Role of Nonmotor Microtubule-Associated Proteins in Mitotic Spindle Assembly

2017 ◽  
pp. 1-9
Author(s):  
Danica Drpic ◽  
Helder Maiato
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Mitotic Spindle Assembly

scholarly journals Ensconsin/Map7 promotes microtubule growth and centrosome separation in Drosophila neural stem cells

2014 ◽  
Vol 204 (7) ◽  
pp. 1111-1121 ◽  
Author(s):  
Emmanuel Gallaud ◽  
Renaud Caous ◽  
Aude Pascal ◽  
Franck Bazile ◽  
Jean-Philippe Gagné ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Microtubule Associated Proteins ◽  
Microtubule Polymerization ◽  
Sister Chromatids ◽  
Centrosome Separation ◽  
Associated Proteins ◽  
Microtubule Growth ◽  
Mitotic Spindle Assembly

The mitotic spindle is crucial to achieve segregation of sister chromatids. To identify new mitotic spindle assembly regulators, we isolated 855 microtubule-associated proteins (MAPs) from Drosophila melanogaster mitotic or interphasic embryos. Using RNAi, we screened 96 poorly characterized genes in the Drosophila central nervous system to establish their possible role during spindle assembly. We found that Ensconsin/MAP7 mutant neuroblasts display shorter metaphase spindles, a defect caused by a reduced microtubule polymerization rate and enhanced by centrosome ablation. In agreement with a direct effect in regulating spindle length, Ensconsin overexpression triggered an increase in spindle length in S2 cells, whereas purified Ensconsin stimulated microtubule polymerization in vitro. Interestingly, ensc-null mutant flies also display defective centrosome separation and positioning during interphase, a phenotype also detected in kinesin-1 mutants. Collectively, our results suggest that Ensconsin cooperates with its binding partner Kinesin-1 during interphase to trigger centrosome separation. In addition, Ensconsin promotes microtubule polymerization during mitosis to control spindle length independent of Kinesin-1.

scholarly journals Compartimentalized control of Cdk1 drives mitotic spindle assembly

2021 ◽  
Author(s):  
Angela Flavia Serpico ◽  
Francesco Febbraro ◽  
Caterina Pisauro ◽  
Domenico Grieco
Keyword(s):  
Mitotic Spindle ◽  
Kinase Activity ◽  
Spindle Assembly ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Microtubule Growth ◽  
Mitotic Spindle Assembly ◽  
Spindle Microtubules ◽  
Growth Promoting ◽  
Fraction Bound

During cell division, dramatic microtubular rearrangements driven by cyclin B-cdk1 (Cdk1) kinase activity mark mitosis onset leading to interphase cytoskeleton dissolution and mitotic spindle assembly. Once activated by Cdc25, that reverses inhibitory phosphorylation operated by Wee1/Myt1, Cdk1 clears the cytoplasm from microtubules by inhibiting microtubule associated proteins (MAPs) with microtubule growth-promoting properties. Nevertheless, some of these MAPs are required for spindle assembly, creating quite a conundrum. We show here that a Cdk1 fraction bound to spindle structures escaped Cdc25 action and remained inhibited by phosphorylation (i-Cdk1) in mitotic human cells. Loss or restoration of i-Cdk1 inhibited or promoted spindle assembly, respectively. Furthermore, polymerizing spindle microtubules fostered i-Cdk1 by aggregating with Wee1 and excluding Cdc25. Our data reveal that spindle assembly relies on compartimentalized control of Cdk1 activity.

scholarly journals Computer simulations predict that chromosome movements and rotations accelerate mitotic spindle assembly without compromising accuracy

2009 ◽  
Vol 106 (37) ◽  
pp. 15708-15713 ◽  
Author(s):  
Raja Paul ◽  
Roy Wollman ◽  
William T. Silkworth ◽  
Isaac K. Nardi ◽  
Daniela Cimini ◽  
...  
Keyword(s):  
Computer Simulations ◽  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Spindle Poles ◽  
Colorectal Cancer Cells ◽  
Microtubule Growth ◽  
Mitotic Spindle Assembly ◽  
Chromosome Movements ◽  
Realistic Geometry

The mitotic spindle self-assembles in prometaphase by a combination of centrosomal pathway, in which dynamically unstable microtubules search in space until chromosomes are captured, and a chromosomal pathway, in which microtubules grow from chromosomes and focus to the spindle poles. Quantitative mechanistic understanding of how spindle assembly can be both fast and accurate is lacking. Specifically, it is unclear how, if at all, chromosome movements and combining the centrosomal and chromosomal pathways affect the assembly speed and accuracy. We used computer simulations and high-resolution microscopy to test plausible pathways of spindle assembly in realistic geometry. Our results suggest that an optimal combination of centrosomal and chromosomal pathways, spatially biased microtubule growth, and chromosome movements and rotations is needed to complete prometaphase in 10–20 min while keeping erroneous merotelic attachments down to a few percent. The simulations also provide kinetic constraints for alternative error correction mechanisms, shed light on the dual role of chromosome arm volume, and compare well with experimental data for bipolar and multipolar HT-29 colorectal cancer cells.

scholarly journals The role of localization in the operation of the mitotic spindle assembly checkpoint

Cell Cycle ◽  
2009 ◽  
Vol 8 (16) ◽  
pp. 2650-2660 ◽  
Author(s):  
Maiko Lohel ◽  
Bashar Ibrahim ◽  
Stephan Diekmann ◽  
Peter Dittrich
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Spindle Assembly

scholarly journals XMAP310: A Xenopus Rescue-promoting Factor Localized to the Mitotic Spindle

1997 ◽  
Vol 139 (4) ◽  
pp. 975-983 ◽  
Author(s):  
Søren S.L. Andersen ◽  
Eric Karsenti
Keyword(s):  
Mitotic Spindle ◽  
Time Lapse ◽  
Culture Cell ◽  
Tissue Culture Cell ◽  
Microtubule Associated Proteins ◽  
Cell Biol ◽  
Egg Extracts ◽  
Associated Proteins ◽  
Cross Links

To understand the role of microtubule-associated proteins (MAPs) in the regulation of microtubule (MT) dynamics we have characterized MAPs prepared from Xenopus laevis eggs (Andersen, S.S.L., B. Buendia, J.E. Domínguez, A. Sawyer, and E. Karsenti. 1994. J. Cell Biol. 127:1289–1299). Here we report on the purification and characterization of a 310-kD MAP (XMAP310) that localizes to the nucleus in interphase and to mitotic spindle MTs in mitosis. XMAP310 is present in eggs, oocytes, a Xenopus tissue culture cell line, testis, and brain. We have purified XMAP310 to homogeneity from egg extracts. The purified protein cross-links pure MTs. Analysis of the effect of this protein on MT dynamics by time-lapse video microscopy has shown that it increases the rescue frequency 5–10-fold and decreases the shrinkage rate twofold. It has no effect on the growth rate or the catastrophe frequency. Microsequencing data suggest that XMAP230 and XMAP310 are novel MAPs. Although the three Xenopus MAPs characterized so far, XMAP215 (Vasquez, R.J., D.L. Gard, and L. Cassimeris. 1994. J. Cell Biol. 127:985–993), XMAP230, and XMAP310 are localized to the mitotic spindle, they have distinct effects on MT dynamics. While XMAP215 promotes rapid MT growth, XMAP230 decreases the catastrophe frequency and XMAP310 increases the rescue frequency. This may have important implications for the regulation of MT dynamics during spindle morphogenesis and chromosome segregation.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

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