bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023–07–23
eight papers selected by
Valentina Piano, Uniklinik Köln
  1. Twenty years of merotelic kinetochore attachments: a historical perspective.
  2. Editorial: Chromosome bi-orientation, tension and the spindle-assembly checkpoint.
  3. MTA1 localizes to the mitotic spindle apparatus and interacts with TPR in spindle assembly checkpoint regulation.
  4. A dual-function SNF2 protein drives chromatid resolution and nascent transcripts removal in mitosis.
  5. CAMK2D serves as a molecular scaffold for RNF8-MAD2 complex to induce mitotic checkpoint in glioma.
  6. BI6727 and GSK461364A, potent PLK1 inhibitors induce G2/M arrest and apoptosis against cholangiocarcinoma cell lines.
  7. Mechanisms of nuclear pore complex disassembly by the mitotic Polo-like kinase 1 (PLK-1) in C. elegans embryos.
  8. Super-resolution microscopy reveals focal organization of ER-associated Y-complexes in mitosis.
  1. Chromosome Res. 2023 Jul 19. 31(3): 18
    Twenty years of merotelic kinetochore attachments: a historical perspective.
    Daniela Cimini.
      Micronuclei, small DNA-containing structures separate from the main nucleus, were used for decades as an indicator of genotoxic damage. Micronuclei containing whole chromosomes were considered a biomarker of aneuploidy and were believed to form, upon mitotic exit, from chromosomes that lagged behind in anaphase as all other chromosomes segregated to the poles of the mitotic spindle. However, the mechanism responsible for inducing anaphase lagging chromosomes remained unknown until just over twenty years ago. Here, I summarize what preceded and what followed this discovery, highlighting some of the open questions and opportunities for future investigation.
    Keywords:  chromosome segregation; lagging chromosome; merotelic; micronuclei; mitosis
    DOI:  https://doi.org/10.1007/s10577-023-09727-7
  2. Front Cell Dev Biol. 2023 ;11 1245368
    Editorial: Chromosome bi-orientation, tension and the spindle-assembly checkpoint.
    Scott C Schuyler.
      
    Keywords:  aurora kinase; chromosomes; mitosis; spindle checkpoint; tension
    DOI:  https://doi.org/10.3389/fcell.2023.1245368
  3. Biochem Biophys Res Commun. 2023 Jul 13. pii: S0006-291X(23)00878-1. [Epub ahead of print]675 106-112
    MTA1 localizes to the mitotic spindle apparatus and interacts with TPR in spindle assembly checkpoint regulation.
    Jian Liu, Hongsheng Xue, Chunxiao Li, Xiangyu Chen, Jiannan Yao, Dongkui Xu, Haili Qian.
      We previously identified a cell cycle-dependent periodic subcellular distribution of cancer metastasis-associated antigen 1 (MTA1) and unraveled a novel role of MTA1 in inhibiting spindle damage-induced spindle assembly checkpoint (SAC) activation in cancer cells. However, the more detailed subcellular localization of MTA1 in mitotic cells and its copartner in SAC regulation in cancer cells are still poorly understood. Here, through immunofluorescent colocalization analysis of MTA1 and alpha-tubulin in mitotic cancer cells, we reveal that MTA1 is dynamically localized to the spindle apparatus throughout the entire mitotic process. We also demonstrated a reversible upregulation of MTA1 expression upon spindle damage-induced SAC activation, and time-lapse imaging assays indicated that MTA1 silencing delayed the mitotic metaphase-anaphase transition in cancer cells. Further investigation revealed that MTA1 interacts and colocalizes with Translocated Promoter Region (TPR) on spindle microtubules in mitotic cells, and this interaction is attenuated on SAC activation. TPR is well-implicated in SAC regulation via binding the MAD1-MAD2 complex, however, no interactions between MTA1 and MAD1 or MAD2 were detected in our coimmunoprecipitation (co-IP) assays, suggesting that the MTA1-TPR may represent a distinct SAC-associated complex separate from the previously reported TPR-MAD1/MAD2 complex. Our data provide new insights into the subcellular localization and molecular function of MTA1 in SAC regulation in cancer, and indicate that intervention of the MTA1-TPR interaction may be effective to modulate SAC and hence chromosomal instability (CIN) in tumorigenesis.
    Keywords:  Cancer; MTA1; Spindle apparatus; Spindle assembly checkpoint; TPR
    DOI:  https://doi.org/10.1016/j.bbrc.2023.07.021
  4. EMBO Rep. 2023 Jul 18. e56463
    A dual-function SNF2 protein drives chromatid resolution and nascent transcripts removal in mitosis.
    Catarina Carmo, João Coelho, Rui D Silva, Alexandra Tavares, Ana Boavida, Paola Gaetani, Leonardo G Guilgur, Rui Gonçalo Martinho, Raquel A Oliveira.
      Mitotic chromatin is largely assumed incompatible with transcription due to changes in the transcription machinery and chromosome architecture. However, the mechanisms of mitotic transcriptional inactivation and their interplay with chromosome assembly remain largely unknown. By monitoring ongoing transcription in Drosophila early embryos, we reveal that eviction of nascent mRNAs from mitotic chromatin occurs after substantial chromosome compaction and is not promoted by condensin I. Instead, we show that the timely removal of transcripts from mitotic chromatin is driven by the SNF2 helicase-like protein Lodestar (Lds), identified here as a modulator of sister chromatid cohesion defects. In addition to the eviction of nascent transcripts, we uncover that Lds cooperates with Topoisomerase 2 to ensure efficient sister chromatid resolution and mitotic fidelity. We conclude that the removal of nascent transcripts upon mitotic entry is not a passive consequence of cell cycle progression and/or chromosome compaction but occurs via dedicated mechanisms with functional parallelisms to sister chromatid resolution.
    Keywords:  SNF2 family; cohesin; condensin; mitotic transcription; topoisomerase 2
    DOI:  https://doi.org/10.15252/embr.202256463
  5. Cell Death Differ. 2023 Jul 19.
    CAMK2D serves as a molecular scaffold for RNF8-MAD2 complex to induce mitotic checkpoint in glioma.
    You Heng Chuah, Emmy Xue Yun Tay, Oleg V Grinchuk, Jeehyun Yoon, Jia Feng, Srinivasaraghavan Kannan, Matius Robert, Rekha Jakhar, Yajing Liang, Bernice Woon Li Lee, Loo Chien Wang, Yan Ting Lim, Tianyun Zhao, Radoslaw M Sobota, Guang Lu, Boon Chuan Low, Karen Carmelina Crasta, Chandra Shekhar Verma, Zhewang Lin, Derrick Sek Tong Ong.
      MAD2 is a spindle assembly checkpoint protein that participates in the formation of mitotic checkpoint complex, which blocks mitotic progression. RNF8, an established DNA damage response protein, has been implicated in mitotic checkpoint regulation but its exact role remains poorly understood. Here, RNF8 proximity proteomics uncovered a role of RNF8-MAD2 in generating the mitotic checkpoint signal. Specifically, RNF8 competes with a small pool of p31comet for binding to the closed conformer of MAD2 via its RING domain, while CAMK2D serves as a molecular scaffold to concentrate the RNF8-MAD2 complex via transient/weak interactions between its p-Thr287 and RNF8's FHA domain. Accordingly, RNF8 overexpression impairs glioma stem cell (GSC) mitotic progression in a FHA- and RING-dependent manner. Importantly, low RNF8 expression correlates with inferior glioma outcome and RNF8 overexpression impedes GSC tumorigenicity. Last, we identify PLK1 inhibitor that mimics RNF8 overexpression using a chemical biology approach, and demonstrate a PLK1/HSP90 inhibitor combination that synergistically reduces GSC proliferation and stemness. Thus, our study has unveiled a previously unrecognized CAMK2D-RNF8-MAD2 complex in regulating mitotic checkpoint with relevance to gliomas, which is therapeutically targetable.
    DOI:  https://doi.org/10.1038/s41418-023-01192-3
  6. Pathol Res Pract. 2023 Jul 08. pii: S0344-0338(23)00378-3. [Epub ahead of print]248 154678
    BI6727 and GSK461364A, potent PLK1 inhibitors induce G2/M arrest and apoptosis against cholangiocarcinoma cell lines.
    Handy Riantana, Orawan Waenphimai, Panupong Mahalapbutr, Kun Karnchanapandh, Kulthida Vaeteewoottacharn, Sopit Wongkham, Kanlayanee Sawanyawisuth.
      Polo-like kinase 1 (PLK1) is an essential mitotic checkpoint protein that plays a key role in cell cycle division. Overexpression of PLK1 has been associated with poor prognosis in various cancers. Cholangiocarcinoma (CCA) is a lethal bile duct cancer and the current treatments in inoperable patients have not been satisfactory. In order to develop novel targeted therapies, we investigated the efficacy of BI6727 (volasertib) and GSK461364A, polo-like kinase 1 (PLK1) inhibitors in KKU-100 and KKU-213A CCA cell lines. PLK1 expression was significantly up-regulated in CCA cases compared with normal tissues based on the results derived from GEPIA. Western blot results exhibited PLK1 protein expression in both CCA cell lines. Molecular dynamics simulations and free energy calculations based on MM/GBSA method revealed that BI6727-PLK1 and GSK461364A-PLK1 complexes were stable in an aqueous environment, and their complexation was mainly driven by Van der Waals interaction. BI6727 and GSK461364A clearly suppressed CCA cell proliferation and induced G2/M arrest, accompanied with upregulation of cyclin B1 and phosphorylated Histone H3 at Ser10 (pS10H3), specific markers of mitosis. Furthermore, both compounds triggered mitotic catastrophe followed by cell apoptosis via activation of PARP and Caspase 3, as well as downregulation of Mcl-1 anti-apoptotic protein in both CCA cell lines. In conclusion, pharmacologic PLK1 inhibition by BI6727 and GSK461364A blocked survival of CCA cells by several mechanisms. Our study provides evidence that BI6727 and GSK461364A could be alternative drugs and have potential implications at the clinical level for CCA therapy.
    Keywords:  Apoptosis; BI6727; Cholangiocarcinoma; GSK461364A; Mitotic catastrophe; PLK1; Volasertib
    DOI:  https://doi.org/10.1016/j.prp.2023.154678
  7. Sci Adv. 2023 Jul 21. 9(29): eadf7826
    Mechanisms of nuclear pore complex disassembly by the mitotic Polo-like kinase 1 (PLK-1) in C. elegans embryos.
    Sylvia Nkombo Nkoula, Griselda Velez-Aguilera, Batool Ossareh-Nazari, Lucie Van Hove, Cristina Ayuso, Véronique Legros, Guillaume Chevreux, Laura Thomas, Géraldine Seydoux, Peter Askjaer, Lionel Pintard.
      The nuclear envelope, which protects and organizes the genome, is dismantled during mitosis. In the Caenorhabditis elegans zygote, nuclear envelope breakdown (NEBD) of the parental pronuclei is spatially and temporally regulated during mitosis to promote the unification of the maternal and paternal genomes. Nuclear pore complex (NPC) disassembly is a decisive step of NEBD, essential for nuclear permeabilization. By combining live imaging, biochemistry, and phosphoproteomics, we show that NPC disassembly is a stepwise process that involves Polo-like kinase 1 (PLK-1)-dependent and -independent steps. PLK-1 targets multiple NPC subcomplexes, including the cytoplasmic filaments, central channel, and inner ring. PLK-1 is recruited to and phosphorylates intrinsically disordered regions (IDRs) of several multivalent linker nucleoporins. Notably, although the phosphosites are not conserved between human and C. elegans nucleoporins, they are located in IDRs in both species. Our results suggest that targeting IDRs of multivalent linker nucleoporins is an evolutionarily conserved driver of NPC disassembly during mitosis.
    DOI:  https://doi.org/10.1126/sciadv.adf7826
  8. EMBO Rep. 2023 Jul 20. e56766
    Super-resolution microscopy reveals focal organization of ER-associated Y-complexes in mitosis.
    Rojapriyadharshini Gandhimathi, Dorothea Pinotsi, Mario Köhler, Jörg Mansfeld, Caroline Ashiono, Tatjana Kleele, Sumit Pawar, Ulrike Kutay.
      During mitotic entry of vertebrate cells, nuclear pore complexes (NPCs) are rapidly disintegrated. NPC disassembly is initiated by hyperphosphorylation of linker nucleoporins (Nups), which leads to the dissociation of FG repeat Nups and relaxation of the nuclear permeability barrier. However, less is known about disintegration of the huge nuclear and cytoplasmic rings, which are formed by annular assemblies of Y-complexes that are dissociated from NPCs as intact units. Surprisingly, we observe that Y-complex Nups display slower dissociation kinetics compared with other Nups during in vitro NPC disassembly, indicating a mechanistic difference in the disintegration of Y-based rings. Intriguingly, biochemical experiments reveal that a fraction of Y-complexes remains associated with mitotic ER membranes, supporting recent microscopic observations. Visualization of mitotic Y-complexes by super-resolution microscopy demonstrates that they form two classes of higher order assemblies: large clusters at kinetochores and small, focal ER-associated assemblies. These, however, lack features qualifying them as persisting ring-shaped subassemblies previously proposed to serve as structural templates for NPC reassembly during mitotic exit, which helps to refine current models of nuclear reassembly.
    Keywords:  NPC disassembly; Y-complex; mitosis; nuclear pore complex; nucleoporin
    DOI:  https://doi.org/10.15252/embr.202356766
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