Anchorage of Plant RanGAP to the Nuclear Envelope Involves Novel Nuclear-Pore-Associated Proteins

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.

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In Vivo Dynamics of Drosophila Nuclear Envelope Components

Molecular Biology of the Cell ◽

10.1091/mbc.e07-11-1162 ◽

2008 ◽

Vol 19 (9) ◽

pp. 3652-3666 ◽

Cited By ~ 76

Author(s):

Katerina R. Katsani ◽

Roger E. Karess ◽

Nathalie Dostatni ◽

Valérie Doye

Keyword(s):

Nuclear Envelope ◽

Mammalian Cells ◽

Nuclear Pore ◽

Nuclear Pore Complexes ◽

Checkpoint Proteins ◽

Early Anaphase ◽

Associated Proteins ◽

Pore Complexes ◽

Drosophila Cells

Nuclear pore complexes (NPCs) are multisubunit protein entities embedded into the nuclear envelope (NE). Here, we examine the in vivo dynamics of the essential Drosophila nucleoporin Nup107 and several other NE-associated proteins during NE and NPCs disassembly and reassembly that take place within each mitosis. During both the rapid mitosis of syncytial embryos and the more conventional mitosis of larval neuroblasts, Nup107 is gradually released from the NE, but it remains partially confined to the nuclear (spindle) region up to late prometaphase, in contrast to nucleoporins detected by wheat germ agglutinin and lamins. We provide evidence that in all Drosophila cells, a structure derived from the NE persists throughout metaphase and early anaphase. Finally, we examined the dynamics of the spindle checkpoint proteins Mad2 and Mad1. During mitotic exit, Mad2 and Mad1 are actively imported back from the cytoplasm into the nucleus after the NE and NPCs have reformed, but they reassociate with the NE only later in G1, concomitantly with the recruitment of the basket nucleoporin Mtor (the Drosophila orthologue of vertebrate Tpr). Surprisingly, Drosophila Nup107 shows no evidence of localization to kinetochores, despite the demonstrated importance of this association in mammalian cells.

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Nuclear Envelope and Nuclear Pore Complex Dynamjcs in vitro, Visualised by FEISEM

Microscopy and Microanalysis ◽

10.1017/s1431927600015518 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 438-439

Author(s):

T.D. Allen ◽

L.A. Cotter ◽

J.M. Cronshaw ◽

K.L. Wilson ◽

M.W. Goldberg

Keyword(s):

Cell Division ◽

Nuclear Envelope ◽

Nuclear Pore ◽

Cytoplasmic Extract ◽

Associated Proteins ◽

Chromosome Separation ◽

Specific Proteins ◽

Xenopus Egg ◽

Normal Cell Cycle

As the defining structure in eukaryote cells, the nuclear envelope is completely dismantled and reformed within an hour or so at each cell division (open mitosis). In yeast and some insect tissues, closed mitosis occurs, in which the nuclear envelope is maintained largely intact throughout chromosome separation. Use of cell free systems has allows us access to the mechanisms of cell division and NE dynamics in vitro by FEISEM (Field Emission In Lens Scanning Electron Microscopy. We have used demembranated Xenopus sperm heads as a source of DNA, which is incubated in an extract of Xenopus egg cytoplasm, where it becomes assembled into a normal nucleus with functional nuclear envelope (1-4). DNA replication proceeds under normal cell cycle controls, followed by an in vitro mitosis in suitable conditions. The cytoplasmic extract can be separated into membrane and soluble fractions that can be supplemented with, or depleted of, specific proteins. Inhibitors and other effectors can be .added to modulate both assembly and transport (5). Using the lectin WGA we have depleted Xenopus cytoplasmic extract of the major nucleoporins, CAN, Nup 98 and p62 and their associated proteins, whose removal effectively inhibits three aspects of nuclear formation, namely NPC formation, nuclear growth, and the reorganisation of the DNA in the depleted nuclei. Adding back these eluted nucleoporins restores normality with respect to nuclear growth, DNA reorganisation and NPC assembly. Current work involves purification of complexes containing these proteins by HPLC to allow add back of the complexes singly and in combination, to characterise their individual roles in NPC assembly, structure and transport (Figures 1,2,3).

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Targeting proteins to the plant nuclear envelope

Biochemical Society Transactions ◽

10.1042/bst0380733 ◽

2010 ◽

Vol 38 (3) ◽

pp. 733-740 ◽

Cited By ~ 21

Author(s):

Iris Meier ◽

Xiao Zhou ◽

Jelena Brkljacić ◽

Annkatrin Rose ◽

Qiao Zhao ◽

...

Keyword(s):

Nuclear Envelope ◽

Protein Interactions ◽

Transmembrane Domain ◽

Stress Protein ◽

Coiled Coil ◽

Land Plant ◽

Nuclear Pore ◽

Root Cells ◽

Interacting Protein ◽

Associated Proteins

The nuclear envelope and the nuclear pore are important structures that both separate and selectively connect the nucleoplasm and the cytoplasm. The requirements for specific targeting of proteins to the plant nuclear envelope and nuclear pore are poorly understood. How are transmembrane-domain proteins sorted to the nuclear envelope and nuclear pore membranes? What protein–protein interactions are involved in associating other proteins to the nuclear pore? Are there plant-specific aspects to these processes? We are using the case of the nuclear pore-associated Ran-cycle component RanGAP (Ran GTPase-activating protein) to address these fundamental questions. Plant RanGAP is targeted to the nuclear pore by a plant-specific mechanism involving two families of nuclear pore-associated proteins [WIP (WPP-domain-interacting protein) and WIT (WPP-domain-interacting tail-anchored protein)] not found outside the land plant lineage. One protein family (WIP or WIT) is sufficient for RanGAP targeting in differentiated root cells, whereas both families are necessary in meristematic cells. A C-terminal predicted transmembrane domain is sufficient for targeting WIP proteins to the nuclear envelope. Nuclear-envelope targeting of WIT proteins requires a coiled-coil domain and is facilitated by HSC70 (heat-shock cognate 70 stress protein) chaperones and a class of plant-specific proteins resembling the RanGAP-targeting domain (WPP proteins). Taken together, this sheds the first light on the requirements and interdependences of nuclear envelope and nuclear pore targeting in land plants.

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Nuclear Envelope Dynamics During Mitosis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103188 ◽

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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Faculty Opinions recommendation of The integral membrane nucleoporin pom121 functionally links nuclear pore complex assembly and nuclear envelope formation.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1023280.285732 ◽

2005 ◽

Author(s):

Mary Dasso

Keyword(s):

Nuclear Envelope ◽

Nuclear Pore Complex ◽

Nuclear Pore ◽

Complex Assembly ◽

Nuclear Envelope Formation

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The polymerization of actin: II. how nonfilamentous actin becomes nonrandomly distributed in sperm: evidence for the association of this actin with membranes

The Journal of Cell Biology ◽

10.1083/jcb.69.1.51 ◽

1976 ◽

Vol 69 (1) ◽

pp. 51-72 ◽

Cited By ~ 67

Author(s):

LG Tilney

Keyword(s):

Plasma Membrane ◽

Nuclear Envelope ◽

Thin Section ◽

Actin Filaments ◽

Early Stage ◽

Mature Sperm ◽

Vacuole Membrane ◽

Other Substances ◽

Associated Proteins ◽

Basal Half

At an early stage in spermiogenesis the acrosomal vacuole and other organelles including ribosomes are located at the basal end of the cell. From here actin must be transported to its future location at the anterior end of the cell. At no stage in the accumulation of actin in the periacrosomal region is the actin sequestered in a membrane-bounded compartment such as a vacuole or vesicle. Since filaments are not present in the periacrosomal region during the accumulation of the actin even though the fixation of these cells is sufficiently good to distinguish actin filaments in thin section, the actin must accumulate in the nonfilamentous state. The membranes in the periacrosomal region, specifically a portion of the nuclear envelope and the basal half of the acrosomal vacuole membrane, become specialized morphologically in advance of the accumulation of actin in this region. My working hypothesis is that the actin in combination with other substances binds to these specialized membranes and to itself and thus can accumulate in the periacrosmoal region by being trapped on these specialized membranes. Diffusion would then be sufficient to move these substances to this region. In support of this hypothesis are experiments in which I treated mature sperm with detergents, glycols, and hypotonic media, which solubilize or lift away the plasma membrane. The actin and its associated proteins remain attached to these specialized membranes. Thus actin can be nonrandomly distributed in cells in a nonfilamentous state presumably by its association with specialized membranes.

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Regulation and coordination of nuclear envelope and nuclear pore complex assembly

Nucleus ◽

10.4161/nucl.23796 ◽

2013 ◽

Vol 4 (2) ◽

pp. 105-114 ◽

Cited By ~ 15

Author(s):

Michaela Clever ◽

Yasuhiro Mimura ◽

Tomoko Funakoshi ◽

Naoko Imamoto

Keyword(s):

Nuclear Envelope ◽

Nuclear Pore Complex ◽

Nuclear Pore ◽

Complex Assembly

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Correlation between structure and mass distribution of the nuclear pore complex and of distinct pore complex components.

The Journal of Cell Biology ◽

10.1083/jcb.110.4.883 ◽

1990 ◽

Vol 110 (4) ◽

pp. 883-894 ◽

Cited By ~ 310

Author(s):

R Reichelt ◽

A Holzenburg ◽

E L Buhle ◽

M Jarnik ◽

A Engel ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Nuclear Envelope ◽

Three Dimensional ◽

Structural Features ◽

Nuclear Pore ◽

Xenopus Laevis Oocyte ◽

Three Dimensional Model ◽

Transmission Electron ◽

Freeze Dried

Nuclear pore complexes (NPCs) prepared from Xenopus laevis oocyte nuclear envelopes were studied in "intact" form (i.e., unexposed to detergent) and after detergent treatment by a combination of conventional transmission electron microscopy (CTEM) and quantitative scanning transmission electron microscopy (STEM). In correlation-averaged CTEM pictures of negatively stained intact NPCs and of distinct NPC components (i.e., "rings," "spoke" complexes, and "plug-spoke" complexes), several fine structural features arranged with octagonal symmetry about a central axis could reproducibly be identified. STEM micrographs of unstained/freeze-dried intact NPCs as well as of their components yielded comparable but less distinct features. Mass determination by STEM revealed the following molecular masses: intact NPC with plug, 124 +/- 11 MD; intact NPC without plug, 112 +/- 11 MD; heavy ring, 32 +/- 5 MD; light ring, 21 +/- 4 MD; plug-spoke complex, 66 +/- 8 MD; and spoke complex, 52 +/- 3 MD. Based on these combined CTEM and STEM data, a three-dimensional model of the NPC exhibiting eightfold centrosymmetry about an axis perpendicular to the plane of the nuclear envelope but asymmetric along this axis is proposed. This structural polarity of the NPC across the nuclear envelope is in accord with its well-documented functional polarity facilitating mediated nucleocytoplasmic exchange of molecules and particles.

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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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