1
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Pena GE, Zhou X, Slevin L, Brownlee C, Heald R. The NLS3 Motif in TPX2 Regulates Spindle Architecture in Xenopus Egg Extracts. Cytoskeleton (Hoboken) 2025. [PMID: 40326229 DOI: 10.1002/cm.22034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2024] [Revised: 04/08/2025] [Accepted: 04/16/2025] [Indexed: 05/07/2025]
Abstract
A bipolar spindle composed of microtubules and many associated proteins functions to segregate chromosomes during cell division in all eukaryotes, yet both spindle size and architecture vary dramatically across different species and cell types. Targeting protein for Xklp2 (TPX2) is one candidate factor for modulating spindle microtubule organization through its roles in branching microtubule nucleation, activation of the mitotic kinase Aurora A, and association with the kinesin-5 (Eg5) motor. Here we characterize a conserved nuclear localization sequence (NLS) motif, 123KKLK126 in Xenopus laevis TPX2, which regulates astral microtubule formation and spindle pole morphology in Xenopus egg extracts. Addition of recombinant TPX2 with this sequence mutated to AALA stimulated spontaneous formation of microtubule asters and increased recruitment of phosphorylated Aurora A, pericentrin, and Eg5 to meiotic spindle poles while still binding to the regulatory transport factor importin α. We propose that TPX2 is a linchpin spindle assembly factor whose regulation contributes to the activation of multiple microtubule polymerizing and organizing proteins, generating distinct spindle architectures.
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Affiliation(s)
- Guadalupe E Pena
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Xiao Zhou
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
- AbbVie, South San Francisco, California, USA
| | - Lauren Slevin
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
- Swedish Maternal and Fetal Specialty Center, Seattle, Washington, USA
| | - Christopher Brownlee
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
- Deparment of Pharmacological Sciences, Stony Brook University, Stony Brook, New York, USA
| | - Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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2
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Liang Z, Huang J, Wang Y, Hua S, Jiang K. Diverse microtubule-binding repeats regulate TPX2 activities at distinct locations within the spindle. J Cell Biol 2025; 224:e202404025. [PMID: 39821262 PMCID: PMC11737348 DOI: 10.1083/jcb.202404025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 11/12/2024] [Accepted: 12/20/2024] [Indexed: 01/19/2025] Open
Abstract
TPX2 is an elongated molecule containing multiple α-helical repeats. It stabilizes microtubules (MTs), promotes MT nucleation, and is essential for spindle assembly. However, the molecular basis of how TPX2 performs these functions remains elusive. Here, we systematically characterized the MT-binding activities of all TPX2 modules individually and in combinations and investigated their respective contributions both in vitro and in cells. We show that TPX2 contains α-helical repeats with opposite preferences for "extended" and "compacted" tubulin dimer spacing, and their distinct combinations produce divergent outcomes, making TPX2 activity highly robust yet tunable. Importantly, a repeat group at the C terminus, R8-9, is the key determinant of the TPX2 function. It stabilizes MTs by promoting rescues in vitro and is critical in spindle assembly. We propose a model where TPX2 activities are spatially regulated via its diverse MT-binding repeats to accommodate its varied functions in distinct locations within the spindle. Furthermore, we reveal a synergy between TPX2 and HURP in stabilizing spindle MTs.
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Affiliation(s)
- Zhuobi Liang
- State Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School and Hospital of Stomatology, Medical Research Institute, Wuhan University, Wuhan, China
- Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Junjie Huang
- State Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School and Hospital of Stomatology, Medical Research Institute, Wuhan University, Wuhan, China
- Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Yong Wang
- State Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School and Hospital of Stomatology, Medical Research Institute, Wuhan University, Wuhan, China
- Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Shasha Hua
- State Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School and Hospital of Stomatology, Medical Research Institute, Wuhan University, Wuhan, China
- Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
| | - Kai Jiang
- State Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School and Hospital of Stomatology, Medical Research Institute, Wuhan University, Wuhan, China
- Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, China
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3
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Prifti DK, Lauzier A, Garand C, Calvo E, Devillers R, Roy S, Dos Santos A, Descombes L, Trudel B, Laplante M, Bordeleau F, Elowe S. ARHGEF17/TEM4 regulates the cell cycle through control of G1 progression. J Cell Biol 2025; 224:e202311194. [PMID: 39903211 PMCID: PMC11792891 DOI: 10.1083/jcb.202311194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Revised: 10/17/2024] [Accepted: 12/10/2024] [Indexed: 02/06/2025] Open
Abstract
The Ras homolog (Rho) small GTPases coordinate diverse cellular functions including cell morphology, adhesion and motility, cell cycle progression, survival, and apoptosis via their role in regulating the actin cytoskeleton. The upstream regulators for many of these functions are unknown. ARHGEF17 (also known as TEM4) is a Rho family guanine nucleotide exchange factor (GEF) implicated in cell migration, cell-cell junction formation, and the mitotic checkpoint. In this study, we characterize the regulation of the cell cycle by TEM4. We demonstrate that TEM4-depleted cells exhibit multiple defects in mitotic entry and duration, spindle morphology, and spindle orientation. In addition, TEM4 insufficiency leads to excessive cortical actin polymerization and cell rounding defects. Mechanistically, we demonstrate that TEM4-depleted cells delay in G1 as a consequence of decreased expression of the proproliferative transcriptional co-activator YAP. TEM4-depleted cells that progress through to mitosis do so with decreased levels of cyclin B as a result of attenuated expression of CCNB1. Importantly, cyclin B overexpression in TEM4-depleted cells largely rescues mitotic progression and chromosome segregation defects in anaphase. Our study thus illustrates the consequences of Rho signaling imbalance on cell cycle progression and identifies TEM4 as the first GEF governing Rho GTPase-mediated regulation of G1/S.
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Affiliation(s)
- Diogjena Katerina Prifti
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
| | - Annie Lauzier
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
| | - Chantal Garand
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
| | - Eva Calvo
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
| | - Romain Devillers
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de pneumologie de Québec (CRIUCPQ), Faculté de Médecine, Université Laval, Québec, Canada
| | - Suparba Roy
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
| | - Alexsandro Dos Santos
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
| | - Laurence Descombes
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Cancer, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
| | - Benjamin Trudel
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Cancer, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
- Centre de Recherche en Organogénèse Expérimentale de l’Université Laval (LOEX), Québec, Canada
| | - Mathieu Laplante
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
- Centre de Recherche de l’Institut Universitaire de Cardiologie et de pneumologie de Québec (CRIUCPQ), Faculté de Médecine, Université Laval, Québec, Canada
| | - François Bordeleau
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Cancer, Québec, Canada
- Département de biologie moléculaire, biochimie médicale et pathologie, Faculté de Médecine, Université Laval, Québec City, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
- Centre de Recherche en Organogénèse Expérimentale de l’Université Laval (LOEX), Québec, Canada
| | - Sabine Elowe
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’Enfant, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’Ingénierie et les Applications des protéines, Québec, Canada
- Département de Pédiatrie, Faculté de Médicine, Université Laval, Québec, Canada
- Centre de Recherche sur le Cancer de l’Université Laval, Québec, Canada
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4
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Perez-Bertoldi JM, Zhao Y, Thawani A, Yildiz A, Nogales E. HURP regulates Kif18A recruitment and activity to synergistically control microtubule dynamics. Nat Commun 2024; 15:9687. [PMID: 39516196 PMCID: PMC11549086 DOI: 10.1038/s41467-024-53691-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Accepted: 10/16/2024] [Indexed: 11/16/2024] Open
Abstract
During mitosis, microtubule dynamics are regulated to ensure proper alignment and segregation of chromosomes. The dynamics of kinetochore-attached microtubules are regulated by hepatoma-upregulated protein (HURP) and the mitotic kinesin-8 Kif18A, but the underlying mechanism remains elusive. Using single-molecule imaging in vitro, we demonstrate that Kif18A motility is regulated by HURP. While sparse decoration of HURP activates the motor, higher concentrations hinder processive motility. To shed light on this behavior, we determine the binding mode of HURP to microtubules using cryo-EM. The structure helps rationalize why HURP functions as a microtubule stabilizer. Additionally, HURP partially overlaps with the microtubule-binding site of the Kif18A motor domain, indicating that excess HURP inhibits Kif18A motility by steric exclusion. We also observe that HURP and Kif18A function together to suppress dynamics of the microtubule plus-end, providing a mechanistic basis for how they collectively serve in microtubule length control.
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Affiliation(s)
| | - Yuanchang Zhao
- Physics Department, University of California, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Akanksha Thawani
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Ahmet Yildiz
- Biophysics Graduate Group, University of California, Berkeley, CA, USA.
- Physics Department, University of California, Berkeley, CA, USA.
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Eva Nogales
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Howard Hughes Medical Institute, University of California, Berkeley, CA, USA.
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5
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Salazar BM, Ohi R. Antiparallel microtubule bundling supports KIF15-driven mitotic spindle assembly. Mol Biol Cell 2024; 35:ar84. [PMID: 38598297 PMCID: PMC11238081 DOI: 10.1091/mbc.e24-01-0023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 04/02/2024] [Accepted: 04/05/2024] [Indexed: 04/12/2024] Open
Abstract
The spindle is a bipolar microtubule-based machine that is crucial for accurate chromosome segregation. Spindle bipolarity is generated by Eg5 (a kinesin-5), a conserved motor that drives spindle assembly by localizing to and sliding apart antiparallel microtubules. In the presence of Eg5 inhibitors (K5Is), KIF15 (a kinesin-12) can promote spindle assembly, resulting in K5I-resistant cells (KIRCs). However, KIF15 is a less potent motor than Eg5, suggesting that other factors may contribute to spindle formation in KIRCs. Protein Regulator of Cytokinesis 1 (PRC1) preferentially bundles antiparallel microtubules, and we previously showed that PRC1 promotes KIF15-microtubule binding, leading us to hypothesize that PRC1 may enhance KIF15 activity in KIRCs. Here, we demonstrate that: 1) loss of PRC1 in KIRCs decreases spindle bipolarity, 2) overexpression of PRC1 increases spindle formation efficiency in KIRCs, 3) overexpression of PRC1 protects K5I naïve cells against the K5I S-trityl-L-cysteine (STLC), and 4) PRC1 overexpression promotes the establishment of K5I resistance. These effects are not fully reproduced by a TPX2, a microtubule bundler with no known preference for microtubule orientation. These results suggest a model wherein PRC1-mediated bundling of microtubules creates a more favorable microtubule architecture for KIF15-driven mitotic spindle assembly in the context of Eg5 inhibition.
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Affiliation(s)
- Brittany M. Salazar
- Department of Cell and Developmental Biology, University of Michigan; Ann Arbor, MI 48109
| | - Ryoma Ohi
- Department of Cell and Developmental Biology, University of Michigan; Ann Arbor, MI 48109
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6
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Perez-Bertoldi JM, Zhao Y, Thawani A, Yildiz A, Nogales E. Molecular interplay between HURP and Kif18A in mitotic spindle regulation. RESEARCH SQUARE 2024:rs.3.rs-4249615. [PMID: 38854046 PMCID: PMC11160874 DOI: 10.21203/rs.3.rs-4249615/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
During mitosis, microtubule dynamics are regulated to ensure proper alignment and segregation of chromosomes. The dynamics of kinetochore-attached microtubules are regulated by hepatoma-upregulated protein (HURP) and the mitotic kinesin-8 Kif18A, but the underlying mechanism remains elusive. Using single-molecule imaging in vitro, we demonstrate that Kif18A motility is regulated by HURP. While sparse decoration of HURP activates the motor, higher concentrations hinder processive motility. To shed light on this behavior, we determined the binding mode of HURP to microtubules using Cryo-EM. The structure reveals that one HURP motif spans laterally across β-tubulin, while a second motif binds between adjacent protofilaments. HURP partially overlaps with the microtubule-binding site of the Kif18A motor domain, indicating that excess HURP inhibits Kif18A motility by steric exclusion. We also observed that HURP and Kif18A function together to suppress dynamics of the microtubule plus-end, providing a mechanistic basis for how they collectively serve in spindle length control.
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Affiliation(s)
| | - Yuanchang Zhao
- Physics Department, University of California, Berkeley, CA, USA
| | - Akanksha Thawani
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Ahmet Yildiz
- Biophysics Graduate Group, University of California, Berkeley, CA, USA
- Physics Department, University of California, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Eva Nogales
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California, Berkeley, CA, USA
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7
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Perez-Bertoldi JM, Zhao Y, Thawani A, Yildiz A, Nogales E. Molecular interplay between HURP and Kif18A in mitotic spindle regulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.11.589088. [PMID: 38645125 PMCID: PMC11030443 DOI: 10.1101/2024.04.11.589088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
During mitosis, microtubule dynamics are regulated to ensure proper alignment and segregation of chromosomes. The dynamics of kinetochore-attached microtubules are regulated by hepatoma-upregulated protein (HURP) and the mitotic kinesin-8 Kif18A, but the underlying mechanism remains elusive. Using single-molecule imaging in vitro , we demonstrate that Kif18A motility is regulated by HURP. While sparse decoration of HURP activates the motor, higher concentrations hinder processive motility. To shed light on this behavior, we determined the binding mode of HURP to microtubules using Cryo-EM. The structure reveals that one HURP motif spans laterally across β-tubulin, while a second motif binds between adjacent protofilaments. HURP partially overlaps with the microtubule-binding site of the Kif18A motor domain, indicating that excess HURP inhibits Kif18A motility by steric exclusion. We also observed that HURP and Kif18A function together to suppress dynamics of the microtubule plus-end, providing a mechanistic basis for how they collectively serve in spindle length control.
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8
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Pena G, Rohrberg J, Goga A, Heald R. Changes in spindle morphology driven by TPX2 overexpression in MYC-driven breast cancer cells. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001182. [PMID: 38660563 PMCID: PMC11040394 DOI: 10.17912/micropub.biology.001182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 04/09/2024] [Accepted: 04/08/2024] [Indexed: 04/26/2024]
Abstract
The MYC oncogene was previously shown to induce mitotic spindle defects, chromosome instability, and reliance on the microtubule-associated protein TPX2 to survive, but how TPX2 levels affect spindle morphology in cancer cells has not previously been examined in detail. We show that breast cancer cell lines expressing high levels of MYC and TPX2 possess shorter spindles with increased TPX2 localization at spindle poles. A similar effect was observed in non-transformed human RPE-1 cells compared to a tumor cell line (HeLa) that overexpresses MYC . These results demonstrate that TPX2 alters spindle length and morphology in cancer cells, which may contribute their ability to divide despite MYC-induced mitotic stress.
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Affiliation(s)
- Guadalupe Pena
- Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, United States
| | - Julia Rohrberg
- Medicine, University of California, San Francisco, San Francisco, California, United States
- Cell & Tissue Biology, University of California, San Francisco, San Francisco, California, United States
| | - Andrei Goga
- Medicine, University of California, San Francisco, San Francisco, California, United States
- Cell & Tissue Biology, University of California, San Francisco, San Francisco, California, United States
| | - Rebecca Heald
- Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, United States
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9
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Gopinathan G, Xu Q, Luan X, Diekwisch TGH. CFDP1 regulates the stability of pericentric heterochromatin thereby affecting RAN GTPase activity and mitotic spindle formation. PLoS Biol 2024; 22:e3002574. [PMID: 38630655 PMCID: PMC11023358 DOI: 10.1371/journal.pbio.3002574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Accepted: 03/02/2024] [Indexed: 04/19/2024] Open
Abstract
The densely packed centromeric heterochromatin at minor and major satellites is comprised of H3K9me2/3 histones, the heterochromatin protein HP1α, and histone variants. In the present study, we sought to determine the mechanisms by which condensed heterochromatin at major and minor satellites stabilized by the chromatin factor CFDP1 affects the activity of the small GTPase Ran as a requirement for spindle formation. CFDP1 colocalized with heterochromatin at major and minor satellites and was essential for the structural stability of centromeric heterochromatin. Loss of CENPA, HP1α, and H2A.Z heterochromatin components resulted in decreased binding of the spindle nucleation facilitator RCC1 to minor and major satellite repeats. Decreased RanGTP levels as a result of diminished RCC1 binding interfered with chromatin-mediated microtubule nucleation at the onset of mitotic spindle formation. Rescuing chromatin H2A.Z levels in cells and mice lacking CFDP1 through knock-down of the histone chaperone ANP32E not only partially restored RCC1-dependent RanGTP levels but also alleviated CFDP1-knockout-related craniofacial defects and increased microtubule nucleation in CFDP1/ANP32E co-silenced cells. Together, these studies provide evidence for a direct link between condensed heterochromatin at major and minor satellites and microtubule nucleation through the chromatin protein CFDP1.
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Affiliation(s)
- Gokul Gopinathan
- School of Medicine and Dentistry, University of Rochester, Rochester, New York, United States of America
| | - Qian Xu
- School of Medicine and Dentistry, University of Rochester, Rochester, New York, United States of America
| | - Xianghong Luan
- School of Medicine and Dentistry, University of Rochester, Rochester, New York, United States of America
| | - Thomas G. H. Diekwisch
- School of Medicine and Dentistry, University of Rochester, Rochester, New York, United States of America
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10
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Pena GE, Zhou X, Slevin L, Brownlee C, Heald R. Identification of a motif in TPX2 that regulates spindle architecture in Xenopus egg extracts. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.10.579770. [PMID: 38370704 PMCID: PMC10871311 DOI: 10.1101/2024.02.10.579770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
A bipolar spindle composed of microtubules and many associated proteins functions to segregate chromosomes during cell division in all eukaryotes, yet spindle size and architecture varies dramatically across different species and cell types. Targeting protein for Xklp2 (TPX2) is one candidate factor for modulating spindle microtubule organization through its roles in branching microtubule nucleation, activation of the mitotic kinase Aurora A, and association with the kinesin-5 (Eg5) motor. Here we identify a conserved nuclear localization sequence (NLS) motif, 123 KKLK 126 in X. laevis TPX2, which regulates astral microtubule formation and spindle pole morphology in Xenopus egg extracts. Addition of recombinant TPX2 with this sequence mutated to AALA dramatically increased spontaneous formation of microtubule asters and recruitment of phosphorylated Aurora A, pericentrin, and Eg5 to meiotic spindle poles. We propose that TPX2 is a linchpin spindle assembly factor whose regulation contributes to the recruitment and activation of multiple microtubule polymerizing and organizing proteins, generating distinct spindle architectures.
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11
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Nayak P, Chatterjee S, Paul R. Microtubule search-and-capture model evaluates the effect of chromosomal volume conservation on spindle assembly during mitosis. Phys Rev E 2023; 108:034401. [PMID: 37849183 DOI: 10.1103/physreve.108.034401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 06/23/2023] [Indexed: 10/19/2023]
Abstract
Variation in the chromosome numbers can arise from the erroneous mitosis or fusion and fission of chromosomes. While the mitotic errors lead to an increase or decrease in the overall chromosomal substance in the daughter cells, fission and fusion keep this conserved. Variations in chromosome numbers are assumed to be a crucial driver of speciation. For example, the members of the muntjac species are known to have very different karyotypes with the chromosome numbers varying from 2n=70+3B in the brown brocket deer to 2n=46 in the Chinese muntjac and 2n=6/7 in the Indian muntjac. The chromosomal content in the nucleus of these closely related mammals is roughly the same and various chromosome fusion and fission pathways have been suggested as the evolution process of these karyotypes. Similar trends can also be found in lepidoptera and yeast species which show a wide variation of chromosome numbers. The effect of chromosome number variation on the spindle assembly time and accuracy is still not properly addressed. We computationally investigate the effect of conservation of the total chromosomal substance on the spindle assembly during prometaphase. Our results suggest that chromosomal fusion pathways aid the microtubule-driven search and capture of the kinetochore in cells with monocentric chromosomes. We further report a comparative analysis of the site and percentage of amphitelic captures, dependence on cell shape, and position of the kinetochore in respect to chromosomal volume partitioning.
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Affiliation(s)
- Pinaki Nayak
- School of Mathematical and Computational Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India
| | - Saptarshi Chatterjee
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30332, USA
| | - Raja Paul
- School of Mathematical and Computational Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India
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12
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Valdez VA, Neahring L, Petry S, Dumont S. Mechanisms underlying spindle assembly and robustness. Nat Rev Mol Cell Biol 2023; 24:523-542. [PMID: 36977834 PMCID: PMC10642710 DOI: 10.1038/s41580-023-00584-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2023] [Indexed: 03/30/2023]
Abstract
The microtubule-based spindle orchestrates chromosome segregation during cell division. Following more than a century of study, many components and pathways contributing to spindle assembly have been described, but how the spindle robustly assembles remains incompletely understood. This process involves the self-organization of a large number of molecular parts - up to hundreds of thousands in vertebrate cells - whose local interactions give rise to a cellular-scale structure with emergent architecture, mechanics and function. In this Review, we discuss key concepts in our understanding of spindle assembly, focusing on recent advances and the new approaches that enabled them. We describe the pathways that generate the microtubule framework of the spindle by driving microtubule nucleation in a spatially controlled fashion and present recent insights regarding the organization of individual microtubules into structural modules. Finally, we discuss the emergent properties of the spindle that enable robust chromosome segregation.
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Affiliation(s)
| | - Lila Neahring
- Department of Bioengineering & Therapeutic Sciences, UCSF, San Francisco, CA, USA
- Developmental & Stem Cell Biology Graduate Program, UCSF, San Francisco, CA, USA
| | - Sabine Petry
- Molecular Biology, Princeton University, Princeton, NJ, USA.
| | - Sophie Dumont
- Department of Bioengineering & Therapeutic Sciences, UCSF, San Francisco, CA, USA.
- Developmental & Stem Cell Biology Graduate Program, UCSF, San Francisco, CA, USA.
- Department of Biochemistry & Biophysics, UCSF, San Francisco, CA, USA.
- Chan Zuckerberg Biohub, San Francisco, CA, USA.
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13
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Amin MA, Chakraborty M, Wallace DA, Varma D. Coordination between the Ndc80 complex and dynein is essential for microtubule plus-end capture by kinetochores during early mitosis. J Biol Chem 2023; 299:104711. [PMID: 37060995 PMCID: PMC10206188 DOI: 10.1016/j.jbc.2023.104711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 03/22/2023] [Accepted: 04/02/2023] [Indexed: 04/17/2023] Open
Abstract
Mitotic kinetochores are initially captured by dynamic microtubules via a "search-and-capture" mechanism. The microtubule motor, dynein, is critical for kinetochore capture as it has been shown to transport microtubule-attached chromosomes toward the spindle pole during prometaphase. The microtubule-binding nuclear division cycle 80 (Ndc80) complex that is recruited to kinetochores in prophase is known to play a central role in forming kinetochore-microtubule (kMT) attachments in metaphase. It is not yet clear, however, how Ndc80 contributes to initial kMT capture during prometaphase. Here, by combining CRISPR/Cas9-mediated knockout and RNAi technology with assays specific to study kMT capture, we show that mitotic cells lacking Ndc80 exhibit substantial defects in this function during prometaphase. Rescue experiments show that Ndc80 mutants deficient in microtubule-binding are unable to execute proper kMT capture. While cells inhibited of dynein alone are predominantly able to make initial kMT attachments, cells co-depleted of Ndc80 and dynein show severe defects in kMT capture. Further, we use an in vitro total internal reflection fluorescence microscopy assay to reconstitute microtubule capture events, which suggest that Ndc80 and dynein coordinate with each other for microtubule plus-end capture and that the phosphorylation status of Ndc80 is critical for productive kMT capture. A novel interaction between Ndc80 and dynein that we identify in prometaphase extracts might be critical for efficient plus-end capture. Thus, our studies, for the first time, identify a distinct event in the formation of initial kMT attachments, which is directly mediated by Ndc80 and in coordination with dynein is required for efficient kMT capture and chromosome alignment.
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Affiliation(s)
- Mohammed Abdullahel Amin
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
| | - Manas Chakraborty
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Destiny Ariel Wallace
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Dileep Varma
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
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14
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Wu J, Larreategui-Aparicio A, Lambers MLA, Bodor DL, Klaasen SJ, Tollenaar E, de Ruijter-Villani M, Kops GJPL. Microtubule nucleation from the fibrous corona by LIC1-pericentrin promotes chromosome congression. Curr Biol 2023; 33:912-925.e6. [PMID: 36720222 PMCID: PMC10017265 DOI: 10.1016/j.cub.2023.01.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 11/17/2022] [Accepted: 01/06/2023] [Indexed: 01/31/2023]
Abstract
Error-free chromosome segregation in mitosis and meiosis relies on the assembly of a microtubule-based spindle that interacts with kinetochores to guide chromosomes to the cell equator before segregation in anaphase. Microtubules sprout from nucleation sites such as centrosomes, but kinetochores can also promote microtubule formation. It is unclear, however, how kinetochore-derived microtubules are generated and what their role is in chromosome segregation. Here, we show that the transient outer-kinetochore meshwork known as the fibrous corona serves as an autonomous microtubule nucleation platform. The fibrous corona is essential for the nucleation of kinetochore-derived microtubules, and when dissociated from the core kinetochore, it retains microtubule nucleation capacity. Nucleation relies on a fibrous-corona-bound pool of the LIC1 subunit of the dynein motor complex, which interacts with the γ-tubulin-tethering protein pericentrin (PCNT). PCNT is essential for microtubule nucleation from fibrous coronas, and in centrosome-depleted cells, where nearly all mitotic nucleation occurs at fibrous coronas, chromosome congression is fully dependent on PCNT. We further show that chromosomes in bovine oocytes, which naturally lack centrosomes, have highly expanded fibrous coronas that drive chromosome-derived microtubule nucleation. Preventing fibrous corona expansion in these cells impairs chromosome congression and causes spindle assembly defects. Our results show that fibrous coronas are autonomous microtubule-organizing centers that are important for spindle assembly, which may be especially relevant in acentrosomal cells such as oocytes.
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Affiliation(s)
- Jingchao Wu
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Uppsalalaan 8, 3584CT Utrecht, the Netherlands; University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands; Oncode Institute, Jaarbeursplein 6, 3521AL Utrecht, the Netherlands
| | - Ainhoa Larreategui-Aparicio
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Uppsalalaan 8, 3584CT Utrecht, the Netherlands; University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands; Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584CL Utrecht, the Netherlands
| | - Maaike L A Lambers
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Uppsalalaan 8, 3584CT Utrecht, the Netherlands; University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands; Oncode Institute, Jaarbeursplein 6, 3521AL Utrecht, the Netherlands
| | - Dani L Bodor
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Uppsalalaan 8, 3584CT Utrecht, the Netherlands; University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands; Oncode Institute, Jaarbeursplein 6, 3521AL Utrecht, the Netherlands
| | - Sjoerd J Klaasen
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Uppsalalaan 8, 3584CT Utrecht, the Netherlands; University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands; Oncode Institute, Jaarbeursplein 6, 3521AL Utrecht, the Netherlands
| | - Eveline Tollenaar
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584CL Utrecht, the Netherlands
| | - Marta de Ruijter-Villani
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Uppsalalaan 8, 3584CT Utrecht, the Netherlands; University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands; Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584CL Utrecht, the Netherlands; Division of Woman and Baby, Department of Obstetrics and Gynecology, University Medical Centre Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands
| | - Geert J P L Kops
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Uppsalalaan 8, 3584CT Utrecht, the Netherlands; University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, the Netherlands; Oncode Institute, Jaarbeursplein 6, 3521AL Utrecht, the Netherlands.
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15
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Renda F, Khodjakov A. Cell biology: Kinetochores nucleate their own microtubules. Curr Biol 2023; 33:R187-R190. [PMID: 36917941 DOI: 10.1016/j.cub.2023.01.049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
The origin of microtubules that tether the chromosomes' kinetochores to spindle poles has remained a mystery for several decades. A new study identifies the 'fibrous corona' as an autonomous microtubule nucleation site, and reveals the molecular cascade responsible for this process.
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Affiliation(s)
- Fioranna Renda
- Wadsworth Center, New York State Department of Health, Albany, NY, USA.
| | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, NY, USA.
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16
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Berman AY, Wieczorek M, Aher A, Olinares PDB, Chait BT, Kapoor TM. A nucleotide binding-independent role for γ-tubulin in microtubule capping and cell division. J Cell Biol 2023; 222:213828. [PMID: 36695784 PMCID: PMC9930161 DOI: 10.1083/jcb.202204102] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 10/20/2022] [Accepted: 12/22/2022] [Indexed: 01/26/2023] Open
Abstract
The γ-tubulin ring complex (γ-TuRC) has essential roles in centrosomal and non-centrosomal microtubule organization during vertebrate mitosis. While there have been important advances in understanding γ-TuRC-dependent microtubule nucleation, γ-TuRC capping of microtubule minus-ends remains poorly characterized. Here, we utilized biochemical reconstitutions and cellular assays to characterize the human γ-TuRC's capping activity. Single filament assays showed that the γ-TuRC remained associated with a nucleated microtubule for tens of minutes. In contrast, caps at dynamic microtubule minus-ends displayed lifetimes of ∼1 min. Reconstituted γ-TuRCs with nucleotide-binding deficient γ-tubulin (γ-tubulinΔGTP) formed ring-shaped complexes that did not nucleate microtubules but capped microtubule minus-ends with lifetimes similar to those measured for wild-type complexes. In dividing cells, microtubule regrowth assays revealed that while knockdown of γ-tubulin suppressed non-centrosomal microtubule formation, add-back of γ-tubulinΔGTP could substantially restore this process. Our results suggest that γ-TuRC capping is a nucleotide-binding-independent activity that plays a role in non-centrosomal microtubule organization during cell division.
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Affiliation(s)
- Adi Y. Berman
- https://ror.org/0420db125Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA,Tri-Institutional PhD Program in Chemical Biology, The Rockefeller University, New York, NY, USA
| | - Michal Wieczorek
- https://ror.org/0420db125Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA
| | - Amol Aher
- https://ror.org/0420db125Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA
| | - Paul Dominic B. Olinares
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, NY, USA
| | - Brian T. Chait
- Tri-Institutional PhD Program in Chemical Biology, The Rockefeller University, New York, NY, USA,Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, NY, USA
| | - Tarun M. Kapoor
- https://ror.org/0420db125Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA,Tri-Institutional PhD Program in Chemical Biology, The Rockefeller University, New York, NY, USA
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17
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Štimac V, Koprivec I, Manenica M, Simunić J, Tolić IM. Augmin prevents merotelic attachments by promoting proper arrangement of bridging and kinetochore fibers. eLife 2022; 11:e83287. [PMID: 36269126 PMCID: PMC9640188 DOI: 10.7554/elife.83287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 09/26/2022] [Indexed: 11/18/2022] Open
Abstract
The human mitotic spindle is made of microtubules nucleated at centrosomes, at kinetochores, and from pre-existing microtubules by the augmin complex. However, it is unknown how the augmin-mediated nucleation affects distinct microtubule classes and thereby mitotic fidelity. Here, we use superresolution microscopy to analyze the previously indistinguishable microtubule arrangements within the crowded metaphase plate area and demonstrate that augmin is vital for the formation of uniformly arranged parallel units consisting of sister kinetochore fibers connected by a bridging fiber. This ordered geometry helps both prevent and resolve merotelic attachments. Whereas augmin-nucleated bridging fibers prevent merotelic attachments by creating a nearly parallel and highly bundled microtubule arrangement unfavorable for creating additional attachments, augmin-nucleated k-fibers produce robust force required to resolve errors during anaphase. STED microscopy revealed that bridging fibers were impaired twice as much as k-fibers following augmin depletion. The complete absence of bridging fibers from a significant portion of kinetochore pairs, especially in the inner part of the spindle, resulted in the specific reduction of the interkinetochore distance. Taken together, we propose a model where augmin promotes mitotic fidelity by generating assemblies consisting of bridging and kinetochore fibers that align sister kinetochores to face opposite poles, thereby preventing erroneous attachments.
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Affiliation(s)
- Valentina Štimac
- Division of Molecular Biology, Ruđer Bošković InstituteZagrebCroatia
| | - Isabella Koprivec
- Division of Molecular Biology, Ruđer Bošković InstituteZagrebCroatia
| | - Martina Manenica
- Division of Molecular Biology, Ruđer Bošković InstituteZagrebCroatia
| | - Juraj Simunić
- Division of Molecular Biology, Ruđer Bošković InstituteZagrebCroatia
| | - Iva M Tolić
- Division of Molecular Biology, Ruđer Bošković InstituteZagrebCroatia
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18
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Popova JV, Pavlova GA, Razuvaeva AV, Yarinich LA, Andreyeva EN, Anders AF, Galimova YA, Renda F, Somma MP, Pindyurin AV, Gatti M. Genetic Control of Kinetochore-Driven Microtubule Growth in Drosophila Mitosis. Cells 2022; 11:cells11142127. [PMID: 35883570 PMCID: PMC9323100 DOI: 10.3390/cells11142127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/28/2022] [Accepted: 06/29/2022] [Indexed: 01/08/2023] Open
Abstract
Centrosome-containing cells assemble their spindles exploiting three main classes of microtubules (MTs): MTs nucleated by the centrosomes, MTs generated near the chromosomes/kinetochores, and MTs nucleated within the spindle by the augmin-dependent pathway. Mammalian and Drosophila cells lacking the centrosomes generate MTs at kinetochores and eventually form functional bipolar spindles. However, the mechanisms underlying kinetochore-driven MT formation are poorly understood. One of the ways to elucidate these mechanisms is the analysis of spindle reassembly following MT depolymerization. Here, we used an RNA interference (RNAi)-based reverse genetics approach to dissect the process of kinetochore-driven MT regrowth (KDMTR) after colcemid-induced MT depolymerization. This MT depolymerization procedure allows a clear assessment of KDMTR, as colcemid disrupts centrosome-driven MT regrowth but not KDMTR. We examined KDMTR in normal Drosophila S2 cells and in S2 cells subjected to RNAi against conserved genes involved in mitotic spindle assembly: mast/orbit/chb (CLASP1), mei-38 (TPX2), mars (HURP), dgt6 (HAUS6), Eb1 (MAPRE1/EB1), Patronin (CAMSAP2), asp (ASPM), and Klp10A (KIF2A). RNAi-mediated depletion of Mast/Orbit, Mei-38, Mars, Dgt6, and Eb1 caused a significant delay in KDMTR, while loss of Patronin had a milder negative effect on this process. In contrast, Asp or Klp10A deficiency increased the rate of KDMTR. These results coupled with the analysis of GFP-tagged proteins (Mast/Orbit, Mei-38, Mars, Eb1, Patronin, and Asp) localization during KDMTR suggested a model for kinetochore-dependent spindle reassembly. We propose that kinetochores capture the plus ends of MTs nucleated in their vicinity and that these MTs elongate at kinetochores through the action of Mast/Orbit. The Asp protein binds the MT minus ends since the beginning of KDMTR, preventing excessive and disorganized MT regrowth. Mei-38, Mars, Dgt6, Eb1, and Patronin positively regulate polymerization, bundling, and stabilization of regrowing MTs until a bipolar spindle is reformed.
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Affiliation(s)
- Julia V. Popova
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
- Laboratory of Bioengineering, Novosibirsk State Agrarian University, 630039 Novosibirsk, Russia
| | - Gera A. Pavlova
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Alyona V. Razuvaeva
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia
| | - Lyubov A. Yarinich
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
- Faculty of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Evgeniya N. Andreyeva
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
| | - Alina F. Anders
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
| | - Yuliya A. Galimova
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
| | - Fioranna Renda
- Institute of Molecular Biology and Pathology (IBPM), National Research Council (CNR), c/o Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy; (F.R.); (M.P.S.)
| | - Maria Patrizia Somma
- Institute of Molecular Biology and Pathology (IBPM), National Research Council (CNR), c/o Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy; (F.R.); (M.P.S.)
| | - Alexey V. Pindyurin
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
- Correspondence: (A.V.P.); (M.G.)
| | - Maurizio Gatti
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia; (J.V.P.); (G.A.P.); (A.V.R.); (L.A.Y.); (E.N.A.); (A.F.A.); (Y.A.G.)
- Institute of Molecular Biology and Pathology (IBPM), National Research Council (CNR), c/o Department of Biology and Biotechnology, Sapienza University of Rome, 00185 Rome, Italy; (F.R.); (M.P.S.)
- Correspondence: (A.V.P.); (M.G.)
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19
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Prifti DK, Lauzier A, Elowe S. A commercial ARHGEF17/TEM4 antibody cross-reacts with Nuclear Mitotic Apparatus protein 1 (NuMA). PLoS One 2022; 17:e0268848. [PMID: 35776709 PMCID: PMC9249204 DOI: 10.1371/journal.pone.0268848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 05/20/2022] [Indexed: 11/18/2022] Open
Abstract
The Rho family Guanine nucleotide exchange factor (GEF) ARHGEF17 (also known as TEM4) is a large protein with only 3 annotated regions: an N-terminal actin-binding domain, a Rho-specific dbl homology (DH)- pleckstrin homology (PH) type GEF domain and a seven bladed β propeller fold at the C-terminus with unknown function. TEM4 has been implicated in numerous activities that rely on regulation of the cytoskeleton including cell migration, cell-cell junction formation and the spindle assembly checkpoint during mitosis. Here we have assessed the specificity of a TEM4 polyclonal antibody that has been commonly used as a Western blotting and immunocytochemistry probe for TEM4 in mammalian cells. We find that this antibody, in addition to its intended target, cross-reacts with the Nuclear Mitotic Apparatus Protein 1 (NuMA) in Western blotting and immunoprecipitation, and detects NuMA preferentially in immunocytochemistry. This cross-reactivity, with an abundant chromatin- and mitotic spindle-associated factor, is likely to affect the interpretation of experiments that make use of this antibody probe, in particular by immunocytochemistry and immunoprecipitation.
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Affiliation(s)
- Diogjena Katerina Prifti
- Programme en Biologie Cellulaire et Moléculaire, Faculté de Médicine Université Laval, Québec, Québec, Canada
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’enfant, Québec, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’ingénierie et les Applications des Protéines, Québec, Québec, Canada
| | - Annie Lauzier
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’enfant, Québec, Québec, Canada
| | - Sabine Elowe
- Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Université Laval, Axe de Réproduction, Santé de la Mère et de l’enfant, Québec, Québec, Canada
- PROTEO-Regroupement Québécois de Recherche sur la Fonction, l’ingénierie et les Applications des Protéines, Québec, Québec, Canada
- Département de Pédiatrie, Faculté de Médicine, Université Laval et le Centre de Recherche sur le Cancer de l’Université Laval, Québec, Québec, Canada
- * E-mail:
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20
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Almeida AC, Soares-de-Oliveira J, Drpic D, Cheeseman LP, Damas J, Lewin HA, Larkin DM, Aguiar P, Pereira AJ, Maiato H. Augmin-dependent microtubule self-organization drives kinetochore fiber maturation in mammals. Cell Rep 2022; 39:110610. [PMID: 35385739 PMCID: PMC8994134 DOI: 10.1016/j.celrep.2022.110610] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 01/07/2022] [Accepted: 03/11/2022] [Indexed: 11/29/2022] Open
Abstract
Chromosome segregation in mammals relies on the maturation of a thick bundle of kinetochore-attached microtubules known as k-fiber. How k-fibers mature from initial kinetochore microtubule attachments remains a fundamental question. By combining molecular perturbations and phenotypic analyses in Indian muntjac fibroblasts containing the lowest known diploid chromosome number in mammals (2N = 6) and distinctively large kinetochores, with fixed/live-cell super-resolution coherent-hybrid stimulated emission depletion (CH-STED) nanoscopy and laser microsurgery, we demonstrate a key role for augmin in kinetochore microtubule self-organization and maturation, regardless of pioneer centrosomal microtubules. In doing so, augmin promotes kinetochore and interpolar microtubule turnover and poleward flux. Tracking of microtubule growth events within individual k-fibers reveals a wide angular dispersion, consistent with augmin-mediated branched microtubule nucleation. Augmin depletion reduces the frequency of kinetochore microtubule growth events and hampers efficient repair after acute k-fiber injury by laser microsurgery. Together, these findings underscore the contribution of augmin-mediated microtubule amplification for k-fiber self-organization and maturation in mammals.
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Affiliation(s)
- Ana C Almeida
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Joana Soares-de-Oliveira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Danica Drpic
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Liam P Cheeseman
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Joana Damas
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK; Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Harris A Lewin
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Denis M Larkin
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK
| | - Paulo Aguiar
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto Nacional de Engenharia Biomédica (INEB), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - António J Pereira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Helder Maiato
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Cell Division Group, Department of Biomedicine, Faculdade de Medicina, Universidade do Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal.
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21
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TPX2 Serves as a Cancer Susceptibility Gene and Is Closely Associated with the Poor Prognosis of Endometrial Cancer. Genet Res (Camb) 2022; 2022:5401106. [PMID: 35356748 PMCID: PMC8942693 DOI: 10.1155/2022/5401106] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 02/10/2022] [Indexed: 11/17/2022] Open
Abstract
Background. Endometrial cancer (EC) is a common tumor of the genital tract that affects the female reproductive system but with only limited treatment options. We aimed to discover new prognostic biomarkers for EC. Methods. We used mRNA-seq data to detect differentially expressed genes (DEGs) between EC and control tissues. Detailed clinicopathological information was collected, and changes in the mRNA and protein levels of hub DEGs were analyzed in EC. Copy number variation (CNV) was also evaluated for its association with the pathogenesis of EC. Gene set enrichment analysis (GSEA) was conducted to enrich significant pathways driven by the hub genes. Cox regression analysis was used to select variables to create a nomogram. The nomogram was calibrated by applying the concordance index (C-index), and net benefits of the nomogram at different threshold probabilities were quantified using decision curve analysis (DCA). Results. Differential expression analysis identified 24 DEGs as potential risk factors for EC. Survival analysis revealed that TPX2 expression was related to worsening overall survival in patients with advanced EC. A high CNV was associated with the overexpression of TPX2; this suggested that modifications in the cell-cycle pathway might be crucial in the advancement of EC. Moreover, an individualized nomogram was developed for TPX2 incorporating clinical factors; this was also evaluated for its ability to predict EC. Calibration and DCA analyses confirmed the robustness and clinical usefulness of the nomogram. Conclusion. We offer novel insights into the pathogenesis and molecular mechanisms of EC. The overexpression of TPX2 was related to a poorer prognosis and could serve as a biomarker for predicting prognostic outcomes in EC patients.
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22
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Renda F, Miles C, Tikhonenko I, Fisher R, Carlini L, Kapoor TM, Mogilner A, Khodjakov A. Non-centrosomal microtubules at kinetochores promote rapid chromosome biorientation during mitosis in human cells. Curr Biol 2022; 32:1049-1063.e4. [PMID: 35108523 PMCID: PMC8930511 DOI: 10.1016/j.cub.2022.01.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 11/23/2021] [Accepted: 01/06/2022] [Indexed: 12/18/2022]
Abstract
Proper segregation of chromosomes during mitosis depends on "amphitelic attachments"-load-bearing connections of sister kinetochores to the opposite spindle poles via bundles of microtubules, termed as the "K-fibers." Current models of spindle assembly assume that K-fibers arise largely from stochastic capture of microtubules, which occurs at random times and locations and independently at sister kinetochores. We test this assumption by following the movements of all kinetochores in human cells and determine that most amphitelic attachments form synchronously at a specific stage of spindle assembly and within a spatially distinct domain. This biorientation domain is enriched in bundles of antiparallel microtubules, and perturbation of microtubule bundling changes the temporal and spatial dynamics of amphitelic attachment formation. Structural analyses indicate that interactions of kinetochores with microtubule bundles are mediated by non-centrosomal short microtubules that emanate from most kinetochores during early prometaphase. Computational analyses suggest that momentous molecular motor-driven interactions with antiparallel bundles rapidly convert these short microtubules into nascent K-fibers. Thus, load-bearing connections to the opposite spindle poles form simultaneously on sister kinetochores. In contrast to the uncoordinated sequential attachments of sister kinetochores expected in stochastic models of spindle assembly, our model envisions the formation of amphitelic attachments as a deterministic process in which the chromosomes connect with the spindle poles synchronously at a specific stage of spindle assembly and at a defined location determined by the spindle architecture. Experimental analyses of changes in the kinetochore behavior in cells with perturbed activity of molecular motors CenpE and dynein confirm the predictive power of the model.
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Affiliation(s)
- Fioranna Renda
- Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Christopher Miles
- Courant Institute and Department of Biology, New York University, New York, NY, USA; Department of Mathematics and the NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, Irvine, CA, USA
| | - Irina Tikhonenko
- Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Rebecca Fisher
- Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Lina Carlini
- Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, NY, USA
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, NY, USA
| | - Alex Mogilner
- Courant Institute and Department of Biology, New York University, New York, NY, USA.
| | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, NY, USA; Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, USA.
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23
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Verma V, Maresca TJ. A celebration of the 25th anniversary of chromatin-mediated spindle assembly. Mol Biol Cell 2022; 33:rt1. [PMID: 35076260 PMCID: PMC9236140 DOI: 10.1091/mbc.e21-08-0400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Formation of a bipolar spindle is required for the faithful segregation of chromosomes during cell division. Twenty-five years ago, a transformative insight into how bipolarity is achieved was provided by Rebecca Heald, Eric Karsenti, and colleagues in their landmark publication characterizing a chromatin-mediated spindle assembly pathway in which centrosomes and kinetochores were dispensable. The discovery revealed that bipolar spindle assembly is a self-organizing process where microtubules, which possess an intrinsic polarity, polymerize around chromatin and become sorted by mitotic motors into a bipolar structure. On the 25th anniversary of this seminal paper, we discuss what was known before, what we have learned since, and what may lie ahead in understanding the bipolar spindle.
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Affiliation(s)
- Vikash Verma
- Biology Department, University of Massachusetts, Amherst, Amherst, MA 01003
| | - Thomas J Maresca
- Biology Department, University of Massachusetts, Amherst, Amherst, MA 01003.,Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Amherst, MA 01003
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24
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Tsuchiya K, Goshima G. Microtubule-associated proteins promote microtubule generation in the absence of γ-tubulin in human colon cancer cells. J Cell Biol 2021; 220:e202104114. [PMID: 34779859 PMCID: PMC8598081 DOI: 10.1083/jcb.202104114] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 08/13/2021] [Accepted: 09/20/2021] [Indexed: 11/29/2022] Open
Abstract
The γ-tubulin complex acts as the predominant microtubule (MT) nucleator that initiates MT formation and is therefore an essential factor for cell proliferation. Nonetheless, cellular MTs are formed after experimental depletion of the γ-tubulin complex, suggesting that cells possess other factors that drive MT nucleation. Here, by combining gene knockout, auxin-inducible degron, RNA interference, MT depolymerization/regrowth assay, and live microscopy, we identified four microtubule-associated proteins (MAPs), ch-TOG, CLASP1, CAMSAPs, and TPX2, which are involved in γ-tubulin-independent MT generation in human colon cancer cells. In the mitotic MT regrowth assay, nucleated MTs organized noncentriolar MT organizing centers (ncMTOCs) in the absence of γ-tubulin. Depletion of CLASP1 or TPX2 substantially delayed ncMTOC formation, suggesting that these proteins might promote MT nucleation in the absence of γ-tubulin. In contrast, depletion of ch-TOG or CAMSAPs did not affect the timing of ncMTOC appearance. CLASP1 also accelerates γ-tubulin-independent MT regrowth during interphase. Thus, MT generation can be promoted by MAPs without the γ-tubulin template.
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Affiliation(s)
- Kenta Tsuchiya
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Gohta Goshima
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
- Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, Nagoya, Japan
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25
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Various effects of two types of kinesin-5 inhibitors on mitosis and cell proliferation. Biochem Pharmacol 2021; 193:114789. [PMID: 34582773 DOI: 10.1016/j.bcp.2021.114789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 09/23/2021] [Accepted: 09/23/2021] [Indexed: 11/21/2022]
Abstract
Kinesin-5 has received considerable attention as a new target for mitosis. Various small-molecule compounds targeting kinesin-5 have been developed in the last few decades. However, the differences in the cellular effects of kinesin-5 inhibitors remain poorly understood. Here, we used two different kinesin-5 inhibitors, biphenyl-type PVZB1194 and S-trityl-L-cysteine-type PVEI0021, to examine their effects on molecular events involving kinesin-5. Our biochemical study of kinesin-5 protein-protein interactions showed that PVZB1194-treated kinesin-5 interacted with TPX2 microtubule nucleation factor, Aurora-A kinase, receptor for hyaluronan-mediated motility, and γ-tubulin, as did untreated mitotic kinesin-5. However, PVEI0021 prevented kinesin-5 from binding to these proteins. In mitotic HeLa cells recovered from nocodazole inhibition, kinesin-5 colocalized with these binding proteins, along with microtubules nucleated near kinetochores. By acting on kinesin-5 interactions with chromatin-associated microtubules, PVZB1194, rather than PVEI0021, not only affected the formation of dispersed microtubule clusters but also enhanced the stability of microtubules. In addition, screening for mitotic inhibitors working synergistically with the kinesin-5 inhibitors revealed that paclitaxel synergistically inhibited HeLa cell proliferation only with PVZB1194. In contrast, the Aurora-A inhibitor MLN8237 exerted a synergistic anti-cell proliferation effect when combined with either inhibitor. Together, these results have provided a better understanding of the molecular action of kinesin-5 inhibitors and indicate their usefulness as molecular tools for the study of mitosis and the development of anticancer agents.
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26
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Ferreira LT, Maiato H. Prometaphase. Semin Cell Dev Biol 2021; 117:52-61. [PMID: 34127384 DOI: 10.1016/j.semcdb.2021.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 11/28/2022]
Abstract
The establishment of a metaphase plate in which all chromosomes are attached to mitotic spindle microtubules and aligned at the cell equator is required for faithful chromosome segregation in metazoans. The achievement of this configuration relies on the precise coordination between several concurrent mechanisms that start upon nuclear envelope breakdown, mediate chromosome capture at their kinetochores during mitotic spindle assembly and culminate with the congression of all chromosomes to the spindle equator. This period is called 'prometaphase'. Because the nature of chromosome capture by mitotic spindle microtubules is error prone, the cell is provided of error correction mechanisms that sense and correct most erroneous kinetochore-microtubule attachments before committing to separate sister chromatids in anaphase. In this review, aimed for newcomers in the field, more than providing an exhaustive mechanistic coverage of each and every concurrent mechanism taking place during prometaphase, we provide an integrative overview of these processes that ultimately promote the subsequent faithful segregation of chromosomes during mitosis.
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Affiliation(s)
- Luísa T Ferreira
- Chromosome Instability & Dynamics Group, i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Helder Maiato
- Chromosome Instability & Dynamics Group, i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Cell Division Group, Experimental Biology Unit, Department of Biomedicine, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal.
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27
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Renda F, Khodjakov A. Role of spatial patterns and kinetochore architecture in spindle morphogenesis. Semin Cell Dev Biol 2021; 117:75-85. [PMID: 33836948 PMCID: PMC8762378 DOI: 10.1016/j.semcdb.2021.03.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/25/2021] [Accepted: 03/25/2021] [Indexed: 12/30/2022]
Abstract
Mitotic spindle is a self-assembling macromolecular machine responsible for the faithful segregation of chromosomes during cell division. Assembly of the spindle is believed to be governed by the 'Search & Capture' (S&C) principle in which dynamic microtubules explore space in search of kinetochores while the latter capture microtubules and thus connect chromosomes to the spindle. Due to the stochastic nature of the encounters between kinetochores and microtubules, the time required for incorporating all chromosomes into the spindle is profoundly affected by geometric constraints, such as the size and shape of kinetochores as well as their distribution in space at the onset of spindle assembly. In recent years, several molecular mechanisms that control these parameters have been discovered. It is now clear that stochastic S&C takes place in structured space, where components are optimally distributed and oriented to minimize steric hindrances. Nucleation of numerous non-centrosomal microtubules near kinetochores accelerates capture, while changes in the kinetochore architecture at various stages of spindle assembly promote proper connection of sister kinetochores to the opposite spindle poles. Here we discuss how the concerted action of multiple facilitating mechanisms ensure that the spindle assembles rapidly yet with a minimal number of errors.
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Affiliation(s)
- Fioranna Renda
- Biggs Laboratory, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12237, United States.
| | - Alexey Khodjakov
- Biggs Laboratory, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12237, United States; Rensselaer Polytechnic Institute, Troy, NY 12180, United States.
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28
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Zupa E, Liu P, Würtz M, Schiebel E, Pfeffer S. The structure of the γ-TuRC: a 25-years-old molecular puzzle. Curr Opin Struct Biol 2020; 66:15-21. [PMID: 33002806 DOI: 10.1016/j.sbi.2020.08.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 08/26/2020] [Accepted: 08/28/2020] [Indexed: 10/23/2022]
Abstract
The nucleation of microtubules from αβ-tubulin dimers is an essential cellular process dependent on γ-tubulin complexes. Mechanistic understanding of the nucleation reaction was hampered by the lack of γ-tubulin complex structures at sufficiently high resolution. The recent technical developments in cryo-electron microscopy have allowed resolving the vertebrate γ-tubulin ring complex (γ-TuRC) structure at near-atomic resolution. These studies clarified the arrangement and stoichiometry of gamma-tubulin complex proteins in the γ-TuRC, characterized the surprisingly versatile integration of the small proteins MZT1/2 into the complex, and identified actin as an integral component of the γ-TuRC. In this review, we summarize the structural insights into the molecular architecture, the assembly pathway, and the regulation of the microtubule nucleation reaction.
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Affiliation(s)
- Erik Zupa
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Peng Liu
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Martin Würtz
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
| | - Stefan Pfeffer
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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29
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Turn RE, East MP, Prekeris R, Kahn RA. The ARF GAP ELMOD2 acts with different GTPases to regulate centrosomal microtubule nucleation and cytokinesis. Mol Biol Cell 2020; 31:2070-2091. [PMID: 32614697 PMCID: PMC7543072 DOI: 10.1091/mbc.e20-01-0012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
ELMOD2 is a ∼32 kDa protein first purified by its GTPase-activating protein (GAP) activity toward ARL2 and later shown to have uniquely broad specificity toward ARF family GTPases in in vitro assays. To begin the task of defining its functions in cells, we deleted ELMOD2 in immortalized mouse embryonic fibroblasts and discovered a number of cellular defects, which are reversed upon expression of ELMOD2-myc. We show that these defects, resulting from the loss of ELMOD2, are linked to two different pathways and two different GTPases: with ARL2 and TBCD to support microtubule nucleation from centrosomes and with ARF6 in cytokinesis. These data highlight key aspects of signaling by ARF family GAPs that contribute to previously underappreciated sources of complexity, including GAPs acting from multiple sites in cells, working with multiple GTPases, and contributing to the spatial and temporal control of regulatory GTPases by serving as both GAPs and effectors.
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Affiliation(s)
- Rachel E Turn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322.,Biochemistry, Cell & Developmental Biology Graduate Program, Laney Graduate School, Emory University, Atlanta, GA 30307
| | - Michael P East
- Department of Pharmacology, University of North Carolina Chapel Hill, Chapel Hill, NC 27599
| | - Rytis Prekeris
- Department of Cell and Developmental Biology, University of Colorado, Aurora, CO 80045
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322
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30
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Marthiens V, Basto R. Centrosomes: The good and the bad for brain development. Biol Cell 2020; 112:153-172. [PMID: 32170757 DOI: 10.1111/boc.201900090] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 02/25/2020] [Accepted: 03/01/2020] [Indexed: 12/15/2022]
Abstract
Centrosomes nucleate and organise the microtubule cytoskeleton in animal cells. These membraneless organelles are key structures for tissue organisation, polarity and growth. Centrosome dysfunction, defined as deviation in centrosome numbers and/or structural integrity, has major impact on brain size and functionality, as compared with other tissues of the organism. In this review, we discuss the contribution of centrosomes to brain growth during development. We discuss in particular the impact of centrosome dysfunction in Drosophila and mammalian neural stem cell division and fitness, which ultimately underlie brain growth defects.
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Affiliation(s)
- Véronique Marthiens
- Biology of Centrosomes and Genetic Instability Laboratory, Institut Curie, PSL Research University, CNRS, UMR144, Paris, 75005, France
| | - Renata Basto
- Biology of Centrosomes and Genetic Instability Laboratory, Institut Curie, PSL Research University, CNRS, UMR144, Paris, 75005, France
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31
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King MR, Petry S. Phase separation of TPX2 enhances and spatially coordinates microtubule nucleation. Nat Commun 2020; 11:270. [PMID: 31937751 PMCID: PMC6959270 DOI: 10.1038/s41467-019-14087-0] [Citation(s) in RCA: 143] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 12/10/2019] [Indexed: 12/14/2022] Open
Abstract
Phase separation of substrates and effectors is proposed to enhance biological reaction rates and efficiency. Targeting protein for Xklp2 (TPX2) is an effector of branching microtubule nucleation in spindles and functions with the substrate tubulin by an unknown mechanism. Here we show that TPX2 phase separates into a co-condensate with tubulin, which mediates microtubule nucleation in vitro and in isolated cytosol. TPX2-tubulin co-condensation preferentially occurs on pre-existing microtubules, the site of branching microtubule nucleation, at the endogenous and physiologically relevant concentration of TPX2. Truncation and chimera versions of TPX2 suggest that TPX2-tubulin co-condensation enhances the efficiency of TPX2-mediated branching microtubule nucleation. Finally, the known inhibitor of TPX2, the importin-α/β heterodimer, regulates TPX2 condensation in vitro and, consequently, branching microtubule nucleation activity in isolated cytosol. Our study demonstrates how regulated phase separation can simultaneously enhance reaction efficiency and spatially coordinate microtubule nucleation, which may facilitate rapid and accurate spindle formation.
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Affiliation(s)
- Matthew R King
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, 08544, USA
- Department of Biomedical Engineering, Washington University, Brauer Hall, One Brookings Drive, Saint Louis, Missouri, 63130, USA
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, 08544, USA.
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32
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Sawada JI, Ishii H, Matsuno K, Sato M, Suzuki Y, Asai A. Selective Inhibition of Spindle Microtubules by a Tubulin-Binding Quinazoline Derivative. Mol Pharmacol 2019; 96:609-618. [PMID: 31471455 DOI: 10.1124/mol.119.116624] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 08/20/2019] [Indexed: 02/03/2023] Open
Abstract
In the research field of tubulin-binding agents for the development of anticancer agents, hidden targets are emerging as a problem in understanding the exact mechanisms of actions. The quinazoline derivative 1-(4-methoxyphenyl)-1-(quinazolin-4-yl)ethan-1-ol (PVHD121) has anti-cell proliferative activity and inhibits tubulin polymerization by binding to the colchicine site of tubulin. However, the molecular mechanism of action of PVHD121 in cells remains unclear. Here, we demonstrate that PVHD121 delays mitotic entry and efficiently causes mitotic arrest with spindle checkpoint activation, leading to subsequent cell death. The dominant phenotype induced by PVHD121 was aberrant spindles with robust microtubules and unseparated centrosomes. The microtubules were radially distributed, and their ends appeared to adhere to kinetochores, and not to centrosomes. Extensive inhibition by high concentrations of PVHD121 eliminated all microtubules from cells. PVHD277 [1-(4-methoxyphenyl)-1-(2-morpholinoquinazolin-4-yl)ethan-1-ol], a PVHD121 derivative with fluorescence, tended to localize close to the centrosomes when cells prepared to enter mitosis. Our results show that PVHD121 is an antimitotic agent that selectively disturbs microtubule formation at centrosomes during mitosis. This antimitotic activity can be attributed to the targeting of centrosome maturation in addition to the interference with microtubule dynamics. Due to its unique bioactivity, PVHD121 is a potential tool for studying the molecular biology of mitosis and a potential lead compound for the development of anticancer agents. SIGNIFICANCE STATEMENT: Many tubulin-binding agents have been developed as potential anticancer agents. The aim of this study was to understand the subcellular molecular actions of a quinazoline derivative tubulin-binding agent, 1-(4-methoxyphenyl)-1-(quinazolin-4-yl)ethan-1-ol (PVHD121). As expected from its binding activity to tubulin, PVHD121 caused aberrant spindles and inhibited mitotic progression. However, in addition to tubulin, PVHD121 also targeted an unexpected biomolecule involved in centrosome maturation. Due to targeting the biomolecule just before entering mitosis, PVHD121 preferentially inhibited centrosome-derived microtubules rather than chromosome-derived microtubules during spindle formation. This study not only revealed the molecular action of PVHD121 in cells but also emphasized the importance of considering possible tubulin-independent effects of tubulin-binding agents via hidden targeted biomolecules for future use.
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Affiliation(s)
- Jun-Ichi Sawada
- Center for Drug Discovery, Graduate School of Pharmaceutical Sciences (J.-i.S., H.I., K.M., A.A.) and Laboratory of Organic Chemistry, School of Pharmaceutical Sciences (M.S., Y.S.), University of Shizuoka, Shizuoka, Japan
| | - Hirosuke Ishii
- Center for Drug Discovery, Graduate School of Pharmaceutical Sciences (J.-i.S., H.I., K.M., A.A.) and Laboratory of Organic Chemistry, School of Pharmaceutical Sciences (M.S., Y.S.), University of Shizuoka, Shizuoka, Japan
| | - Kenji Matsuno
- Center for Drug Discovery, Graduate School of Pharmaceutical Sciences (J.-i.S., H.I., K.M., A.A.) and Laboratory of Organic Chemistry, School of Pharmaceutical Sciences (M.S., Y.S.), University of Shizuoka, Shizuoka, Japan
| | - Masayuki Sato
- Center for Drug Discovery, Graduate School of Pharmaceutical Sciences (J.-i.S., H.I., K.M., A.A.) and Laboratory of Organic Chemistry, School of Pharmaceutical Sciences (M.S., Y.S.), University of Shizuoka, Shizuoka, Japan
| | - Yumiko Suzuki
- Center for Drug Discovery, Graduate School of Pharmaceutical Sciences (J.-i.S., H.I., K.M., A.A.) and Laboratory of Organic Chemistry, School of Pharmaceutical Sciences (M.S., Y.S.), University of Shizuoka, Shizuoka, Japan
| | - Akira Asai
- Center for Drug Discovery, Graduate School of Pharmaceutical Sciences (J.-i.S., H.I., K.M., A.A.) and Laboratory of Organic Chemistry, School of Pharmaceutical Sciences (M.S., Y.S.), University of Shizuoka, Shizuoka, Japan
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33
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Taulet N, Douanier A, Vitre B, Anguille C, Maurin J, Dromard Y, Georget V, Delaval B. IFT88 controls NuMA enrichment at k-fibers minus-ends to facilitate their re-anchoring into mitotic spindles. Sci Rep 2019; 9:10311. [PMID: 31312011 PMCID: PMC6635507 DOI: 10.1038/s41598-019-46605-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 07/02/2019] [Indexed: 02/06/2023] Open
Abstract
To build and maintain mitotic spindle architecture, molecular motors exert spatially regulated forces on microtubules (MT) minus-ends. This spatial regulation is required to allow proper chromosomes alignment through the organization of kinetochore fibers (k-fibers). NuMA was recently shown to target dynactin to MT minus-ends and thus to spatially regulate dynein activity. However, given that k-fibers are embedded in the spindle, our understanding of the machinery involved in the targeting of proteins to their minus-ends remains limited. Intraflagellar transport (IFT) proteins were primarily studied for their ciliary roles but they also emerged as key regulators of cell division. Taking advantage of MT laser ablation, we show here that IFT88 concentrates at k-fibers minus-ends and is required for their re-anchoring into spindles by controlling NuMA accumulation. Indeed, IFT88 interacts with NuMA and is required for its enrichment at newly generated k-fibers minus-ends. Combining nocodazole washout experiments and IFT88 depletion, we further show that IFT88 is required for the reorganization of k-fibers into spindles and thus for efficient chromosomes alignment in mitosis. Overall, we propose that IFT88 could serve as a mitotic MT minus-end adaptor to concentrate NuMA at minus-ends thus facilitating k-fibers incorporation into the main spindle.
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Affiliation(s)
- Nicolas Taulet
- CRBM, CNRS, Univ. Montpellier, Centrosome, cilia and pathologies Lab, 1919 Route de Mende, 34293, Montpellier, France.
| | - Audrey Douanier
- CRBM, CNRS, Univ. Montpellier, Centrosome, cilia and pathologies Lab, 1919 Route de Mende, 34293, Montpellier, France
| | - Benjamin Vitre
- CRBM, CNRS, Univ. Montpellier, Centrosome, cilia and pathologies Lab, 1919 Route de Mende, 34293, Montpellier, France
| | - Christelle Anguille
- CRBM, CNRS, Univ. Montpellier, Centrosome, cilia and pathologies Lab, 1919 Route de Mende, 34293, Montpellier, France
| | - Justine Maurin
- CRBM, CNRS, Univ. Montpellier, Centrosome, cilia and pathologies Lab, 1919 Route de Mende, 34293, Montpellier, France
| | - Yann Dromard
- Montpellier Ressources Imagerie, CRBM, CNRS, Univ. Montpellier, 1919 Route de Mende, 34293, Montpellier, France
| | - Virginie Georget
- Montpellier Ressources Imagerie, CRBM, CNRS, Univ. Montpellier, 1919 Route de Mende, 34293, Montpellier, France
| | - Benedicte Delaval
- CRBM, CNRS, Univ. Montpellier, Centrosome, cilia and pathologies Lab, 1919 Route de Mende, 34293, Montpellier, France.
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34
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David AF, Roudot P, Legant WR, Betzig E, Danuser G, Gerlich DW. Augmin accumulation on long-lived microtubules drives amplification and kinetochore-directed growth. J Cell Biol 2019; 218:2150-2168. [PMID: 31113824 PMCID: PMC6605806 DOI: 10.1083/jcb.201805044] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 12/19/2018] [Accepted: 04/30/2019] [Indexed: 12/31/2022] Open
Abstract
Vertebrate cells assemble mitotic spindles through multiple pathways. It is shown that Augmin-dependent, noncentrosomal nucleation generates the vast majority of microtubules in metaphase spindles. This results in a strong directional bias of microtubule growth toward individual kinetochores. Dividing cells reorganize their microtubule cytoskeleton into a bipolar spindle, which moves one set of sister chromatids to each nascent daughter cell. Early spindle assembly models postulated that spindle pole–derived microtubules search the cytoplasmic space until they randomly encounter a kinetochore to form a stable attachment. More recent work uncovered several additional, centrosome-independent microtubule generation pathways, but the contributions of each pathway to spindle assembly have remained unclear. Here, we combined live microscopy and mathematical modeling to show that most microtubules nucleate at noncentrosomal regions in dividing human cells. Using a live-cell probe that selectively labels aged microtubule lattices, we demonstrate that the distribution of growing microtubule plus ends can be almost entirely explained by Augmin-dependent amplification of long-lived microtubule lattices. By ultrafast 3D lattice light-sheet microscopy, we observed that this mechanism results in a strong directional bias of microtubule growth toward individual kinetochores. Our systematic quantification of spindle dynamics reveals highly coordinated microtubule growth during kinetochore fiber assembly.
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Affiliation(s)
- Ana F David
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
| | - Philippe Roudot
- Department of Cell Biology and Lyda Hill Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Wesley R Legant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Eric Betzig
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Gaudenz Danuser
- Department of Cell Biology and Lyda Hill Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
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35
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Thawani A, Stone HA, Shaevitz JW, Petry S. Spatiotemporal organization of branched microtubule networks. eLife 2019; 8:43890. [PMID: 31066674 PMCID: PMC6519983 DOI: 10.7554/elife.43890] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 05/07/2019] [Indexed: 11/13/2022] Open
Abstract
To understand how chromosomes are segregated, it is necessary to explain the precise spatiotemporal organization of microtubules (MTs) in the mitotic spindle. We use Xenopus egg extracts to study the nucleation and dynamics of MTs in branched networks, a process that is critical for spindle assembly. Surprisingly, new branched MTs preferentially originate near the minus-ends of pre-existing MTs. A sequential reaction model, consisting of deposition of nucleation sites on an existing MT, followed by rate-limiting nucleation of branches, reproduces the measured spatial profile of nucleation, the distribution of MT plus-ends and tubulin intensity. By regulating the availability of the branching effectors TPX2, augmin and γ-TuRC, combined with single-molecule observations, we show that first TPX2 is deposited on pre-existing MTs, followed by binding of augmin/γ-TuRC to result in the nucleation of branched MTs. In sum, regulating the localization and kinetics of nucleation effectors governs the architecture of branched MT networks.
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Affiliation(s)
- Akanksha Thawani
- Department of Chemical and Biological Engineering, Princeton University, Princeton, United States
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, United States
| | - Joshua W Shaevitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, United States.,Department of Physics, Princeton University, Princeton, United States
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, United States
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36
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The binding of Borealin to microtubules underlies a tension independent kinetochore-microtubule error correction pathway. Nat Commun 2019; 10:682. [PMID: 30737408 PMCID: PMC6368601 DOI: 10.1038/s41467-019-08418-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 12/19/2018] [Indexed: 12/22/2022] Open
Abstract
Proper chromosome segregation depends upon kinetochore phosphorylation by the Chromosome Passenger Complex (CPC). Current models suggest the activity of the CPC decreases in response to the inter-kinetochore stretch that accompanies the formation of bi-oriented microtubule attachments, however little is known about tension-independent CPC phosphoregulation. Microtubule bundles initially lie in close proximity to inner centromeres and become depleted by metaphase. Here we find these microtubules control kinetochore phosphorylation by the CPC in a tension independent manner via a microtubule-binding site on the Borealin subunit. Disruption of Borealin-microtubule interactions generates reduced phosphorylation of prometaphase kinetochores, improper kinetochore-microtubule attachments and weakened spindle checkpoint signals. Experimental and modeling evidence suggests that kinetochore phosphorylation is greatly stimulated when the CPC binds microtubules that lie near the inner centromere, even if kinetochores have high inter-kinetochore stretch. We propose the CPC senses its local environment through microtubule structures to control phosphorylation of kinetochores. How the chromosome passenger complex (CPC) phosphorylates the kinetochores that can be a micron away to control mitotic events is unknown. Here the authors find that the CPC directly binds microtubules near inner centromeres, which controls its ability to phosphorylate kinetochores independently of tension generated by kinetochore microtubule attachments.
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37
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Zou J, Huang RY, Jiang FN, Chen DX, Wang C, Han ZD, Liang YX, Zhong WD. Overexpression of TPX2 is associated with progression and prognosis of prostate cancer. Oncol Lett 2018; 16:2823-2832. [PMID: 30127868 PMCID: PMC6096215 DOI: 10.3892/ol.2018.9016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 04/06/2018] [Indexed: 12/17/2022] Open
Abstract
Targeting protein for Xenopus kinesin-like protein 2 (TPX2) activates Aurora kinase A during mitosis and targets its activity to the mitotic spindle, serving an important role in mitosis. It has been associated with different types of cancer and is considered to promote tumor growth. The aim of the present study was to explore the role of TPX2 in diagnosing prostate cancer (PCa). It was identified that TPX2 expression in PCa tissues was increased compared with benign prostate tissues. Microarray analysis demonstrated that TPX2 was positively associated with the Gleason score, tumor-node-metastasis (TNM) stage, clinicopathological stage, metastasis, overall survival and biochemical relapse-free survival. In vitro studies revealed that the high expression of TPX2 in PCa cells improved proliferative, invasive and migratory abilities, and repressed apoptosis of the PCa cells, without affecting tolerance to docetaxel. The results suggested that TPX2 serves as a tumorigenesis-promoting gene in PCa, and a potential therapeutic target for patients with PCa.
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Affiliation(s)
- Jun Zou
- Department of Emergency Surgery, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, Guangzhou, Guangdong 510150, P.R. China
| | - Rui-Yan Huang
- Department of Ultrasonography and Electrocardiograms, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong 510060, P.R. China
| | - Fu-Neng Jiang
- Department of Urology, Guangdong Key Laboratory of Clinical Molecular Medicine and Diagnostics, The Second Affiliated Hospital of South China University of Technology, Guangzhou, Guangdong 510180, P.R. China
| | - De-Xiong Chen
- Department of Emergency Surgery, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, Guangzhou, Guangdong 510150, P.R. China
| | - Cong Wang
- Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, P.R. China
| | - Zhao-Dong Han
- Department of Urology, Guangdong Key Laboratory of Clinical Molecular Medicine and Diagnostics, The Second Affiliated Hospital of South China University of Technology, Guangzhou, Guangdong 510180, P.R. China
| | - Yu-Xiang Liang
- Department of Urology, Guangdong Key Laboratory of Clinical Molecular Medicine and Diagnostics, The Second Affiliated Hospital of South China University of Technology, Guangzhou, Guangdong 510180, P.R. China
| | - Wei-De Zhong
- Department of Urology, Guangdong Key Laboratory of Clinical Molecular Medicine and Diagnostics, The Second Affiliated Hospital of South China University of Technology, Guangzhou, Guangdong 510180, P.R. China.,Department of Urology, Huadu District People's Hospital, Southern Medical University, Guangzhou, Guangdong 510800, P.R. China
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38
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Zulkipli I, Clark J, Hart M, Shrestha RL, Gul P, Dang D, Kasichiwin T, Kujawiak I, Sastry N, Draviam VM. Spindle rotation in human cells is reliant on a MARK2-mediated equatorial spindle-centering mechanism. J Cell Biol 2018; 217:3057-3070. [PMID: 29941476 PMCID: PMC6122980 DOI: 10.1083/jcb.201804166] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/18/2018] [Accepted: 05/24/2018] [Indexed: 12/11/2022] Open
Abstract
Unlike man-made wheels that are centered and rotated via an axle, the mitotic spindle of a human cell is rotated by external cortical pulling mechanisms. Zulkipli et al. identify MARK2’s role in equatorial spindle centering and astral microtubule length, which in turn control spindle rotation. The plane of cell division is defined by the final position of the mitotic spindle. The spindle is pulled and rotated to the correct position by cortical dynein. However, it is unclear how the spindle’s rotational center is maintained and what the consequences of an equatorially off centered spindle are in human cells. We analyzed spindle movements in 100s of cells exposed to protein depletions or drug treatments and uncovered a novel role for MARK2 in maintaining the spindle at the cell’s geometric center. Following MARK2 depletion, spindles glide along the cell cortex, leading to a failure in identifying the correct division plane. Surprisingly, spindle off centering in MARK2-depleted cells is not caused by excessive pull by dynein. We show that MARK2 modulates mitotic microtubule growth and length and that codepleting mitotic centromere-associated protein (MCAK), a microtubule destabilizer, rescues spindle off centering in MARK2-depleted cells. Thus, we provide the first insight into a spindle-centering mechanism needed for proper spindle rotation and, in turn, the correct division plane in human cells.
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Affiliation(s)
- Ihsan Zulkipli
- Department of Genetics, University of Cambridge, Cambridge, England, UK
| | - Joanna Clark
- Department of Genetics, University of Cambridge, Cambridge, England, UK
| | - Madeleine Hart
- School of Biological and Chemical Sciences, Queen Mary University of London, London, England, UK
| | - Roshan L Shrestha
- Department of Genetics, University of Cambridge, Cambridge, England, UK
| | - Parveen Gul
- School of Biological and Chemical Sciences, Queen Mary University of London, London, England, UK
| | - David Dang
- School of Biological and Chemical Sciences, Queen Mary University of London, London, England, UK.,Department of Informatics, King's College, London, England, UK
| | - Tami Kasichiwin
- School of Biological and Chemical Sciences, Queen Mary University of London, London, England, UK
| | - Izabela Kujawiak
- Department of Genetics, University of Cambridge, Cambridge, England, UK
| | - Nishanth Sastry
- Department of Informatics, King's College, London, England, UK
| | - Viji M Draviam
- School of Biological and Chemical Sciences, Queen Mary University of London, London, England, UK .,Department of Genetics, University of Cambridge, Cambridge, England, UK
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39
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Hsu WH, Wang WJ, Lin WY, Huang YM, Lai CC, Liao JC, Chen HC. Adducin-1 is essential for spindle pole integrity through its interaction with TPX2. EMBO Rep 2018; 19:embr.201745607. [PMID: 29925526 PMCID: PMC6073210 DOI: 10.15252/embr.201745607] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 05/21/2018] [Accepted: 05/28/2018] [Indexed: 11/25/2022] Open
Abstract
Bipolar spindle assembly is necessary to ensure the proper progression of cell division. Loss of spindle pole integrity leads to multipolar spindles and aberrant chromosomal segregation. However, the mechanism underlying the maintenance of spindle pole integrity remains unclear. In this study, we show that the actin‐binding protein adducin‐1 (ADD1) is phosphorylated at S726 during mitosis. S726‐phosphorylated ADD1 localizes to centrosomes, wherein it organizes into a rosette‐like structure at the pericentriolar material. ADD1 depletion causes centriole splitting and therefore results in multipolar spindles during mitosis, which can be restored by re‐expression of ADD1 and the phosphomimetic S726D mutant but not by the S726A mutant. Moreover, the phosphorylation of ADD1 at S726 is crucial for its interaction with TPX2, which is essential for spindle pole integrity. Together, our findings unveil a novel function of ADD1 in maintaining spindle pole integrity through its interaction with TPX2.
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Affiliation(s)
- Wen-Hsin Hsu
- Ph.D. Program in Tissue Engineering and Regenerative Medicine, National Chung Hsing University, Taichung, Taiwan
| | - Won-Jing Wang
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan
| | - Wan-Yi Lin
- Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan
| | - Yu-Min Huang
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan
| | - Chien-Chen Lai
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan
| | - Jung-Chi Liao
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
| | - Hong-Chen Chen
- Ph.D. Program in Tissue Engineering and Regenerative Medicine, National Chung Hsing University, Taichung, Taiwan .,Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan.,Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan.,Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan.,Cancer Progression Research Center, National Yang-Ming University, Taipei, Taiwan
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40
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Sikirzhytski V, Renda F, Tikhonenko I, Magidson V, McEwen BF, Khodjakov A. Microtubules assemble near most kinetochores during early prometaphase in human cells. J Cell Biol 2018; 217:2647-2659. [PMID: 29907657 PMCID: PMC6080938 DOI: 10.1083/jcb.201710094] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 04/15/2018] [Accepted: 05/21/2018] [Indexed: 11/22/2022] Open
Abstract
Correlative light electron microscopy reveals microtubule assembly near most kinetochores at the onset of mitosis in human cells. Conversion of the initially lateral interactions between these microtubules and kinetochores into end-on attachments is facilitated by the kinesin CenpE. This work suggests that kinetochore fibers predominately form via capture of locally nucleated noncentrosomal microtubules. For proper segregation during cell division, each chromosome must connect to the poles of the spindle via microtubule bundles termed kinetochore fibers (K-fibers). K-fibers form by two distinct mechanisms: (1) capture of astral microtubules nucleated at the centrosome by the chromosomes’ kinetochores or (2) attachment of kinetochores to noncentrosomal microtubules with subsequent transport of the minus ends of these microtubules toward the spindle poles. The relative contributions of these alternative mechanisms to normal spindle assembly remain unknown. In this study, we report that most kinetochores in human cells develop K-fibers via the second mechanism. Correlative light electron microscopy demonstrates that from the onset of spindle assembly, short randomly oriented noncentrosomal microtubules appear in the immediate vicinity of the kinetochores. Initially, these microtubules interact with the kinetochores laterally, but end-on attachments form rapidly in the first 3 min of prometaphase. Conversion from lateral to end-on interactions is impeded upon inhibition of the plus end–directed kinetochore-associated kinesin CenpE.
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Affiliation(s)
| | - Fioranna Renda
- Wadsworth Center, New York State Department of Health, Albany, NY
| | - Irina Tikhonenko
- Wadsworth Center, New York State Department of Health, Albany, NY
| | | | - Bruce F McEwen
- Wadsworth Center, New York State Department of Health, Albany, NY
| | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, NY .,Rensselaer Polytechnic Institute, Troy, NY
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41
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Mitotic cell death induction by targeting the mitotic spindle with tubulin-inhibitory indole derivative molecules. Oncotarget 2017; 8:19738-19759. [PMID: 28160569 PMCID: PMC5386718 DOI: 10.18632/oncotarget.14980] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 01/06/2017] [Indexed: 01/08/2023] Open
Abstract
Tubulin-targeting molecules are widely used cancer therapeutic agents. They inhibit microtubule-based structures, including the mitotic spindle, ultimately preventing cell division. The final fates of microtubule-inhibited cells are however often heterogeneous and difficult to predict. While recent work has provided insight into the cell response to inhibitors of microtubule dynamics (taxanes), the cell response to tubulin polymerization inhibitors remains less well characterized. Arylthioindoles (ATIs) are recently developed tubulin inhibitors. We previously identified ATI members that effectively inhibit tubulin polymerization in vitro and cancer cell growth in bulk cell viability assays. Here we characterise in depth the response of cancer cell lines to five selected ATIs. We find that all ATIs arrest mitotic progression, yet subsequently yield distinct cell fate profiles in time-lapse recording assays, indicating that molecules endowed with similar tubulin polymerization inhibitory activity in vitro can in fact display differential efficacy in living cells. Individual ATIs induce cytological phenotypes of increasing severity in terms of damage to the mitotic apparatus. That differentially triggers MCL-1 down-regulation and caspase-3 activation, and underlies the terminal fate of treated cells. Collectively, these results contribute to define the cell response to tubulin inhibitors and pinpoint potentially valuable molecules that can increase the molecular diversity of tubulin-targeting agents.
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42
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Gilistro E, de Turris V, Damizia M, Verrico A, Moroni S, De Santis R, Rosa A, Lavia P. Importin-β and CRM1 control a RANBP2 spatiotemporal switch essential for mitotic kinetochore function. J Cell Sci 2017; 130:2564-2578. [PMID: 28600321 DOI: 10.1242/jcs.197905] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 06/05/2017] [Indexed: 12/30/2022] Open
Abstract
Protein conjugation with small ubiquitin-related modifier (SUMO) is a post-translational modification that modulates protein interactions and localisation. RANBP2 is a large nucleoporin endowed with SUMO E3 ligase and SUMO-stabilising activity, and is implicated in some cancer types. RANBP2 is part of a larger complex, consisting of SUMO-modified RANGAP1, the GTP-hydrolysis activating factor for the GTPase RAN. During mitosis, the RANBP2-SUMO-RANGAP1 complex localises to the mitotic spindle and to kinetochores after microtubule attachment. Here, we address the mechanisms that regulate this localisation and how they affect kinetochore functions. Using proximity ligation assays, we find that nuclear transport receptors importin-β and CRM1 play essential roles in localising the RANBP2-SUMO-RANGAP1 complex away from, or at kinetochores, respectively. Using newly generated inducible cell lines, we show that overexpression of nuclear transport receptors affects the timing of RANBP2 localisation in opposite ways. Concomitantly, kinetochore functions are also affected, including the accumulation of SUMO-conjugated topoisomerase-IIα and stability of kinetochore fibres. These results delineate a novel mechanism through which nuclear transport receptors govern the functional state of kinetochores by regulating the timely deposition of RANBP2.
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Affiliation(s)
- Eugenia Gilistro
- CNR National Research Council of Italy, Institute of Molecular Biology and Pathology (IBPM), ℅ Department of Biology and Biotechnology, Sapienza Università di Roma, Via degli Apuli 4, 00185 Rome, Italy
| | - Valeria de Turris
- Istituto Italiano di Tecnologia, Center for Life Nanoscience@Sapienza, Viale Regina Elena 291, 00161 Rome, Italy
| | - Michela Damizia
- CNR National Research Council of Italy, Institute of Molecular Biology and Pathology (IBPM), ℅ Department of Biology and Biotechnology, Sapienza Università di Roma, Via degli Apuli 4, 00185 Rome, Italy
| | - Annalisa Verrico
- CNR National Research Council of Italy, Institute of Molecular Biology and Pathology (IBPM), ℅ Department of Biology and Biotechnology, Sapienza Università di Roma, Via degli Apuli 4, 00185 Rome, Italy
| | - Sara Moroni
- CNR National Research Council of Italy, Institute of Molecular Biology and Pathology (IBPM), ℅ Department of Biology and Biotechnology, Sapienza Università di Roma, Via degli Apuli 4, 00185 Rome, Italy
| | - Riccardo De Santis
- Istituto Italiano di Tecnologia, Center for Life Nanoscience@Sapienza, Viale Regina Elena 291, 00161 Rome, Italy
- Department of Biology and Biotechnology 'Charles Darwin', Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Alessandro Rosa
- Istituto Italiano di Tecnologia, Center for Life Nanoscience@Sapienza, Viale Regina Elena 291, 00161 Rome, Italy
- Department of Biology and Biotechnology 'Charles Darwin', Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Patrizia Lavia
- CNR National Research Council of Italy, Institute of Molecular Biology and Pathology (IBPM), ℅ Department of Biology and Biotechnology, Sapienza Università di Roma, Via degli Apuli 4, 00185 Rome, Italy
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43
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Destouni A, Vermeesch JR. How can zygotes segregate entire parental genomes into distinct blastomeres? The zygote metaphase revisited. Bioessays 2017; 39. [DOI: 10.1002/bies.201600226] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Aspasia Destouni
- Laboratory of Cytogenetics and Genome Research; Center of Human Genetics; KU Leuven; Leuven Belgium
| | - Joris R. Vermeesch
- Laboratory of Cytogenetics and Genome Research; Center of Human Genetics; KU Leuven; Leuven Belgium
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44
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Abstract
The mitotic spindle has a crucial role in ensuring the accurate segregation of chromosomes into the two daughter cells during cell division, which is paramount for maintaining genome integrity. It is a self-organized and dynamic macromolecular structure that is constructed from microtubules, microtubule-associated proteins and motor proteins. Thirty years of research have led to the identification of centrosome-, chromatin- and microtubule-mediated microtubule nucleation pathways that each contribute to mitotic spindle assembly. Far from being redundant pathways, data are now emerging regarding how they function together to ensure the timely completion of mitosis. We are also beginning to comprehend the multiple mechanisms by which cells regulate spindle scaling. Together, this research has increased our understanding of how cells coordinate hundreds of proteins to assemble the dynamic, precise and robust structure that is the mitotic spindle.
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45
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Kapoor TM. Metaphase Spindle Assembly. BIOLOGY 2017; 6:biology6010008. [PMID: 28165376 PMCID: PMC5372001 DOI: 10.3390/biology6010008] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/17/2017] [Accepted: 01/19/2017] [Indexed: 01/31/2023]
Abstract
A microtubule-based bipolar spindle is required for error-free chromosome segregation during cell division. In this review I discuss the molecular mechanisms required for the assembly of this dynamic micrometer-scale structure in animal cells.
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Affiliation(s)
- Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, the Rockefeller University, New York, NY 10065, USA.
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46
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Lim NR, Yeap YYC, Ang CS, Williamson NA, Bogoyevitch MA, Quinn LM, Ng DCH. Aurora A phosphorylation of WD40-repeat protein 62 in mitotic spindle regulation. Cell Cycle 2016; 15:413-24. [PMID: 26713495 DOI: 10.1080/15384101.2015.1127472] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Mitotic spindle organization is regulated by centrosomal kinases that potentiate recruitment of spindle-associated proteins required for normal mitotic progress including the microcephaly protein WD40-repeat protein 62 (WDR62). WDR62 functions underlie normal brain development as autosomal recessive mutations and wdr62 loss cause microcephaly. Here we investigate the signaling interactions between WDR62 and the mitotic kinase Aurora A (AURKA) that has been recently shown to cooperate to control brain size in mice. The spindle recruitment of WDR62 is closely correlated with increased levels of AURKA following mitotic entry. We showed that depletion of TPX2 attenuated WDR62 localization at spindle poles indicating that TPX2 co-activation of AURKA is required to recruit WDR62 to the spindle. We demonstrated that AURKA activity contributed to the mitotic phosphorylation of WDR62 residues Ser49 and Thr50 and phosphorylation of WDR62 N-terminal residues was required for spindle organization and metaphase chromosome alignment. Our analysis of several MCPH-associated WDR62 mutants (V65M, R438H and V1314RfsX18) that are mislocalized in mitosis revealed that their interactions and phosphorylation by AURKA was substantially reduced consistent with the notion that AURKA is a key determinant of WDR62 spindle recruitment. Thus, our study highlights the role of AURKA signaling in the spatiotemporal control of WDR62 at spindle poles where it maintains spindle organization.
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Affiliation(s)
- Nicholas R Lim
- a Department of Biochemistry and Molecular Biology , University of Melbourne , Victoria , Australia.,b Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Victoria , Australia
| | - Yvonne Y C Yeap
- a Department of Biochemistry and Molecular Biology , University of Melbourne , Victoria , Australia.,d School of Biomedical Sciences, University of Queensland , St Lucia , Australia
| | - Ching-Seng Ang
- b Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Victoria , Australia
| | - Nicholas A Williamson
- b Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Victoria , Australia
| | - Marie A Bogoyevitch
- a Department of Biochemistry and Molecular Biology , University of Melbourne , Victoria , Australia.,b Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Victoria , Australia
| | - Leonie M Quinn
- c Department of Anatomy and Neuroscience , University of Melbourne , Victoria , Australia
| | - Dominic C H Ng
- a Department of Biochemistry and Molecular Biology , University of Melbourne , Victoria , Australia.,d School of Biomedical Sciences, University of Queensland , St Lucia , Australia
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Mann BJ, Balchand SK, Wadsworth P. Regulation of Kif15 localization and motility by the C-terminus of TPX2 and microtubule dynamics. Mol Biol Cell 2016; 28:65-75. [PMID: 27852894 PMCID: PMC5221630 DOI: 10.1091/mbc.e16-06-0476] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/04/2016] [Accepted: 11/07/2016] [Indexed: 12/31/2022] Open
Abstract
Mitotic motor proteins generate force to establish and maintain spindle bipolarity, but how they are temporally and spatially regulated in vivo is unclear. Prior work demonstrated that a microtubule-associated protein, TPX2, targets kinesin-5 and kinesin-12 motors to spindle microtubules. The C-terminal domain of TPX2 contributes to the localization and motility of the kinesin-5, Eg5, but it is not known whether this domain regulates kinesin-12, Kif15. We found that the C-terminal domain of TPX2 contributes to the localization of Kif15 to spindle microtubules in cells and suppresses motor walking in vitro. Kif15 and Eg5 are partially redundant motors, and overexpressed Kif15 can drive spindle formation in the absence of Eg5 activity. Kif15-dependent bipolar spindle formation in vivo requires the C-terminal domain of TPX2. In the spindle, fluorescent puncta of GFP-Kif15 move toward the equatorial region at a rate equivalent to microtubule growth. Reduction of microtubule growth with paclitaxel suppresses GFP-Kif15 motility, demonstrating that dynamic microtubules contribute to Kif15 behavior. Our results show that the C-terminal region of TPX2 regulates Kif15 in vitro, contributes to motor localization in cells, and is required for Kif15 force generation in vivo and further reveal that dynamic microtubules contribute to Kif15 behavior in vivo.
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Affiliation(s)
- Barbara J Mann
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
| | - Sai K Balchand
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
| | - Patricia Wadsworth
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
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Simunić J, Tolić IM. Mitotic Spindle Assembly: Building the Bridge between Sister K-Fibers. Trends Biochem Sci 2016; 41:824-833. [DOI: 10.1016/j.tibs.2016.07.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 07/05/2016] [Accepted: 07/08/2016] [Indexed: 12/30/2022]
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Abstract
TPX2 is a microtubule-associated protein that is required for mitotic spindle function.
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Affiliation(s)
- Pat Wadsworth
- Department of Biology, University of Massachusetts Amherst, Amherst, MA, USA.
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50
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Cavazza T, Malgaretti P, Vernos I. The sequential activation of the mitotic microtubule assembly pathways favors bipolar spindle formation. Mol Biol Cell 2016; 27:2935-45. [PMID: 27489339 PMCID: PMC5042580 DOI: 10.1091/mbc.e16-05-0322] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 07/27/2016] [Indexed: 01/22/2023] Open
Abstract
A combination of experimental data obtained in somatic cells and Xenopus egg extracts and modeling suggests a novel function for centrosome maturation that balances the activity of the mitotic microtubule assembly pathways favoring bipolar spindle formation. Centrosome maturation is the process by which the duplicated centrosomes recruit pericentriolar components and increase their microtubule nucleation activity before mitosis. The role of this process in cells entering mitosis has been mostly related to the separation of the duplicated centrosomes and thereby to the assembly of a bipolar spindle. However, spindles can form without centrosomes. In fact, all cells, whether they have centrosomes or not, rely on chromatin-driven microtubule assembly to form a spindle. To test whether the sequential activation of these microtubule assembly pathways, defined by centrosome maturation and nuclear envelope breakdown, plays any role in spindle assembly, we combined experiments in tissue culture cells and Xenopus laevis egg extracts with a mathematical model. We found that interfering with the sequential activation of the microtubule assembly pathways compromises bipolar spindle assembly in tissue culture cells but not in X. laevis egg extracts. Our data suggest a novel function for centrosome maturation that determines the contribution of the chromosomal microtubule assembly pathway and favors bipolar spindle formation in most animal cells in which tubulin is in limiting amounts.
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Affiliation(s)
- Tommaso Cavazza
- Cell and Developmental Biology Programme, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Paolo Malgaretti
- Departament de Fisica Fonamental, Universitat de Barcelona, 08028 Barcelona, Spain Max-Planck-Institut für Intelligente Systeme and IV. Institut für Theoretische Physik, Universität Stuttgart, D-70569 Stuttgart, Germany
| | - Isabelle Vernos
- Cell and Developmental Biology Programme, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain Institució Catalana de Recerca I Estudis Avançats, 08010 Barcelona, Spain
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