bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023‒05‒14
nine papers selected by
Valentina Piano
Uniklinik Köln
  1. A mechanism that integrates microtubule motors of opposite polarity at the kinetochore corona.
  2. Robust microtubule dynamics facilitate low-tension kinetochore detachment in metaphase.
  3. Regulation of intestinal stem cell activity by a mitotic cell cycle regulator Polo in Drosophila.
  4. The histone methyltransferase NSD3 contributes to sister chromatid cohesion and to cohesin loading at mitotic exit.
  5. Mitotic clustering of pulverized chromosomes from micronuclei.
  6. Polo-like kinase 4 homodimerization and condensate formation regulate its own protein levels but are not required for centriole assembly.
  7. Mitotic rate in primary cutaneous melanoma: Cell division matters.
  8. Confinement plus Myosin-II suppression maximizes heritable loss of chromosomes, as revealed by live-cell ChReporters.
  9. Caspase cleaves Drosophila BubR1 to modulate spindle assembly checkpoint function and lifespan of the organism.
  1. bioRxiv. 2023 Apr 25. pii: 2023.04.25.538277. [Epub ahead of print]
    A mechanism that integrates microtubule motors of opposite polarity at the kinetochore corona.
    Verena Cmentowski, Giuseppe Ciossani, Ennio d'Amico, Sabine Wohlgemuth, Mikito Owa, Brian Dynlacht, Andrea Musacchio.
      Chromosome biorientation on the mitotic spindle is prerequisite to errorless genome inheritance. CENP-E (kinesin 7) and Dynein-Dynactin (DD), microtubule motors with opposite polarity, promote biorientation from the kinetochore corona, a polymeric structure whose assembly requires MPS1 kinase. The corona's building block consists of ROD, Zwilch, ZW10, and the DD adaptor Spindly (RZZS). How CENP-E and DD are scaffolded and mutually coordinated in the corona remains unclear. Here, we report near-complete depletion of RZZS and DD from kinetochores after depletion of CENP-E and the outer kinetochore protein KNL1. With inhibited MPS1, CENP-E, which we show binds directly to RZZS, is required to retain kinetochore RZZS. An RZZS phosphomimetic mutant bypasses this requirement. With active MPS1, CENP-E is dispensable for corona expansion, but strictly required for physiological kinetochore accumulation of DD. Thus, we identify the corona as an integrated scaffold where CENP-E kinesin controls DD kinetochore loading for coordinated bidirectional transport of chromosome cargo.
    DOI:  https://doi.org/10.1101/2023.04.25.538277
  2. J Cell Biol. 2023 Aug 07. pii: e202202085. [Epub ahead of print]222(8):
    Robust microtubule dynamics facilitate low-tension kinetochore detachment in metaphase.
    Sneha Parmar, Samuel J Gonzalez, Julia M Heckel, Soumya Mukherjee, Mark McClellan, Duncan J Clarke, Marnie Johansson, Damien Tank, Athena Geisness, David K Wood, Melissa K Gardner.
      During mitosis, sister chromatids are stretched apart at their centromeres via their attachment to oppositely oriented kinetochore microtubules. This stretching generates inwardly directed tension across the separated sister centromeres. The cell leverages this tension signal to detect and then correct potential errors in chromosome segregation, via a mechanical tension signaling pathway that detaches improperly attached kinetochores from their microtubules. However, the sequence of events leading up to these detachment events remains unknown. In this study, we used microfluidics to sustain and observe low-tension budding yeast metaphase spindles over multiple hours, allowing us to elucidate the tension history prior to a detachment event. We found that, under conditions in which kinetochore phosphorylation weakens low-tension kinetochore-microtubule connections, the mechanical forces produced via the dynamic growth and shortening of microtubules is required to efficiently facilitate detachment events. Our findings underscore the critical role of robust kinetochore microtubule dynamics in ensuring the fidelity of chromosome segregation during mitosis.
    DOI:  https://doi.org/10.1083/jcb.202202085
  3. G3 (Bethesda). 2023 May 08. pii: jkad084. [Epub ahead of print]
    Regulation of intestinal stem cell activity by a mitotic cell cycle regulator Polo in Drosophila.
    Ying Zhang, Rongbing Chen, Liyuan Gong, Wuren Huang, Ping Li, Zongzhao Zhai, Erjun Ling.
      Maintaining a definite and stable pool of dividing stem cells plays an important role in organ development. This process requires an appropriate progression of mitosis for proper spindle orientation and polarity to ensure the ability of stem cells to proliferate and differentiate correctly. Polo-like kinases (Plks)/Polo are the highly conserved serine/threonine kinases involved in the initiation of mitosis as well as in the progression of the cell cycle. Although numerous studies have investigated the mitotic defects upon loss of Plks/Polo in cells, little is known about the in vivo consequences of stem cells with abnormal Polo activity in the context of tissue and organism development. The current study aimed to investigate this question using the Drosophila intestine, an organ dynamically maintained by the intestinal stem cells (ISCs). The results indicated that the polo depletion caused a reduction in the gut size due to a gradual decrease in the number of functional ISCs. Interestingly, the polo-deficient ISCs showed an extended G2/M phase and aneuploidy and were subsequently eliminated by premature differentiation into enterocytes (ECs). In contrast, the constitutively active Polo (poloT182D) suppressed ISC proliferation, induced abnormal accumulation of β-tubulin in cells, and drove ISC loss via apoptosis. Therefore, Polo activity should be properly maintained for optimal stem cell function. Further analysis suggested that polo was a direct target gene of Sox21a, a Sox transcription factor that critically regulates stem cell activity. Together, this study provided a novel perspective on the correlation between the progression of mitosis and the ISC function in Drosophila.
    Keywords:  Polo; aneuploidy; apoptosis; differentiation; intestinal stem cell; mitosis
    DOI:  https://doi.org/10.1093/g3journal/jkad084
  4. J Cell Sci. 2023 May 09. pii: jcs.261014. [Epub ahead of print]
    The histone methyltransferase NSD3 contributes to sister chromatid cohesion and to cohesin loading at mitotic exit.
    Grégory Eot-Houllier, Laura Magnaghi-Jaulin, Gaëlle Bourgine, Fatima Smagulova, Régis Giet, Erwan Watrin, Christian Jaulin.
      Sister chromatid cohesion is a multi-step process implemented throughout the cell cycle to ensure the correct transmission of chromosomes to daughter cells. While cohesion establishment and mitotic cohesion dissolution have been extensively explored, the regulation of cohesin loading is still poorly understood. Here, we report that the methyltransferase NSD3 is essential for mitotic sister chromatid cohesion before mitosis entry. NSD3 interacts with the cohesin loader complex kollerin (NIPBL/MAU2) and promotes the chromatin recruitment of MAU2 and cohesin at mitotic exit. We also show that NSD3 associates with chromatin in early anaphase, prior to the recruitment of MAU2 and RAD21, and dissociates from chromatin when prophase begins. Among the two NSD3 isoforms present in somatic cells, the long isoform is responsible for regulating kollerin and cohesin chromatin-loading, and its methyltransferase activity is required for efficient sister chromatid cohesion. Based on these observations, we propose that NSD3-dependent methylation contributes to sister chromatid cohesion by ensuring proper kollerin recruitment and thus cohesin loading.
    Keywords:  Cohesin; MAU2; Methylation; Mitosis; NIPBL; NSD3
    DOI:  https://doi.org/10.1242/jcs.261014
  5. Nature. 2023 May 10.
    Mitotic clustering of pulverized chromosomes from micronuclei.
    Yu-Fen Lin, Qing Hu, Alice Mazzagatti, Jose Espejo Valle-Inclán, Elizabeth G Maurais, Rashmi Dahiya, Alison Guyer, Jacob T Sanders, Justin L Engel, Giaochau Nguyen, Daniel Bronder, Samuel F Bakhoum, Isidro Cortés-Ciriano, Peter Ly.
      Complex genome rearrangements can be generated by the catastrophic pulverization of missegregated chromosomes trapped within micronuclei through a process known as chromothripsis1-5. As each chromosome contains a single centromere, it remains unclear how acentric fragments derived from shattered chromosomes are inherited between daughter cells during mitosis6. Here we tracked micronucleated chromosomes with live-cell imaging and show that acentric fragments cluster in close spatial proximity throughout mitosis for asymmetric inheritance by a single daughter cell. Mechanistically, the CIP2A-TOPBP1 complex prematurely associates with DNA lesions within ruptured micronuclei during interphase, which poises pulverized chromosomes for clustering upon mitotic entry. Inactivation of CIP2A-TOPBP1 caused acentric fragments to disperse throughout the mitotic cytoplasm, stochastically partition into the nucleus of both daughter cells and aberrantly misaccumulate as cytoplasmic DNA. Mitotic clustering facilitates the reassembly of acentric fragments into rearranged chromosomes lacking the extensive DNA copy-number losses that are characteristic of canonical chromothripsis. Comprehensive analysis of pan-cancer genomes revealed clusters of DNA copy-number-neutral rearrangements-termed balanced chromothripsis-across diverse tumour types resulting in the acquisition of known cancer driver events. Thus, distinct patterns of chromothripsis can be explained by the spatial clustering of pulverized chromosomes from micronuclei.
    DOI:  https://doi.org/10.1038/s41586-023-05974-0
  6. Mol Biol Cell. 2023 May 10. mbcE22120572
    Polo-like kinase 4 homodimerization and condensate formation regulate its own protein levels but are not required for centriole assembly.
    John M Ryniawec, Daniel W Buster, Lauren K Slevin, Cody J Boese, Anastasia Amoiroglou, Spencer M Dean, Kevin C Slep, Gregory C Rogers.
      Polo-like kinase 4 (Plk4) is the master-regulator of centriole assembly and cell cycle-dependent regulation of its activity maintains proper centrosome number. During most of the cell cycle, Plk4 levels are nearly undetectable due to its ability to autophosphorylate and trigger its own ubiquitin-mediated degradation. However, during mitotic exit, Plk4 forms a single aggregate on the centriole surface to stimulate centriole duplication. Whereas most Polo-like kinase family members are monomeric, Plk4 is unique because it forms homodimers. Notably, Plk4 trans-autophosphorylates a degron near its kinase domain, a critical step in autodestruction. While it is thought that the purpose of homodimerization is to promote trans-autophosphorylation, this has not been tested. Here, we generated separation-of-function Plk4 mutants that fail to dimerize and show that homodimerization creates a binding site for the Plk4 activator, Asterless. Surprisingly however, Plk4 dimer mutants are catalytically-active in cells, promote centriole assembly, and can trans-autophosphorylate through concentration-dependent condensate formation. Moreover, we mapped and then deleted the weak-interacting regions within Plk4 that mediate condensation and conclude that dimerization and condensation are not required for centriole assembly. Our findings suggest that Plk4 dimerization and condensation function simply to downregulate Plk4 and suppress centriole overduplication. [Media: see text].
    DOI:  https://doi.org/10.1091/mbc.E22-12-0572
  7. Cancer. 2023 May 10.
    Mitotic rate in primary cutaneous melanoma: Cell division matters.
    Jeffrey E Gershenwald.
      
    DOI:  https://doi.org/10.1002/cncr.34825
  8. J Cell Sci. 2023 May 09. pii: jcs.260753. [Epub ahead of print]
    Confinement plus Myosin-II suppression maximizes heritable loss of chromosomes, as revealed by live-cell ChReporters.
    Brandon H Hayes, Peter Kuangzheng Zhu, Mai Wang, Charlotte R Pfeifer, Yuntao Xia, Steven Phan, Jason C Andrechak, Junhong Du, Michael P Tobin, Alisya Anlas, Lawrence J Dooling, Manasvita Vashisth, Jerome Irianto, Michael A Lampson, Dennis E Discher.
      A cell's mechanical environment can have many effects, but whether it impacts a cell's DNA sequence has remained unclear. To investigate this, we developed a live-cell method to measure changes in chromosome numbers. We edited constitutive genes with GFP/RFP-tags on single alleles and discovered that cells that lose Chromosome-reporters (ChReporters) become non-fluorescent. We applied our new tools to confined mitosis and to inhibition of the putative tumor suppressor Myosin-II. We quantified compression of mitotic chromatin in vivo and demonstrated that similar compression in vitro resulted in cell death, but also rare and heritable ChReptorter loss. Myosin-II suppression rescued lethal multipolar divisions and maximized ChReporter loss in 3D-compression and 2D-confinement, but not in standard 2D-culture. ChReporter loss associated with chromosome mis-segregation, rather than just the number of divisions, and loss in vitro and in mice was selected against in subsequent 2D-cultures. Inhibition of the spindle assembly checkpoint (SAC) caused ChReporter loss in 2D, as expected, but not in 3D-compression, suggesting a SAC perturbation. Thus, confinement and myosin-II affect DNA sequence and mechano-evolution, and ChReporters enable diverse studies of viable genetic changes.
    Keywords:  Aneuploidy; Compression; Confinement; Heritability; Myosin; Rigidity
    DOI:  https://doi.org/10.1242/jcs.260753
  9. FEBS J. 2023 May 07.
    Caspase cleaves Drosophila BubR1 to modulate spindle assembly checkpoint function and lifespan of the organism.
    Natsuki Shinoda, Misuzu Horikoshi, Yusuke Taira, Masaya Muramoto, Shoshiro Hirayama, Shigeo Murata, Masayuki Miura.
      Caspases cleave over 1,500 substrates in the human proteome in both lethal and non-lethal scenarios. However, reports of the physiological consequences of substrate cleavage are limited. Additionally, the manner in which caspase cleaves only a subset of substrates in the non-lethal scenario remains to be elucidated. BubR1, a spindle assembly checkpoint component, is a caspase substrate in humans, the physiological function of which remains unclear. Here, we found that caspases, especially Drice, cleave Drosophila BubR1 between the N-terminal KEN box motif and C-terminal kinase domain. By using proximity labelling, we found that Drice, but not Dcp-1, is in proximity to BubR1, suggesting that protein proximity facilitates substrate preference. The cleaved fragments displayed, altered subcellular localization and protein-protein interactions. Flies that harbored cleavage-resistant BubR1 showed longer duration of BubR1 localization to the kinetochore upon colchicine treatment. Furthermore, these flies showed extended lifespan. Thus, we propose that the caspase-mediated cleavage of BubR1 limits spindle assembly checkpoint and organismal lifespan. Our results highlight the importance of the individual analysis of substrates in vivo to determine the biological significance of caspase-dependent non-lethal cellular processes.
    Keywords:  BubR1; Caspase; Drosophila; TurboID; aging
    DOI:  https://doi.org/10.1111/febs.16811
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