bims-micesi 2023-07-30 papers

bims-micesi

Biomed News

on Mitotic cell signalling

Issue of 2023–07–30
eleven papers selected by
Valentina Piano, Uniklinik Köln

HURP localization in metaphase is the result of a multi-step process requiring its phosphorylation at Ser627 residue.
Cryo-EM structure of the complete inner kinetochore of the budding yeast point centromere.
Microtubule nucleation for spindle assembly: one molecule at a time.
Histone H3K79 methylation by DOT1L promotes Aurora B localization at centromeres in mitosis.
Cell division visualized: barley reporter lines for chromosome and microtubule dynamics.
The diverging role of CDC14B: from mitotic exit in yeast to cell fate control in humans.
The Role of Mitochondrial Dynamics and Mitotic Fission in Regulating the Cell Cycle in Cancer and Pulmonary Arterial Hypertension: Implications for Dynamin-Related Protein 1 and Mitofusin2 in Hyperproliferative Diseases.
SYS-1/beta-catenin inheritance and regulation by Wnt-signaling during asymmetric cell division.
Mad2 is dispensable for accurate chromosome segregation but becomes essential when oocytes are subjected to environmental stress.
Spindle Position Checkpoint Kinase Kin4 Regulates Organelle Transport in Saccharomyces cerevisiae.
A comprehensive multi-domain dataset for mitotic figure detection.

Front Cell Dev Biol. 2023 ;11 981425

HURP localization in metaphase is the result of a multi-step process requiring its phosphorylation at Ser627 residue.

Stylianos Didaskalou, Christos Efstathiou, Sotirios Galtsidis, Ilοna Kesisova, Aliaksandr Halavatyi, Tountzai Elmali, Avgi Tsolou, Andreas Girod, Maria Koffa.

  Faithful chromosome segregation during cell division requires accurate mitotic spindle formation. As mitosis occurs rapidly within the cell cycle, the proteins involved in mitotic spindle assembly undergo rapid changes, including their interactions with other proteins. The proper localization of the HURP protein on the kinetochore fibers, in close proximity to chromosomes, is crucial for ensuring accurate congression and segregation of chromosomes. In this study, we employ photoactivation and FRAP experiments to investigate the impact of alterations in microtubule flux and phosphorylation of HURP at the Ser627 residue on its dynamics. Furthermore, through immunoprecipitations assays, we demonstrate the interactions of HURP with various proteins, such as TPX2, Aurora A, Eg5, Dynein, Kif5B, and Importin β, in mammalian cells during mitosis. We also find that phosphorylation of HURP at Ser627 regulates its interaction with these partners during mitosis. Our findings suggest that HURP participates in at least two distinct complexes during metaphase to ensure its proper localization in close proximity to chromosomes, thereby promoting the bundling and stabilization of kinetochore fibers.

Keywords:  Aurora A; FRAP (fluorescence recovery after photobleaching); HURP dynamics; HURP localization; HURP phosphorylation; TPX2; mitosis; photoactivation

DOI:  https://doi.org/10.3389/fcell.2023.981425
Sci Adv. 2023 Jul 28. 9(30): eadg7480

Cryo-EM structure of the complete inner kinetochore of the budding yeast point centromere.

Tom Dendooven, Ziguo Zhang, Jing Yang, Stephen H McLaughlin, Johannes Schwab, Sjors H W Scheres, Stanislau Yatskevich, David Barford.

The point centromere of budding yeast specifies assembly of the large kinetochore complex to mediate chromatid segregation. Kinetochores comprise the centromere-associated inner kinetochore (CCAN) complex and the microtubule-binding outer kinetochore KNL1-MIS12-NDC80 (KMN) network. The budding yeast inner kinetochore also contains the DNA binding centromere-binding factor 1 (CBF1) and CBF3 complexes. We determined the cryo-electron microscopy structure of the yeast inner kinetochore assembled onto the centromere-specific centromere protein A nucleosomes (CENP-ANuc). This revealed a central CENP-ANuc with extensively unwrapped DNA ends. These free DNA duplexes bind two CCAN protomers, one of which entraps DNA topologically, positioned on the centromere DNA element I (CDEI) motif by CBF1. The two CCAN protomers are linked through CBF3 forming an arch-like configuration. With a structural mechanism for how CENP-ANuc can also be linked to KMN involving only CENP-QU, we present a model for inner kinetochore assembly onto a point centromere and how it organizes the outer kinetochore for chromosome attachment to the mitotic spindle.

DOI: https://doi.org/10.1126/sciadv.adg7480
Trends Biochem Sci. 2023 Jul 21. pii: S0968-0004(23)00143-3. [Epub ahead of print]

Microtubule nucleation for spindle assembly: one molecule at a time.

Jodi Kraus, Raymundo Alfaro-Aco, Bernardo Gouveia, Sabine Petry.

  The cell orchestrates the dance of chromosome segregation with remarkable speed and fidelity. The mitotic spindle is built from scratch after interphase through microtubule (MT) nucleation, which is dependent on the γ-tubulin ring complex (γ-TuRC), the universal MT template. Although several MT nucleation pathways build the spindle framework, the question of when and how γ-TuRC is targeted to these nucleation sites in the spindle and subsequently activated remains an active area of investigation. Recent advances facilitated the discovery of new MT nucleation effectors and their mechanisms of action. In this review, we illuminate each spindle assembly pathway and subsequently consider how the pathways are merged to build a spindle.

Keywords:  CDK5RAP2; TPX2; XMAP215; augmin; branching MT nucleation; spindle assembly factors (SAFs); γ-tubulin ring complex (γ-TuRC)

DOI:  https://doi.org/10.1016/j.tibs.2023.06.004
Cell Rep. 2023 Jul 25. pii: S2211-1247(23)00896-3. [Epub ahead of print]42(8): 112885

Histone H3K79 methylation by DOT1L promotes Aurora B localization at centromeres in mitosis.

Dan Yang, Yanji He, Renyan Li, Zhenting Huang, Yong Zhou, Yingxu Shi, Zhongliang Deng, Jingxian Wu, Yanfei Gao.

  Centromere localization of the chromosome passenger complex (CPC) is paramount for achieving accurate sister chromosome segregation in mitosis. Although it has been widely recognized that the recruitment of CPC is directly regulated by two histone codes, phosphorylation of histone H3 at threonine 3 (H3T3ph) and phosphorylation of histone H2A at threonine 120 (H2AT120ph), the regulation of CPC localization by other histone codes remains elusive. We show that dysfunction of disruptor of telomeric silencing 1 like (DOT1L) leads to mislocation of the CPC in prometaphase, caused by disturbing the level of H3T3ph and its reader Survivin. This cascade is initiated by over-dephosphorylation of H3T3ph mediated by the phosphatase RepoMan-PP1, whose scaffold RepoMan translocalizes to chromosomes, while the level of H3K79me2/3 is diminished. Together, our findings uncover a biological function of DOT1L and H3K79 methylation in mitosis and give insight into how genomic stability is coordinated by different histone codes.

Keywords:  CP: Cell biology; CP: Molecular biology; DOT1L; H3K79 methylation; H3T3 phosphorylation; aneuploidy; chromosome passenger complex

DOI:  https://doi.org/10.1016/j.celrep.2023.112885
Plant J. 2023 08;115(3): 600-601

Cell division visualized: barley reporter lines for chromosome and microtubule dynamics.

Gwendolyn K Kirschner.

DOI: https://doi.org/10.1111/tpj.16392
EMBO J. 2023 Jul 26. e114364

The diverging role of CDC14B: from mitotic exit in yeast to cell fate control in humans.

Patrick Partscht, Elmar Schiebel.

  CDC14, originally identified as crucial mediator of mitotic exit in budding yeast, belongs to the family of dual-specificity phosphatases (DUSPs) that are present in most eukaryotes. Contradicting data have sparked a contentious discussion whether a cell cycle role is conserved in the human paralogs CDC14A and CDC14B but possibly masked due to redundancy. Subsequent studies on CDC14A and CDC14B double knockouts in human and mouse demonstrated that CDC14 activity is dispensable for mitotic progression in higher eukaryotes and instead suggested functional specialization. In this review, we provide a comprehensive overview of our current understanding of how faithful cell division is linked to phosphorylation and dephosphorylation and compare functional similarities and divergences between the mitotic phosphatases CDC14, PP2A, and PP1 from yeast and higher eukaryotes. Furthermore, we review the latest discoveries on CDC14B, which identify this nuclear phosphatase as a key regulator of gene expression and reveal its role in neuronal development. Finally, we discuss CDC14B functions in meiosis and possible implications in other developmental processes.

Keywords:  CDC14; PP2A; cell cycle; gene expression; protein phosphorylation

DOI:  https://doi.org/10.15252/embj.2023114364
Cells. 2023 Jul 20. pii: 1897. [Epub ahead of print]12(14):

The Role of Mitochondrial Dynamics and Mitotic Fission in Regulating the Cell Cycle in Cancer and Pulmonary Arterial Hypertension: Implications for Dynamin-Related Protein 1 and Mitofusin2 in Hyperproliferative Diseases.

Pierce Colpman, Asish Dasgupta, Stephen L Archer.

  Mitochondria, which generate ATP through aerobic respiration, also have important noncanonical functions. Mitochondria are dynamic organelles, that engage in fission (division), fusion (joining) and translocation. They also regulate intracellular calcium homeostasis, serve as oxygen-sensors, regulate inflammation, participate in cellular and organellar quality control and regulate the cell cycle. Mitochondrial fission is mediated by the large GTPase, dynamin-related protein 1 (Drp1) which, when activated, translocates to the outer mitochondrial membrane (OMM) where it interacts with binding proteins (Fis1, MFF, MiD49 and MiD51). At a site demarcated by the endoplasmic reticulum, fission proteins create a macromolecular ring that divides the organelle. The functional consequence of fission is contextual. Physiological fission in healthy, nonproliferating cells mediates organellar quality control, eliminating dysfunctional portions of the mitochondria via mitophagy. Pathological fission in somatic cells generates reactive oxygen species and triggers cell death. In dividing cells, Drp1-mediated mitotic fission is critical to cell cycle progression, ensuring that daughter cells receive equitable distribution of mitochondria. Mitochondrial fusion is regulated by the large GTPases mitofusin-1 (Mfn1) and mitofusin-2 (Mfn2), which fuse the OMM, and optic atrophy 1 (OPA-1), which fuses the inner mitochondrial membrane. Mitochondrial fusion mediates complementation, an important mitochondrial quality control mechanism. Fusion also favors oxidative metabolism, intracellular calcium homeostasis and inhibits cell proliferation. Mitochondrial lipids, cardiolipin and phosphatidic acid, also regulate fission and fusion, respectively. Here we review the role of mitochondrial dynamics in health and disease and discuss emerging concepts in the field, such as the role of central versus peripheral fission and the potential role of dynamin 2 (DNM2) as a fission mediator. In hyperproliferative diseases, such as pulmonary arterial hypertension and cancer, Drp1 and its binding partners are upregulated and activated, positing mitochondrial fission as an emerging therapeutic target.

Keywords:  apoptosis; cancer; cardiolipin (CL); dynamin 2 (DNM2); dynamin-related protein 1 (Drp1); mitochondrial dynamics protein of 49 kDa (MiD49); mitochondrial dynamics protein of 51 kDa (MiD51); mitochondrial fission factor (MFF); mitochondrial fission protein 1 (Fis1); mitophagy; mitotic fission; phosphatidic acid (PA); pulmonary arterial hypertension

DOI:  https://doi.org/10.3390/cells12141897
bioRxiv. 2023 Jul 21. pii: 2023.07.21.550069. [Epub ahead of print]

SYS-1/beta-catenin inheritance and regulation by Wnt-signaling during asymmetric cell division.

Maria F Valdes Michel, Bryan T Phillips.

Asymmetric cell division (ACD) allows daughter cells of a polarized mother to acquire different developmental fates. In C. elegans , the Wnt/β-catenin Asymmetry (WβA) pathway oversees many embryonic and larval ACDs; here, a Wnt gradient induces an asymmetric distribution of Wnt signaling components within the dividing mother cell. One terminal nuclear effector of the WβA pathway is the transcriptional activator SYS-1/β-catenin. SYS-1 is sequentially negatively regulated during ACD; first by centrosomal regulation and subsequent proteasomal degradation and second by asymmetric activity of the β-catenin "destruction complex" in one of the two daughter cells, which decreases SYS-1 levels in the absence of WβA signaling. However, the extent to which mother cell SYS-1 influences cell fate decisions of the daughters is unknown. Here, we quantify inherited SYS-1 in the differentiating daughter cells and the role of SYS-1 inheritance in Wnt-directed ACD. Photobleaching experiments demonstrate the GFP::SYS-1 present in daughter cell nuclei is comprised of inherited and de novo translated SYS-1 pools. We used a photoconvertible DENDRA2::SYS-1, to directly observe the dynamics of inherited SYS-1. Photoconversion during mitosis reveals that SYS-1 clearance at the centrosome preferentially degrades older SYS-1, and this accumulation is regulated via dynein trafficking. Photoconversion of the EMS cell during Wnt-driven ACD shows daughter cell inheritance of mother cell SYS-1. Additionally, loss of centrosomal SYS-1 increased inherited SYS-1 and, surprisingly, loss of centrosomal SYS-1 also resulted in increased levels of de novo SYS-1 in both EMS daughter cells. Lastly, we show that daughter cell negative regulation of SYS-1 via the destruction complex member APR-1/APC is key to limit both the de novo and the inherited SYS-1 pools in both the E and the MS cells. We conclude that regulation of both inherited and newly translated SYS-1 via centrosomal processing in the mother cell and daughter cell regulation via Wnt signaling are critical to maintain sister SYS-1 asymmetry during ACD.

DOI: https://doi.org/10.1101/2023.07.21.550069
Development. 2023 Jul 15. pii: dev201398. [Epub ahead of print]150(14):

Mad2 is dispensable for accurate chromosome segregation but becomes essential when oocytes are subjected to environmental stress.

Jing-Yi Qiao, Qian Zhou, Ke Xu, Wei Yue, Wen-Long Lei, Yuan-Yuan Li, Lin-Jian Gu, Ying-Chun Ouyang, Yi Hou, Heide Schatten, Tie-Gang Meng, Zhen-Bo Wang, Qing-Yuan Sun.

  Accurate chromosome segregation, monitored by the spindle assembly checkpoint (SAC), is crucial for the production of euploid cells. Previous in vitro studies by us and others showed that Mad2, a core member of the SAC, performs a checkpoint function in oocyte meiosis. Here, through an oocyte-specific knockout approach in mouse, we reconfirmed that Mad2-deficient oocytes exhibit an accelerated metaphase-to-anaphase transition caused by premature degradation of securin and cyclin B1 and subsequent activation of separase in meiosis I. However, it was surprising that the knockout mice were completely fertile and the resulting oocytes were euploid. In the absence of Mad2, other SAC proteins, including BubR1, Bub3 and Mad1, were normally recruited to the kinetochores, which likely explains the balanced chromosome separation. Further studies showed that the chromosome separation in Mad2-null oocytes was particularly sensitive to environmental changes and, when matured in vitro, showed chromosome misalignment, lagging chromosomes, and aneuploidy with premature separation of sister chromatids, which was exacerbated at a lower temperature. We reveal for the first time that Mad2 is dispensable for proper chromosome segregation but acts to mitigate environmental stress in meiotic oocytes.

Keywords:  Aneuploidy; Chromosome segregation; IVM; Mad2; Mouse; Sister chromatid; Spindle assembly checkpoint

DOI:  https://doi.org/10.1242/dev.201398
Biomolecules. 2023 Jul 10. pii: 1098. [Epub ahead of print]13(7):

Spindle Position Checkpoint Kinase Kin4 Regulates Organelle Transport in Saccharomyces cerevisiae.

Lakhan Ekal, Abdulaziz M S Alqahtani, Maya Schuldiner, Einat Zalckvar, Ewald H Hettema, Kathryn R Ayscough.

  Membrane-bound organelles play important, frequently essential, roles in cellular metabolism in eukaryotes. Hence, cells have evolved molecular mechanisms to closely monitor organelle dynamics and maintenance. The actin cytoskeleton plays a vital role in organelle transport and positioning across all eukaryotes. Studies in the budding yeast Saccharomyces cerevisiae (S. cerevisiae) revealed that a block in actomyosin-dependent transport affects organelle inheritance to daughter cells. Indeed, class V Myosins, Myo2, and Myo4, and many of their organelle receptors, have been identified as key factors in organelle inheritance. However, the spatiotemporal regulation of yeast organelle transport remains poorly understood. Using peroxisome inheritance as a proxy to study actomyosin-based organelle transport, we performed an automated genome-wide genetic screen in S. cerevisiae. We report that the spindle position checkpoint (SPOC) kinase Kin4 and, to a lesser extent, its paralog Frk1, regulates peroxisome transport, independent of their role in the SPOC. We show that Kin4 requires its kinase activity to function and that both Kin4 and Frk1 protect Inp2, the peroxisomal Myo2 receptor, from degradation in mother cells. In addition, vacuole inheritance is also affected in kin4/frk1-deficient cells, suggesting a common regulatory mechanism for actin-based transport for these two organelles in yeast. More broadly our findings have implications for understanding actomyosin-based transport in cells.

Keywords:  actin cytoskeleton; class V myosin; mitotic exit network (MEN); organelle transport; peroxisome; spindle position checkpoint (SPOC)

DOI:  https://doi.org/10.3390/biom13071098
Sci Data. 2023 Jul 25. 10(1): 484

A comprehensive multi-domain dataset for mitotic figure detection.

Marc Aubreville, Frauke Wilm, Nikolas Stathonikos, Katharina Breininger, Taryn A Donovan, Samir Jabari, Mitko Veta, Jonathan Ganz, Jonas Ammeling, Paul J van Diest, Robert Klopfleisch, Christof A Bertram.

The prognostic value of mitotic figures in tumor tissue is well-established for many tumor types and automating this task is of high research interest. However, especially deep learning-based methods face performance deterioration in the presence of domain shifts, which may arise from different tumor types, slide preparation and digitization devices. We introduce the MIDOG++ dataset, an extension of the MIDOG 2021 and 2022 challenge datasets. We provide region of interest images from 503 histological specimens of seven different tumor types with variable morphology with in total labels for 11,937 mitotic figures: breast carcinoma, lung carcinoma, lymphosarcoma, neuroendocrine tumor, cutaneous mast cell tumor, cutaneous melanoma, and (sub)cutaneous soft tissue sarcoma. The specimens were processed in several laboratories utilizing diverse scanners. We evaluated the extent of the domain shift by using state-of-the-art approaches, observing notable differences in single-domain training. In a leave-one-domain-out setting, generalizability improved considerably. This mitotic figure dataset is the first that incorporates a wide domain shift based on different tumor types, laboratories, whole slide image scanners, and species.

DOI: https://doi.org/10.1038/s41597-023-02327-4