scholarly journals The mechanism of spindle assembly

2004 ◽  
Vol 166 (7) ◽  
pp. 949-955 ◽  
Author(s):  
Oliver J. Gruss ◽  
Isabelle Vernos
Keyword(s):  
Cell Division ◽  
Recent Work ◽  
Current Knowledge ◽  
Spindle Assembly ◽  
Small Gtpase ◽  
Multiple Roles ◽  
Mitotic Chromosomes ◽  
Downstream Targets ◽  
Gtpase Ran

Recent work has provided new insights into the mechanism of spindle assembly. Growing evidence supports a model in which the small GTPase Ran plays a central role in this process. Here, we examine the evidence for the existence of a RanGTP gradient around mitotic chromosomes and some controversial data on the role that chromosomes play in spindle assembly. We review the current knowledge on the Ran downstream targets for spindle assembly and we focus on the multiple roles of TPX2, one of the targets of RanGTP during cell division.

scholarly journals Cell division screens and dynamin

2008 ◽  
Vol 36 (3) ◽  
pp. 431-435 ◽  
Author(s):  
Mary Kate Bonner ◽  
Ahna R. Skop
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Wound Repair ◽  
Current Knowledge ◽  
Multiple Roles ◽  
Actin Assembly ◽  
Dynamic Nature ◽  
Fundamental Process ◽  
Cell Diversity ◽  
Living Organisms

Cell division is the most fundamental process in the development of all living organisms. The generation of cell diversity throughout development, the multiplication of cells during wound repair and the maintenance of stem cells in several tissues and organs all rely on proper progress through cell division. Historically, biochemical studies of cell division proved to be difficult, since mitosis is a moving target. The rapid and dynamic nature of mitosis means necessary proteins often exist in multiple isoforms and some for only brief moments during a particular stage in the cell cycle. The advent of proteomics and the introduction of stage-specific inhibitors have enabled the field to identify numerous factors required at distinct steps in the cell cycle. One such factor identified in many of these screens was the highly conserved protein dynamin. Dynamin, long known for its role in endocytosis, is also necessary for co-ordinating actin assembly at membranes. Our knowledge of its precise cell cycle function and upstream/downstream targets, however, is unclear. Our review will describe current knowledge regarding the impacts of several cell division screens and the multiple roles that dynamin may play during mitosis.

Chromokinesins: localization-dependent functions and regulation during cell division

2011 ◽  
Vol 39 (5) ◽  
pp. 1154-1160 ◽  
Author(s):  
David Vanneste ◽  
Vanessa Ferreira ◽  
Isabelle Vernos
Keyword(s):  
Cell Division ◽  
Molecular Motors ◽  
Current Knowledge ◽  
Spindle Assembly ◽  
Dynamic Structure ◽  
Spindle Pole ◽  
Dependent Manner ◽  
Ki 67 ◽  
Balance Of Forces ◽  
Chromosome Movements

The bipolar spindle is a highly dynamic structure that assembles transiently around the chromosomes and provides the mechanical support and the forces required for chromosome segregation. Spindle assembly and chromosome movements rely on the regulation of microtubule dynamics and a fine balance of forces exerted by various molecular motors. Chromosomes are themselves central players in spindle assembly. They generate a RanGTP gradient that triggers microtubule nucleation and stabilization locally and they interact dynamically with the microtubules through motors targeted to the chromatin. We have previously identified and characterized two of these so-called chromokinesins: Xkid (kinesin 10) and Xklp1 (kinesin 4). More recently, we found that Hklp2/kif15 (kinesin 12) is targeted to the chromosomes through an interaction with Ki-67 in human cells and is therefore a novel chromokinesin. Hklp2 also associates with the microtubules specifically during mitosis, in a TPX2 (targeting protein for Xklp2)-dependent manner. We have shown that Hklp2 participates in spindle pole separation and in the maintenance of spindle bipolarity in metaphase. To better understand the function of Hklp2, we have performed a detailed domain analysis. Interestingly, from its positioning on the chromosome arms, Hklp2 seems to restrict spindle pole separation. In the present review, we summarize the current knowledge of the function and regulation of the different kinesins associated with chromosome arms during cell division, including Hklp2 as a novel member of this so-called chromokinesin family.

scholarly journals The Fission Yeast Nup107-120 Complex Functionally Interacts with the Small GTPase Ran/Spi1 and Is Required for mRNA Export, Nuclear Pore Distribution, and Proper Cell Division

2004 ◽  
Vol 24 (14) ◽  
pp. 6379-6392 ◽  
Author(s):  
Siau Wei Baï ◽  
Jacques Rouquette ◽  
Makoto Umeda ◽  
Wolfgang Faigle ◽  
Damarys Loew ◽  
...  
Keyword(s):  
Cell Division ◽  
Mrna Export ◽  
Small Gtpase ◽  
Pore Distribution ◽  
Open Reading Frames ◽  
Nuclear Pore ◽  
Restrictive Temperature ◽  
Functional Studies ◽  
Gtpase Ran

ABSTRACT We have characterized Schizosaccharomyces pombe open reading frames encoding potential orthologues of constituents of the evolutionarily conserved Saccharomyces cerevisiae Nup84 vertebrate Nup107-160 nuclear pore subcomplex, namely Nup133a, Nup133b, Nup120, Nup107, Nup85, and Seh1. In spite of rather weak sequence conservation, in vivo analyses demonstrated that these S. pombe proteins are localized at the nuclear envelope. Biochemical data confirmed the organization of these nucleoporins within conserved complexes. Although examination of the S. cerevisiae and S. pombe deletion mutants revealed different viability phenotypes, functional studies indicated that the involvement of this complex in nuclear pore distribution and mRNA export has been conserved between these highly divergent yeasts. Unexpectedly, microscopic analyses of some of the S. pombe mutants revealed cell division defects at the restrictive temperature (abnormal septa and mitotic spindles and chromosome missegregation) that were reminiscent of defects occurring in several S. pombe GTPase Ran (RanSp)/Spi1 cycle mutants. Furthermore, deletion of nup120 moderately altered the nuclear location of RanSp/Spi1, whereas overexpression of a nonfunctional RanSp/Spi1-GFP allele was specifically toxic in the Δnup120 and Δnup133b mutant strains, indicating a functional and genetic link between constituents of the S. pombe Nup107-120 complex and of the RanSp/Spi1 pathway.

scholarly journals Importin β Is a Mitotic Target of the Small GTPase Ran in Spindle Assembly

Cell ◽  
2001 ◽  
Vol 104 (1) ◽  
pp. 95-106 ◽  
Author(s):  
Maxence V Nachury ◽  
Thomas J Maresca ◽  
Wendy C Salmon ◽  
Clare M Waterman-Storer ◽  
Rebecca Heald ◽  
...  
Keyword(s):  
Spindle Assembly ◽  
Small Gtpase ◽  
Gtpase Ran

Ras induces NBT-II epithelial cell scattering through the coordinate activities of Rac and MAPK pathways

2002 ◽  
Vol 115 (12) ◽  
pp. 2591-2601 ◽  
Author(s):  
Natacha Edme ◽  
Julian Downward ◽  
Jean-Paul Thiery ◽  
Brigitte Boyer
Keyword(s):  
Cell Migration ◽  
Cell Motility ◽  
Mapk Pathway ◽  
Small Gtpase ◽  
Dominant Negative Mutant ◽  
Cell Periphery ◽  
Cell Dissociation ◽  
Downstream Targets ◽  
Cell Dispersion ◽  
Cell Scattering

Cell dissociation and cell migration are the two main components of epithelium-mesenchyme transitions (EMT). We previously demonstrated that Ras is required for the accomplishment of both of these processes during the EGF-induced EMT of the NBT-II rat carcinoma cell line in vitro. In this study,we examined the downstream targets of Ras that are responsible for the dissociation and motility of NBT-II cells. Overexpression of activated forms of c-Raf and MEK1 (a component of the mitogen-activated protein kinase pathway, MAPK) led to cell dissociation, as inferred by the loss of desmosomes from the cell periphery. By contrast, active PI3K, RalA and RalB did not induce desmosome breakdown. The MEK1 inhibitor PD098059 inhibited EGF- and Ras-induced cell dispersion, whereas the PI3K inhibitor LY294002 had no effect. Accordingly, among the partial loss-of-function mutants of Ras(RasV12) that were used to distinguish between downstream targets of Ras, we found that the Raf-specific Ras mutants RasV12S35 and RasV12E38 induced cell dissociation. The PI3K- and RalGDS-activating Ras mutants had, in contrast, no effect on cell dispersion. However, MEK1 was unable to promote cell motility,whereas RasV12S35 and RasV12E38 induced cell migration, suggesting that another Ras effector was responsible for cell motility. We found that the small GTPase Rac is necessary for EGF-mediated cell dispersion since overexpression of a dominant-negative mutant of Rac1 (Rac1N17) inhibited EGF-induced NBT-II cell migration. All stimuli that promoted cell migration also induced Rac activation. Finally, coexpression of active Rac1 and active MEK1 induced the motility of NBT-II cells, suggesting that Ras mediates NBT-II cell scattering through the coordinate activation of Rac and the Raf/MAPK pathway.

Genetic elements of Thermococcales

2004 ◽  
Vol 32 (2) ◽  
pp. 184-187 ◽  
Author(s):  
D. Prieur ◽  
G. Erauso ◽  
C. Geslin ◽  
S. Lucas ◽  
M. Gaillard ◽  
...  
Keyword(s):  
Recent Work ◽  
Deep Sea ◽  
Current Knowledge ◽  
Genetic Tools ◽  
Genetic Elements ◽  
Cryptic Plasmids

This minireview summarizes our current knowledge about archaeal genetic elements in the hyperthermophilic order Thermococcales in the phylum Euryarchaeota. This includes recent work on the first virus of Pyrococcus, PAV1, the discovery of novel unique virus morphotypes in hot deep-sea environments, and preliminary observations on novel cryptic plasmids. We also review the work accomplished over the last 5 years in the development of genetic tools for members of the Pyrococcus and Thermococcus genera, mainly in our laboratories.

scholarly journals Kinesin molecular motor Eg5 functions during polypeptide synthesis

2011 ◽  
Vol 22 (18) ◽  
pp. 3420-3430 ◽  
Author(s):  
Kristen M. Bartoli ◽  
Jelena Jakovljevic ◽  
John L. Woolford ◽  
William S. Saunders
Keyword(s):  
Cell Division ◽  
Molecular Motor ◽  
Spindle Assembly ◽  
Intact Cells ◽  
Nascent Polypeptide ◽  
Polypeptide Synthesis

The kinesin-related molecular motor Eg5 plays roles in cell division, promoting spindle assembly. We show that during interphase Eg5 is associated with ribosomes and is required for optimal nascent polypeptide synthesis. When Eg5 was inhibited, ribosomes no longer bound to microtubules in vitro, ribosome transit rates slowed, and polysomes accumulated in intact cells, suggesting defects in elongation or termination during polypeptide synthesis. These results demonstrate that the molecular motor Eg5 associates with ribosomes and enhances the efficiency of translation.

Spindle Assembly Checkpoint Protein Dynamics and Roles in Plant Cell Division

2011 ◽  
pp. 142-153
Author(s):  
Marie-Cécile Caillaud ◽  
Laetitia Paganelli ◽  
Philippe Lecomte ◽  
Laurent Deslandes ◽  
Michaël Quentin ◽  
...  
Keyword(s):  
Cell Division ◽  
Protein Dynamics ◽  
Plant Cell ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Checkpoint Protein ◽  
Plant Cell Division ◽  
Spindle Assembly Checkpoint Protein
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