bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2024–05–19
fourteen papers selected by
Valentina Piano, Uniklinik Köln
  1. Vertebrate centromeres in mitosis are functionally bipartite structures stabilized by cohesin.
  2. U3 snoRNA inter-regulates with DDX21 in the perichromosomal region to control mitosis.
  3. Aurora-A condensation mediated by BuGZ aids its mitotic centrosome functions.
  4. Liquid-liquid phase separation of microtubule-binding proteins in the regulation of spindle assembly.
  5. Ipsilateral restriction of chromosome movement along a centrosome, and apical-basal axis during the cell cycle.
  6. UHRF2 accumulates in early G1-phase after serum stimulation or mitotic exit to extend G1 and total cell cycle length.
  7. A-MYB substitutes for B-MYB in activating cell cycle genes and in stimulating proliferation.
  8. An improved epigenetic counter to track mitotic age in normal and precancerous tissues.
  9. Survivin as a Therapeutic Target for the Treatment of Human Cancer.
  10. Modification of Seurat v4 for the Development of a Phase Assignment Tool Able to Distinguish between G2 and Mitotic Cells.
  11. dsRNAi-mediated silencing of PIAS2beta specifically kills anaplastic carcinomas by mitotic catastrophe.
  12. A novel multilevel iterative training strategy for the ResNet50 based mitotic cell classifier.
  13. Microtubule dependent sorting of actin-binding proteins in mitosis.
  14. Activation of the Anaphase Promoting Complex Restores Impaired Mitotic Progression and Chemosensitivity in Multiple Drug-Resistant Human Breast Cancer.
  1. Cell. 2024 May 08. pii: S0092-8674(24)00409-4. [Epub ahead of print]
    Vertebrate centromeres in mitosis are functionally bipartite structures stabilized by cohesin.
    Carlos Sacristan, Kumiko Samejima, Lorena Andrade Ruiz, Moonmoon Deb, Maaike L A Lambers, Adam Buckle, Chris A Brackley, Daniel Robertson, Tetsuya Hori, Shaun Webb, Robert Kiewisz, Tristan Bepler, Eloïse van Kwawegen, Patrik Risteski, Kruno Vukušić, Iva M Tolić, Thomas Müller-Reichert, Tatsuo Fukagawa, Nick Gilbert, Davide Marenduzzo, William C Earnshaw, Geert J P L Kops.
      Centromeres are scaffolds for the assembly of kinetochores that ensure chromosome segregation during cell division. How vertebrate centromeres obtain a three-dimensional structure to accomplish their primary function is unclear. Using super-resolution imaging, capture-C, and polymer modeling, we show that vertebrate centromeres are partitioned by condensins into two subdomains during mitosis. The bipartite structure is found in human, mouse, and chicken cells and is therefore a fundamental feature of vertebrate centromeres. Super-resolution imaging and electron tomography reveal that bipartite centromeres assemble bipartite kinetochores, with each subdomain binding a distinct microtubule bundle. Cohesin links the centromere subdomains, limiting their separation in response to spindle forces and avoiding merotelic kinetochore-spindle attachments. Lagging chromosomes during cancer cell divisions frequently have merotelic attachments in which the centromere subdomains are separated and bioriented. Our work reveals a fundamental aspect of vertebrate centromere biology with implications for understanding the mechanisms that guarantee faithful chromosome segregation.
    Keywords:  centromere; chromatin organization; chromosomal instability; cohesin; condensin; kinetochore; mitosis
    DOI:  https://doi.org/10.1016/j.cell.2024.04.014
  2. Cell Death Dis. 2024 May 17. 15(5): 342
    U3 snoRNA inter-regulates with DDX21 in the perichromosomal region to control mitosis.
    Yang Jiang, Shiqi Sun, Xiaofeng Liu, Kunqi Su, Chunfeng Zhang, Peipei Zhang, Zhuochen Zhao, Ya Su, Chang Wang, Xiaojuan Du.
      U3 snoRNA is essential for ribosome biogenesis during interphase. Upon mitotic onset, the nucleolus disassembles and U3 snoRNA relocates to the perichromosomal region (PR) to be considered as a chromosome passenger. Whether U3 controls mitosis remains unknown. Here, we demonstrate that U3 snoRNA is required for mitotic progression. We identified DDX21 as the predominant U3-binding protein during mitosis and confirmed that U3 snoRNA colocalizes with DDX21 in the PR. DDX21 knockdown induces mitotic catastrophe and similar mitotic defects caused by U3 snoRNA depletion. Interestingly, the uniform PR distribution of U3 snoRNA and DDX21 is interdependent. DDX21 functions in mitosis depending on its PR localization. Mechanistically, U3 snoRNA regulates DDX21 PR localization through maintaining its mobility. Moreover, Cy5-U3 snoRNA downsizes the fibrous condensates of His-DDX21 at proper molecular ratios in vitro. This work highlights the importance of the equilibrium between U3 snoRNA and DDX21 in PR formation and reveals the potential relationship between the PR assembly and mitotic regulation.
    DOI:  https://doi.org/10.1038/s41419-024-06725-3
  3. iScience. 2024 May 17. 27(5): 109785
    Aurora-A condensation mediated by BuGZ aids its mitotic centrosome functions.
    Hui Zheng, Qiaoqiao Zhang, Xing Liu, Fan Shi, Fengrui Yang, Shengqi Xiang, Hao Jiang.
      Centrosomes composed of centrioles and the pericentriolar material (PCM), serve as the platform for microtubule polymerization during mitosis. Despite some centriole and PCM proteins have been reported to utilize liquid-liquid phase separation (LLPS) to perform their mitotic functions, whether and how centrosomal kinases exert the coacervation in mitosis is still unknown. Here we reveal that Aurora-A, one key centrosomal kinase in regulating centrosome formation and functions, undergoes phase separation in vitro or in centrosomes from prophase, mediated by the conserved positive-charged residues inside its intrinsic disordered region (IDR) and the intramolecular interaction between its N- and C-terminus. Aurora-A condensation affects centrosome maturation, separation, initial spindle formation from the spindle pole and its kinase activity. Moreover, BuGZ interacts with Aurora-A to enhance its LLPS and centrosome functions. Thus, we propose that Aurora-A collaborates with BuGZ to exhibit the property of LLPS in centrosomes to control its centrosome-dependent functions from prophase.
    Keywords:  Biophysics; Cell biology; Functional aspects of cell biology
    DOI:  https://doi.org/10.1016/j.isci.2024.109785
  4. Cell Prolif. 2024 May 13. e13649
    Liquid-liquid phase separation of microtubule-binding proteins in the regulation of spindle assembly.
    Shuang Sun, Jun Zhou, Peiwei Liu.
      Cell division is a highly regulated process essential for the accurate segregation of chromosomes. Central to this process is the assembly of a bipolar mitotic spindle, a highly dynamic microtubule (MT)-based structure responsible for chromosome movement. The nucleation and dynamics of MTs are intricately regulated by MT-binding proteins. Over the recent years, various MT-binding proteins have been reported to undergo liquid-liquid phase separation, forming either single- or multi-component condensates on MTs. Herein, we provide a comprehensive summary of the phase separation characteristics of these proteins. We underscore their critical roles in MT nucleation, spindle assembly and kinetochore-MT attachment during the cell division process. Furthermore, we discuss the current challenges and various remaining unsolved problems, highlights the ongoing research efforts aimed at a deeper understanding of the role of the phase separation process during spindle assembly and orientation. Our review aims to contribute to the collective knowledge in this area and stimulate further investigations that will enhance our comprehension of the intricate mechanisms governing cell division.
    DOI:  https://doi.org/10.1111/cpr.13649
  5. Res Sq. 2024 Apr 29. pii: rs.3.rs-4283973. [Epub ahead of print]
    Ipsilateral restriction of chromosome movement along a centrosome, and apical-basal axis during the cell cycle.
    Pingping Cai, Christian Joseph Casas, Gabriel Quintero Plancarte, Takashi Mikawa, Lisa L Hua.
      Little is known about how distance between homologous chromosomes are controlled during the cell cycle. Here, we show that the distribution of centromere components display two discrete clusters placed to either side of the centrosome and apical/basal axis from prophase to G1 interphase. 4-Dimensional live cell imaging analysis of centromere and centrosome tracking reveals that centromeres oscillate largely within one cluster, but do not cross over to the other cluster. We propose a model of an axis-dependent ipsilateral restriction of chromosome oscillations throughout mitosis.
    DOI:  https://doi.org/10.21203/rs.3.rs-4283973/v1
  6. Cell Cycle. 2024 May 16. 1-15
    UHRF2 accumulates in early G1-phase after serum stimulation or mitotic exit to extend G1 and total cell cycle length.
    Xiaohong Wang, Huarui Lu, Grace Sprangers, Timothy C Hallstrom.
      Ubiquitin like with PHD and ring finger domains 2 (UHRF2) regulates the cell cycle and epigenetics as a multi-domain protein sharing homology with UHRF1. UHRF1 functions with DNMT1 to coordinate daughter strand methylation during DNA replication, but UHRF2 can't perform this function, and its roles during cell cycle progression are not well defined. UHRF2 role as an oncogene vs. tumor suppressor differs in distinct cell types. UHRF2 interacts with E2F1 to control Cyclin E1 (CCNE1) transcription. UHRF2 also functions in a reciprocal loop with Cyclin E/CDK2 during G1, first as a direct target of CDK2 phosphorylation, but also as an E3-ligase with direct activity toward both Cyclin E and Cyclin D. In this study, we demonstrate that UHRF2 is expressed in early G1 following either serum stimulation out of quiescence or in cells transiting directly out of M-phase, where UHRF2 protein is lost. Further, UHRF2 depletion in G2/M is reversed with a CDK1 specific inhibitor. UHRF2 controls expression levels of cyclins and CDK inhibitors and controls its own transcription in a negative-feedback loop. Deletion of UHRF2 using CRISPR/Cas9 caused a delay in passage through each cell cycle phase. UHRF2 loss culminated in elevated levels of cyclins but also the CDK inhibitor p27KIP1, which regulates G1 passage, to reduce retinoblastoma phosphorylation and increase the amount of time required to reach G1/S passage. Our data indicate that UHRF2 is a central regulator of cell-cycle pacing through its complex regulation of cell cycle gene expression and protein stability.
    Keywords:  FUCCI; UHRF2; cell cycle; cyclin/Cdk
    DOI:  https://doi.org/10.1080/15384101.2024.2353553
  7. Nucleic Acids Res. 2024 May 15. pii: gkae370. [Epub ahead of print]
    A-MYB substitutes for B-MYB in activating cell cycle genes and in stimulating proliferation.
    Robin Kohler, Kurt Engeland.
      A-MYB (MYBL1) is a transcription factor with a role in meiosis in spermatocytes. The related B-MYB protein is a key oncogene and a master regulator activating late cell cycle genes. To activate genes, B-MYB forms a complex with MuvB and is recruited indirectly to cell cycle genes homology region (CHR) promoter sites of target genes. Activation through the B-MYB-MuvB (MMB) complex is essential for successful mitosis. Here, we discover that A-MYB has a function in transcriptional regulation of the mitotic cell cycle and can substitute for B-MYB. Knockdown experiments in cells not related to spermatogenesis show that B-MYB loss alone merely delays cell cycle progression. Only dual knockdown of B-MYB and A-MYB causes G2/M cell cycle arrest, endoreduplication, and apoptosis. A-MYB can substitute for B-MYB in binding to MuvB. The resulting A-MYB-MuvB complex activates genes through CHR sites. We find that A-MYB activates the same target genes as B-MYB. Many of the corresponding proteins are central regulators of the cell division cycle. In summary, we demonstrate that A-MYB is an activator of the mitotic cell cycle by activating late cell cycle genes.
    DOI:  https://doi.org/10.1093/nar/gkae370
  8. Nat Commun. 2024 May 17. 15(1): 4211
    An improved epigenetic counter to track mitotic age in normal and precancerous tissues.
    Tianyu Zhu, Huige Tong, Zhaozhen Du, Stephan Beck, Andrew E Teschendorff.
      The cumulative number of stem cell divisions in a tissue, known as mitotic age, is thought to be a major determinant of cancer-risk. Somatic mutational and DNA methylation (DNAm) clocks are promising tools to molecularly track mitotic age, yet their relationship is underexplored and their potential for cancer risk prediction in normal tissues remains to be demonstrated. Here we build and validate an improved pan-tissue DNAm counter of total mitotic age called stemTOC. We demonstrate that stemTOC's mitotic age proxy increases with the tumor cell-of-origin fraction in each of 15 cancer-types, in precancerous lesions, and in normal tissues exposed to major cancer risk factors. Extensive benchmarking against 6 other mitotic counters shows that stemTOC compares favorably, specially in the preinvasive and normal-tissue contexts. By cross-correlating stemTOC to two clock-like somatic mutational signatures, we confirm the mitotic-like nature of only one of these. Our data points towards DNAm as a promising molecular substrate for detecting mitotic-age increases in normal tissues and precancerous lesions, and hence for developing cancer-risk prediction strategies.
    DOI:  https://doi.org/10.1038/s41467-024-48649-8
  9. Cancers (Basel). 2024 Apr 27. pii: 1705. [Epub ahead of print]16(9):
    Survivin as a Therapeutic Target for the Treatment of Human Cancer.
    Qiang Wang, Mark I Greene.
      Survivin was initially identified as a member of the inhibitor apoptosis (IAP) protein family and has been shown to play a critical role in the regulation of apoptosis. More recent studies showed that survivin is a component of the chromosome passenger complex and acts as an essential mediator of mitotic progression. Other potential functions of survivin, such as mitochondrial function and autophagy, have also been proposed. Survivin has emerged as an attractive target for cancer therapy because its overexpression has been found in most human cancers and is frequently associated with chemotherapy resistance, recurrence, and poor survival rates in cancer patients. In this review, we discuss our current understanding of how survivin mediates various aspects of malignant transformation and drug resistance, as well as the efforts that have been made to develop therapeutics targeting survivin for the treatment of cancer.
    Keywords:  apoptosis; cancer; mitosis; survivin
    DOI:  https://doi.org/10.3390/cancers16091705
  10. Int J Mol Sci. 2024 Apr 23. pii: 4589. [Epub ahead of print]25(9):
    Modification of Seurat v4 for the Development of a Phase Assignment Tool Able to Distinguish between G2 and Mitotic Cells.
    Steven Watson, Harry Porter, Ian Sudbery, Ruth Thompson.
      Single-cell RNA sequencing (scRNAseq) is a rapidly advancing field enabling the characterisation of heterogeneous gene expression profiles within a population. The cell cycle phase is a major contributor to gene expression variance between cells and computational analysis tools have been developed to assign cell cycle phases to cells within scRNAseq datasets. Whilst these tools can be extremely useful, all have the drawback that they classify cells as only G1, S or G2/M. Existing discrete cell phase assignment tools are unable to differentiate between G2 and M and continuous-phase-assignment tools are unable to identify a region corresponding specifically to mitosis in a pseudo-timeline for continuous assignment along the cell cycle. In this study, bulk RNA sequencing was used to identify differentially expressed genes between mitotic and interphase cells isolated based on phospho-histone H3 expression using fluorescence-activated cell sorting. These gene lists were used to develop a methodology which can distinguish G2 and M phase cells in scRNAseq datasets. The phase assignment tools present in Seurat were modified to allow for cell cycle phase assignment of all stages of the cell cycle to identify a mitotic-specific cell population.
    Keywords:  RNA sequencing; bioinformatics; cell cycle; mitosis; phase assignment
    DOI:  https://doi.org/10.3390/ijms25094589
  11. Nat Commun. 2024 May 14. 15(1): 3736
    dsRNAi-mediated silencing of PIAS2beta specifically kills anaplastic carcinomas by mitotic catastrophe.
    Joana S Rodrigues, Miguel Chenlo, Susana B Bravo, Sihara Perez-Romero, Maria Suarez-Fariña, Tomas Sobrino, Rebeca Sanz-Pamplona, Román González-Prieto, Manuel Narciso Blanco Freire, Ruben Nogueiras, Miguel López, Laura Fugazzola, José Manuel Cameselle-Teijeiro, Clara V Alvarez.
      The E3 SUMO ligase PIAS2 is expressed at high levels in differentiated papillary thyroid carcinomas but at low levels in anaplastic thyroid carcinomas (ATC), an undifferentiated cancer with high mortality. We show here that depletion of the PIAS2 beta isoform with a transcribed double-stranded RNA-directed RNA interference (PIAS2b-dsRNAi) specifically inhibits growth of ATC cell lines and patient primary cultures in vitro and of orthotopic patient-derived xenografts (oPDX) in vivo. Critically, PIAS2b-dsRNAi does not affect growth of normal or non-anaplastic thyroid tumor cultures (differentiated carcinoma, benign lesions) or cell lines. PIAS2b-dsRNAi also has an anti-cancer effect on other anaplastic human cancers (pancreas, lung, and gastric). Mechanistically, PIAS2b is required for proper mitotic spindle and centrosome assembly, and it is a dosage-sensitive protein in ATC. PIAS2b depletion promotes mitotic catastrophe at prophase. High-throughput proteomics reveals the proteasome (PSMC5) and spindle cytoskeleton (TUBB3) to be direct targets of PIAS2b SUMOylation at mitotic initiation. These results identify PIAS2b-dsRNAi as a promising therapy for ATC and other aggressive anaplastic carcinomas.
    DOI:  https://doi.org/10.1038/s41467-024-47751-1
  12. Comput Biol Chem. 2024 May 10. pii: S1476-9271(24)00080-X. [Epub ahead of print]110 108092
    A novel multilevel iterative training strategy for the ResNet50 based mitotic cell classifier.
    Yuqi Chen, Juan Liu, Peng Jiang, Yu Jin.
      The number of mitotic cells is an important indicator of grading invasive breast cancer. It is very challenging for pathologists to identify and count mitotic cells in pathological sections with naked eyes under the microscope. Therefore, many computational models for the automatic identification of mitotic cells based on machine learning, especially deep learning, have been proposed. However, converging to the local optimal solution is one of the main problems in model training. In this paper, we proposed a novel multilevel iterative training strategy to address the problem. To evaluate the proposed training strategy, we constructed the mitotic cell classification model with ResNet50 and trained the model with different training strategies. The results showed that the models trained with the proposed training strategy performed better than those trained with the conventional strategy in the independent test set, illustrating the effectiveness of the new training strategy. Furthermore, after training with our proposed strategy, the ResNet50 model with Adam optimizer has achieved 89.26% F1 score on the public MITOSI14 dataset, which is higher than that of the state-of-the-art methods reported in the literature.
    Keywords:  Deep learning; Invasive breast cancer; Mitotic cell; Multi-level iterative training strategy; ResNet50
    DOI:  https://doi.org/10.1016/j.compbiolchem.2024.108092
  13. Sci Rep. 2024 05 16. 14(1): 11250
    Microtubule dependent sorting of actin-binding proteins in mitosis.
    Jana Prassler, Mary Ecke, Günther Gerisch.
      The patterns of Formin B and of the Arp2/3 complex formed during mitosis were studied in a mutant of Dictyostelium discoideum that produces multinucleate cells, which divide by the ingression of unilateral cleavage furrows. During cytokinesis the cells of this mutant remain spread on a glass surface where they generate a planar pattern based on the sorting-out of actin-binding proteins. During anaphase, Formin B and Arp2/3 became localized to the regions of microtubule asters around the centrosomes; Formin B in particular in the form of round, quite uniformly covered areas. These areas have been shown to be depleted of myosin II and the actin-filament crosslinker cortexillin, and to be avoided by cleavage furrows on their path into the cell.
    Keywords:  Actin nucleation; Arp2/3 complex; Cytokinesis; Formin; Microtubules
    DOI:  https://doi.org/10.1038/s41598-024-61967-7
  14. Cancers (Basel). 2024 Apr 30. pii: 1755. [Epub ahead of print]16(9):
    Activation of the Anaphase Promoting Complex Restores Impaired Mitotic Progression and Chemosensitivity in Multiple Drug-Resistant Human Breast Cancer.
    Mathew Lubachowski, Cordell VanGenderen, Sarah Valentine, Zach Belak, Gerald Floyd Davies, Terra Gayle Arnason, Troy Anthony Alan Harkness.
      The development of multiple-drug-resistant (MDR) cancer all too often signals the need for toxic alternative therapy or palliative care. Our recent in vivo and in vitro studies using canine MDR lymphoma cancer cells demonstrate that the Anaphase Promoting Complex (APC) is impaired in MDR cells compared to normal canine control and drug-sensitive cancer cells. Here, we sought to establish whether this phenomena is a generalizable mechanism independent of species, malignancy type, or chemotherapy regime. To test the association of blunted APC activity with MDR cancer behavior, we used matched parental and MDR MCF7 human breast cancer cells, and a patient-derived xenograft (PDX) model of human triple-negative breast cancer. We show that APC activating mechanisms, such as APC subunit 1 (APC1) phosphorylation and CDC27/CDC20 protein associations, are reduced in MCF7 MDR cells when compared to chemo-sensitive matched cell lines. Consistent with impaired APC function in MDR cells, APC substrate proteins failed to be effectively degraded. Similar to our previous observations in canine MDR lymphoma cells, chemical activation of the APC using Mad2 Inhibitor-1 (M2I-1) in MCF7 MDR cells enhanced APC substrate degradation and resensitized MDR cells in vitro to the cytotoxic effects of the alkylating chemotherapeutic agent, doxorubicin (DOX). Using cell cycle arrest/release experiments, we show that mitosis is delayed in MDR cells with elevated substrate levels. When pretreated with M2I-1, MDR cells progress through mitosis at a faster rate that coincides with reduced levels of APC substrates. In our PDX model, mice growing a clinically MDR human triple-negative breast cancer tumor show significantly reduced tumor growth when treated with M2I-1, with evidence of increased DNA damage and apoptosis. Thus, our results strongly support the hypothesis that APC impairment is a driver of aggressive tumor development and that targeting the APC for activation has the potential for meaningful clinical benefits in treating recurrent cases of MDR malignancy.
    Keywords:  Anaphase Promoting Complex; PDX mouse model; cell culture; multiple-drug-resistant breast cancer
    DOI:  https://doi.org/10.3390/cancers16091755
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