scholarly journals Chromosomes function as a barrier to mitotic spindle bipolarity in polyploid cells

2019 ◽  
Author(s):  
Alix Goupil ◽  
Maddalena Nano ◽  
Gaëlle Letort ◽  
Delphine Gogendeau ◽  
Carole Pennetier ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Animal Cells ◽  
Whole Genome Duplications ◽  
Abnormal Mitosis ◽  
Polyploid Cells ◽  
Genome Duplications ◽  
A Cell ◽  
Underlying Mechanisms ◽  
Early Mitosis

AbstractWhole genome duplications (WGDs) are found in a variety of tumors and are associated with chromosomal instability (CIN) and poor prognosis [1,2]. When induced experimentally, through cytokinesis failure, polyploid cells generate tumors [3]. Cytokinesis failure results in the accumulation of double DNA content, but also of cytoplasmic organelles, such as centrosomes, which are the major microtubule (MT) organizing centers of animal cells. Importantly, even if there is a correlation between polyploidy and CIN [4], the underlying mechanisms generating error-prone mitosis in cells with extra DNA and extra centrosomes are not known. When considering polyploid mitosis, it is essential to take into account the increase in MT nucleation due to the presence of extra centrosomes and extra DNA. The presence of supernumerary centrosomes in a cell, centrosome amplification [5], is associated with mitotic spindle multipolarity and CIN [6–9]. Importantly, additional MTs can be nucleated from the chromatin (chromatin mediated pathway-CMP) or from pre-existing MTs-through the Augmin pathway. We hypothesized that the increase in DNA and centrosome content in a cell could lead to an increased MT mass, which might account for abnormal mitosis described in polyploid cells [4, 10, 11, 12]. Using genetics, live imaging and modeling approaches, we investigated the mechanisms establishing multipolarity in vivo in polyploid cells. We found that MT nucleation from the centrosomes is the major contributor to multipolarity, while other pathways seem to play minor roles. Unexpectedly, we found that even if Ncd/HSET, plays an essential role in promoting centrosome clustering in early mitosis, the increase in chromosome mass associated with cytokinesis failure functions as a barrier to centrosome clustering into two main poles. Our work provides a mechanistic link between polyploidy and the generation of CIN.

Regulation of Mitosis

1969 ◽  
Vol 5 (3) ◽  
pp. 745-755
Author(s):  
W. T. JACKSON
Keyword(s):  
Mitotic Spindle ◽  
Time Lapse ◽  
Polarization Microscopy ◽  
Animal Cells ◽  
Higher Plant ◽  
Competitive Antagonism ◽  
Dividing Cells ◽  
Spindle Microtubules ◽  
Giant Nuclei

Earlier studies on the effects of the herbicide isopropyl N-phenylcarbamate (IPC) on mitosis revealed blocked metaphases, multinucleate cells, giant nuclei and an increase in number of partly contracted chromosomes. It was assumed that IPC, like colchicine, was causing these effects by disruption of the spindle apparatus by destroying the spindle microtubules. The animal hormone melatonin causes an increase in birefringence of the mitotic spindle in animal cells, presumably by increasing the number of microtubules. We have studied the effects of IPC, melatonin, and combinations of the two on mitosis in dividing endosperm cells of the African blood lily (Haemanthus katherinae Baker) in vivo by phase-contrast and polarization microscopy. Both qualitative and quantitative data are presented. Interpretation of these results has been aided materially by a time-lapse cinemicrographic analysis of dividing cells subjected to 1 and 10 p.p.m. IPC (unpublished) and by an accompanying fine-structural analysis of untreated and IPC-treated cells. Mitosis was disrupted by 0.01-10 p.p.m. IPC, the severity of the effect depending on both concentration and stage of mitosis of the cell at the time of treatment. Concentrations of IPC that caused cessation of chromosome movement also caused loss of birefringence of the mitotic spindle. Melatonin increased birefringence of the mitotic spindle in these plant cells and partly nullified the adverse effects of IPC. The results of this study demonstrate that the herbicide IPC, under our conditions, causes disruption of mitosis and loss of birefringence of the spindle. And it has been established that an animal hormone is capable of increasing the birefringence, and presumably the number of microtubules, of the mitotic spindle in dividing endosperm cells of a higher plant. Although melatonin is capable of partly nullifying the effects of IPC, a competitive antagonism is not postulated.

scholarly journals SUMO proteases SENP3 and SENP5 spatiotemporally regulate the kinase activity of Aurora A

2021 ◽  
Author(s):  
Bin Yu ◽  
Qiaoyu Lin ◽  
Chao Huang ◽  
Boyan Zhang ◽  
Ying Wang ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Kinase Activity ◽  
In Vitro Assays ◽  
Aurora A ◽  
Sumo Proteases ◽  
Spatiotemporal Control ◽  
Early Mitosis

Precise chromosome segregation is mediated by a well-assembled mitotic spindle, which requires balance of the kinase activity of Aurora A (AurA). However, how this kinase activity is regulated remains largely unclear. Here, using in vivo and in vitro assays, we report that conjugation of SUMO2 with AurA at K258 in early mitosis promotes the kinase activity of AurA and facilitates the binding with its activator, Bora. Knockdown of the SUMO proteases SENP3 and SENP5 disrupted the deSUMOylation of AurA, leading to an increased kinase activity and abnormalities in spindle assembly and chromosomes segregation which could be rescued by suppressing the kinase activity of AurA. Collectively, these results demonstrate that SENP3 and SENP5 deSUMOylate AurA to render a spatiotemporal control on its kinase activity in mitosis.

Microtubule dynamics in the mitotic spindle

1987 ◽  
Vol 45 ◽  
pp. 794-797
Author(s):  
J. Richard McIntosh ◽  
Guy P. A. Vigers
Keyword(s):  
Mitotic Spindle ◽  
Living Cell ◽  
Mitotic Cell ◽  
Tubulin Polymerization ◽  
Half Time ◽  
Laser Microbeam ◽  
A Cell ◽  
Spindle Microtubules ◽  
Lines Of Evidence

Six lines of evidence suggest that the mitotic spindle is highly labile in vivo: the spindle forms for division and disassembles as it finishes its job; the spindle dissolves under most conditions of cell lysis; the spindle disappears when a living cell is treated with temperatures near 0°C or high hydrostatic pressure; the spindle quickly disassembles when drugs that block tubulin polymerization are put on or injected into a cell; labeled tubulin, injected into a mitotic cell, is incorporated into the spindle within seconds of injection; and the spindle of a living cell, equilibrated with injected fluorescent tubulin, may be photobleached with a laser microbeam, and the spindle fluorescence redistributes with a half time of 15 - 20 sec. These data suggest that spindle microtubules (MTs) are in rapidly exchanging equilibrium with a pool of soluble tubulin subunits (Reviewed in 1 - 3).

scholarly journals The 110-kD spindle pole body component of Saccharomyces cerevisiae is a phosphoprotein that is modified in a cell cycle-dependent manner.

1996 ◽  
Vol 132 (5) ◽  
pp. 903-914 ◽  
Author(s):  
D B Friedman ◽  
H A Sundberg ◽  
E Y Huang ◽  
T N Davis
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Wild Type ◽  
Spindle Formation ◽  
Pole Body ◽  
A Cell ◽  
In Cells

Spc110p (Nuf1p) is an essential component of the yeast microtubule organizing center, or spindle pole body (SPB). Asynchronous wild-type cultures contain two electrophoretically distinct isoforms of Spc110p as detected by Western blot analysis, suggesting that Spc110p is modified in vivo. Both isoforms incorporate 32Pi in vivo, suggesting that Spc110p is post-translationally modified by phosphorylation. The slower-migrating 120-kD Spc110p isoform after incubation is converted to the faster-migrating 112-kD isoform after incubation with protein phosphatase PP2A, and specific PP2A inhibitors block this conversion. Thus, additional phosphorylation of Spc110p at serine and/or threonine residues gives rise to the slower-migrating 120-kD isoform. The 120-kD isoform predominates in cells arrested in mitosis by the addition of nocodazole. However, the 120-kD isoform is not detectable in cells grown to stationary phase (G0) or in cells arrested in G1 by the addition of alpha-factor. Temperature-sensitive cell division cycle (cdc) mutations demonstrate that the presence of the 120-kD isoform correlates with mitotic spindle formation but not with SPB duplication. In a synchronous wild-type population, the additional serine/threonine phosphorylation that gives rise to the 120-kD isoform appears as cells are forming the mitotic spindle and diminishes as cells enter anaphase. None of several sequences similar to the consensus for phosphorylation by the Cdc28p (cdc2p34) kinase is important for these mitosis-specific phosphorylations or for function. Carboxy-terminal Spc110p truncations lacking the calmodulin binding site can support growth and are also phosphorylated in a cell cycle-specific manner. Further truncation of the Spc110p carboxy terminus results in mutant proteins that are unable to support growth and now migrate as single species. Collectively, these results provide the first evidence of a structural component of the SPB that is phosphorylated during spindle formation and dephosphorylated as cells enter anaphase.

scholarly journals Structural activation of Mad2 in the mitotic spindle checkpoint: the two-state Mad2 model versus the Mad2 template model

2006 ◽  
Vol 173 (2) ◽  
pp. 153-157 ◽  
Author(s):  
Hongtao Yu
Keyword(s):  
Mitotic Spindle ◽  
Spindle Checkpoint ◽  
Biological Data ◽  
Anaphase Promoting Complex ◽  
Mitotic Spindle Checkpoint ◽  
Ubiquitin Ligase Activity ◽  
Large Conformational Change ◽  
A Cell ◽  
Model Versus

The inheritance of a normal assortment of chromosomes during each cell division relies on a cell-cycle surveillance system called the mitotic spindle checkpoint. The existence of sister chromatids that do not achieve proper bipolar attachment to the mitotic spindle in a cell activates this checkpoint, which inhibits the ubiquitin ligase activity of the anaphase-promoting complex or cyclosome (APC/C) and delays the onset of anaphase. The mitotic arrest deficiency 2 (Mad2) spindle checkpoint protein inhibits APC/C through binding to its mitotic-specific activator, Cdc20. Binding of Mad2 to Cdc20 involves a large conformational change of Mad2 and requires the Mad1–Mad2 interaction in vivo. Two related but distinct models of Mad1-assisted activation of Mad2, the “two-state Mad2” and the “Mad2 template” models, have been proposed. I review the recent structural, biochemical, and cell biological data on Mad2, discuss the differences between the two models, and propose experiments that test their key principles.

scholarly journals Co-translational protein targeting facilitates centrosomal recruitment of PCNT during centrosome maturation in vertebrates

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Guadalupe Sepulveda ◽  
Mark Antkowiak ◽  
Ingrid Brust-Mascher ◽  
Karan Mahe ◽  
Tingyoung Ou ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Protein Targeting ◽  
Mrna Localization ◽  
Cytoplasmic Dynein ◽  
Animal Cells ◽  
Bipolar Spindle ◽  
Spindle Poles ◽  
Cytoplasmic Proteins ◽  
Pericentriolar Material ◽  
Early Mitosis

As microtubule-organizing centers of animal cells, centrosomes guide the formation of the bipolar spindle that segregates chromosomes during mitosis. At mitosis onset, centrosomes maximize microtubule-organizing activity by rapidly expanding the pericentriolar material (PCM). This process is in part driven by the large PCM protein pericentrin (PCNT), as its level increases at the PCM and helps recruit additional PCM components. However, the mechanism underlying the timely centrosomal enrichment of PCNT remains unclear. Here, we show that PCNT is delivered co-translationally to centrosomes during early mitosis by cytoplasmic dynein, as evidenced by centrosomal enrichment of PCNT mRNA, its translation near centrosomes, and requirement of intact polysomes for PCNT mRNA localization. Additionally, the microtubule minus-end regulator, ASPM, is also targeted co-translationally to mitotic spindle poles. Together, these findings suggest that co-translational targeting of cytoplasmic proteins to specific subcellular destinations may be a generalized protein targeting mechanism.

scholarly journals Effect of aspirin on tumour cell colony formation and evolution

2017 ◽  
Vol 14 (134) ◽  
pp. 20170374 ◽  
Author(s):  
Dominik Wodarz ◽  
Ajay Goel ◽  
C. Richard Boland ◽  
Natalia L. Komarova
Keyword(s):  
Cell Lines ◽  
Cell Population ◽  
Tumour Cell ◽  
Evolutionary Potential ◽  
A Cell ◽  
Tumour Cell Lines ◽  
Underlying Mechanisms ◽  
Cell Colony

Aspirin is known to reduce the risk of colorectal cancer (CRC) incidence, but the underlying mechanisms are not fully understood. In a previous study, we quantified the in vitro growth kinetics of different CRC tumour cell lines treated with varying doses of aspirin, measuring the rate of cell division and cell death. Here, we use these measured parameters to calculate the chances of successful clonal expansion and to determine the evolutionary potential of the tumour cell lines in the presence and absence of aspirin. The calculations indicate that aspirin increases the probability that a single tumour cell fails to clonally expand. Further, calculations suggest that aspirin increases the evolutionary potential of an expanding tumour cell colony. An aspirin-treated tumour cell population is predicted to result in the accumulation of more mutations (and is thus more virulent and more difficult to treat) than a cell population of the same size that grew without aspirin. This indicates a potential trade-off between delaying the onset of cancer and increasing its evolutionary potential through chemoprevention. Further work needs to investigate to what extent these findings apply to in vivo settings, and to what degree they contribute to the epidemiologically documented aspirin-mediated protection.

scholarly journals NuMA is required for the organization of microtubules into aster-like mitotic arrays.

1995 ◽  
Vol 131 (3) ◽  
pp. 693-708 ◽  
Author(s):  
T Gaglio ◽  
A Saredi ◽  
D A Compton
Keyword(s):  
Mitotic Spindle ◽  
Cultured Cells ◽  
Active Role ◽  
Mitotic Apparatus ◽  
Free System ◽  
Cell Free System ◽  
A Cell ◽  
Late Stages ◽  
Temporal Accumulation

NuMA (Nuclear protein that associates with the Mitotic Apparatus) is a 235-kD intranuclear protein that accumulates at the pericentrosomal region of the mitotic spindle in vertebrate cells. To determine if NuMA plays an active role in organizing the microtubules at the polar region of the mitotic spindle, we have developed a cell free system for the assembly of mitotic asters derived from synchronized cultured cells. Mitotic asters assembled in this extract are composed of microtubules arranged in a radial array that contain NuMA concentrated at the central core. The organization of microtubules into asters in this cell free system is dependent on NuMA because immunodepletion of NuMA from the extract results in randomly dispersed microtubules instead of organized mitotic asters, and addition of the purified recombinant NuMA protein to the NuMA-depleted extract fully reconstitutes the organization of the microtubules into mitotic asters. Furthermore, we show that NuMA is phosphorylated upon mitotic aster assembly and that NuMA is only required in the late stages of aster assembly in this cell free system consistent with the temporal accumulation of NuMA at the polar ends of the mitotic spindle in vivo. These results, in combination with the phenotype observed in vivo after the prevention of NuMA from targeting onto the mitotic spindle by antibody microinjection, suggest that NuMA plays a functional role in the organization of the microtubules of the mitotic spindle.

scholarly journals Autophagy as a modulator of cell death machinery

2020 ◽  
Vol 11 (7) ◽  
Author(s):  
Masayuki Noguchi ◽  
Noriyuki Hirata ◽  
Tsutomu Tanaka ◽  
Futoshi Suizu ◽  
Hiroshi Nakajima ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Mammalian Cells ◽  
Critical Parameter ◽  
Type I ◽  
Type Ii ◽  
Critical Question ◽  
A Cell ◽  
Underlying Mechanisms

Abstract The balance between cell death and survival is a critical parameter in the regulation of cells and the maintenance of homeostasis in vivo. Three major mechanisms for cell death have been identified in mammalian cells: apoptosis (type I), autophagic cell death (type II), and necrosis (type III). These three mechanisms have been suggested to engage in cross talk with each other. Among them, autophagy was originally characterized as a cell survival mechanism for amino acid recycling during starvation. Whether autophagy functions primarily in cell survival or cell death is a critical question yet to be answered. Here, we present a comprehensive review of the cell death-related events that take place during autophagy and their underlying mechanisms in cancer and autoimmune disease development.

scholarly journals Co-translational protein targeting facilitates centrosomal recruitment of PCNT during centrosome maturation

2017 ◽  
Author(s):  
Guadalupe Sepulveda ◽  
Mark Antkowiak ◽  
Ingrid Brust-Mascher ◽  
Karan Mahe ◽  
Tingyoung Ou ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Protein Targeting ◽  
Mrna Localization ◽  
Cytoplasmic Dynein ◽  
Animal Cells ◽  
Bipolar Spindle ◽  
Spindle Poles ◽  
Cytoplasmic Proteins ◽  
Pericentriolar Material ◽  
Early Mitosis

AbstractAs microtubule-organizing centers of animal cells, centrosomes guide the formation of the bipolar spindle that segregates chromosomes during mitosis. At mitosis onset, centrosomes maximize microtubule-organizing activity by rapidly expanding the pericentriolar material (PCM). This process is in part driven by the large PCM protein pericentrin (PCNT), as its level increases at the PCM and helps recruit additional PCM components. However, the mechanism underlying the timely centrosomal enrichment of PCNT remains unclear. Here we show that PCNT is delivered co-translationally to centrosomes during early mitosis by cytoplasmic dynein, as evidenced by centrosomal enrichment of PCNT mRNA, its translation near the centrosome, and requirement of intact polysomes for PCNT mRNA localization. Additionally, the microtubule minus-end regulator, ASPM, is also targeted co-translationally to mitotic spindle poles. Together, these findings suggest that co-translational targeting of cytoplasmic proteins to specific subcellular destinations may be a generalized protein targeting mechanism.

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