bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023–01–08
eleven papers selected by
Valentina Piano, Uniklinik Köln



  1. J Biol Chem. 2022 Dec 30. pii: S0021-9258(22)01296-0. [Epub ahead of print] 102853
      The kinetochore establishes the linkage between chromosomes and the spindle microtubule plus ends during mitosis. In vertebrates, the spindle-kinetochore-associated (Ska1,2,3) complex stabilizes kinetochore attachment with the microtubule plus ends, but how Ska is recruited to and stabilized at the kinetochore-microtubule interface is not understood. Here, our results show that interaction of Ska1 with the general microtubule plus end-associated protein EB1 through a conserved motif regulates Ska recruitment to kinetochores in human cells. Ska1 forms a stable complex with EB1 via interaction with the motif in its N-terminal disordered loop region. Disruption of this interaction either by deleting or mutating the motif disrupts Ska complex recruitment to kinetochores and induce chromosome alignment defects, but it does not affect Ska complex assembly. Atomic-force microscopy imaging revealed that Ska1 is anchored to the C-terminal region of the EB1 dimer through its loop and thereby promotes formation of extended structures. Furthermore, our NMR data showed that the Ska1 motif binds to the residues in EB1 that are the binding sites of other plus end targeting proteins that are recruited to microtubules by EB1 through a similar conserved motif. Collectively, our results demonstrate that EB1-mediated Ska1 recruitment onto the microtubule serves as a general mechanism for formation of vertebrate kinetochore-microtubule attachments and metaphase chromosome alignment.
    Keywords:  +TIPs; EB1; Kinetochore; Microtubule; Mitosis; Ska1; Spindle
    DOI:  https://doi.org/10.1016/j.jbc.2022.102853
  2. Life Sci Alliance. 2023 Mar;pii: e202201807. [Epub ahead of print]6(3):
      Centromere identity is defined and maintained epigenetically by the presence of the histone variant CENP-A. How centromeric CENP-A position is specified and precisely maintained through DNA replication is not fully understood. The recently released Telomere-to-Telomere (T2T) genome assembly containing the first complete human centromere sequences provides a new resource for examining CENP-A position. Mapping CENP-A position in clones of the same cell line to the T2T assembly identified highly similar CENP-A position after multiple cell divisions. In contrast, centromeric CENP-A epialleles were evident at several centromeres of different human cell lines, demonstrating the location of CENP-A enrichment and the site of kinetochore recruitment vary among human cells. Across the cell cycle, CENP-A molecules deposited in G1 phase are maintained in their precise position through DNA replication. Thus, despite CENP-A dilution during DNA replication, CENP-A is precisely reloaded onto the same sequences within the daughter centromeres, maintaining unique centromere identity among human cells.
    DOI:  https://doi.org/10.26508/lsa.202201807
  3. Cells Tissues Organs. 2023 Jan 04.
      The initiation of apical-basal (AB) polarity and the process of mitotic cell division are both characterised by the generation of specialised plasma membrane and cortical domains. These are generated using shared mechanisms, such as asymmetric protein accumulation, Rho GTPase signalling, cytoskeletal reorganisation, vesicle trafficking and asymmetric phosphoinositide distribution. In epithelial tissue, the coordination of AB polarity and mitosis in space and time is important both during initial epithelial development and to maintain tissue integrity and ensure appropriate cell differentiation at later stages. Whilst significant progress has been made in understanding the mechanisms underlying cell division and AB polarity, it has so far been challenging to fully unpick the complex interrelationship between polarity, signalling, morphogenesis, and cell division. However, the recent emergence of optogenetic protein localisation techniques is now allowing researchers to reversibly control protein activation, localisation and signalling with high spatiotemporal resolution. This has the potential to revolutionise our understanding of how subcellular processes such as apical-basal polarity are integrated with cell behaviours such as mitosis and how these processes impact whole tissue morphogenesis. So far, these techniques have been used to investigate processes such as cleavage furrow ingression, mitotic spindle positioning, and in vivo epithelial morphogenesis. This review describes some of the key shared mechanisms of cell division and apical-basal polarity establishment, how they are coordinated during development and how the advance of optogenetic techniques is furthering this research field.
    DOI:  https://doi.org/10.1159/000528796
  4. Methods Mol Biol. 2023 ;2623 25-42
      Cytoplasmic dynein-1 is a minus end-directed microtubule motor that transports numerous cargoes in cell types throughout the evolutionary spectrum. Dynein is regulated by various motor-intrinsic and motor-extrinsic factors that enhance its processivity, recruit it to various cellular sites, or otherwise promote or restrict its activity. Studying dynein activity in higher eukaryotes is complicated by various factors, including the myriad functions in which this motor participates, and the consequential pleotropic effects associated with disrupting its activity. Budding yeast has long been a powerful model system for understanding this enormous motor protein complex, which is highly conserved between yeast and humans at the primary sequence and structural levels. Studies in budding yeast are simplified by the fact that dynein only performs one known function in this organism: to position the mitotic spindle at the site of cell division. Monitoring dynein-mediated spindle movements in budding yeast provides a powerful tool for the quantitative measurements of various motility parameters, and a system with which to assess the consequence of mutations in dynein or its regulators. Here, we provide detailed protocols to perform quantitative measurements of dynein activity in live cells using a combination of fluorescence microscopy and computational methods to track and quantitate dynein-mediated spindle movements. These methods are broadly applicable to anyone that wishes to perform fluorescence microscopy on budding yeast.
    Keywords:  Dynein; Live-cell imaging; Yeast transformation, Nuclear migration, Spindle positioning
    DOI:  https://doi.org/10.1007/978-1-0716-2958-1_2
  5. Bratisl Lek Listy. 2023 Jan 04.
      The cell cycle covers cell proliferation and growth and is strictly regulated by cyclin-dependent kinase, cyclins and their inhibitors. Cyclin-dependent kinases are serine/threonine kinases that are activated in certain phases of the cell cycle by regulatory subunits, cyclins, with which they form functional heterodimeric complexes. Under physiological conditions, the activation of cyclin-dependent kinases and cyclins is strictly controlled. The formation of these complexes is inhibited, as needed, either specifically or non-specifically, by cyclin-dependent kinase inhibitors. Progression through the cell cycle is a critical process that drives many aspects of cellular function. The cell cycle is a series of events that occurs in a repeating pattern. Each cell cycle consists of two phases, interphase and mitotic phase. Their dysregulation leads to disruption of cell cycle coordination and uncontrollable cell proliferation, which is the main feature of tumorigenesis (Fig. 1, Ref. 69). Keywords: cell cycle, regulation, cyclin‑dependent kinases, cyclins, inhibitors.
    DOI:  https://doi.org/10.4149/BLL_2023_039
  6. Commun Biol. 2023 Jan 04. 6(1): 9
      Profilin 1-encoded by PFN1-is a small actin-binding protein with a tumour suppressive role in various adenocarcinomas and pagetic osteosarcomas. However, its contribution to tumour development is not fully understood. Using fix and live cell imaging, we report that Profilin 1 inactivation results in multiple mitotic defects, manifested prominently by anaphase bridges, multipolar spindles, misaligned and lagging chromosomes, and cytokinesis failures. Accordingly, next-generation sequencing technologies highlighted that Profilin 1 knock-out cells display extensive copy-number alterations, which are associated with complex genome rearrangements and chromothripsis events in primary pagetic osteosarcomas with Profilin 1 inactivation. Mechanistically, we show that Profilin 1 is recruited to the spindle midzone at anaphase, and its deficiency reduces the supply of actin filaments to the cleavage furrow during cytokinesis. The mitotic defects are also observed in mouse embryonic fibroblasts and mesenchymal cells deriving from a newly generated knock-in mouse model harbouring a Pfn1 loss-of-function mutation. Furthermore, nuclear atypia is also detected in histological sections of mutant femurs. Thus, our results indicate that Profilin 1 has a role in regulating cell division, and its inactivation triggers mitotic defects, one of the major mechanisms through which tumour cells acquire chromosomal instability.
    DOI:  https://doi.org/10.1038/s42003-022-04392-8
  7. J Cell Sci. 2023 Jan 01. pii: jcs260103. [Epub ahead of print]136(1):
      Cancer cells have heterogeneous fitness, and this heterogeneity stems from genetic and epigenetic sources. Here, we sought to assess the contribution of asymmetric mitosis (AM) and time on the variability of fitness in sister cells. Around one quarter of sisters had differences in fitness, assessed as the intermitotic time (IMT), from 330 to 510 min. Phenotypes related to fitness, such as ERK activity (herein referring to ERK1 and ERK2, also known as MAPK3 and MAPK1, respectively), DNA damage and nuclear morphological phenotypes were also asymmetric at mitosis or turned asymmetric over the course of the cell cycle. The ERK activity of mother cell was found to influence the ERK activity and the IMT of the daughter cells, and cells with ERK asymmetry at mitosis produced more offspring with AMs, suggesting heritability of the AM phenotype for ERK activity. Our findings demonstrate how variabilities in sister cells can be generated, contributing to the phenotype heterogeneities in tumor cells.
    Keywords:  Asymmetric mitosis; ERK activity; Fitness; Heritability; Mother cell; Sister cells
    DOI:  https://doi.org/10.1242/jcs.260103
  8. Methods Mol Biol. 2023 ;2623 73-85
      Several light-inducible hetero-dimerization tools have been developed to spatiotemporally control subcellular localization and activity of target proteins or their downstream signaling. In contrast to other genetic technologies, such as CRISPR-mediated genome editing, these optogenetic tools can locally control protein localization on the second timescale. In addition, these tools can be used to understand the sufficiency of target proteins' function and manipulate downstream events. In this chapter, I will present methods for locally activating cytoplasmic dynein at the mitotic cell cortex in human cells, with a focus on how to generate knock-in cell lines and set up a microscope system.
    Keywords:  CRISPR/Cas9; Light-inducible dimerization; Metamorph; Mosaic 3 light-illumination device; NuMA; iLID
    DOI:  https://doi.org/10.1007/978-1-0716-2958-1_5
  9. J Vet Med Sci. 2022 Dec 30.
      Inflammatory bowel disease (IBD) is classified into two types: Crohn's disease and ulcerative colitis. In IBD, the imbalance between the pro-inflammatory and anti-inflammatory cytokines prevents recovery from the inflammatory state, resulting in chronic inflammation in the colon. The mitotic spindle positioning protein (MISP) is localized to the apical membrane in the colon. In this study, we observed increased expression of MISP in the intestinal epithelial cells in dextran sulfate sodium (DSS)-induced colitis in mice. MISP-deficient mice receiving DSS showed significant exacerbation of colitis (e.g., weight loss, loss of the crypts). The intestinal epithelial cells of the MISP-deficient mice showed a trend towards decreased cell proliferation after DSS treatment. Reverse transcription followed by quantitative polymerase chain reaction revealed that the expression levels of Tgfb1, an anti-inflammatory cytokine, were significantly reduced in the colon of MISP-deficient mice compared with the wild-type mice regardless of DSS treatment. These findings indicate that MISP may play a role in the recovery of the colon after inflammation through its anti-inflammatory and proliferative activities, suggesting that MISP may be a new therapeutic target for IBD.
    Keywords:  dextran sulfate sodium-induced colitis; inflammatory bowel disease; inflammatory cytokines; mitotic spindle positioning protein
    DOI:  https://doi.org/10.1292/jvms.22-0483
  10. Sci Adv. 2023 Jan 04. 9(1): eabq5404
      CLASPs (cytoplasmic linker-associated proteins) are ubiquitous stabilizers of microtubule dynamics, but their molecular targets at the microtubule plus-end are not understood. Using DNA origami-based reconstructions, we show that clusters of human CLASP2 form a load-bearing bond with terminal non-GTP tubulins at the stabilized microtubule tip. This activity relies on the unconventional TOG2 domain of CLASP2, which releases its high-affinity bond with non-GTP dimers upon their conversion into polymerization-competent GTP-tubulins. The ability of CLASP2 to recognize nucleotide-specific tubulin conformation and stabilize the catastrophe-promoting non-GTP tubulins intertwines with the previously underappreciated exchange between GDP and GTP at terminal tubulins. We propose that TOG2-dependent stabilization of sporadically occurring non-GTP tubulins represents a distinct molecular mechanism to suppress catastrophe at the freely assembling microtubule ends and to promote persistent tubulin assembly at the load-bearing tethered ends, such as at the kinetochores in dividing cells.
    DOI:  https://doi.org/10.1126/sciadv.abq5404
  11. STAR Protoc. 2023 Jan 03. pii: S2666-1667(22)00850-4. [Epub ahead of print]4(1): 101970
      Cells experiencing DNA replication stress enter mitosis with under-replicated DNA, which activates a repair mechanism known as mitotic DNA synthesis (MiDAS). Here we describe a protocol to identify at genome wide and at high resolution the genomic sites where MiDAS occurs in cells exposed to aphidicolin. We use EdU incorporation to label nascent DNA in mitotic cells, followed by isolation of the EdU-labeled DNA and next-generation sequencing. For complete details on the use and execution of this protocol, please refer to Groelly et al. (2022)1 and Macheret et al. (2020).2.
    Keywords:  Cell Biology; Cell culture; ChIPseq; Molecular Biology; Sequencing
    DOI:  https://doi.org/10.1016/j.xpro.2022.101970