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Biochemical Society Transactions Jun 2008Cytokinesis is a dynamic and plastic process involving the co-ordinated regulation of many components. Accordingly, many proteins, including the putative scaffold... (Review)
Review
Cytokinesis is a dynamic and plastic process involving the co-ordinated regulation of many components. Accordingly, many proteins, including the putative scaffold protein anillin, localize to the cleavage furrow and are required for cytokinesis, but how they function together is poorly understood. Anillin can bind to numerous other furrow components, including F-actin, septins and myosin II, but its molecular functions are unclear. Recent data suggest that anillin participates in a previously unrecognized Rho-dependent pathway that can promote the association of anillin with the plasma membrane, septins, myosin II and microtubules. Studies using the inhibitor of F-actin assembly, Lat A (Latrunculin A), have revealed that these associations occur independently of F-actin; indeed they appear to be stabilized by the loss of F-actin. This pathway may explain previously described requirements for anillin in maintaining stable furrow positioning and for forming a stable midbody, and supports the notion that anillin is a central organizer at the hub of the cytokinetic machinery.
Topics: Anaphase; Animals; Contractile Proteins; Cytokinesis; Humans; Protein Binding; Spindle Apparatus; rho GTP-Binding Proteins
PubMed: 18481976
DOI: 10.1042/BST0360439 -
Bioinformatics (Oxford, England) Jun 2022Lattice light-sheet microscopy (LLSM) is revolutionizing cell biology since it enables fast, high-resolution extended imaging in three dimensions combined with a drastic...
MOTIVATION
Lattice light-sheet microscopy (LLSM) is revolutionizing cell biology since it enables fast, high-resolution extended imaging in three dimensions combined with a drastic reduction in photo-toxicity and bleaching. However, analysis of such datasets still remains a major challenge.
RESULTS
Automated tracking of kinetochores, the protein complex facilitating and controlling microtubule attachment of the chromosomes within the mitotic spindle, provides quantitative assessment of chromosome dynamics in mitosis. Here, we extend existing open-source kinetochore tracking software (KiT) to track (and pair) kinetochores throughout prometaphase to anaphase in LLSM data. One of the key improvements is a regularization term in the objective function to enforce biological information about the number of kinetochores in a human mitotic cell, as well as improved diagnostic tools. This software provides quantitative insights into how kinetochores robustly ensure congression and segregation of chromosomes during mitosis.
AVAILABILITY AND IMPLEMENTATION
KiT is free, open-source software implemented in MATLAB and can be downloaded as a package from https://github.com/cmcb-warwick/KiT. The source repository is available at https://bitbucket.org/jarmond/kit (tag v2.4.0) and under continuing development.
SUPPLEMENTARY INFORMATION
Supplementary data are available at Bioinformatics online.
Topics: Humans; Kinetochores; Spindle Apparatus; Anaphase; Microtubules; Software; Chromosome Segregation
PubMed: 35579370
DOI: 10.1093/bioinformatics/btac330 -
Cell Cycle (Georgetown, Tex.) Oct 2021To ensure genome stability, chromosomes need to undergo proper condensation into two linked sister chromatids from prophase to prometaphase, followed by equal...
To ensure genome stability, chromosomes need to undergo proper condensation into two linked sister chromatids from prophase to prometaphase, followed by equal segregation at anaphase. Emerging evidence has shown that persistent DNA entanglements connecting the sister chromatids lead to the formation of ultrafine anaphase bridges (UFBs). If UFBs are not resolved soon after anaphase, they can induce chromosome missegregation. PICH (PLK1-interacting checkpoint helicase) is a DNA translocase that localizes on chromosome arms, centromeres and UFBs. It plays multiple essential roles in mitotic chromosome organization and segregation. PICH also recruits other associated proteins to UFBs, and together they mediate UFB resolution. Here, the proposed mechanism behind PICH's functions in chromosome organization and UFB resolution will be discussed. We summarize the regulation of PICH action at chromosome arms and centromeres, how PICH recognizes UFBs and recruits other UFB-associated factors, and finally how PICH promotes UFB resolution together with other DNA processing enzymes.
Topics: Anaphase; Centromere; Chromatids; Chromosome Segregation; Genomic Instability; Humans; Mitosis
PubMed: 34530686
DOI: 10.1080/15384101.2021.1970877 -
Nucleus (Austin, Tex.) Mar 2012Coordination of late mitotic events is crucial for the maintenance of genome stability and for the control of gene expression after cell division. Reversible protein... (Review)
Review
Coordination of late mitotic events is crucial for the maintenance of genome stability and for the control of gene expression after cell division. Reversible protein phosphorylation regulates this process by de-phosphorylation of mitotic phospho-proteins in a sequential and coordinated manner: this allows an orderly sequence of events to take place during mitotic exit. We have identified Repo-Man/PP1 as a phosphatase complex that regulates temporally and spatially chromatin re-organization and nuclear envelope re-formation during anaphase-telophase.
Topics: Anaphase; Chromatin Assembly and Disassembly; Nuclear Envelope; Nuclear Proteins; Protein Phosphatase 1; Telophase
PubMed: 22555598
DOI: 10.4161/nucl.19267 -
Cellular and Molecular Life Sciences :... Jul 2010One of the most extraordinary events in the lifetime of a cell is the coordinated separation of sister chromatids during cell division. This is truly the essence of the... (Review)
Review
One of the most extraordinary events in the lifetime of a cell is the coordinated separation of sister chromatids during cell division. This is truly the essence of the entire mitotic process and the reason for the most profound morphological changes in cytoskeleton and nuclear organization that a cell may ever experience. It all occurs within a very short time window known as "anaphase", as if the cell had spent the rest of its existence getting ready for this moment in an ultimate act of survival. And there is a good reason for this: no space for mistakes. Problems in the distribution of chromosomes during cell division have been correlated with aneuploidy, a common feature observed in cancers and several birth defects, and the main cause of spontaneous abortion in humans. In this paper, we critically review the mechanisms of anaphase chromosome motion that resisted the scrutiny of more than 100 years of research, as part of a tribute to the pioneering work of Miguel Mota.
Topics: Anaphase; Animals; Chromatids; Chromosomes; Drosophila; Dyneins; Kinetochores
PubMed: 20306325
DOI: 10.1007/s00018-010-0327-5 -
Nature Communications Sep 2021The RAD51 recombinase plays critical roles in safeguarding genome integrity, which is fundamentally important for all living cells. While interphase functions of RAD51...
The RAD51 recombinase plays critical roles in safeguarding genome integrity, which is fundamentally important for all living cells. While interphase functions of RAD51 in maintaining genome stability are well-characterised, its role in mitosis remains contentious. In this study, we show that RAD51 protects under-replicated DNA in mitotic human cells and, in this way, promotes mitotic DNA synthesis (MiDAS) and successful chromosome segregation. In cells experiencing mild replication stress, MiDAS was detected irrespective of mitotically generated DNA damage. MiDAS broadly required de novo RAD51 recruitment to single-stranded DNA, which was supported by the phosphorylation of RAD51 by the key mitotic regulator Polo-like kinase 1. Importantly, acute inhibition of MiDAS delayed anaphase onset and induced centromere fragility, suggesting a mechanism that prevents the satisfaction of the spindle assembly checkpoint while chromosomal replication remains incomplete. This study hence identifies an unexpected function of RAD51 in promoting genomic stability in mitosis.
Topics: Anaphase; Cell Cycle Proteins; Cell Line; Chromatin; Chromosome Segregation; DNA; DNA Damage; DNA Repair; DNA Replication; Genomic Instability; Humans; Intravital Microscopy; M Phase Cell Cycle Checkpoints; Phosphorylation; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Rad51 Recombinase; Polo-Like Kinase 1
PubMed: 34508092
DOI: 10.1038/s41467-021-25643-y -
Molecular Biology of the Cell Jul 2023Cells actively position their nuclei based on their activity. In fission yeast, microtubule-dependent nuclear centering is critical for symmetrical cell division. After...
Cells actively position their nuclei based on their activity. In fission yeast, microtubule-dependent nuclear centering is critical for symmetrical cell division. After spindle disassembly at the end of anaphase, the nucleus recenters over an ∼90-min period, approximately half of the duration of the cell cycle. Live-cell and simulation experiments support the cooperation of two distinct microtubule competition mechanisms in the slow recentering of the nucleus. First, a push-push mechanism acts from spindle disassembly to septation and involves the opposing actions of the mitotic spindle pole body microtubules that push the nucleus away from the ends of the cell, while a postanaphase array of microtubules baskets the nucleus and limits its migration toward the division plane. Second, a slow-and-grow mechanism slowly centers the nucleus in the newborn cell by a combination of microtubule competition and asymmetric cell growth. Our work underlines how intrinsic properties of microtubules differently impact nuclear positioning according to microtubule network organization and cell size.
Topics: Humans; Infant, Newborn; Anaphase; Schizosaccharomyces; Microtubules; Cell Cycle; Cytoskeleton; Cell Nucleus; Spindle Apparatus
PubMed: 37099380
DOI: 10.1091/mbc.E23-01-0034 -
Cytogenetic and Genome Research 2011Mammalian oocytes execute a unique meiotic programme involving 2 arrest stages and an unusually protracted preamble to chromosome segregation during the first meiotic... (Review)
Review
Mammalian oocytes execute a unique meiotic programme involving 2 arrest stages and an unusually protracted preamble to chromosome segregation during the first meiotic division (meiosis I). How mammalian oocytes successfully navigate their exceptional meiotic journey has long been a question of immense interest. Understanding the minutiae of female mammalian meiosis I is not merely of academic interest as 80-90% of human aneuploidy is the consequence of errors arising at this particular stage of oocyte maturation, a stage with a peculiar vulnerability to aging. Recent evidence indicates that oocytes employ many of the same cast of proteins during meiosis I as somatic cells do during mitosis, often to execute similar tasks, but intriguingly, occasionally delegate them to unexpected and unprecedented roles. This is epitomised by the master cell-cycle regulon, the anaphase-promoting complex or cyclosome (APC/C), acting in concert with a critical APC/C-targeted surveillance mechanism, the spindle assembly checkpoint (SAC). Together, the APC/C and the SAC are among the most influential entities overseeing the fidelity of cell-cycle progression and the precision of chromosome segregation. Here I review the current status of pivotal elements underpinning homologue disjunction in mammalian oocytes including spindle assembly, critical biochemical anaphase-initiating events, APC/C activity and SAC signalling along with contemporary findings relevant to progressive oocyte SAC dysfunction as a model for age-related human aneuploidy.
Topics: Anaphase; Anaphase-Promoting Complex-Cyclosome; Animals; Humans; Mammals; Meiosis; Oocytes; Ubiquitin-Protein Ligase Complexes
PubMed: 21335952
DOI: 10.1159/000324118 -
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