bims-micesi 2024-10-06 papers

bims-micesi

Biomed News

on Mitotic cell signalling

Issue of 2024–10–06
ten papers selected by
Valentina Piano, Uniklinik Köln

CENP-C-targeted PLK-1 regulates kinetochore function in C. elegans embryos.
Cyclin A/Cdk1 promotes chromosome alignment and timely mitotic progression.
Regulation of outer kinetochore assembly during meiosis I and II by CENP-A and KNL-2/M18BP1 in C. elegans oocytes.
Interphase chromosome conformation is specified by distinct folding programs inherited via mitotic chromosomes or through the cytoplasm.
Dynamics of microcompartment formation at the mitosis-to-G1 transition.
Commitment to cytokinetic furrowing requires the coordinate activity of microtubules and Plk1.
Aurora B and Aurora C pools at two chromosomal regions collaboratively maintain chromosome alignment and prevent aneuploidy at the second meiotic division in mammalian oocytes.
Spatiotemporal regulation of MELK during mitosis.
Mitotic ER-mitochondria contact enhances mitochondrial Ca2+ influx to promote cell division.
Chromosomal instability increases radiation sensitivity.

J Cell Sci. 2024 Oct 02. pii: jcs.262327. [Epub ahead of print]

CENP-C-targeted PLK-1 regulates kinetochore function in C. elegans embryos.

Laura Bel Borja, Samuel J P Taylor, Flavie Soubigou, Federico Pelisch.

  Polo-like kinase 1 (PLK-1) is present in centrosomes, the nuclear envelope, and kinetochores and plays a significant role in meiosis and mitosis. PLK-1 depletion or inhibition has severe consequences for spindle assembly, spindle assembly checkpoint (SAC) activation, chromosome segregation, and cytokinesis. BUB-1 targets PLK-1 to the outer kinetochore and, in mammals, the inner kinetochore PLK1 targeting is mediated by the constitutive centromere associated network (CCAN). BUB1-targeted PLK-1 plays a key role in SAC activation and a SAC-independent role through targeting CDC-20. In contrast, whether there is a specific, non-redundant role for inner kinetochore targeted PLK-1 is unknown. Here, we used the C. elegans embryo to study the role of inner kinetochore PLK-1. We found that CENP-C, the sole CCAN component in C. elegans and other species, targets PLK-1 to the inner kinetochore during prometaphase and metaphase. Disruption of the CENP-C/PLK-1 interaction leads to an imbalance in kinetochore components and a defect in chromosome congression, without affecting CDC-20 recruitment. These findings indicate that PLK-1 kinetochore recruitment by CENP-C has at least partially distinct functions than outer kinetochore PLK-1, providing a platform for a better understanding of the different roles played by PLK-1 during mitosis.

Keywords:  CCAN; CENP-C; Kinetochore; MIS12; Mitosis; PLK

DOI:  https://doi.org/10.1242/jcs.262327
Mol Biol Cell. 2024 Oct 02. mbcE23120479

Cyclin A/Cdk1 promotes chromosome alignment and timely mitotic progression.

Sarah Y Valles, Shrea Bural, Kristina M Godek, Duane A Compton.

To ensure genomic fidelity a series of spatially and temporally coordinated events are executed during prometaphase of mitosis, including bipolar spindle formation, chromosome attachment to spindle microtubules at kinetochores, the correction of erroneous kinetochore-microtubule (k-MT) attachments, and chromosome congression to the spindle equator. Cyclin A/Cdk1 kinase plays a key role in destabilizing k-MT attachments during prometaphase to promote correction of erroneous k-MT attachments. However, it is unknown if Cyclin A/Cdk1 kinase regulates other events during prometaphase. Here, we investigate additional roles of Cyclin A/Cdk1 in prometaphase by using an siRNA knockdown strategy to deplete endogenous Cyclin A from human cells. We find that depleting Cyclin A significantly extends mitotic duration, specifically prometaphase, because chromosome alignment is delayed. Unaligned chromosomes display erroneous monotelic, syntelic, or lateral k-MT attachments suggesting that bioriented k-MT attachment formation is delayed in the absence of Cyclin A. Mechanistically, chromosome alignment is likely impaired because the localization of the kinetochore proteins BUB1 kinase, KNL1, and MPS1 kinase are reduced in Cyclin A-depleted cells. Moreover, we find that Cyclin A promotes BUB1 kinetochore localization independently of its role in destabilizing k-MT attachments. Thus, Cyclin A/Cdk1 facilitates chromosome alignment during prometaphase to support timely mitotic progression.

DOI: https://doi.org/10.1091/mbc.E23-12-0479
Curr Biol. 2024 Sep 26. pii: S0960-9822(24)01215-6. [Epub ahead of print]

Regulation of outer kinetochore assembly during meiosis I and II by CENP-A and KNL-2/M18BP1 in C. elegans oocytes.

Laura Bellutti, Nicolas Macaisne, Layla El Mossadeq, Thadshagine Ganeswaran, Julie C Canman, Julien Dumont.

  During cell division, chromosomes build kinetochores that attach to spindle microtubules. Kinetochores usually form at the centromeres, which contain CENP-A nucleosomes. The outer kinetochore, which is the core attachment site for microtubules, is composed of the KMN network (Knl1c, Mis12c, and Ndc80c complexes) and is recruited downstream of CENP-A and its partner CENP-C. In C. elegans oocytes, kinetochores have been suggested to form independently of CENP-A nucleosomes. Yet kinetochore formation requires CENP-C, which acts in parallel to the nucleoporin MEL-28ELYS. Here, we used a combination of RNAi and Degron-based depletion of CENP-A (or downstream CENP-C) to demonstrate that both proteins are in fact responsible for a portion of outer kinetochore assembly during meiosis I and are essential for accurate chromosome segregation. The remaining part requires the coordinated action of KNL-2 (ortholog of human M18BP1) and of the nucleoporin MEL-28ELYS. Accordingly, co-depletion of CENP-A (or CENP-C) and KNL-2M18BP1 (or MEL-28ELYS) prevented outer kinetochore assembly in oocytes during meiosis I. We further found that KNL-2M18BP1 and MEL-28ELYS are interdependent for kinetochore localization. Using engineered mutants, we demonstrated that KNL-2M18BP1 recruits MEL-28ELYS at meiotic kinetochores through a specific N-terminal domain, independently of its canonical CENP-A loading factor activity. Finally, we found that meiosis II outer kinetochore assembly was solely dependent on the canonical CENP-A/CENP-C pathway. Thus, like in most cells, outer kinetochore assembly in C. elegans oocytes depends on centromeric chromatin. However, during meiosis I, an additional KNL-2M18BP1 and MEL-28ELYS pathway acts in a non-redundant manner and in parallel to canonical centromeric chromatin.

Keywords:  CENP-A; CENP-C; centromere; chromosome segregation; holocentric; kinetochore; microtubule; oocyte meiosis

DOI:  https://doi.org/10.1016/j.cub.2024.09.004
bioRxiv. 2024 Sep 16. pii: 2024.09.16.613305. [Epub ahead of print]

Interphase chromosome conformation is specified by distinct folding programs inherited via mitotic chromosomes or through the cytoplasm.

Allana Schooley, Sergey V Venev, Vasilisa Aksenova, Emily Navarrete, Mary Dasso, Job Dekker.

Identity-specific interphase chromosome conformation must be re-established each time a cell divides. To understand how interphase folding is inherited, we developed an experimental approach that physically segregates mediators of G1 folding that are intrinsic to mitotic chromosomes from cytoplasmic factors. Proteins essential for nuclear transport, RanGAP1 and Nup93, were degraded in pro-metaphase arrested DLD-1 cells to prevent the establishment of nucleo-cytoplasmic transport during mitotic exit and isolate the decondensing mitotic chromatin of G1 daughter cells from the cytoplasm. Using this approach, we discover a transient folding intermediate entirely driven by chromosome-intrinsic factors. In addition to conventional compartmental segregation, this chromosome-intrinsic folding program leads to prominent genome-scale microcompartmentalization of mitotically bookmarked and cell type-specific cis-regulatory elements. This microcompartment conformation is formed during telophase and subsequently modulated by a second folding program driven by factors inherited through the cytoplasm in G1. This nuclear import-dependent folding program includes cohesin and factors involved in transcription and RNA processing. The combined and inter-dependent action of chromosome-intrinsic and cytoplasmic inherited folding programs determines the interphase chromatin conformation as cells exit mitosis.

DOI: https://doi.org/10.1101/2024.09.16.613305
bioRxiv. 2024 Sep 16. pii: 2024.09.16.611917. [Epub ahead of print]

Dynamics of microcompartment formation at the mitosis-to-G1 transition.

Viraat Y Goel, Nicholas G Aboreden, James M Jusuf, Haoyue Zhang, Luisa P Mori, Leonid A Mirny, Gerd A Blobel, Edward J Banigan, Anders S Hansen.

As cells exit mitosis and enter G1, mitotic chromosomes decompact and transcription is reestablished. Previously, Hi-C studies showed that essentially all interphase 3D genome features including A/B-compartments, TADs, and CTCF loops, are lost during mitosis. However, Hi-C remains insensitive to features such as microcompartments, nested focal interactions between cis -regulatory elements (CREs). We therefore applied Region Capture Micro-C to cells from mitosis to G1. Unexpectedly, we observe microcompartments in prometaphase, which further strengthen in ana/telophase before gradually weakening in G1. Loss of loop extrusion through condensin depletion differentially impacts microcompartments and large A/B-compartments, suggesting that they are partially distinct. Using polymer modeling, we show that microcompartment formation is favored by chromatin compaction and disfavored by loop extrusion activity, explaining why ana/telophase likely provides a particularly favorable environment. Our results suggest that CREs exhibit intrinsic homotypic affinity leading to microcompartment formation, which may explain transient transcriptional spiking observed upon mitotic exit.

DOI: https://doi.org/10.1101/2024.09.16.611917
bioRxiv. 2024 Sep 16. pii: 2024.09.16.612913. [Epub ahead of print]

Commitment to cytokinetic furrowing requires the coordinate activity of microtubules and Plk1.

Charles A Day, Alyssa Langfald, Tana Lukes, Hanna Middlebrook, Kevin T Vaughan, David Daniels, Edward H Hinchcliffe.

At anaphase, spindle microtubules (MTs) position the cleavage furrow and trigger actomyosin assembly by localizing the small GTPase RhoA and the scaffolding protein anillin to a narrow band along the equatorial cortex [1-6]. Using vertebrate somatic cells we examined the temporal control of furrow assembly. Although its positioning commences at anaphase onset, furrow maturation is not complete until ∼10-11 min later. The maintenance of the RhoA/anillin scaffold initially requires continuous signaling from the spindle; loss of either MTs or polo-like kinase 1 (Plk1) activity prevents proper RhoA/anillin localization to the equator, thereby disrupting furrowing. However, we find that at ∼6 min post-anaphase, the cortex becomes "committed to furrowing"; loss of either MTs or Plk1 after this stage does not prevent eventual furrowing, even though at this point the contractile apparatus has not fully matured. Also at this stage, the RhoA/anillin scaffold at the equator becomes permanent. Surprisingly, concurrent loss of both MTs and Plk1 activity following the "commitment to furrowing" stage results in persistent, asymmetric "half-furrows", with only one cortical hemisphere retaining RhoA/anillin, and undergoing ingression. This phenotype is reminiscent of asymmetric furrows caused by a physical block between spindle and cortex [7-9], or by acentric spindle positioning [10-12]. The formation of these persistent "half-furrows" suggests a potential feedback mechanism between the spindle and the cortex that maintains cortical competency along the presumptive equatorial region prior to the "commitment to furrowing" stage of cytokinesis, thereby ensuring the eventual ingression of a symmetric cleavage furrow.

DOI: https://doi.org/10.1101/2024.09.16.612913
Front Cell Dev Biol. 2024 ;12 1470981

Aurora B and Aurora C pools at two chromosomal regions collaboratively maintain chromosome alignment and prevent aneuploidy at the second meiotic division in mammalian oocytes.

Anna Kouznetsova, Sonata Valentiniene, Jian-Guo Liu, Tomoya S Kitajima, Hjalmar Brismar, Christer Höög.

  Correct chromosome segregation is essential to preserve genetic integrity. The two protein kinases, Aurora B and its meiotic homolog Aurora C, regulate attachments between chromosomal kinetochores and microtubules, thereby contributing to the accuracy of the chromosome segregation process. Here we performed a detailed examination of the localization and activity of Aurora B/C kinases, their partner Incenp and the kinetochore target Hec1, during the second meiotic division in mouse oocytes. We found that a majority of Aurora B and C changed their localization from the outer kinetochore region of chromosomes at prometaphase II to an inner central region localized between sister centromeres at metaphase II. Depletion of the Aurora B/C pool at the inner central region using the haspin kinase inhibitor 5-iodotubercidin resulted in chromosome misalignments at the metaphase II stage. To further understand the role of the Aurora B/C pool at the central region, we examined the behaviour of single chromatids, that lack a central Aurora B/C pool but retain Aurora B/C at the outer kinetochores. We found that kinetochore-microtubule attachments at single chromatids were corrected at both prometaphase II and metaphase II stages, but that single chromatids compared to paired chromatids were more prone to misalignments following treatment of oocytes with the Aurora B/C inhibitory drugs AZD1152 and GSK1070916. We conclude that the Aurora B/C pool at the inner central region stabilizes chromosome alignment during metaphase II arrest, while Aurora B/C localized at the kinetochore assist in re-establishing chromosome positioning at the metaphase plate if alignment is lost. Collaboratively these two pools prevent missegregation and aneuploidy at the second meiotic division in mammalian oocytes.

Keywords:  Aurora B; Aurora C; aneuploidy; meiosis; oocyte; second meiotic division

DOI:  https://doi.org/10.3389/fcell.2024.1470981
Front Cell Dev Biol. 2024 ;12 1406940

Spatiotemporal regulation of MELK during mitosis.

Sreemita Majumdar, Song-Tao Liu.

  Maternal Embryonic Leucine Zipper Kinase (MELK) has been studied intensively in recent years due to its overexpression in multiple cancers. However, the cell biology of MELK remains less characterized despite its well-documented association with mitosis. Here we report a distinctive pattern of human MELK that translocates from the cytoplasm to cell cortex within 3 min of anaphase onset. The cortex association lasts about 30 min till telophase. The spatiotemporal specific localization of MELK depends on the interaction between its Threonine-Proline (TP) rich domain and kinase associated 1 (KA1) domain, which is regulated by CDK1 kinase and PP4 protein phosphatase. KA1 domains are known to regulate kinase activities through various intramolecular interactions. Our results revealed a new role for KA1 domain to control subcellular localization of a protein kinase.

Keywords:  Cdk1; KA1 domain; MELK; PP4; anaphase; cell cortex

DOI:  https://doi.org/10.3389/fcell.2024.1406940
Cell Rep. 2024 Sep 28. pii: S2211-1247(24)01145-8. [Epub ahead of print]43(10): 114794

Mitotic ER-mitochondria contact enhances mitochondrial Ca2+ influx to promote cell division.

Gan Zhao, Mingkang Jia, Shicong Zhu, He Ren, Guopeng Wang, Guangwei Xin, Mengjie Sun, Xiangyang Wang, Qiaoyu Lin, Qing Jiang, Chuanmao Zhang.

  Cell division is tightly regulated and requires an expanded energy supply. However, how this energy is generated remains unclear. Here, we establish a correlation between two mitochondrial Ca2+ influx events and ATP production during mitosis. While both events promote ATP production during mitosis, the second event, the Ca2+ influx surge, is substantial. To facilitate this Ca2+ influx surge, the lamin B receptor (LBR) organizes a mitosis-specific endoplasmic reticulum (ER)-mitochondrial contact site (ERMCS), creating a rapid Ca2+ transport pathway. LBR acts as a tether, connecting the ER Ca2+ release channel IP3R with the mitochondrial VDAC2. Depletion of LBR disrupts the Ca2+ influx surge, reduces ATP production, and postpones the metaphase-anaphase transition and subsequent cell division. These findings provide insight into the mechanisms underlying mitotic energy production and supply required for cell proliferation.

Keywords:  CP: Cell biology; CP: Metabolism; Ca(2+); ER-mitochondrial contact; LBR; VDAC2; cell cycle; cell division; energy generation; metaphase-anaphase transition; mitochondria; mitosis

DOI:  https://doi.org/10.1016/j.celrep.2024.114794
bioRxiv. 2024 Sep 19. pii: 2024.09.13.612942. [Epub ahead of print]

Chromosomal instability increases radiation sensitivity.

Pippa F Cosper, Maha Paracha, Kathryn M Jones, Laura Hrycyniak, Les Henderson, Ava Bryan, Diego Eyzaguirre, Emily McCunn, Elizabeth Boulanger, Jun Wan, Kwangok P Nickel, Vanessa Horner, Rong Hu, Paul M Harari, Randall J Kimple, Beth A Weaver.

Continuous chromosome missegregation over successive mitotic divisions, known as chromosomal instability (CIN), is common in cancer. Increasing CIN above a maximally tolerated threshold leads to cell death due to loss of essential chromosomes. Here, we show in two tissue contexts that otherwise isogenic cancer cells with higher levels of CIN are more sensitive to ionizing radiation, which itself induces CIN. CIN also sensitizes HPV-positive and HPV-negative head and neck cancer patient derived xenograft (PDX) tumors to radiation. Moreover, laryngeal cancers with higher CIN prior to treatment show improved response to radiation therapy. In addition, we reveal a novel mechanism of radiosensitization by docetaxel, a microtubule stabilizing drug commonly used in combination with radiation. Docetaxel causes cell death by inducing CIN due to abnormal multipolar spindles rather than causing mitotic arrest, as previously assumed. Docetaxel-induced CIN, rather than mitotic arrest, is responsible for the enhanced radiation sensitivity observed in vitro and in vivo, challenging the mechanistic dogma of the last 40 years. These results implicate CIN as a potential biomarker and inducer of radiation response, which could provide valuable cancer therapeutic opportunities.
Statement of Significance: Cancer cells and laryngeal tumors with higher chromosome missegregation rates are more sensitive to radiation therapy, supporting chromosomal instability as a promising biomarker of radiation response.

DOI: https://doi.org/10.1101/2024.09.13.612942