scholarly journals csi2p modulates microtubule dynamics and organizes the bipolar spindle for chromosome segregation

2014 ◽  
Vol 25 (24) ◽  
pp. 3900-3908 ◽  
Author(s):  
Judite Costa ◽  
Chuanhai Fu ◽  
V. Mohini Khare ◽  
Phong T. Tran
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Microtubule Dynamics ◽  
High Rate ◽  
Spindle Formation ◽  
Bipolar Spindle ◽  
Eukaryotic Chromosome ◽  
Relative Contribution ◽  
Multiple Phenotypes

Proper chromosome segregation is of paramount importance for proper genetic inheritance. Defects in chromosome segregation can lead to aneuploidy, which is a hallmark of cancer cells. Eukaryotic chromosome segregation is accomplished by the bipolar spindle. Additional mechanisms, such as the spindle assembly checkpoint and centromere positioning, further help to ensure complete segregation fidelity. Here we present the fission yeast csi2+. csi2p localizes to the spindle poles, where it regulates mitotic microtubule dynamics, bipolar spindle formation, and subsequent chromosome segregation. csi2 deletion (csi2Δ) results in abnormally long mitotic microtubules, high rate of transient monopolar spindles, and subsequent high rate of chromosome segregation defects. Because csi2Δ has multiple phenotypes, it enables estimates of the relative contribution of the different mechanisms to the overall chromosome segregation process. Centromere positioning, microtubule dynamics, and bipolar spindle formation can all contribute to chromosome segregation. However, the major determinant of chromosome segregation defects in fission yeast may be microtubule dynamic defects.

scholarly journals A microtubule polymerase cooperates with the kinesin-6 motor and a microtubule cross-linker to promote bipolar spindle assembly in the absence of kinesin-5 and kinesin-14 in fission yeast

2017 ◽  
Vol 28 (25) ◽  
pp. 3647-3659 ◽  
Author(s):  
Masashi Yukawa ◽  
Tomoki Kawakami ◽  
Masaki Okazaki ◽  
Kazunori Kume ◽  
Ngang Heok Tang ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Spindle Pole Body ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
Temperature Sensitive ◽  
Bipolar Spindle ◽  
Pole Body ◽  
Cross Linker ◽  
Spindle Elongation

Accurate chromosome segregation relies on the bipolar mitotic spindle. In many eukaryotes, spindle formation is driven by the plus-end–directed motor kinesin-5 that generates outward force to establish spindle bipolarity. Its inhibition leads to the emergence of monopolar spindles with mitotic arrest. Intriguingly, simultaneous inactivation of the minus-end–directed motor kinesin-14 restores spindle bipolarity in many systems. Here we show that in fission yeast, three independent pathways contribute to spindle bipolarity in the absence of kinesin-5/Cut7 and kinesin-14/Pkl1. One is kinesin-6/Klp9 that engages with spindle elongation once short bipolar spindles assemble. Klp9 also ensures the medial positioning of anaphase spindles to prevent unequal chromosome segregation. Another is the Alp7/TACC-Alp14/TOG microtubule polymerase complex. Temperature-sensitive alp7cut7pkl1 mutants are arrested with either monopolar or very short spindles. Forced targeting of Alp14 to the spindle pole body is sufficient to render alp7cut7pkl1 triply deleted cells viable and promote spindle assembly, indicating that Alp14-mediated microtubule polymerization from the nuclear face of the spindle pole body could generate outward force in place of Cut7 during early mitosis. The third pathway involves the Ase1/PRC1 microtubule cross-linker that stabilizes antiparallel microtubules. Our study, therefore, unveils multifaceted interplay among kinesin-dependent and -independent pathways leading to mitotic bipolar spindle assembly.

Regulation of Microtubule Assembly: The View From The End

2000 ◽  
Vol 6 (S2) ◽  
pp. 80-81
Author(s):  
L. Cassimeris ◽  
C. Spittle ◽  
M. Kratzer
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Dynamic Instability ◽  
Intrinsic Property ◽  
Microtubule Dynamics ◽  
Microtubule Assembly ◽  
Chromosome Movement ◽  
Spindle Formation ◽  
Associated Proteins

The mitotic spindle is responsible for chromosome movement during mitosis. It is composed of a dynamic array of microtubules and associated proteins whose assembly and constant turnover are required for both spindle formation and chromosome movement. Because microtubule assembly and turnover are necessary for chromosome segregation, we are studying how cells regulate microtubule dynamics. Microtubules are polarized polymers composed of tubulin subunits; they assemble by a process of dynamic instability where individual microtubules exist in persistent phases of elongation or rapid shortening with abrupt transitions between these two states. The switch from elongation to shortening is termed catastrophe, and the switch from shortening to elongation, rescue. Although dynamic instability is an intrinsic property of the tubulin subunits, cells use associated proteins to both speed elongation (∼ 10 fold) and regulate transitions.The only protein isolated to date capable of promoting fast polymerization consistent with rates in vivo is XMAP215, a 215 kD protein from Xenopus eggs.

scholarly journals Interplay of Microtubule Dynamics and Sliding during Bipolar Spindle Formation in Mammalian Cells

2009 ◽  
Vol 19 (24) ◽  
pp. 2108-2113 ◽  
Author(s):  
Swapna Kollu ◽  
Samuel F. Bakhoum ◽  
Duane A. Compton
Keyword(s):  
Mammalian Cells ◽  
Microtubule Dynamics ◽  
Spindle Formation ◽  
Bipolar Spindle

scholarly journals Interdependency of Fission Yeast Alp14/TOG and Coiled Coil Protein Alp7 in Microtubule Localization and Bipolar Spindle Formation

2004 ◽  
Vol 15 (4) ◽  
pp. 1609-1622 ◽  
Author(s):  
Masamitsu Sato ◽  
Leah Vardy ◽  
Miguel Angel Garcia ◽  
Nirada Koonrugsa ◽  
Takashi Toda
Keyword(s):  
Fission Yeast ◽  
Spindle Pole Body ◽  
Coiled Coil ◽  
Spindle Pole ◽  
Mitotic Spindles ◽  
Microtubule Organization ◽  
Spindle Formation ◽  
Bipolar Spindle ◽  
C Terminus ◽  
Step Model

The Dis1/TOG family plays a pivotal role in microtubule organization. In fission yeast, Alp14 and Dis1 share an essential function in bipolar spindle formation. Here, we characterize Alp7, a novel coiled-coil protein that is required for organization of bipolar spindles. Both Alp7 and Alp14 colocalize to the spindle pole body (SPB) and mitotic spindles. Alp14 localization to these sites is fully dependent upon Alp7. Conversely, in the absence of Alp14, Alp7 localizes to the SPBs, but not mitotic spindles. Alp7 forms a complex with Alp14, where the C-terminal region of Alp14 interacts with the coiled-coil domain of Alp7. Intriguingly, this Alp14 C terminus is necessary and sufficient for mitotic spindle localization. Overproduction of either full-length or coiled-coil region of Alp7 results in abnormal V-shaped spindles and stabilization of interphase microtubules, which is induced independent of Alp14. Alp7 may be a functional homologue of animal TACC. Our results shed light on an interdependent relationship between Alp14/TOG and Alp7. We propose a two-step model that accounts for the recruitment of Alp7 and Alp14 to the SPB and microtubules.

scholarly journals Spindle checkpoint activation at meiosis I advances anaphase II onset via meiosis-specific APC/C regulation

2008 ◽  
Vol 182 (2) ◽  
pp. 277-288 ◽  
Author(s):  
Ayumu Yamamoto ◽  
Kenji Kitamura ◽  
Daisuke Hihara ◽  
Yukinobu Hirose ◽  
Satoshi Katsuyama ◽  
...  
Keyword(s):  
Protein Degradation ◽  
Fission Yeast ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Related Factor ◽  
Anaphase Promoting Complex ◽  
Checkpoint Activation ◽  
Anaphase Onset ◽  
Yeast Meiosis ◽  
Meiosis I

During mitosis, the spindle assembly checkpoint (SAC) inhibits the Cdc20-activated anaphase-promoting complex/cyclosome (APC/CCdc20), which promotes protein degradation, and delays anaphase onset to ensure accurate chromosome segregation. However, the SAC function in meiotic anaphase regulation is poorly understood. Here, we examined the SAC function in fission yeast meiosis. As in mitosis, a SAC factor, Mad2, delayed anaphase onset via Slp1 (fission yeast Cdc20) when chromosomes attach to the spindle improperly. However, when the SAC delayed anaphase I, the interval between meiosis I and II shortened. Furthermore, anaphase onset was advanced and the SAC effect was reduced at meiosis II. The advancement of anaphase onset depended on a meiosis-specific, Cdc20-related factor, Fzr1/Mfr1, which contributed to anaphase cyclin decline and anaphase onset and was inefficiently inhibited by the SAC. Our findings show that impacts of SAC activation are not confined to a single division at meiosis due to meiosis-specific APC/C regulation, which has probably been evolved for execution of two meiotic divisions.

scholarly journals Nek5 promotes centrosome integrity in interphase and loss of centrosome cohesion in mitosis

2015 ◽  
Vol 209 (3) ◽  
pp. 339-348 ◽  
Author(s):  
Suzanna L. Prosser ◽  
Navdeep K. Sahota ◽  
Laurence Pelletier ◽  
Ciaran G. Morrison ◽  
Andrew M. Fry
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Cell Cycle Progression ◽  
Primary Cilia ◽  
Microtubule Nucleation ◽  
Cycle Progression ◽  
Spindle Formation ◽  
Mitotic Entry ◽  
Bipolar Spindle ◽  
Centrosome Separation

Nek5 is a poorly characterized member of the NIMA-related kinase family, other members of which play roles in cell cycle progression and primary cilia function. Here, we show that Nek5, similar to Nek2, localizes to the proximal ends of centrioles. Depletion of Nek5 or overexpression of kinase-inactive Nek5 caused unscheduled separation of centrosomes in interphase, a phenotype also observed upon overexpression of active Nek2. However, separated centrosomes that resulted from Nek5 depletion remained relatively close together, exhibited excess recruitment of the centrosome linker protein rootletin, and had reduced levels of Nek2. In addition, Nek5 depletion led to loss of PCM components, including γ-tubulin, pericentrin, and Cdk5Rap2, with centrosomes exhibiting reduced microtubule nucleation. Upon mitotic entry, Nek5-depleted cells inappropriately retained centrosome linker components and exhibited delayed centrosome separation and defective chromosome segregation. Hence, Nek5 is required for the loss of centrosome linker proteins and enhanced microtubule nucleation that lead to timely centrosome separation and bipolar spindle formation in mitosis.

scholarly journals The fission yeast SPB component Cut12 links bipolar spindle formation to mitotic control

1998 ◽  
Vol 12 (7) ◽  
pp. 927-942 ◽  
Author(s):  
A. J. Bridge ◽  
M. Morphew ◽  
R. Bartlett ◽  
I. M. Hagan
Keyword(s):  
Fission Yeast ◽  
Spindle Formation ◽  
Bipolar Spindle ◽  
Mitotic Control

scholarly journals CLASP2 binding to curved microtubule tips promotes flux and stabilizes kinetochore attachments

2019 ◽  
pp. jcb.201905080 ◽  
Author(s):  
Hugo Girão ◽  
Naoyuki Okada ◽  
Tony A. Rodrigues ◽  
Alexandra O. Silva ◽  
Ana C. Figueiredo ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Protein Interaction ◽  
Half Life ◽  
Spindle Assembly Checkpoint ◽  
Underlying Mechanism ◽  
Microtubule Dynamics ◽  
Microtubule Depolymerization ◽  
Binding Properties ◽  
Chromosome Congression ◽  
Self Association

CLASPs are conserved microtubule plus-end–tracking proteins that suppress microtubule catastrophes and independently localize to kinetochores during mitosis. Thus, CLASPs are ideally positioned to regulate kinetochore–microtubule dynamics required for chromosome segregation fidelity, but the underlying mechanism remains unknown. Here, we found that human CLASP2 exists predominantly as a monomer in solution, but it can self-associate through its C-terminal kinetochore-binding domain. Kinetochore localization was independent of self-association, and driving monomeric CLASP2 to kinetochores fully rescued normal kinetochore–microtubule dynamics, while partially sustaining mitosis. CLASP2 kinetochore localization, recognition of growing microtubule plus-ends through EB–protein interaction, and the ability to associate with curved microtubule protofilaments through TOG2 and TOG3 domains independently sustained normal spindle length, timely spindle assembly checkpoint satisfaction, chromosome congression, and faithful segregation. Measurements of kinetochore–microtubule half-life and poleward flux revealed that CLASP2 regulates kinetochore–microtubule dynamics by integrating distinctive microtubule-binding properties at the kinetochore–microtubule interface. We propose that kinetochore CLASP2 suppresses microtubule depolymerization and detachment by binding to curved protofilaments at microtubule plus-ends.

scholarly journals The V260I Mutation in Fission Yeast α-Tubulin Atb2 Affects Microtubule Dynamics and EB1-Mal3 Localization and Activates the Bub1 Branch of the Spindle Checkpoint

2006 ◽  
Vol 17 (3) ◽  
pp. 1421-1435 ◽  
Author(s):  
Kazuhide Asakawa ◽  
Kazunori Kume ◽  
Muneyoshi Kanai ◽  
Tetsuya Goshima ◽  
Kohji Miyahara ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Spindle Checkpoint ◽  
Spindle Pole ◽  
Vital Role ◽  
Microtubule Dynamics ◽  
High Rate ◽  
Single Amino Acid ◽  
Temperature Sensitive ◽  
Spindle Pole Bodies ◽  
Synthetically Lethal

We have identified a novel temperature-sensitive mutant of fission yeast α-tubulin Atb2 (atb2-983) that contains a single amino acid substitution (V260I). Atb2-983 is incorporated into the microtubules, and their overall structures are not altered noticeably, but microtubule dynamics is compromised during interphase. atb2-983 displays a high rate of chromosome missegregation and is synthetically lethal with deletions in a subset of spindle checkpoint genes including bub1, bub3, and mph1, but not with mad1, mad2, and mad3. During early mitosis in this mutant, Bub1, but not Mad2, remains for a prolonged period in the kinetochores that are situated in proximity to one of the two SPBs (spindle pole bodies). High dosage mal3+, encoding EB1 homologue, rescues atb2-983, suggesting that Mal3 function is compromised. Consistently, Mal3 localization and binding between Mal3 and Atb2-983 are impaired significantly, and a mal3 single mutant, such as atb2-983, displays prolonged Bub1 kinetochore localization. Furthermore in atb2-983 back-and-forth centromere oscillation during prometaphase is abolished. Intriguingly, this oscillation still occurs in the mal3 mutant, indicating that there is another defect independent of Mal3. These results show that microtubule dynamics is important for coordinated execution of mitotic events, in which Mal3 plays a vital role.

scholarly journals The Essentiality of the Fungus-Specific Dam1 Complex Is Correlated with a One-Kinetochore-One-Microtubule Interaction Present throughout the Cell Cycle, Independent of the Nature of a Centromere

2011 ◽  
Vol 10 (10) ◽  
pp. 1295-1305 ◽  
Author(s):  
Jitendra Thakur ◽  
Kaustuv Sanyal
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Candida Albicans ◽  
Fission Yeast ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Mitotic Chromosome ◽  
Content Type ◽  
Spindle Elongation ◽  
Dam1 Complex

ABSTRACTA fungus-specific outer kinetochore complex, the Dam1 complex, is essential inSaccharomyces cerevisiae, nonessential in fission yeast, and absent from metazoans. The reason for the reductive evolution of the functionality of this complex remains unknown. BothCandida albicansandSchizosaccharomyces pombehave regional centromeres as opposed to the short-point centromeres ofS. cerevisiae. The interaction of one microtubule per kinetochore is established both inS. cerevisiaeandC. albicansearly during the cell cycle, which is in contrast to the multiple microtubules that bind to a kinetochore only during mitosis inS. pombe. Moreover, the Dam1 complex is associated with the kinetochore throughout the cell cycle inS. cerevisiaeandC. albicansbut only during mitosis inS. pombe. Here, we show that the Dam1 complex is essential for viability and indispensable for proper mitotic chromosome segregation inC. albicans. The kinetochore localization of the Dam1 complex is independent of the kinetochore-microtubule interaction, but the function of this complex is monitored by a spindle assembly checkpoint. Strikingly, the Dam1 complex is required to prevent precocious spindle elongation in premitotic phases. Thus, constitutive kinetochore localization associated with a one-microtubule-one kinetochore type of interaction, but not the length of a centromere, is correlated with the essentiality of the Dam1 complex.

Sign in / Sign up

Export Citation Format

Share Document