1
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Nageshan RK, Krogan N, Cooper JP. Parallel genetic screens identify nuclear envelope homeostasis as a key determinant of telomere entanglement resolution in fission yeast. G3 (BETHESDA, MD.) 2024; 14:jkae078. [PMID: 38657142 PMCID: PMC11228871 DOI: 10.1093/g3journal/jkae078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 03/18/2024] [Accepted: 03/21/2024] [Indexed: 04/26/2024]
Abstract
In fission yeast lacking the telomere binding protein, Taz1, replication forks stall at telomeres, triggering deleterious downstream events. Strand invasion from one taz1Δ telomeric stalled fork to another on a separate (nonsister) chromosome leads to telomere entanglements, which are resolved in mitosis at 32°C; however, entanglement resolution fails at ≤20°C, leading to cold-specific lethality. Previously, we found that loss of the mitotic function of Rif1, a conserved DNA replication and repair factor, suppresses cold sensitivity by promoting resolution of entanglements without affecting entanglement formation. To understand the underlying pathways of mitotic entanglement resolution, we performed a series of genome-wide synthetic genetic array screens to generate a comprehensive list of genetic interactors of taz1Δ and rif1Δ. We modified a previously described screening method to ensure that the queried cells were kept in log phase growth. In addition to recapitulating previously identified genetic interactions, we find that loss of genes encoding components of the nuclear pore complex (NPC) promotes telomere disentanglement and suppresses taz1Δ cold sensitivity. We attribute this to more rapid anaphase midregion nuclear envelope (NE) breakdown in the absence of these NPC components. Loss of genes involved in lipid metabolism reverses the ability of rif1+ deletion to suppress taz1Δ cold sensitivity, again pinpointing NE modulation. A rif1+ separation-of-function mutant that specifically loses Rif1's mitotic functions yields similar genetic interactions. Genes promoting membrane fluidity were enriched in a parallel taz1+ synthetic lethal screen at permissive temperature, cementing the idea that the cold specificity of taz1Δ lethality stems from altered NE homeostasis.
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Affiliation(s)
- Rishi Kumar Nageshan
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 E. 17th Ave, Aurora, CO 80045, USA
- Former address: Telomere Biology Laboratory, Laboratory of Biochemistry and Molecular Biology, NCI, NIH, Bethesda, MD 20892, USA
| | - Nevan Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, 1700 4th Street, 308D, San Francisco, CA 94158, USA
- Quantitative Biosciences Institute (QBI), University of California, San Francisco, CA 94158, USA
- J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | - Julia Promisel Cooper
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 E. 17th Ave, Aurora, CO 80045, USA
- Former address: Telomere Biology Laboratory, Laboratory of Biochemistry and Molecular Biology, NCI, NIH, Bethesda, MD 20892, USA
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2
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Grazzini A, Cavanaugh AM. Fungal microtubule organizing centers are evolutionarily unstable structures. Fungal Genet Biol 2024; 172:103885. [PMID: 38485050 DOI: 10.1016/j.fgb.2024.103885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 03/07/2024] [Accepted: 03/11/2024] [Indexed: 03/24/2024]
Abstract
For most Eukaryotic species the requirements of cilia formation dictate the structure of microtubule organizing centers (MTOCs). In this study we find that loss of cilia corresponds to loss of evolutionary stability for fungal MTOCs. We used iterative search algorithms to identify proteins homologous to those found in Saccharomyces cerevisiae, and Schizosaccharomyces pombe MTOCs, and calculated site-specific rates of change for those proteins that were broadly phylogenetically distributed. Our results indicate that both the protein composition of MTOCs as well as the sequence of MTOC proteins are poorly conserved throughout the fungal kingdom. To begin to reconcile this rapid evolutionary change with the rigid structure and essential function of the S. cerevisiae MTOC we further analyzed how structural interfaces among proteins influence the rates of change for specific residues within a protein. We find that a more stable protein may stabilize portions of an interacting partner where the two proteins are in contact. In summary, while the protein composition and sequences of the MTOC may be rapidly changing the proteins within the structure have a stabilizing effect on one another. Further exploration of fungal MTOCs will expand our understanding of how changes in the functional needs of a cell have affected physical structures, proteomes, and protein sequences throughout fungal evolution.
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Affiliation(s)
- Adam Grazzini
- Department of Biology, Creighton University, Omaha, Nebraska, USA
| | - Ann M Cavanaugh
- Department of Biology, Creighton University, Omaha, Nebraska, USA.
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3
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Pineda-Santaella A, Martín-García R, Fernández-Álvarez A. Analyzing self-assembled spindle dynamics in fission yeast meiosis using in vivo fluorescence imaging. STAR Protoc 2023; 4:102655. [PMID: 37864786 PMCID: PMC10598709 DOI: 10.1016/j.xpro.2023.102655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/21/2023] [Accepted: 09/29/2023] [Indexed: 10/23/2023] Open
Abstract
Chromosome segregation in female meiosis in many metazoans is mediated by acentrosomal spindles. The analysis of the dynamics of self-assembled spindles is a challenge due to the low availability of oocytes. Here, we present a protocol for analyzing self-assembled spindle dynamics in fission yeast meiosis using in vivo fluorescence imaging. We describe steps for starter culture preparation, meiosis induction, and sample preparation. We then detail procedures for acquisition and analysis of images of self-assembled spindles. For complete details on the use and execution of this protocol, please refer to Pineda-Santaella and Fernández-Álvarez (2019)1 and Pineda-Santaella et al. (2021).2.
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Affiliation(s)
- Alberto Pineda-Santaella
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Salamanca, Calle Zacarías González 2, 37007 Salamanca, Spain
| | - Rebeca Martín-García
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Salamanca, Calle Zacarías González 2, 37007 Salamanca, Spain
| | - Alfonso Fernández-Álvarez
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Salamanca, Calle Zacarías González 2, 37007 Salamanca, Spain.
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4
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Ader NR, Chen L, Surovtsev IV, Chadwick WL, Rodriguez EC, King MC, Lusk CP. An ESCRT grommet cooperates with a diffusion barrier to maintain nuclear integrity. Nat Cell Biol 2023; 25:1465-1477. [PMID: 37783794 DOI: 10.1038/s41556-023-01235-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 08/17/2023] [Indexed: 10/04/2023]
Abstract
The molecular mechanisms by which the endosomal sorting complexes required for transport (ESCRT) proteins contribute to the integrity of the nuclear envelope (NE) barrier are not fully defined. We leveraged the single NE hole generated by mitotic extrusion of the Schizosaccharomyces pombe spindle pole body to reveal two modes of ESCRT function executed by distinct complements of ESCRT-III proteins, both dependent on CHMP7/Cmp7. A grommet-like function is required to restrict the NE hole in anaphase B, whereas replacement of Cmp7 by a sealing module ultimately closes the NE in interphase. Without Cmp7, nucleocytoplasmic compartmentalization remains intact despite NE discontinuities of up to 540 nm, suggesting mechanisms to limit diffusion through these holes. We implicate spindle pole body proteins as key components of a diffusion barrier acting with Cmp7 in anaphase B. Thus, NE remodelling mechanisms cooperate with proteinaceous diffusion barriers beyond nuclear pore complexes to maintain the nuclear compartment.
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Affiliation(s)
- Nicholas R Ader
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - Linda Chen
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - Ivan V Surovtsev
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
- Department of Physics, Yale University, New Haven, CT, USA
| | | | - Elisa C Rodriguez
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
| | - Megan C King
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA.
- Department of Molecular, Cell and Developmental Biology, Yale University, New Haven, CT, USA.
| | - C Patrick Lusk
- Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA.
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5
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Amm I, Weberruss M, Hellwig A, Schwarz J, Tatarek-Nossol M, Lüchtenborg C, Kallas M, Brügger B, Hurt E, Antonin W. Distinct domains in Ndc1 mediate its interaction with the Nup84 complex and the nuclear membrane. J Cell Biol 2023; 222:e202210059. [PMID: 37154843 PMCID: PMC10165475 DOI: 10.1083/jcb.202210059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 01/31/2023] [Accepted: 03/17/2023] [Indexed: 05/10/2023] Open
Abstract
Nuclear pore complexes (NPCs) are embedded in the nuclear envelope and built from ∼30 different nucleoporins (Nups) in multiple copies, few are integral membrane proteins. One of these transmembrane nucleoporins, Ndc1, is thought to function in NPC assembly at the fused inner and outer nuclear membranes. Here, we show a direct interaction of Ndc1's transmembrane domain with Nup120 and Nup133, members of the pore membrane coating Y-complex. We identify an amphipathic helix in Ndc1's C-terminal domain binding highly curved liposomes. Upon overexpression, this amphipathic motif is toxic and dramatically alters the intracellular membrane organization in yeast. Ndc1's amphipathic motif functionally interacts with related motifs in the C-terminus of the nucleoporins Nup53 and Nup59, important for pore membrane binding and interconnecting NPC modules. The essential function of Ndc1 can be suppressed by deleting the amphipathic helix from Nup53. Our data indicate that nuclear membrane and presumably NPC biogenesis depends on a balanced ratio between amphipathic motifs in diverse nucleoporins.
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Affiliation(s)
- Ingo Amm
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, Heidelberg, Germany
| | - Marion Weberruss
- Institute of Biochemistry and Molecular Cell Biology, Medical School, RWTH Aachen University, Aachen, Germany
| | - Andrea Hellwig
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Heidelberg, Germany
| | - Johannes Schwarz
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, Heidelberg, Germany
| | - Marianna Tatarek-Nossol
- Institute of Biochemistry and Molecular Cell Biology, Medical School, RWTH Aachen University, Aachen, Germany
| | - Christian Lüchtenborg
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, Heidelberg, Germany
| | - Martina Kallas
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, Heidelberg, Germany
| | - Britta Brügger
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, Heidelberg, Germany
| | - Ed Hurt
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg, Heidelberg, Germany
| | - Wolfram Antonin
- Institute of Biochemistry and Molecular Cell Biology, Medical School, RWTH Aachen University, Aachen, Germany
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6
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Mitic K, Meyer I, Gräf R, Grafe M. Temporal Changes in Nuclear Envelope Permeability during Semi-Closed Mitosis in Dictyostelium Amoebae. Cells 2023; 12:1380. [PMID: 37408214 DOI: 10.3390/cells12101380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/10/2023] [Accepted: 05/11/2023] [Indexed: 07/07/2023] Open
Abstract
The Amoebozoan Dictyostelium discoideum exhibits a semi-closed mitosis in which the nuclear membranes remain intact but become permeabilized to allow tubulin and spindle assembly factors to access the nuclear interior. Previous work indicated that this is accomplished at least by partial disassembly of nuclear pore complexes (NPCs). Further contributions by the insertion process of the duplicating, formerly cytosolic, centrosome into the nuclear envelope and nuclear envelope fenestrations forming around the central spindle during karyokinesis were discussed. We studied the behavior of several Dictyostelium nuclear envelope, centrosomal, and nuclear pore complex (NPC) components tagged with fluorescence markers together with a nuclear permeabilization marker (NLS-TdTomato) by live-cell imaging. We could show that permeabilization of the nuclear envelope during mitosis occurs in synchrony with centrosome insertion into the nuclear envelope and partial disassembly of nuclear pore complexes. Furthermore, centrosome duplication takes place after its insertion into the nuclear envelope and after initiation of permeabilization. Restoration of nuclear envelope integrity usually occurs long after re-assembly of NPCs and cytokinesis has taken place and is accompanied by a concentration of endosomal sorting complex required for transport (ESCRT) components at both sites of nuclear envelope fenestration (centrosome and central spindle).
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Affiliation(s)
- Kristina Mitic
- Department of Cell Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Irene Meyer
- Department of Cell Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Ralph Gräf
- Department of Cell Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Marianne Grafe
- Department of Cell Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
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7
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Schweigel U, Batsios P, Müller-Taubenberger A, Gräf R, Grafe M. Dictyostelium spastin is involved in nuclear envelope dynamics during semi-closed mitosis. Nucleus 2022; 13:144-154. [PMID: 35298348 PMCID: PMC8932920 DOI: 10.1080/19491034.2022.2047289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Dictyostelium amoebae perform a semi-closed mitosis, in which the nuclear envelope is fenestrated at the insertion sites of the mitotic centrosomes and around the central spindle during karyokinesis. During late telophase the centrosome relocates to the cytoplasmic side of the nucleus, the central spindle disassembles and the nuclear fenestrae become closed. Our data indicate that Dictyostelium spastin (DdSpastin) is a microtubule-binding and severing type I membrane protein that plays a role in this process. Its mitotic localization is in agreement with a requirement for the removal of microtubules that would hinder closure of the fenestrae. Furthermore, DdSpastin interacts with the HeH/ LEM-family protein Src1 in BioID analyses as well as the inner nuclear membrane protein Sun1, and shows subcellular co-localizations with Src1, Sun1, the ESCRT component CHMP7 and the IST1-like protein filactin, suggesting that the principal pathway of mitotic nuclear envelope remodeling is conserved between animals and Dictyostelium amoebae.
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Affiliation(s)
- Ulrike Schweigel
- Department of Cell Biology, University of Potsdam, Institute for Biochemistry and Biology, Potsdam-Golm, Germany
| | - Petros Batsios
- Department of Cell Biology, University of Potsdam, Institute for Biochemistry and Biology, Potsdam-Golm, Germany
| | | | - Ralph Gräf
- Department of Cell Biology, University of Potsdam, Institute for Biochemistry and Biology, Potsdam-Golm, Germany
| | - Marianne Grafe
- Department of Cell Biology, University of Potsdam, Institute for Biochemistry and Biology, Potsdam-Golm, Germany
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8
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Vitale J, Khan A, Neuner A, Schiebel E. A perinuclear α-helix with amphipathic features in Brl1 promotes NPC assembly. Mol Biol Cell 2022; 33:ar35. [PMID: 35293775 PMCID: PMC9282021 DOI: 10.1091/mbc.e21-12-0616] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
How nuclear pore complexes (NPC) assemble in the intact nuclear envelope (NE) is only rudimentarily understood. Nucleoporins accumulate at the inner NE (INM), deform this membrane towards the outer nuclear membrane (ONM) and eventually INM and ONM fuse by an unclear mechanism. In budding yeast, the integral membrane protein Brl1 that transiently associates with NPC assembly intermediates is involved in INM/ONM fusion during NPC assembly but leaving the molecular mechanism open. AlphaFold predictions indicate that Brl1-like proteins carry as common motifs an α-helix with amphipathic features (AαH) and a disulfide-stabilized anti-parallel helix bundle (DAH) in the perinuclear space. Mutants with defective AαH (brl1F391E, brl1F391P, brl1L402E) impair the essential function of BRL1. Overexpression of brl1F391E promotes formation of INM and ONM enclosed petal-like structures that carry nucleoporins at their base suggesting that they are derived from an NPC assembly attempt with failed INM/ONM fusion. Accordingly, brl1F391E expression triggers mis-localisation of Nup159 and Nup42 and to a lesser extent Nsp1 that localize on the cytoplasmic face of the NPC. The DAH also contributes to the function of Brl1 and AαH has functions independent of DAH. We propose that AαH and DAH in Brl1 promote INM/ONM fusion during NPC assembly.
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Affiliation(s)
- Jlenia Vitale
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Deutsches Krebsforschungszentrum (DKFZ)-ZMBH Allianz, Universität Heidelberg, 69120 Heidelberg, Germany.,Heidelberg Biosciences International Graduate School (HBIGS), Universität Heidelberg, 69120 Heidelberg, Germany
| | - Azqa Khan
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Deutsches Krebsforschungszentrum (DKFZ)-ZMBH Allianz, Universität Heidelberg, 69120 Heidelberg, Germany.,Heidelberg Biosciences International Graduate School (HBIGS), Universität Heidelberg, 69120 Heidelberg, Germany
| | - Annett Neuner
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Deutsches Krebsforschungszentrum (DKFZ)-ZMBH Allianz, Universität Heidelberg, 69120 Heidelberg, Germany
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Deutsches Krebsforschungszentrum (DKFZ)-ZMBH Allianz, Universität Heidelberg, 69120 Heidelberg, Germany
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9
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Zhang W, Khan A, Vitale J, Neuner A, Rink K, Lüchtenborg C, Brügger B, Söllner TH, Schiebel E. A short perinuclear amphipathic α-helix in Apq12 promotes nuclear pore complex biogenesis. Open Biol 2021; 11:210250. [PMID: 34814743 PMCID: PMC8611336 DOI: 10.1098/rsob.210250] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The integral membrane protein Apq12 is an important nuclear envelope (NE)/endoplasmic reticulum (ER) modulator that cooperates with the nuclear pore complex (NPC) biogenesis factors Brl1 and Brr6. How Apq12 executes these functions is unknown. Here, we identified a short amphipathic α-helix (AαH) in Apq12 that links the two transmembrane domains in the perinuclear space and has liposome-binding properties. Cells expressing an APQ12 (apq12-ah) version in which AαH is disrupted show NPC biogenesis and NE integrity defects, without impacting Apq12-ah topology or NE/ER localization. Overexpression of APQ12 but not apq12-ah triggers striking over-proliferation of the outer nuclear membrane (ONM)/ER and promotes accumulation of phosphatidic acid (PA) at the NE. Apq12 and Apq12-ah both associate with NPC biogenesis intermediates and removal of AαH increases both Brl1 levels and the interaction between Brl1 and Brr6. We conclude that the short amphipathic α-helix of Apq12 regulates the function of Brl1 and Brr6 and promotes PA accumulation at the NE possibly during NPC biogenesis.
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Affiliation(s)
- Wanlu Zhang
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Azqa Khan
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Jlenia Vitale
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Annett Neuner
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Kerstin Rink
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Christian Lüchtenborg
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Britta Brügger
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Thomas H. Söllner
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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10
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Gräf R, Grafe M, Meyer I, Mitic K, Pitzen V. The Dictyostelium Centrosome. Cells 2021; 10:cells10102657. [PMID: 34685637 PMCID: PMC8534566 DOI: 10.3390/cells10102657] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 10/01/2021] [Accepted: 10/02/2021] [Indexed: 12/13/2022] Open
Abstract
The centrosome of Dictyostelium amoebae contains no centrioles and consists of a cylindrical layered core structure surrounded by a corona harboring microtubule-nucleating γ-tubulin complexes. It is the major centrosomal model beyond animals and yeasts. Proteomics, protein interaction studies by BioID and superresolution microscopy methods led to considerable progress in our understanding of the composition, structure and function of this centrosome type. We discuss all currently known components of the Dictyostelium centrosome in comparison to other centrosomes of animals and yeasts.
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11
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Gardner JM, O'Toole E, Jaspersen SL. A mutation in budding yeast BRR6 affecting nuclear envelope insertion of the spindle pole body. MICROPUBLICATION BIOLOGY 2021; 2021. [PMID: 34549174 PMCID: PMC8449258 DOI: 10.17912/micropub.biology.000463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 09/13/2021] [Accepted: 09/13/2021] [Indexed: 11/06/2022]
Abstract
BRR6 and BRL1 are two paralogs that encode transmembrane proteins of the nuclear envelope (NE) involved in membrane fluidity and nuclear pore complex biogenesis in organisms that undergo a closed mitosis. We show that mutation of a conserved cysteine in the intralumenal domain of Saccharomyces cerevisiae Brr6p results in a novel temperature sensitive allele, brr6-Y100H, that arrests growth due to defects in spindle formation. Analysis of brr6-Y100H cells by electron tomography and Brr6p localization by super-resolution imaging supports the idea that Brr6p is involved in insertion of the newly duplicated spindle pole body into the NE.
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Affiliation(s)
| | - Eileen O'Toole
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
| | - Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, MO 64110.,Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160
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12
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Bestul AJ, Yu Z, Unruh JR, Jaspersen SL. Redistribution of centrosomal proteins by centromeres and Polo kinase controls partial nuclear envelope breakdown in fission yeast. Mol Biol Cell 2021; 32:1487-1500. [PMID: 34133218 PMCID: PMC8351742 DOI: 10.1091/mbc.e21-05-0239] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Proper mitotic progression in Schizosaccharomyces pombe requires partial nuclear envelope breakdown (NEBD) and insertion of the spindle pole body (SPB—yeast centrosome) to build the mitotic spindle. Linkage of the centromere to the SPB is vital to this process, but why that linkage is important is not well understood. Utilizing high-resolution structured illumination microscopy, we show that the conserved Sad1-UNC-84 homology-domain protein Sad1 and other SPB proteins redistribute during mitosis to form a ring complex around SPBs, which is a precursor for localized NEBD and spindle formation. Although the Polo kinase Plo1 is not necessary for Sad1 redistribution, it localizes to the SPB region connected to the centromere, and its activity is vital for redistribution of other SPB ring proteins and for complete NEBD at the SPB to allow for SPB insertion. Our results lead to a model in which centromere linkage to the SPB drives redistribution of Sad1 and Plo1 activation that in turn facilitate partial NEBD and spindle formation through building of a SPB ring structure.
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Affiliation(s)
- Andrew J Bestul
- Stowers Institute for Medical Research, Kansas City, MO 64110
| | - Zulin Yu
- Stowers Institute for Medical Research, Kansas City, MO 64110
| | - Jay R Unruh
- Stowers Institute for Medical Research, Kansas City, MO 64110
| | - Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, MO 64110.,Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160
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13
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Dey G, Baum B. Nuclear envelope remodelling during mitosis. Curr Opin Cell Biol 2021; 70:67-74. [PMID: 33421755 PMCID: PMC8129912 DOI: 10.1016/j.ceb.2020.12.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/07/2020] [Accepted: 12/09/2020] [Indexed: 12/20/2022]
Abstract
The defining feature of the eukaryotic cell, the nucleus, is bounded by a double envelope. This envelope and the nuclear pores within it play a critical role in separating the genome from the cytoplasm. It also presents cells with a challenge. How are cells to remodel the nuclear compartment boundary during mitosis without compromising nuclear function? In the two billion years since the emergence of the first cells with a nucleus, eukaryotes have evolved a range of strategies to do this. At one extreme, the nucleus is disassembled upon entry into mitosis and then reassembled anew in the two daughter cells. At the other, cells maintain an intact nuclear compartment boundary throughout the division process. In this review, we discuss common features of the division process that underpin remodelling mechanisms, the topological challenges involved and speculate on the selective pressures that may drive the evolution of distinct modes of division.
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Affiliation(s)
- Gautam Dey
- Cell Biology and Biophysics, European Molecular Biology Laboratory, 69117, Heidelberg, Germany.
| | - Buzz Baum
- Lab of Molecular Biology, Cambridge, CB2 0QH, United Kingdom; Lab for Molecular Cell Biology, UCL, London, WC1E 6BT, United Kingdom.
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14
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Jaspersen SL. Anatomy of the fungal microtubule organizing center, the spindle pole body. Curr Opin Struct Biol 2020; 66:22-31. [PMID: 33113389 DOI: 10.1016/j.sbi.2020.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 09/14/2020] [Accepted: 09/19/2020] [Indexed: 12/21/2022]
Abstract
The fungal kingdom is large and diverse, representing extremes of ecology, life cycles and morphology. At a cellular level, the diversity among fungi is particularly apparent at the spindle pole body (SPB). This nuclear envelope embedded structure, which is essential for microtubule nucleation, shows dramatically different morphologies between different fungi. However, despite phenotypic diversity, many SPB components are conserved, suggesting commonalities in structure, function and duplication. Here, I review the organization of the most well-studied SPBs and describe how advances in genomics, genetics and cell biology have accelerated knowledge of SPB architecture in other fungi, providing insights into microtubule nucleation and other processes conserved across eukaryotes.
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Affiliation(s)
- Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, MO 64110, United States; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, United States.
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15
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Dey G, Culley S, Curran S, Schmidt U, Henriques R, Kukulski W, Baum B. Closed mitosis requires local disassembly of the nuclear envelope. Nature 2020; 585:119-123. [PMID: 32848252 PMCID: PMC7610560 DOI: 10.1038/s41586-020-2648-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 05/21/2020] [Indexed: 01/15/2023]
Abstract
At the end of mitosis, eukaryotic cells must segregate the two copies of their replicated genome into two new nuclear compartments1. They do this either by first dismantling and later reassembling the nuclear envelope in an 'open mitosis' or by reshaping an intact nucleus and then dividing it into two in a 'closed mitosis'2,3. Mitosis has been studied in a wide variety of eukaryotes for more than a century4, but how the double membrane of the nuclear envelope is split into two at the end of a closed mitosis without compromising the impermeability of the nuclear compartment remains unknown5. Here, using the fission yeast Schizosaccharomyces pombe (a classical model for closed mitosis5), genetics, live-cell imaging and electron tomography, we show that nuclear fission is achieved via local disassembly of nuclear pores within the narrow bridge that links segregating daughter nuclei. In doing so, we identify the protein Les1, which is localized to the inner nuclear envelope and restricts the process of local nuclear envelope breakdown to the bridge midzone to prevent the leakage of material from daughter nuclei. The mechanism of local nuclear envelope breakdown in a closed mitosis therefore closely mirrors nuclear envelope breakdown in open mitosis3, revealing an unexpectedly high conservation of nuclear remodelling mechanisms across diverse eukaryotes.
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Affiliation(s)
- Gautam Dey
- MRC Laboratory for Molecular Cell Biology, London, UK.
| | - Siân Culley
- MRC Laboratory for Molecular Cell Biology, London, UK
| | | | - Uwe Schmidt
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
| | | | | | - Buzz Baum
- MRC Laboratory for Molecular Cell Biology, London, UK.
- Institute for the Physics of Living Systems, University College London, London, UK.
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16
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Expósito-Serrano M, Sánchez-Molina A, Gallardo P, Salas-Pino S, Daga RR. Selective Nuclear Pore Complex Removal Drives Nuclear Envelope Division in Fission Yeast. Curr Biol 2020; 30:3212-3222.e2. [DOI: 10.1016/j.cub.2020.05.066] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/24/2020] [Accepted: 05/20/2020] [Indexed: 01/09/2023]
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17
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Salas-Pino S, Daga RR. Spatiotemporal control of spindle disassembly in fission yeast. Cell Mol Life Sci 2019; 76:3543-3551. [PMID: 31129857 PMCID: PMC11105212 DOI: 10.1007/s00018-019-03139-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 04/29/2019] [Accepted: 05/07/2019] [Indexed: 12/20/2022]
Abstract
Maintenance of genomic stability during cell division is one of the most important cellular tasks, and it critically depends on the faithful replication of the genetic material and its equal partitioning into daughter cells, gametes, or spores in the case of yeasts. Defective mitotic spindle assembly and disassembly both result in changes in cellular ploidy that ultimately impinge proliferation fitness and might increase tumor malignancy. Although a great progress has been made in understanding how spindles are assembled to orchestrate chromosome segregation, much less is known about how they are disassembled once completed their function. Here, we review two recently uncovered mechanisms of spindle disassembly that operate at different stages of the fission yeast life cycle.
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Affiliation(s)
- Silvia Salas-Pino
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide-Consejo Superior de Investigaciones Científicas-Junta de Andalucia, Carretera de Utrera, km1, 41013, Seville, Spain.
| | - Rafael R Daga
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide-Consejo Superior de Investigaciones Científicas-Junta de Andalucia, Carretera de Utrera, km1, 41013, Seville, Spain.
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18
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Spindle assembly without spindle pole body insertion into the nuclear envelope in fission yeast meiosis. Chromosoma 2019; 128:267-277. [PMID: 31152193 DOI: 10.1007/s00412-019-00710-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 05/09/2019] [Accepted: 05/16/2019] [Indexed: 01/23/2023]
Abstract
Centrosomes represent the major microtubule organizing center (MTOC) in eukaryotic cells and are responsible for nucleation of the spindle, the vehicle of chromosome segregation. In human female meiosis, however, spindle assembly occurs in the absence of centrosomes or other MTOCs and microtubules are nucleated around chromosomes. In yeast, spindle formation in mitosis and meiosis depends on the activity of spindle pole bodies (SPBs), the functional equivalents of centrosomes; thus, SPBs and centrosomes use similar machineries to assemble spindles. Here, we develop a system to explore the molecular mechanisms supporting acentrosomal spindle formation using fission yeast meiosis as a model scenario. We achieve this situation by removing access of the SPBs to the nucleus after their duplication. Under these conditions, we observe self-assembly-based spindle formation in the nuclear environment, conferring an ability to segregate chromosomes independently of the SPBs. Our results open the possibility to utilize the experimental advantages of fission yeast for insights into the molecular basis of acentrosomal spindle formation in meiosis.
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19
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de Bruyn Kops A, Burke JE, Guthrie C. Brr6 plays a role in gene recruitment and transcriptional regulation at the nuclear envelope. Mol Biol Cell 2018; 29:2578-2590. [PMID: 30133335 PMCID: PMC6254580 DOI: 10.1091/mbc.e18-04-0258] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Correlation between transcriptional regulation and positioning of genes at the nuclear envelope is well established in eukaryotes, but the mechanisms involved are not well understood. We show that brr6-1, a mutant of the essential yeast envelope transmembrane protein Brr6p, impairs normal positioning and expression of the PAB1 and FUR4-GAL1,10,7 loci. Similarly, expression of a dominant negative nucleoplasmic Brr6 fragment in wild-type cells reproduced many of the brr6-1 effects. Histone chromatin immunoprecipitation (ChIP) experiments showed decreased acetylation at the key histone H4K16 residue in the FUR4-GAL1,10,7 region in brr6-1. Importantly, blocking deacetylation significantly suppressed selected brr6-1 phenotypes. ChIPseq with FLAG-tagged Brr6 fragments showed enrichment at FUR4 and several other genes that showed striking changes in brr6-1 RNAseq data. These associations depended on a Brr6 putative zinc finger domain. Importantly, artificially tethering the GAL1 locus to the envelope suppressed the brr6-1 effects on GAL1 and FUR4 expression and increased H4K16 acetylation between GAL1 and FUR4 in the mutant. Together these results argue that Brr6 interacts with chromatin, helping to maintain normal chromatin architecture and transcriptional regulation of certain loci at the nuclear envelope.
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Affiliation(s)
- Anne de Bruyn Kops
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143
| | - Jordan E Burke
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143
| | - Christine Guthrie
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143
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20
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Identification of the Novel Nup188-brr7 Allele in a Screen for Cold-Sensitive mRNA Export Mutants in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2018; 8:2991-3003. [PMID: 30021831 PMCID: PMC6118305 DOI: 10.1534/g3.118.200447] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The maturation and export of mRNA from the nucleus through the nuclear pore complex is critical for maintaining an appropriate proteome in all eukaryotic cells. Here we summarize a previously unpublished screen in S. cerevisiae that utilized an established dT50 in situ hybridization assay to identify cold-sensitive mutants that accumulated bulk poly A RNA in the nucleus. The screen identified seven mutants in six complementation groups, including the brr6-1 strain that we described previously. In addition to brr6-1, we identified novel alleles of the key transport gene GLE1 and NUP188, a component of the Nic96 nucleoporin complex. Notably, we show that the nup188-brr7 allele causes defects in select protein import pathways as well as mRNA export. Given recent structural and functional evidence linking the Nic96 complex to transport components, this mutant may be particularly useful to the transport community.
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21
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Duplication and Nuclear Envelope Insertion of the Yeast Microtubule Organizing Centre, the Spindle Pole Body. Cells 2018; 7:cells7050042. [PMID: 29748517 PMCID: PMC5981266 DOI: 10.3390/cells7050042] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 05/04/2018] [Accepted: 05/08/2018] [Indexed: 11/16/2022] Open
Abstract
The main microtubule organizing centre in the unicellular model organisms Saccharomyces cerevisiae and Schizosaccharomyces pompe is the spindle pole body (SPB). The SPB is a multilayer structure, which duplicates exactly once per cell cycle. Unlike higher eukaryotic cells, both yeast model organisms undergo mitosis without breakdown of the nuclear envelope (NE), a so-called closed mitosis. Therefore, in order to simultaneously nucleate nuclear and cytoplasmic MTs, it is vital to embed the SPB into the NE at least during mitosis, similarly to the nuclear pore complex (NPC). This review aims to embrace the current knowledge of the SPB duplication cycle with special emphasis on the critical step of the insertion of the new SPB into the NE.
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22
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23
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Zhang W, Neuner A, Rüthnick D, Sachsenheimer T, Lüchtenborg C, Brügger B, Schiebel E. Brr6 and Brl1 locate to nuclear pore complex assembly sites to promote their biogenesis. J Cell Biol 2018; 217:877-894. [PMID: 29439116 PMCID: PMC5839787 DOI: 10.1083/jcb.201706024] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 11/21/2017] [Accepted: 01/10/2018] [Indexed: 12/30/2022] Open
Abstract
The conserved paralogous Brr6 and Brl1 promote NPC biogenesis in an unclear manner. Here, Zhang et al. show that both transmembrane proteins transiently associate with NPC assembly intermediates and directly promote NPC biogenesis. The paralogous Brr6 and Brl1 are conserved integral membrane proteins of the nuclear envelope (NE) with an unclear role in nuclear pore complex (NPC) biogenesis. Here, we analyzed double-degron mutants of Brr6/Brl1 to understand this function. Depletion of Brr6 and Brl1 caused defects in NPC biogenesis, whereas the already assembled NPCs remained unaffected. This NPC biogenesis defect was not accompanied by a change in lipid composition. However, Brl1 interacted with Ndc1 and Nup188 by immunoprecipitation, and with transmembrane and outer and inner ring NPC components by split yellow fluorescent protein analysis, indicating a direct role in NPC biogenesis. Consistently, we found that Brr6 and Brl1 associated with a subpopulation of NPCs and emerging NPC assembly sites. Moreover, BRL1 overexpression affected NE morphology without a change in lipid composition and completely suppressed the nuclear pore biogenesis defect of nup116Δ and gle2Δ cells. We propose that Brr6 and Brl1 transiently associate with NPC assembly sites where they promote NPC biogenesis.
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Affiliation(s)
- Wanlu Zhang
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Annett Neuner
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Diana Rüthnick
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | | | | | - Britta Brügger
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
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24
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Abstract
The synthesis, processing and function of coding and non-coding RNA molecules and their interacting proteins has been the focus of a great deal of research that has boosted our understanding of key molecular pathways that underlie higher order events such as cell cycle control, development, innate immune response and the occurrence of genetic diseases. In this study, we have found that formamide preferentially weakens RNA related processes in vivo. Using a non-essential Schizosaccharomyces pombe gene deletion collection, we identify deleted loci that make cells sensitive to formamide. Sensitive deletions are significantly enriched in genes involved in RNA metabolism. Accordingly, we find that previously known temperature-sensitive splicing mutants become lethal in the presence of the drug under permissive temperature. Furthermore, in a wild type background, splicing efficiency is decreased and R-loop formation is increased in the presence of formamide. In addition, we have also isolated 35 formamide-sensitive mutants, many of which display remarkable morphology and cell cycle defects potentially unveiling new players in the regulation of these processes. We conclude that formamide preferentially targets RNA related processes in vivo, probably by relaxing RNA secondary structures and/or RNA-protein interactions, and can be used as an effective tool to characterize these processes.
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25
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Yang HJ, Iwamoto M, Hiraoka Y, Haraguchi T. Function of nuclear membrane proteins in shaping the nuclear envelope integrity during closed mitosis. J Biochem 2017; 161:471-477. [PMID: 28398483 DOI: 10.1093/jb/mvx020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 02/28/2017] [Indexed: 11/13/2022] Open
Abstract
The nuclear envelope (NE) not only protects the genome from being directly accessed by detrimental agents but also regulates genome organization. Breaches in NE integrity threaten genome stability and impede cellular function. Nonetheless, the NE constantly remodels, and NE integrity is endangered in dividing or differentiating cells. Specifically, in unicellular eukaryotes undergoing closed mitosis, the NE expands instead of breaking down during chromosome segregation. The newly assembling nuclear pore complexes (NPCs) penetrate the existing NE in interphase. A peculiar example of NE remodelling during nuclear differentiation in Tetrahymena involves formation of the redundant NE and clustered NPCs. Even under these conditions, the NE remains intact. Many recent studies on unicellular organisms have revealed that nuclear membrane proteins, such as LEM-domain proteins, play a role in maintaining NE integrity. This review summarizes and discusses how nuclear membrane proteins participate in NE integrity.
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Affiliation(s)
- Hui-Ju Yang
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Masaaki Iwamoto
- Advance ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan
| | - Yasushi Hiraoka
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan.,Advance ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan
| | - Tokuko Haraguchi
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan.,Advance ICT Research Institute Kobe, National Institute of Information and Communications Technology, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan
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26
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Cavanaugh AM, Jaspersen SL. Big Lessons from Little Yeast: Budding and Fission Yeast Centrosome Structure, Duplication, and Function. Annu Rev Genet 2017; 51:361-383. [PMID: 28934593 DOI: 10.1146/annurev-genet-120116-024733] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Centrosomes are a functionally conserved feature of eukaryotic cells that play an important role in cell division. The conserved γ-tubulin complex organizes spindle and astral microtubules, which, in turn, separate replicated chromosomes accurately into daughter cells. Like DNA, centrosomes are duplicated once each cell cycle. Although in some cell types it is possible for cell division to occur in the absence of centrosomes, these divisions typically result in defects in chromosome number and stability. In single-celled organisms such as fungi, centrosomes [known as spindle pole bodies (SPBs)] are essential for cell division. SPBs also must be inserted into the membrane because fungi undergo a closed mitosis in which the nuclear envelope (NE) remains intact. This poorly understood process involves events similar or identical to those needed for de novo nuclear pore complex assembly. Here, we review how analysis of fungal SPBs has advanced our understanding of centrosomes and NE events.
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Affiliation(s)
- Ann M Cavanaugh
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA;
| | - Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA; .,Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
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27
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Abstract
In this introduction we discuss some basic genetic tools and techniques that are used with the fission yeast Schizosaccharomyces pombe Genes commonly used for selection or as reporters are discussed, with an emphasis on genes that permit counterselection, intragenic complementation, or colony-color assays. S. pombe is most stable as a haploid organism. We describe its mating-type system, how to perform genetic crosses and methods for selecting and propagating diploids. We discuss the relative merits of tetrad dissection and random spore preparation in strain construction and genetic analyses. Finally, we present several types of mutant screens, with an evaluation of their respective strengths and limitations in the light of emerging technologies such as next-generation sequencing.
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Affiliation(s)
- Karl Ekwall
- Department of Biosciences and Nutrition, Karolinska Institute, Stockholm SE-141 83, Sweden;
| | - Geneviève Thon
- Department of Biology, University of Copenhagen, Copenhagen DK-2200, Denmark
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28
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LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells. Proc Natl Acad Sci U S A 2017; 114:E2166-E2175. [PMID: 28242692 PMCID: PMC5358359 DOI: 10.1073/pnas.1613916114] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The molecular mechanism for sealing newly formed nuclear envelopes was unclear until the recent discovery that endosomal sorting complexes required for transport III (ESCRT-III) proteins mediate this process. Cmp7p (CHMP7), in particular, was identified as an early acting factor that recruits other ESCRT-III proteins to the nuclear envelope. A fundamental aspect of the varied roles of ESCRT factors is their recruitment by site-specific adaptors, yet the central question of how the ESCRT machinery is targeted to nuclear membranes has remained outstanding. Our study identifies the inner nuclear membrane protein LEM2 as a key, conserved factor that recruits CHMP7 and downstream ESCRT-III proteins to breaches in the nuclear envelope. Endosomal sorting complexes required for transport III (ESCRT-III) proteins have been implicated in sealing the nuclear envelope in mammals, spindle pole body dynamics in fission yeast, and surveillance of defective nuclear pore complexes in budding yeast. Here, we report that Lem2p (LEM2), a member of the LEM (Lap2-Emerin-Man1) family of inner nuclear membrane proteins, and the ESCRT-II/ESCRT-III hybrid protein Cmp7p (CHMP7), work together to recruit additional ESCRT-III proteins to holes in the nuclear membrane. In Schizosaccharomyces pombe, deletion of the ATPase vps4 leads to severe defects in nuclear morphology and integrity. These phenotypes are suppressed by loss-of-function mutations that arise spontaneously in lem2 or cmp7, implying that these proteins may function upstream in the same pathway. Building on these genetic interactions, we explored the role of LEM2 during nuclear envelope reformation in human cells. We found that CHMP7 and LEM2 enrich at the same region of the chromatin disk periphery during this window of cell division and that CHMP7 can bind directly to the C-terminal domain of LEM2 in vitro. We further found that, during nuclear envelope formation, recruitment of the ESCRT factors CHMP7, CHMP2A, and IST1/CHMP8 all depend on LEM2 in human cells. We conclude that Lem2p/LEM2 is a conserved nuclear site-specific adaptor that recruits Cmp7p/CHMP7 and downstream ESCRT factors to the nuclear envelope.
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29
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Abstract
As a compartment border, the nuclear envelope (NE) needs to serve as both a protective membrane shell for the genome and a versatile communication interface between the nucleus and the cytoplasm. Despite its important structural role in sheltering the genome, the NE is a dynamic and highly adaptable boundary that changes composition during differentiation, deforms in response to mechanical challenges, can be repaired upon rupture and even rapidly disassembles and reforms during open mitosis. NE remodelling is fundamentally involved in cell growth, division and differentiation, and if perturbed can lead to devastating diseases such as muscular dystrophies or premature ageing.
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30
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Fernández-Álvarez A, Cooper JP. Chromosomes Orchestrate Their Own Liberation: Nuclear Envelope Disassembly. Trends Cell Biol 2016; 27:255-265. [PMID: 28024902 DOI: 10.1016/j.tcb.2016.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 11/08/2016] [Accepted: 11/10/2016] [Indexed: 12/13/2022]
Abstract
The mammalian nuclear division cycle is coordinated with nuclear envelope breakdown (NEBD), in which the entire nuclear envelope (NE) is dissolved to allow chromosomes to access their segregation vehicle, the spindle. In other eukaryotes, complete NEBD is replaced by localized disassembly or remodeling of the NE. Although the molecular mechanisms controlling NE disassembly are incompletely understood, coordinated cycles of modification of specific NE components drive breakdown. Here, we review the current state of knowledge regarding NE disassembly and argue for a role of chromosome-NE contacts in triggering initiation of NE disassembly and thereby, cell division.
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Affiliation(s)
- Alfonso Fernández-Álvarez
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Julia Promisel Cooper
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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31
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Fernández-Álvarez A, Bez C, O'Toole ET, Morphew M, Cooper JP. Mitotic Nuclear Envelope Breakdown and Spindle Nucleation Are Controlled by Interphase Contacts between Centromeres and the Nuclear Envelope. Dev Cell 2016; 39:544-559. [PMID: 27889481 DOI: 10.1016/j.devcel.2016.10.021] [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: 05/04/2016] [Revised: 09/02/2016] [Accepted: 10/26/2016] [Indexed: 10/20/2022]
Abstract
Faithful genome propagation requires coordination between nuclear envelope (NE) breakdown, spindle formation, and chromosomal events. The conserved linker of nucleoskeleton and cytoskeleton (LINC) complex connects fission yeast centromeres and the centrosome, across the NE, during interphase. During meiosis, LINC connects the centrosome with telomeres rather than centromeres. We previously showed that loss of telomere-LINC contacts compromises meiotic spindle formation. Here, we define the precise events regulated by telomere-LINC contacts and address the analogous possibility that centromeres regulate mitotic spindle formation. We develop conditionally inactivated LINC complexes in which the conserved SUN-domain protein Sad1 remains stable but severs interphase centromere-LINC contacts. Strikingly, the loss of such contacts abolishes spindle formation. We pinpoint the defect to a failure in the partial NE breakdown required for centrosome insertion into the NE, a step analogous to mammalian NE breakdown. Thus, interphase chromosome-LINC contacts constitute a cell-cycle control device linking nucleoplasmic and cytoplasmic events.
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Affiliation(s)
- Alfonso Fernández-Álvarez
- Telomere Biology Section, LBMB, National Cancer Institute, NIH, 9000 Rockville Pike, Bethesda, MD 20892, USA; Telomere Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.
| | - Cécile Bez
- Telomere Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Eileen T O'Toole
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Mary Morphew
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Julia Promisel Cooper
- Telomere Biology Section, LBMB, National Cancer Institute, NIH, 9000 Rockville Pike, Bethesda, MD 20892, USA; Telomere Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.
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32
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Makarova M, Oliferenko S. Mixing and matching nuclear envelope remodeling and spindle assembly strategies in the evolution of mitosis. Curr Opin Cell Biol 2016; 41:43-50. [PMID: 27062548 PMCID: PMC7100904 DOI: 10.1016/j.ceb.2016.03.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/20/2016] [Accepted: 03/23/2016] [Indexed: 12/11/2022]
Abstract
In eukaryotes, cellular genome is enclosed inside a membrane-bound organelle called the nucleus. The nucleus compartmentalizes genome replication, repair and expression, keeping these activities separated from protein synthesis and other metabolic processes. Each proliferative division, the duplicated chromosomes must be equipartitioned between the daughter cells and this requires precise coordination between assembly of the microtubule-based mitotic spindle and nuclear remodeling. Here we review a surprising variety of strategies used by modern eukaryotes to manage these processes and discuss possible mechanisms that might have led to the emergence of this diversity in evolution.
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Affiliation(s)
- Maria Makarova
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK
| | - Snezhana Oliferenko
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, UK.
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33
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Hagan IM, Grallert A, Simanis V. Synchronizing Progression of Schizosaccharomyces pombe Cells from Prophase through Mitosis and into S Phase with nda3-KM311 Arrest Release. Cold Spring Harb Protoc 2016; 2016:2016/8/pdb.prot091256. [PMID: 27480719 DOI: 10.1101/pdb.prot091256] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Here, we describe how the rapid reversibility of the nda3-KM311 cold-sensitive β-tubulin mutation was optimized by Mitsuhiro Yanagida's laboratory to synchronize mitotic progression in an entire cell population. The inability to form microtubules following the loss of β-tubulin function at 20°C triggers the spindle assembly checkpoint, which arrests mitotic progression. Restoration of β-tubulin function by rewarming to 30°C (or higher) releases the arrest, generating a highly synchronous progression through mitosis. The viability of nda3-KM311 strains at 30°C makes it feasible to generate double mutants between nda3-KM311 and any temperature-sensitive mutant that can also grow at 30°C. These double mutants can be used in reciprocal shift analyses, in which cold-induced early mitotic arrest is relieved by a shift to 36°C, which then inactivates the product of the second mutant gene. The addition of microtubule depolymerizing drugs before the return to 36°C will maintain checkpoint signaling at 36°C transiently, permitting analysis of the impact of temperature-sensitive mutations on checkpoint function. Silencing the checkpoint of nda3-KM311-arrested cells at 20°C through chemical inhibition of aurora kinase is a powerful way to study checkpoint recovery pathways and mitotic exit without anaphase.
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Affiliation(s)
- Iain M Hagan
- CRUK Cell Division Group, Cancer Research UK Manchester Institute, University of Manchester, Manchester M20 4BX, United Kingdom
| | - Agnes Grallert
- CRUK Cell Division Group, Cancer Research UK Manchester Institute, University of Manchester, Manchester M20 4BX, United Kingdom
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Meseroll RA, Cohen-Fix O. The Malleable Nature of the Budding Yeast Nuclear Envelope: Flares, Fusion, and Fenestrations. J Cell Physiol 2016; 231:2353-60. [PMID: 26909870 DOI: 10.1002/jcp.25355] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 02/19/2016] [Indexed: 11/10/2022]
Abstract
In eukaryotes, the nuclear envelope (NE) physically separates nuclear components and activities from rest of the cell. The NE also provides rigidity to the nucleus and contributes to chromosome organization. At the same time, the NE is highly dynamic; it must change shape and rearrange its components during development and throughout the cell cycle, and its morphology can be altered in response to mutation and disease. Here we focus on the NE of budding yeast, Saccharomyces cerevisiae, which has several unique features: it remains intact throughout the cell cycle, expands symmetrically during interphase, elongates during mitosis and, expands asymmetrically during mitotic delay. Moreover, its NE is safely breached during mating and when large structures, such as nuclear pore complexes and the spindle pole body, are embedded into its double membrane. The budding yeast NE lacks lamins and yet the nucleus is capable of maintaining a spherical shape throughout interphase. Despite these eccentricities, studies of the budding yeast NE have uncovered interesting, and likely conserved, processes that contribute to NE dynamics. In particular, we discuss the processes that drive and enable NE expansion and the dramatic changes in the NE that lead to extensions and fenestrations. J. Cell. Physiol. 231: 2353-2360, 2016. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.
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Affiliation(s)
- Rebecca A Meseroll
- The Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Orna Cohen-Fix
- The Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
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Yeast Integral Membrane Proteins Apq12, Brl1, and Brr6 Form a Complex Important for Regulation of Membrane Homeostasis and Nuclear Pore Complex Biogenesis. EUKARYOTIC CELL 2015; 14:1217-27. [PMID: 26432634 DOI: 10.1128/ec.00101-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/01/2015] [Indexed: 11/20/2022]
Abstract
Proper functioning of intracellular membranes is critical for many cellular processes. A key feature of membranes is their ability to adapt to changes in environmental conditions by adjusting their composition so as to maintain constant biophysical properties, including fluidity and flexibility. Similar changes in the biophysical properties of membranes likely occur when intracellular processes, such as vesicle formation and fusion, require dramatic changes in membrane curvature. Similar modifications must also be made when nuclear pore complexes (NPCs) are constructed within the existing nuclear membrane, as occurs during interphase in all eukaryotes. Here we report on the role of the essential nuclear envelope/endoplasmic reticulum (NE/ER) protein Brl1 in regulating the membrane composition of the NE/ER. We show that Brl1 and two other proteins characterized previously-Brr6, which is closely related to Brl1, and Apq12-function together and are required for lipid homeostasis. All three transmembrane proteins are localized to the NE and can be coprecipitated. As has been shown for mutations affecting Brr6 and Apq12, mutations in Brl1 lead to defects in lipid metabolism, increased sensitivity to drugs that inhibit enzymes involved in lipid synthesis, and strong genetic interactions with mutations affecting lipid metabolism. Mutations affecting Brl1 or Brr6 or the absence of Apq12 leads to hyperfluid membranes, because mutant cells are hypersensitive to agents that increase membrane fluidity. We suggest that the defects in nuclear pore complex biogenesis and mRNA export seen in these mutants are consequences of defects in maintaining the biophysical properties of the NE.
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Webster BM, Lusk CP. Border Safety: Quality Control at the Nuclear Envelope. Trends Cell Biol 2015; 26:29-39. [PMID: 26437591 DOI: 10.1016/j.tcb.2015.08.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/27/2015] [Accepted: 08/07/2015] [Indexed: 10/23/2022]
Abstract
The unique biochemical identity of the nuclear envelope confers its capacity to establish a barrier that protects the nuclear compartment and directly contributes to nuclear function. Recent work uncovered quality control mechanisms employing the endosomal sorting complexes required for transport (ESCRT) machinery and a new arm of endoplasmic reticulum-associated protein degradation (ERAD) to counteract the unfolding, damage, or misassembly of nuclear envelope proteins and ensure the integrity of the nuclear envelope membranes. Moreover, cells have the capacity to recognize and triage defective nuclear pore complexes to prevent their inheritance and preserve the longevity of progeny. These mechanisms serve to highlight the diverse strategies used by cells to maintain nuclear compartmentalization; we suggest they mitigate the progression and severity of diseases associated with nuclear envelope malfunction such as the laminopathies.
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Zhang D, Oliferenko S. Tts1, the fission yeast homologue of the TMEM33 family, functions in NE remodeling during mitosis. Mol Biol Cell 2014; 25:2970-83. [PMID: 25103238 PMCID: PMC4230586 DOI: 10.1091/mbc.e13-12-0729] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The evolutionarily conserved eukaryotic TMEM33-family protein Tts1 functions in promoting mitotic spindle pole body–nuclear envelope insertion and modulating mitotic nuclear pore complex distribution in Schizosaccharomyces pombe. The structural features of Tts1 important for its function in distinct aspects of membrane remodeling are identified. The fission yeast Schizosaccharomyces pombe undergoes “closed” mitosis in which the nuclear envelope (NE) stays intact throughout chromosome segregation. Here we show that Tts1, the fission yeast TMEM33 protein that was previously implicated in organizing the peripheral endoplasmic reticulum (ER), also functions in remodeling the NE during mitosis. Tts1 promotes insertion of spindle pole bodies (SPBs) in the NE at the onset of mitosis and modulates distribution of the nuclear pore complexes (NPCs) during mitotic NE expansion. Structural features that drive partitioning of Tts1 to the high-curvature ER domains are crucial for both aspects of its function. An amphipathic helix located at the C-terminus of Tts1 is important for ER shaping and modulating the mitotic NPC distribution. Of interest, the evolutionarily conserved residues at the luminal interface of the third transmembrane region function specifically in promoting SPB-NE insertion. Our data illuminate cellular requirements for remodeling the NE during “closed” nuclear division and provide insight into the structure and functions of the eukaryotic TMEM33 family.
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Affiliation(s)
- Dan Zhang
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604
| | - Snezhana Oliferenko
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 Department of Biological Sciences, National University of Singapore, Singapore 117604
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38
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Wälde S, King MC. The KASH protein Kms2 coordinates mitotic remodeling of the spindle pole body. J Cell Sci 2014; 127:3625-40. [PMID: 24963130 DOI: 10.1242/jcs.154997] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Defects in the biogenesis of the spindle pole body (SPB), the yeast centrosome equivalent, can lead to monopolar spindles and mitotic catastrophe. The KASH domain protein Kms2 and the SUN domain protein Sad1 colocalize within the nuclear envelope at the site of SPB attachment during interphase and at the spindle poles during mitosis in Schizosaccharomyces pombe. We show that Kms2 interacts with the essential SPB components Cut12 and Pcp1 and the Polo kinase Plo1. Depletion of Kms2 delays mitotic entry and leads to defects in the insertion of the SPB into the nuclear envelope, disrupting stable bipolar spindle formation. These effects are mediated in part by a delay in the recruitment of Plo1 to the SPB at mitotic entry. Plo1 activity supports mitotic SPB remodeling by driving a burst of incorporation of Cut12 and Pcp1. Thus, a fission yeast SUN-KASH complex plays an important role in supporting the remodeling of the SPB at mitotic entry.
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Affiliation(s)
- Sarah Wälde
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Megan C King
- Department of Cell Biology, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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Tay YD, Patel A, Kaemena DF, Hagan IM. Mutation of a conserved residue enhances the sensitivity of analogue-sensitised kinases to generate a novel approach to the study of mitosis in fission yeast. J Cell Sci 2013; 126:5052-61. [PMID: 23986474 DOI: 10.1242/jcs.135301] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The chemical genetic strategy in which mutational enlargement of the ATP-binding site sensitises of a protein kinase to bulky ATP analogues has proved to be an elegant tool for the generation of conditional analogue-sensitive kinase alleles in a variety of model organisms. Here, we describe a novel substitution mutation in the kinase domain that can enhance the sensitivity of analogue-sensitive kinases. Substitution of a methionine residue to phenylalanine in the +2 position after HRDLKxxN motif of the subdomain VIb within the kinase domain markedly increased the sensitivities of the analogue-sensitive kinases to ATP analogues in three out of five S. pombe kinases (i.e. Plo1, Orb5 and Wee1) that harbor this conserved methionine residue. Kinome alignment established that a methionine residue is found at this site in 5-9% of kinases in key model organisms, suggesting that a broader application of this structural modification may enhance ATP analogue sensitivity of analogue-sensitive kinases in future studies. We also show that the enhanced sensitivity of the wee1.as8 allele in a cdc25.22 background can be exploited to generate highly synchronised mitotic and S phase progression at 36°C. Proof-of-principle experiments show how this novel synchronisation technique will prove of great use in the interrogation of the mitotic or S-phase functions through temperature sensitivity mutation of molecules of interest in fission yeast.
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Affiliation(s)
- Ye-Dee Tay
- CRUK Cell Division Group, Paterson Institute for Cancer Research, Wilmslow Road, Manchester M20 4BX, UK
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Smoyer CJ, Jaspersen SL. Breaking down the wall: the nuclear envelope during mitosis. Curr Opin Cell Biol 2013; 26:1-9. [PMID: 24529240 DOI: 10.1016/j.ceb.2013.08.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 08/13/2013] [Accepted: 08/13/2013] [Indexed: 11/28/2022]
Abstract
A defining feature of eukaryotic cells is the nucleus, which houses the genome inside the nuclear envelope (NE): a double lipid bilayer that separates the nuclear and cytoplasmic materials. Although the NE is commonly viewed as a barrier that is overcome only by embedded nuclear pore complexes (NPCs) that facilitate nuclear-cytoplasmic trafficking, recent work in a wide range of eukaryotes reveals that the NE is a dynamic organelle that is modified each time the cell divides to ultimately establish two functional daughter nuclei. Here, we review how studies of divergent mitotic strategies have helped elucidate common properties of NE biology that allow it to function throughout the cell cycle.
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Affiliation(s)
- Christine J Smoyer
- Stowers Institute for Medical Research, Kansas City, MO 64110, United States
| | - Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, MO 64110, United States; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, United States.
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41
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Poring over pores: nuclear pore complex insertion into the nuclear envelope. Trends Biochem Sci 2013; 38:292-301. [DOI: 10.1016/j.tibs.2013.04.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Revised: 03/29/2013] [Accepted: 04/02/2013] [Indexed: 11/18/2022]
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Abstract
Faithful transmission of genetic material is essential for the survival of all organisms. Eukaryotic chromosome segregation is driven by the kinetochore that assembles onto centromeric DNA to capture spindle microtubules and govern the movement of chromosomes. Its molecular mechanism has been actively studied in conventional model eukaryotes, such as yeasts, worms, flies and human. However, these organisms are closely related in the evolutionary time scale and it therefore remains unclear whether all eukaryotes use a similar mechanism. The evolutionary origins of the segregation apparatus also remain enigmatic. To gain insights into these questions, it is critical to perform comparative studies. Here, we review our current understanding of the mitotic mechanism in Trypanosoma brucei, an experimentally tractable kinetoplastid parasite that branched early in eukaryotic history. No canonical kinetochore component has been identified, and the design principle of kinetochores might be fundamentally different in kinetoplastids. Furthermore, these organisms do not appear to possess a functional spindle checkpoint that monitors kinetochore-microtubule attachments. With these unique features and the long evolutionary distance from other eukaryotes, understanding the mechanism of chromosome segregation in T. brucei should reveal fundamental requirements for the eukaryotic segregation machinery, and may also provide hints about the origin and evolution of the segregation apparatus.
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Affiliation(s)
- Bungo Akiyoshi
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
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Genetic analysis of Mps3 SUN domain mutants in Saccharomyces cerevisiae reveals an interaction with the SUN-like protein Slp1. G3-GENES GENOMES GENETICS 2012; 2:1703-18. [PMID: 23275891 PMCID: PMC3516490 DOI: 10.1534/g3.112.004614] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 10/26/2012] [Indexed: 01/16/2023]
Abstract
In virtually all eukaryotic cells, protein bridges formed by the conserved inner nuclear membrane SUN (for Sad1-UNC-84) domain-containing proteins and their outer nuclear membrane binding partners span the nuclear envelope (NE) to connect the nucleoplasm and cytoplasm. These linkages are important for chromosome movements within the nucleus during meiotic prophase and are essential for nuclear migration and centrosome attachment to the NE. In Saccharomyces cerevisiae, MPS3 encodes the sole SUN protein. Deletion of MPS3 or the conserved SUN domain is lethal in three different genetic backgrounds. Mutations in the SUN domain result in defects in duplication of the spindle pole body, the yeast centrosome-equivalent organelle. A genome-wide screen for mutants that exhibited synthetic fitness defects in combination with mps3 SUN domain mutants yielded a large number of hits in components of the spindle apparatus and the spindle checkpoint. Mutants in lipid metabolic processes and membrane organization also exacerbated the growth defects of mps3 SUN domain mutants, pointing to a role for Mps3 in nuclear membrane organization. Deletion of SLP1 or YER140W/EMP65 (for ER membrane protein of 65 kDa) aggravated growth of mps3 SUN domain mutants. Slp1 and Emp65 form an ER-membrane associated protein complex that is not required directly for spindle pole body duplication or spindle assembly. Rather, Slp1 is involved in Mps3 localization to the NE.
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Zhang D, Oliferenko S. Remodeling the nuclear membrane during closed mitosis. Curr Opin Cell Biol 2012; 25:142-8. [PMID: 23040820 DOI: 10.1016/j.ceb.2012.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 09/06/2012] [Accepted: 09/10/2012] [Indexed: 11/28/2022]
Abstract
The mitotic spindle assembly and chromosome segregation in eukaryotes must be coordinated with the nuclear envelope (NE) remodeling. In a so-called 'open' mitosis the envelope of the mother nucleus is dismantled allowing the cytoplasmic spindle microtubules to capture the chromosomes. Alternatively, cells undergoing 'closed' mitosis assemble the intranuclear spindle and divide the nucleus without ever losing the nucleocytoplasmic compartmentalization. Here we focus on the mechanisms underlying mitotic NE dynamics in unicellular eukaryotes undergoing a closed nuclear division, paying specific attention to the emerging roles of the lipid biosynthesis machinery in this process. We argue that lessons learned in these organisms may be generally relevant to understanding the NE remodeling and the evolution of mitotic mechanisms throughout the eukaryotic domain.
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Affiliation(s)
- Dan Zhang
- Temasek Life Sciences Laboratory, 1 Research Link, Singapore 117604, Singapore
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45
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Functional repurposing revealed by comparing S. pombe and S. cerevisiae genetic interactions. Cell 2012; 149:1339-52. [PMID: 22682253 PMCID: PMC3613983 DOI: 10.1016/j.cell.2012.04.028] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 03/08/2012] [Accepted: 04/02/2012] [Indexed: 12/12/2022]
Abstract
We present a genetic interaction map of pairwise measures including ∼40% of nonessential S. pombe genes. By comparing interaction maps for fission and budding yeast, we confirmed widespread conservation of genetic relationships within and between complexes and pathways. However, we identified an important subset of orthologous complexes that have undergone functional "repurposing": the evolution of divergent functions and partnerships. We validated three functional repurposing events in S. pombe and mammalian cells and discovered that (1) two lumenal sensors of misfolded ER proteins, the kinase/nuclease Ire1 and the glucosyltransferase Gpt1, act together to mount an ER stress response; (2) ESCRT factors regulate spindle-pole-body duplication; and (3) a membrane-protein phosphatase and kinase complex, the STRIPAK complex, bridges the cis-Golgi, the centrosome, and the outer nuclear membrane to direct mitotic progression. Each discovery opens new areas of inquiry and-together-have implications for model organism-based research and the evolution of genetic systems.
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46
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Integrity and function of the Saccharomyces cerevisiae spindle pole body depends on connections between the membrane proteins Ndc1, Rtn1, and Yop1. Genetics 2012; 192:441-55. [PMID: 22798490 DOI: 10.1534/genetics.112.141465] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The nuclear envelope in Saccharomyces cerevisiae harbors two essential macromolecular protein assemblies: the nuclear pore complexes (NPCs) that enable nucleocytoplasmic transport, and the spindle pole bodies (SPBs) that mediate chromosome segregation. Previously, based on metazoan and budding yeast studies, we reported that reticulons and Yop1/DP1 play a role in the early steps of de novo NPC assembly. Here, we examined if Rtn1 and Yop1 are required for SPB function in S. cerevisiae. Electron microscopy of rtn1Δ yop1Δ cells revealed lobular abnormalities in SPB structure. Using an assay that monitors lateral expansion of the SPB central layer, we found that rtn1Δ yop1Δ SPBs had decreased connections to the NE compared to wild type, suggesting that SPBs are less stable in the NE. Furthermore, large budded rtn1Δ yop1Δ cells exhibited a high incidence of short mitotic spindles, which were frequently misoriented with respect to the mother-daughter axis. This correlated with cytoplasmic microtubule defects. We found that overexpression of the SPB insertion factors NDC1, MPS2, or BBP1 rescued the SPB defects observed in rtn1Δ yop1Δ cells. However, only overexpression of NDC1, which is also required for NPC biogenesis, rescued both the SPB and NPC associated defects. Rtn1 and Yop1 also physically interacted with Ndc1 and other NPC membrane proteins. We propose that NPC and SPB biogenesis are altered in cells lacking Rtn1 and Yop1 due to competition between these complexes for Ndc1, an essential common component of both NPCs and SPBs.
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Jaspersen SL, Ghosh S. Nuclear envelope insertion of spindle pole bodies and nuclear pore complexes. Nucleus 2012; 3:226-36. [PMID: 22572959 PMCID: PMC3414398 DOI: 10.4161/nucl.20148] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The defining feature of eukaryotic cells is the double lipid bilayer of the nuclear envelope (NE) that serves as a physical barrier separating the genome from the cytosol. Nuclear pore complexes (NPCs) are embedded in the NE to facilitate transport of proteins and other macromolecules into and out of the nucleus. In fungi and early embryos where the NE does not completely breakdown during mitosis, microtubule-organizing centers such as the spindle pole body (SPB) must also be inserted into the NE to facilitate organization of the mitotic spindle. Several recent papers have shed light on the mechanism by which SPB complexes are inserted into the NE. An unexpected link between the SPB and NPCs suggests that assembly of these NE complexes is tightly coordinated. We review the findings of these reports in light of our current knowledge of SPB, NPC and NE structure, assembly and function.
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Affiliation(s)
- Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, MO, USA.
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