bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023–09–24
eightteen papers selected by
Valentina Piano, Uniklinik Köln
  1. Signaling protein abundance modulates the strength of the spindle assembly checkpoint.
  2. CTCF is essential for proper mitotic spindle structure and anaphase segregation.
  3. Mitotic chromatin marking governs asymmetric segregation of DNA damage.
  4. Distinct regions of the kinesin-5 C-terminal tail are essential for mitotic spindle midzone localization and sliding force.
  5. SiR-DNA/SiR-Hoechst-induced chromosome entanglement generates severe anaphase bridges and DNA damage.
  6. Apical PAR protein caps orient the mitotic spindle in C. elegans early embryos.
  7. UHRF1 promotes spindle assembly and chromosome congression by catalyzing EG5 polyubiquitination.
  8. Cell cycle-dependent organization of a bacterial centromere through multi-layered regulation of the ParABS system.
  9. Single molecule analysis of CENP-A chromatin by high-speed atomic force microscopy.
  10. Aspergillus SUMOylation mutants exhibit chromosome-segregation defects including chromatin bridges.
  11. Phosphotyrosine proteomics in cells synchronized at monopolar cytokinesis reveals EphA2 as functioning in cytokinesis.
  12. Mitotic genome-bookmarking by nuclear hormone receptors: A novel dimension in epigenetic reprogramming and disease assessment.
  13. Unannotated microprotein EMBOW regulates the interactome and chromatin and mitotic functions of WDR5.
  14. The TRIM69-MST2 signaling axis regulates centrosome dynamics and chromosome segregation.
  15. SETD2 safeguards the genome against isochromosome formation.
  16. The localization of centromere protein A is conserved among tissues.
  17. Disentangling the roles of aneuploidy, chromosomal instability and tumour heterogeneity in developing resistance to cancer therapies.
  18. Selective retention of dysfunctional mitochondria during asymmetric cell division in yeast.
  1. Curr Biol. 2023 Sep 13. pii: S0960-9822(23)01154-5. [Epub ahead of print]
    Signaling protein abundance modulates the strength of the spindle assembly checkpoint.
    Soubhagyalaxmi Jema, Chu Chen, Lauren Humphrey, Shriya Karmarkar, Frank Ferrari, Ajit P Joglekar.
      During mitosis, unattached kinetochores in a dividing cell signal to the spindle assembly checkpoint (SAC) to delay anaphase onset and prevent chromosome missegregation.1,2,3,4 The signaling activity of these kinetochores and the likelihood of chromosome missegregation depend on the amount of SAC signaling proteins each kinetochore recruits.5,6,7,8 Therefore, factors that control SAC protein recruitment must be thoroughly understood. Phosphoregulation of kinetochore and SAC signaling proteins due to the concerted action of many kinases and phosphatases is a significant determinant of the SAC protein recruitment to signaling kinetochores.9 Whether the abundance of SAC proteins also influences the recruitment and signaling activity of human kinetochores has not been studied.8,10 Here, we reveal that the low cellular abundance of the SAC signaling protein Bub1 limits its own recruitment and that of BubR1 and restricts the SAC signaling activity of the kinetochore. Conversely, Bub1 overexpression results in higher recruitment of SAC proteins, producing longer delays in anaphase onset. We also find that the number of SAC proteins recruited by a signaling kinetochore is inversely correlated with the total number of signaling kinetochores in the cell. This correlation likely arises from the competition among the signaling kinetochores to recruit from a limited pool of signaling proteins, including Bub1. The inverse correlation may allow the dividing cell to prevent a large number of signaling kinetochores in early prophase from generating an overly large signal while enabling the last unaligned kinetochore in late prometaphase to signal at the maximum strength.
    Keywords:  cell cycle; kinetochore; microscopy; mitosis; signaling; spindle assembly checkpoint
    DOI:  https://doi.org/10.1016/j.cub.2023.08.074
  2. Chromosoma. 2023 Sep 20.
    CTCF is essential for proper mitotic spindle structure and anaphase segregation.
    Katherine Chiu, Yasmin Berrada, Nebiyat Eskndir, Dasol Song, Claire Fong, Sarah Naughton, Tina Chen, Savanna Moy, Sarah Gyurmey, Liam James, Chimere Ezeiruaku, Caroline Capistran, Daniel Lowey, Vedang Diwanji, Samantha Peterson, Harshini Parakh, Ayanna R Burgess, Cassandra Probert, Annie Zhu, Bryn Anderson, Nehora Levi, Gabi Gerlitz, Mary C Packard, Katherine A Dorfman, Michael Seifu Bahiru, Andrew D Stephens.
      Mitosis is an essential process in which the duplicated genome is segregated equally into two daughter cells. CTCF has been reported to be present in mitosis and has a role in localizing CENP-E, but its importance for mitotic fidelity remains to be determined. To evaluate the importance of CTCF in mitosis, we tracked mitotic behaviors in wild-type and two different CTCF CRISPR-based genetic knockdowns. We find that knockdown of CTCF results in prolonged mitoses and failed anaphase segregation via time-lapse imaging of SiR-DNA. CTCF knockdown did not alter cell cycling or the mitotic checkpoint, which was activated upon nocodazole treatment. Immunofluorescence imaging of the mitotic spindle in CTCF knockdowns revealed disorganization via tri/tetrapolar spindles and chromosomes behind the spindle pole. Imaging of interphase nuclei showed that nuclear size increased drastically, consistent with failure to divide the duplicated genome in anaphase. Long-term inhibition of CNEP-E via GSK923295 recapitulates CTCF knockdown abnormal mitotic spindles with polar chromosomes and increased nuclear sizes. Population measurements of nuclear shape in CTCF knockdowns do not display decreased circularity or increased nuclear blebbing relative to wild-type. However, failed mitoses do display abnormal nuclear morphologies relative to successful mitoses, suggesting that population images do not capture individual behaviors. Thus, CTCF is important for both proper metaphase organization and anaphase segregation which impacts the size and shape of the interphase nucleus likely through its known role in recruiting CENP-E.
    Keywords:  CTCF; DNA/chromatin; Mitosis; Mitotic spindle; Nucleus
    DOI:  https://doi.org/10.1007/s00412-023-00810-w
  3. bioRxiv. 2023 Sep 05. pii: 2023.09.04.556166. [Epub ahead of print]
    Mitotic chromatin marking governs asymmetric segregation of DNA damage.
    Juliette Ferrand, Juliette Dabin, Odile Chevallier, Ariana Kupai, Scott B Rothbart, Sophie E Polo.
      The faithful segregation of intact genetic material and the perpetuation of chromatin states through mitotic cell divisions are pivotal for maintaining cell function and identity across cell generations. However, most exogenous mutagens generate long-lasting DNA lesions that are segregated during mitosis. How this segregation is controlled is unknown. Here, we uncover a mitotic chromatin-marking pathway that governs the segregation of UV-induced damage in human cells. Our mechanistic analyses reveal two layers of control: histone ADP-ribosylation, and the incorporation of newly synthesized histones at UV damage sites, that both prevent local mitotic phosphorylations on histone H3 serines. Functionally, this chromatin-marking pathway drives the asymmetric segregation of UV damage in the cell progeny with potential consequences on daughter cell fate. We propose that this mechanism may help preserve the integrity of stem cell compartments during asymmetric cell divisions.
    DOI:  https://doi.org/10.1101/2023.09.04.556166
  4. Proc Natl Acad Sci U S A. 2023 Sep 26. 120(39): e2306480120
    Distinct regions of the kinesin-5 C-terminal tail are essential for mitotic spindle midzone localization and sliding force.
    Zachary R Gergely, Michele H Jones, Bojun Zhou, Cai Cash, J Richard McIntosh, Meredith D Betterton.
      Kinesin-5 motor proteins play essential roles during mitosis in most organisms. Their tetrameric structure and plus-end-directed motility allow them to bind to and move along antiparallel microtubules, thereby pushing spindle poles apart to assemble a bipolar spindle. Recent work has shown that the C-terminal tail is particularly important to kinesin-5 function: The tail affects motor domain structure, ATP hydrolysis, motility, clustering, and sliding force measured for purified motors, as well as motility, clustering, and spindle assembly in cells. Because previous work has focused on presence or absence of the entire tail, the functionally important regions of the tail remain to be identified. We have therefore characterized a series of kinesin-5/Cut7 tail truncation alleles in fission yeast. Partial truncation causes mitotic defects and temperature-sensitive growth, while further truncation that removes the conserved BimC motif is lethal. We compared the sliding force generated by cut7 mutants using a kinesin-14 mutant background in which some microtubules detach from the spindle poles and are pushed into the nuclear envelope. These Cut7-driven protrusions decreased as more of the tail was truncated, and the most severe truncations produced no observable protrusions. Our observations suggest that the C-terminal tail of Cut7p contributes to both sliding force and midzone localization. In the context of sequential tail truncation, the BimC motif and adjacent C-terminal amino acids are particularly important for sliding force. In addition, moderate tail truncation increases midzone localization, but further truncation of residues N-terminal to the BimC motif decreases midzone localization.
    Keywords:  fission yeast; force; kinesin-5; mitosis; truncation alleles
    DOI:  https://doi.org/10.1073/pnas.2306480120
  5. Life Sci Alliance. 2023 Dec;pii: e202302260. [Epub ahead of print]6(12):
    SiR-DNA/SiR-Hoechst-induced chromosome entanglement generates severe anaphase bridges and DNA damage.
    Girish Rajendraprasad, Sergi Rodriguez-Calado, Marin Barisic.
      SiR-DNA/SiR-Hoechst is a far-red fluorescent DNA probe that is routinely used for live-cell imaging of cell nuclei in interphase and chromosomes during mitosis. Despite being reported to induce DNA damage, SiR-DNA has been used in more than 300 research articles, covering topics like mitosis, chromatin biology, cancer research, cytoskeletal research, and DNA damage response. Here, we used live-cell imaging to perform a comprehensive analysis of the effects of SiR-DNA on mitosis of four human cell lines (RPE-1, DLD-1, HeLa, and U2OS). We report a dose-, time-, and light-dependent effect of SiR-DNA on chromosome segregation. We found that, upon the exposure to light during imaging, nanomolar concentrations of SiR-DNA induce non-centromeric chromosome entanglement that severely impairs sister chromatid segregation and spindle elongation during anaphase. This causes DNA damage that is passed forward to the following cell cycle, thereby having a detrimental effect on genome integrity. Our findings highlight the drawbacks in using SiR-DNA for investigation of late mitotic events and DNA damage-related topics and urge the use of alternative labeling strategies to study these processes.
    DOI:  https://doi.org/10.26508/lsa.202302260
  6. Curr Biol. 2023 Sep 09. pii: S0960-9822(23)01149-1. [Epub ahead of print]
    Apical PAR protein caps orient the mitotic spindle in C. elegans early embryos.
    Naomi J Stolpner, Nadia I Manzi, Thomas Su, Daniel J Dickinson.
      During embryonic development, oriented cell divisions are important for patterned tissue growth and cell fate specification. Cell division orientation is controlled in part by asymmetrically localized polarity proteins, which establish functional domains of the cell membrane and interact with microtubule regulators to position the mitotic spindle. For example, in the 8-cell mouse embryo, apical polarity proteins form caps on the outside, contact-free surface of the embryo that position the mitotic spindle to execute asymmetric cell division. A similar radial or "inside-outside" polarity is established at an early stage in many other animal embryos, but in most cases, it remains unclear how inside-outside polarity is established and how it influences downstream cell behaviors. Here, we explore inside-outside polarity in C. elegans somatic blastomeres using spatiotemporally controlled protein degradation and live embryo imaging. We show that PAR polarity proteins, which form apical caps at the center of the contact-free membrane, localize dynamically during the cell cycle and contribute to spindle orientation and proper cell positioning. Surprisingly, isolated single blastomeres lacking cell contacts are able to break symmetry and form PAR-3/atypical protein kinase C (aPKC) caps. Polarity caps form independently of actomyosin flows and microtubules and can regulate spindle orientation in cooperation with the key polarity kinase aPKC. Together, our results reveal a role for apical polarity caps in regulating spindle orientation in symmetrically dividing cells and provide novel insights into how these structures are formed.
    Keywords:  Caenorhabditis elegans; PAR proteins; cell polarity; embryo polarity; mitotic spindle orientation
    DOI:  https://doi.org/10.1016/j.cub.2023.08.069
  7. J Cell Biol. 2023 11 06. pii: e202210093. [Epub ahead of print]222(11):
    UHRF1 promotes spindle assembly and chromosome congression by catalyzing EG5 polyubiquitination.
    Xuli Qi, Youhong Liu, Yuchong Peng, Yuxin Fu, Yongming Fu, Linglong Yin, Xiong Li.
      UHRF1 is an epigenetic coordinator bridging DNA methylation and histone modifications. Additionally, UHRF1 regulates DNA replication and cell cycle, and its deletion induces G1/S or G2/M cell cycle arrest. The roles of UHRF1 in the regulation of G2/M transition remain poorly understood. UHRF1 depletion caused chromosome misalignment, thereby inducing cell cycle arrest at mitotic metaphase, and these cells exhibited the defects of spindle geometry, prominently manifested as shorter spindles. Mechanistically, UHRF1 protein directly interacts with EG5, a kinesin motor protein, during mitosis. Furthermore, UHRF1 induced EG5 polyubiquitination at the site of K1034 and further promoted the interaction of EG5 with spindle assembly factor TPX2, thereby ensuring accurate EG5 distribution to the spindles during metaphase. Our study clarifies a novel UHRF1 function as a nuclear protein catalyzing EG5 polyubiquitination for proper spindle architecture and faithful genomic transmission, which is independent of its roles in epigenetic regulation and DNA damage repair inside the nucleus. These findings revealed a previously unknown mechanism of UHRF1 in controlling mitotic spindle architecture and chromosome behavior and provided mechanistic evidence for UHRF1 deletion-mediated G2/M arrest.
    DOI:  https://doi.org/10.1083/jcb.202210093
  8. PLoS Genet. 2023 Sep 21. 19(9): e1010951
    Cell cycle-dependent organization of a bacterial centromere through multi-layered regulation of the ParABS system.
    Jovana Kaljević, Coralie Tesseur, Tung B K Le, Géraldine Laloux.
      The accurate distribution of genetic material is crucial for all organisms. In most bacteria, chromosome segregation is achieved by the ParABS system, in which the ParB-bound parS sequence is actively partitioned by ParA. While this system is highly conserved, its adaptation in organisms with unique lifestyles and its regulation between developmental stages remain largely unexplored. Bdellovibrio bacteriovorus is a predatory bacterium proliferating through polyploid replication and non-binary division inside other bacteria. Our study reveals the subcellular dynamics and multi-layered regulation of the ParABS system, coupled to the cell cycle of B. bacteriovorus. We found that ParA:ParB ratios fluctuate between predation stages, their balance being critical for cell cycle progression. Moreover, the parS chromosomal context in non-replicative cells, combined with ParB depletion at cell division, critically contribute to the unique cell cycle-dependent organization of the centromere in this bacterium, highlighting new levels of complexity in chromosome segregation and cell cycle control.
    DOI:  https://doi.org/10.1371/journal.pgen.1010951
  9. Elife. 2023 Sep 20. pii: e86709. [Epub ahead of print]12
    Single molecule analysis of CENP-A chromatin by high-speed atomic force microscopy.
    Daniël P Melters, Keir C Neuman, Reda S Bentahar, Tatini Rakshit, Yamini Dalal.
      Chromatin accessibility is modulated in a variety of ways to create open and closed chromatin states, both of which are critical for eukaryotic gene regulation. At the single molecule level, how accessibility is regulated of the chromatin fiber composed of canonical or variant nucleosomes is a fundamental question in the field. Here, we developed a single-molecule tracking method where we could analyze thousands of canonical H3 and centromeric variant nucleosomes imaged by high-speed atomic force microscopy. This approach allowed us to investigate how changes in nucleosome dynamics in vitro inform us about transcriptional potential in vivo. By high-speed atomic force microscopy, we tracked chromatin dynamics in real time and determined the mean square displacement and diffusion constant for the variant centromeric CENP-A nucleosome. Furthermore, we found that an essential kinetochore protein CENP-C reduces the diffusion constant and mobility of centromeric nucleosomes along the chromatin fiber. We subsequently interrogated how CENP-C modulates CENP-A chromatin dynamics in vivo. Overexpressing CENP-C resulted in reduced centromeric transcription and impaired loading of new CENP-A molecules. From these data, we speculate that factors altering nucleosome mobility in vitro, also correspondingly alter transcription in vivo. Subsequently, we propose a model in which variant nucleosomes encode their own diffusion kinetics and mobility, and where binding partners can suppress or enhance nucleosome mobility.
    Keywords:  chromatin; chromosomes; epigenetics; gene expression; high-speed AFM; human; none; nucleosomes; single-molecule
    DOI:  https://doi.org/10.7554/eLife.86709
  10. Genetics. 2023 Sep 19. pii: iyad169. [Epub ahead of print]
    Aspergillus SUMOylation mutants exhibit chromosome-segregation defects including chromatin bridges.
    Jun Zhang, Rongde Qiu, Baronger D Bieger, C Elizabeth Oakley, Berl R Oakley, Martin J Egan, Xin Xiang.
      Functions of protein SUMOylation remain incompletely understood in different cell types. Via forward genetics, here we identified ubaBQ247*, a loss-of-function mutation in a SUMO-activation enzyme UbaB in the filamentous fugus Aspergillus nidulans. The ubaBQ247*, ΔubaB and ΔsumO mutants all produce abnormal chromatin bridges, indicating the importance of SUMOylation in the completion of chromosome segregation. The bridges are enclosed by nuclear membrane containing peripheral nuclear-pore-complex proteins that normally get dispersed during mitosis, and the bridges are also surrounded by cytoplasmic microtubules typical of interphase cells. Time-lapse sequences further indicate that most bridges persist through interphase prior to the next mitosis, and anaphase chromosome segregation can produce new bridges that persist into the next interphase. When the first mitosis happens at a higher temperature of 42°C, SUMOylation deficiency produces not only chromatin bridges but also many abnormally shaped single nuclei that fail to divide. UbaB-GFP localizes to interphase nuclei just like the previously studied SumO-GFP, but the nuclear signals disappear during mitosis when the nuclear pores are partially open, and the signals reappear after mitosis. The nuclear localization is consistent with many SUMO-targets being nuclear proteins. Finally, although the budding yeast SUMOylation machinery interacts with LIS1, a protein critical for dynein activation, loss of SUMOylation does not cause any obvious defect in dynein-mediated transport of nuclei and early endosomes, indicating that SUMOylation is unnecessary for dynein activation in A. nidulans.
    Keywords:   Aspergillus nidulans ; SUMOylation; anaphase bridges; chromatin bridges; dynein; mitosis
    DOI:  https://doi.org/10.1093/genetics/iyad169
  11. Exp Cell Res. 2023 Sep 17. pii: S0014-4827(23)00331-2. [Epub ahead of print]432(1): 113783
    Phosphotyrosine proteomics in cells synchronized at monopolar cytokinesis reveals EphA2 as functioning in cytokinesis.
    Nanami Hasegawa, Mayue Hongo, Misaki Okada, Takahisa Kuga, Yuichi Abe, Jun Adachi, Takeshi Tomonaga, Naoto Yamaguchi, Yuji Nakayama.
      Cytokinesis is the final step of the cell division in which cellular components are separated into two daughter cells. This process is regulated through the phosphorylation of different classes of proteins by serine/threonine (Ser/Thr) kinases such as Aurora B and Polo-like kinase 1 (PLK1). Conversely, the role of phosphorylation at tyrosine residues during cytokinesis has not been studied in detail yet. In this study, we performed a phosphotyrosine proteomic analysis of cells undergoing monopolar cytokinesis synchronized by using the Eg5 inhibitor (+)-S-trityl-l-cysteine (STLC) and the CDK1 inhibitor RO-3306. Phosphotyrosine proteomics gave 362 tyrosine-phosphorylated peptides. Western blot analysis of proteins revealed tyrosine phosphorylation in mitogen-activated protein kinase 14 (MAPK14), vimentin, ephrin type-A receptor 2 (EphA2), and myelin protein zero-like protein 1 (MPZL1) during monopolar cytokinesis. Additionally, we demonstrated that EphA2, a protein with unknown function during cytokinesis, is involved in cytokinesis. EphA2 knockdown accelerated epithelial cell transforming 2 (Ect2) knockdown-induced multinucleation, suggesting that EphA2 plays a role in cytokinesis in a particular situation. The list also included many proteins previously reported to play roles during cytokinesis. These results evidence that the identified phosphopeptides facilitate the identification of novel tyrosine phosphorylation signaling involved in regulating cytokinesis.
    Keywords:  EphA2; Monopolar cytokinesis; Phosphotyrosine proteomics; RO-3306; STLC
    DOI:  https://doi.org/10.1016/j.yexcr.2023.113783
  12. Mol Cell Endocrinol. 2023 Sep 18. pii: S0303-7207(23)00220-4. [Epub ahead of print] 112069
    Mitotic genome-bookmarking by nuclear hormone receptors: A novel dimension in epigenetic reprogramming and disease assessment.
    Sheeba Rizvi, Ayushi Chhabra, Anjali Tripathi, Rakesh K Tyagi.
      Arrival of multi-colored fluorescent proteins and advances in live cell imaging has immensely contributed to our understanding of intracellular trafficking of nuclear receptors and their roles in gene regulatory functions. These regulatory events need to be faithfully propagated from progenitor to progeny cells. This is corroborated by multiple converging mechanisms that include histone modifications and lately, the phenomenon of 'mitotic genome-bookmarking' by specific transcription factors. This phenomenon refers to the retention and feed-forward transmission of progenitor's architectural blueprint of active transcription status which is silenced and preserved during mitosis. Upon mitotic exit, this phenomenon ensures accurate reactivation of transcriptome, proteome, cellular traits and phenotypes in the progeny cells. In addition to diverse modes of genome-bookmarking by nuclear receptors, a correlation between disease-associated receptor polymorphism and disruption of this phenomenon is apparent. However, breakthrough technologies shall reveal finer details of this phenomenon to help achieve normalcy in receptor-specific diseases.
    Keywords:  Genome-bookmarking; Mitosis; Mitotic coating; Nuclear hormone receptor; Receptor polymorphism; Receptor-chromatin association
    DOI:  https://doi.org/10.1016/j.mce.2023.112069
  13. Cell Rep. 2023 Sep 18. pii: S2211-1247(23)01157-9. [Epub ahead of print]42(9): 113145
    Unannotated microprotein EMBOW regulates the interactome and chromatin and mitotic functions of WDR5.
    Yanran Chen, Haomiao Su, Jianing Zhao, Zhenkun Na, Kevin Jiang, Antonella Bacchiocchi, Ken H Loh, Ruth Halaban, Zhentian Wang, Xiongwen Cao, Sarah A Slavoff.
      The conserved WD40-repeat protein WDR5 interacts with multiple proteins both inside and outside the nucleus. However, it is currently unclear whether and how the distribution of WDR5 between complexes is regulated. Here, we show that an unannotated microprotein EMBOW (endogenous microprotein binder of WDR5) dually encoded in the human SCRIB gene interacts with WDR5 and regulates its binding to multiple interaction partners, including KMT2A and KIF2A. EMBOW is cell cycle regulated, with two expression maxima at late G1 phase and G2/M phase. Loss of EMBOW decreases WDR5 interaction with KIF2A, aberrantly shortens mitotic spindle length, prolongs G2/M phase, and delays cell proliferation. In contrast, loss of EMBOW increases WDR5 interaction with KMT2A, leading to WDR5 binding to off-target genes, erroneously increasing H3K4me3 levels, and activating transcription of these genes. Together, these results implicate EMBOW as a regulator of WDR5 that regulates its interactions and prevents its off-target binding in multiple contexts.
    Keywords:  CP: Cell biology; CP: Molecular biology; WDR5; histone H3K4me3; microprotein; mitosis; transcription
    DOI:  https://doi.org/10.1016/j.celrep.2023.113145
  14. Nucleic Acids Res. 2023 Sep 22. pii: gkad766. [Epub ahead of print]
    The TRIM69-MST2 signaling axis regulates centrosome dynamics and chromosome segregation.
    Yilin Wang, Patrik Risteski, Yang Yang, Huan Chen, Gaith Droby, Andrea Walens, Deepika Jayaprakash, Melissa Troester, Laura Herring, Jonathan Chernoff, Iva M Tolić, Jessica Bowser, Cyrus Vaziri.
      Stringent control of centrosome duplication and separation is important for preventing chromosome instability. Structural and numerical alterations in centrosomes are hallmarks of neoplastic cells and contribute to tumorigenesis. We show that a Centrosome Amplification 20 (CA20) gene signature is associated with high expression of the Tripartite Motif (TRIM) family member E3 ubiquitin ligase, TRIM69. TRIM69-ablation in cancer cells leads to centrosome scattering and chromosome segregation defects. We identify Serine/threonine-protein kinase 3 (MST2) as a new direct binding partner of TRIM69. TRIM69 redistributes MST2 to the perinuclear cytoskeleton, promotes its association with Polo-like kinase 1 (PLK1) and stimulates MST2 phosphorylation at S15 (a known PLK1 phosphorylation site that is critical for centrosome disjunction). TRIM69 also promotes microtubule bundling and centrosome segregation that requires PRC1 and DYNEIN. Taken together, we identify TRIM69 as a new proximal regulator of distinct signaling pathways that regulate centrosome dynamics and promote bipolar mitosis.
    DOI:  https://doi.org/10.1093/nar/gkad766
  15. Proc Natl Acad Sci U S A. 2023 Sep 26. 120(39): e2303752120
    SETD2 safeguards the genome against isochromosome formation.
    Frank M Mason, Emily S Kounlavong, Anteneh T Tebeje, Rashmi Dahiya, Tiffany Guess, Abid Khan, Logan Vlach, Stephen R Norris, Courtney A Lovejoy, Ruhee Dere, Brian D Strahl, Ryoma Ohi, Peter Ly, Cheryl Lyn Walker, W Kimryn Rathmell.
      Isochromosomes are mirror-imaged chromosomes with simultaneous duplication and deletion of genetic material which may contain two centromeres to create isodicentric chromosomes. Although isochromosomes commonly occur in cancer and developmental disorders and promote genome instability, mechanisms that prevent isochromosomes are not well understood. We show here that the tumor suppressor and methyltransferase SETD2 is essential to prevent these errors. Using cellular and cytogenetic approaches, we demonstrate that loss of SETD2 or its epigenetic mark, histone H3 lysine 36 trimethylation (H3K36me3), results in the formation of isochromosomes as well as isodicentric and acentric chromosomes. These defects arise during DNA replication and are likely due to faulty homologous recombination by RAD52. These data provide a mechanism for isochromosome generation and demonstrate that SETD2 and H3K36me3 are essential to prevent the formation of this common mutable chromatin structure known to initiate a cascade of genomic instability in cancer.
    Keywords:  chromosome; epigenetics; intratumoral heterogeneity; isochromosome; mitosis
    DOI:  https://doi.org/10.1073/pnas.2303752120
  16. Commun Biol. 2023 Sep 21. 6(1): 963
    The localization of centromere protein A is conserved among tissues.
    Eleonora Cappelletti, Francesca M Piras, Lorenzo Sola, Marco Santagostino, Jessica L Petersen, Rebecca R Bellone, Carrie J Finno, Sichong Peng, Ted S Kalbfleisch, Ernest Bailey, Solomon G Nergadze, Elena Giulotto.
      Centromeres are epigenetically specified by the histone H3 variant CENP-A. Although mammalian centromeres are typically associated with satellite DNA, we previously demonstrated that the centromere of horse chromosome 11 (ECA11) is completely devoid of satellite DNA. We also showed that the localization of its CENP-A binding domain is not fixed but slides within an about 500 kb region in different individuals, giving rise to positional alleles. These epialleles are inherited as Mendelian traits but their position can move in one generation. It is still unknown whether centromere sliding occurs during meiosis or during development. Here, we first improve the sequence of the ECA11 centromeric region in the EquCab3.0 assembly. Then, to test whether centromere sliding may occur during development, we map the CENP-A binding domains of ECA11 using ChIP-seq in five tissues of different embryonic origin from the four horses of the equine FAANG (Functional Annotation of ANimal Genomes) consortium. Our results demonstrate that the centromere is localized in the same region in all tissues, suggesting that the position of the centromeric domain is maintained during development.
    DOI:  https://doi.org/10.1038/s42003-023-05335-7
  17. Chromosome Res. 2023 Sep 18. 31(4): 28
    Disentangling the roles of aneuploidy, chromosomal instability and tumour heterogeneity in developing resistance to cancer therapies.
    Joana Reis Andrade, Annie Dinky Gallagher, Jovanna Maharaj, Sarah Elizabeth McClelland.
      Aneuploidy is defined as the cellular state of having a number of chromosomes that deviates from a multiple of the normal haploid chromosome number of a given organism. Aneuploidy can be present in a static state: Down syndrome individuals stably maintain an extra copy of chromosome 21 in their cells. In cancer cells, however, aneuploidy is usually present in combination with chromosomal instability (CIN) which leads to a continual generation of new chromosomal alterations and the development of intratumour heterogeneity (ITH). The prevalence of cells with specific chromosomal alterations is further shaped by evolutionary selection, for example, during the administration of cancer therapies. Aneuploidy, CIN and ITH have each been individually associated with poor prognosis in cancer, and a wealth of evidence suggests they contribute, either alone or in combination, to cancer therapy resistance by providing a reservoir of potential resistant states, or the ability to rapidly evolve resistance. A full understanding of the contribution and interplay between aneuploidy, CIN and ITH is required to tackle therapy resistance in cancer patients. However, these characteristics often co-occur and are intrinsically linked, presenting a major challenge to defining their individual contributions. Moreover, their accurate measurement in both experimental and clinical settings is a technical hurdle. Here, we attempt to deconstruct the contribution of the individual and combined roles of aneuploidy, CIN and ITH to therapy resistance in cancer, and outline emerging approaches to measure and disentangle their roles as a step towards integrating these principles into cancer therapeutic strategy.
    Keywords:  Aneuploidy; cancer; chromosomal instability; intratumour heterogeneity; therapy resistance; tumour evolution
    DOI:  https://doi.org/10.1007/s10577-023-09737-5
  18. PLoS Biol. 2023 Sep 18. 21(9): e3002310
    Selective retention of dysfunctional mitochondria during asymmetric cell division in yeast.
    Xenia Chelius, Veronika Bartosch, Nathalie Rausch, Magdalena Haubner, Jana Schramm, Ralf J Braun, Till Klecker, Benedikt Westermann.
      Decline of mitochondrial function is a hallmark of cellular aging. To counteract this process, some cells inherit mitochondria asymmetrically to rejuvenate daughter cells. The molecular mechanisms that control this process are poorly understood. Here, we made use of matrix-targeted D-amino acid oxidase (Su9-DAO) to selectively trigger oxidative damage in yeast mitochondria. We observed that dysfunctional mitochondria become fusion-incompetent and immotile. Lack of bud-directed movements is caused by defective recruitment of the myosin motor, Myo2. Intriguingly, intact mitochondria that are present in the same cell continue to move into the bud, establishing that quality control occurs directly at the level of the organelle in the mother. The selection of healthy organelles for inheritance no longer works in the absence of the mitochondrial Myo2 adapter protein Mmr1. Together, our data suggest a mechanism in which the combination of blocked fusion and loss of motor protein ensures that damaged mitochondria are retained in the mother cell to ensure rejuvenation of the bud.
    DOI:  https://doi.org/10.1371/journal.pbio.3002310
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