bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023–08–27
eight papers selected by
Valentina Piano, Uniklinik Köln
  1. An Aurora kinase A-BOD1L1-PP2A B56 Axis promotes chromosome segregation fidelity.
  2. Nucleolin is required for multiple centrosome-associated functions in early vertebrate mitosis.
  3. Cyclin B3 is a dominant fast-acting cyclin that drives rapid early embryonic mitoses.
  4. The minus-end depolymerase KIF2A drives flux-like treadmilling of γTuRC-uncapped microtubules.
  5. Delineation of the CENP-LN sub-complex dissociation mechanism upon multisite phosphorylation during mitosis.
  6. Perspectives and mechanisms for targeting mitotic catastrophe in cancer treatment.
  7. Specific inhibition of an anticancer target, polo-like kinase 1, by allosterically dismantling its mechanism of substrate recognition.
  8. Non-homologous end joining shapes the genomic rearrangement landscape of chromothripsis from mitotic errors.
  1. bioRxiv. 2023 Aug 07. pii: 2023.08.06.552174. [Epub ahead of print]
    An Aurora kinase A-BOD1L1-PP2A B56 Axis promotes chromosome segregation fidelity.
    Thomas J Kucharski, Irma M Vlasac, Martin R Higgs, Brock C Christensen, Duane A Compton.
      Cancer cells are often aneuploid and frequently display elevated rates of chromosome mis-segregation in a phenomenon called chromosomal instability (CIN). CIN is commonly caused by hyperstable kinetochore-microtubule (K-MT) attachments that reduces the efficiency of correction of erroneous K-MT attachments. We recently showed that UMK57, a chemical agonist of MCAK (alias KIF2C), improves chromosome segregation fidelity in CIN cancer cells but that cells rapidly develop resistance to UMK57. To determine the mechanism of resistance we performed unbiased proteomic screens which revealed increased phosphorylation in cells adapted to UMK57 at two Aurora kinase A phosphoacceptor sites on BOD1L1 (alias FAM44A). BOD1L1 depletion or Aurora kinase A inhibition eliminated resistance to UMK57 in CIN cancer cells. BOD1L1 localizes to spindles/kinetochores during mitosis, interacts with the PP2A phosphatase, and regulates phosphorylation levels of kinetochore proteins, chromosome alignment, mitotic progression, and fidelity. Moreover, the BOD1L1 gene is mutated in a subset of human cancers, and BOD1L1 depletion reduces cell growth in combination with low doses of taxol or Aurora kinase A inhibitor. Thus, an Aurora kinase A -BOD1L1-PP2A axis promotes faithful chromosome segregation during mitosis.
    DOI:  https://doi.org/10.1101/2023.08.06.552174
  2. Chromosoma. 2023 Aug 24.
    Nucleolin is required for multiple centrosome-associated functions in early vertebrate mitosis.
    Chandan Kumar, Sivaram V S Mylavarapu.
      Nucleolin is a multifunctional RNA-binding protein that resides predominantly not only in the nucleolus, but also in multiple other subcellular pools in the cytoplasm in mammalian cells, and is best known for its roles in ribosome biogenesis, RNA stability, and translation. During early mitosis, nucleolin is required for equatorial mitotic chromosome alignment prior to metaphase. Using high resolution fluorescence imaging, we reveal that nucleolin is required for multiple centrosome-associated functions at the G2-prophase boundary. Nucleolin depletion led to dissociation of the centrosomes from the G2 nuclear envelope, a delay in the onset of nuclear envelope breakdown, reduced inter-centrosome separation, and longer metaphase spindles. Our results reveal novel roles for nucleolin in early mammalian mitosis, establishing multiple important functions for nucleolin during mammalian cell division.
    Keywords:  Centrosome; Dynein; Mitosis; Mitotic spindle; Nuclear envelope; Nucleolin
    DOI:  https://doi.org/10.1007/s00412-023-00808-4
  3. bioRxiv. 2023 Aug 11. pii: 2023.08.11.553011. [Epub ahead of print]
    Cyclin B3 is a dominant fast-acting cyclin that drives rapid early embryonic mitoses.
    Pablo Lara-Gonzalez, Smriti Variyar, Jacqueline Budrewicz, Aleesa Schlientz, Neha Varshney, Andrew Bellaart, Shabnam Moghareh, Anh Cao Ngoc Nguyen, Karen Oegema, Arshad Desai.
      In many species, early embryonic mitoses proceed at a very rapid pace, but how this pace is achieved is not understood. Here we show that in the early C. elegans embryo, cyclin B3 is the dominant driver of rapid embryonic mitoses. Metazoans typically have three cyclin B isoforms that associate with and activate Cdk1 kinase to orchestrate mitotic events: the related cyclins B1 and B2 and the more divergent cyclin B3. We show that whereas embryos expressing cyclins B1 and B2 support slow mitosis (NEBD to Anaphase ∼ 600s), the presence of cyclin B3 dominantly drives the ∼3-fold faster mitosis observed in wildtype embryos. CYB-1/2-driven mitosis is longer than CYB-3-driven mitosis primarily because the progression of mitotic events itself is slower, rather than delayed anaphase onset due to activation of the spindle checkpoint or inhibitory phosphorylation of the anaphase activator CDC-20. Addition of cyclin B1 to cyclin B3-only mitosis introduces an ∼60s delay between the completion of chromosome alignment and anaphase onset, which likely ensures segregation fidelity; this delay is mediated by inhibitory phosphorylation on CDC-20. Thus, the dominance of cyclin B3 in driving mitotic events, coupled to introduction of a short cyclin B1-dependent delay in anaphase onset, sets the rapid pace and ensures fidelity of mitoses in the early C. elegans embryo.
    DOI:  https://doi.org/10.1101/2023.08.11.553011
  4. J Cell Biol. 2023 10 02. pii: e202304020. [Epub ahead of print]222(10):
    The minus-end depolymerase KIF2A drives flux-like treadmilling of γTuRC-uncapped microtubules.
    Gil Henkin, Cláudia Brito, Claire Thomas, Thomas Surrey.
      During mitosis, microtubules in the spindle turn over continuously. At spindle poles, where microtubule minus ends are concentrated, microtubule nucleation and depolymerization, the latter required for poleward microtubule flux, happen side by side. How these seemingly antagonistic processes of nucleation and depolymerization are coordinated is not understood. Here, we reconstitute this coordination in vitro combining different pole-localized activities. We find that the spindle pole-localized kinesin-13 KIF2A is a microtubule minus-end depolymerase, in contrast to its paralog MCAK. Due to its asymmetric activity, KIF2A still allows microtubule nucleation from the γ-tubulin ring complex (γTuRC), which serves as a protective cap shielding the minus end against KIF2A binding. Efficient γTuRC uncapping requires the combined action of KIF2A and a microtubule severing enzyme, leading to treadmilling of the uncapped microtubule driven by KIF2A. Together, these results provide insight into the molecular mechanisms by which a minimal protein module coordinates microtubule nucleation and depolymerization at spindle poles consistent with their role in poleward microtubule flux.
    DOI:  https://doi.org/10.1083/jcb.202304020
  5. J Biomol Struct Dyn. 2023 Aug 22. 1-19
    Delineation of the CENP-LN sub-complex dissociation mechanism upon multisite phosphorylation during mitosis.
    Olanrewaju Ayodeji Durojaye.
      Phosphorylation is the most prevalent form of regulation in cells, organizing virtually all cellular functions, including survival, motility, differentiation, proliferation, and metabolism. This regulatory function has been largely conserved from the primitive single-cell to the more complex multicellular organisms. More than a third of proteins in eukaryotes are phosphorylated, and essentially every class of protein undergoes regulation by phosphorylation. A decline in the cellular level of CENP-L and CENP-N (components of the constitutive centromere associated network) has earlier been reported and linked to cyclin-dependent kinase (CDK) phosphorylation upon transition into mitosis. Given the importance of posttranslational modifications in cell cycle regulation, mechanistic comprehension of the impact of phosphorylation on both proteins (CENP-L and CENP-N) is of high significance. Through the application of diverse computational analytical techniques, including atomistic molecular dynamics simulations, the mechanism of kinetochore mis-localization and dissociation of the CENP-LN sub-complex in mitosis was delineated. We showed that the phosphorylation of both components of the sub-complex induces global conformational destabilizing effects on the proteins, combined with changes in the electrostatic potential and increase in steric clashes around the protein-protein interaction interface. This, consistent with earlier experimental reports, suggest that the multisite phosphorylation of the CENP-LN sub-complex plays a crucial role in the regulation of cell division.Communicated by Ramaswamy H. Sarma.
    Keywords:  CCAN; CENP-L; CENP-N; Posttranslational modification; phosphorylation
    DOI:  https://doi.org/10.1080/07391102.2023.2249101
  6. Biochim Biophys Acta Rev Cancer. 2023 Aug 23. pii: S0304-419X(23)00114-2. [Epub ahead of print] 188965
    Perspectives and mechanisms for targeting mitotic catastrophe in cancer treatment.
    Zhaoshi Bai, Yiran Zhou, Yaling Peng, Xinyue Ye, Lingman Ma.
      Mitotic catastrophe is distinct from other cell death modes due to unique nuclear alterations characterized as multi and/or micronucleation. Mitotic catastrophe is a common and virtually unavoidable consequence during cancer therapy. However, a comprehensive understanding of mitotic catastrophe remains lacking. Herein, we summarize the anticancer drugs that induce mitotic catastrophe, including microtubule-targeting agents, spindle assembly checkpoint kinase inhibitors, DNA damage agents and DNA damage response inhibitors. Based on the relationships between mitotic catastrophe and other cell death modes, we thoroughly evaluated the roles played by mitotic catastrophe in cancer treatment as well as its advantages and disadvantages. Some strategies for overcoming its shortcomings while fully utilizing its advantages are summarized and proposed in this review. We also review how mitotic catastrophe regulates cancer immunotherapy. These summarized findings suggest that the induction of mitotic catastrophe can serve as a promising new therapeutic approach for overcoming apoptosis resistance and strengthening cancer immunotherapy.
    Keywords:  Apoptosis resistance; Cancer immunotherapy; Cell death modes; Mitotic catastrophe; Multi and/or micronucleation
    DOI:  https://doi.org/10.1016/j.bbcan.2023.188965
  7. Proc Natl Acad Sci U S A. 2023 Aug 29. 120(35): e2305037120
    Specific inhibition of an anticancer target, polo-like kinase 1, by allosterically dismantling its mechanism of substrate recognition.
    Jung-Eun Park, Klara Kirsch, Hobin Lee, Paola Oliva, Jong Il Ahn, Harsha Ravishankar, Yan Zeng, Stephen D Fox, Samuel A Kirby, Pooja Badhwar, Thorkell Andresson, Kenneth A Jacobson, Kyung S Lee.
      Polo-like kinase 1 (Plk1) is considered an attractive target for anticancer therapy. Over the years, studies on the noncatalytic polo-box domain (PBD) of Plk1 have raised the expectation of generating highly specific protein-protein interaction inhibitors. However, the molecular nature of the canonical PBD-dependent interaction, which requires extensive water network-mediated interactions with its phospholigands, has hampered efforts to identify small molecules suitable for Plk1 PBD drug discovery. Here, we report the identification of the first allosteric inhibitor of Plk1 PBD, called Allopole, a prodrug that can disrupt intracellular interactions between PBD and its cognate phospholigands, delocalize Plk1 from centrosomes and kinetochores, and induce mitotic block and cancer cell killing. At the structural level, its unmasked active form, Allopole-A, bound to a deep Trp-Phe-lined pocket occluded by a latch-like loop, whose adjoining region was required for securely retaining a ligand anchored to the phospho-binding cleft. Allopole-A binding completely dislodged the L2 loop, an event that appeared sufficient to trigger the dissociation of a phospholigand and inhibit PBD-dependent Plk1 function during mitosis. Given Allopole's high specificity and antiproliferative potency, this study is expected to open an unexplored avenue for developing Plk1 PBD-specific anticancer therapeutic agents.
    Keywords:  X-ray crystallography; allosteric inhibitor; mitotic kinase; polo-box domain; polo-like kinase 1
    DOI:  https://doi.org/10.1073/pnas.2305037120
  8. bioRxiv. 2023 Aug 11. pii: 2023.08.10.552800. [Epub ahead of print]
    Non-homologous end joining shapes the genomic rearrangement landscape of chromothripsis from mitotic errors.
    Qing Hu, Jose Espejo Valle-Inclan, Rashmi Dahiya, Alison Guyer, Alice Mazzagatti, Elizabeth G Maurais, Justin L Engel, Isidro Cortés-Ciriano, Peter Ly.
      Errors in mitosis can generate micronuclei that entrap mis-segregated chromosomes, which are susceptible to catastrophic fragmentation through a process termed chromothripsis. The reassembly of fragmented chromosomes by error-prone DNA double-strand break (DSB) repair generates a spectrum of simple and complex genomic rearrangements that are associated with human cancers and disorders. How specific DSB repair pathways recognize and process these lesions remains poorly understood. Here we used CRISPR/Cas9 to systematically inactivate distinct DSB processing or repair pathways and interrogated the rearrangement landscape of fragmented chromosomes from micronuclei. Deletion of canonical non-homologous end joining (NHEJ) components, including DNA-PKcs, LIG4, and XLF, substantially reduced the formation of complex rearrangements and shifted the rearrangement landscape toward simple alterations without the characteristic patterns of cancer-associated chromothripsis. Following reincorporation into the nucleus, fragmented chromosomes localize within micronuclei bodies (MN bodies) and undergo successful ligation by NHEJ within a single cell cycle. In the absence of NHEJ, chromosome fragments were rarely engaged by polymerase theta-mediated alternative end-joining or recombination-based mechanisms, resulting in delayed repair kinetics and persistent 53BP1-labeled MN bodies in the interphase nucleus. Prolonged DNA damage signaling from unrepaired fragments ultimately triggered cell cycle arrest. Thus, we provide evidence supporting NHEJ as the exclusive DSB repair pathway generating complex rearrangements following chromothripsis from mitotic errors.
    DOI:  https://doi.org/10.1101/2023.08.10.552800
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