bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2025–03–30
thirteen papers selected by
Valentina Piano, Uniklinik Köln
  1. Nanoscale DNA tracing reveals the self-organization mechanism of mitotic chromosomes.
  2. CARM1 S217 phosphorylation by CDK1 in late G2 phase facilitates mitotic entry.
  3. Molecular mechanism of Mad2 conformational conversion promoted by the Mad2-interaction motif of Cdc20.
  4. The unconventional TPX2 family protein TPXL3 regulates α Aurora kinase function in spindle morphogenesis in Arabidopsis.
  5. Localization and function of APC15 during mouse oocyte meiotic progression.
  6. Orchestration of pluripotent stem cell genome reactivation during mitotic exit.
  7. Sustained chromosomal passenger complex activity preserves the pluripotency of human embryonic carcinoma cells.
  8. Cryo-EM Analysis of a Unique Subnucleosome Containing Centromere-Specific Histone Variant CENP-A.
  9. Cohesin and condensin regulate chromosome topology and play an essential role in maintaining pluripotency in embryonic stem cells.
  10. Beyond mitotic arrest: the diverse effects of microtubule-targeting drugs on tumor vasculature.
  11. Cardiovascular Mitosis.
  12. Conservation of dichromatin organization along regional centromeres.
  13. Inward transport of organelles drives outward migration of the spindle during C. elegans meiosis.
  1. Cell. 2025 Mar 19. pii: S0092-8674(25)00255-7. [Epub ahead of print]
    Nanoscale DNA tracing reveals the self-organization mechanism of mitotic chromosomes.
    Kai Sandvold Beckwith, Andreas Brunner, Natalia Rosalia Morero, Ralf Jungmann, Jan Ellenberg.
      How genomic DNA is folded during cell division to form the characteristic rod-shaped mitotic chromosomes essential for faithful genome inheritance is a long-standing open question in biology. Here, we use nanoscale DNA tracing in single dividing cells to directly visualize how the 3D fold of genomic DNA changes during mitosis at scales from single loops to entire chromosomes. Our structural analysis reveals a characteristic genome scaling minimum of 6-8 megabases in mitosis. Combined with data-driven modeling and molecular perturbations, we can show that very large and strongly overlapping loops formed by condensins are the fundamental structuring principle of mitotic chromosomes. These loops compact chromosomes locally and globally to the limit set by chromatin self-repulsion. The characteristic length, density, and increasingly overlapping structure of mitotic loops we observe in 3D fully explain how the rod-shaped mitotic chromosome structure emerges by self-organization during cell division.
    Keywords:  cell division; chromatin tracing; chromosome compaction; condensins; genome organization; loop extrusion; mitosis
    DOI:  https://doi.org/10.1016/j.cell.2025.02.028
  2. Cell Death Dis. 2025 Mar 25. 16(1): 202
    CARM1 S217 phosphorylation by CDK1 in late G2 phase facilitates mitotic entry.
    Yena Cho, Dae-Geun Song, Su-Nam Kim, Yong Kee Kim.
      The coactivator-associated arginine methyltransferase 1 (CARM1) functions as an epigenetic writer, however, its role in mitosis remains poorly understood. In this study, we identified CARM1 as a novel substrate of cyclin-dependent kinase 1 (CDK1) and revealed its novel function as a scaffold that regulates CDK1 stability. During interphase, CARM1 acts as an adaptor in the Cullin-1-mediated CDK1 degradation process, limiting nuclear levels of CDK1. In late G2 phase, the CDK1/Cyclin B1 complex translocates to the nucleus, where it phosphorylates the S217 residue of CARM1. This phosphorylation not only inhibits CARM1's enzymatic activity but also facilitates its translocation to the cytoplasm, leading to the loss of its scaffolding function. Consequently, the CDK1/Cyclin B1 complex resides for longer in the nucleus and initiates mitosis. In addition, depletion or inhibition of CARM1 facilitates entry into mitosis, resulting in accelerated cell growth. Overall, our findings expand the cellular functions of CARM1 beyond its enzymatic activity.
    DOI:  https://doi.org/10.1038/s41419-025-07533-z
  3. Protein Sci. 2025 Apr;34(4): e70099
    Molecular mechanism of Mad2 conformational conversion promoted by the Mad2-interaction motif of Cdc20.
    Conny W H Yu, Elyse S Fischer, Joe G Greener, Jing Yang, Ziguo Zhang, Stefan M V Freund, David Barford.
      During mitosis, unattached kinetochores trigger the spindle assembly checkpoint by promoting the assembly of the mitotic checkpoint complex, a heterotetramer comprising Mad2, Cdc20, BubR1, and Bub3. Critical to this process is the kinetochore-mediated catalysis of an intrinsically slow conformational conversion of Mad2 from an open (O-Mad2) inactive state to a closed (C-Mad2) active state bound to Cdc20. These Mad2 conformational changes involve substantial remodeling of the N-terminal β1 strand and C-terminal β7/β8 hairpin. In vitro, the Mad2-interaction motif (MIM) of Cdc20 (Cdc20MIM) triggers the rapid conversion of O-Mad2 to C-Mad2, effectively removing the kinetic barrier for MCC assembly. How Cdc20MIM directly induces Mad2 conversion remains unclear. In this study, we demonstrate that the Cdc20MIM-binding site is inaccessible in O-Mad2. Time-resolved NMR and molecular dynamics simulations show how Mad2 conversion involves sequential conformational changes of flexible structural elements in O-Mad2, orchestrated by Cdc20MIM. Conversion is initiated by the β7/β8 hairpin of O-Mad2 transiently unfolding to expose a nascent Cdc20MIM-binding site. Engagement of Cdc20MIM to this site promotes the release of the β1 strand. We propose that initial conformational changes of the β7/β8 hairpin allow binding of Cdc20MIM to a transient intermediate state of Mad2, thereby lowering the kinetic barrier to Mad2 conversion.
    Keywords:  Cdc20; HORMA domain; Mad2; NMR; cell cycle; metamorphic proteins; molecular dynamic simulations; spindle assembly checkpoint
    DOI:  https://doi.org/10.1002/pro.70099
  4. Plant Cell. 2025 Mar 26. pii: koaf065. [Epub ahead of print]
    The unconventional TPX2 family protein TPXL3 regulates α Aurora kinase function in spindle morphogenesis in Arabidopsis.
    Xingguang Deng, Takumi Higaki, Hong-Hui Lin, Yuh-Ru Julie Lee, Bo Liu.
      Spindle assembly in vertebrates requires the Aurora kinase, which is targeted to microtubules and activated by TPX2 (Targeting Protein of XKLP2). In Arabidopsis (Arabidopsis thaliana), TPX2-LIKE 3 (TPXL3), but not the highly conserved TPX2, is essential. To test the hypothesis that TPXL3 regulates the function of α Aurora kinase in spindle assembly, we generated transgenic Arabidopsis lines expressing an artificial microRNA targeting TPXL3 mRNA (amiR-TPXL3). The resulting mutants exhibited growth retardation, which was linked to compromised TPXL3 expression. In the mutant cells, α Aurora was delocalized from spindle microtubules to the cytoplasm, and spindles were assembled without recognizable poles. A functional TPXL3-GFP fusion protein first prominently appeared on the prophase nuclear envelope. Then, TPXL3-GFP localized to spindle microtubules (primarily towards the spindle poles, like γ-tubulin), and finally to the re-forming nuclear envelope during telophase and cytokinesis. However, TPXL3 was absent from phragmoplast microtubules. In addition, we found that the TPXL3 N-terminal Aurora-binding motif, microtubule-binding domain, and importin-binding motif, but not the C-terminal segment, were required for its mitotic function. Expression of truncated TPXL3 variants enhanced the defects in spindle assembly and seedling growth of amiR-TPXL3 plants. Taken together, our findings uncovered the essential function of TPXL3, but not TPX2, in targeting and activating α Aurora kinase for spindle apparatus assembly in Arabidopsis.
    DOI:  https://doi.org/10.1093/plcell/koaf065
  5. J Mol Histol. 2025 Mar 28. 56(2): 121
    Localization and function of APC15 during mouse oocyte meiotic progression.
    Shi-Bin Chao, Ren-Ren Zhang, Qing-Yuan Sun.
      The Anaphase-Promoting Complex/Cyclosome (APC/C) is a critical regulator of cell cycle progression, with APC15 serving as an essential subunit. While the role of APC15 in mitosis is well characterized, its function during meiosis remains poorly understood. In this study, we investigated the expression, subcellular localization, and potential role of APC15 during mouse oocyte meiotic progression. Using immunofluorescence and confocal microscopy, we observed dynamic changes in APC15 localization throughout meiotic progression. Knockdown of APC15 via siRNA did not affect spindle organization, but led to meiotic arrest at metaphase I (MI) and impaired the removal of BUB3 from kinetochores, suggesting a disruption in Spindle Assembly Checkpoint (SAC) inactivation. Our results highlight the involvement of APC15 in the regulation of SAC and the transition from metaphase to anaphase in oocytes. These findings contribute to our understanding of APC15's role in meiotic regulation and provide insights into its potential impact on maintaining chromosomal stability during oocyte maturation.
    Keywords:  APC15; Meiosis; Meiotic arrest; Spindle; Spindle assembly checkpoint
    DOI:  https://doi.org/10.1007/s10735-025-10404-8
  6. Cell Rep. 2025 Mar 27. pii: S2211-1247(25)00257-8. [Epub ahead of print]44(4): 115486
    Orchestration of pluripotent stem cell genome reactivation during mitotic exit.
    Silja Placzek, Ludovica Vanzan, Cédric Deluz, David M Suter.
      Cell identity maintenance faces many challenges during mitosis, as most DNA-binding proteins are evicted from DNA and transcription is virtually abolished. How cells maintain their identity through division and faithfully re-initiate gene expression during mitotic exit is unclear. Here, we develop a novel reporter system enabling cell cycle synchronization-free separation of pluripotent stem cells in temporal bins of <30 min during mitotic exit. This allows us to quantify genome-wide reactivation of transcription, sequential changes in chromatin accessibility and transcription factor footprints, and re-binding of the pluripotency transcription factors OCT4, SOX2, and NANOG (OSN). We find that transcriptional activity progressively ramps up after mitosis and that OSN rapidly reoccupy the genome during the anaphase-telophase transition. We also demonstrate transcription factor-specific, dynamic relocation patterns and a hierarchical reorganization of the OSN binding landscape governed by OCT4 and SOX2. Our study sheds light on the dynamic orchestration of transcriptional reactivation after mitosis.
    Keywords:  ATAC-seq; CP: Cell biology; CP: Stem cell research; ChIP-seq; NANOG; OCT4; RNA-seq; SOX2; chromatin; mitosis; pluripotent stem cells; transcription factors
    DOI:  https://doi.org/10.1016/j.celrep.2025.115486
  7. Sci Signal. 2025 Feb 18. 18(874): eadg4626
    Sustained chromosomal passenger complex activity preserves the pluripotency of human embryonic carcinoma cells.
    Takaaki Tsunematsu, Yasuhiro Mouri, Wenhua Shao, Rieko Arakaki, Jan G Ruppert, Kensaku Murano, Naozumi Ishimaru, Daniele Guardavaccaro, Michele Pagano, Yasusei Kudo.
      Human embryonic carcinoma (hEC) cells are derived from teratocarcinomas, exhibit robust proliferation, have a high differentiation potential, are the malignant counterparts of human embryonic stem cells (hESCs), and are considered hESC-like. The chromosomal passenger complex (CPC), made up of the microtuble binding protein Borealin, the kinase Aurora-B, the CPC-stabilizing inner centromere protein (INCENP), and the inhibitor of apoptosis family member Survivin, regulates cell division and is active exclusively during mitosis in somatic cells. The anaphase-promoting complex/cyclosome and its cofactor Cdh1 (APC/CCdh1) is a ubiquitylating complex that catalyzes the degradation of Aurora-B and Borealin in somatic cells but has low activity during interphase in hESCs. Here, we found that Borealin and Aurora-B exhibited sustained stability throughout the cell cycle of hEC cells due to low APC/CCdh1 activity. In contrast with somatic cells, CPC activity persisted across the cell cycle of hEC cells because of diminished APC/CCdh1 activity. Disrupting the CPC complex by depleting its constituents triggered spontaneous differentiation in hEC cells. As hEC cells differentiated, APC/CCdh1 activation curtailed CPC activity. Inactivating the CPC by pharmacologically inhibiting Aurora-B induced hEC cell differentiation by activating the epithelial-to-mesenchymal transition (EMT) program. Hence, APC/CCdh1-mediated termination of CPC activity triggered hEC cell differentiation. Collectively, these findings demonstrate a role for the CPC in governing hESC cell fate.
    DOI:  https://doi.org/10.1126/scisignal.adg4626
  8. Genes Cells. 2025 Mar;30(2): e70016
    Cryo-EM Analysis of a Unique Subnucleosome Containing Centromere-Specific Histone Variant CENP-A.
    Osamu Kawasaki, Yoshimasa Takizawa, Iori Kiyokawa, Hitoshi Kurumizaka, Kayo Nozawa.
      In eukaryotes, genomic DNA is stored in the nucleus as nucleosomes, in which a DNA segment is wrapped around a protein octamer consisting of two each of the four histones, H2A, H2B, H3, and H4. The core histones can be replaced by histone variants or altered with covalent modifications, contributing to the regulation of chromosome structure and nuclear activities. The formation of an octameric histone core in nucleosomes is widely accepted. Recently, the H3-H4 octasome, a novel nucleosome-like structure with a histone octamer consisting solely of H3 and H4, has been reported. CENP-A is the centromere-specific histone H3 variant and determines the position of kinetochore assembly during mitosis. CENP-A is a distant H3 variant sharing approximately 50% amino acid sequence with H3. In this study, we found that CENP-A and H4 also formed an octamer without H2A and H2B in vitro. We determined the structure of the CENP-A-H4 octasome at 3.66 Å resolution. In the CENP-A-H4 octasome, an approximately 120-base pair DNA segment was wrapped around the CENP-A-H4 octameric core and displayed the four CENP-A RG-loops, which are the direct binding sites for another centromeric protein, CENP-N.
    Keywords:  CENP‐A; centromere; cryo‐EM structure; histone; nucleosome
    DOI:  https://doi.org/10.1111/gtc.70016
  9. Sci Rep. 2025 Mar 22. 15(1): 9918
    Cohesin and condensin regulate chromosome topology and play an essential role in maintaining pluripotency in embryonic stem cells.
    Eui-Hwan Choi, Keun P Kim.
      Cohesin and condensin, two related protein complexes, play essential roles in ensuring the accurate segregation of the genome into daughter cells during cell division. However, the interaction between cohesin and condensin in embryonic stem cells remains unclear, as does the specific function of the meiosis-specific cohesin complex. Cohesin maintains the cohesion of replicated sister chromatids until their separation at anaphase, whereas condensin facilitates the reorganization of chromosomes into a highly compact structure characteristic of mitosis. First, we found via ChIP-seq analysis that cohesins (SMC3, RAD21, and REC8) and condensin (SMC4) share DNA binding sites in close proximity and directly interact with the insulator protein CTCF. Second, siRNA-regulated SMC3 depletion led to nuclear accumulation of SMC4. Third, embryonic stem (ES) cells uniquely harbor cohesin complexes containing the meiotic kleisin subunit REC8. RAD21 knockdown increased the proportion of SMC3-REC8 complexes. Our findings indicate that cohesin and condensin make important contributions to the functions of the chromosomal organization, and that meiotic cohesin may be specifically required for the mitotic program in ES cells.
    Keywords:  Cohesin; Condensin; Embryonic stem cell; Meiosis; Mitosis
    DOI:  https://doi.org/10.1038/s41598-025-94533-w
  10. EMBO Mol Med. 2025 Mar 26.
    Beyond mitotic arrest: the diverse effects of microtubule-targeting drugs on tumor vasculature.
    April L Risinger.
      
    DOI:  https://doi.org/10.1038/s44321-025-00223-5
  11. Struct Heart. 2025 Feb;9(2): 100409
    Cardiovascular Mitosis.
    Anthony DeMaria.
      
    DOI:  https://doi.org/10.1016/j.shj.2025.100409
  12. Cell Genom. 2025 Mar 21. pii: S2666-979X(25)00075-8. [Epub ahead of print] 100819
    Conservation of dichromatin organization along regional centromeres.
    Danilo Dubocanin, Gabrielle A Hartley, Adriana E Sedeño Cortés, Yizi Mao, Sabrine Hedouin, Jane Ranchalis, Aman Agarwal, Glennis A Logsdon, Katherine M Munson, Taylor Real, Benjamin J Mallory, Evan E Eichler, Sue Biggins, Rachel J O'Neill, Andrew B Stergachis.
      The attachment of the kinetochore to the centromere is essential for genome maintenance, yet the highly repetitive nature of satellite regional centromeres limits our understanding of their chromatin organization. We demonstrate that single-molecule chromatin fiber sequencing (Fiber-seq) can uniquely co-resolve kinetochore and surrounding chromatin architectures along point centromeres, revealing largely homogeneous single-molecule kinetochore occupancy. In contrast, the application of Fiber-seq to regional centromeres exposed marked per-molecule heterogeneity in their chromatin organization. Regional centromere cores uniquely contain a dichotomous chromatin organization (dichromatin) composed of compacted nucleosome arrays punctuated with highly accessible chromatin patches. CENP-B occupancy phases dichromatin to the underlying alpha-satellite repeat within centromere cores but is not necessary for dichromatin formation. Centromere core dichromatin is conserved between humans and primates, including along regional centromeres lacking satellite repeats. Overall, the chromatin organization of regional centromeres is defined by marked per-molecule heterogeneity, buffering kinetochore attachment against sequence and structural variability within regional centromeres.
    Keywords:  Alpha-satellite; CENP-B; Fiber-seq; centromere; chromatin; kinetochore; single molecule
    DOI:  https://doi.org/10.1016/j.xgen.2025.100819
  13. Cell Rep. 2025 Mar 22. pii: S2211-1247(25)00229-3. [Epub ahead of print]44(4): 115458
    Inward transport of organelles drives outward migration of the spindle during C. elegans meiosis.
    Alma P Aquino, Wenzhe Li, Aastha Lele, Denisa Lazureanu, Megan F Hampton, Rebecca M Do, Melissa C Lafrades, Maria G Barajas, Antonio A Batres, Francis J McNally.
      Cortical positioning of the meiotic spindle within an oocyte is required to expel chromosomes into polar bodies to generate a zygote with the correct number of chromosomes. In C. elegans, yolk granules and mitochondria are packed inward, away from the cortex, while the spindle moves outward, both in a kinesin-dependent manner. The kinesin-dependent inward packing of yolk granules suggests the existence of microtubules with minus ends at the cortex and plus ends extending inward, making it unclear how kinesin moves the spindle outward. We hypothesize that the inward packing of organelles might indirectly force the spindle outward by volume exclusion. To test this hypothesis, we generate a strain in which the only kinesin consists of motor domains with no cargo-binding tail optogenetically attached to mitochondria. This mitochondria-only kinesin packs mitochondria into a tight ball and efficiently moves the meiotic spindle to the cortex, supporting the volume exclusion hypothesis.
    Keywords:  CP: Cell biology; kinesin; meiosis; meiotic spindle; oocyte
    DOI:  https://doi.org/10.1016/j.celrep.2025.115458
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