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Life Science Alliance Nov 2023In metazoans, Polo-like kinase (PLK1) controls several mitotic events including nuclear envelope breakdown, centrosome maturation, spindle assembly and progression...
In metazoans, Polo-like kinase (PLK1) controls several mitotic events including nuclear envelope breakdown, centrosome maturation, spindle assembly and progression through mitosis. Here we show that a mutation in the mitochondria-localized protein SPD-3 affects mitotic events by inducing elevated levels of PLK-1 in early embryos. SPD-3 mutant embryos contain abnormally positioned mitotic chromosomes, show a delay in anaphase onset and asymmetrically disassemble the nuclear lamina. We found that more PLK-1 accumulated on centrosomes, nuclear envelope, nucleoplasm, and chromatin before NEBD, suggesting that PLK-1 overexpression is responsible for some of the observed mitotic phenotypes. In agreement with this, the chromosome positioning defects of the mutant could be rescued by reducing PLK-1 levels. Our data suggests that the mitochondrial SPD-3 protein affects chromosome positioning and nuclear envelope integrity by up-regulating the endogenous levels of PLK-1 during early embryogenesis in This finding suggests a novel link between mitochondria and nuclear envelope dynamics and chromosome positioning by increasing the amount of a key mitotic regulator, PLK-1, providing a novel link between mitochondria and mitosis.
Topics: Animals; Mitochondrial Proteins; Caenorhabditis elegans; Cell Cycle; Mitosis; Cell Nucleus
PubMed: 37684042
DOI: 10.26508/lsa.202302011 -
Protoplasma Jul 2023Diterpenoid 3-epicaryoptin (CHO) is abundant in the leaves of Clerodendrum inerme, a traditionally used medicinal plant, and has insect antifeedant activities. Here, we...
Diterpenoid 3-epicaryoptin (CHO) is abundant in the leaves of Clerodendrum inerme, a traditionally used medicinal plant, and has insect antifeedant activities. Here, we aim to explore the cytogenotoxic effects of compound 3-epicaryoptin in Allium cepa root apical meristem cells. 3-epicaryoptin (concentrations of 100, 150, and 200 µg mL) and the standard compound colchicine (200 µg mL) were applied to A. cepa roots for 2, 4, and 4 + 16 h (4-h treatment followed by 16-h recovery). Cytogenotoxicity was analyzed by studying the root growth retardation (RGR), mitotic index (MI), and chromosomal aberrations. The result showed statistically significant (p < 0.01), concentration-dependent RGR effects of 3-epicaryoptin treatment compared with the negative control. A study of cell frequency in different phases of cell division observed a significant (p < 0.001) increase in the metaphase cell percentage (66.2 ± 0.58%, 150 µg mL), which subsequently caused an increase in the frequency of MI (12.29 ± 0.34%, 150 µg mL) at 4 h of 3-epicaryoptin treatment and that was comparable with the colchicine action. The cytological study revealed that the 3-epicaryoptin treatment could induce different types of chromosomal abnormalities, such as colchicine-like metaphase, vagrant chromosomes, sticky chromosomes, anaphase bridge, lagging chromosomes, multipolar anaphase-telophase, and an increased frequency of micronuclei and polyploid cells. These findings indicate that 3-epicaryoptin is cytogenotoxic, and thus, C. inerme should be used with caution in traditional medicine.
Topics: Meristem; Onions; Plant Roots; Mitosis; Mitotic Index; Chromosome Aberrations; DNA Damage
PubMed: 36735079
DOI: 10.1007/s00709-023-01838-6 -
BMC Biology Mar 2024Mitogen-activated protein kinases (MAPKs) preserve cell homeostasis by transducing physicochemical fluctuations of the environment into multiple adaptive responses....
BACKGROUND
Mitogen-activated protein kinases (MAPKs) preserve cell homeostasis by transducing physicochemical fluctuations of the environment into multiple adaptive responses. These responses involve transcriptional rewiring and the regulation of cell cycle transitions, among others. However, how stress conditions impinge mitotic progression is largely unknown. The mitotic checkpoint is a surveillance mechanism that inhibits mitotic exit in situations of defective chromosome capture, thus preventing the generation of aneuploidies. In this study, we investigate the role of MAPK Pmk1 in the regulation of mitotic exit upon stress.
RESULTS
We show that Schizosaccharomyces pombe cells lacking Pmk1, the MAP kinase effector of the cell integrity pathway (CIP), are hypersensitive to microtubule damage and defective in maintaining a metaphase arrest. Epistasis analysis suggests that Pmk1 is involved in maintaining spindle assembly checkpoint (SAC) signaling, and its deletion is additive to the lack of core SAC components such as Mad2 and Mad3. Strikingly, pmk1Δ cells show up to twofold increased levels of the anaphase-promoting complex (APC/C) activator Cdc20 during unperturbed growth. We demonstrate that Pmk1 physically interacts with Cdc20 N-terminus through a canonical MAPK docking site. Most important, the Cdc20 pool is rapidly degraded in stressed cells undergoing mitosis through a mechanism that requires MAPK activity, Mad3, and the proteasome, thus resulting in a delayed mitotic exit.
CONCLUSIONS
Our data reveal a novel function of MAPK in preventing mitotic exit and activation of cytokinesis in response to stress. The regulation of Cdc20 turnover by MAPK Pmk1 provides a key mechanism by which the timing of mitotic exit can be adjusted relative to environmental conditions.
Topics: Schizosaccharomyces; Anaphase-Promoting Complex-Cyclosome; Schizosaccharomyces pombe Proteins; Cdc20 Proteins; Cell Cycle Proteins; Mitosis; Spindle Apparatus
PubMed: 38523261
DOI: 10.1186/s12915-024-01865-6 -
Archives of Microbiology Aug 2023Gastrodia elata needs to establish a symbiotic relationship with Armillaria strains to obtain nutrients and energy. However, the signaling cross talk between G. elata...
Gastrodia elata needs to establish a symbiotic relationship with Armillaria strains to obtain nutrients and energy. However, the signaling cross talk between G. elata and Armillaria strains is still unclear. During our experiment, we found that the vegetative mycelium of Armillaria gallica 012m grew significantly better in the media containing gibberellic acid (GA3) than the blank control group (BK). To explore the response mechanism, we performed an RNA-sequencing experiment to profile the transcriptome changes of A. gallica 012m cultured in the medium with exogenous GA3. The transcriptome-guided differential expression genes (DEGs) analysis of GA3 and BK showed that a total of 1309 genes were differentially expressed, including 361 upregulated genes and 948 downregulated genes. Some of those DEGs correlated with the biological process, including positive regulation of chromosome segregation, mitotic metaphase/anaphase transition, attachment of mitotic spindle microtubules to kinetochore, mitotic cytokinesis, and nuclear division. These analyses explained that GA3 actively promoted the growth of A. gallica to some extent. Further analysis of protein domain features showed that the deduced polypeptide contained 41 candidate genes of GA receptor, and 27 of them were expressed in our samples. We speculate that GA receptors exist in A. gallica 012m. Comparative studies of proteins showed that the postulated GA receptor domains of A. gallica 012m have a higher homologous correlation with fungi than others based on cluster analysis.
Topics: Armillaria; Cluster Analysis; Gene Expression Profiling; Mycelium
PubMed: 37594611
DOI: 10.1007/s00203-023-03621-w -
Methods in Molecular Biology (Clifton,... 2024In this chapter, we describe a software called MAARS (Mitotic Analysis And Recording System) that enables automatic and quantitative analysis of mitotic progression on...
In this chapter, we describe a software called MAARS (Mitotic Analysis And Recording System) that enables automatic and quantitative analysis of mitotic progression on an open-source platform. This computer-assisted analysis of cell division allows the unbiased acquisition of multiple parameters such as cell shape or size, metaphase or anaphase delays, as well as various mitotic abnormalities. This chapter describes the power of such an expert system to highlight the complexity of the mechanisms required to prevent mitotic chromosome segregation errors, leading to aneuploidy.
Topics: Mitosis; Spindle Apparatus; Metaphase; Anaphase; Chromosome Segregation; Software
PubMed: 38393482
DOI: 10.1007/978-1-0716-3557-5_17 -
PloS One 2023The mitotic regulator, Aurora kinase B (AURKB), is frequently overexpressed in malignancy and is a target for therapeutic intervention. The compound, LXY18, is a potent,...
The mitotic regulator, Aurora kinase B (AURKB), is frequently overexpressed in malignancy and is a target for therapeutic intervention. The compound, LXY18, is a potent, orally available small molecule that inhibits the proper localization of AURKB during late mitosis, without affecting its kinase activity. In this study, we demonstrate that LXY18 elicits apoptosis in cancer cells derived from various indications, but not in non-transformed cell lines. The apoptosis is p53-independent, triggered by a prolonged mitotic arrest and occurs predominantly in mitosis. Some additional cells succumb post-mitotic slippage. We also demonstrate that cancer cell lines refractory to AURKB kinase inhibitors are sensitive to LXY18. The mitotic proteins MKLP2, NEK6, NEK7 and NEK9 are known regulators of AURKB localization during the onset of anaphase. LXY18 fails to inhibit the catalytic activity of these AURKB localization factors. Overall, our findings suggest a novel activity for LXY18 that produces a prolonged mitotic arrest and lethality in cancer cells, leaving non-transformed cells healthy. This new activity suggests that the compound may be a promising drug candidate for cancer treatment and that it can also be used as a tool compound to further dissect the regulatory network controlling AURKB localization.
Topics: Humans; Aurora Kinase B; Aurora Kinase A; Cell Death; Mitosis; Neoplasms; NIMA-Related Kinases
PubMed: 37903144
DOI: 10.1371/journal.pone.0293283 -
Life Science Alliance Nov 2023Different types of anaphase bridges are reported to form between segregating chromosomes during cell division. Previous studies using laser microsurgery suggested that...
Different types of anaphase bridges are reported to form between segregating chromosomes during cell division. Previous studies using laser microsurgery suggested that elastic tethers connect the telomeres of separating anaphase chromosomes in many animal meiotic and mitotic cells. However, structural evidence is lacking for their existence. In this study, by correlating live imaging with electron tomography, we examined whether visible structures connect separating telomeres in meiosis I of crane-fly primary spermatocytes. We found structures extending between separating telomeres in all stages of anaphase. The structures consist of two components: one is darkly stained, looking somewhat like chromatin, whereas the other is more lightly stained, appearing filamentous. Although in early anaphase both structures extend between telomeres, in later anaphase, the darker structure extends shorter distances from the telomeres but the lighter structure still extends between the separating telomeres. From these observations, we deduced that these structures represent the "tethers" inferred from the laser-cutting experiments. Because elastic tethers have been detected in a variety of animal cells, they probably are present during anaphase in all animal cells.
Topics: Animals; Male; Spermatocytes; Telomere; Chromatin; Meiosis; Cytoskeleton
PubMed: 37591724
DOI: 10.26508/lsa.202302303 -
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 -
Cell Structure and Function Jun 2024In metazoans, the nuclear envelope (NE) disassembles during the prophase and reassembles around segregated chromatids during the telophase. The process of NE formation...
In metazoans, the nuclear envelope (NE) disassembles during the prophase and reassembles around segregated chromatids during the telophase. The process of NE formation has been extensively studied using live-cell imaging. At the early step of NE reassembly in human cells, specific pattern-like localization of inner nuclear membrane (INM) proteins, connected to the nuclear pore complex (NPC), was observed in the so-called "core" region and "noncore" region on telophase chromosomes, which corresponded to the "pore-free" region and the "pore-rich" region, respectively, in the early G1 interphase nucleus. We refer to these phenomena as NE subdomain formation. To biochemically investigate this process, we aimed to develop an in vitro NE reconstitution system using digitonin-permeabilized semi-intact mitotic human cells coexpressing two INM proteins, emerin and lamin B receptor, which were labeled with fluorescent proteins. The targeting and accumulation of INM proteins to chromosomes before and after anaphase onset in semi-intact cells were observed using time-lapse imaging. Our in vitro NE reconstitution system recapitulated the formation of the NE subdomain, as in living cells, although chromosome segregation and cytokinesis were not observed. This in vitro NE reconstitution required the addition of a mitotic cytosolic fraction supplemented with a cyclin-dependent kinase inhibitor and energy sources. The cytoplasmic soluble factor(s) dependency of INM protein targeting differed among the segregation states of chromosomes. Furthermore, the NE reconstituted on segregated chromosomes exhibited active nucleocytoplasmic transport competency. These results indicate that the chromosome status changes after anaphase onset for recruiting NPC components.Key words: nuclear envelope reassembly, inner nuclear membrane protein, nuclear pore complex, semi-intact cell, in vitro reconstitution.
PubMed: 38839376
DOI: 10.1247/csf.24003 -
Journal of Cell Science Jul 2023Cell division involves separating the genetic material and cytoplasm of a mother cell into two daughter cells. The last step of cell division, abscission, consists of...
Cell division involves separating the genetic material and cytoplasm of a mother cell into two daughter cells. The last step of cell division, abscission, consists of cutting the cytoplasmic bridge, a microtubule-rich membranous tube connecting the two cells, which contains the midbody, a dense proteinaceous structure. Canonically, abscission occurs 1-3 h after anaphase. However, in certain cases, abscission can be severely delayed or incomplete. Abscission delays can be caused by mitotic defects that activate the abscission 'NoCut' checkpoint in tumor cells, as well as when cells exert abnormally strong pulling forces on the bridge. Delayed abscission can also occur during normal organism development. Here, we compare the mechanisms triggering delayed and incomplete abscission in healthy and disease scenarios. We propose that NoCut is not a bona fide cell cycle checkpoint, but a general mechanism that can control the dynamics of abscission in multiple contexts.
Topics: Animals; Cytoplasm; Stem Cells; Cytosol; Microtubules; Anaphase
PubMed: 37387255
DOI: 10.1242/jcs.260520