scholarly journals Defects in nuclear pore assembly lead to activation of an Aurora B–mediated abscission checkpoint

2010 ◽  
Vol 191 (5) ◽  
pp. 923-931 ◽  
Author(s):  
Douglas R. Mackay ◽  
Masaki Makise ◽  
Katharine S. Ullman
Keyword(s):  
Small Interfering Rna ◽  
Nuclear Pore ◽  
Aurora B ◽  
Nuclear Pore Complexes ◽  
Daughter Cells ◽  
Nuclear Environment ◽  
Genomic Regulation ◽  
Pore Complexes ◽  
Interfering Rna ◽  
Nuclear Pore Assembly

Correct assembly of nuclear pore complexes (NPCs), which directly and indirectly control nuclear environment and architecture, is vital to genomic regulation. We previously found that nucleoporin 153 (Nup153) is required for timely progression through late mitosis. In this study, we report that disruption of Nup153 function by either small interfering RNA–mediated depletion or expression of a dominant-interfering Nup153 fragment results in dramatic mistargeting of the pore basket components Tpr and Nup50 in midbody-stage cells. We find a concomitant appearance of aberrantly localized active Aurora B and an Aurora B–dependent delay in abscission. Depletion of Nup50 is also sufficient to increase the number of midbody-stage cells and, likewise, triggers distinctive mislocalization of Aurora B. Together, our results suggest that defects in nuclear pore assembly, and specifically the basket structure, at this time of the cell cycle activate an Aurora B–mediated abscission checkpoint, thereby ensuring that daughter cells are generated only when fully formed NPCs are present.

scholarly journals Nuclear Pore Complex Acetylation Regulates mRNA Export and Cell Cycle Commitment in Budding Yeast

2021 ◽  
Author(s):  
Mercè Gomar-Alba ◽  
Vasilisa Pozharskaia ◽  
Celia Schaal ◽  
Arun Kumar ◽  
Basile Jacquel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Nuclear Export ◽  
Mrna Export ◽  
Cell Types ◽  
Nuclear Pore ◽  
Specific Cell ◽  
Nuclear Pore Complexes ◽  
Daughter Cells ◽  
Associated Proteins ◽  
Pore Complexes

AbstractNuclear pore complexes (NPCs) mediate communication between the nucleus and the cytoplasm and regulate gene expression by interacting with transcription and mRNA export factors. Lysine acetyl-transferases (KATs) promote transcription through acetylation of chromatin-associated proteins. We find that Esa1, the KAT subunit of the yeast NuA4 complex, also acetylates the nuclear pore basket component Nup60 to promote mRNA export. Acetylation of Nup60 recruits mRNA export factors to the nuclear basket, including the scaffolding subunit of the Transcription and Export 2 (TREX-2) complex, Sac3. Esa1-dependent nuclear export of mRNAs promotes entry into S phase, and is inhibited by the Hos3 deacetylase in G1 daughter cells to restrain their premature commitment to a new cell division cycle. This mechanism also inhibits expression of the nutrient-regulated GAL1 gene specifically in daughter cells. These results reveal how acetylation contributes to the functional plasticity of NPCs in specific cell types, and demonstrate how the evolutionarily conserved NuA4 complex regulates gene expression dually at the level of transcription and mRNA export, by modifying the nucleoplasmic entrance to nuclear pores.

scholarly journals The transmission of nuclear pore complexes to daughter cells requires a cytoplasmic pool of Nsp1

2013 ◽  
Vol 203 (2) ◽  
pp. 215-232 ◽  
Author(s):  
Paolo Colombi ◽  
Brant M. Webster ◽  
Florian Fröhlich ◽  
C. Patrick Lusk
Keyword(s):  
De Novo ◽  
Selective Inhibition ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Protein Assemblies ◽  
Class V ◽  
Specific Loss ◽  
Daughter Cells ◽  
Mother And Daughter ◽  
Pore Complexes

Nuclear pore complexes (NPCs) are essential protein assemblies that span the nuclear envelope and establish nuclear–cytoplasmic compartmentalization. We have investigated mechanisms that control NPC number in mother and daughter cells during the asymmetric division of budding yeast. By simultaneously tracking existing NPCs and newly synthesized NPC protomers (nups) through anaphase, we uncovered a pool of the central channel nup Nsp1 that is actively targeted to the bud in association with endoplasmic reticulum. Bud targeting required an intact actin cytoskeleton and the class V myosin, Myo2. Selective inhibition of cytoplasmic Nsp1 or inactivation of Myo2 reduced the inheritance of NPCs in daughter cells, leading to a daughter-specific loss of viability. Our data are consistent with a model in which Nsp1 releases a barrier that otherwise prevents NPC passage through the bud neck. It further supports the finding that NPC inheritance, not de novo NPC assembly, is primarily responsible for controlling NPC number in daughter cells.

scholarly journals Importin β Regulates the Seeding of Chromatin with Initiation Sites for Nuclear Pore Assembly

2009 ◽  
Vol 20 (18) ◽  
pp. 4031-4042 ◽  
Author(s):  
Asaf Rotem ◽  
Rita Gruber ◽  
Hagai Shorer ◽  
Lihi Shaulov ◽  
Eugenia Klein ◽  
...  
Keyword(s):  
Initial Step ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
High Molecular Weight Complex ◽  
Assembly Pathway ◽  
Attachment Sites ◽  
Pore Complexes ◽  
Membrane Components ◽  
Nuclear Pore Assembly ◽  
Initial Seeding

The nuclear envelope of higher eukaryotic cells reforms at the exit from mitosis, in concert with the assembly of nuclear pore complexes (NPCs). The first step in postmitotic NPC assembly involves the “seeding” of chromatin with ELYS and the Nup107-160 complex. Subsequent steps in the assembly process are poorly understood and different mechanistic models have been proposed to explain the formation of the full supramolecular structure. Here, we show that the initial step of chromatin seeding is negatively regulated by importin β. Direct imaging of the chromatin attachment sites reveals single sites situated predominantly on the highest substructures of chromatin surface and lacking any sign of annular structures or oligomerized pre-NPCs. Surprisingly, the inhibition by importin β is only partially reversed by RanGTP. Importin β forms a high-molecular-weight complex with both ELYS and the Nup107-160 complex in cytosol. We suggest that initiation sites for NPC assembly contain single copies of chromatin-bound ELYS/Nup107-160 and that the lateral oligomerization of these subunits depends on the recruitment of membrane components. We predict that additional regulators, besides importin β and Ran, may be involved in coordinating the initial seeding of chromatin with subsequent steps in the NPC assembly pathway.

scholarly journals Inheritance of yeast nuclear pore complexes requires the Nsp1p subcomplex

2013 ◽  
Vol 203 (2) ◽  
pp. 187-196 ◽  
Author(s):  
Tadashi Makio ◽  
Diego L. Lapetina ◽  
Richard W. Wozniak
Keyword(s):  
Daughter Cell ◽  
Selection Process ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Yeast Saccharomyces Cerevisiae ◽  
Macromolecular Complexes ◽  
Daughter Cells ◽  
Bud Neck ◽  
Pore Complexes ◽  
Mother Nucleus

In the yeast Saccharomyces cerevisiae, organelles and macromolecular complexes are delivered from the mother to the emerging daughter during cell division, thereby ensuring progeny viability. Here, we have shown that during mitosis nuclear pore complexes (NPCs) in the mother nucleus are actively delivered through the bud neck and into the daughter cell concomitantly with the nuclear envelope. Furthermore, we show that NPC movement into the daughter cell requires members of an NPC subcomplex containing Nsp1p and its interacting partners. NPCs lacking these nucleoporins (Nups) were blocked from entry into the daughter by a putative barrier at the bud neck. This selection process could be observed within individual cells such that NPCs containing Nup82p (an Nsp1p-interacting Nup) were transferred to the daughter cells while functionally compromised NPCs lacking Nup82p were retained in the mother. This mechanism is proposed to facilitate the inheritance of functional NPCs by daughter cells.

scholarly journals Leukemia-associated RhoGEF (LARG) is a novel RhoGEF in cytokinesis and required for the proper completion of abscission

2013 ◽  
Vol 24 (18) ◽  
pp. 2785-2794 ◽  
Author(s):  
Matthew K. Martz ◽  
Elda Grabocka ◽  
Neil Beeharry ◽  
Timothy J. Yen ◽  
Philip B. Wedegaertner
Keyword(s):  
Small Interfering Rna ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Aurora B ◽  
Intercellular Bridge ◽  
Concerted Effort ◽  
Central Spindle ◽  
Daughter Cells ◽  
Spindle Poles ◽  
Interfering Rna

Proper completion of mitosis requires the concerted effort of multiple RhoGEFs. Here we show that leukemia-associated RhoGEF (LARG), a RhoA-specific RGS-RhoGEF, is required for abscission, the final stage of cytokinesis, in which the intercellular membrane is cleaved between daughter cells. LARG colocalizes with α-tubulin at the spindle poles before localizing to the central spindle. During cytokinesis, LARG is condensed in the midbody, where it colocalizes with RhoA. HeLa cells depleted of LARG display apoptosis during cytokinesis with unresolved intercellular bridges, and rescue experiments show that expression of small interfering RNA–resistant LARG prevents this apoptosis. Moreover, live cell imaging of LARG-depleted cells reveals greatly delayed fission kinetics in abscission in which a population of cells with persistent bridges undergoes apoptosis; however, the delayed fission kinetics is rescued by Aurora-B inhibition. The formation of a Flemming body and thinning of microtubules in the intercellular bridge of cells depleted of LARG is consistent with a defect in late cytokinesis, just before the abscission event. In contrast to studies of other RhoGEFs, particularly Ect2 and GEF-H1, LARG depletion does not result in cytokinetic furrow regression nor does it affect internal mitotic timing. These results show that LARG is a novel and temporally distinct RhoGEF required for completion of abscission.

scholarly journals Postmitotic nuclear pore assembly proceeds by radial dilation of small ER membrane openings

2017 ◽  
Author(s):  
Shotaro Otsuka ◽  
Anna M. Steyer ◽  
Martin Schorb ◽  
Jean-Karim Hériché ◽  
M. Julius Hossain ◽  
...  
Keyword(s):  
Time Course ◽  
Three Dimensional ◽  
Membrane Topology ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Ring Complex ◽  
Pore Complexes ◽  
Transport Channels ◽  
Membrane Sealing ◽  
Nuclear Pore Assembly

AbstractThe nuclear envelope has to be reformed after mitosis to create viable daughter cells with closed nuclei. How membrane sealing of DNA and assembly of nuclear pore complexes (NPCs) are achieved and coordinated is poorly understood. Here, we reconstructed nuclear membrane topology and structure of assembling NPCs in a correlative three dimensional electron microscopy time-course of dividing human cells. Our quantitative ultrastructural analysis shows that nuclear membranes form from highly fenestrated ER sheets, whose shrinking holes are stabilized and then dilated into NPCs during inner ring complex assembly, forming thousands of transport channels within minutes. This mechanism is fundamentally different from interphase NPC assembly and explains how mitotic cells can rapidly establish a closed nuclear compartment while making it transport-competent at the same time.

scholarly journals Transportin Regulates Major Mitotic Assembly Events: From Spindle to Nuclear Pore Assembly

2009 ◽  
Vol 20 (18) ◽  
pp. 4043-4058 ◽  
Author(s):  
Corine K. Lau ◽  
Valerie A. Delmar ◽  
Rene C. Chan ◽  
Quang Phung ◽  
Cyril Bernis ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Mitotic Chromosomes ◽  
Nuclear Assembly ◽  
Importin Beta ◽  
Egg Extracts ◽  
Multiple Cell ◽  
Pore Complexes ◽  
Nuclear Pore Assembly

Mitosis in higher eukaryotes is marked by the sequential assembly of two massive structures: the mitotic spindle and the nucleus. Nuclear assembly itself requires the precise formation of both nuclear membranes and nuclear pore complexes. Previously, importin alpha/beta and RanGTP were shown to act as dueling regulators to ensure that these assembly processes occur only in the vicinity of the mitotic chromosomes. We now find that the distantly related karyopherin, transportin, negatively regulates nuclear envelope fusion and nuclear pore assembly in Xenopus egg extracts. We show that transportin—and importin beta—initiate their regulation as early as the first known step of nuclear pore assembly: recruitment of the critical pore-targeting nucleoporin ELYS/MEL-28 to chromatin. Indeed, each karyopherin can interact directly with ELYS. We further define the nucleoporin subunit targets for transportin and importin beta and find them to be largely the same: ELYS, the Nup107/160 complex, Nup53, and the FG nucleoporins. Equally importantly, we find that transportin negatively regulates mitotic spindle assembly. These negative regulatory events are counteracted by RanGTP. We conclude that the interplay of the two negative regulators, transportin and importin beta, along with the positive regulator RanGTP, allows precise choreography of multiple cell cycle assembly events.

scholarly journals Formation of the postmitotic nuclear envelope from extended ER cisternae precedes nuclear pore assembly

2011 ◽  
Vol 194 (3) ◽  
pp. 425-440 ◽  
Author(s):  
Lei Lu ◽  
Mark S. Ladinsky ◽  
Tomas Kirchhausen
Keyword(s):  
Nuclear Envelope ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Current Model ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nuclear Envelope Formation ◽  
Pore Complexes ◽  
Nuclear Pore Assembly ◽  
A Current

During mitosis, the nuclear envelope merges with the endoplasmic reticulum (ER), and nuclear pore complexes are disassembled. In a current model for reassembly after mitosis, the nuclear envelope forms by a reshaping of ER tubules. For the assembly of pores, two major models have been proposed. In the insertion model, nuclear pore complexes are embedded in the nuclear envelope after their formation. In the prepore model, nucleoporins assemble on the chromatin as an intermediate nuclear pore complex before nuclear envelope formation. Using live-cell imaging and electron microscope tomography, we find that the mitotic assembly of the nuclear envelope primarily originates from ER cisternae. Moreover, the nuclear pore complexes assemble only on the already formed nuclear envelope. Indeed, all the chromatin-associated Nup107–160 complexes are in single units instead of assembled prepores. We therefore propose that the postmitotic nuclear envelope assembles directly from ER cisternae followed by membrane-dependent insertion of nuclear pore complexes.

Nuclear Envelope Dynamics During Mitosis

1988 ◽  
Vol 46 ◽  
pp. 224-225
Author(s):  
Brian Burke
Keyword(s):  
Nuclear Envelope ◽  
Membrane Vesicles ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Animal Cells ◽  
Interphase Chromosome ◽  
Lamin B ◽  
Chromosome Architecture ◽  
Complex Membrane ◽  
Pore Complexes

The nuclear envelope is a complex membrane structure that forms the boundary of the nuclear compartment in eukaryotes. It regulates the passage of macromolecules between the two compartments and may be important for organizing interphase chromosome architecture. In interphase animal cells it forms a remarkably stable structure consisting of a double membrane ouerlying a protein meshwork or lamina and penetrated by nuclear pore complexes. The latter form the channels for nucleocytoplasmic exchange of macromolecules, At the onset of mitosis, however, it rapidly disassembles, the membranes fragment to yield small vesicles and the lamina, which is composed of predominantly three polypeptides, lamins R, B and C (MW approx. 74, 68 and 65 kDa respectiuely), breaks down. Lamins B and C are dispersed as monomers throughout the mitotic cytoplasm, while lamin B remains associated with the nuclear membrane vesicles.

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