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

2017 ◽  
Vol 114 (11) ◽  
pp. E2166-E2175 ◽  
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.

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

2016 ◽  
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

AbstractESCRT-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. InS. 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 disc periphery during this window of cell division, and that CHMP7 can bind directly to the C-terminal domain of LEM2in 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.

NNF1 is an essential yeast gene required for proper spindle orientation, nucleolar and nuclear envelope structure and mRNA export

1997 ◽  
Vol 110 (14) ◽  
pp. 1615-1624 ◽  
Author(s):  
X. Shan ◽  
Z. Xue ◽  
G. Euskirchen ◽  
T. Melese
Keyword(s):  
Nuclear Envelope ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Receptor Protein ◽  
Nuclear Localization Sequence ◽  
Nuclear Pore ◽  
Temperature Sensitive ◽  
Nuclear Pore Complexes ◽  
Yeast Gene ◽  
Localization Sequence

The nuclear envelope is central to nuclear structure and function. It plays a role in maintaining nuclear shape, allowing the exchange of macromolecules between the nucleus and the cytoplasm (via the nuclear pore complexes), and providing attachment sites for microtubules during chromosome segregation and nuclear migration (via the spindle pole body). We have isolated an essential yeast gene, NNF1 that is required for a number of nuclear functions. Cells depleted of Nnf1p or containing a temperature-sensitive nnf1 mutation have elongated microtubules and become bi- and multinucleate. They also have a fragmented nucleolous and accumulate poly(A)+ RNA inside the nucleus. A similar constellation of phenotypes has been reported in cells carrying mutations in a number of nuclear pore proteins, components of the Ran GTPase cycle, and the nuclear localization sequence receptor protein. Our results suggest that Nnf1p plays a role in a number of nuclear functions.

scholarly journals Membrane proteins Bqt3 and -4 anchor telomeres to the nuclear envelope to ensure chromosomal bouquet formation

2009 ◽  
Vol 187 (3) ◽  
pp. 413-427 ◽  
Author(s):  
Yuji Chikashige ◽  
Miho Yamane ◽  
Kasumi Okamasa ◽  
Chihiro Tsutsumi ◽  
Tomoko Kojidani ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Fission Yeast ◽  
Nuclear Membrane ◽  
Meiotic Prophase ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Null Mutant ◽  
Vegetative Cells ◽  
Nuclear Membranes ◽  
Pole Body

In many organisms, telomeres cluster to form a bouquet arrangement of chromosomes during meiotic prophase. Previously, we reported that two meiotic proteins, Bqt1 and -2, are required for tethering telomeres to the spindle pole body (SPB) during meiotic prophase in fission yeast. This study has further identified two novel, ubiquitously expressed inner nuclear membrane (INM) proteins, Bqt3 and -4, which are required for bouquet formation. We found that in the absence of Bqt4, telomeres failed to associate with the nuclear membranes in vegetative cells and consequently failed to cluster to the SPB in meiotic prophase. In the absence of Bqt3, Bqt4 protein was degraded during meiosis, leading to a phenotype similar to that of the bqt4-null mutant. Collectively, these results show that Bqt4 anchors telomeres to the INM and that Bqt3 protects Bqt4 from protein degradation. Interestingly, the functional integrity of telomeres is maintained even when they are separated from the nuclear envelope in vegetative cells.

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

2009 ◽  
Vol 20 (2) ◽  
pp. 616-630 ◽  
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.

scholarly journals Nuclear envelope organization in Dictyostelium discoideum

2019 ◽  
Vol 63 (8-9-10) ◽  
pp. 509-519 ◽  
Author(s):  
Petros Batsios ◽  
Ralph Gräf ◽  
Michael P. Koonce ◽  
Denis A. Larochelle ◽  
Irene Meyer
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Nuclear Lamina ◽  
Major Constituent ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Linc Complex ◽  
Family Protein ◽  
Import And Export ◽  
Pore Complexes

The nuclear envelope consists of the outer and the inner nuclear membrane, the nuclear lamina and the nuclear pore complexes, which regulate nuclear import and export. The major constituent of the nuclear lamina of Dictyostelium is the lamin NE81. It can form filaments like B-type lamins and it interacts with Sun1, as well as with the LEM/HeH-family protein Src1. Sun1 and Src1 are nuclear envelope transmembrane proteins involved in the centrosome-nucleus connection and nuclear envelope stability at the nucleolar regions, respectively. In conjunction with a KASH-domain protein, Sun1 usually forms a so-called LINC complex. Two proteins with functions reminiscent of KASH-domain proteins at the outer nuclear membrane of Dictyostelium are known; interaptin which serves as an actin connector and the kinesin Kif9 which plays a role in the microtubule-centrosome connector. However, both of these lack the conserved KASH-domain. The link of the centrosome to the nuclear envelope is essential for the insertion of the centrosome into the nuclear envelope and the appropriate spindle formation. Moreover, centrosome insertion is involved in permeabilization of the mitotic nucleus, which ensures access of tubulin dimers and spindle assembly factors. Our recent progress in identifying key molecular players at the nuclear envelope of Dictyostelium promises further insights into the mechanisms of nuclear envelope dynamics.

scholarly journals The NIMA Kinase Is Required To Execute Stage-Specific Mitotic Functions after Initiation of Mitosis

2013 ◽  
Vol 13 (1) ◽  
pp. 99-109 ◽  
Author(s):  
Meera Govindaraghavan ◽  
Alisha A. Lad ◽  
Stephen A. Osmani
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Cycle Phase ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Content Type ◽  
Mitotic Entry ◽  
Spindle Pole Bodies ◽  
Pore Complexes

ABSTRACTThe G2-M transition inAspergillus nidulansrequires the NIMA kinase, the founding member of the Nek kinase family. Inactivation of NIMA results in a late G2arrest, while overexpression of NIMA is sufficient to promote mitotic events independently of cell cycle phase. Endogenously tagged NIMA-GFP has dynamic mitotic localizations appearing first at the spindle pole body and then at nuclear pore complexes before transitioning to within nuclei and the mitotic spindle and back at the spindle pole bodies at mitotic exit, suggesting that it functions sequentially at these locations. Since NIMA is indispensable for mitotic entry, it has been difficult to determine the requirement of NIMA for subaspects of mitosis. We show here that when NIMA is partially inactivated, although mitosis can be initiated, a proportion of cells fail to successfully generate two daughter nuclei. We further define the mitotic defects to show that normal NIMA function is required for the formation of a bipolar spindle, nuclear pore complex disassembly, completion of chromatin segregation, and the normal structural rearrangements of the nuclear envelope required to generate two nuclei from one. In the remaining population of cells that enter mitosis with inadequate NIMA, two daughter nuclei are generated in a manner dependent on the spindle assembly checkpoint, indicating highly penetrant defects in mitotic progression without sufficient NIMA activity. This study shows that NIMA is required not only for mitotic entry but also sequentially for successful completion of stage-specific mitotic events.

scholarly journals Expression of TorsinA in a heterologous yeast system reveals interactions with conserved lumenal domains of LINC and nuclear pore complexes

2018 ◽  
Author(s):  
Madeleine Chalfant ◽  
Karl W. Barber ◽  
Sapan Borah ◽  
David Thaller ◽  
C. Patrick Lusk
Keyword(s):  
Nuclear Envelope ◽  
Genetic Interaction ◽  
Spindle Pole ◽  
Nuclear Pore ◽  
Physical Interaction ◽  
Nuclear Pore Complexes ◽  
Gene Encoding ◽  
Aaa Atpase ◽  
Dyt1 Dystonia ◽  
Pore Complexes

ABSTRACTDYT1 dystonia is caused by an in-frame deletion of a glutamic acid codon in the gene encoding the AAA+ ATPase TorsinA. TorsinA localizes within the lumen of the nuclear envelope/ER and binds to a membrane-spanning co-factor, LAP1 or LULL1, to form an ATPase; the substrate(s) of TorsinA remain ill defined. Here we use budding yeast, which lack Torsins, to interrogate TorsinA function. We show that TorsinA accumulates at nuclear envelope embedded spindle pole bodies (SPBs) in a way that requires its oligomerization and the conserved SUN-domain protein, Mps3. TorsinA is released from SPBs upon expression of LAP1 and stabilized by LAP1 mutants incapable of stimulating TorsinA ATPase activity, suggesting the recapitulation of a TorsinA-substrate cycle. While the expression of TorsinA or TorsinA-ΔE impacts the fitness of strains expressing mps3 alleles, a genetic interaction with a conserved component of the nuclear pore complex, Pom152, is specific for TorsinA. This specificity is mirrored by a physical interaction between Pom152 and TorsinA, but not TorsinA-ΔE. These data suggest that TorsinA-nucleoporin interactions would be abrogated by TorsinA-ΔE, providing new experimental avenues to interrogate the molecular basis behind nuclear envelope herniations seen in cells lacking TorsinA function.

Sequential recruitment of NPC proteins to the nuclear periphery at the end of mitosis

1999 ◽  
Vol 112 (13) ◽  
pp. 2253-2264 ◽  
Author(s):  
K. Bodoor ◽  
S. Shaikh ◽  
D. Salina ◽  
W.H. Raharjo ◽  
R. Bastos ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Time Course ◽  
Nuclear Periphery ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Confocal Immunofluorescence Microscopy ◽  
Pore Complexes ◽  
Nuclear Membrane Protein

Nuclear pore complexes (NPCs) are extremely elaborate structures that mediate the bidirectional movement of macromolecules between the nucleus and cytoplasm. With a mass of about 125 MDa, NPCs are thought to be composed of 50 or more distinct protein subunits, each present in multiple copies. During mitosis in higher cells the nuclear envelope is disassembled and its components, including NPC subunits, are dispersed throughout the mitotic cytoplasm. At the end of mitosis, all of these components are reutilized. Using both conventional and digital confocal immunofluorescence microscopy we have been able to define a time course of post-mitotic assembly for a group of NPC components (CAN/Nup214, Nup153, POM121, p62 and Tpr) relative to the integral nuclear membrane protein LAP2 and the NPC membrane glycoprotein gp210. Nup153, a component of the nuclear basket, associates with chromatin towards the end of anaphase, in parallel with the inner nuclear membrane protein, LAP2. However, immunogold labeling suggests that the initial Nup153 chromatin association is membrane-independent. Assembly of the remaining proteins follows that of the nuclear membranes and occurs in the sequence POM121, p62, CAN/Nup214 and gp210/Tpr. Since p62 remains as a complex with three other NPC proteins (p58, 54, 45) during mitosis and CAN/Nup214 maintains a similar interaction with its partner, Nup84, the relative timing of assembly of these additional four proteins may also be inferred. These observations suggest that there is a sequential association of NPC proteins with chromosomes during nuclear envelope reformation and the recruitment of at least eight of these precedes that of gp210. These findings support a model in which it is POM121 rather than gp210 that defines initial membrane-associated NPC assembly intermediates.

Reticulon-like REEP4 at the inner nuclear membrane promotes nuclear pore complex formation

2021 ◽  
Vol 221 (2) ◽  
Author(s):  
Banafsheh Golchoubian ◽  
Andreas Brunner ◽  
Helena Bragulat-Teixidor ◽  
Annett Neuner ◽  
Busra A. Akarlar ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Inner Nuclear Membrane ◽  
Pore Complexes ◽  
Late Stages ◽  
Protein Complex Assembly

Nuclear pore complexes (NPCs) are channels within the nuclear envelope that mediate nucleocytoplasmic transport. NPCs form within the closed nuclear envelope during interphase or assemble concomitantly with nuclear envelope reformation in late stages of mitosis. Both interphase and mitotic NPC biogenesis require coordination of protein complex assembly and membrane deformation. During early stages of mitotic NPC assembly, a seed for new NPCs is established on chromatin, yet the factors connecting the NPC seed to the membrane of the forming nuclear envelope are unknown. Here, we report that the reticulon homology domain protein REEP4 not only localizes to high-curvature membrane of the cytoplasmic endoplasmic reticulum but is also recruited to the inner nuclear membrane by the NPC biogenesis factor ELYS. This ELYS-recruited pool of REEP4 promotes NPC assembly and appears to be particularly important for NPC formation during mitosis. These findings suggest a role for REEP4 in coordinating nuclear envelope reformation with mitotic NPC biogenesis.

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

2014 ◽  
Vol 25 (19) ◽  
pp. 2970-2983 ◽  
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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