bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023–01–22
seven papers selected by
Valentina Piano, Uniklinik Köln
  1. The HIPK2/CDC14B-MeCP2 axis enhances the spindle assembly checkpoint block by promoting cyclin B translation.
  2. Mitotic chromosome condensation resets chromatin to safeguard transcriptional homeostasis during interphase.
  3. Kinesin-5/Cut7 moves bidirectionally on fission-yeast spindles with activity that increases in anaphase.
  4. Inactivation of Mad2B Enhances Apoptosis in Human Cervical Cancer Cell Line upon Cisplatin-Induced DNA Damage.
  5. Chromodomain on Y-like 2 (CDYL2) implicated in mitosis and genome stability regulation via interaction with CHAMP1 and POGZ.
  6. DASH/Dam1 complex mutants stabilize ploidy in histone-humanized yeast by weakening kinetochore-microtubule attachments.
  7. Phosphosite Scanning reveals a complex phosphorylation code underlying CDK-dependent activation of Hcm1.
  1. Sci Adv. 2023 Jan 20. 9(3): eadd6982
    The HIPK2/CDC14B-MeCP2 axis enhances the spindle assembly checkpoint block by promoting cyclin B translation.
    Patrick Partscht, Alexander Simon, Nan-Peng Chen, Sylvia Erhardt, Elmar Schiebel.
      Mitotic perturbations activate the spindle assembly checkpoint (SAC) that keeps cells in prometaphase with high CDK1 activity. Prolonged mitotic arrest is eventually bypassed by gradual cyclin B decline followed by slippage of cells into G1 without chromosome segregation, a process that promotes cell transformation and drug resistance. Hitherto, the cyclin B1 decay is exclusively defined by mechanisms that involve its proteasomal degradation. Here, we report that hyperphosphorylated HIPK2 kinase accumulates in mitotic cells and phosphorylates the Rett syndrome protein MeCP2 at Ser92, a regulation that is counteracted by CDC14B phosphatase. MeCP2S92 phosphorylation leads to the enhanced translation of cyclin B1, which is important for cells with persistent SAC activation to counteract the proteolytic decline of cyclin B1 and therefore to suspend mitotic slippage. Hence, the HIPK2/CDC14B-MeCP2 axis functions as an enhancer of the SAC-induced mitotic block. Collectively, our study revises the prevailing view of how cells confer a sustainable SAC.
    DOI:  https://doi.org/10.1126/sciadv.add6982
  2. Proc Natl Acad Sci U S A. 2023 Jan 24. 120(4): e2210593120
    Mitotic chromosome condensation resets chromatin to safeguard transcriptional homeostasis during interphase.
    Lucía Ramos-Alonso, Petter Holland, Stéphanie Le Gras, Xu Zhao, Bernard Jost, Magnar Bjørås, Yves Barral, Jorrit M Enserink, Pierre Chymkowitch.
      Mitotic entry correlates with the condensation of the chromosomes, changes in histone modifications, exclusion of transcription factors from DNA, and the broad downregulation of transcription. However, whether mitotic condensation influences transcription in the subsequent interphase is unknown. Here, we show that preventing one chromosome to condense during mitosis causes it to fail resetting of transcription. Rather, in the following interphase, the affected chromosome contains unusually high levels of the transcription machinery, resulting in abnormally high expression levels of genes in cis, including various transcription factors. This subsequently causes the activation of inducible transcriptional programs in trans, such as the GAL genes, even in the absence of the relevant stimuli. Thus, mitotic chromosome condensation exerts stringent control on interphase gene expression to ensure the maintenance of basic cellular functions and cell identity across cell divisions. Together, our study identifies the maintenance of transcriptional homeostasis during interphase as an unexpected function of mitosis and mitotic chromosome condensation.
    Keywords:  cell cycle; chromatin; chromosomes; mitosis; transcription
    DOI:  https://doi.org/10.1073/pnas.2210593120
  3. J Cell Sci. 2023 Jan 19. pii: jcs.260474. [Epub ahead of print]
    Kinesin-5/Cut7 moves bidirectionally on fission-yeast spindles with activity that increases in anaphase.
    Zachary R Gergely, Saad Ansari, Michele H Jones, Bojun Zhou, Cai Cash, Richard McIntosh, Meredith D Betterton.
      Kinesin-5 motors are essential to separate mitotic spindle poles and assemble a bipolar spindle in many organisms. These motors crosslink and slide apart antiparallel microtubules via microtubule plus-end-directed motility. However, kinesin-5 localization is enhanced away from antiparallel overlaps. Increasing evidence suggests this localization occurs due to bidirectional motility or trafficking. Purified fission-yeast kinesin-5 Cut7p moves bidirectionally, but bidirectionality has not been shown in cells and the function of the minus-end-directed movement is unknown. We characterized the motility of Cut7p on bipolar and monopolar spindles and observed movement toward both plus and minus ends of microtubules. Notably, the activity of the motor increases at anaphase B onset. Perturbations to microtubule dynamics only modestly changed Cut7p movement, while Cut7p mutation reduced movement. These results suggest that the directed motility of Cut7p contributed to the movement of the motor. Comparison of Cut7 mutant and human Eg5 localization suggest a new hypothesis for the function of minus-end-directed motility and spindle-pole localization of kinesin-5s.
    Keywords:  Cut7; Fission yeast; Kinesin-5; Mitosis
    DOI:  https://doi.org/10.1242/jcs.260474
  4. Biomol Ther (Seoul). 2023 Jan 16.
    Inactivation of Mad2B Enhances Apoptosis in Human Cervical Cancer Cell Line upon Cisplatin-Induced DNA Damage.
    Ju Hwan Kim, Hak Rim Kim, Rajnikant Patel.
      Mad2B (Mad2L2), the human homolog of the yeast Rev7 protein, is a regulatory subunit of DNA polymerase ζ that shares sequence similarity with the mitotic checkpoint protein Mad2A. Previous studies on Mad2B have concluded that it is a mitotic checkpoint protein that functions by inhibiting the anaphase-promoting complex/cyclosome (APC/C). Here, we demonstrate that Mad2B is activated in response to cisplatin-induced DNA damage. Mad2B co-localizes at nuclear foci with DNA damage markers, such as proliferating cell nuclear antigen and gamma histone H2AX (γ-H2AX), following cisplatin-induced DNA damage. However, unlike Mad2A, the binding of Mad2B to Cdc20 does not inhibit the activity of APC/C in vitro. In contrast to Mad2A, Mad2B does not localize to kinetochores or binds to Cdc20 in spindle assembly checkpoint-activated cells. Loss of the Mad2B protein leads to damaged nuclei following cisplatin-induced DNA damage. Mad2B/Rev7 depletion causes the accumulation of damaged nuclei, thereby accelerating apoptosis in human cancer cells in response to cisplatin-induced DNA damage. Therefore, our results suggest that Mad2B may be a critical modulator of DNA damage response.
    Keywords:  Apoptosis; Cancer; Cell cycle; Cisplatin; DNA damage; Mad2B
    DOI:  https://doi.org/10.4062/biomolther.2022.130
  5. Cell Mol Life Sci. 2023 Jan 20. 80(2): 47
    Chromodomain on Y-like 2 (CDYL2) implicated in mitosis and genome stability regulation via interaction with CHAMP1 and POGZ.
    Maha Siouda, Audrey D Dujardin, Blanche Dekeyzer, Laurent Schaeffer, Peter Mulligan.
      Histone H3 trimethylation on lysine 9 (H3K9me3) is a defining feature of mammalian pericentromeres, loss of which results in genome instability. Here we show that CDYL2 is recruited to pericentromeres in an H3K9me3-dependent manner and is required for faithful mitosis and genome stability. CDYL2 RNAi in MCF-7 breast cancer cells and Hela cervical cancer cells inhibited their growth, induced apoptosis, and provoked both nuclear and mitotic aberrations. Mass spectrometry analysis of CDYL2-interacting proteins identified the neurodevelopmental disease-linked mitotic regulators CHAMP1 and POGZ, which are associated with a central non-conserved region of CDYL2. RNAi rescue assays identified both the CDYL2 chromodomain and the CHAMP1-POGZ interacting region as required and, together, sufficient for CDYL2 regulation of mitosis and genome stability. CDYL2 RNAi caused loss of CHAMP1 localization at pericentromeres. We propose that CDYL2 functions as an adaptor protein that connects pericentromeric H3K9me3 with CHAMP1 and POGZ to ensure mitotic fidelity and genome stability.
    Keywords:  C13orf8; CAMP; Centromere; Epigenetics; ZNF828
    DOI:  https://doi.org/10.1007/s00018-022-04659-7
  6. EMBO J. 2023 Jan 18. e112600
    DASH/Dam1 complex mutants stabilize ploidy in histone-humanized yeast by weakening kinetochore-microtubule attachments.
    Max A B Haase, Guðjón Ólafsson, Rachel L Flores, Emmanuel Boakye-Ansah, Alex Zelter, Miles Sasha Dickinson, Luciana Lazar-Stefanita, David M Truong, Charles L Asbury, Trisha N Davis, Jef D Boeke.
      Forcing budding yeast to chromatinize their DNA with human histones manifests an abrupt fitness cost. We previously proposed chromosomal aneuploidy and missense mutations as two potential modes of adaptation to histone humanization. Here, we show that aneuploidy in histone-humanized yeasts is specific to a subset of chromosomes that are defined by their centromeric evolutionary origins but that these aneuploidies are not adaptive. Instead, we find that a set of missense mutations in outer kinetochore proteins drives adaptation to human histones. Furthermore, we characterize the molecular mechanism underlying adaptation in two mutants of the outer kinetochore DASH/Dam1 complex, which reduce aneuploidy by suppression of chromosome instability. Molecular modeling and biochemical experiments show that these two mutants likely disrupt a conserved oligomerization interface thereby weakening microtubule attachments. We propose a model through which weakened microtubule attachments promote increased kinetochore-microtubule turnover and thus suppress chromosome instability. In sum, our data show how a set of point mutations evolved in histone-humanized yeasts to counterbalance human histone-induced chromosomal instability through weakening microtubule interactions, eventually promoting a return to euploidy.
    Keywords:  Saccharomyces cerevisiae; aneuploidy; centromere dysfunction; histones; kinetochore
    DOI:  https://doi.org/10.15252/embj.2022112600
  7. Nat Commun. 2023 Jan 19. 14(1): 310
    Phosphosite Scanning reveals a complex phosphorylation code underlying CDK-dependent activation of Hcm1.
    Michelle M Conti, Rui Li, Michelle A Narváez Ramos, Lihua Julie Zhu, Thomas G Fazzio, Jennifer A Benanti.
      Ordered cell cycle progression is coordinated by cyclin dependent kinases (CDKs). CDKs often phosphorylate substrates at multiple sites clustered within disordered regions. However, for most substrates, it is not known which phosphosites are functionally important. We developed a high-throughput approach, Phosphosite Scanning, that tests the importance of each phosphosite within a multisite phosphorylated domain. We show that Phosphosite Scanning identifies multiple combinations of phosphosites that can regulate protein function and reveals specific phosphorylations that are required for phosphorylation at additional sites within a domain. We applied this approach to the yeast transcription factor Hcm1, a conserved regulator of mitotic genes that is critical for accurate chromosome segregation. Phosphosite Scanning revealed a complex CDK-regulatory circuit that mediates Cks1-dependent phosphorylation of key activating sites in vivo. These results illuminate the mechanism of Hcm1 activation by CDK and establish Phosphosite Scanning as a powerful tool for decoding multisite phosphorylated domains.
    DOI:  https://doi.org/10.1038/s41467-023-36035-9
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