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 SUN proteins facilitate the removal of membranes from chromatin during nuclear envelope breakdown

2014 ◽  
Vol 204 (7) ◽  
pp. 1099-1109 ◽  
Author(s):  
Yagmur Turgay ◽  
Lysie Champion ◽  
Csaba Balazs ◽  
Michael Held ◽  
Alberto Toso ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Dominant Negative ◽  
Mitotic Spindles ◽  
Mitotic Progression ◽  
Microtubule Depolymerization ◽  
Nuclear Envelope Breakdown ◽  
And Migration ◽  
Delayed Removal

SUN proteins reside in the inner nuclear membrane and form complexes with KASH proteins of the outer nuclear membrane that connect the nuclear envelope (NE) to the cytoskeleton. These complexes have well-established functions in nuclear anchorage and migration in interphase, but little is known about their involvement in mitotic processes. Our analysis demonstrates that simultaneous depletion of human SUN1 and SUN2 delayed removal of membranes from chromatin during NE breakdown (NEBD) and impaired the formation of prophase NE invaginations (PNEIs), similar to microtubule depolymerization or down-regulation of the dynein cofactors NudE/EL. In addition, overexpression of dominant-negative SUN and KASH constructs reduced the occurrence of PNEI, indicating a requirement for functional SUN–KASH complexes in NE remodeling. Codepletion of SUN1/2 slowed cell proliferation and resulted in an accumulation of morphologically defective and disoriented mitotic spindles. Quantification of mitotic timing revealed a delay between NEBD and chromatin separation, indicating a role of SUN proteins in bipolar spindle assembly and mitotic progression.

scholarly journals Drosophila dTBCE recruits tubulin around chromatin to promote mitotic spindle assembly

2020 ◽  
Author(s):  
Mathieu Métivier ◽  
Emmanuel Gallaud ◽  
Aude Pascal ◽  
Jean-Philippe Gagné ◽  
Guy G. Poirier ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore ◽  
Nuclear Space ◽  
Mitotic Spindles ◽  
Microtubule Nucleation ◽  
Nuclear Envelope Breakdown ◽  
Tubulin Binding ◽  
Mitotic Spindle Assembly ◽  
Spindle Microtubules ◽  
Biochemical Analyses

AbstractProper assembly of mitotic spindles requires microtubule nucleation at centrosomes but also around chromatin. In this study, we reveal a novel mechanism by which an enrichment of tubulin in the nuclear space following nuclear envelope breakdown promotes nucleation of spindle microtubules. This event mediated by the tubulin-specific chaperone dTBCE, depends on its tubulin binding CAP-Gly motif and is regulated by Ran. Live imaging, proteomic and biochemical analyses suggest that dTBCE is enriched in the nucleus at nuclear envelope breakdown and interacts with nuclear pore proteins and the Ran machinery to create an environment that facilitates subsequent tubulin enrichment. We propose that dTBCE-dependent increase in tubulin concentration in the nuclear space is an important mechanism for microtubule nucleation in organisms where compartmentalization prevents free diffusion of tubulin.

scholarly journals Reconstitution of nuclear protein transport with semi-intact yeast cells.

1993 ◽  
Vol 123 (4) ◽  
pp. 785-798 ◽  
Author(s):  
G Schlenstedt ◽  
E Hurt ◽  
V Doye ◽  
P A Silver
Keyword(s):  
Nuclear Envelope ◽  
Protein Transport ◽  
Protein Import ◽  
Nuclear Protein ◽  
Yeast Cells ◽  
Nuclear Pore ◽  
Nuclear Pore Protein ◽  
Nuclear Protein Import ◽  
Pore Protein

We have developed an in vitro nuclear protein import reaction from semi-intact yeast cells. The reaction uses cells that have been permeabilized by freeze-thaw after spheroplast formation. Electron microscopic analysis and antibody-binding experiments show that the nuclear envelope remains intact but the plasma membrane is perforated. In the presence of ATP and cytosol derived from yeast or mammalian cells, a protein containing the nuclear localization sequence (NLS) of SV40 large T-antigen is transported into the nucleus. Proteins with mutant NLSs are not imported. In the absence of cytosol, binding of NLS-containing proteins occurs at the nuclear envelope. N-ethylmaleimide treatment of the cytosol as well as antibodies to the nuclear pore protein Nsp1 inhibit import but not binding to the nuclear envelope. Yeast mutants defective in nuclear protein transport were tested in the in vitro import reaction. Semi-intact cells from temperature-sensitive nsp1 mutants failed to import but some binding to the nuclear envelope was observed. On the other hand, no binding and thus no import into nuclei was observed in semi-intact nsp49 cells which are mutated in another nuclear pore protein. Np13 mutants, which are defective for nuclear protein import in vivo, were also deficient in the binding step under the in vitro conditions. Thus, the transport defect in these mutants is at the level of the nucleus and the point at which nuclear transport is blocked can be defined.

scholarly journals Introgression of Drosophila simulans Nuclear Pore Protein 160 in Drosophila melanogaster Alone Does Not Cause Inviability but Does Cause Female Sterility

Genetics ◽  
2010 ◽  
Vol 186 (2) ◽  
pp. 669-676 ◽  
Author(s):  
Kyoichi Sawamura ◽  
Kazunori Maehara ◽  
Shotaro Mashino ◽  
Tatsuo Kagesawa ◽  
Miyuki Kajiwara ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Drosophila Simulans ◽  
Female Sterility ◽  
Nuclear Pore ◽  
Nuclear Pore Protein ◽  
Pore Protein

scholarly journals Partial cDNA sequence encoding a nuclear pore protein modified by O-linked N-acetylglucosamine.

1988 ◽  
Vol 85 (24) ◽  
pp. 9595-9599 ◽  
Author(s):  
M. D'Onofrio ◽  
C. M. Starr ◽  
M. K. Park ◽  
G. D. Holt ◽  
R. S. Haltiwanger ◽  
...  
Keyword(s):  
Cdna Sequence ◽  
Nuclear Pore ◽  
Nuclear Pore Protein ◽  
Partial Cdna Sequence ◽  
Partial Cdna ◽  
Sequence Encoding ◽  
Pore Protein

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.

Analysis of nuclear pore protein p62 glycosylation

Biochemistry ◽  
1995 ◽  
Vol 34 (5) ◽  
pp. 1686-1694 ◽  
Author(s):  
W. A. Lubas ◽  
M. Smith ◽  
C. M. Starr ◽  
J. A. Hanover
Keyword(s):  
Nuclear Pore ◽  
Nuclear Pore Protein ◽  
Pore Protein
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