-
PLoS Genetics Jan 2011During cell division, the spindle checkpoint ensures accurate chromosome segregation by monitoring the kinetochore-microtubule interaction and delaying the onset of...
During cell division, the spindle checkpoint ensures accurate chromosome segregation by monitoring the kinetochore-microtubule interaction and delaying the onset of anaphase until each pair of sister chromosomes is properly attached to microtubules. The spindle checkpoint is deactivated as chromosomes start moving toward the spindles in anaphase, but the mechanisms by which this deactivation and adaptation to prolonged mitotic arrest occur remain obscure. Our results strongly suggest that Cdc28-mediated phosphorylation of Bub1 at T566 plays an important role for the degradation of Bub1 in anaphase, and the phosphorylation is required for adaptation of the spindle checkpoint to prolonged mitotic arrest.
Topics: Anaphase; CDC28 Protein Kinase, S cerevisiae; Chromosome Segregation; G1 Phase; Genes, cdc; Kinetochores; Microtubules; Mitosis; Phosphorylation; Protein Serine-Threonine Kinases; S Phase; Saccharomyces cerevisiae; Spindle Apparatus; Threonine
PubMed: 21298086
DOI: 10.1371/journal.pgen.1001282 -
Cell Reports Aug 2022Chromosome alignment at the spindle equator promotes proper chromosome segregation and depends on pulling forces exerted at kinetochore fiber tips together with polar...
Chromosome alignment at the spindle equator promotes proper chromosome segregation and depends on pulling forces exerted at kinetochore fiber tips together with polar ejection forces. However, kinetochore fibers are also subjected to forces driving their poleward flux. Here we introduce a flux-driven centering model that relies on flux generated by forces within the overlaps of bridging and kinetochore fibers. This centering mechanism works so that the longer kinetochore fiber fluxes faster than the shorter one, moving the kinetochores toward the center. We develop speckle microscopy in human spindles and confirm the key prediction that kinetochore fiber flux is length dependent. Kinetochores are better centered when overlaps are shorter and the kinetochore fiber flux slower than the bridging fiber flux. We identify Kif18A and Kif4A as overlap and flux regulators and NuMA as a fiber coupler. Thus, length-dependent sliding forces exerted by the bridging fiber onto kinetochore fibers support chromosome alignment.
Topics: Anaphase; Cell Cycle Proteins; Chromosome Segregation; Chromosomes; Humans; Kinesins; Kinetochores; Metaphase; Microtubules; Spindle Apparatus
PubMed: 35926461
DOI: 10.1016/j.celrep.2022.111169 -
Proceedings of the National Academy of... Nov 2022How cells adjust their growth to the spatial and mechanical constraints of their surrounding environment is central to many aspects of biology. Here, we examined how...
How cells adjust their growth to the spatial and mechanical constraints of their surrounding environment is central to many aspects of biology. Here, we examined how extracellular matrix (ECM) rigidity affects cell division. We found that cells divide more rapidly when cultured on rigid substrates. While we observed no effect of ECM rigidity on rounding or postmitotic spreading duration, we found that changes in matrix stiffness impact mitosis progression. We noticed that ECM elasticity up-regulates the expression of the linker of nucleoskeleton and cytoskeleton (LINC) complex component SUN2, which in turn promotes metaphase-to-anaphase transition by acting on mitotic spindle formation, whereas when cells adhere to soft ECM, low levels of SUN2 expression perturb astral microtubule organization and delay the onset of anaphase.
Topics: Nuclear Matrix; Cytoskeleton; Microtubules; Mitosis; Extracellular Matrix; Spindle Apparatus; Anaphase
PubMed: 36322767
DOI: 10.1073/pnas.2116167119 -
EMBO Reports Jun 2001The final irreversible step in the duplication and distribution of genomes to daughter cells takes place at the metaphase to anaphase transition. At this point aligned... (Review)
Review
The final irreversible step in the duplication and distribution of genomes to daughter cells takes place at the metaphase to anaphase transition. At this point aligned sister chromatid pairs split and separate. During metaphase, cohesion between sister chromatids is maintained by the chromosomal multi-subunit cohesin complex. Here, I review recent findings as to how anaphase is initiated by proteolytic cleavage of the Scc1 subunit of cohesin. Scc1 is cleaved by a site-specific protease that is conserved in all eukaryotes, and is now called 'separase'. As a result of this cleavage, the cohesin complex is destroyed, allowing the spindle to pull sister chromatids into opposite halves of the cell. Because of the final and irreversible nature of Scc1 cleavage, this reaction is tightly controlled. Several independent mechanisms seem to impose regulation on Scc1 cleavage, acting on both the activity of separase and the susceptibility of the substrate.
Topics: Anaphase; Animals; Binding Sites; Cell Cycle Proteins; Chromosomal Proteins, Non-Histone; Chromosomes; Fungal Proteins; Metaphase; Nuclear Proteins; Phosphoproteins; Saccharomyces cerevisiae Proteins; Cohesins
PubMed: 11415980
DOI: 10.1093/embo-reports/kve113 -
Cytoskeleton (Hoboken, N.J.) Nov 2012Vesicle trafficking and new membrane addition at the cleavage furrow have been extensively documented. However, less clear is the old idea that expansion at the cell...
Vesicle trafficking and new membrane addition at the cleavage furrow have been extensively documented. However, less clear is the old idea that expansion at the cell poles occurs during cytokinesis. We find that new membrane is added to the cell poles during anaphase, causing the plasma membrane to expand coincident with the constriction of the contractile ring and may provide a pushing force for membrane ingression at the furrow. This membrane addition occurs earlier during mitosis than membrane addition at the furrow and is dependent on actin and astral microtubules. The membrane that is added at the polar regions is compositionally distinct from the original cell membrane in that it is devoid of GM(1) , a component of lipid rafts. These findings suggest that the growth of the plasma membrane at the cell poles during cell division is not due to stretching as previously thought, but due to the addition of compositionally unique new membrane.
Topics: Anaphase; Animals; Biological Transport, Active; Cytokinesis; G(M1) Ganglioside; Intracellular Membranes; Lytechinus; Membrane Microdomains
PubMed: 23027735
DOI: 10.1002/cm.21078 -
Developmental Cell Aug 2021Chromosome segregation errors that cause oocyte aneuploidy increase in frequency with maternal age and are considered a major contributing factor of age-related...
Chromosome segregation errors that cause oocyte aneuploidy increase in frequency with maternal age and are considered a major contributing factor of age-related fertility decline in females. Lagging anaphase chromosomes are a common age-associated phenomenon in oocytes, but whether anaphase laggards actually missegregate and cause aneuploidy is unclear. Here, we show that lagging chromosomes in mouse oocytes comprise two mechanistically distinct classes of chromosome motion that we refer to as "class-I" and "class-II" laggards. We use imaging approaches and mechanistic interventions to dissociate the two classes and find that whereas class-II laggards are largely benign, class-I laggards frequently directly lead to aneuploidy. Most notably, a controlled prolongation of meiosis I specifically lessens class-I lagging to prevent aneuploidy. Our data thus reveal lagging chromosomes to be a cause of age-related aneuploidy in mouse oocytes and suggest that manipulating the cell cycle could increase the yield of useful oocytes in some contexts.
Topics: Anaphase; Aneuploidy; Animals; Chromosome Segregation; Female; Mice; Oocytes
PubMed: 34428397
DOI: 10.1016/j.devcel.2021.07.022 -
ELife Mar 2022During anaphase B, molecular motors slide interpolar microtubules to elongate the mitotic spindle, contributing to the separation of chromosomes. However, sliding of...
During anaphase B, molecular motors slide interpolar microtubules to elongate the mitotic spindle, contributing to the separation of chromosomes. However, sliding of antiparallel microtubules reduces their overlap, which may lead to spindle breakage, unless microtubules grow to compensate sliding. How sliding and growth are coordinated is still poorly understood. In this study, we have used the fission yeast to measure microtubule dynamics during anaphase B. We report that the coordination of microtubule growth and sliding relies on promoting rescues at the midzone edges. This makes microtubules stable from pole to midzone, while their distal parts including the plus ends alternate between assembly and disassembly. Consequently, the midzone keeps a constant length throughout anaphase, enabling sustained sliding without the need for a precise regulation of microtubule growth speed. Additionally, we found that in , which undergoes closed mitosis, microtubule growth speed decreases when the nuclear membrane wraps around the spindle midzone.
Topics: Anaphase; Microtubules; Mitosis; Schizosaccharomyces; Spindle Apparatus
PubMed: 35293864
DOI: 10.7554/eLife.72630 -
The Journal of Cell Biology Feb 2019Aurora kinases create phosphorylation gradients within the spindle during prometaphase and anaphase, thereby locally regulating factors that promote spindle...
Aurora kinases create phosphorylation gradients within the spindle during prometaphase and anaphase, thereby locally regulating factors that promote spindle organization, chromosome condensation and movement, and cytokinesis. We show that one such factor is the kinesin KIF4A, which is present along the chromosome axes throughout mitosis and the central spindle in anaphase. These two pools of KIF4A depend on condensin I and PRC1, respectively. Previous work has shown KIF4A is activated by Aurora B at the anaphase central spindle. However, whether or not chromosome-associated KIF4A bound to condensin I is regulated by Aurora kinases remain unclear. To determine the roles of the two different pools of KIF4A, we generated specific point mutants that are unable to interact with either condensin I or PRC1 or are deficient for Aurora kinase regulation. By analyzing these mutants, we show that Aurora A phosphorylates the condensin I-dependent pool of KIF4A and thus actively promotes chromosome congression from the spindle poles to the metaphase plate.
Topics: Adenosine Triphosphatases; Anaphase; Aurora Kinase A; Cell Line; Cell Line, Tumor; Chromosome Positioning; Chromosome Segregation; Chromosomes; DNA-Binding Proteins; HEK293 Cells; HeLa Cells; Humans; Kinesins; Microtubules; Mitosis; Multiprotein Complexes; Phosphorylation; Spindle Apparatus
PubMed: 31881080
DOI: 10.1083/jcb.201905194 -
The Journal of Cell Biology Nov 1995We have quantitatively studied the dynamic behavior of kinetochore fiber microtubules (kMTs); both turnover and poleward transport (flux) in metaphase and anaphase...
We have quantitatively studied the dynamic behavior of kinetochore fiber microtubules (kMTs); both turnover and poleward transport (flux) in metaphase and anaphase mammalian cells by fluorescence photoactivation. Tubulin derivatized with photoactivatable fluorescein was microinjected into prometaphase LLC-PK and PtK1 cells and allowed to incorporate to steady-state. A fluorescent bar was generated across the MTs in a half-spindle of the mitotic cells using laser irradiation and the kinetics of fluorescence redistribution were determined in terms of a double exponential decay process. The movement of the activated zone was also measured along with chromosome movement and spindle elongation. To investigate the possible regulation of MT transport at the metaphase-anaphase transition, we performed double photoactivation analyses on the same spindles as the cell advanced from metaphase to anaphase. We determined values for the turnover of kMTs (t1/2 = 7.1 +/- 2.4 min at 30 degrees C) and demonstrated that the turnover of kMTs in metaphase is approximately an order of magnitude slower than that for non-kMTs. In anaphase, kMTs become dramatically more stable as evidenced by a fivefold increase in the fluorescence redistribution half-time (t1/2 = 37.5 +/- 8.5 min at 30 degrees C). Our results also indicate that MT transport slows abruptly at anaphase onset to one-half the metaphase value. In early anaphase, MT depolymerization at the kinetochore accounted, on average, for 84% of the rate of chromosome movement toward the pole whereas the relative contribution of MT transport and depolymerization at the pole contributed 16%. These properties reflect a dramatic shift in the dynamic behavior of kMTs at the metaphase-anaphase transition. A release-capture model is presented in which the stability of kMTs is increased at the onset of anaphase through a reduction in the probability of MT release from the kinetochore. The reduction in MT transport at the metaphase-anaphase transition suggests that motor activity and/or subunit dynamics at the centrosome are subject to modulation at this key cell cycle point.
Topics: Anaphase; Animals; Cell Cycle; Cell Line; Kidney Tubules, Proximal; Kinetochores; Metaphase; Microtubules; Photochemistry; Spindle Apparatus; Swine; Temperature; Time Factors; Tubulin
PubMed: 7593192
DOI: 10.1083/jcb.131.3.721 -
Current Biology : CB Dec 2005In animal cells, microtubules (MTs) of the mitotic apparatus (MA) communicate with the cell cortex to stimulate cytokinesis; however, the molecular nature of this... (Comparative Study)
Comparative Study
In animal cells, microtubules (MTs) of the mitotic apparatus (MA) communicate with the cell cortex to stimulate cytokinesis; however, the molecular nature of this stimulus remains elusive . A signal for cytokinesis likely involves the MT plus end binding family of proteins, which includes EB1, p150glued, APC, LIS1, and CLIP-170. These proteins modulate MT dynamics and facilitate interactions between growing MTs and their intracellular targets, including kinetochores, organelles, and the cell cortex . The dynein-dynactin complex mediates many of these microtubule capture events . We report that EB1 and p150glued interactions are required for stimulation of cytokinesis in dividing sea urchin eggs. Injected antibodies against EB1 or p150glued suppressed furrow ingression but did not prevent elongation of anaphase astral MTs toward the cortex, suggesting that EB1 and dynactin are both required for communication between the MA and the cortex. Targeted disruption of the interaction between EB1 and p150glued suppressed anaphase astral MT elongation and resulted in a delay of cytokinesis that could not be overcome by manipulation of the asters toward the cortex. We conclude that EB1 and dynactin participate in stimulation of the cleavage furrow, and their interaction promotes elongation of astral MTs at anaphase onset.
Topics: Anaphase; Animals; Blotting, Western; Cytokinesis; Dynactin Complex; Fluorescent Antibody Technique; Immunoprecipitation; Microscopy, Fluorescence; Microtubule-Associated Proteins; Microtubules; Ovum; Sea Urchins
PubMed: 16360686
DOI: 10.1016/j.cub.2005.10.073