bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2025–04–06
eleven papers selected by
Valentina Piano, Uniklinik Köln
  1. Spindle integrity is regulated by a phospho-dependent interaction between the Ndc80 and Dam1 kinetochore complexes.
  2. Autophagy-related protein Atg11 is essential for microtubule-mediated chromosome segregation.
  3. Meru co-ordinates spindle orientation with cell polarity and cell cycle progression.
  4. Dawning aurora: TPXL3 activates α-Aurora kinase and regulates mitotic spindle morphogenesis.
  5. SKAP binding to microtubules reduces friction at the kinetochore-microtubule interface and increases attachment stability under force.
  6. Role of noncanonical histone H2A variant, H2A.Z, to maintain proper centromeric transcription and chromosome segregation.
  7. Ndc80 complex, a conserved coupler for kinetochore-microtubule motility, is a sliding molecular clutch.
  8. Dual role of p21 in regulating apoptosis and mitotic integrity in response to doxorubicin in colon cancer cells.
  9. Analysis of a cancer-associated mutation in the budding yeast Nuf2 kinetochore protein.
  10. HDAC6 deacetylates ENKD1 to regulate mitotic spindle behavior and corneal epithelial homeostasis.
  11. A chemical-genetic system to rapidly inhibit the PP2A-B56 phosphatase reveals a role at metaphase kinetochores.
  1. PLoS Genet. 2025 Apr 04. 21(4): e1011645
    Spindle integrity is regulated by a phospho-dependent interaction between the Ndc80 and Dam1 kinetochore complexes.
    Christian R Nelson, Darren R Mallett, Sue Biggins.
      Faithful chromosome segregation depends upon kinetochores, large protein complexes that anchor chromosomes to dynamic microtubules, allowing for their movement at anaphase. Critical microtubule-coupling components of the budding yeast kinetochore, the Dam1 (Dam1c) and Ndc80 (Ndc80c) complexes, work cooperatively to ensure that kinetochores track with the plus-ends of microtubules. Additionally, the Dam1 complex plays a distinct role in ensuring the integrity of the mitotic spindle. However, the events required to orchestrate these diverse functions of Dam1c remain unclear. To identify regulatory events on kinetochores, we performed phosphoproteomics on purified kinetochore proteins and identified many previously unknown phosphorylation events. We demonstrate that Ndc80 is phosphorylated at Thr-248 and Thr-252 to promote the interaction between Ndc80 and the Dam1c. The phosphorylation of T248 is cell cycle regulated and depends on Mps1. Ndc80 phosphorylation at T248 and T252 does not appear to regulate kinetochore function and instead contributes to Dam1c localization to the anaphase spindle. A ndc80 phospho-deficient mutant exhibited a genetic interaction and altered spindle morphology when combined with dam1 mutant alleles. Taken together, we propose that Mps1-dependent phosphorylation of Ndc80 at T248 and T252 is removed at anaphase to allow Dam1c to help organize and stabilize the spindle.
    DOI:  https://doi.org/10.1371/journal.pgen.1011645
  2. PLoS Biol. 2025 Apr 02. 23(4): e3003069
    Autophagy-related protein Atg11 is essential for microtubule-mediated chromosome segregation.
    Md Hashim Reza, Rashi Aggarwal, Jigyasa Verma, Nitesh Kumar Podh, Ratul Chowdhury, Gunjan Mehta, Ravi Manjithaya, Kaustuv Sanyal.
      Emerging studies hint at the roles of autophagy-related proteins in various cellular processes. To understand if autophagy-related proteins influence genome stability, we sought to examine a cohort of 35 autophagy mutants in Saccharomyces cerevisiae. We observe cells lacking Atg11 show poor mitotic stability of minichromosomes. Single-molecule tracking assays and live cell microscopy reveal that Atg11 molecules dynamically localize to the spindle pole bodies (SPBs) in a microtubule (MT)-dependent manner. Loss of Atg11 leads to a delayed cell cycle progression. Such cells accumulate at metaphase at an elevated temperature that is relieved when the spindle assembly checkpoint (SAC) is inactivated. Indeed, atg11∆ cells have stabilized securin levels, that prevent anaphase onset. Ipl1-mediated activation of SAC also confirms that atg11∆ mutants are defective in chromosome biorientation. Atg11 functions in the Kar9-dependent spindle positioning pathway. Stabilized Clb4 levels in atg11∆ cells suggest that Atg11 maintains Kar9 asymmetry by facilitating proper dynamic instability of astral microtubules (aMTs). Loss of Spc72 asymmetry contributes to non-random SPB inheritance in atg11∆ cells. Overall, this study uncovers an essential non-canonical role of Atg11 in the MT-mediated process of chromosome segregation.
    DOI:  https://doi.org/10.1371/journal.pbio.3003069
  3. EMBO J. 2025 Apr 01.
    Meru co-ordinates spindle orientation with cell polarity and cell cycle progression.
    Melissa M McLellan, Birgit L Aerne, Jennifer J Banerjee Dhoul, Maxine V Holder, Tania Auchynnikava, Nicolas Tapon.
      Correct mitotic spindle alignment is essential for tissue architecture and plays an important role in cell fate specification through asymmetric cell division. Spindle tethering factors such as Drosophila Mud (NuMA in mammals) are recruited to the cell cortex and capture astral microtubules, pulling the spindle in the correct orientation. However, how spindle tethering complexes read the cell polarity axis and how spindle attachment is coupled to mitotic progression remains poorly understood. We explore these questions in Drosophila sensory organ precursors (SOPs), which divide asymmetrically to give rise to epidermal mechanosensory bristles. We show that the scaffold protein Meru, which is enriched at the posterior cortex by the Frizzled/Dishevelled planar cell polarity complex, in turn recruits Mud, linking the spindle tethering and polarity machineries. Furthermore, Cyclin A/Cdk1 associates with Meru at the posterior cortex, promoting the formation of the Mud/Meru/Dsh complex via Meru and Dsh phosphorylation. Thus, Meru couples spindle orientation with cell polarity and provides a cell cycle-dependent cue for spindle tethering.
    Keywords:  Asymmetric Cell Division; Cell Polarity; Development; Drosophila; Spindle Orientation
    DOI:  https://doi.org/10.1038/s44318-025-00420-5
  4. Plant Cell. 2025 Apr 02. pii: koaf074. [Epub ahead of print]
    Dawning aurora: TPXL3 activates α-Aurora kinase and regulates mitotic spindle morphogenesis.
    Renuka Kolli.
      
    DOI:  https://doi.org/10.1093/plcell/koaf074
  5. Curr Biol. 2025 Mar 25. pii: S0960-9822(25)00288-X. [Epub ahead of print]
    SKAP binding to microtubules reduces friction at the kinetochore-microtubule interface and increases attachment stability under force.
    Miquel Rosas-Salvans, Caleb J Rux, Moumita Das, Sophie Dumont.
      The kinetochore links chromosomes to spindle microtubules to drive chromosome segregation at cell division. We recently uncovered that the kinetochore complex Astrin-SKAP, which binds microtubules, reduces rather than increases friction at the mammalian kinetochore-microtubule interface. How it does so is not known. Astrin-SKAP could affect how other kinetochore complexes bind microtubules, reducing their friction along microtubules, or it could itself bind microtubules with similar affinity but lower friction than other attachment factors. Using SKAP mutants unable to bind microtubules, live imaging, and laser ablation, we show that SKAP's microtubule binding is essential for sister kinetochore coordination, force dissipation at the interface, and attachment responsiveness to force changes. Further, we show that SKAP's microtubule binding is essential to prevent chromosome detachment under both spindle forces and microneedle-generated forces. Together, our findings indicate that SKAP's microtubule binding reduces kinetochore friction and increases attachment responsiveness and stability under force. We propose that having complexes with both high and low sliding friction on microtubules, making a mechanically heterogeneous interface, is key to maintaining robust attachments under force and thus accurate segregation.
    Keywords:  Astrin-SKAP; attachment; dynamics; friction; interface; kinetochore; mechanics; microtubule; robustness; spindle
    DOI:  https://doi.org/10.1016/j.cub.2025.03.003
  6. J Biol Chem. 2025 Mar 27. pii: S0021-9258(25)00313-8. [Epub ahead of print] 108464
    Role of noncanonical histone H2A variant, H2A.Z, to maintain proper centromeric transcription and chromosome segregation.
    Mahmuda Akter, Xiaoai Lyu, Jack Lu, Xiao Wang, Tyson Phonesavanh, Hao Wang, Hongtao Yu, Jungseog Kang.
      The genome stability of eukaryotic cells is ensured by proper regulation of histones and their variants. H2A.Z, a conserved and essential histone H2A variant, plays a crucial role in this process by regulating various chromatin-related processes such as gene expression, heterochromatin formation, DNA damage repair, and chromosome segregation. It has two isoforms, H2A.Z1 and H2A.Z2, also known as H2AFZ and H2AFV respectively, which perform both redundant and non-redundant roles in maintaining genome stability. In this study, we investigated the isoform-specific mitotic functions of H2A.Z in Hela cells. Our studies revealed that the depletion of H2AFV or H2AFZ did not alter the overall cell cycle profile. However, H2AFV depletion significantly increased the formation of micronuclei, indicating defects in chromosome segregation. Additionally, H2AFV depletion led to the accumulation of DNA damage at various nuclear loci including centromeres. Interestingly, we discovered that H2AFV depletion significantly increased centromeric transcription, which may interfere with proper centromere function. Furthermore, we discovered that a mitotic kinase, Aurora B, binds to both H2AFV and H2AFZ, but preferentially to H2AFV. Inhibition of Aurora B activity by hesperadin disrupted proper centromeric transcription but not significantly centromeric localization of H2A.Z. Collectively, these data demonstrated that the H2A.Z isoforms play distinctive regulatory roles in maintaining proper centromeric transcription and DNA repair, ensuring accurate chromosome segregation.
    Keywords:  Chromosome segregation; H2A.Z; centromeric transcription; histone variants; mitotic kinases
    DOI:  https://doi.org/10.1016/j.jbc.2025.108464
  7. bioRxiv. 2025 Mar 13. pii: 2025.03.13.643154. [Epub ahead of print]
    Ndc80 complex, a conserved coupler for kinetochore-microtubule motility, is a sliding molecular clutch.
    Vladimir M Demidov, Ivan V Gonchar, Suvranta K Tripathy, Fazly I Ataullakhanov, Ekaterina L Grishchuk.
      Chromosome motion at spindle microtubule plus-ends relies on dynamic molecular bonds between kinetochores and proximal microtubule walls. Under opposing forces, kinetochores move bi-directionally along these walls while remaining near the ends, yet how continuous wall-sliding occurs without end-detachment remains unclear. Using ultrafast force-clamp spectroscopy, we show that single Ndc80 complexes, the primary microtubule-binding kinetochore component, exhibit processive, bi-directional sliding. Plus-end-directed forces induce a mobile catch-bond in Ndc80, increasing frictional resistance and restricting sliding toward the tip. Conversely, forces pulling Ndc80 away from the plus-end trigger mobile slip-bond behavior, facilitating sliding. This dual behavior arises from force-dependent modulation of the Nuf2 calponin-homology domain's microtubule binding, identifying this subunit as a friction regulator. We propose that Ndc80c's ability to modulate sliding friction provides the mechanistic basis for the kinetochore's end coupling, enabling its slip-clutch behavior.
    One Sentence Summary: Direction-dependent mobile catch- and slip-bond behavior of the microtubule-binding Ndc80 protein.
    DOI:  https://doi.org/10.1101/2025.03.13.643154
  8. Cell Death Discov. 2025 Apr 02. 11(1): 133
    Dual role of p21 in regulating apoptosis and mitotic integrity in response to doxorubicin in colon cancer cells.
    Heeyeon Kim, Haein Kim, Eunjung Jang, Young-Woo Eom, Gyesoon Yoon, Kyeong Sook Choi, Eunhee Kim.
      This study explores the multifaceted role of p21 in mediating cellular responses to DNA-damaging agents, with a focus on doxorubicin treatment in HCT116 colon carcinoma cells. We investigated how different doses of doxorubicin affect cells with varied p21 and p53 statuses, revealing distinct roles for p21 depending on the drug dosage. At high doses (HD), p21 is more critical than p53 in mediating apoptosis, whereas at low doses (LD), p21 is essential for preventing mitotic defects and multinucleation. Notably, reintroducing p21 or pharmacologically inhibiting CDK1 reduced multinucleation. The absence of p21 upon LD doxorubicin exposure led to aberrant chromosome segregation, persistent DNA damage response (DDR) activation, and increased non-homologous end-joining (NHEJ) activity, resulting in unrepaired DNA accumulation and multinucleation. Additionally, mitotic defects in p21-deficient cells were associated with mislocalization of key mitotic regulators, Aurora B and mitotic kinesin-like protein 1 (MKLP1), exacerbating defective mitosis. In summary, p21 functions as a dual regulator in response to DNA damage, promoting apoptosis at HD and preventing mitotic failure at LD. These insights have significant implications for cancer therapy, highlighting the potential of targeting the p21 to enhance treatment efficacy.
    DOI:  https://doi.org/10.1038/s41420-025-02416-w
  9. MicroPubl Biol. 2025 ;2025
    Analysis of a cancer-associated mutation in the budding yeast Nuf2 kinetochore protein.
    Angelica Andrade Latino, Sue Biggins.
      The kinetochore is a highly conserved megadalton protein complex that ensures proper chromosome segregation via microtubule attachments. The NDC80 complex is one of the major conserved microtubule binding complexes in the kinetochore. NUF2, a protein within the NDC80 complex, has been identified as a cancer gene candidate because missense mutations, found across different tumor samples, cluster within NUF2's calponin homology domain. In this study, we examined a NUF2 cancer-associated mutation in a simple and well-studied organism, Saccharomyces cerevisiae , to elucidate its effects on cell division. We studied the budding yeast nuf2 Q21A mutation with the intention of extrapolating our results to the homologous cancer associated mutation in Homo sapiens NUF2 R19H (HsNUF2 R19H ). Our studies demonstrate that the nuf2 Q21A mutant does not exhibit any growth defects or disrupt kinetochore composition. Additionally, it does not affect the Ndc80 complex's interactions with the Dam1 complex or with the Mps1 kinase. These results indicate that the yeast nuf2 Q21A mutant does not cause a significant defect in kinetochore function, and that the role of HsNUF2 R19H in cancer will need to be further investigated by directly studying the cancer-associated mutation in human cells.
    DOI:  https://doi.org/10.17912/micropub.biology.001546
  10. EMBO Rep. 2025 Mar 28.
    HDAC6 deacetylates ENKD1 to regulate mitotic spindle behavior and corneal epithelial homeostasis.
    Ting Song, Xueqing Han, Hanxiao Yin, Junkui Zhao, Mingming Ma, Xiaonuan Wen, Chunli Liu, Yiyang Yue, Huijie Zhao, Jun Zhou, Yang Yang, Jie Ran, Min Liu.
      Corneal diseases can cause severe visual impairment and even blindness, which have been linked to the interruption of corneal epithelial homeostasis. However, the underlying molecular mechanisms are largely unknown. In this study, by comparing the transcriptomes of keratoconus, bacterial keratitis, viral keratitis, and healthy corneas, we found a steady upregulation of histone deacetylase 6 (HDAC6) in corneal diseases. Consistently, a significant increase in HDAC6 was observed in mouse corneas with bacterial keratitis. Overexpression of HDAC6 in mice results in a significant thickening of the corneal epithelium. Mechanistic studies reveal that HDAC6 overexpression disrupts mitotic spindle orientation and positioning in corneal epithelial cells. Our data further show that HDAC6 deacetylates enkurin domain-containing protein 1 (ENKD1) at lysine 98 and thereby impedes its interaction with γ-tubulin, restraining the centrosomal localization of ENKD1 and its proper function in regulating mitotic spindle behavior. These findings uncover a pivotal role for HDAC6-mediated deacetylation of ENKD1 in the control of corneal epithelial homeostasis, providing potential therapeutic targets for treating corneal diseases.
    Keywords:  Centrosome; Corneal Epithelium; Deacetylation; Spindle Orientation; Spindle Positioning
    DOI:  https://doi.org/10.1038/s44319-025-00438-0
  11. Nat Commun. 2025 Mar 29. 16(1): 3069
    A chemical-genetic system to rapidly inhibit the PP2A-B56 phosphatase reveals a role at metaphase kinetochores.
    Lindsey A Allan, Andrea Corno, Juan Manuel Valverde, Rachel Toth, Tony Ly, Adrian T Saurin.
      Serine-threonine phosphatases have been challenging to study because of the lack of specific inhibitors. Their catalytic domains are druggable, but these are shared or very similar between individual phosphatase complexes, precluding their specific inhibition. Instead, phosphatase complexes often achieve specificity by interacting with short linear motifs (SLiMs) in substrates or their binding partners. We develop here a chemical-genetic system to rapidly inhibit these interactions within the PP2A-B56 family. Drug-inducible recruitment of ectopic SLiMs ("directSLiMs") is used to rapidly block the SLiM-binding pocket on the B56 regulatory subunit, thereby displacing endogenous interactors and inhibiting PP2A-B56 activity within seconds. We use this system to characterise PP2A-B56 substrates during mitosis and to identify a role for PP2A-B56 in allowing metaphase kinetochores to properly sense tension and maintain microtubule attachments. The directSLiMs approach can be used to inhibit any other phosphatase, enzyme or protein that uses a critical SLiM-binding interface, providing a powerful strategy to inhibit and characterise proteins once considered "undruggable".
    DOI:  https://doi.org/10.1038/s41467-025-58185-8
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