-
Environmental Research Oct 2022The present study is an attempt to assess the cytogenotoxic effect of untreated and methyl orange treated with Oedogonium subplagiostomum AP1 on Allium cepa roots. On...
The present study is an attempt to assess the cytogenotoxic effect of untreated and methyl orange treated with Oedogonium subplagiostomum AP1 on Allium cepa roots. On the fifth day, root growth, root length, mitotic index, mitotic inhibition/depression, and chromosomal abnormalities were measured in root cells of Allium cepa subjected to untreated and treated methyl orange dye solutions. Roots exposed to treated dye solution exhibited maximum root growth, root length and mitotic index, whereas roots exposed to untreated dye solution had the most mitotic inhibition and chromosomal abnormalities. Allium cepa exposed to untreated dye solution revealed chromosomal aberrations such as disoriented and abnormal chromosome grouping, vagrant and laggard chromosomes, chromosomal loss, sticky chain and disturbed metaphase, pulverised and disturbed anaphase, chromosomal displacement in anaphase, abnormal telophase, and chromosomal bridge at telophase, spindle disturbances and binucleate cells. The comet test was used to quantify DNA damage in the root cells of A. cepa subjected to untreated and treated methyl orange solutions in terms of tail DNA (percent) and tail length. The results concluded that A. cepa exposed to methyl orange induced DNA damage whereas meager damage was noted in the treated dye solution. As a result, the research can be used as a biomarker to detect the genotoxic effects of textile dyes on biota.
Topics: Allium; Azo Compounds; Chromosome Aberrations; DNA Damage; Mitotic Index; Onions; Plant Roots
PubMed: 35716816
DOI: 10.1016/j.envres.2022.113612 -
Science (New York, N.Y.) Nov 2017Cell division and differentiation depend on massive and rapid organelle remodeling. The mitotic oscillator, centered on the cyclin-dependent kinase 1-anaphase-promoting...
Cell division and differentiation depend on massive and rapid organelle remodeling. The mitotic oscillator, centered on the cyclin-dependent kinase 1-anaphase-promoting complex/cyclosome (CDK1-APC/C) axis, spatiotemporally coordinates this reorganization in dividing cells. Here we discovered that nondividing cells could also implement this mitotic clocklike regulatory circuit to orchestrate subcellular reorganization associated with differentiation. We probed centriole amplification in differentiating mouse-brain multiciliated cells. These postmitotic progenitors fine-tuned mitotic oscillator activity to drive the orderly progression of centriole production, maturation, and motile ciliation while avoiding the mitosis commitment threshold. Insufficient CDK1 activity hindered differentiation, whereas excessive activity accelerated differentiation yet drove postmitotic progenitors into mitosis. Thus, postmitotic cells can redeploy and calibrate the mitotic oscillator to uncouple cytoplasmic from nuclear dynamics for organelle remodeling associated with differentiation.
Topics: Anaphase-Promoting Complex-Cyclosome; Animals; Brain; CDC2 Protein Kinase; Cell Differentiation; Centrioles; Cilia; Mice; Mitosis; Organelles
PubMed: 28982797
DOI: 10.1126/science.aan8311 -
Molecular & Cellular Oncology 2015Equal segregation of sister chromatids during mitosis requires that pairs of kinetochores establish proper attachment to microtubules emanating from opposite poles of... (Review)
Review
Equal segregation of sister chromatids during mitosis requires that pairs of kinetochores establish proper attachment to microtubules emanating from opposite poles of the mitotic spindle. The spindle assembly checkpoint (SAC) protects against errors in segregation by delaying sister separation in response to improper kinetochore-microtubule interactions, and certain checkpoint proteins help to establish proper attachments. Anaphase entry is inhibited by the checkpoint through assembly of the mitotic checkpoint complex (MCC) composed of the 2 checkpoint proteins, Mad2 and BubR1, bound to Cdc20. The outer kinetochore acts as a catalyst for MCC production through the recruitment and proper positioning of checkpoint proteins and recently there has been remarkable progress in understanding how this is achieved. Here, we highlight recent advances in our understanding of kinetochore-checkpoint protein interactions and inhibition of the anaphase promoting complex by the MCC.
PubMed: 27308407
DOI: 10.4161/23723548.2014.970484 -
PLoS Genetics Sep 2022The activated spindle assembly checkpoint (SAC) potently inhibits the anaphase-promoting complex/cyclosome (APC/C) to ensure accurate chromosome segregation at anaphase....
The activated spindle assembly checkpoint (SAC) potently inhibits the anaphase-promoting complex/cyclosome (APC/C) to ensure accurate chromosome segregation at anaphase. Early studies have recognized that the SAC should be silenced within minutes to enable rapid APC/C activation and synchronous segregation of chromosomes once all kinetochores are properly attached, but the underlying silencers are still being elucidated. Here, we report that the timely silencing of SAC in fission yeast requires dnt1+, which causes severe thiabendazole (TBZ) sensitivity and increased rate of lagging chromosomes when deleted. The absence of Dnt1 results in prolonged inhibitory binding of mitotic checkpoint complex (MCC) to APC/C and attenuated protein levels of Slp1Cdc20, consequently slows the degradation of cyclin B and securin, and eventually delays anaphase entry in cells released from SAC activation. Interestingly, Dnt1 physically associates with APC/C upon SAC activation. We propose that this association may fend off excessive and prolonged MCC binding to APC/C and help to maintain Slp1Cdc20 stability. This may allow a subset of APC/C to retain activity, which ensures rapid anaphase onset and mitotic exit once SAC is inactivated. Therefore, our study uncovered a new player in dictating the timing and efficacy of APC/C activation, which is actively required for maintaining cell viability upon recovery from the inhibition of APC/C by spindle checkpoint.
Topics: Anaphase-Promoting Complex-Cyclosome; Cdc20 Proteins; Cell Cycle Proteins; Kinetochores; M Phase Cell Cycle Checkpoints; Securin; Spindle Apparatus; Thiabendazole
PubMed: 36108046
DOI: 10.1371/journal.pgen.1010397 -
Cells Feb 2020Meiosis is required to reduce to haploid the diploid genome content of a cell, generating gametes-oocytes and sperm-with the correct number of chromosomes. To achieve... (Review)
Review
Meiosis is required to reduce to haploid the diploid genome content of a cell, generating gametes-oocytes and sperm-with the correct number of chromosomes. To achieve this goal, two specialized cell divisions without intermediate S-phase are executed in a time-controlled manner. In mammalian female meiosis, these divisions are error-prone. Human oocytes have an exceptionally high error rate that further increases with age, with significant consequences for human fertility. To understand why errors in chromosome segregation occur at such high rates in oocytes, it is essential to understand the molecular players at work controlling these divisions. In this review, we look at the interplay of kinase and phosphatase activities at the transition from metaphase-to-anaphase for correct segregation of chromosomes. We focus on the activity of PP2A-B56, a key phosphatase for anaphase onset in both mitosis and meiosis. We start by introducing multiple roles PP2A-B56 occupies for progression through mitosis, before laying out whether or not the same principles may apply to the first meiotic division in oocytes, and describing the known meiosis-specific roles of PP2A-B56 and discrepancies with mitotic cell cycle regulation.
Topics: Animals; Kinetochores; Meiosis; Mice; Microtubules; Oocytes; Protein Phosphatase 2; Spindle Apparatus
PubMed: 32046180
DOI: 10.3390/cells9020390 -
Molecular Biology of the Cell Sep 2019Spindle microtubules, whose dynamics vary over time and at different locations, cooperatively drive chromosome segregation. Measurements of microtubule dynamics and...
Spindle microtubules, whose dynamics vary over time and at different locations, cooperatively drive chromosome segregation. Measurements of microtubule dynamics and spindle ultrastructure can provide insight into the behaviors of microtubules, helping elucidate the mechanism of chromosome segregation. Much work has focused on the dynamics and organization of kinetochore microtubules, that is, on the region between chromosomes and poles. In comparison, microtubules in the central-spindle region, between segregating chromosomes, have been less thoroughly characterized. Here, we report measurements of the movement of central-spindle microtubules during chromosome segregation in human mitotic spindles and mitotic and female meiotic spindles. We found that these central-spindle microtubules slide apart at the same speed as chromosomes, even as chromosomes move toward spindle poles. In these systems, damaging central-spindle microtubules by laser ablation caused an immediate and complete cessation of chromosome motion, suggesting a strong coupling between central-spindle microtubules and chromosomes. Electron tomographic reconstruction revealed that the analyzed anaphase spindles all contain microtubules with both ends between segregating chromosomes. Our results provide new dynamical, functional, and ultrastructural characterizations of central-spindle microtubules during chromosome segregation in diverse spindles and suggest that central-spindle microtubules and chromosomes are strongly coupled in anaphase.
Topics: Anaphase; Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cell Line, Tumor; Chromosome Segregation; Chromosomes; Humans; Kinetochores; Meiosis; Microtubules; Spindle Apparatus; Spindle Poles
PubMed: 31339442
DOI: 10.1091/mbc.E19-01-0074 -
Cancer Biology & Therapy Dec 2023Cyclin-dependent Kinase 2 (CDK2) inhibition prevents supernumerary centrosome clustering. This causes multipolarity, anaphase catastrophe and apoptotic death of...
Cyclin-dependent Kinase 2 (CDK2) inhibition prevents supernumerary centrosome clustering. This causes multipolarity, anaphase catastrophe and apoptotic death of aneuploid cancers. This study elucidated how CDK2 antagonism affected centrosome stoichiometry. Focused ion beam scanning electron microscopy (FIB-SEM) and immunofluorescent imaging were used. Studies interrogated multipolar mitosis after pharmacologic or genetic repression of CDK2. CDK2/9 antagonism with CYC065 (Fadraciclib)-treatment disordered centrosome stoichiometry in aneuploid cancer cells, preventing centrosome clustering. This caused ring-like chromosomes or multipolar cancer cells to form before onset of cell death. Intriguingly, CDK2 inhibition caused a statistically significant increase in single centrioles rather than intact centrosomes with two centrioles in cancer cells having chromosome rings or multipolarity. Statistically significant alterations in centrosome stoichiometry were undetected in other mitotic cancer cells. To confirm this pharmacodynamic effect, CDK2 but not CDK9 siRNA-mediated knockdown augmented cancer cells with chromosome ring or multipolarity formation. Notably, engineered gain of CDK2, but not CDK9 expression, reversed emergence of cancer cells with chromosome rings or multipolarity, despite CYC065-treatment. In marked contrast, CDK2 inhibition of primary human alveolar epithelial cells did not confer statistically significant increases of cells with ring-like chromosomes or multipolarity. Hence, CDK2 antagonism caused differential effects in malignant versus normal alveolar epithelial cells. Translational relevance was confirmed by CYC065-treatment of syngeneic lung cancers in mice. Mitotic figures in tumors exhibited chromosome rings or multipolarity. Thus, CDK2 inhibition preferentially disorders centrosome stoichiometry in cancer cells. Engaging this disruption is a strategy to explore against aneuploid cancers in future clinical trials.
Topics: Humans; Animals; Mice; Cyclin-Dependent Kinase 2; Centrosome; Anaphase; Mitosis; Aneuploidy; Neoplasms
PubMed: 38031910
DOI: 10.1080/15384047.2023.2279241 -
Trends in Cell Biology Jan 2017The separation of chromosomes in anaphase is a precarious step in the cell cycle. The separation is irreversible, and any error can lead to cell death or genetic... (Review)
Review
The separation of chromosomes in anaphase is a precarious step in the cell cycle. The separation is irreversible, and any error can lead to cell death or genetic instability. Chromosome separation is controlled by the protease separase. Here we discuss recent work that has revealed additional layers of separase regulation and has deepened our understanding of how separase activation is coordinated with other events of mitotic exit.
Topics: Animals; Chromatids; Chromosome Segregation; Humans; Mitosis; Models, Biological; Separase
PubMed: 27567180
DOI: 10.1016/j.tcb.2016.07.008 -
Cell Reports Jun 2018A common assumption is that human chromosomes carry equal chances of mis-segregation during compromised cell division. Human chromosomes vary in multiple parameters that...
A common assumption is that human chromosomes carry equal chances of mis-segregation during compromised cell division. Human chromosomes vary in multiple parameters that might generate bias, but technological limitations have precluded a comprehensive analysis of chromosome-specific aneuploidy. Here, by imaging specific centromeres coupled with high-throughput single-cell analysis as well as single-cell sequencing, we show that aneuploidy occurs non-randomly following common treatments to elevate chromosome mis-segregation. Temporary spindle disruption leads to elevated mis-segregation and aneuploidy of a subset of chromosomes, particularly affecting chromosomes 1 and 2. Unexpectedly, we find that a period of mitotic delay weakens centromeric cohesion and promotes chromosome mis-segregation and that chromosomes 1 and 2 are particularly prone to suffer cohesion fatigue. Our findings demonstrate that inherent properties of individual chromosomes can bias chromosome mis-segregation and aneuploidy rates, with implications for studies on aneuploidy in human disease.
Topics: Anaphase; Aneuploidy; Carrier Proteins; Cell Line, Tumor; Chromosome Segregation; Chromosomes, Human; Humans; In Situ Hybridization, Fluorescence; Kinetochores; Nocodazole; Nuclear Proteins; Proto-Oncogene Proteins; RNA Interference; RNA, Small Interfering; Single-Cell Analysis
PubMed: 29898405
DOI: 10.1016/j.celrep.2018.05.047 -
Cell Cycle (Georgetown, Tex.) 2019The Anaphase-Promoting Complex/Cyclosome (APC/C) is an E3 ubiquitin ligase and a key regulator of cell cycle progression. By triggering the degradation of mitotic... (Review)
Review
The Anaphase-Promoting Complex/Cyclosome (APC/C) is an E3 ubiquitin ligase and a key regulator of cell cycle progression. By triggering the degradation of mitotic cyclins, APC/C controls cell cycle-dependent oscillations in cyclin-dependent kinase (CDK) activity. Thus, the dynamic activities of both APC/C and CDK sit at the core of the cell cycle oscillator. The APC/C controls a large number of substrates and is regulated through multiple mechanisms, including cofactor-dependent activation. These cofactors, Cdc20 and Cdh1, recognize substrates, while the specific E2 enzymes UBE2C/UbcH10 and UBE2S cooperate with APC/C to build K11-linked ubiquitin chains on substrates to target them for proteasomal degradation. However, whether deubiquitinating enzymes (DUBs) can antagonize APC/C substrate ubiquitination during mitosis has remained largely unknown. We recently demonstrated that Cezanne/OTUD7B is a cell cycle-regulated DUB that opposes the ubiquitination of APC/C substrates. Cezanne binds APC/C substrates, reverses their ubiquitination and protects them from degradation. Accordingly, Cezanne depletion accelerates APC/C substrate degradation, leading to errors in mitotic progression and formation of micronuclei. Moreover, Cezanne is significantly amplified and overexpressed in breast cancers. This suggests a potential role for APC/C antagonism in the pathogenesis of disease. APC/C contributes to chromosome segregation fidelity in mitosis raising the possibility that copy-number and expression changes in Cezanne observed in cancer contribute to the etiology of disease. Collectively, these observations identify a new player in cell cycle progression, define mechanisms of tempered APC/C substrate destruction and highlight the importance of this regulation in maintaining chromosome stability.
Topics: Anaphase-Promoting Complex-Cyclosome; Animals; Cell Cycle Proteins; Cell Nucleus Division; Chromosomal Instability; Chromosome Segregation; Endopeptidases; Humans; Mitosis; Ubiquitin; Ubiquitination
PubMed: 30874463
DOI: 10.1080/15384101.2019.1593646