beta-tubulin, and both c-Cbl and Cbl-b displaced HDAC6. In addition to the effects on microtubules and the podosome belt, depleting both Cbls significantly increased the levels of the proapoptotic protein Bim and apoptosis relative to the levels induced by eliminating either protein alone. Thus, both c-Cbl and Cbl-b promote bone resorption via the stabilization of microtubules, allowing the formation of the podosome belt in osteoclasts, and by promoting osteoclast survival.
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Affiliation(s)
- Enkhtsetseg Purev
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA 02115, USA
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14
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Rathinasamy K, Panda D. Kinetic stabilization of microtubule dynamic instability by benomyl increases the nuclear transport of p53. Biochem Pharmacol 2008; 76:1669-80. [DOI: 10.1016/j.bcp.2008.09.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 08/28/2008] [Accepted: 09/02/2008] [Indexed: 01/26/2023]
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15
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Jordan MA, Horwitz SB, Lobert S, Correia JJ. Exploring the mechanisms of action of the novel microtubule inhibitor vinflunine. Semin Oncol 2008; 35:S6-S12. [PMID: 18538179 DOI: 10.1053/j.seminoncol.2008.01.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Microtubules have been identified as a suitable target for anticancer therapy, primarily based on their biological importance in coordinating chromosomal segregation at mitosis. Two main classes of microtubule-targeted agents, the taxanes and vinca alkaloids, suppress the dynamic behavior of spindle microtubules, inducing mitotic arrest and subsequent apoptotic cell death. Clinical activity of taxanes and first-generation vinca alkaloids in the treatment of solid tumors and hematologic malignancies, respectively, has prompted further research for novel analogs with improved clinical efficacy and safety. Such efforts have led to the development of vinflunine, a bifluorinated vinca alkaloid endowed with unique antitumor properties. Highlighted in this review are the key features of vinflunine that lead to effective suppression of microtubule dynamics and induction of cell death in cancer cells.
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Affiliation(s)
- Mary Ann Jordan
- Department of Molecular, Cellular and Developmental Biology, University of California-Santa Barbara, Santa Barbara, CA 93106, USA.
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Forer A, Pickett-Heaps JD, Spurck T. What generates flux of tubulin in kinetochore microtubules? PROTOPLASMA 2008; 232:137-141. [PMID: 18421550 DOI: 10.1007/s00709-008-0286-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Accepted: 07/10/2007] [Indexed: 05/26/2023]
Abstract
We discuss models for production of tubulin flux in kinetochore microtubules. Current models concentrate solely on microtubules and their associated motors and enzymes. For example, in some models the driving force for flux is enzymes at the poles and the kinetochores; in others the driving force is motor molecules that are associated with a stationary spindle matrix. We present a different viewpoint, that microtubules are propelled poleward by forces arising from the spindle matrix, that the forces on the microtubules "activate" polymerising and depolymerising enzymes at kinetochores and poles, that matrix forces utilise actin, myosin, and microtubule motors, and that the matrix itself may not necessarily be static.
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Affiliation(s)
- Arthur Forer
- Biology Department, York University, Toronto, Ontario, Canada.
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Forer A, Spurck T, Pickett-Heaps JD. Actin and myosin inhibitors block elongation of kinetochore fibre stubs in metaphase crane-fly spermatocytes. PROTOPLASMA 2007; 232:79-85. [PMID: 18094930 DOI: 10.1007/s00709-007-0265-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Accepted: 02/12/2007] [Indexed: 05/25/2023]
Abstract
We used an ultraviolet microbeam to cut individual kinetochore spindle fibres in metaphase crane-fly spermatocytes. We then followed the growth of the "kinetochore stubs", the remnants of kinetochore fibres that remain attached to kinetochores. Kinetochore stubs elongate with constant velocity by adding tubulin subunits at the kinetochore, and thus elongation is related to tubulin flux in the kinetochore microtubules. Stub elongation was blocked by cytochalasin D and latrunculin A, actin inhibitors, and by butanedione monoxime, a myosin inhibitor. We conclude that actin and myosin are involved in generating elongation and thus in producing tubulin flux in kinetochore microtubules. We suggest that actin and myosin act in concert with a spindle matrix to propel kinetochore fibres poleward, thereby causing stub elongation and generating anaphase chromosome movement in nonirradiated cells.
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Affiliation(s)
- A Forer
- Biology Department, York University, Toronto, Ontario, Canada.
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18
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Fabian L, Forer A. Possible roles of actin and myosin during anaphase chromosome movements in locust spermatocytes. PROTOPLASMA 2007; 231:201-213. [PMID: 17922265 DOI: 10.1007/s00709-007-0262-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Accepted: 12/20/2006] [Indexed: 05/25/2023]
Abstract
We tested whether the mechanisms of chromosome movement during anaphase in locust (Locusta migratoria L.) spermatocytes might be similar to those described for crane-fly spermatocytes. Actin and myosin have been implicated in anaphase chromosome movements in crane-fly spermatocytes, as indicated by the effects of inhibitors and by the localisations of actin and myosin in spindles. In this study, we tested whether locust spermatocyte spindles also utilise actin and myosin, and whether actin is involved in microtubule flux. Living locust spermatocytes were treated with inhibitors of actin (latrunculin B and cytochalasin D), myosin (BDM), or myosin phosphorylation (Y-27632 and ML-7). We added drugs (individually) during anaphase. Actin inhibitors alter anaphase: chromosomes either completely stop moving, slow, or sometimes accelerate. The myosin inhibitor, BDM, also alters anaphase: in most cases, the chromosomes drastically slow or stop. ML-7, an inhibitor of MLCK, causes chromosomes to stop, slow, or sometimes accelerate, similar to actin inhibitors. Y-27632, an inhibitor of Rho-kinase, drastically slows or stops anaphase chromosome movements. The effects of the drugs on anaphase movement are reversible: most of the half-bivalents resumed movement at normal speed after these drugs were washed out. Actin and myosin were present in the spindles in locations consistent with their possible involvement in force production. Microtubule flux along kinetochore fibres is an actin-dependent process, since LatB completely removes or drastically reduces the gap in microtubule acetylation at the kinetochore. These results suggest that actin and myosin are involved in anaphase chromosome movements in locust spermatocytes.
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Fabian L, Forer A. Redundant mechanisms for anaphase chromosome movements: crane-fly spermatocyte spindles normally use actin filaments but also can function without them. PROTOPLASMA 2005; 225:169-84. [PMID: 16228898 DOI: 10.1007/s00709-005-0094-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Accepted: 11/04/2004] [Indexed: 05/04/2023]
Abstract
Actin inhibitors block or slow anaphase chromosome movements in crane-fly spermatocytes, but stopping of movement is only temporary; we assumed that cells adapt to loss of actin by switching to mechanism(s) involving only microtubules. To test this, we produced actin-filament-free spindles: we added latrunculin B during prometaphase, 9-80 min before anaphase, after which chromosomes generally moved normally during anaphase. We confirmed the absence of actin filaments by staining with fluorescent phalloidin and by showing that cytochalasin D had no effect on chromosome movement. Thus, actin filaments are involved in normal anaphase movements, but in vivo, spindles nonetheless can function normally without them. We tested whether chromosome movements in actin-filament-free spindles arise via microtubules by challenging such spindles with anti-myosin drugs. Y-27632 and BDM (2,3-butanedione monoxime), inhibitors that affect myosin at different regulatory levels, blocked chromosome movement in normal spindles and in actin-filament-free spindles. We tested whether BDM has side effects on microtubule motors. BDM had no effect on ciliary and sperm motility or on ATPase activity of isolated ciliary axonemes, and thus it does not directly block dynein. Nor does it block kinesin, assayed by a microtubule sliding assay. BDM could conceivably indirectly affect these microtubule motors, though it is unlikely that it would have the same side effect on the motors as Y-27632. Since BDM and Y-27632 both affect chromosome movement in the same way, it would seem that both affect spindle myosin; this suggests that spindle myosin interacts with kinetochore microtubules, either directly or via an intermediate component.
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Affiliation(s)
- Mary Ann Jordan
- University of California Santa Barbara, Santa Barbara, California 93106, USA.
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Forer A, Spurck T, Pickett-Heaps JD, Wilson PJ. Structure of kinetochore fibres in crane-fly spermatocytes after irradiation with an ultraviolet microbeam: Neither microtubules nor actin filaments remain in the irradiated region. ACTA ACUST UNITED AC 2003; 56:173-92. [PMID: 14569597 DOI: 10.1002/cm.10144] [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: 01/10/2023]
Abstract
We studied chromosome movement after kinetochore microtubules were severed. Severing a kinetochore fibre in living crane-fly spermatocytes with an ultraviolet microbeam creates a kinetochore stub, a birefringent remnant of the spindle fibre connected to the kinetochore and extending only to the edge of the irradiated region. After the irradiation, anaphase chromosomes either move poleward led by their stubs or temporarily stop moving. We examined actin and/or microtubules in irradiated cells by means of confocal fluorescence microscopy or serial-section reconstructions from electron microscopy. For each cell thus examined, chromosome movement had been recorded continuously until the moment of fixation. Kinetochore microtubules were completely severed by the ultraviolet microbeam in cells in which chromosomes continued to move poleward after the irradiation: none were seen in the irradiated regions. Similarly, actin filaments normally present in kinetochore fibres were severed by the ultraviolet microbeam irradiations: the irradiated regions contained no actin filaments and only local spots of non-filamentous actin. There was no difference in irradiated regions when the associated chromosomes continued to move versus when they stopped moving. Thus, one cannot explain motion with severed kinetochore microtubules in terms of either microtubules or actin-filaments bridging the irradiated region. The data seem to negate current models for anaphase chromosome movement and support a model in which poleward chromosome movement results from forces generated within the spindle matrix that propel kinetochore fibres or kinetochore stubs poleward.
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Affiliation(s)
- Arthur Forer
- Biology Department, York University, Toronto, Ontario, Canada.
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Wilson PJ, Forer A, Wise D. Microtubule distribution during meiosis I in flea-beetle [Alagoasa (Oedionychus)] spermatocytes: evidence for direct connections between unpaired sex chromosomes. J Cell Sci 2003; 116:1235-47. [PMID: 12615966 DOI: 10.1242/jcs.00296] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The meiosis-I spindle in flea-beetle spermatocytes is unusual in that the autosomes and univalent sex chromosomes are separated by a mitochondrial sheath and move polewards at different times. To help understand the basis for this interesting chromosome behaviour, and to gather more detailed information about it, we studied microtubule distributions throughout meiosis I using immunofluorescence and confocal microscopy, and took careful measurements of pole and kinetochore positions at all stages of division. Our results show that, by late prophase, there is a spindle-shaped cytoplasmic array of microtubules in the central part of the cell, with the nucleus at the periphery. Following nuclear envelope breakdown, both autosomes and sex chromosomes become associated with cytoplasmic microtubules, although only the autosomes move centrally to the 'cytoplasmic spindle'. The two unpaired sex chromosomes remain at the cell periphery and appear to be connected to each other by a microtubule bundle extending between their kinetochores. These bundles often persist into anaphase. Analysis of measurements taken from fixed/stained cells supports previous observations that sex chromosomes move part way to the pole in early prometaphase and then stop. The measurements also suggest that during autosomal anaphase, spindle elongation precedes autosome movement to the poles and polewards movement of sex chromosomes is limited or absent when autosomes are moving polewards.
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Affiliation(s)
- Paula J Wilson
- Biology Department, York University, Toronto, Ontario M3J 1P3, Canada
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Matsuyama A, Shimazu T, Sumida Y, Saito A, Yoshimatsu Y, Seigneurin-Berny D, Osada H, Komatsu Y, Nishino N, Khochbin S, Horinouchi S, Yoshida M. In vivo destabilization of dynamic microtubules by HDAC6-mediated deacetylation. EMBO J 2002; 21:6820-31. [PMID: 12486003 PMCID: PMC139102 DOI: 10.1093/emboj/cdf682] [Citation(s) in RCA: 554] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2002] [Revised: 10/18/2002] [Accepted: 10/29/2002] [Indexed: 11/14/2022] Open
Abstract
Trichostatin A (TSA) inhibits all histone deacetylases (HDACs) of both class I and II, whereas trapoxin (TPX) cannot inhibit HDAC6, a cytoplasmic member of class II HDACs. We took advantage of this differential sensitivity of HDAC6 to TSA and TPX to identify its substrates. Using this approach, alpha-tubulin was identified as an HDAC6 substrate. HDAC6 deacetylated alpha-tubulin both in vivo and in vitro. Our investigations suggest that HDAC6 controls the stability of a dynamic pool of microtubules. Indeed, we found that highly acetylated microtubules observed after TSA treatment exhibited delayed drug-induced depolymerization and that HDAC6 overexpression prompted their induced depolymerization. Depolymerized tubulin was rapidly deacetylated in vivo, whereas tubulin acetylation occurred only after polymerization. We therefore suggest that acetylation and deacetylation are coupled to the microtubule turnover and that HDAC6 plays a key regulatory role in the stability of the dynamic microtubules.
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Affiliation(s)
- Akihisa Matsuyama
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Tadahiro Shimazu
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Yuko Sumida
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Akiko Saito
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Yasuhiro Yoshimatsu
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Daphné Seigneurin-Berny
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Hiroyuki Osada
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Yasuhiko Komatsu
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Norikazu Nishino
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Saadi Khochbin
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Sueharu Horinouchi
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
| | - Minoru Yoshida
- Chemical Genetics Laboratory, Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, CREST Research Project, Japan Science and Technology Corporation, Saitama 332-0012, Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu, Kitakyushu 808-0196, Japan and Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation-INSERM U309, Equipe, Chromatine et Expression des Gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, France Corresponding author e-mail:
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LaFountain JR, Oldenbourg R, Cole RW, Rieder CL. Microtubule flux mediates poleward motion of acentric chromosome fragments during meiosis in insect spermatocytes. Mol Biol Cell 2001; 12:4054-65. [PMID: 11739800 PMCID: PMC60775 DOI: 10.1091/mbc.12.12.4054] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We applied a combination of laser microsurgery and quantitative polarization microscopy to study kinetochore-independent forces that act on chromosome arms during meiosis in crane fly spermatocytes. When chromosome arms located within one of the half-spindles during prometa- or metaphase were cut with the laser, the acentric fragments (lacking kinetochores) that were generated moved poleward with velocities similar to those of anaphase chromosomes (approximately 0.5 microm/min). To determine the mechanism underlying this poleward motion of detached arms, we treated spermatocytes with the microtubule-stabilizing drug taxol. Spindles in taxol-treated cells were noticeably short, yet with polarized light, the distribution and densities of microtubules in domains where fragment movement occurred were not different from those in control cells. When acentric fragments were generated in taxol-treated spermatocytes, 22 of 24 fragments failed to exhibit poleward motion, and the two that did move had velocities attenuated by 80% (to approximately 0.1 microm/min). In these cells, taxol did not inhibit the disjunction of chromosomes nor prevent their poleward segregation during anaphase, but the velocity of anaphase was also decreased 80% (approximately 0.1 microm/min) relative to untreated controls. Together, these data reveal that microtubule flux exerts pole-directed forces on chromosome arms during meiosis in crane fly spermatocytes and strongly suggest that the mechanism underlying microtubule flux also is used in the anaphase motion of kinetochores in these cells.
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Affiliation(s)
- J R LaFountain
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA.
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25
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Pickett-Heaps JD, Forer A. Pac-Man does not resolve the enduring problem of anaphase chromosome movement. PROTOPLASMA 2001; 215:16-20. [PMID: 11732055 DOI: 10.1007/bf01280300] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The Pac-Man hypothesis suggests that poleward movement of chromosomes during anaphase A is brought about by: disassembly of kinetochore microtubules (MTs) at the kinetochore; generation of the poleward force exclusively at or very close to the kinetochore; and the required energy coming from coupled disassembly of these MTs. This model has become widely accepted and cited as the sole or major mechanism of anaphase A. Rarely acknowledged are several significant phenomena that refute some or all of these postulates. We summarise these anomalies as follows: poleward movement of chromosomes occurring without insertion of any MTs at the kinetochore; "anaphase" shortening of kinetochore fibres in spindles entirely devoid of chromosomes and, presumably, kinetochores; continued movement of chromosomes while their severed kinetochore stub elongated poleward after treatment with UV microbeams; and fluxing of tubulin subunits through kinetochore MTs during anaphase A, indicating that during anaphase, kinetochore MTs disassemble partly or solely at the poles.
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Affiliation(s)
- J D Pickett-Heaps
- School of Botany, University of Melbourne, Parkville, Victoria, 3052, Australia
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26
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Forer A, Wilson PJ. Evidence that kinetochore fibre microtubules shorten predominantly at the pole in anaphase flea-beetle spermatocytes. Chromosome Res 2000; 8:151-63. [PMID: 10780704 DOI: 10.1023/a:1009298620707] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Kinetochore spindle fibres in flea-beetle metaphase primary spermatocytes have two regions with distinct morphologies. As seen after staining with antibodies against tubulin, the kinetochore microtubules are tightly bundled in the 5 microm closest to the kinetochore but they splay out in the region closest to the pole. This morphology persists throughout anaphase. This distinct morphology allows one to deduce the site where kinetochore microtubules depolymerise during anaphase. During poleward movement of the autosomes in anaphase, the bundled region shortens by about 0.25 microm for each 1 microm the chromosome moves poleward; this suggests that, during anaphase, 75% of the kinetochore microtubule shortening occurs at the pole end. Sex chromosomes in metaphase cells are separated from the autosomes and do not move poleward at the same time as the autosomes: they are reported to move poleward when the autosomes are in metaphase, to stop part way to the poles, and to move poleward again as the autosomes do (Virkki 1970). Kinetochore microtubules of the sex chromosomes also have bundled and splayed regions; measurements of those regions suggest that these chromosomes may move poleward before the autosomes enter anaphase, but not afterwards.
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Affiliation(s)
- A Forer
- Biology Department, York University, North York, Ontario, Canada.
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27
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Silverman-Gavrila RV, Forer A. Evidence that actin and myosin are involved in the poleward flux of tubulin in metaphase kinetochore microtubules of crane-fly spermatocytes. J Cell Sci 2000; 113 ( Pt 4):597-609. [PMID: 10652253 DOI: 10.1242/jcs.113.4.597] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
We studied the effects of various drugs on the poleward flux of tubulin in kinetochore microtubules in metaphase-I crane-fly spermatocytes. We used as a measure of tubulin flux a ‘gap’ in acetylation of kinetochore microtubules immediately poleward from the kinetochore; the ‘gap’ is caused by a time lag between incorporation of new tubulin subunits at the kinetochore and subsequent acetylation of those subunits as they flux to the pole. We confirmed that the ‘gap’ is due to flux by showing that the ‘gap’ disappeared when cells were treated briefly with the anti-tubulin drug nocodazole, which decreases microtubule dynamics. The ‘gap’ disappeared when cells were treated for 10 minutes with anti-actin drugs (cytochalasin D, latrunculin B, swinholide A), or with the anti-myosin drug 2,3-butanedione 2-monoxime. The ‘gap’ did not disappear when cells were treated with the actin stabilizing drug jasplakinolide. We studied whether these drugs altered spindle actin. We used fluorescent phalloidin to visualize spermatocyte F-actin, which was associated with kinetochore spindle fibers as well as the cell cortex, the contractile ring and finger-like protrusions at the poles. Spindle F-actin was no longer seen after cells were treated with cytochalasin D, swinholide A or a high concentration of latrunculin B, whereas a low concentration of latrunculin B, which did not completely remove the ‘gap’, caused reduced staining of spindle actin. Neither 2,3-butanedione 2-monoxime nor jasplakinolide altered spindle actin. These data suggest that an actomyosin mechanism drives the metaphase poleward tubulin flux.
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28
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Matthies HJ, Messina LG, Namba R, Greer KJ, Walker M, Hawley RS. Mutations in the alpha-tubulin 67C gene specifically impair achiasmate segregation in Drosophila melanogaster. J Cell Biol 1999; 147:1137-44. [PMID: 10601329 PMCID: PMC2168102 DOI: 10.1083/jcb.147.6.1137] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [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
Drosophila melanogaster oocytes heterozygous for mutations in the alpha-tubulin 67C gene (alphatub67C) display defects in centromere positioning during prometaphase of meiosis I. The centromeres do not migrate to the poleward edges of the chromatin mass, and the chromatin fails to stretch during spindle lengthening. These results suggest that the poleward forces acting at the kinetochore are compromised in the alphatub67C mutants. Genetic studies demonstrate that these mutations also strongly and specifically decrease the fidelity of achiasmate chromosome segregation. Proper centromere orientation, chromatin elongation, and faithful segregation can all be restored by a decrease in the amount of the Nod chromokinesin. These results suggest that the accurate segregation of achiasmate chromosomes requires the proper balancing of forces acting on the chromosomes during prometaphase.
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Affiliation(s)
- Heinrich J.G. Matthies
- Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616
| | - Lisa G. Messina
- Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616
| | - Ruria Namba
- Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616
| | - Kimberly J. Greer
- Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616
| | - M.Y. Walker
- Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616
| | - R. Scott Hawley
- Department of Genetics, Section of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616
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Abstract
A high-resolution model of the microtubule has been obtained by docking the crystal structure of tubulin into a 20 A map of the microtubule. The excellent fit indicates the similarity of the tubulin conformation in both polymers and defines the orientation of the tubulin structure within the microtubule. Long C-terminal helices form the crest on the outside of the protofilament, while long loops define the microtubule lumen. The exchangeable nucleotide in beta-tubulin is exposed at the plus end of the microtubule, while the proposed catalytic residue in alpha-tubulin is exposed at the minus end. Extensive longitudinal interfaces between monomers have polar and hydrophobic components. At the lateral contacts, a nucleotide-sensitive helix interacts with a loop that contributes to the binding site of taxol in beta-tubulin.
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Affiliation(s)
- E Nogales
- Lawrence Berkeley National Laboratory, Molecular and Cell Biology Department, University of California at Berkeley, California 94720, USA.
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