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The Journal of Cell Biology Jun 2022Errors in mitosis that cause chromosome missegregation lead to aneuploidy and micronucleus formation, which are associated with cancer. Accurate segregation requires the...
Errors in mitosis that cause chromosome missegregation lead to aneuploidy and micronucleus formation, which are associated with cancer. Accurate segregation requires the alignment of all chromosomes by the mitotic spindle at the metaphase plate, and any misalignment must be corrected before anaphase is triggered. The spindle is situated in a membrane-free "exclusion zone"; beyond this zone, endomembranes (mainly endoplasmic reticulum) are densely packed. We investigated what happens to misaligned chromosomes localized beyond the exclusion zone. Here we show that such chromosomes become ensheathed in multiple layers of endomembranes. Chromosome ensheathing delays mitosis and increases the frequency of chromosome missegregation and micronucleus formation. We use an induced organelle relocalization strategy in live cells to show that clearance of endomembranes allows for the rescue of chromosomes that were destined for missegregation. Our findings indicate that endomembranes promote the missegregation of misaligned chromosomes that are outside the exclusion zone and therefore constitute a risk factor for aneuploidy.
Topics: Anaphase; Aneuploidy; Cell Membrane; Chromosome Segregation; Chromosomes; Endoplasmic Reticulum; Humans; Metaphase; Mitosis; Spindle Apparatus
PubMed: 35486148
DOI: 10.1083/jcb.202203021 -
Journal of Ginseng Research May 2022Although the tumor-suppressive effects of ginsenosides in cell cycle have been well established, their pharmacological properties in mitosis have not been clarified yet....
BACKGROUND
Although the tumor-suppressive effects of ginsenosides in cell cycle have been well established, their pharmacological properties in mitosis have not been clarified yet. The chromosomal instability resulting from dysregulated mitotic processes is usually increased in cancer. In this study, we aimed to investigate the anticancer effects of ginsenoside Rg1 on mitotic progression in cancer.
MATERIALS AND METHODS
Cancer cells were treated with ginsenoside Rg1 and their morphology and intensity of different protein were analyzed using immunofluorescence microscopy. The level of proteins in chromosomes was compared through chromosomal fractionation and Western blot analyses. The location and intensity of proteins in the chromosome were confirmed through immunostaining of mitotic chromosome after spreading. The colony formation assays were conducted using various cancer cell lines.
RESULTS
Ginsenoside Rg1 reduced cancer cell proliferation in some cancers through inducing mitotic arrest. Mechanistically, it inhibits the phosphorylation of histone H3 Thr3 (H3T3ph) mediated by Haspin kinase and concomitant recruitment of chromosomal passenger complex (CPC) to the centromere. Depletion of Aurora B at the centromere led to abnormal centromere integrity and spindle dynamics, thereby causing mitotic defects, such as increase in the width of the metaphase plate and spindle instability, resulting in delayed mitotic progression and cancer cell proliferation.
CONCLUSION
Ginsenoside Rg1 reduces the level of Aurora B at the centromere via perturbing Haspin kinase activity and concurrent H3T3ph. Therefore, ginsenoside Rg1 suppresses cancer cell proliferation through impeding mitotic processes, such as chromosome alignment and spindle dynamics, upon depletion of Aurora B from the centromere.
PubMed: 35600766
DOI: 10.1016/j.jgr.2021.11.004 -
Cell Division 2019Nuclear pore complexes (NPCs) act as nano-turnstiles within nuclear membranes between the cytoplasm and nucleus of mammalian cells. NPC proteins, called nucleoporins...
BACKGROUND
Nuclear pore complexes (NPCs) act as nano-turnstiles within nuclear membranes between the cytoplasm and nucleus of mammalian cells. NPC proteins, called nucleoporins (Nups), mediate trafficking of proteins and RNA into and out of the nucleus, and are involved in a variety of mitotic processes. We previously reported that Nup62 localizes to the centrosome and mitotic spindle during mitosis, and plays a role in centrosome homeostasis. However, whether Nup58, a Nup62 subcomplex protein, also localizes to spindle poles is unknown.
RESULT
Herein, we show that Nup58 localizes to the nuclear rim during interphase, and to mitotic spindles, centrosomes, and midbodies during mitosis. Our confocal microscopy, live-cell imaging, and stimulated emission depletion nanoscopy results also demonstrated that Nup58 localized to the centrosomes during metaphase and relocalized to midbodies during abscission. Depletion of Nup58 resulted in centrosomal abnormalities and delayed abscission.
CONCLUSION
Nup58 localized at the centrosomes and mitotic spindle during metaphase and relocalized at midbodies during abscission. This study highlights the important role of Nup58 in mitosis.
PubMed: 31388347
DOI: 10.1186/s13008-019-0050-z -
Science Advances Mar 2024Canonical mitotic and meiotic cell divisions commence with replicated chromosomes consisting of two sister chromatids. Here, we developed and explored a model of...
Canonical mitotic and meiotic cell divisions commence with replicated chromosomes consisting of two sister chromatids. Here, we developed and explored a model of premature cell division, where nonreplicated, G/G-stage somatic cell nuclei are transplanted to the metaphase cytoplasm of mouse oocytes. Subsequent cell division generates daughter cells with reduced ploidy. Unexpectedly, genome sequencing analysis revealed proper segregation of homologous chromosomes, resulting in complete haploid genomes. We observed a high occurrence of somatic genome haploidization in nuclei from inbred genetic backgrounds but not in hybrids, emphasizing the importance of sequence homology between homologs. These findings suggest that premature cell division relies on mechanisms similar to meiosis I, where genome haploidization is facilitated by homologous chromosome interactions, recognition, and pairing. Unlike meiosis, no evidence of recombination between somatic cell homologs was detected. Our study offers an alternative in vitro gametogenesis approach by directly reprogramming diploid somatic cells into haploid oocytes.
Topics: Animals; Mice; Haploidy; Diploidy; Meiosis; Cell Nucleus; Chromatids
PubMed: 38457500
DOI: 10.1126/sciadv.adk9001 -
Cancer Journal (Sudbury, Mass.)The Aurora kinases (AURKA and AURKB) have attracted attention as therapeutic targets in head and neck squamous cell carcinomas. Aurora kinases were first defined as...
The Aurora kinases (AURKA and AURKB) have attracted attention as therapeutic targets in head and neck squamous cell carcinomas. Aurora kinases were first defined as regulators of mitosis that localization to the centrosome (AURKA) and centromere (AURKB), governing formation of the mitotic spindle, chromatin condensation, activation of the core mitotic kinase CDK1, alignment of chromosomes at metaphase, and other processes. Subsequently, additional roles for Aurora kinases have been defined in other phases of cell cycle, including regulation of ciliary disassembly and DNA replication. In cancer, elevated expression and activity of Aurora kinases result in enhanced or neomorphic locations and functions that promote aggressive disease, including promotion of MYC expression, oncogenic signaling, stem cell identity, epithelial-mesenchymal transition, and drug resistance. Numerous Aurora-targeted inhibitors have been developed and are being assessed in preclinical and clinical trials, with the goal of improving head and neck squamous cell carcinoma treatment.
Topics: Aurora Kinase A; Chromatin; Head and Neck Neoplasms; Humans; Squamous Cell Carcinoma of Head and Neck
PubMed: 36165728
DOI: 10.1097/PPO.0000000000000614 -
Genes Jan 2023Telomeres present inherent difficulties to the DNA replication machinery due to their repetitive sequence content, formation of non-B DNA secondary structures, and the... (Review)
Review
Telomeres present inherent difficulties to the DNA replication machinery due to their repetitive sequence content, formation of non-B DNA secondary structures, and the presence of the nucleo-protein t-loop. Especially in cancer cells, telomeres are hot spots for replication stress, which can result in a visible phenotype in metaphase cells termed "telomere fragility". A mechanism cells employ to mitigate replication stress, including at telomeres, is DNA synthesis in mitosis (MiDAS). While these phenomena are both observed in mitotic cells, the relationship between them is poorly understood; however, a common link is DNA replication stress. In this review, we will summarize what is known to regulate telomere fragility and telomere MiDAS, paying special attention to the proteins which play a role in these telomere phenotypes.
Topics: DNA Replication; DNA; Mitosis; Phenotype; Telomere
PubMed: 36833275
DOI: 10.3390/genes14020348 -
Molecular Cell Sep 2020A long-standing conundrum is how mitotic chromosomes can compact, as required for clean separation to daughter cells, while maintaining close parallel alignment of...
A long-standing conundrum is how mitotic chromosomes can compact, as required for clean separation to daughter cells, while maintaining close parallel alignment of sister chromatids. Pursuit of this question, by high resolution 3D fluorescence imaging of living and fixed mammalian cells, has led to three discoveries. First, we show that the structural axes of separated sister chromatids are linked by evenly spaced "mini-axis" bridges. Second, when chromosomes first emerge as discrete units, at prophase, they are organized as co-oriented sister linear loop arrays emanating from a conjoined axis. We show that this same basic organization persists throughout mitosis, without helical coiling. Third, from prophase onward, chromosomes are deformed into sequential arrays of half-helical segments of alternating handedness (perversions), accompanied by correlated kinks. These arrays fluctuate dynamically over <15 s timescales. Together these discoveries redefine the foundation for thinking about the evolution of mitotic chromosomes as they prepare for anaphase segregation.
Topics: Adenosine Triphosphatases; Anaphase; Animals; Cell Cycle Proteins; Chromatids; Chromosomal Proteins, Non-Histone; Chromosomes; DNA Topoisomerases, Type II; DNA-Binding Proteins; Imaging, Three-Dimensional; Mammals; Metaphase; Mitosis; Prophase
PubMed: 32768407
DOI: 10.1016/j.molcel.2020.07.002 -
ELife May 2022Cell mass and composition change with cell cycle progression. Our previous work characterized buoyant mass dynamics in mitosis (Miettinen et al., 2019), but how dry mass...
Cell mass and composition change with cell cycle progression. Our previous work characterized buoyant mass dynamics in mitosis (Miettinen et al., 2019), but how dry mass and cell composition change in mitosis has remained unclear. To better understand mitotic cell growth and compositional changes, we develop a single-cell approach for monitoring dry mass and the density of that dry mass every ~75 s with 1.3% and 0.3% measurement precision, respectively. We find that suspension grown mammalian cells lose dry mass and increase dry mass density following mitotic entry. These changes display large, non-genetic cell-to-cell variability, and the changes are reversed at metaphase-anaphase transition, after which dry mass continues accumulating. The change in dry mass density causes buoyant and dry mass to differ specifically in early mitosis, thus reconciling existing literature on mitotic cell growth. Mechanistically, cells in early mitosis increase lysosomal exocytosis, and inhibition of lysosomal exocytosis decreases the dry mass loss and dry mass density increase in mitosis. Overall, our work provides a new approach for monitoring single-cell dry mass and dry mass density, and reveals that mitosis is coupled to extensive exocytosis-mediated secretion of cellular contents.
Topics: Anaphase; Animals; Cell Cycle; Exocytosis; Mammals; Metaphase; Mitosis
PubMed: 35535854
DOI: 10.7554/eLife.76664 -
Cell Cycle (Georgetown, Tex.) Jan 2020Lumican is overexpressed in lung cancer cells and has been implicated in the pathogenesis of tumorigenesis and regulation of cancer cell invasion. Lumican is robustly...
Lumican is overexpressed in lung cancer cells and has been implicated in the pathogenesis of tumorigenesis and regulation of cancer cell invasion. Lumican is robustly associated with the binding of p120-catenin protein to modulate cell metastasis. However, its role in cancer cell proliferation is still unclear. This study investigated the effect of lumican on the cell division including mitosis and cytokinesis in non-small lung cancer cells. We found that the downregulation of lumican prolonged the doubling time of cells and retarded the cell growth in H460 and A549 cells. Along with tubulin, lumican localized to the mitotic spindle and centrosome during the metaphase-anaphase stage. The cell cycle was retained in the G2/M phase after the downregulation of lumican. Interestingly, lumican was found to play important roles in central spindle and midbody formation during cytokinesis. Lumican interacted with the midbody-associated proteins such as MKLP1, Aurora B, and ECT2. Notably, the downregulation of lumican decreased the level of MKLP1 accompanied by the retention of midbody-residual that resulted in multi-nucleated cells. Downregulation of lumican promoted the chromosome missegregation and the increment of the bi-/multinucleated cells. The results of this study indicated that lumican associated with tubulin is crucial for spindle fiber formation and midbody assembly in cell division. Downregulation of lumican displayed the defects in mitotic spindle assembly/dynamics and improper kinetochore-microtubules attachment that led to increase aneuploidy. This emerging property of lumican is suggested to tightly control chromosome segregation during cell division in lung cancer cells. ESCRT: endosomal sorting complex required for transport; PRC1: protein regulator of cytokinesis 1; Nci: negative control siRNA; Lumi: lumican siRNAs; MKLP1: mitotic kinesin-like protein 1; H460LD and A549LD: H460 and A549 cell lines with less expressed lumican.
Topics: Aneuploidy; Cell Line, Tumor; Cell Proliferation; Cytokinesis; Down-Regulation; Humans; Lumican; Lung Neoplasms; Microtubules; Mitosis; Proto-Oncogene Proteins
PubMed: 31760859
DOI: 10.1080/15384101.2019.1693189 -
Cytogenetic and Genome Research 2022Mitotic chromosomes of butterflies, which look like dots or short filaments in most published data, are generally considered to lack localised centromeres and thus to be...
Mitotic chromosomes of butterflies, which look like dots or short filaments in most published data, are generally considered to lack localised centromeres and thus to be holokinetic. This particularity, observed in a number of other invertebrates, is associated with meiotic particularities known as "inverted meiosis," in which the first division is equational, i.e., centromere splitting-up and segregation of sister chromatids instead of homologous chromosomes. However, the accurate analysis of butterfly chromosomes is difficult because (1) their size is very small, equivalent to 2 bands of a mammalian metaphase chromosome, and (2) they lack satellite DNA/heterochromatin in putative centromere regions and therefore marked primary constrictions. Our improved conditions for basic chromosome preparations, here applied to 6 butterfly species belonging to families Nymphalidae and Pieridae challenges the holocentricity of their chromosomes: in spite of the absence of primary constrictions, sister chromatids are recurrently held together at definite positions during mitotic metaphase, which makes possible to establish karyotypes composed of acrocentric and submetacentric chromosomes. The total number of chromosomes per karyotype is roughly inversely proportional to that of non-acrocentric chromosomes, which suggests the occurrence of frequent robertsonian-like fusions or fissions during evolution. Furthermore, the behaviour and morphological changes of chromosomes along the various phases of meiosis do not seem to differ much from those of canonical meiosis. In particular, at metaphase II chromosomes clearly have 2 sister chromatids, which refutes that anaphase I was equational. Thus, we propose an alternative mechanism to holocentricity for explaining the large variations in chromosome numbers in butterflies: (1) in the ancestral karyotype, composed of about 62 mostly acrocentric chromosomes, the centromeres, devoid of centromeric heterochromatin/satellite DNA, were located at contact with telomeric heterochromatin; (2) the instability of telomeric heterochromatin largely contributed to drive the multiple rearrangements, principally chromosome fusions, which occurred during butterfly evolution.
Topics: Humans; Animals; Butterflies; Heterochromatin; DNA, Satellite; Chromosomes; Centromere; Meiosis; Chromatids; Karyotyping; Mammals
PubMed: 36689925
DOI: 10.1159/000526034