scholarly journals Mechanical design principles of a mitotic spindle

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Jonathan J Ward ◽  
Hélio Roque ◽  
Claude Antony ◽  
François Nédélec
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Structural Integrity ◽  
Mechanical Design ◽  
Structural Components ◽  
Cell Type ◽  
And Function ◽  
Anaphase B ◽  
The Relationship ◽  
Spindle Structure

An organised spindle is crucial to the fidelity of chromosome segregation, but the relationship between spindle structure and function is not well understood in any cell type. The anaphase B spindle in fission yeast has a slender morphology and must elongate against compressive forces. This ‘pushing’ mode of chromosome transport renders the spindle susceptible to breakage, as observed in cells with a variety of defects. Here we perform electron tomographic analyses of the spindle, which suggest that it organises a limited supply of structural components to increase its compressive strength. Structural integrity is maintained throughout the spindle's fourfold elongation by organising microtubules into a rigid transverse array, preserving correct microtubule number and dynamically rescaling microtubule length.

scholarly journals Suppression of the bimC4 mitotic spindle defect by deletion of klpA, a gene encoding a KAR3-related kinesin-like protein in Aspergillus nidulans.

1993 ◽  
Vol 120 (1) ◽  
pp. 153-162 ◽  
Author(s):  
M J O'Connell ◽  
P B Meluh ◽  
M D Rose ◽  
N R Morris
Keyword(s):  
Aspergillus Nidulans ◽  
Mitotic Spindle ◽  
Structural Similarity ◽  
Temperature Sensitive ◽  
Gene Encoding ◽  
Expression Studies ◽  
Primary Amino ◽  
And Function ◽  
Spindle Function ◽  
The Relationship

To investigate the relationship between structure and function of kinesin-like proteins, we have identified by polymerase chain reaction (PCR) a new kinesin-like protein in the filamentous fungus Aspergillus nidulans, which we have designated KLPA. DNA sequence analysis showed that the predicted KLPA protein contains a COOH terminal kinesin-like motor domain. Despite the structural similarity of KLPA to the KAR3 and NCD kinesin-like proteins of Saccharomyces cerevisiae and Drosophila melanogaster, which also posses COOH-terminal kinesin-like motor domains, there are no significant sequence similarities between the nonmotor or tail portions of these proteins. Nevertheless, expression studies in S. cerevisiae showed that klpA can complement a null mutation in KAR3, indicating that primary amino acid sequence conservation between the tail domains of kinesin-like proteins is not necessarily required for conserved function. Chromosomal deletion of the klpA gene exerted no observable mutant phenotype, suggesting that in A. nidulans there are likely to be other proteins functionally redundant with KLPA. Interestingly, the temperature sensitive phenotype of a mutation in another gene, bimC, which encodes a kinesin-like protein involved in mitotic spindle function in A. nidulans, was suppressed by deletion of klpA. We hypothesize that the loss of KLPA function redresses unbalanced forces within the spindle caused by mutation in bimC, and that the KLPA and BIMC kinesin-like proteins may play opposing roles in spindle function.

Mitotic motors and chromosome segregation: the mechanism of anaphase B

2011 ◽  
Vol 39 (5) ◽  
pp. 1149-1153 ◽  
Author(s):  
Ingrid Brust-Mascher ◽  
Jonathan M. Scholey
Keyword(s):  
Chromosome Segregation ◽  
Cyclin B ◽  
Spindle Poles ◽  
Mitotic Motors ◽  
Balance Of Forces ◽  
Spindle Elongation ◽  
Anaphase B ◽  
Relationship Of ◽  
The Relationship ◽  
Acting In Concert

Anaphase B spindle elongation plays an important role in chromosome segregation. In the present paper, we discuss our model for anaphase B in Drosophila syncytial embryos, in which spindle elongation depends on an ip (interpolar) MT (microtubule) sliding filament mechanism generated by homotetrameric kinesin-5 motors acting in concert with poleward ipMT flux, which acts as an ‘on/off’ switch. Specifically, the pre-anaphase B spindle is maintained at a steady-state length by the balance between ipMT sliding and ipMT depolymerization at spindle poles, producing poleward flux. Cyclin B degradation at anaphase B onset triggers: (i) an MT catastrophe gradient causing ipMT plus ends to invade the overlap zone where ipMT sliding forces are generated; and (ii) the inhibition of ipMT minus-end depolymerization so flux is turned ‘off’, tipping the balance of forces to allow outward ipMT sliding to push apart the spindle poles. We briefly comment on the relationship of this model to anaphase B in other systems.

scholarly journals Nucleocytoplasmic transport in the midzone membrane domain controls yeast mitotic spindle disassembly

2015 ◽  
Vol 209 (3) ◽  
pp. 387-402 ◽  
Author(s):  
Rafael Lucena ◽  
Noah Dephoure ◽  
Steve P. Gygi ◽  
Douglas R. Kellogg ◽  
Victor A. Tallada ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Nucleocytoplasmic Transport ◽  
Membrane Domain ◽  
Aaa Atpase ◽  
Membrane Compartment ◽  
Spindle Disassembly ◽  
Spindle Midzone ◽  
Anaphase B

During each cell cycle, the mitotic spindle is efficiently assembled to achieve chromosome segregation and then rapidly disassembled as cells enter cytokinesis. Although much has been learned about assembly, how spindles disassemble at the end of mitosis remains unclear. Here we demonstrate that nucleocytoplasmic transport at the membrane domain surrounding the mitotic spindle midzone, here named the midzone membrane domain (MMD), is essential for spindle disassembly in Schizosaccharomyces pombe cells. We show that, during anaphase B, Imp1-mediated transport of the AAA-ATPase Cdc48 protein at the MMD allows this disassembly factor to localize at the spindle midzone, thereby promoting spindle midzone dissolution. Our findings illustrate how a separate membrane compartment supports spindle disassembly in the closed mitosis of fission yeast.

Driving chromosome segregation: lessons from the human and Drosophila centromere–kinetochore machinery

2010 ◽  
Vol 38 (6) ◽  
pp. 1667-1675 ◽  
Author(s):  
Bernardo Orr ◽  
Olga Afonso ◽  
Tália Feijão ◽  
Claudio E. Sunkel
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Spindle Assembly Checkpoint ◽  
Genomic Stability ◽  
Mitotic Progression ◽  
Chromosomal Locus ◽  
Microtubule Attachment ◽  
Sister Chromatids ◽  
And Function ◽  
Drosophila Cells

The kinetochore is a complex molecular machine that serves as the interface between sister chromatids and the mitotic spindle. The kinetochore assembles at a particular chromosomal locus, the centromere, which is essential to maintain genomic stability during cell division. The kinetochore is a macromolecular puzzle of subcomplexes assembled in a hierarchical manner and fulfils three main functions: microtubule attachment, chromosome and sister chromatid movement, and regulation of mitotic progression though the spindle assembly checkpoint. In the present paper we compare recent results on the assembly, organization and function of the kinetochore in human and Drosophila cells and conclude that, although essential functions are highly conserved, there are important differences that might help define what is a minimal chromosome segregation machinery.

scholarly journals Conditional Mutations in γ-Tubulin Reveal Its Involvement in Chromosome Segregation and Cytokinesis

2001 ◽  
Vol 12 (8) ◽  
pp. 2469-2481 ◽  
Author(s):  
Triscia W. Hendrickson ◽  
Joyce Yao ◽  
Saswata Bhadury ◽  
Anita H. Corbett ◽  
Harish C. Joshi
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Homology Model ◽  
Deleterious Mutations ◽  
Alanine Scanning Mutagenesis ◽  
Structural Mapping ◽  
Lethal Mutations ◽  
M Phase ◽  
Cold Sensitive ◽  
And Function

γ-Tubulin is a conserved essential protein required for assembly and function of the mitotic spindle in humans and yeast. For example, human γ-tubulin can replace the γ-tubulin gene inSchizosaccharomyces pombe. To understand the structural/functional domains of γ-tubulin, we performed a systematic alanine-scanning mutagenesis of human γ-tubulin (TUBG1) and studied phenotypes of each mutant allele inS. pombe. Our screen, both in the presence and absence of the endogenous S. pombe γ-tubulin, resulted in 11 lethal mutations and 12 cold-sensitive mutations. Based on structural mapping onto a homology model of human γ-tubulin generated by free energy minimization, all deleterious mutations are found in residues predicted to be located on the surface, some in positions to interact with α- and/or β-tubulins in the microtubule lattice. As expected, one class of tubg1 mutations has either an abnormal assembly or loss of the mitotic spindle. Surprisingly, a subset of mutants with abnormal spindles does not arrest in M phase but proceeds through anaphase followed by abnormal cytokinesis. These studies reveal that in addition to its previously appreciated role in spindle microtubule nucleation, γ-tubulin is involved in the coordination of postmetaphase events, anaphase, and cytokinesis.

scholarly journals Polewards microtubule flux in the mitotic spindle: evidence from photoactivation of fluorescence.

1989 ◽  
Vol 109 (2) ◽  
pp. 637-652 ◽  
Author(s):  
T J Mitchison
Keyword(s):  
Molecular Dynamics ◽  
Tissue Culture ◽  
Strong Evidence ◽  
Mitotic Spindle ◽  
Living Cells ◽  
Structure And Function ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
And Function ◽  
Spindle Structure

I have synthesized a novel derivative of carboxyfluorescein that is nonfluorescent, but can be converted to a fluorescent form by exposure to 365-nm light. This photoactivable, fluorescent probe was covalently attached to tubulin and microinjected into mitotic tissue culture cells, where it incorporated into functional spindles. To generate a fluorescent bar across the mitotic spindle, metaphase cells were irradiated with a slit microbeam. This bar decreased in intensity over the first minute, presumably due to turnover of nonkinetochore microtubules. The remaining fluorescent zones, now presumably restricted to kinetochore microtubules, moved polewards at 0.3-0.7 microns/min. This result provides strong evidence for polewards flux in kinetochore microtubules. In conjunction with earlier biotin-tubulin incorporation experiments (Mitchison, T. J., L. Evans, E. Schulze, and M. Kirschner. 1986. Cell. 45:515-527), I conclude that microtubules polymerize at kinetochores and depolymerize near the poles throughout metaphase. The significance of this observation for spindle structure and function is discussed. Local photoactivation of fluorescence should be a generally useful method for following molecular dynamics inside living cells.

scholarly journals Analysis of kinesin motor function at budding yeast kinetochores

2006 ◽  
Vol 172 (6) ◽  
pp. 861-874 ◽  
Author(s):  
Jessica D. Tytell ◽  
Peter K. Sorger
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Motor Function ◽  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Budding Yeast ◽  
Kinesin Motor ◽  
Complex Processes ◽  
Sister Chromatids ◽  
Higher Eukaryotes ◽  
And Function

Accurate chromosome segregation during mitosis requires biorientation of sister chromatids on the microtubules (MT) of the mitotic spindle. Chromosome–MT binding is mediated by kinetochores, which are multiprotein structures that assemble on centromeric (CEN) DNA. The simple CENs of budding yeast are among the best understood, but the roles of kinesin motor proteins at yeast kinetochores have yet to be determined, despite evidence of their importance in higher eukaryotes. We show that all four nuclear kinesins in Saccharomyces cerevisiae localize to kinetochores and function in three distinct processes. Kip1p and Cin8p, which are kinesin-5/BimC family members, cluster kinetochores into their characteristic bilobed metaphase configuration. Kip3p, a kinesin-8,-13/KinI kinesin, synchronizes poleward kinetochore movement during anaphase A. The kinesin-14 motor Kar3p appears to function at the subset of kinetochores that become detached from spindle MTs. These data demonstrate roles for structurally diverse motors in the complex processes of chromosome segregation and reveal important similarities and intriguing differences between higher and lower eukaryotes.

scholarly journals Emerging Insights into the Function of Kinesin-8 Proteins in Microtubule Length Regulation

2018 ◽  
Author(s):  
Sanjay Shrestha ◽  
Mark Hazelbaker ◽  
Amber L. Yount ◽  
Claire E. Walczak
Keyword(s):  
Motor Activity ◽  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Structure And Function ◽  
Cellular Processes ◽  
Cellular Factors ◽  
Destabilizing Factors ◽  
Length Regulation ◽  
Mitotic Spindle Assembly ◽  
And Function

Proper regulation of microtubules (MTs) is critical for the execution of diverse cellular processes, including mitotic spindle assembly and chromosome segregation. There are a multitude of cellular factors that regulate the dynamicity of MTs and play critical roles in mitosis. Members of the Kinesin-8 family of motor proteins act as MT-destabilizing factors to control MT length in a spatially and temporally regulated manner. In this review, we focus on recent advances in our understanding of the structure and function of the Kinesin-8 motor domain, and the emerging contributions of the C-terminal tail of Kinesin-8 proteins to regulate motor activity and localization.

scholarly journals Novel Roles for Saccharomyces cerevisiae Mitotic Spindle Motors

1999 ◽  
Vol 147 (2) ◽  
pp. 335-350 ◽  
Author(s):  
Frank R. Cottingham ◽  
Larisa Gheber ◽  
Dana L. Miller ◽  
M. Andrew Hoyt
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Spindle ◽  
Structural Integrity ◽  
Cytoplasmic Dynein ◽  
Spindle Positioning ◽  
Bipolar Spindle ◽  
Accessory Factor ◽  
Spindle Function ◽  
Related Proteins ◽  
Spindle Structure

The single cytoplasmic dynein and five of the six kinesin-related proteins encoded by Saccharomyces cerevisiae participate in mitotic spindle function. Some of the motors operate within the nucleus to assemble and elongate the bipolar spindle. Others operate on the cytoplasmic microtubules to effect spindle and nuclear positioning within the cell. This study reveals that kinesin-related Kar3p and Kip3p are unique in that they perform roles both inside and outside the nucleus. Kar3p, like Kip3p, was found to be required for spindle positioning in the absence of dynein. The spindle positioning role of Kar3p is performed in concert with the Cik1p accessory factor, but not the homologous Vik1p. Kar3p and Kip3p were also found to overlap for a function essential for the structural integrity of the bipolar spindle. The cytoplasmic and nuclear roles of both these motors could be partially substituted for by the microtubule-destabilizing agent benomyl, suggesting that these motors perform an essential microtubule-destabilizing function. In addition, we found that yeast cell viability could be supported by as few as two microtubule-based motors: the BimC-type kinesin Cin8p, required for spindle structure, paired with either Kar3p or Kip3p, required for both spindle structure and positioning.

scholarly journals Emerging Insights into the Function of Kinesin-8 Proteins in Microtubule Length Regulation

Biomolecules ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 1 ◽  
Author(s):  
Sanjay Shrestha ◽  
Mark Hazelbaker ◽  
Amber Yount ◽  
Claire Walczak
Keyword(s):  
Motor Activity ◽  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Structure And Function ◽  
Cellular Processes ◽  
Cellular Factors ◽  
Destabilizing Factors ◽  
Length Regulation ◽  
Mitotic Spindle Assembly ◽  
And Function

Proper regulation of microtubules (MTs) is critical for the execution of diverse cellular processes, including mitotic spindle assembly and chromosome segregation. There are a multitude of cellular factors that regulate the dynamicity of MTs and play critical roles in mitosis. Members of the Kinesin-8 family of motor proteins act as MT-destabilizing factors to control MT length in a spatially and temporally regulated manner. In this review, we focus on recent advances in our understanding of the structure and function of the Kinesin-8 motor domain, and the emerging contributions of the C-terminal tail of Kinesin-8 proteins to regulate motor activity and localization.

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