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Staphylococcus aureus isolates from hospital clinics induce ROS-mediated DNA damage, apoptosis and gene expression alterations in male mice. GENE REPORTS 2021. [DOI: 10.1016/j.genrep.2021.101028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Staphylococcus aureus Internalization in Osteoblast Cells: Mechanisms, Interactions and Biochemical Processes. What Did We Learn from Experimental Models? Pathogens 2021; 10:pathogens10020239. [PMID: 33669789 PMCID: PMC7922271 DOI: 10.3390/pathogens10020239] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/12/2021] [Accepted: 02/17/2021] [Indexed: 02/07/2023] Open
Abstract
Bacterial internalization is a strategy that non-intracellular microorganisms use to escape the host immune system and survive inside the human body. Among bacterial species, Staphylococcus aureus showed the ability to interact with and infect osteoblasts, causing osteomyelitis as well as bone and joint infection, while also becoming increasingly resistant to antibiotic therapy and a reservoir of bacteria that can make the infection difficult to cure. Despite being a serious issue in orthopedic surgery, little is known about the mechanisms that allow bacteria to enter and survive inside the osteoblasts, due to the lack of consistent experimental models. In this review, we describe the current knowledge about S. aureus internalization mechanisms and various aspects of the interaction between bacteria and osteoblasts (e.g., best experimental conditions, bacteria-induced damages and immune system response), focusing on studies performed using the MG-63 osteoblastic cell line, the best traditional (2D) model for the study of this phenomenon to date. At the same time, as it has been widely demonstrated that 2D culture systems are not completely indicative of the dynamic environment in vivo, and more recent 3D models—representative of bone infection—have also been investigated.
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3
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Deplanche M, Mouhali N, Nguyen MT, Cauty C, Ezan F, Diot A, Raulin L, Dutertre S, Langouet S, Legembre P, Taieb F, Otto M, Laurent F, Götz F, Le Loir Y, Berkova N. Staphylococcus aureus induces DNA damage in host cell. Sci Rep 2019; 9:7694. [PMID: 31118484 PMCID: PMC6531466 DOI: 10.1038/s41598-019-44213-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 05/09/2019] [Indexed: 12/15/2022] Open
Abstract
Staphylococcus aureus causes serious medical problems in human and animals. Here we show that S. aureus can compromise host genomic integrity as indicated by bacteria-induced histone H2AX phosphorylation, a marker of DNA double strand breaks (DSBs), in human cervix cancer HeLa and osteoblast-like MG-63 cells. This DNA damage is mediated by alpha phenol-soluble modulins (PSMα1–4), while a specific class of lipoproteins (Lpls), encoded on a pathogenicity island in S. aureus, dampens the H2AX phosphorylation thus counteracting the DNA damage. This DNA damage is mediated by reactive oxygen species (ROS), which promotes oxidation of guanine forming 7,8-dihydro-8-oxoguanine (8-oxoG). DNA damage is followed by the induction of DNA repair that involves the ATM kinase-signaling pathway. An examination of S. aureus strains, isolated from the same patient during acute initial and recurrent bone and joint infections (BJI), showed that recurrent strains produce lower amounts of Lpls, induce stronger DNA-damage and prompt the G2/M transition delay to a greater extent that suggest an involvement of these mechanisms in adaptive processes of bacteria during chronicization. Our findings redefine our understanding of mechanisms of S. aureus-host interaction and suggest that the balance between the levels of PSMα and Lpls expression impacts the persistence of the infection.
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Affiliation(s)
| | | | - Minh-Thu Nguyen
- Microbial Genetics, University of Tübingen, Tübingen, Germany
| | | | - Frédéric Ezan
- Univ Rennes, Inserm, EHESP, Irset UMR_S 1085, F-35000, Rennes, France
| | - Alan Diot
- Centre International de Recherche en Infectiologie, INSERM U1111, CNRS, Université Lyon 1, Lyon, France.,Centre National de Référence des Staphylocoques, Lyon, France
| | - Lesly Raulin
- CNRS, Inserm, BIOSIT-UMS 3480, MRic, Université de Rennes, Rennes, France
| | - Stephanie Dutertre
- CNRS, Inserm, BIOSIT-UMS 3480, MRic, Université de Rennes, Rennes, France
| | - Sophie Langouet
- Univ Rennes, Inserm, EHESP, Irset UMR_S 1085, F-35000, Rennes, France
| | - Patrick Legembre
- Centre Eugène Marquis, Equipe Ligue Contre Le Cancer, Rennes, France
| | - Frederic Taieb
- IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France
| | - Michael Otto
- Laboratory of Human Bacterial Pathogenesis, US National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Frédéric Laurent
- Centre International de Recherche en Infectiologie, INSERM U1111, CNRS, Université Lyon 1, Lyon, France.,Centre National de Référence des Staphylocoques, Lyon, France
| | - Friedrich Götz
- Microbial Genetics, University of Tübingen, Tübingen, Germany
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Soong YHV, Liu N, Yoon S, Lawton C, Xie D. Cellular and metabolic engineering of oleaginous yeast Yarrowia lipolytica for bioconversion of hydrophobic substrates into high-value products. Eng Life Sci 2019; 19:423-443. [PMID: 32625020 DOI: 10.1002/elsc.201800147] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 12/12/2018] [Accepted: 02/07/2019] [Indexed: 12/17/2022] Open
Abstract
The non-conventional oleaginous yeast Yarrowia lipolytica is able to utilize both hydrophilic and hydrophobic carbon sources as substrates and convert them into value-added bioproducts such as organic acids, extracellular proteins, wax esters, long-chain diacids, fatty acid ethyl esters, carotenoids and omega-3 fatty acids. Metabolic pathway analysis and previous research results show that hydrophobic substrates are potentially more preferred by Y. lipolytica than hydrophilic substrates to make high-value products at higher productivity, titer, rate, and yield. Hence, Y. lipolytica is becoming an efficient and promising biomanufacturing platform due to its capabilities in biosynthesis of extracellular lipases and directly converting the extracellular triacylglycerol oils and fats into high-value products. It is believed that the cell size and morphology of the Y. lipolytica is related to the cell growth, nutrient uptake, and product formation. Dimorphic Y. lipolytica demonstrates the yeast-to-hypha transition in response to the extracellular environments and genetic background. Yeast-to-hyphal transition regulating genes, such as YlBEM1, YlMHY1 and YlZNC1 and so forth, have been identified to involve as major transcriptional factors that control morphology transition in Y. lipolytica. The connection of the cell polarization including cell cycle and the dimorphic transition with the cell size and morphology in Y. lipolytica adapting to new growth are reviewed and discussed. This review also summarizes the general and advanced genetic tools that are used to build a Y. lipolytica biomanufacturing platform.
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Affiliation(s)
- Ya-Hue Valerie Soong
- Massachusetts Biomanufacturing Center Department of Chemical Engineering University of Massachusetts Lowell Lowell MA USA
| | - Na Liu
- Massachusetts Biomanufacturing Center Department of Chemical Engineering University of Massachusetts Lowell Lowell MA USA
| | - Seongkyu Yoon
- Massachusetts Biomanufacturing Center Department of Chemical Engineering University of Massachusetts Lowell Lowell MA USA
| | - Carl Lawton
- Massachusetts Biomanufacturing Center Department of Chemical Engineering University of Massachusetts Lowell Lowell MA USA
| | - Dongming Xie
- Massachusetts Biomanufacturing Center Department of Chemical Engineering University of Massachusetts Lowell Lowell MA USA
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5
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Wang X, Tanaka M, Peixoto HS, Wink M. Cucurbitacins: elucidation of their interactions with the cytoskeleton. PeerJ 2017; 5:e3357. [PMID: 28584704 PMCID: PMC5452965 DOI: 10.7717/peerj.3357] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 04/26/2017] [Indexed: 01/25/2023] Open
Abstract
Cucurbitacins, a class of toxic tetracyclic triterpenoids in Cucurbitaceae, modulate many molecular targets. Here we investigated the interactions of cucurbitacin B, E and I with cytoskeletal proteins such as microtubule and actin filaments. The effects of cucurbitacin B, E and I on microtubules and actin filaments were studied in living cells (Hela and U2OS) and in vitro using GFP markers, immunofluorescence staining and in vitro tubulin polymerization assay. Cucurbitacin B, E and I apparently affected microtubule structures in living cells and cucurbitacin E inhibited tubulin polymerization in vitro with IC50 value of 566.91 ± 113.5 µM. Cucurbitacin E did not affect the nucleation but inhibited the growth phase and steady state during microtubule assembly in vitro. In addition, cucurbitacin B, E and I all altered mitotic spindles and induced the cell cycle arrest at G2/M phase. Moreover, they all showed potent effects on actin cytoskeleton by affecting actin filaments through the depolymerization and aggregation. The interactions of cucubitacin B, E and I with microtubules and actin filaments present new insights into their modes of action.
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Affiliation(s)
- Xiaojuan Wang
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
| | - Mine Tanaka
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
| | - Herbenya Silva Peixoto
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
| | - Michael Wink
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
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6
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Role of potassium channels in chlorogenic acid-induced apoptotic volume decrease and cell cycle arrest in Candida albicans. Biochim Biophys Acta Gen Subj 2017; 1861:585-592. [DOI: 10.1016/j.bbagen.2016.12.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 12/20/2016] [Accepted: 12/26/2016] [Indexed: 11/20/2022]
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7
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Wang X, Tanaka M, Krstin S, Peixoto HS, Moura CCDM, Wink M. Cytoskeletal interference - A new mode of action for the anticancer drugs camptothecin and topotecan. Eur J Pharmacol 2016; 789:265-274. [PMID: 27474470 DOI: 10.1016/j.ejphar.2016.07.044] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 07/26/2016] [Accepted: 07/26/2016] [Indexed: 11/24/2022]
Abstract
The anticancer drugs camptothecin (CPT) and topotecan (TPT) are known DNA topoisomerase I inhibitors which cause DNA damage and lead to cell death. In this study we provide evidence that CPT and TPT also interfere with the elements of cytoskeleton - microtubules and actin filaments which could be partly responsible for their cytotoxic properties. CPT and TPT apparently affected microtubule structures in living cells (Hela and U2OS) and inhibited tubulin polymerization in vitro with IC50 values of 74.57±9.96µM and 121.55±58.68µM, respectively. TPT significantly affected the nucleation and growth phase during the microtubule assembly in vitro, whereas the mode of action of CPT was different in that it specifically affected the 'tread milling' of polymerized microtubules. Cell cycle effects of CPT and TPT varied with their concentrations. CPT and TPT induced G2/M arrest and promoted the population to 76.94±11.20% and 83.91±2.43% at a concentration of 9.4nM and 46.9nM, respectively. As the concentration increased, cells were blocked in S phase with a dose-dependent reduction in G2/M population. In addition, CPT and TPT exhibited a certain effect on actin filaments by reducing the mass of actin filaments. The interactions of CPT and TPT with microtubules and actin filaments present new insights into their modes of action.
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Affiliation(s)
- Xiaojuan Wang
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany.
| | - Mine Tanaka
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany.
| | - Sonja Krstin
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany.
| | - Herbenya Silva Peixoto
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany.
| | - Carina Carneiro de Melo Moura
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany.
| | - Michael Wink
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany.
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8
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Wang X, Tanaka M, Krstin S, Peixoto HS, Wink M. The Interference of Selected Cytotoxic Alkaloids with the Cytoskeleton: An Insight into Their Modes of Action. Molecules 2016; 21:E906. [PMID: 27420038 PMCID: PMC6273799 DOI: 10.3390/molecules21070906] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 07/05/2016] [Accepted: 07/06/2016] [Indexed: 02/01/2023] Open
Abstract
Alkaloids, the largest group among the nitrogen-containing secondary metabolites of plants, usually interact with several molecular targets. In this study, we provide evidence that six cytotoxic alkaloids (sanguinarine, chelerythrine, chelidonine, noscapine, protopine, homoharringtonine), which are known to affect neuroreceptors, protein biosynthesis and nucleic acids, also interact with the cellular cytoskeleton, such as microtubules and actin filaments, as well. Sanguinarine, chelerythrine and chelidonine depolymerized the microtubule network in living cancer cells (Hela cells and human osteosarcoma U2OS cells) and inhibited tubulin polymerization in vitro with IC50 values of 48.41 ± 3.73, 206.39 ± 4.20 and 34.51 ± 9.47 μM, respectively. However, sanguinarine and chelerythrine did not arrest the cell cycle while 2.5 μM chelidonine arrested the cell cycle in the G₂/M phase with 88.27% ± 0.99% of the cells in this phase. Noscapine and protopine apparently affected microtubule structures in living cells without affecting tubulin polymerization in vitro, which led to cell cycle arrest in the G2/M phase, promoting this cell population to 73.42% ± 8.31% and 54.35% ± 11.26% at a concentration of 80 μM and 250.9 μM, respectively. Homoharringtonine did not show any effects on microtubules and cell cycle, while the known microtubule-stabilizing agent paclitaxel was found to inhibit tubulin polymerization in the presence of MAPs in vitro with an IC50 value of 38.19 ± 3.33 μM. Concerning actin filaments, sanguinarine, chelerythrine and chelidonine exhibited a certain effect on the cellular actin filament network by reducing the mass of actin filaments. The interactions of these cytotoxic alkaloids with microtubules and actin filaments present new insights into their molecular modes of action.
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Affiliation(s)
- Xiaojuan Wang
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, INF 364, D-69120 Heidelberg, Germany.
| | - Mine Tanaka
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, INF 364, D-69120 Heidelberg, Germany.
| | - Sonja Krstin
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, INF 364, D-69120 Heidelberg, Germany.
| | - Herbenya Silva Peixoto
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, INF 364, D-69120 Heidelberg, Germany.
| | - Michael Wink
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, INF 364, D-69120 Heidelberg, Germany.
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9
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Horváth A, Rácz-Mónus A, Buchwald P, Sveiczer Á. Cell length growth patterns in fission yeast reveal a novel size control mechanism operating in late G2 phase. Biol Cell 2016; 108:259-77. [DOI: 10.1111/boc.201500066] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 04/05/2016] [Indexed: 02/03/2023]
Affiliation(s)
- Anna Horváth
- Department of Applied Biotechnology and Food Science; Budapest University of Technology and Economics; Budapest Hungary
| | - Anna Rácz-Mónus
- Department of Applied Biotechnology and Food Science; Budapest University of Technology and Economics; Budapest Hungary
| | - Peter Buchwald
- Department of Molecular and Cellular Pharmacology; Miller School of Medicine; University of Miami; Miami FL USA
| | - Ákos Sveiczer
- Department of Applied Biotechnology and Food Science; Budapest University of Technology and Economics; Budapest Hungary
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10
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Gismondi A, Nanni V, Reina G, Orlanducci S, Terranova ML, Canini A. Nanodiamonds coupled with 5,7-dimethoxycoumarin, a plant bioactive metabolite, interfere with the mitotic process in B16F10 cells altering the actin organization. Int J Nanomedicine 2016; 11:557-74. [PMID: 26893562 PMCID: PMC4745844 DOI: 10.2147/ijn.s96614] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
For the first time, we coupled reduced detonation nanodiamonds (NDs) with a plant secondary metabolite, citropten (5,7-dimethoxycoumarin), and demonstrated how this complex was able to reduce B16F10 tumor cell growth more effectively than treatment with the pure molecule. These results encouraged us to find out the specific mechanism underlying this phenomenon. Internalization kinetics and quantification of citropten in cells after treatment with its pure or ND-conjugated form were measured, and it was revealed that the coupling between NDs and citropten was essential for the biological properties of the complex. We showed that the adduct was not able to induce apoptosis, senescence, or differentiation, but it determined cell cycle arrest, morphological changes, and alteration of mRNA levels of the cytoskeletal-related genes. The identification of metaphasic nuclei and irregular disposition of β-actin in the cell cytoplasm supported the hypothesis that citropten conjugated with NDs showed antimitotic properties in B16F10 cells. This work can be considered a pioneering piece of research that could promote and support the biomedical use of plant drug-functionalized NDs in cancer therapy.
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Affiliation(s)
- Angelo Gismondi
- Department of Biology, University of Rome "Tor Vergata", Rome, Italy
| | - Valentina Nanni
- Department of Biology, University of Rome "Tor Vergata", Rome, Italy
| | - Giacomo Reina
- Department of Chemical Science and Technology, University of Rome "Tor Vergata", Rome, Italy
| | - Silvia Orlanducci
- Department of Chemical Science and Technology, University of Rome "Tor Vergata", Rome, Italy
| | - Maria Letizia Terranova
- Department of Chemical Science and Technology, University of Rome "Tor Vergata", Rome, Italy
| | - Antonella Canini
- Department of Biology, University of Rome "Tor Vergata", Rome, Italy
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11
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The tethering of chromatin to the nuclear envelope supports nuclear mechanics. Nat Commun 2015; 6:7159. [PMID: 26074052 PMCID: PMC4490570 DOI: 10.1038/ncomms8159] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 04/10/2015] [Indexed: 12/23/2022] Open
Abstract
The nuclear lamina is thought to be the primary mechanical defence of the nucleus. However, the lamina is integrated within a network of lipids, proteins and chromatin; the interdependence of this network poses a challenge to defining the individual mechanical contributions of these components. Here, we isolate the role of chromatin in nuclear mechanics by using a system lacking lamins. Using novel imaging analyses, we observe that untethering chromatin from the inner nuclear membrane results in highly deformable nuclei in vivo, particularly in response to cytoskeletal forces. Using optical tweezers, we find that isolated nuclei lacking inner nuclear membrane tethers are less stiff than wild-type nuclei and exhibit increased chromatin flow, particularly in frequency ranges that recapitulate the kinetics of cytoskeletal dynamics. We suggest that modulating chromatin flow can define both transient and long-lived changes in nuclear shape that are biologically important and may be altered in disease. The mechanical properties of the metazoan nucleus can be influenced by the nuclear lamina. Here, Schreiner et al. show that untethering chromatin from the inner nuclear membrane results in highly deformable, softer nuclei, revealing an important role for chromatin in modulating nuclear mechanics.
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Abstract
Discoveries in cytogenetics, molecular biology, and genomics have revealed that genome change is an active cell-mediated physiological process. This is distinctly at variance with the pre-DNA assumption that genetic changes arise accidentally and sporadically. The discovery that DNA changes arise as the result of regulated cell biochemistry means that the genome is best modelled as a read-write (RW) data storage system rather than a read-only memory (ROM). The evidence behind this change in thinking and a consideration of some of its implications are the subjects of this article. Specific points include the following: cells protect themselves from accidental genome change with proofreading and DNA damage repair systems; localized point mutations result from the action of specialized trans-lesion mutator DNA polymerases; cells can join broken chromosomes and generate genome rearrangements by non-homologous end-joining (NHEJ) processes in specialized subnuclear repair centres; cells have a broad variety of natural genetic engineering (NGE) functions for transporting, diversifying and reorganizing DNA sequences in ways that generate many classes of genomic novelties; natural genetic engineering functions are regulated and subject to activation by a range of challenging life history events; cells can target the action of natural genetic engineering functions to particular genome locations by a range of well-established molecular interactions, including protein binding with regulatory factors and linkage to transcription; and genome changes in cancer can usefully be considered as consequences of the loss of homeostatic control over natural genetic engineering functions.
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Affiliation(s)
- James A Shapiro
- Department of Biochemistry and Molecular Biology, University of Chicago, GCISW123B, 979 E. 57th Street, Chicago, IL 60637, USA
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13
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Ahn YT, Shin IJ, Kim JM, Kim YS, Lee C, Ju SA, An WG. Counteracting the activation of pAkt by inhibition of MEK/Erk inhibition reduces actin disruption-mediated apoptosis in PTEN-null PC3M prostate cancer cell lines. Oncol Lett 2013; 6:1383-1389. [PMID: 24179529 PMCID: PMC3813806 DOI: 10.3892/ol.2013.1547] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 08/12/2013] [Indexed: 11/06/2022] Open
Abstract
The actin cytoskeleton is important in the maintenance of cellular homeostasis and in signal transduction pathways leading to cell growth and apoptotic cell death in eukaryotic cells. Disruption of actin dynamics is associated with morphological changes in cancer cells. Deletion of phosphatase and tensin homolog (PTEN), a tumor suppressor gene involved in the regulation of the cell cycle and apoptosis, leads to cytoskeleton disruption and double-strand breaks (DSBs). To study the mechanism(s) of actin disruption-mediated apoptosis and its potential application for anticancer therapy, PTEN-null PC3M prostate cancer cells were treated with latrunculin B (LB). LB induced destabilization of the actin microfilament and apoptosis in a dose-dependent manner, as demonstrated by morphological changes and nuclear condensation in the PC3M cells. In addition, it resulted in an increase in the levels of γH2AX recruitment, implicating the induction of DNA damage, including DSBs. Induction of Bax, with little effect on Bcl-2 expression, indicated that actin disruption causes apoptosis through activation of Bax signaling in PC3M cells. Treatment with U20126, a mitogen-activated protein kinase kinase (MEK) inhibitor, resulted in attenuated induction of DSBs and apoptosis through activation of protein kinase B (Akt), suggesting that LB-mediated actin dysfunction induces DSBs via the MEK/extracellular signal-regulated kinase (Erk) pathway in cells. Therefore, counteracting activation of phosphorylated Akt stemming from the inhibition of MEK/Erk resulted in attenuation of actin disruption-induced apoptotic events in the PC3M cells. The results of this study provide information not only for use in delineation of the molecular association between actin disruption and tumorigenesis, but also for the development of a strategy for actin-based anticancer chemotherapy against highly metastatic prostate cancer.
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Affiliation(s)
- Yong-Tae Ahn
- Department of Biomedical Science, Kyungdong University, Goseong-gun, Gangwon-do 219-832, Republic of Korea
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14
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Robust cell size checkpoint from spatiotemporal positive feedback loop in fission yeast. BIOMED RESEARCH INTERNATIONAL 2013; 2013:910941. [PMID: 23957011 PMCID: PMC3728729 DOI: 10.1155/2013/910941] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 06/07/2013] [Indexed: 11/17/2022]
Abstract
Cells must maintain appropriate cell size during proliferation. Size control may be regulated by a size checkpoint that couples cell size to cell division. Biological experimental data suggests that the cell size is coupled to the cell cycle in two ways: the rates of protein synthesis and the cell polarity protein kinase Pom1 provide spatial information that is used to regulate mitosis inhibitor Wee1. Here a mathematical model involving these spatiotemporal regulations was developed and used to explore the mechanisms underlying the size checkpoint in fission yeast. Bifurcation analysis shows that when the spatiotemporal regulation is coupled to the positive feedback loops (active Cdc2 promotes its activator, Cdc25, and suppress its inhibitor, Wee1), the mitosis-promoting factor (MPF) exhibits a bistable steady-state relationship with the cell size. The switch-like response from the positive feedback loops naturally generates the cell size checkpoint. Further analysis indicated that the spatial regulation provided by Pom1 enhances the robustness of the size checkpoint in fission yeast. This was consistent with experimental data.
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15
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Horváth A, Rácz-Mónus A, Buchwald P, Sveiczer Á. Cell length growth in fission yeast: an analysis of its bilinear character and the nature of its rate change transition. FEMS Yeast Res 2013; 13:635-49. [DOI: 10.1111/1567-1364.12064] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 06/20/2013] [Accepted: 07/04/2013] [Indexed: 11/27/2022] Open
Affiliation(s)
- Anna Horváth
- Department of Applied Biotechnology and Food Science; Budapest University of Technology and Economics; Budapest; Hungary
| | - Anna Rácz-Mónus
- Department of Applied Biotechnology and Food Science; Budapest University of Technology and Economics; Budapest; Hungary
| | - Peter Buchwald
- Department of Molecular and Cellular Pharmacology and Diabetes Research Institute; Miller School of Medicine; University of Miami; Miami; FL; USA
| | - Ákos Sveiczer
- Department of Applied Biotechnology and Food Science; Budapest University of Technology and Economics; Budapest; Hungary
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16
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Linkers of cell polarity and cell cycle regulation in the fission yeast protein interaction network. PLoS Comput Biol 2012; 8:e1002732. [PMID: 23093924 PMCID: PMC3475659 DOI: 10.1371/journal.pcbi.1002732] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 08/21/2012] [Indexed: 11/19/2022] Open
Abstract
The study of gene and protein interaction networks has improved our understanding of the multiple, systemic levels of regulation found in eukaryotic and prokaryotic organisms. Here we carry out a large-scale analysis of the protein-protein interaction (PPI) network of fission yeast (Schizosaccharomyces pombe) and establish a method to identify ‘linker’ proteins that bridge diverse cellular processes - integrating Gene Ontology and PPI data with network theory measures. We test the method on a highly characterized subset of the genome consisting of proteins controlling the cell cycle, cell polarity and cytokinesis and identify proteins likely to play a key role in controlling the temporal changes in the localization of the polarity machinery. Experimental inspection of one such factor, the polarity-regulating RNB protein Sts5, confirms the prediction that it has a cell cycle dependent regulation. Detailed bibliographic inspection of other predicted ‘linkers’ also confirms the predictive power of the method. As the method is robust to network perturbations and can successfully predict linker proteins, it provides a powerful tool to study the interplay between different cellular processes. Analysis of protein interaction networks has been of use as a means to grapple with the complexity of the interactome of biological organisms. So far, network based approaches have only been used in a limited number of organisms due to the lack of high-throughput experiments. In this study, we investigate by graph theoretical network analysis approaches the protein-protein interaction network of fission yeast, and present a new network measure, linkerity, that predicts the ability of certain proteins to function as bridges between diverse cellular processes. We apply this linkerity measure to a highly conserved and coupled subset of the fission yeast network, consisting of the proteins that regulate cell cycle, polarized cell growth, and cell division. In depth literature analysis confirms that several proteins identified as linkers of cell polarity regulation are indeed also associated with cell cycle and/or cell division control. Similarly, experimental testing confirms that a mostly uncharacterized polarity regulator identified by the method as an important linker is regulated by the cell cycle, as predicted.
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Karagiannis J. Ensuring the faithful execution of cytokinesis in Schizosaccharomyces pombe. Commun Integr Biol 2012; 5:265-71. [PMID: 22896789 PMCID: PMC3419111 DOI: 10.4161/cib.19860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Eukaryotic cells ensure error-free progress through the cell cycle by monitoring (1) the completion of cell cycle events, (2) damage to critical cellular components, or (3) structural changes such as the attachment of kinetochores to the mitotic spindle. In the presence of damage, or in the face of a reduced capacity to complete essential events, cells are capable of delaying the cell cycle so that damage can be repaired, or previous cell cycle phases can proceed to completion. Although such “checkpoints” have been extensively studied in many organisms—and much is understood with respect to the monitoring of DNA replication and DNA damage—little is known with regards to mechanisms that might monitor the completion of cytokinesis. In this review I summarize recent work from the fission yeast, Schizosaccharomyces pombe, describing the existence of regulatory modules that aid in ensuring the faithful and reliable execution of cytokinesis. Together, these modules promote the maintenance of a “cytokinesis-competent” state characterized by delayed progression into mitosis and the continuous repair and/or re-establishment of the acto-myosin ring. In this way, fission yeast cells are able to increase the likelihood of successful cell division prior to committing to a subsequent cell cycle. The recent demonstration of conservation between S. pombe components of these modules, and human proteins with defined roles in preventing cell division failure, suggest that the lessons learned in S. pombe may be applicable to other eukaryotes.
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Affiliation(s)
- Jim Karagiannis
- Department of Biology; University of Western Ontario; London, ON Canada
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18
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Hansjakob A, Riederer M, Hildebrandt U. Appressorium morphogenesis and cell cycle progression are linked in the grass powdery mildew fungus Blumeria graminis. Fungal Biol 2012; 116:890-901. [DOI: 10.1016/j.funbio.2012.05.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 05/02/2012] [Accepted: 05/30/2012] [Indexed: 12/28/2022]
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Abstract
Cell size is an important adaptive trait that influences nearly all aspects of cellular physiology. Despite extensive characterization of the cell-cycle regulatory network, the molecular mechanisms coupling cell growth to division, and thereby controlling cell size, have remained elusive. Recent work in yeast has reinvigorated the size control field and suggested provocative mechanisms for the distinct functions of setting and sensing cell size. Further examination of size-sensing models based on spatial gradients and molecular titration, coupled with elucidation of the pathways responsible for nutrient-modulated target size, may reveal the fundamental principles of eukaryotic cell size control.
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Azarin SM, Larson EA, Almodóvar-Cruz JM, de Pablo JJ, Palecek SP. Effects of 3D microwell culture on growth kinetics and metabolism of human embryonic stem cells. Biotechnol Appl Biochem 2012; 59:88-96. [PMID: 23586789 PMCID: PMC3628806 DOI: 10.1002/bab.1003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 01/18/2012] [Indexed: 11/07/2022]
Abstract
Human embryonic stem cells (hESCs) hold potential in the field of tissue engineering, given their capacity for both limitless self-renewal and differentiation to any adult cell type. However, several limitations, including the ability to expand undifferentiated cells and efficiently direct differentiation at scales needed for commercial cell production, prevent realizing the potential of hESCs in tissue engineering. Numerous studies have illustrated that three-dimensional (3D) culture systems provide microenvironmental cues that affect hESC pluripotency and differentiation fates, but little is known about how 3D culture affects cell expansion. Here, we have used a 3D microwell array to model the differences in hESC growth kinetics and metabolism in two-dimensional (2D) versus 3D cultures. Our results demonstrated that 3D microwell culture reduced hESC size and proliferative capacity, and impacted cell cycle dynamics, lengthening the G1 phase and shortening the G2/M phase of the cell cycle. However, glucose and lactate metabolism were similar in 2D and 3D cultures. Elucidating the effects of 3D culture on growth and metabolism of hESCs may facilitate efforts for developing integrated, scalable cell expansion and differentiation processes with these cells.
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Affiliation(s)
- Samira M Azarin
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, USA
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21
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Frazer C, Young PG. Redundant mechanisms prevent mitotic entry following replication arrest in the absence of Cdc25 hyper-phosphorylation in fission yeast. PLoS One 2011; 6:e21348. [PMID: 21731711 PMCID: PMC3121752 DOI: 10.1371/journal.pone.0021348] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 05/27/2011] [Indexed: 11/18/2022] Open
Abstract
Following replication arrest the Cdc25 phosphatase is phosphorylated and inhibited by Cds1. It has previously been reported that expressing Cdc25 where 9 putative amino-terminal Cds1 phosphorylation sites have been substituted to alanine results in bypass of the DNA replication checkpoint. However, these results were acquired by expression of the phosphorylation mutant using a multicopy expression vector in a genetic background where the DNA replication checkpoint is intact. In order to clarify these results we constructed a Cdc25(9A)-GFP native promoter integrant and examined its effect on the replication checkpoint at endogenous expression levels. In this strain the replication checkpoint operates normally, conditional on the presence of the Mik1 kinase. In response to replication arrest the Cdc25(9A)-GFP protein is degraded, suggesting the presence of a backup mechanism to eliminate the phosphatase when it cannot be inhibited through phosphorylation.
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Affiliation(s)
- Corey Frazer
- Department of Biology, Queen's University, Kingston, Ontario, Canada
| | - Paul G. Young
- Department of Biology, Queen's University, Kingston, Ontario, Canada
- * E-mail:
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22
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Vilela M, Morgan JJ, Lindahl PA. Mathematical model of a cell size checkpoint. PLoS Comput Biol 2010; 6:e1001036. [PMID: 21187911 PMCID: PMC3002998 DOI: 10.1371/journal.pcbi.1001036] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Accepted: 11/16/2010] [Indexed: 01/06/2023] Open
Abstract
How cells regulate their size from one generation to the next has remained an enigma for decades. Recently, a molecular mechanism that links cell size and cell cycle was proposed in fission yeast. This mechanism involves changes in the spatial cellular distribution of two proteins, Pom1 and Cdr2, as the cell grows. Pom1 inhibits Cdr2 while Cdr2 promotes the G2 → M transition. Cdr2 is localized in the middle cell region (midcell) whereas the concentration of Pom1 is highest at the cell tips and declines towards the midcell. In short cells, Pom1 efficiently inhibits Cdr2. However, as cells grow, the Pom1 concentration at midcell decreases such that Cdr2 becomes activated at some critical size. In this study, the chemistry of Pom1 and Cdr2 was modeled using a deterministic reaction-diffusion-convection system interacting with a deterministic model describing microtubule dynamics. Simulations mimicked experimental data from wild-type (WT) fission yeast growing at normal and reduced rates; they also mimicked the behavior of a Pom1 overexpression mutant and WT yeast exposed to a microtubule depolymerizing drug. A mechanism linking cell size and cell cycle, involving the downstream action of Cdr2 on Wee1 phosphorylation, is proposed. Cells delay division into two daughter cells until they reach a particular size. However, the molecular-level mechanisms by which they do this have remained unknown until recently. A cell-size checkpoint mechanism in rod-shaped fission yeast cells has recently been shown to involve two proteins, Pom1 and Cdr2. The concentrations of these proteins in the middle of the cell differ from that at the poles. The changing nature of these spatial gradients as the cell grows is size-sensitive. Pom1 inhibits Cdr2 while Cdr2 stimulates the cell to enter into mitosis. In short cells, the Pom1 concentration in the middle of the cell is so great that Cdr2 is inhibited. As cells grow, the Pom1 concentration in the middle of the cell declines; at some particular size, Cdr2 activates. In this study, we developed a mathematical model that mimics this checkpoint behavior.
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Affiliation(s)
- Marco Vilela
- Department of Chemistry, Texas A&M University, College Station, Texas, United States of America
| | - Jeffrey J. Morgan
- Department of Mathematics, University of Houston, Houston, Texas, United States of America
| | - Paul A. Lindahl
- Department of Chemistry, Texas A&M University, College Station, Texas, United States of America
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Wicky S, Tjandra H, Schieltz D, Yates J, Kellogg DR. The Zds proteins control entry into mitosis and target protein phosphatase 2A to the Cdc25 phosphatase. Mol Biol Cell 2010; 22:20-32. [PMID: 21119008 PMCID: PMC3016974 DOI: 10.1091/mbc.e10-06-0487] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The Wee1 kinase restrains entry into mitosis by phosphorylating and inhibiting cyclin-dependent kinase 1 (Cdk1). The Cdc25 phosphatase promotes entry into mitosis by removing Cdk1 inhibitory phosphorylation. Experiments in diverse systems have established that Wee1 and Cdc25 are regulated by protein phosphatase 2A (PP2A), but a full understanding of the function and regulation of PP2A in entry into mitosis has remained elusive. In budding yeast, entry into mitosis is controlled by a specific form of PP2A that is associated with the Cdc55 regulatory subunit (PP2A(Cdc55)). We show here that related proteins called Zds1 and Zds2 form a tight stoichiometric complex with PP2A(Cdc55) and target its activity to Cdc25 but not to Wee1. Conditional inactivation of the Zds proteins revealed that their function is required primarily at entry into mitosis. In addition, Zds1 undergoes cell cycle-dependent changes in phosphorylation. Together, these observations define a role for the Zds proteins in controlling specific functions of PP2A(Cdc55) and suggest that upstream signals that regulate PP2A(Cdc55) may play an important role in controlling entry into mitosis.
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Affiliation(s)
- Sidonie Wicky
- Department of Molecular, Cell, and Developmental Biology, Univ. of California, Santa Cruz, CA 95064, USA
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24
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Fedyanina OS. The alp1-1315 mutation of the tubulin-folding cofactor D gene delays the mitosis initiation in cdc25-22 mutant cells of Schizosaccharomyces pombe. RUSS J GENET+ 2010. [DOI: 10.1134/s1022795410030051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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25
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Proteomic analysis of early-response to mechanical stress in neonatal rat mandibular condylar chondrocytes. J Cell Physiol 2010; 223:610-22. [DOI: 10.1002/jcp.22052] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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26
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Li R, Tang XL, Miao SY, Zong SD, Wang LF. Regulation of the G2/M phase of the cell cycle by sperm associated antigen 8 (SPAG8) protein. Cell Biochem Funct 2009; 27:264-8. [DOI: 10.1002/cbf.1574] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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27
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Robertson AM, Hagan IM. Stress-regulated kinase pathways in the recovery of tip growth and microtubule dynamics following osmotic stress in S. pombe. J Cell Sci 2008; 121:4055-68. [PMID: 19033386 DOI: 10.1242/jcs.034488] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cell-integrity and stress-response MAP kinase pathways (CIP and SRP, respectively) are stimulated by various environmental stresses. Ssp1 kinase modulates actin dynamics and is rapidly recruited to the plasma membrane following osmotic stress. Here, we show that osmotic stress arrested tip growth, induced the deposition of abnormal cell-wall deposits at tips and led to disassociation of F-actin foci from cell tips together with a reduction in the amount of F-actin in these foci. Osmotic stress also ;froze' the dynamics of interphase microtubule bundles, with microtubules remaining static for approximately 38 minutes (at 30 degrees C) before fragmenting upon return to dynamic behaviour. The timing with which microtubules resumed dynamic behaviour relied upon SRP activation of Atf1-mediated transcription, but not on either CIP or Ssp1 signalling. Analysis of the recovery of tip growth showed that: (1) the timing of recovery was controlled by SRP-stimulated Atf1 transcription; (2) re-establishment of polarized tip growth was absolutely dependent upon SRP and partially dependent upon Ssp1 signalling; and (3) selection of the site for polarized tip extension required Ssp1 and the SRP-associated polarity factor Wsh3 (also known as Tea4). CIP signalling did not impact upon any aspect of recovery. The normal kinetics of tip growth following osmotic stress of plo1.S402A/E mutants established that SRP control over the resumption of tip growth after osmotic stress is distinct from its control of tip growth following heat or gravitational stresses.
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Affiliation(s)
- Alasdair M Robertson
- CRUK Cell Division Laboratory, Paterson Institute for Cancer Research, University of Manchester, Wilmslow Road, Manchester M20 4BX, UK
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28
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Abstract
Microtubules assume a variety of structures throughout the different stages of the cell cycle. Ensuring the correct assembly of such structures is essential to guarantee cell division. During mitosis, it is well established that the spindle assembly checkpoint monitors the correct attachment of sister chromatids to the mitotic spindle. However, the role that microtubule cytoskeleton integrity plays for cell-cycle progression during interphase is uncertain. Here we describe the existence of a mechanism, independent of the mitotic checkpoint, that delays entry into mitosis in response to G(2)-phase microtubule damage. Disassembly of the G(2)-phase microtubule array leads to the stabilization of the universal mitotic inhibitor Wee1, thus actively delaying entry into mitosis via inhibitory Cdc2 Tyr15 phosphorylation.
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Meadows JC, Millar J. Latrunculin A delays anaphase onset in fission yeast by disrupting an Ase1-independent pathway controlling mitotic spindle stability. Mol Biol Cell 2008; 19:3713-23. [PMID: 18562692 DOI: 10.1091/mbc.e08-02-0164] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
It has been proposed previously that latrunculin A, an inhibitor of actin polymerization, delays the onset of anaphase by causing spindle misorientation in fission yeast. However, we show that Delta mto1 cells, which are defective in nucleation of cytoplasmic microtubules, have profoundly misoriented spindles but are not delayed in the timing of sister chromatid separation, providing compelling evidence that fission yeast does not possess a spindle orientation checkpoint. Instead, we show that latrunculin A delays anaphase onset by disrupting interpolar microtubule stability. This effect is abolished in a latrunculin A-insensitive actin mutant and exacerbated in cells lacking Ase1, which cross-links antiparallel interpolar microtubules at the spindle midzone both before and after anaphase. These data indicate that both Ase1 and an intact actin cytoskeleton are required for preanaphase spindle stability. Finally, we show that loss of Ase1 activates a checkpoint that requires only the Mad3, Bub1, and Mph1, but not Mad1, Mad2, or Bub3 checkpoint proteins.
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Affiliation(s)
- John C Meadows
- Division of Yeast Genetics, National Institute for Medical Research, London NW7 1AA, United Kingdom
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30
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Daga RR, Nurse P. Interphase microtubule bundles use global cell shape to guide spindle alignment in fission yeast. J Cell Sci 2008; 121:1973-80. [PMID: 18495844 DOI: 10.1242/jcs.011825] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Correct spindle alignment requires a cell to detect and interpret its global geometry and to communicate this information to the mitotic spindle. In the fission yeast, Schizosaccharomyces pombe, the mitotic spindle is aligned with the longitudinal axis of the rod-shaped cell. Here, using wild-type and cell-shape mutants we investigate the mechanism of initial spindle alignment and show that attachment of interphase microtubules to the spindle pole bodies (SPB), the yeast equivalent of the centrosome, is required to align duplicated SPBs, and thus the mitotic spindle, with the long axis of the cell. In the absence of interphase microtubules or attachment between the microtubules and the SPB, newly formed spindles are randomly oriented. We show that the axis of the mitotic spindle correlates with the axis along which the SPB, as a consequence of interphase microtubule dynamics, oscillates just before mitosis. We propose that cell geometry guides cytoplasmic microtubule alignment, which in turn, determines initial spindle alignment, and demonstrate that a failure of the spindle pre-alignment mechanism results in unequal chromosome segregation when spindle length is reduced.
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Tatebe H, Nakano K, Maximo R, Shiozaki K. Pom1 DYRK regulates localization of the Rga4 GAP to ensure bipolar activation of Cdc42 in fission yeast. Curr Biol 2008; 18:322-30. [PMID: 18328707 PMCID: PMC2277499 DOI: 10.1016/j.cub.2008.02.005] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Revised: 01/25/2008] [Accepted: 01/25/2008] [Indexed: 12/24/2022]
Abstract
BACKGROUND In the fission yeast Schizosaccharomyces pombe, cell growth takes place exclusively at both ends of the cylindrical cell. During this highly polarized growth, microtubules are responsible for the placement of the cell-end marker proteins, the Tea1-Tea4/Wsh3 complex, which recruits the Pom1 DYRK-family protein kinase. Pom1 is required for proper positioning of growth sites, and the Deltapom1 mutation brings about monopolar cell growth. RESULTS Pom1 kinase physically interacts with Rga4, which has a GAP (GTPase-activating protein) domain for Rho-family GTPase. Genetic and biochemical evidence indicates that Rga4 functions as GAP for the Cdc42 GTPase, an evolutionarily conserved regulator of F-actin. CRIB (Cdc42/Rac interactive binding)-GFP microscopy has revealed that GTP-bound, active Cdc42 is concentrated to growing cell ends accompanied by developed F-actin structures, where the Rga4 GAP is excluded. The monopolar Deltapom1 mutant fails to eliminate Rga4 from the nongrowing cell end, resulting in monopolar distribution of GTP-Cdc42 to the growing cell end. However, mutational inactivation of Rga4 allows Cdc42 to be active at both ends of Deltapom1 cells, suggesting that mislocalization of Rga4 in the Deltapom1 mutant contributes to its monopolar phenotype. CONCLUSIONS Pom1 kinase recruited to cell ends by the Tea1-Tea4/Wsh3 complex is essential for proper localization of a GAP for Cdc42, Rga4, which ensures bipolar localization of GTP-bound, active Cdc42. Because of the established role of Cdc42 in F-actin formation, these observations provide a new insight into how the microtubule system achieves localized formation of F-actin to generate cell polarity.
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Affiliation(s)
- Hisashi Tatebe
- Section of Microbiology College of Biological Sciences University of California Davis, California 95616
| | - Kentaro Nakano
- Department of Structural Biosciences Graduate School of Life and Environmental Sciences University of Tsukuba Tennohdai, Tsukuba, Ibaraki 305−8577 Japan
| | - Rachel Maximo
- Section of Microbiology College of Biological Sciences University of California Davis, California 95616
| | - Kazuhiro Shiozaki
- Section of Microbiology College of Biological Sciences University of California Davis, California 95616
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32
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George VT, Brooks G, Humphrey TC. Regulation of cell cycle and stress responses to hydrostatic pressure in fission yeast. Mol Biol Cell 2007; 18:4168-79. [PMID: 17699598 PMCID: PMC1995737 DOI: 10.1091/mbc.e06-12-1141] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We have investigated the cellular responses to hydrostatic pressure by using the fission yeast Schizosaccharomyces pombe as a model system. Exposure to sublethal levels of hydrostatic pressure resulted in G2 cell cycle delay. This delay resulted from Cdc2 tyrosine-15 (Y-15) phosphorylation, and it was abrogated by simultaneous disruption of the Cdc2 kinase regulators Cdc25 and Wee1. However, cell cycle delay was independent of the DNA damage, cytokinesis, and cell size checkpoints, suggesting a novel mechanism of Cdc2-Y15 phosphorylation in response to hydrostatic pressure. Spc1/Sty1 mitogen-activated protein (MAP) kinase, a conserved member of the eukaryotic stress-activated p38, mitogen-activated protein (MAP) kinase family, was rapidly activated after pressure stress, and it was required for cell cycle recovery under these conditions, in part through promoting polo kinase (Plo1) phosphorylation on serine 402. Moreover, the Spc1 MAP kinase pathway played a key role in maintaining cell viability under hydrostatic pressure stress through the bZip transcription factor, Atf1. Further analysis revealed that prestressing cells with heat increased barotolerance, suggesting adaptational cross-talk between these stress responses. These findings provide new insight into eukaryotic homeostasis after exposure to pressure stress.
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Affiliation(s)
- Vinoj T. George
- *Medical Research Council Radiation Oncology and Biology Unit, Harwell, Didcot, Oxfordshire, OX11 0RD, United Kingdom; and
| | - Gavin Brooks
- Cardiovascular Research Group, School of Pharmacy, University of Reading, Reading, Berkshire, RG6 6AP, United Kingdom
| | - Timothy C. Humphrey
- *Medical Research Council Radiation Oncology and Biology Unit, Harwell, Didcot, Oxfordshire, OX11 0RD, United Kingdom; and
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Gu YY, Zhang HY, Zhang HJ, Li SY, Ni JH, Jia HT. 8-Chloro-adenosine inhibits growth at least partly by interfering with actin polymerization in cultured human lung cancer cells. Biochem Pharmacol 2006; 72:541-50. [PMID: 16844099 DOI: 10.1016/j.bcp.2006.05.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Revised: 05/10/2006] [Accepted: 05/16/2006] [Indexed: 01/30/2023]
Abstract
A key feature of actin is its ability to bind and hydrolyze ATP. 8-Chloro-adenosine (8-Cl-Ado), which can be phosphorylated to the moiety of 8-Cl-ATP in living cells, inhibits tumor cell proliferation. Therefore we tested the hypothesis that 8-Cl-Ado can interfere with the dynamic state of actin polymerization. We found that 8-Cl-Ado inhibited the growth of human lung cancer cell line A549 and H1299 in culture, and arrested the target cells in G2/M phase evidenced by fluorescence-activated cell sorting (FACS). Immunocytochemistry showed that the normal organization of microfilaments was disrupted in 8-Cl-Ado-exposed cells, which is accompanied by the decrease of cell size and the alteration of cell shape, and by aberrant mitosis and apoptosis in targeted cells. Furthermore, in vitro light scattering assays revealed that 8-Cl-ATP could directly inhibit the transition of G-actin to F-actin. DNase I inhibition assays showed that the G/F-actin ratio, a surrogate marker of actin polymerization status in living cells, was significantly increased in 8-Cl-Ado-exposed A549 and H1299 cells, compared to the G/F-actin ratio in unexposed cells. Taken together, these results indicate that 8-Cl-Ado exposure can alter the dynamic properties of actin polymerization, disrupt the dynamic instability or the rearrangement ability of actin filaments. Therefore, our data suggest that 8-Cl-Ado may exert its cytotoxicity at least partly by interfering with the dynamic instability of microfilaments, which may correlate with its inhibitory effects on cell proliferation and cell death.
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Affiliation(s)
- Yan-Yan Gu
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Xue Yuan Road 38, Beijing 100083, PR China
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34
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Douglas LM, Alvarez FJ, McCreary C, Konopka JB. Septin function in yeast model systems and pathogenic fungi. EUKARYOTIC CELL 2005; 4:1503-12. [PMID: 16151244 PMCID: PMC1214204 DOI: 10.1128/ec.4.9.1503-1512.2005] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Lois M. Douglas
- Department of Molecular Genetics and Microbiology, Graduate Program in Genetics, State University of New York, Stony Brook, New York 11794-5222
| | - Francisco J. Alvarez
- Department of Molecular Genetics and Microbiology, Graduate Program in Genetics, State University of New York, Stony Brook, New York 11794-5222
| | - Cheryl McCreary
- Department of Molecular Genetics and Microbiology, Graduate Program in Genetics, State University of New York, Stony Brook, New York 11794-5222
| | - James B. Konopka
- Department of Molecular Genetics and Microbiology, Graduate Program in Genetics, State University of New York, Stony Brook, New York 11794-5222
- Corresponding author. Mailing address: Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, NY 11794-5222. Phone: (631) 632-8715. Fax: (631) 632-9797. E-mail:
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35
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Harvey SL, Charlet A, Haas W, Gygi SP, Kellogg DR. Cdk1-dependent regulation of the mitotic inhibitor Wee1. Cell 2005; 122:407-20. [PMID: 16096060 DOI: 10.1016/j.cell.2005.05.029] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Revised: 04/27/2005] [Accepted: 05/31/2005] [Indexed: 10/25/2022]
Abstract
The Wee1 kinase phosphorylates and inhibits cyclin-dependent kinase 1 (Cdk1), thereby delaying entry into mitosis until appropriate conditions have been met. An understanding of the mechanisms that regulate Wee1 should provide new insight into how cells make the decision to enter mitosis. We report here that Swe1, the budding-yeast homolog of Wee1, is directly regulated by Cdk1. Phosphorylation of Swe1 by Cdk1 activates Swe1 and is required for formation of a stable Swe1-Cdk1 complex that maintains Cdk1 in the inhibited state. Dephosphorylation of Cdk1 leads to further phosphorylation of Swe1 and release of Cdk1. Thus, Cdk1 both positively and negatively regulates its own inhibitor. Regulation of the Swe1-Cdk1 complex is likely to play a critical role in controlling the transition into mitosis.
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Affiliation(s)
- Stacy L Harvey
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, California 95064, USA
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36
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Abstract
Size is a fundamental attribute impacting cellular design, fitness, and function. Size homeostasis requires a doubling of cell mass with each division. In yeast, division is delayed until a critical size has been achieved. In metazoans, cell cycles can be actively coupled to growth, but in certain cell types extracellular signals may independently induce growth and division. Despite a long history of study, the fascinating mechanisms that control cell size have resisted molecular genetic insight. Recently, genetic screens in Drosophila and functional genomics approaches in yeast have macheted into the thicket of cell size control.
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Affiliation(s)
- Paul Jorgensen
- Department of Medical Genetics and Microbiology, University of Toronto, Toronto ON, Canada M5S 1A8.
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37
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Abstract
The dinoflagellates, a diverse sister group of the malaria parasites, are the major agents causing harmful algal blooms and are also the symbiotic algae of corals. Dinoflagellate nuclei differ significantly from other eukaryotic nuclei by having extranuclear spindles, no nucleosomes and enormous genomes in liquid crystal states. These cytological characteristics were related to the acquisition of prokaryotic genes during evolution (hence Mesokaryotes), which may also account for the biochemical diversity and the relatively slow growth rates of dinoflagellates. The fact that the proliferation of many dinoflagellates is sensitive to turbulence may be due to the physiological requirements of the genome's liquid crystal states. Mechanical stress and anti-microtubule drugs induce cell cycle arrest mainly in G1, implicating a role for the permanent cortical microtubular cytoskeleton in mechanotransduction. The cell cycles of photosynthetic dinoflagellates are also gated by the circadian rhythm, with cell division occurring mainly at the end of the dark phase. Cell growth and the biosynthesis of many toxins occur during the light phase, corresponding to G1 in the cell cycle. The dinoflagellates also embody several options for coupling cell cycle progression to cell growth, enabling them to make the best use of available resources and possibly preparing them for a symbiotic existence.
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Affiliation(s)
- Joseph T Y Wong
- Department of Biology, Hong Kong University of Science and Technology, Hong Kong SAR, People's Republic of China.
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38
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Karagiannis J, Bimbó A, Rajagopalan S, Liu J, Balasubramanian MK. The nuclear kinase Lsk1p positively regulates the septation initiation network and promotes the successful completion of cytokinesis in response to perturbation of the actomyosin ring in Schizosaccharomyces pombe. Mol Biol Cell 2004; 16:358-71. [PMID: 15537703 PMCID: PMC539179 DOI: 10.1091/mbc.e04-06-0502] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cytokinesis in fission yeast requires the function of an actomyosin-based contractile ring whose constriction is dependent on a signaling module termed the septation initiation network (SIN). In response to minor perturbation of the ring, the duration of SIN signaling is extended concurrently with a delay in nuclear cycle progression. These mechanisms require the conserved phosphatase Clp1p/Flp1p and facilitate the successful completion of cytokinesis, thereby increasing cellular viability. To isolate novel components of this cytokinesis monitoring system, we screened a genome-wide bank of protein kinase deletion mutants and identified Lsk1p, a nuclear-localized protein kinase. Similar to clp1Delta mutants, and in contrast to wild type, lsk1Delta cells are unable to maintain the integrity of the actomyosin ring upon treatment with low doses (0.3 microM) of latrunculin A. However, unlike clp1Delta mutants, lsk1Delta cells are competent to delay nuclear cycle progression after cytokinetic failure. In addition, lsk1Delta mutants suppress the lethal, multiseptate phenotype conferred by hyperactivation of the SIN, demonstrating that Lsk1p is a positive regulator of this module. In this report, we demonstrate that Lsk1p acts in parallel to Clp1p to promote actomyosin ring stability upon checkpoint activation. Our studies also establish that actomyosin ring maintenance and nuclear cycle delay in response to cytokinetic perturbation can be genetically resolved into independent pathways.
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Affiliation(s)
- Jim Karagiannis
- Laboratory of Cell Division, Temasek Life Sciences Laboratory, Singapore 117604, Singapore.
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39
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Kellogg DR. Wee1-dependent mechanisms required for coordination of cell growth and cell division. J Cell Sci 2004; 116:4883-90. [PMID: 14625382 DOI: 10.1242/jcs.00908] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Wee1-related kinases function in a highly conserved mechanism that controls the timing of entry into mitosis. Loss of Wee1 function causes fission yeast and budding yeast cells to enter mitosis before sufficient growth has occurred, leading to formation of daughter cells that are smaller than normal. Early work in fission yeast suggested that Wee1 is part of a cell-size checkpoint that prevents entry into mitosis before cells have reached a critical size. Recent experiments in fission yeast and budding yeast have provided new support for this idea. In addition, studies in budding yeast have revealed the existence of highly intricate signaling networks that are required for regulation of Swe1, the budding yeast homolog of Wee1. Further understanding of these signaling networks may provide important clues to how cell growth and cell division are coordinated.
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Affiliation(s)
- Douglas R Kellogg
- Sinsheimer Laboratories, Department of Molecular, Cellular and Developmental Biology, University of California, Santa Cruz, CA 95064, USA.
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40
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Tournier S, Gachet Y, Buck V, Hyams JS, Millar JBA. Disruption of astral microtubule contact with the cell cortex activates a Bub1, Bub3, and Mad3-dependent checkpoint in fission yeast. Mol Biol Cell 2004; 15:3345-56. [PMID: 15146064 PMCID: PMC452588 DOI: 10.1091/mbc.e04-03-0256] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
In animal and yeast cells, the mitotic spindle is aligned perpendicularly to the axis of cell division. This ensures that sister chromatids are separated to opposite sides of the cytokinetic actomyosin ring. In fission yeast, spindle rotation is dependent upon the interaction of astral microtubules with the cortical actin cytoskeleton. In this article, we show that addition of Latrunculin A, which prevents spindle rotation, delays the separation of sister chromatids and anaphase promoting complex-mediated destruction of spindle-associated Securin and Cyclin B. Moreover, we find that whereas sister kinetochore pairs normally congress to the spindle midzone before anaphase onset, this congression is disrupted when astral microtubule contact with the actin cytoskeleton is disturbed. By analyzing the timing of kinetochore separation, we find that this anaphase delay requires the Bub3, Mad3, and Bub1 but not the Mad1 or Mad2 spindle assembly checkpoint proteins. In agreement with this, we find that Bub1 remains associated with kinetochores when spindles are mispositioned. These data indicate that, in fission yeast, astral microtubule contact with the medial cell cortex is monitored by a subset of spindle assembly checkpoint proteins. We propose that this checkpoint ensures spindles are properly oriented before anaphase takes place.
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Affiliation(s)
- Sylvie Tournier
- Division of Yeast Genetics, National Institute for Medical Research, London NW7 1AA, United Kingdom
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41
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Rouzaire-Dubois B, Malo M, Milandri JB, Dubois JM. Cell size-proliferation relationship in rat glioma cells. Glia 2004; 45:249-57. [PMID: 14730698 DOI: 10.1002/glia.10320] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The homeostasis of the central nervous system is highly controlled by glial cells and is dramatically altered in the case of glioma. In this respect, the complex connection between cell size and division is of particular importance and needs clarifying. In order to investigate this connection, cell number and volume were measured in C6 rat glioma cells under different experimental conditions, including continuous cell culture, Cl- channel blockade, and anisotonicity, and in the presence of an inhibitory conditioned medium collected from cell cultures or in a medium containing a low level of fetal calf serum. The rate of cell proliferation changed with cell volume in a bell-shaped manner, so that it is optimal within a cell volume window and appears to be controlled by low and high cell size checkpoints. The cell size-proliferation relationship can be defined by Boltzmann-like equations, which may reflect the effects of macromolecular crowding on proteins controlling the cell cycle progression. Altogether, these observations indicate that glioma cell proliferation is controlled predominantly but not exclusively by cell size-dependent mechanisms.
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42
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Venkatram S, Tasto JJ, Feoktistova A, Jennings JL, Link AJ, Gould KL. Identification and characterization of two novel proteins affecting fission yeast gamma-tubulin complex function. Mol Biol Cell 2004; 15:2287-301. [PMID: 15004232 PMCID: PMC404023 DOI: 10.1091/mbc.e03-10-0728] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The gamma-tubulin complex, via its ability to organize microtubules, is critical for accurate chromosome segregation and cytokinesis in the fission yeast, Schizosaccharomyces pombe. To better understand its roles, we have purified the S. pombe gamma-tubulin complex. Mass spectrometric analyses of the purified complex revealed known components and identified two novel proteins (i.e., Mbo1p and Gfh1p) with homology to gamma-tubulin-associated proteins from other organisms. We show that both Mbo1p and Gfh1p localize to microtubule organizing centers. Although cells deleted for either mbo1(+) or gfh1(+) are viable, they exhibit a number of defects associated with altered microtubule function such as defects in cell polarity, nuclear positioning, spindle orientation, and cleavage site specification. In addition, mbo1Delta and gfh1Delta cells exhibit defects in astral microtubule formation and anchoring, suggesting that these proteins have specific roles in astral microtubule function. This study expands the known roles of gamma-tubulin complex components in organizing different types of microtubule structures in S. pombe.
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Affiliation(s)
- Srinivas Venkatram
- Department of Cell and Developmental Biology, Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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43
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Rajagopalan S, Bimbo A, Balasubramanian MK, Oliferenko S. A Potential Tension-Sensing Mechanism that Ensures Timely Anaphase Onset upon Metaphase Spindle Orientation. Curr Biol 2004; 14:69-74. [PMID: 14711417 DOI: 10.1016/j.cub.2003.12.027] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The spindle orientation checkpoint (SOC) in fission yeast has been proposed to delay metaphase-to-anaphase transition when the spindle poles are misaligned with respect to the long axis of the cell. This checkpoint is activated in the absence of either an actomyosin division ring or astral microtubules. Although the SOC could be overridden in the absence of the transcription factor Atf1p, its mechanistic nature remained unclear. Here, we show that the SOC-triggered metaphase delay depends on a subset of the spindle assembly checkpoint (SAC) components Mph1p and Bub1p. Based on this finding and a detailed imaging of the spindle orientation process, we hypothesized that the spindle pole might contain proteins capable of sensing the achievement of spindle alignment. We identified the kendrin-like spindle pole body resident Pcp1p as a candidate molecule. A targeted mutation in its central domain specifically triggered the SOC in spite of the presence of oriented spindles, causing a metaphase delay that could be relieved in the absence of Mph1p, Bub1p, and Atf1p. Thus, Pcp1p might provide a link between the mechanical process of spindle alignment and the signal transduction that initiates anaphase.
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Affiliation(s)
- Srividya Rajagopalan
- Temasek Life Sciences Laboratory, 1 Research Link, The National University of Singapore, 117604, Republic of, Singapore, Singapore
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44
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Harvey SL, Kellogg DR. Conservation of mechanisms controlling entry into mitosis: budding yeast wee1 delays entry into mitosis and is required for cell size control. Curr Biol 2003; 13:264-75. [PMID: 12593792 DOI: 10.1016/s0960-9822(03)00049-6] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND In fission yeast, the Wee1 kinase delays entry into mitosis until a critical cell size has been reached; however, a similar role for Wee1-related kinases has not been reported in other organisms. SWE1, the budding yeast homolog of wee1, is thought to function in a morphogenesis checkpoint that delays entry into mitosis in response to defects in bud morphogenesis. RESULTS In contrast to previous studies, we found that budding yeast swe1 Delta cells undergo premature entry into mitosis, leading to birth of abnormally small cells. Additional experiments suggest that conditions that activate the morphogenesis checkpoint may actually be activating a G2/M cell size checkpoint. For example, actin depolymerization is thought to activate the morphogenesis checkpoint by inhibiting bud morphogenesis. However, actin depolymerization also inhibits bud growth, suggesting that it could activate a cell size checkpoint. Consistent with this possibility, we found that actin depolymerization fails to induce a G2/M delay once daughter buds pass a critical size. Other conditions that activate the morphogenesis checkpoint block bud formation, which could also activate a size checkpoint if cell size at G2/M is monitored in the daughter bud. Previous work reported that Swe1 is degraded during G2, which was proposed to account for failure of large-budded cells to arrest in response to actin depolymerization. However, we found that Swe1 is present throughout G2 and undergoes hyperphosphorylation as cells enter mitosis, as found in other organisms. CONCLUSIONS Our results suggest that the mechanisms known to coordinate entry into mitosis in other organisms have been conserved in budding yeast.
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Affiliation(s)
- Stacy L Harvey
- Department of Molecular, Cellular, and Developmental Biology, Sinsheimer Labs, University of California, Santa Cruz, CA 95064, USA
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45
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Coll PM, Trillo Y, Ametzazurra A, Perez P. Gef1p, a new guanine nucleotide exchange factor for Cdc42p, regulates polarity in Schizosaccharomyces pombe. Mol Biol Cell 2003; 14:313-23. [PMID: 12529446 PMCID: PMC140247 DOI: 10.1091/mbc.e02-07-0400] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Schizosaccharomyces pombe cdc42(+) regulates cell morphology and polarization of the actin cytoskeleton. Scd1p/Ral1p is the only described guanine nucleotide exchange factor (GEF) for Cdc42p in S. pombe. We have identified a new GEF, named Gef1p, specifically regulating Cdc42p. Gef1p binds to inactive Cdc42p but not to other Rho GTPases in two-hybrid assays. Overexpression of gef1(+) increases specifically the GTP-bound Cdc42p, and Gef1p is capable of stimulating guanine nucleotide exchange of Cdc42p in vitro. Overexpression of gef1(+) causes changes in cell morphology similar to those caused by overexpression of the constitutively active cdc42G12V allele. Gef1p localizes to the septum. gef1(+) deletion is viable but causes a mild cell elongation and defects in bipolar growth and septum formation, suggesting a role for Gef1p in the control of cell polarity and cytokinesis. The double mutant gef1delta scd1delta is not viable, indicating that they share an essential function as Cdc42p activators. However, both deletion and overexpression of either gef1(+) or scd1(+) causes different morphological phenotypes, which suggest different functions. Genetic evidence revealed a link between Gef1p and the signaling pathway of Shk1/Orb2p and Orb6p. In contrast, no genetic interaction between Gef1p and Shk2p-Mkh1p pathway was observed.
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Affiliation(s)
- Pedro M Coll
- Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas/Departamento de Microbiologia y Genetica, Universidad de Salamanca, Edificio Departamental, 37007 Salamanca, Spain
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46
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Chua G, Lingner C, Frazer C, Young PG. The sal3(+) gene encodes an importin-beta implicated in the nuclear import of Cdc25 in Schizosaccharomyces pombe. Genetics 2002; 162:689-703. [PMID: 12399381 PMCID: PMC1462273 DOI: 10.1093/genetics/162.2.689] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In Schizosaccharomyces pombe, the nuclear accumulation of Cdc25 peaks in G2 and is necessary for the proper timing of mitotic entry. Here, we identify the sal3(+) gene product as an importin-beta homolog that participates in the nuclear import of Cdc25. Loss of sal3(+) results in a cell cycle delay, failure to undergo G1 arrest under nitrogen-starvation conditions, and mislocalization of Cdc25 to the cytosol. Fusion of an exogenous classical nuclear localization sequence (cNLS) to Cdc25 restores its nuclear accumulation in a sal3 disruptant and suppresses the sal3 mutant phenotypes. In addition, we show that enhanced nuclear localization of Cdc25 at endogenous levels of expression advances the onset of mitosis. These results demonstrate that the nuclear translocation of Cdc25 is important for the timing of mitotic entry and that Sal3 plays an important role in this process.
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Affiliation(s)
- Gordon Chua
- Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada
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47
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Abstract
To remain viable, cells have to coordinate cell growth with cell division. In yeast, this occurs at two control points: the boundaries between G1 and S phases, also known as Start, and between G2 and M phases. Theoretically, coordination can be achieved by independent regulation of growth and division, or by participation of surveillance mechanisms in which cell size feeds back into cell-cycle control. This article discusses recent advances in the identification of sizing mechanisms in budding and in fission yeast, and how these mechanisms integrate with environmental stimuli. A comparison of the G1-S and G2-M size-control modules in the two species reveals a degree of conservation higher than previously thought. This reinforces the notion that internal sizing could be a conserved feature of cell-cycle control throughout eukaryotes.
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Affiliation(s)
- Ivan Rupes
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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48
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Current awareness on yeast. Yeast 2002; 19:651-8. [PMID: 11967835 DOI: 10.1002/yea.824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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49
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Current awareness on yeast. Yeast 2002; 19:565-72. [PMID: 11921105 DOI: 10.1002/yea.823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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