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 Synthesis, transport and incorporation into the nuclear envelope of A-type lamins and inner nuclear membrane proteins

2011 ◽  
Vol 39 (6) ◽  
pp. 1758-1763 ◽  
Author(s):  
Jose M. González ◽  
Vicente Andrés
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Complex Structure ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Inner Nuclear Membrane ◽  
Perinuclear Space ◽  
Interphase Cells ◽  
Pore Complexes

The mammalian NE (nuclear envelope), which separates the nucleus from the cytoplasm, is a complex structure composed of nuclear pore complexes, the outer and inner nuclear membranes, the perinuclear space and the nuclear lamina (A- and B-type lamins). The NE is completely disassembled and reassembled at each cell division. In the present paper, we review recent advances in the understanding of the mechanisms implicated in the transport of inner nuclear membrane and nuclear lamina proteins from the endoplasmic reticulum to the nucleus in interphase cells and mitosis, with special attention to A-type lamins.

scholarly journals Internuclear exchange of an inner nuclear membrane protein (p55) in heterokaryons: in vivo evidence for the interaction of p55 with the nuclear lamina.

1990 ◽  
Vol 111 (6) ◽  
pp. 2225-2234 ◽  
Author(s):  
L Powell ◽  
B Burke
Keyword(s):  
Nuclear Membrane ◽  
Lateral Diffusion ◽  
Nuclear Lamina ◽  
Membrane System ◽  
Mouse Cell ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Inner Nuclear Membrane ◽  
Pore Complexes

The movement between nuclei of an integral protein of the inner nuclear membrane has been studied in rat/mouse and rat/hamster heterokaryons. This protein, p55, was found to equilibrate between nuclei over a period of approximately 6 h in the absence of new protein synthesis. When rat/mouse heterokaryons were constructed using an undifferentiated murine embryonal carcinoma (P19), which lacks lamins A and C, no accumulation of p55 in the mouse cell nucleus was observed. However, P19 nuclei could be rendered competent to accumulate p55 by transfecting the parent cells with human lamin A before cell fusion, supporting the notion that p55 may interact with the nuclear lamina. Since p55 does not appear to be able to dissociate from the nuclear membrane, it is concluded that this exchange between nuclei does not occur in the aqueous phase and instead is probably membrane mediated. It is proposed that this protein may be free to move between the inner and outer nuclear membranes via the continuities at the nuclear pore complexes and that transfer between nuclei occurs via lateral diffusion through the peripheral ER, which appears to form a single continuous membrane system in these heterokaryons. One implication of these observations is that accumulation of at least some integral proteins in the inner nuclear membrane may be mediated by interactions with other nuclear components and may not require a single defined targeting sequence.

scholarly journals Motor-driven motility of fungal nuclear pores organizes chromosomes and fosters nucleocytoplasmic transport

2012 ◽  
Vol 198 (3) ◽  
pp. 343-355 ◽  
Author(s):  
Gero Steinberg ◽  
Martin Schuster ◽  
Ulrike Theisen ◽  
Sreedhar Kilaru ◽  
Andrew Forge ◽  
...  
Keyword(s):  
Nuclear Lamina ◽  
Ustilago Maydis ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nuclear Pores ◽  
Gfp Reporter ◽  
Import And Export ◽  
Reporter Proteins ◽  
Pore Complexes

Exchange between the nucleus and the cytoplasm is controlled by nuclear pore complexes (NPCs). In animals, NPCs are anchored by the nuclear lamina, which ensures their even distribution and proper organization of chromosomes. Fungi do not possess a lamina and how they arrange their chromosomes and NPCs is unknown. Here, we show that motor-driven motility of NPCs organizes the fungal nucleus. In Ustilago maydis, Aspergillus nidulans, and Saccharomyces cerevisiae fluorescently labeled NPCs showed ATP-dependent movements at ∼1.0 µm/s. In S. cerevisiae and U. maydis, NPC motility prevented NPCs from clustering. In budding yeast, NPC motility required F-actin, whereas in U. maydis, microtubules, kinesin-1, and dynein drove pore movements. In the latter, pore clustering resulted in chromatin organization defects and led to a significant reduction in both import and export of GFP reporter proteins. This suggests that fungi constantly rearrange their NPCs and corresponding chromosomes to ensure efficient nuclear transport and thereby overcome the need for a structural lamina.

Relationships at the nuclear envelope: lamins and nuclear pore complexes in animals and plants

2010 ◽  
Vol 38 (3) ◽  
pp. 829-831 ◽  
Author(s):  
Jindriska Fiserova ◽  
Martin W. Goldberg
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Periphery ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nucleocytoplasmic Trafficking ◽  
Animal Cells ◽  
Cellular Processes ◽  
Associated Proteins ◽  
Pore Complexes

The nuclear envelope comprises a distinct compartment at the nuclear periphery that provides a platform for communication between the nucleus and cytoplasm. Signal transfer can proceed by multiple means. Primarily, this is by nucleocytoplasmic trafficking facilitated by NPCs (nuclear pore complexes). Recently, it has been indicated that signals can be transmitted from the cytoskeleton to the intranuclear structures via interlinking transmembrane proteins. In animal cells, the nuclear lamina tightly underlies the inner nuclear membrane and thus represents the protein structure located at the furthest boundary of the nucleus. It enables communication between the nucleus and the cytoplasm via its interactions with chromatin-binding proteins, transmembrane and membrane-associated proteins. Of particular interest is the interaction of the nuclear lamina with NPCs. As both structures fulfil essential roles in close proximity at the nuclear periphery, their interactions have a large impact on cellular processes resulting in affects on tissue differentiation and development. The present review concentrates on the structural and functional lamina–NPC relationship in animal cells and its potential implications to plants.

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 The Role of Nucleoporin Elys in Nuclear Pore Complex Assembly and Regulation of Genome Architecture

2020 ◽  
Vol 21 (24) ◽  
pp. 9475
Author(s):  
Yuri Y. Shevelyov
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Genome Architecture ◽  
Nuclear Pore Complexes ◽  
Current State ◽  
Long Time ◽  
Pore Complexes

For a long time, the nuclear lamina was thought to be the sole scaffold for the attachment of chromosomes to the nuclear envelope (NE) in metazoans. However, accumulating evidence indicates that nuclear pore complexes (NPCs) comprised of nucleoporins (Nups) participate in this process as well. One of the Nups, Elys, initiates NPC reassembly at the end of mitosis. Elys directly binds the decondensing chromatin and interacts with the Nup107–160 subcomplex of NPCs, thus serving as a seeding point for the subsequent recruitment of other NPC subcomplexes and connecting chromatin with the re-forming NE. Recent studies also uncovered the important functions of Elys during interphase where it interacts with chromatin and affects its compactness. Therefore, Elys seems to be one of the key Nups regulating chromatin organization. This review summarizes the current state of our knowledge about the participation of Elys in the post-mitotic NPC reassembly as well as the role that Elys and other Nups play in the maintenance of genome architecture.

scholarly journals Synchronization of Interphase Events Depends neither on Mitosis nor on cdk1

2003 ◽  
Vol 14 (9) ◽  
pp. 3730-3740 ◽  
Author(s):  
Ayelet Laronne ◽  
Shay Rotkopf ◽  
Asaf Hellman ◽  
Yosef Gruenbaum ◽  
Andrew C.G. Porter ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Ubiquitin Ligase ◽  
Nuclear Membrane ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Polyploid Cells ◽  
Dividing Cells ◽  
Pore Complexes

Human HT2-19 cells with a conditional cdk1 mutation stop dividing upon cdk1 inactivation and undergo multiple rounds of endoreplication. We show herein that major cell cycle events remain synchronized in these endoreplicating cells. DNA replication alternates with gap phases and cell cycle-specific cyclin E expression is maintained. Centrosomes duplicate in synchrony with chromosome replication, giving rise to polyploid cells with multiple centrosomes. Centrosome migration, a typical prophase event, also takes place in endoreplicating cells. The timing of these events is unaffected by cdk1 inactivation compared with normally dividing cells. Nuclear lamina breakdown, in contrast, previously shown to be dependent on cdk1, does not take place in endoreplicating HT2-19 cells. Moreover, breakdown of all other major components of the nuclear lamina, like the inner nuclear membrane proteins and nuclear pore complexes, seems also to depend on cdk1. Interestingly, the APC/C ubiquitin ligase is activated in these endoreplicating cells by fzr but not by fzy. The oscillations of interphase events are thus independent of cdk1 and of mitosis but may depend on APC/Cfzr activity.

scholarly journals An ESCRT-LEM protein surveillance system is poised to directly monitor the nuclear envelope and nuclear transport system

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
David J Thaller ◽  
Matteo Allegretti ◽  
Sapan Borah ◽  
Paolo Ronchi ◽  
Martin Beck ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Surveillance System ◽  
Nuclear Transport ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nuclear Membranes ◽  
Disease Mechanisms ◽  
Pore Complexes ◽  
Membrane Sealing

The integrity of the nuclear membranes coupled to the selective barrier of nuclear pore complexes (NPCs) are essential for the segregation of nucleoplasm and cytoplasm. Mechanical membrane disruption or perturbation to NPC assembly triggers an ESCRT-dependent surveillance system that seals nuclear pores: how these pores are sensed and sealed is ill defined. Using a budding yeast model, we show that the ESCRT Chm7 and the integral inner nuclear membrane (INM) protein Heh1 are spatially segregated by nuclear transport, with Chm7 being actively exported by Xpo1/Crm1. Thus, the exposure of the INM triggers surveillance with Heh1 locally activating Chm7. Sites of Chm7 hyperactivation show fenestrated sheets at the INM and potential membrane delivery at sites of nuclear envelope herniation. Our data suggest that perturbation to the nuclear envelope barrier would lead to local nuclear membrane remodeling to promote membrane sealing. Our findings have implications for disease mechanisms linked to NPC assembly and nuclear envelope integrity.

Selective digestion of nuclear envelopes from Xenopus oocyte germinal vesicles: possible structural role for the nuclear lamina

1990 ◽  
Vol 97 (3) ◽  
pp. 571-580
Author(s):  
S. Whytock ◽  
R.D. Moir ◽  
M. Stewart
Keyword(s):  
Nuclear Envelope ◽  
Xenopus Oocyte ◽  
Structural Integrity ◽  
Marked Change ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Structural Role ◽  
Germinal Vesicles ◽  
Pore Complexes

We have used enzymic digestion as a structural probe to investigate components of the nuclear envelope of germinal vesicles from Xenopus oocytes. Previous studies have shown that these envelopes are composed of a double membrane in which nuclear pore complexes are embedded. The nuclear pore complexes are linked to a fibrous lamina that underlies the nucleoplasmic face of the envelope. The pores are also linked by pore-connecting fibrils that attach near their cytoplasmic face. Xenopus oocyte nuclear envelopes were remarkably resistant to extraction with salt solutions and, even after treatment with 1 M NaCl or 3 M MgCl2, pores, lamina and pore-connecting fibrils remained intact. However, mild proteolysis with trypsin selectively removed the lamina fibres from Triton-extracted nuclear envelopes to leave only the pore complexes and connecting fibrils. This observation confirmed that the pore-connecting fibrils were different from the lamina fibres and were probably constructed from different proteins. Trypsin digestion followed by Triton treatment resulted in the complete disintegration of the nuclear envelope, providing direct evidence for a structural role for the lamina in maintaining envelope integrity. Digestion with ribonuclease did not produce any marked change in the structure of Triton-extracted nuclear envelopes, indicating that probably neither the pore-connecting fibrils nor the cytoplasmic granules on the pore complexes contained a substantial proportion of RNA that was vital for their structural integrity.

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