bims-micesi 2022-09-25 papers

bims-micesi

Biomed News

on Mitotic cell signalling

Issue of 2022–09–25
seven papers selected by
Valentina Piano, Max Planck Institute of Molecular Physiology

On the Regulation of Mitosis by the Kinetochore, a Macromolecular Complex and Organising Hub of Eukaryotic Organisms.
Coupling of microtubule bundles isolates them from local disruptions to set the structural stability of the anaphase spindle.
CtIP Regulates Mitotic Spindle Assembly by Modulating the TPX2-Aurora A Signaling Axis.
Inositol Pyrophosphate-Controlled Kinetochore Architecture and Mitotic Entry in S. pombe.
Mitotic spindle disassembly in human cells relies on CRIPT having hierarchical redox signals.
Divergent polo boxes in KKT2 bind KKT1 to initiate the kinetochore assembly cascade in Trypanosoma brucei.
The mitotic regulator RCC2 promotes glucose metabolism through BACH1-dependent transcriptional upregulation of hexokinase II in glioma.

Subcell Biochem. 2022 ;99 235-267

On the Regulation of Mitosis by the Kinetochore, a Macromolecular Complex and Organising Hub of Eukaryotic Organisms.

Victor M Bolanos-Garcia.

  The kinetochore is the multiprotein complex of eukaryotic organisms that is assembled on mitotic or meiotic centromeres to connect centromeric DNA with microtubules. Its function involves the coordinated action of more than 100 different proteins. The kinetochore acts as an organiser hub that establishes physical connections with microtubules and centromere-associated proteins and recruits central protein components of the spindle assembly checkpoint (SAC), an evolutionarily conserved surveillance mechanism of eukaryotic organisms that detects unattached kinetochores and destabilises incorrect kinetochore-microtubule attachments. The molecular communication between the kinetochore and the SAC is highly dynamic and tightly regulated to ensure that cells can progress towards anaphase until each chromosome is properly bi-oriented on the mitotic spindle. This is achieved through an interplay of highly cooperative interactions and concerted phosphorylation/dephosphorylation events that are organised in time and space.This contribution discusses our current understanding of the function, structure and regulation of the kinetochore, in particular, how its communication with the SAC results in the amplification of specific signals to exquisitely control the eukaryotic cell cycle. This contribution also addresses recent advances in machine learning approaches, cell imaging and proteomics techniques that have enhanced our understanding of the molecular mechanisms that ensure the high fidelity and timely segregation of the genetic material every time a cell divides as well as the current challenges in the study of this fascinating molecular machine.

Keywords:  Aneuploidy; Cancer; Cell cycle regulation; Chromosome segregation; Genome stability; Kinetochore; Kinetochore-microtubule network; Macromolecular assemblies; Signal amplification; Spindle assembly checkpoint (SAC)

DOI:  https://doi.org/10.1007/978-3-031-00793-4_7
Proc Natl Acad Sci U S A. 2022 Sep 27. 119(39): e2204068119

Coupling of microtubule bundles isolates them from local disruptions to set the structural stability of the anaphase spindle.

Lina Carlini, Fioranna Renda, Melissa C Pamula, Alexey Khodjakov, Tarun M Kapoor.

  Chromosome segregation requires load-bearing interactions across kinetochore fibers and antiparallel microtubule bundles, which constitute the spindle midzone. Mechanical properties of kinetochore fibers have been characterized during metaphase, when the mitotic spindle achieves steady state. However, it has been difficult to probe the mechanics of the spindle midzone that elongates during anaphase. Here, we combine superresolution expansion and electron microscopies, lattice light-sheet imaging, and laser microsurgery to examine how midzone organization sets its mechanics. We find that individual midzone bundles extend out to multiple positions across chromosomes and form multiple apparent microtubule-based connections with each other. Across the spindle's short axis, these microtubule bundles exhibit restricted, submicrometer-amplitude motions, which are weakly correlated on <10s timescales. Severing individual midzone bundles near their center does not substantially affect positions of neighboring bundles, nor the overall structural stability of the midzone. In contrast, severing multiple midzone bundles or individual bundles at their chromosome-proximal ends significantly displaces neighboring microtubule bundles. Together, these data suggest a model wherein multiple midzone connections both reinforce its structure and mechanically isolate individual bundles from local perturbations. This feature sets the robust midzone architecture to accommodate disruptions, including those which result from lagging chromosomes, and achieve stereotypic outputs, such as proper chromosome separation.

Keywords:  anaphase; cell division; mechanics; microtubules; spindle

DOI:  https://doi.org/10.1073/pnas.2204068119
Cells. 2022 Sep 08. pii: 2814. [Epub ahead of print]11(18):

CtIP Regulates Mitotic Spindle Assembly by Modulating the TPX2-Aurora A Signaling Axis.

Wonkyung Oh, Ting Ting Wu, Seo-Yeon Jeong, Ho Jin You, Jung-Hee Lee.

  CtBP-interacting protein (CtIP) plays a critical role in controlling the homologous recombination-mediated DNA double-stranded break (DSB) repair pathway through DNA end resection, and recent studies suggest that it also plays a role in mitosis. However, the mechanism by which CtIP contributes to mitosis regulation remains elusive. Here, we show that depletion of CtIP leads to a delay in anaphase progression resulting in misaligned chromosomes, an aberrant number of centrosomes, and defects in chromosome segregation. Additionally, we demonstrate that CtIP binds and colocalizes with Targeting protein for Xklp2 (TPX2) during mitosis to regulate the recruitment of TPX2 to the spindle poles. Furthermore, depletion of CtIP resulted in both a lower concentration of Aurora A, its downstream target, and very low microtubule intensity at the spindle poles, suggesting an important role for the CtIP-TPX2-Auroa A complex in microtubule dynamics at the centrosomal spindles. Our findings reveal a novel function of CtIP in regulating spindle dynamics through interactions with TPX2 and indicate that CtIP is involved in the proper execution of the mitotic program, where deregulation may lead to chromosomal instability.

Keywords:  CtIP; TPX2; kinetochore; mitosis; spindle; spindle assembly checkpoint

DOI:  https://doi.org/10.3390/cells11182814
J Fungi (Basel). 2022 Sep 02. pii: 933. [Epub ahead of print]8(9):

Inositol Pyrophosphate-Controlled Kinetochore Architecture and Mitotic Entry in S. pombe.

Natascha Andrea Kuenzel, Abel R Alcázar-Román, Adolfo Saiardi, Simon M Bartsch, Sarune Daunaraviciute, Dorothea Fiedler, Ursula Fleig.

  Inositol pyrophosphates (IPPs) comprise a specific class of signaling molecules that regulate central biological processes in eukaryotes. The conserved Vip1/PPIP5K family controls intracellular IP8 levels, the highest phosphorylated form of IPPs present in yeasts, as it has both inositol kinase and pyrophosphatase activities. Previous studies have shown that the fission yeast S. pombe Vip1/PPIP5K family member Asp1 impacts chromosome transmission fidelity via the modulation of spindle function. We now demonstrate that an IP8 analogue is targeted by endogenous Asp1 and that cellular IP8 is subject to cell cycle control. Mitotic entry requires Asp1 kinase function and IP8 levels are increased at the G2/M transition. In addition, the kinetochore, the conductor of chromosome segregation that is assembled on chromosomes is modulated by IP8. Members of the yeast CCAN kinetochore-subcomplex such as Mal2/CENP-O localize to the kinetochore depending on the intracellular IP8-level: higher than wild-type IP8 levels reduce Mal2 kinetochore targeting, while a reduction in IP8 has the opposite effect. As our perturbations of the inositol polyphosphate and IPP pathways demonstrate that kinetochore architecture depends solely on IP8 and not on other IPPs, we conclude that chromosome transmission fidelity is controlled by IP8 via an interplay between entry into mitosis, kinetochore architecture, and spindle dynamics.

Keywords:  Asp1; CCAN; CENP-O; Fta2; IP8; Mal2; PPIP5K; Schizosaccharomyces pombe; cell cycle; centromere; chromosome segregation; fission yeast; inositol pyrophosphates; kinetochore; mitosis

DOI:  https://doi.org/10.3390/jof8090933
J Cell Sci. 2022 Sep 15. pii: jcs259657. [Epub ahead of print]135(18):

Mitotic spindle disassembly in human cells relies on CRIPT having hierarchical redox signals.

Kehan Xu, Chunxue Wang, Kari Keinänen, Hong Li, Chunlin Cai.

  Swift and complete spindle disassembly in late mitosis is essential for cell survival, yet how it happens is largely unknown in mammalian cells. Here we used real-time live cell microscopy and biochemical assays to show that the primordial dwarfism (PD)-related cysteine-rich protein CRIPT dictates the spindle disassembly in a redox-dependent manner in human cells. This previously reported cytoplasmic protein was found to have a confined nuclear localization with a nucleolar concentration during interphase but was distributed to spindles and underwent redox modifications to form disulfide bonds in CXXC pairs during mitosis. Then, it directly interacted with, and might transfer a redox response to, tubulin subunits via a putative redox exchange among cysteine residues to induce microtubule depolymerization. Expression of CRIPT proteins with mutations of these cysteine residues blocked spindle disassembly, generating two cell types with long-lasting metaphase spindles or spindle remnants. Live-cell recordings of a disease-relevant mutant (CRIPTC3Y) revealed that microtubule depolymerization at spindle ends during anaphase and the entire spindle dissolution during telophase might share a common CRIPT-bearing redox-controlled mechanism.

Keywords:  CRIPT; Mitosis; Redox regulation; Spindle; Spindle disassembly

DOI:  https://doi.org/10.1242/jcs.259657
Mol Biol Cell. 2022 Sep 21. mbcE22070269T

Divergent polo boxes in KKT2 bind KKT1 to initiate the kinetochore assembly cascade in Trypanosoma brucei.

Midori Ishii, Patryk Ludzia, Gabriele Marcianò, William Allen, Olga O Nerusheva, Bungo Akiyoshi.

Chromosome segregation requires assembly of the macromolecular kinetochore complex onto centromeric DNA. While most eukaryotes have canonical kinetochore proteins that are widely conserved among eukaryotes, evolutionarily divergent kinetoplastids have a unique set of kinetochore proteins. Little is known about the mechanism of kinetochore assembly in kinetoplastids. Here we characterize two homologous kinetoplastid kinetochore proteins, KKT2 and KKT3, that constitutively localize at centromeres. They have three domains that are highly conserved among kinetoplastids: an N-terminal kinase domain of unknown function, the centromere localization domain in the middle, and the C-terminal domain that has weak similarity to polo boxes of Polo-like kinases. We show that the kinase activity of KKT2 is essential for accurate chromosome segregation, while that of KKT3 is dispensable for cell growth in Trypanosoma brucei. Crystal structures of their divergent polo boxes reveal differences between KKT2 and KKT3. We also show that the divergent polo boxes of KKT3 are sufficient to recruit KKT2 in trypanosomes. Furthermore, we demonstrate that the divergent polo boxes of KKT2 directly interact with KKT1 and that KKT1 interacts with KKT6. These results show that the divergent polo boxes of KKT2 and KKT3 are protein-protein interaction domains, which initiate kinetochore assembly in T. brucei.

DOI: https://doi.org/10.1091/mbc.E22-07-0269-T
Cancer Lett. 2022 Sep 15. pii: S0304-3835(22)00401-3. [Epub ahead of print] 215914

The mitotic regulator RCC2 promotes glucose metabolism through BACH1-dependent transcriptional upregulation of hexokinase II in glioma.

Liu Tian, Yubing Wang, Yiwei Wang, Stanley Kwok-Kuen Cheung, Penelope Mei-Yu Or, Chi-Wai Wong, Jingyu Guan, Zhining Li, Weiqin Yang, Yalin Tu, Jing Wang, Wayne Lut-Heng Ho, Haiwei Gu, Alfred Sze-Lok Cheng, Stephen Kwok-Wing Tsui, Andrew M Chan.

  Weighted gene co-expression network analysis (WGCNA) identified a cell-cycle module that is associated with poor prognosis and aggressiveness of glioma. One of the core members, Regulator of chromatin condensation 2 (RCC2) is a component of the chromosome passenger complex. Accumulating evidence suggests that RCC2 plays a vital role in the mitotic process and that abnormal RCC2 expression is involved in cancer development. Gene silencing experiments show that RCC2 is required for glioma cell proliferation and migration. RNA-Sequencing analysis reveals a dual role of RCC2 in both the cell cycle and metabolism. Specifically, RCC2 regulates G2/M progression via CDC2 phosphorylation at Tyrosine 15. Metabolomic analysis identifies a role for RCC2 in promoting the glycolysis and pentose phosphate pathway. RCC2 exerts effects on metabolism by stabilizing the transcription factor BACH1 at its C-terminus leading to the transcriptional upregulation of hexokinase 2 (HK2). These findings elucidate a novel PTEN/RCC2/BACH1/HK2 signaling axis that drives glioma progression through the dual regulation of mitotic cell cycle and glycolytic events.

Keywords:  BACH1; Glioma; Glycolysis; HK2; RCC2

DOI:  https://doi.org/10.1016/j.canlet.2022.215914