Role of Ran GTPase in Nuclear Envelope Assembly

2002 ◽  
pp. 61-71
Author(s):  
Zhang Chuanmao ◽  
Paul R. Clarke
Keyword(s):  
Nuclear Envelope ◽  
Ran Gtpase ◽  
Nuclear Envelope Assembly

scholarly journals Ran GTPase Cycle and Importins α and β Are Essential for Spindle Formation and Nuclear Envelope Assembly in LivingCaenorhabditis elegans Embryos

2002 ◽  
Vol 13 (12) ◽  
pp. 4355-4370 ◽  
Author(s):  
Peter Askjaer ◽  
Vincent Galy ◽  
Eva Hannak ◽  
Iain W. Mattaj
Keyword(s):  
Nuclear Envelope ◽  
Cell Function ◽  
Small Gtpase ◽  
Spindle Formation ◽  
Ran Gtpase ◽  
Early Embryos ◽  
Nuclear Envelope Assembly ◽  
Importin Α ◽  
Gtpase Cycle

The small GTPase Ran has been found to play pivotal roles in several aspects of cell function. We have investigated the role of the Ran GTPase cycle in spindle formation and nuclear envelope assembly in dividing Caenorhabditis elegans embryos in real time. We found that Ran and its cofactors RanBP2, RanGAP, and RCC1 are all essential for reformation of the nuclear envelope after cell division. Reducing the expression of any of these components of the Ran GTPase cycle by RNAi leads to strong extranuclear clustering of integral nuclear envelope proteins and nucleoporins. Ran, RanBP2, and RanGAP are also required for building a mitotic spindle, whereas astral microtubules are normal in the absence of these proteins. RCC1(RNAi) embryos have similar abnormalities in the initial phase of spindle formation but eventually recover to form a bipolar spindle. Irregular chromatin structures and chromatin bridges due to spindle failure were frequently observed in embryos where the Ran cycle was perturbed. In addition, connection between the centrosomes and the male pronucleus, and thus centrosome positioning, depends upon the Ran cycle components. Finally, we have demonstrated that both IMA-2 and IMB-1, the homologues of vertebrate importin α and β, are essential for both spindle assembly and nuclear formation in early embryos.

scholarly journals Lamin activity is essential for nuclear envelope assembly in a Drosophila embryo cell-free extract.

1992 ◽  
Vol 119 (1) ◽  
pp. 17-25 ◽  
Author(s):  
N Ulitzur ◽  
A Harel ◽  
N Feinstein ◽  
Y Gruenbaum
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Membrane Vesicles ◽  
Embryo Cell ◽  
Drosophila Embryo ◽  
Sperm Chromatin ◽  
Naked Dna ◽  
Nuclear Envelope Assembly

The role of the Drosophila lamin protein in nuclear envelope assembly was studied using a Drosophila in vitro assembly system that reconstitutes nuclei from added sperm chromatin or naked DNA. Upon incubation of the embryonic assembly extract with anti-Drosophila lamin antibodies, the attachment of nuclear membrane vesicles to chromatin surface and nuclear envelope formation did not occur. Lamina assembly and nuclear membrane vesicles attachment to the chromatin were inhibited only when the activity of the 75-kD lamin isoform was inhibited in both soluble and membrane-vesicles fractions. Incubation of decondensed sperm chromatin with an extract that was depleted of nuclear membranes revealed the presence of lamin molecules on the chromatin periphery. In addition, high concentrations of bacterially expressed lamin molecules added to the extract, were able to associate with the chromatin periphery, and did not inhibit nuclear envelope assembly. After nuclear reconstitution, a fraction of the lamin pool was converted into the typical 74- and 76-kD isoforms. Together, these data strongly support an essential role of the lamina in nuclear envelope assembly.

Role of phospholipase C in nuclear envelope assembly

2009 ◽  
Vol 4 (1) ◽  
pp. 103-112 ◽  
Author(s):  
Richard D Byrne ◽  
Dominic L Poccia ◽  
Banafshé Larijani
Keyword(s):  
Nuclear Envelope ◽  
Phospholipase C ◽  
Nuclear Envelope Assembly

The Ran GTPase as a marker of chromosome position in spindle formation and nuclear envelope assembly

2002 ◽  
Vol 4 (7) ◽  
pp. E177-E184 ◽  
Author(s):  
Martin Hetzer ◽  
Oliver J. Gruss ◽  
Iain W. Mattaj
Keyword(s):  
Nuclear Envelope ◽  
Spindle Formation ◽  
Ran Gtpase ◽  
Chromosome Position ◽  
Nuclear Envelope Assembly

scholarly journals SUMO-1 targets RanGAP1 to kinetochores and mitotic spindles

2002 ◽  
Vol 156 (4) ◽  
pp. 595-602 ◽  
Author(s):  
Jomon Joseph ◽  
Shyh-Han Tan ◽  
Tatiana S. Karpova ◽  
James G. McNally ◽  
Mary Dasso
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore ◽  
Mitotic Spindles ◽  
Nuclear Pore Protein ◽  
Nuclear Envelope Breakdown ◽  
Spatial Regulation ◽  
Nuclear Envelope Assembly ◽  
First Time ◽  
Pore Protein

RanGAP1 was the first documented substrate for conjugation with the ubiquitin-like protein SUMO-1. However, the functional significance of this conjugation has not been fully clarified. We sought to examine RanGAP1 behavior during mitosis. We found that RanGAP1 associates with mitotic spindles and that it is particularly concentrated at foci near kinetochores. Association with kinetochores appeared soon after nuclear envelope breakdown and persisted until late anaphase, but it was lost coincident with nuclear envelope assembly in telophase. A mutant RanGAP1 protein lacking the capacity to be conjugated to SUMO-1 no longer associated with spindles, indicating that conjugation was essential for RanGAP1's mitotic localization. RanBP2, a nuclear pore protein that binds SUMO-1–conjugated RanGAP1 during interphase, colocalized with RanGAP1 on spindles, suggesting that a complex between these two proteins may be involved in mitotic targeting of RanGAP1. This report shows for the first time that SUMO-1 conjugation is required for mitotic localization of RanGAP1, and suggests that a major role of SUMO-1 conjugation to RanGAP1 may be the spatial regulation of the Ran pathway during mitosis.

scholarly journals Transmembrane proteins are not required for early stages of nuclear envelope assembly

2006 ◽  
Vol 400 (3) ◽  
pp. 393-400 ◽  
Author(s):  
Corinne Ramos ◽  
Elvira R. Rafikova ◽  
Kamran Melikov ◽  
Leonid V. Chernomordik
Keyword(s):  
Nuclear Envelope ◽  
Transmembrane Proteins ◽  
Membrane Vesicles ◽  
Ran Gtpase ◽  
Free System ◽  
Nuclear Envelope Assembly ◽  
Cytosolic Extract ◽  
A Cell ◽  
Integral Proteins ◽  
Membrane Fusion Proteins

All identified membrane fusion proteins are transmembrane proteins. In the present study, we explored the post-mitotic reassembly of the NE (nuclear envelope). The proteins that drive membrane rearrangements in NE assembly remain unknown. To determine whether transmembrane proteins are prerequisite components of this fusion machinery, we have focused on nuclear reconstitution in a cell-free system. Mixing of soluble interphase cytosolic extract and MV (membrane vesicles) from amphibian eggs with chromatin results in the formation of functional nuclei. We replaced MV and cytosol with protein-free phosphatidylcholine LS (liposomes) that were pre-incubated with interphase cytosol. While later stages of NE assembly yielding functional nucleus did not proceed without integral proteins of MV, LS-associated cytosolic proteins were sufficient to reconstitute membrane targeting to the chromatin and GTP-dependent lipid mixing. Binding involved LS-associated A-type lamin, and fusion involved Ran GTPase. Thus in contrast with post-fusion stages, fusion initiation in NE assembly, like membrane remodelling in budding and fission, does not require transmembrane proteins.

scholarly journals Role of Importin-β in the Control of Nuclear Envelope Assembly by Ran

2002 ◽  
Vol 12 (6) ◽  
pp. 498-502 ◽  
Author(s):  
Chuanmao Zhang ◽  
James R.A. Hutchins ◽  
Petra Mühlhäusser ◽  
Ulrike Kutay ◽  
Paul R. Clarke
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Envelope Assembly
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