scholarly journals Kinetochore-driven formation of kinetochore fibers contributes to spindle assembly during animal mitosis

2004 ◽  
Vol 167 (5) ◽  
pp. 831-840 ◽  
Author(s):  
Helder Maiato ◽  
Conly L. Rieder ◽  
Alexey Khodjakov
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
S2 Cells ◽  
Spindle Poles ◽  
Drosophila S2 Cells ◽  
Mitotic Spindle Assembly ◽  
Normal Mitosis ◽  
Proper Orientation ◽  
Dependent Mechanism

It is now clear that a centrosome-independent pathway for mitotic spindle assembly exists even in cells that normally possess centrosomes. The question remains, however, whether this pathway only activates when centrosome activity is compromised, or whether it contributes to spindle morphogenesis during a normal mitosis. Here, we show that many of the kinetochore fibers (K-fibers) in centrosomal Drosophila S2 cells are formed by the kinetochores. Initially, kinetochore-formed K-fibers are not oriented toward a spindle pole but, as they grow, their minus ends are captured by astral microtubules (MTs) and transported poleward through a dynein-dependent mechanism. This poleward transport results in chromosome bi-orientation and congression. Furthermore, when individual K-fibers are severed by laser microsurgery, they regrow from the kinetochore outward via MT plus-end polymerization at the kinetochore. Thus, even in the presence of centrosomes, the formation of some K-fibers is initiated by the kinetochores. However, centrosomes facilitate the proper orientation of K-fibers toward spindle poles by integrating them into a common spindle.

scholarly journals Genes involved in centrosome-independent mitotic spindle assembly in Drosophila S2 cells

2013 ◽  
Vol 110 (49) ◽  
pp. 19808-19813 ◽  
Author(s):  
S. Moutinho-Pereira ◽  
N. Stuurman ◽  
O. Afonso ◽  
M. Hornsveld ◽  
P. Aguiar ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
S2 Cells ◽  
Drosophila S2 Cells ◽  
Mitotic Spindle Assembly

scholarly journals Mechanisms for focusing mitotic spindle poles by minus end–directed motor proteins

2005 ◽  
Vol 171 (2) ◽  
pp. 229-240 ◽  
Author(s):  
Gohta Goshima ◽  
François Nédélec ◽  
Ronald D. Vale
Keyword(s):  
Rna Interference ◽  
High Resolution ◽  
Computer Modeling ◽  
Mitotic Spindle ◽  
Motor Proteins ◽  
Spindle Pole ◽  
S2 Cells ◽  
Spindle Poles ◽  
Drosophila S2 Cells ◽  
High Resolution Microscopy

During the formation of the metaphase spindle in animal somatic cells, kinetochore microtubule bundles (K fibers) are often disconnected from centrosomes, because they are released from centrosomes or directly generated from chromosomes. To create the tightly focused, diamond-shaped appearance of the bipolar spindle, K fibers need to be interconnected with centrosomal microtubules (C-MTs) by minus end–directed motor proteins. Here, we have characterized the roles of two minus end–directed motors, dynein and Ncd, in such processes in Drosophila S2 cells using RNA interference and high resolution microscopy. Even though these two motors have overlapping functions, we show that Ncd is primarily responsible for focusing K fibers, whereas dynein has a dominant function in transporting K fibers to the centrosomes. We also report a novel localization of Ncd to the growing tips of C-MTs, which we show is mediated by the plus end–tracking protein, EB1. Computer modeling of the K fiber focusing process suggests that the plus end localization of Ncd could facilitate the capture and transport of K fibers along C-MTs. From these results and simulations, we propose a model on how two minus end–directed motors cooperate to ensure spindle pole coalescence during mitosis.

scholarly journals Genes Required for Mitotic Spindle Assembly in Drosophila S2 Cells

Science ◽  
2007 ◽  
Vol 316 (5823) ◽  
pp. 417-421 ◽  
Author(s):  
G. Goshima ◽  
R. Wollman ◽  
S. S. Goodwin ◽  
N. Zhang ◽  
J. M. Scholey ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
S2 Cells ◽  
Drosophila S2 Cells ◽  
Mitotic Spindle Assembly

scholarly journals Targeting Alp7/TACC to the spindle pole body is essential for mitotic spindle assembly in fission yeast

FEBS Letters ◽  
2014 ◽  
Vol 588 (17) ◽  
pp. 2814-2821 ◽  
Author(s):  
Ngang Heok Tang ◽  
Naoyuki Okada ◽  
Chii Shyang Fong ◽  
Kunio Arai ◽  
Masamitsu Sato ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
Pole Body ◽  
Mitotic Spindle Assembly

scholarly journals The APC/C targets the Cep152-Cep63 complex at the centrosome to regulate mitotic spindle assembly

2021 ◽  
Author(s):  
Thomas Tischer ◽  
Jing Yang ◽  
David Barford
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Protein Abundance ◽  
Anaphase Promoting Complex ◽  
Mitotic Progression ◽  
Centrosomal Protein ◽  
Temporal Regulation ◽  
Spindle Poles ◽  
Main Protein ◽  
Mitotic Spindle Assembly

The control of protein abundance is a fundamental regulatory mechanism during mitosis. The anaphase promoting complex/cyclosome (APC/C) is the main protein ubiquitin ligase responsible for the temporal regulation of mitotic progression. It has been proposed that the APC/C might fulfil other functions including assembly of the mitotic spindle. Here, we show that the APC/C localizes to centrosomes, the organizers of the eukaryotic microtubule cytoskeleton, specifically during mitosis. Recruitment of the APC/C to spindle poles requires the centrosomal protein Cep152, and we identified Cep152 as both an APC/C interaction partner and as an APC/C substrate. Previous studies showed that Cep152 forms a complex with Cep57 and Cep63. The APC/C-mediated ubiquitination of Cep152 at the centrosome releases Cep57 from this inhibitory complex and enables its interaction with pericentrin, a critical step in promoting microtubule nucleation. Thus, our study extends the function of the APC/C from being a regulator of mitosis to also acting as a positive governor of spindle assembly. The APC/C thereby integrates control of these two important processes in a temporal manner.

scholarly journals Relative contributions of chromatin and kinetochores to mitotic spindle assembly

2009 ◽  
Vol 187 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Christopher B. O'Connell ◽  
Jadranka Lončarek ◽  
Petr Kaláb ◽  
Alexey Khodjakov
Keyword(s):  
Mitotic Spindle ◽  
Dominant Role ◽  
Spindle Assembly ◽  
High Concentration ◽  
Animal Cells ◽  
Microtubule Attachment ◽  
Mitotic Spindle Assembly ◽  
Assembly Pathways ◽  
Mitosis And Meiosis ◽  
Normal Mitosis

During mitosis and meiosis in animal cells, chromosomes actively participate in spindle assembly by generating a gradient of Ran guanosine triphosphate (RanGTP). A high concentration of RanGTP promotes microtubule nucleation and stabilization in the vicinity of chromatin. However, the relative contributions of chromosome arms and centromeres/kinetochores in this process are not known. In this study, we address this issue using cells undergoing mitosis with unreplicated genomes (MUG). During MUG, chromatin is rapidly separated from the forming spindle, and both centrosomal and noncentrosomal spindle assembly pathways are active. MUG chromatin is coated with RCC1 and establishes a RanGTP gradient. However, a robust spindle forms around kinetochores/centromeres outside of the gradient peak. When stable kinetochore microtubule attachment is prevented by Nuf2 depletion in both MUG and normal mitosis, chromatin attracts astral microtubules but cannot induce spindle assembly. These results support a model in which kinetochores play the dominant role in the chromosome-mediated pathway of mitotic spindle assembly.

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 Microtubule pivoting enables mitotic spindle assembly in S. cerevisiae

2021 ◽  
Vol 220 (3) ◽  
Author(s):  
Kimberly K. Fong ◽  
Trisha N. Davis ◽  
Charles L. Asbury
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Force Generation ◽  
Initial Contact ◽  
Bipolar Spindle ◽  
Spindle Poles ◽  
Mitotic Spindle Assembly ◽  
Spindle Microtubules ◽  
Pole Component

To assemble a bipolar spindle, microtubules emanating from two poles must bundle into an antiparallel midzone, where plus end–directed motors generate outward pushing forces to drive pole separation. Midzone cross-linkers and motors display only modest preferences for antiparallel filaments, and duplicated poles are initially tethered together, an arrangement that instead favors parallel interactions. Pivoting of microtubules around spindle poles might help overcome this geometric bias, but the intrinsic pivoting flexibility of the microtubule–pole interface has not been directly measured, nor has its importance during early spindle assembly been tested. By measuring the pivoting of microtubules around isolated yeast spindle poles, we show that pivoting flexibility can be modified by mutating a microtubule-anchoring pole component, Spc110. By engineering mutants with different flexibilities, we establish the importance of pivoting in vivo for timely pole separation. Our results suggest that passive thermal pivoting can bring microtubules from side-by-side poles into initial contact, but active minus end–directed force generation will be needed to achieve antiparallel alignment.

Sign in / Sign up

Export Citation Format

Share Document