The Spindle Pole Bodies Facilitate Nuclear Envelope Division during Closed Mitosis in Fission Yeast

In the fission yeast Schizosaccharomyces pombe, the onset of septum formation is induced by a signal transduction network involving several protein kinases and a GTPase switch. One of the roles of the spg1p GTPase is to localise the cdc7p protein kinase to the poles of the mitotic spindle, from where the onset of septation is thought to be signalled at the end of mitosis. Immunofluorescence studies have shown that cdc7p is located on both spindle pole bodies early in mitosis, but only on one during the later stages of anaphase. This is mediated by inactivation of spg1p on one pole before the other. The GAP for spg1p is a complex of two proteins, cdc16p and byr4p. Localisation of cdc16p and byr4p by indirect immunofluorescence during the mitotic cell cycle showed that both proteins are present on the spindle pole body in interphase cells. During mitosis, byr4p is seen first on both poles of the spindle, then on only one. This occurs prior to cdc7p becoming asymmetric. In contrast, the signal due to cdc16p decreases to a low level during early mitosis, before being seen strongly on the same pole as byr4p. Double staining indicates that this is the opposite pole to that which retains cdc7p in late anaphase. Examination of the effect of inactivating cdc16p at various stages of the cell cycle suggests that cdc16p, together with cdc2p plays a role in restraining septum formation during interphase. The asymmetric inactivation of spg1p is mediated by recruitment of the cdc16p-byr4p GAP to one of the poles of the spindle before the other, and the asymmetry of the spindle pole bodies may be established early during mitosis. Moreover, the spindle pole bodies appear to be non-equivalent even after division has been completed.

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The Three Fungal Transmembrane Nuclear Pore Complex Proteins of Aspergillus nidulans Are Dispensable in the Presence of an Intact An-Nup84-120 Complex

Molecular Biology of the Cell ◽

10.1091/mbc.e08-06-0628 ◽

2009 ◽

Vol 20 (2) ◽

pp. 616-630 ◽

Cited By ~ 73

Author(s):

Hui-Lin Liu ◽

Colin P.C. De Souza ◽

Aysha H. Osmani ◽

Stephen A. Osmani

Keyword(s):

High Temperature ◽

Nuclear Envelope ◽

Aspergillus Nidulans ◽

Nuclear Pore Complex ◽

Mitotic Spindle ◽

Spindle Pole ◽

Nuclear Pore ◽

Nuclear Pore Complexes ◽

Spindle Pole Bodies ◽

Pore Complexes

In Aspergillus nidulans nuclear pore complexes (NPCs) undergo partial mitotic disassembly such that 12 NPC proteins (Nups) form a core structure anchored across the nuclear envelope (NE). To investigate how the NPC core is maintained, we affinity purified the major core An-Nup84-120 complex and identified two new fungal Nups, An-Nup37 and An-ELYS, previously thought to be vertebrate specific. During mitosis the An-Nup84-120 complex locates to the NE and spindle pole bodies but, unlike vertebrate cells, does not concentrate at kinetochores. We find that mutants lacking individual An-Nup84-120 components are sensitive to the membrane destabilizer benzyl alcohol (BA) and high temperature. Although such mutants display no defects in mitotic spindle formation, they undergo mitotic specific disassembly of the NPC core and transient aggregation of the mitotic NE, suggesting the An-Nup84-120 complex might function with membrane. Supporting this, we show cells devoid of all known fungal transmembrane Nups (An-Ndc1, An-Pom152, and An-Pom34) are viable but that An-ndc1 deletion combined with deletion of individual An-Nup84-120 components is either lethal or causes sensitivity to treatments expected to destabilize membrane. Therefore, the An-Nup84-120 complex performs roles, perhaps at the NPC membrane as proposed previously, that become essential without the An-Ndc1 transmembrane Nup.

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γ-Tubulin complex-mediated anchoring of spindle microtubules to spindle-pole bodies requires Msd1 in fission yeast

Nature Cell Biology ◽

10.1038/ncb1593 ◽

2007 ◽

Vol 9 (6) ◽

pp. 646-653 ◽

Cited By ~ 41

Author(s):

Mika Toya ◽

Masamitsu Sato ◽

Uta Haselmann ◽

Kazuhide Asakawa ◽

Damian Brunner ◽

...

Keyword(s):

Fission Yeast ◽

Spindle Pole ◽

Spindle Pole Bodies ◽

Spindle Microtubules

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Synergistic role of fission yeast Alp16GCP6 and Mzt1MOZART1 in γ-tubulin complex recruitment to mitotic spindle pole bodies and spindle assembly

Molecular Biology of the Cell ◽

10.1091/mbc.e15-08-0577 ◽

2016 ◽

Vol 27 (11) ◽

pp. 1753-1763 ◽

Cited By ~ 19

Author(s):

Hirohisa Masuda ◽

Takashi Toda

Keyword(s):

Fission Yeast ◽

Mitotic Spindle ◽

Spindle Assembly Checkpoint ◽

Synthetic Lethality ◽

Spindle Assembly ◽

Spindle Pole ◽

Microtubule Assembly ◽

Spindle Microtubule ◽

Spindle Pole Bodies ◽

Mitotic Spindle Pole

In fission yeast, γ-tubulin ring complex (γTuRC)–specific components Gfh1GCP4, Mod21GCP5, and Alp16GCP6 are nonessential for cell growth. Of these deletion mutants, only alp16Δ shows synthetic lethality with temperature-sensitive mutants of Mzt1MOZART1, a component of the γTuRC required for recruitment of the complex to microtubule-organizing centers. γ-Tubulin small complex levels at mitotic spindle pole bodies (SPBs, the centrosome equivalent in fungi) and microtubule levels for preanaphase spindles are significantly reduced in alp16Δ cells but not in gfh1Δ or mod21Δ cells. Furthermore, alp16Δ cells often form monopolar spindles and frequently lose a minichromosome when the spindle assembly checkpoint is inactivated. Alp16GCP6 promotes Mzt1-dependent γTuRC recruitment to mitotic SPBs and enhances spindle microtubule assembly in a manner dependent on its expression levels. Gfh1GCP4 and Mod21GCP5 are not required for Alp16GCP6-dependent γTuRC recruitment. Mzt1 has an additional role in the activation of the γTuRC for spindle microtubule assembly. The ratio of Mzt1 to γTuRC levels for preanaphase spindles is higher than at other stages of the cell cycle. Mzt1 overproduction enhances spindle microtubule assembly without affecting γTuRC levels at mitotic SPBs. We propose that Alp16GCP6 and Mzt1 act synergistically for efficient bipolar spindle assembly to ensure faithful chromosome segregation.

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LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1613916114 ◽

2017 ◽

Vol 114 (11) ◽

pp. E2166-E2175 ◽

Cited By ~ 73

Author(s):

Mingyu Gu ◽

Dollie LaJoie ◽

Opal S. Chen ◽

Alexander von Appen ◽

Mark S. Ladinsky ◽

...

Keyword(s):

Nuclear Envelope ◽

Fission Yeast ◽

Nuclear Membrane ◽

Spindle Pole Body ◽

Spindle Pole ◽

Human Cells ◽

Nuclear Pore ◽

Nuclear Pore Complexes ◽

Loss Of Function

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. InSchizosaccharomyces pombe, deletion of the ATPasevps4leads to severe defects in nuclear morphology and integrity. These phenotypes are suppressed by loss-of-function mutations that arise spontaneously inlem2orcmp7, 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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The ultrastructure of nuclear division in Armillaria mellea: meiosis

Canadian Journal of Botany ◽

10.1139/b79-235 ◽

1979 ◽

Vol 57 (18) ◽

pp. 1860-1872 ◽

Cited By ~ 12

Author(s):

Diane Cope Peabody ◽

Jerome J. Motta

Keyword(s):

Nuclear Envelope ◽

Membrane Structure ◽

Nuclear Division ◽

Spindle Pole ◽

Armillaria Mellea ◽

Spindle Pole Bodies ◽

Late Telophase ◽

Meiosis I ◽

Metaphase I

Meiosis I in isolates of Armillaria mellea in which subhymenial hyphae are uninucleate and lack clamp connections was examined ultrastructurally. Although the overall pattern of development and basidiosporogenesis appears similar to other Homobasidiomycetes it was observed that spindle pole bodies are predominantly monoglobular and are associated with a unique membrane structure of the subtending nuclear envelope. The nuclear envelope also disappears at metaphase I and reforms by the coalescence of membrane fragments around the compacted chromatin at late telophase I. The significance of these features in relation to other Basidiomycetes is briefly discussed.

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Tts1, the fission yeast homologue of the TMEM33 family, functions in NE remodeling during mitosis

Molecular Biology of the Cell ◽

10.1091/mbc.e13-12-0729 ◽

2014 ◽

Vol 25 (19) ◽

pp. 2970-2983 ◽

Cited By ~ 22

Author(s):

Dan Zhang ◽

Snezhana Oliferenko

Keyword(s):

Fission Yeast ◽

Structural Features ◽

Spindle Pole ◽

Nuclear Pore ◽

Nuclear Pore Complexes ◽

C Terminus ◽

Spindle Pole Bodies ◽

Evolutionarily Conserved ◽

Pore Complexes ◽

Insight Into

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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Yeast-Like Endosymbionts in an Ichneumonid Wasp

Zeitschrift für Naturforschung C ◽

10.1515/znc-1984-3-425 ◽

1984 ◽

Vol 39 (3-4) ◽

pp. 322-326 ◽

Cited By ~ 12

Author(s):

J. Middeldorf ◽

A. Ruthmann

Keyword(s):

Nuclear Envelope ◽

Spindle Pole ◽

Next Generation ◽

Vegetative Cells ◽

Host Cytoplasm ◽

Spindle Pole Bodies ◽

Pathogenic Infection

Vegetative cells and spores of a yeast-like micro organism found in various tissues in both sexes of the ichneumonid wasp Pimpla turionellae are passed to the offspring by infection of the oocytes. Because of their intranuclearspindles with spindle pole bodies associated with the nuclear envelope as pole structures, the microorganisms are thought to be yeasts or closely related to yeasts. The high vitality and fertility of the wasps seem to exclude a pathogenic infection. Both the passage of vesicles from the microorganisms to the host cytoplasm and their transmission to the next generation by the oocytes point to anendosymbiotic relationship

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The Meiosis-Specific Sid2p-related Protein Slk1p Regulates Forespore Membrane Assembly in Fission Yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e07-10-1060 ◽

2008 ◽

Vol 19 (9) ◽

pp. 3676-3690 ◽

Cited By ~ 12

Author(s):

Hongyan Yan ◽

Wanzhong Ge ◽

Ting Gang Chew ◽

Jeng Yeong Chow ◽

Dannel McCollum ◽

...

Keyword(s):

Fission Yeast ◽

Essential Role ◽

Spindle Pole ◽

Dependent Manner ◽

Related Protein ◽

Membrane Assembly ◽

Daughter Cells ◽

Spindle Pole Bodies ◽

Septation Initiation Network ◽

Secretory Apparatus

Cytokinesis in all organisms involves the creation of membranous barriers that demarcate individual daughter cells. In fission yeast, a signaling module termed the septation initiation network (SIN) plays an essential role in the assembly of new membranes and cell wall during cytokinesis. In this study, we have characterized Slk1p, a protein-kinase related to the SIN component Sid2p. Slk1p is expressed specifically during meiosis and localizes to the spindle pole bodies (SPBs) during meiosis I and II in a SIN-dependent manner. Slk1p also localizes to the forespore membrane during sporulation. Cells lacking Slk1p display defects associated with sporulation, leading frequently to the formation of asci with smaller and/or fewer spores. The ability of slk1Δ cells to sporulate, albeit inefficiently, is fully abolished upon compromise of function of Sid2p, suggesting that Slk1p and Sid2p play overlapping roles in sporulation. Interestingly, increased expression of the syntaxin Psy1p rescues the sporulation defect of sid2-250 slk1Δ. Thus, it is likely that Slk1p and Sid2p play a role in forespore membrane assembly by facilitating recruitment of components of the secretory apparatus, such as Psy1p, to allow membrane expansion. These studies thereby provide a novel link between the SIN and vesicle trafficking during cytokinesis.

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