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Abdel-Salam GMH, Hellmuth S, Gradhand E, Käseberg S, Winter J, Pabst AS, Eid MM, Thiele H, Nürnberg P, Budde BS, Toliat MR, Brecht IB, Schroeder C, Gschwind A, Ossowski S, Häuser F, Rossmann H, Abdel-Hamid MS, Hegazy I, Mohamed AG, Schneider DT, Bertoli-Avella A, Bauer P, Pearring JN, Pfundt R, Hoischen A, Gilissen C, Strand D, Zechner U, Tashkandi SA, Faqeih EA, Stemmann O, Strand S, Bolz HJ. Biallelic MAD2L1BP (p31comet) mutation is associated with mosaic aneuploidy and juvenile granulosa cell tumors. JCI Insight 2023; 8:e170079. [PMID: 37796616 PMCID: PMC10721328 DOI: 10.1172/jci.insight.170079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 10/02/2023] [Indexed: 10/07/2023] Open
Abstract
MAD2L1BP-encoded p31comet mediates Trip13-dependent disassembly of Mad2- and Rev7-containing complexes and, through this antagonism, promotes timely spindle assembly checkpoint (SAC) silencing, faithful chromosome segregation, insulin signaling, and homology-directed repair (HDR) of DNA double-strand breaks. We identified a homozygous MAD2L1BP nonsense variant, R253*, in 2 siblings with microcephaly, epileptic encephalopathy, and juvenile granulosa cell tumors of ovary and testis. Patient-derived cells exhibited high-grade mosaic variegated aneuploidy, slowed-down proliferation, and instability of truncated p31comet mRNA and protein. Corresponding recombinant p31comet was defective in Trip13, Mad2, and Rev7 binding and unable to support SAC silencing or HDR. Furthermore, C-terminal truncation abrogated an identified interaction of p31comet with tp53. Another homozygous truncation, R227*, detected in an early-deceased patient with low-level aneuploidy, severe epileptic encephalopathy, and frequent blood glucose elevations, likely corresponds to complete loss of function, as in Mad2l1bp-/- mice. Thus, human mutations of p31comet are linked to aneuploidy and tumor predisposition.
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Affiliation(s)
- Ghada M. H. Abdel-Salam
- Department of Clinical Genetics, Human Genetics and Genome Research Institute, National Research Centre, Cairo, Egypt
| | | | - Elise Gradhand
- Senckenberg Institute of Pathology, University Hospital Frankfurt, Frankfurt, Germany
| | - Stephan Käseberg
- Institute of Human Genetics, University Medical Center Mainz, Mainz, Germany
| | - Jennifer Winter
- Institute of Human Genetics, University Medical Center Mainz, Mainz, Germany
| | - Ann-Sophie Pabst
- Institute of Human Genetics, University Medical Center Mainz, Mainz, Germany
| | - Maha M. Eid
- Human Cytogenetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo, Egypt
| | | | - Peter Nürnberg
- Cologne Center for Genomics and
- Center for Molecular Medicine Cologne, University Hospital of Cologne, University of Cologne, Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | | | | | - Ines B. Brecht
- Paediatric Haematology/Oncology, Department of Paediatrics, University Hospital Tübingen, Tübingen, Germany
| | - Christopher Schroeder
- Institute of Medical Genetics and Applied Genomics, Eberhard-Karls University, Tübingen, Germany
| | - Axel Gschwind
- Institute of Medical Genetics and Applied Genomics, Eberhard-Karls University, Tübingen, Germany
| | - Stephan Ossowski
- Institute of Medical Genetics and Applied Genomics, Eberhard-Karls University, Tübingen, Germany
| | - Friederike Häuser
- Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Mainz, Mainz, Germany
| | - Heidi Rossmann
- Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Mainz, Mainz, Germany
| | - Mohamed S. Abdel-Hamid
- Medical Molecular Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo, Egypt
| | - Ibrahim Hegazy
- Department of Clinical Genetics, Human Genetics and Genome Research Institute, National Research Centre, Cairo, Egypt
| | - Ahmed G. Mohamed
- Pediatrics Department, Faculty of Medicine, Cairo University, Cairo, Egypt
| | | | | | | | - Jillian N. Pearring
- Department of Ophthalmology and Visual Sciences and
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, Michigan, USA
| | - Rolph Pfundt
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences and
| | - Alexander Hoischen
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences and
- Department of Internal Medicine, Radboud University Medical Center, Nijmegen, Netherlands
| | - Christian Gilissen
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences and
| | - Dennis Strand
- Department of Internal Medicine I, University Medical Center Mainz, Mainz, Germany
| | - Ulrich Zechner
- Institute of Human Genetics, University Medical Center Mainz, Mainz, Germany
- Senckenberg Centre for Human Genetics, Frankfurt am Main, Germany
| | - Soha A. Tashkandi
- Cytogenetics Laboratory, Pathology and Clinical Laboratory Medicine Administration (PCLMA), King Fahad Medical City, Second Central Healthcare Cluster (C2), Riyadh, Saudi Arabia
| | - Eissa A. Faqeih
- Section of Medical Genetics, Children’s Specialist Hospital, King Fahad Medical City, Riyadh, Saudi Arabia
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Bayreuth, Germany
| | - Susanne Strand
- Department of Internal Medicine I, University Medical Center Mainz, Mainz, Germany
| | - Hanno J. Bolz
- Senckenberg Centre for Human Genetics, Frankfurt am Main, Germany
- Institute of Human Genetics, University Hospital of Cologne, University of Cologne, Cologne, Germany
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Hellmuth S, Gómez-H L, Pendás AM, Stemmann O. Securin-independent regulation of separase by checkpoint-induced shugoshin-MAD2. Nature 2020; 580:536-541. [PMID: 32322060 DOI: 10.1038/s41586-020-2182-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 01/31/2020] [Indexed: 01/27/2023]
Abstract
Separation of eukaryotic sister chromatids during the cell cycle is timed by the spindle assembly checkpoint (SAC) and ultimately triggered when separase cleaves cohesion-mediating cohesin1-3. Silencing of the SAC during metaphase activates the ubiquitin ligase APC/C (anaphase-promoting complex, also known as the cyclosome) and results in the proteasomal destruction of the separase inhibitor securin1. In the absence of securin, mammalian chromosomes still segregate on schedule, but it is unclear how separase is regulated under these conditions4,5. Here we show that human shugoshin 2 (SGO2), an essential protector of meiotic cohesin with unknown functions in the soma6,7, is turned into a separase inhibitor upon association with SAC-activated MAD2. SGO2-MAD2 can functionally replace securin and sequesters most separase in securin-knockout cells. Acute loss of securin and SGO2, but not of either protein individually, resulted in separase deregulation associated with premature cohesin cleavage and cytotoxicity. Similar to securin8,9, SGO2 is a competitive inhibitor that uses a pseudo-substrate sequence to block the active site of separase. APC/C-dependent ubiquitylation and action of the AAA-ATPase TRIP13 in conjunction with the MAD2-specific adaptor p31comet liberate separase from SGO2-MAD2 in vitro. The latter mechanism facilitates a considerable degree of sister chromatid separation in securin-knockout cells that lack APC/C activity. Thus, our results identify an unexpected function of SGO2 in mitotically dividing cells and a mechanism of separase regulation that is independent of securin but still supervised by the SAC.
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Affiliation(s)
| | - Laura Gómez-H
- Molecular Mechanisms Program, Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer (CSIC-Universidad de Salamanca), Salamanca, Spain
| | - Alberto M Pendás
- Molecular Mechanisms Program, Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer (CSIC-Universidad de Salamanca), Salamanca, Spain
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Bayreuth, Germany.
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3
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Wild T, Budzowska M, Hellmuth S, Eibes S, Karemore G, Barisic M, Stemmann O, Choudhary C. Deletion of APC7 or APC16 Allows Proliferation of Human Cells without the Spindle Assembly Checkpoint. Cell Rep 2019; 25:2317-2328.e5. [PMID: 30485802 PMCID: PMC6289045 DOI: 10.1016/j.celrep.2018.10.104] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 09/07/2018] [Accepted: 10/29/2018] [Indexed: 11/17/2022] Open
Abstract
The multisubunit ubiquitin ligase APC/C (anaphase-promoting complex/cyclosome) is essential for mitosis by promoting timely degradation of cyclin B1. APC/C is tightly regulated by the spindle assembly checkpoint (SAC), which involves MPS1 and MAD2-dependent temporal inhibition of APC/C. We analyzed the contribution of the APC/C subunits APC7 and APC16 to APC/C composition and function in human cells. APC16 is required for APC7 assembly into APC/C, whereas APC16 assembles independently of APC7. APC7 and APC16 knockout cells display no major defects in mitotic progression, cyclin B1 degradation, or SAC response, but APC/C lacking these two subunits shows reduced ubiquitylation activity in vitro. Strikingly, deletion of APC7 or APC16 is sufficient to provide synthetic viability to MAD2 deletion. ΔAPC7ΔMAD2 cells display accelerated mitosis and require SAC-independent MPS1 function for genome stability. These findings reveal that the composition of APC/C critically influences the importance of the SAC in humans. APC16 is required for in vivo assembly of APC7 into APC/C APC7 or APC16 deletion has no major effect on mitosis Deletion of APC7 or APC16 provides synthetic viability to MAD2 deletion
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Affiliation(s)
- Thomas Wild
- Proteomics Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Magda Budzowska
- Proteomics Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark; Center for Chromosome Stability (CCS), Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Susanne Hellmuth
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Susana Eibes
- Danish Cancer Society Research Center, Cell Division Laboratory, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Gopal Karemore
- Protein Imaging Platform, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Marin Barisic
- Danish Cancer Society Research Center, Cell Division Laboratory, Strandboulevarden 49, 2100 Copenhagen, Denmark; Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Chunaram Choudhary
- Proteomics Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark.
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Abstract
Separase, a cysteine protease of the CD clan, triggers chromosome segregation during mitosis by cleaving the cohesin ring entrapping the two sister chromatids. Deregulated separase activity is associated with aneuploidy, a hallmark of most human cancers. In fact, separase is highly overexpressed in many solid cancers, making it an attractive chemotherapeutic target. To identify small molecules capable of inhibiting separase in its complex cellular environment, we established a highly sensitive assay to quantify separase activity in cells and screened a 51 009-member library for separase inhibitors. In vitro assays confirmed that the identified compounds efficiently inhibited separase, while not affecting caspase-1, another CD-clan protease structurally related to separase. Importantly, HeLa cells with compromised separase activity displayed severe chromosome segregation defects upon compound treatment, confirming that the identified inhibitors are bioactive in tumor tissue culture cells. Structure-activity relationship studies succeeded in the optimization of the most promising inhibitor. Overall, this study demonstrates the feasibility of identifying separase-specific inhibitors, which serve as promising lead compounds for the development of clinically relevant separase inhibiting drugs.
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Affiliation(s)
- Lars Henschke
- Department of Biology and Konstanz Research School Chemical-Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78467 Konstanz, Germany
| | - Matthias Frese
- Department of Chemistry and Konstanz Research School Chemical-Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78467 Konstanz, Germany
| | - Susanne Hellmuth
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Andreas Marx
- Department of Chemistry and Konstanz Research School Chemical-Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78467 Konstanz, Germany
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Thomas U. Mayer
- Department of Biology and Konstanz Research School Chemical-Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78467 Konstanz, Germany
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Hellmuth S, Gutiérrez-Caballero C, Llano E, Pendás AM, Stemmann O. Local activation of mammalian separase in interphase promotes double-strand break repair and prevents oncogenic transformation. EMBO J 2018; 37:embj.201899184. [PMID: 30305303 DOI: 10.15252/embj.201899184] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 09/17/2018] [Accepted: 09/19/2018] [Indexed: 11/09/2022] Open
Abstract
Separase halves eukaryotic chromosomes in M-phase by cleaving cohesin complexes holding sister chromatids together. Whether this essential protease functions also in interphase and/or impacts carcinogenesis remains largely unknown. Here, we show that mammalian separase is recruited to DNA double-strand breaks (DSBs) where it is activated to locally cleave cohesin and facilitate homology-directed repair (HDR). Inactivating phosphorylation of its NES, arginine methylation of its RG-repeats, and sumoylation redirect separase from the cytosol to DSBs. In vitro assays suggest that DNA damage response-relevant ATM, PRMT1, and Mms21 represent the corresponding kinase, methyltransferase, and SUMO ligase, respectively. SEPARASE heterozygosity not only debilitates HDR but also predisposes primary embryonic fibroblasts to neoplasia and mice to chemically induced skin cancer. Thus, tethering of separase to DSBs and confined cohesin cleavage promote DSB repair in G2 cells. Importantly, this conserved interphase function of separase protects mammalian cells from oncogenic transformation.
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Affiliation(s)
| | | | - Elena Llano
- Centro de Investigación del Cáncer (CSIC-Universidad de Salamanca), Salamanca, Spain.,Departamento de Fisiología, Universidad de Salamanca, Salamanca, Spain
| | - Alberto M Pendás
- Centro de Investigación del Cáncer (CSIC-Universidad de Salamanca), Salamanca, Spain
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Bayreuth, Germany
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Wolf PG, Cuba Ramos A, Kenzel J, Neumann B, Stemmann O. Studying meiotic cohesin in somatic cells reveals that Rec8-containing cohesin requires Stag3 to function and is regulated by Wapl and sororin. J Cell Sci 2018; 131:jcs212100. [PMID: 29724914 DOI: 10.1242/jcs.212100] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 04/26/2018] [Indexed: 01/21/2023] Open
Abstract
The DNA-embracing, ring-shaped multiprotein complex cohesin mediates sister chromatid cohesion and is stepwise displaced in mitosis by Wapl and separase (also known as ESPL1) to facilitate anaphase. Proper regulation of chromosome cohesion throughout meiosis is critical for preventing formation of aneuploid gametes, which are associated with trisomies and infertility in humans. Studying cohesion in meiocytes is complicated by their difficult experimental amenability and the absence of cohesin turnover. Here, we use cultured somatic cells to unravel fundamental aspects of meiotic cohesin. When expressed in Hek293 cells, the kleisin Rec8 displays no affinity for the peripheral cohesin subunits Stag1 or Stag2 and remains cytoplasmic. However, co-expression of Stag3 is sufficient for Rec8 to enter the nucleus, load onto chromatin, and functionally replace its mitotic counterpart Scc1 (also known as RAD21) during sister chromatid cohesion and dissolution. Rec8-Stag3 cohesin physically interacts with Pds5, Wapl and sororin (also known as CDCA5). Importantly, Rec8-Stag3 cohesin is shown to be susceptible to Wapl-dependent ring opening and sororin-mediated protection. These findings exemplify that our model system is suitable to rapidly generate testable predictions for important unresolved issues of meiotic cohesion regulation.
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Affiliation(s)
- Peter G Wolf
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Alexander Cuba Ramos
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Julia Kenzel
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Brigitte Neumann
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
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Ferencz C, Guigas G, Veres A, Neumann B, Stemmann O, Weiss M. In Vitro Reconstitution of the Endoplasmic Reticulum. ACTA ACUST UNITED AC 2017; 76:11.22.1-11.22.16. [DOI: 10.1002/cpcb.30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Csilla‐Maria Ferencz
- Department of Experimental Physics I, University of Bayreuth Bayreuth Germany
- Current address: Max Planck Institute of Colloids and Interfaces, Department of Theory and Bio‐Systems Potsdam Germany
| | - Gernot Guigas
- Department of Experimental Physics I, University of Bayreuth Bayreuth Germany
- Current address: Institute of Applied Physics, Karlsruhe Institute of Technology (KIT) Karlsruhe Germany
| | - Andreas Veres
- Department of Experimental Physics I, University of Bayreuth Bayreuth Germany
| | | | - Olaf Stemmann
- Department of Genetics, University of Bayreuth Bayreuth Germany
| | - Matthias Weiss
- Department of Experimental Physics I, University of Bayreuth Bayreuth Germany
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Malhotra S, Vinod PK, Mansfeld J, Stemmann O, Mayer TU. RETRACTED: The Anaphase-Promoting Complex/Cyclosome Is Essential for Entry into Meiotic M-Phase. Dev Cell 2016; 36:94-102. [DOI: 10.1016/j.devcel.2015.12.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 11/12/2015] [Accepted: 12/03/2015] [Indexed: 11/16/2022]
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Mohr L, Buheitel J, Schöckel L, Karalus D, Mayer B, Stemmann O. An Alternatively Spliced Bifunctional Localization Signal Reprograms Human Shugoshin 1 to Protect Centrosomal Instead of Centromeric Cohesin. Cell Rep 2015; 12:2156-68. [PMID: 26365192 DOI: 10.1016/j.celrep.2015.08.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 07/24/2015] [Accepted: 08/12/2015] [Indexed: 12/23/2022] Open
Abstract
Separation of human sister chromatids involves the removal of DNA embracing cohesin ring complexes. Ring opening occurs by prophase-pathway-dependent phosphorylation and separase-mediated cleavage, with the former being antagonized at centromeres by Sgo1-dependent PP2A recruitment. Intriguingly, prophase pathway signaling and separase's proteolytic activity also bring about centriole disengagement, whereas Sgo1 is again counteracting this licensing step of later centrosome duplication. Here, we demonstrate that alternative splice variants of human Sgo1 specifically and exclusively localize and function either at centromeres or centrosomes. A small C-terminal peptide encoded by exon 9 of SGO1 (CTS for centrosomal targeting signal of human Sgo1) is necessary and sufficient to drive centrosomal localization and simultaneously abrogate centromeric association of corresponding Sgo1 isoforms. Cohesin is shown to be a target of the prophase pathway at centrosomes and protected by Sgo1-PP2A. Accordingly, premature centriole disengagement in response to Sgo1 depletion is suppressed by blocking ring opening of an engineered cohesin.
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Affiliation(s)
- Lisa Mohr
- Department of Genetics, University of Bayreuth, 95444 Bayreuth, Germany
| | - Johannes Buheitel
- Department of Genetics, University of Bayreuth, 95444 Bayreuth, Germany
| | - Laura Schöckel
- Department of Genetics, University of Bayreuth, 95444 Bayreuth, Germany
| | - Dorothea Karalus
- Department of Genetics, University of Bayreuth, 95444 Bayreuth, Germany
| | - Bernd Mayer
- Department of Genetics, University of Bayreuth, 95444 Bayreuth, Germany; Annikki GmbH, 8020 Graz, Austria
| | - Olaf Stemmann
- Department of Genetics, University of Bayreuth, 95444 Bayreuth, Germany.
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10
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Hellmuth S, Rata S, Brown A, Heidmann S, Novak B, Stemmann O. Human chromosome segregation involves multi-layered regulation of separase by the peptidyl-prolyl-isomerase Pin1. Mol Cell 2015; 58:495-506. [PMID: 25921067 DOI: 10.1016/j.molcel.2015.03.025] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 01/23/2015] [Accepted: 03/18/2015] [Indexed: 10/23/2022]
Abstract
Ring-shaped cohesin keeps sister chromatids paired until cleavage of its Scc1/Rad21 subunit by separase triggers chromosome segregation in anaphase. Vertebrate separase is held inactive by mutually exclusive binding to securin or Cdk1-cyclin B1 and becomes unleashed only upon ubiquitin-dependent degradation of these regulators. Although most separase is usually found in association with securin, this anaphase inhibitor is dispensable for murine life while Cdk1-cyclin B1-dependent control of separase is essential. Here, we show that securin-independent inhibition of separase by Cdk1-cyclin B1 in early mitosis requires the phosphorylation-specific peptidyl-prolyl cis/trans isomerase Pin1. Furthermore, isomerization of previously securin-bound separase at the metaphase-to-anaphase transition renders it resistant to re-inhibition by residual securin. At the same time, isomerization also limits the half-life of separase's proteolytic activity, explaining how cohesin can be reloaded onto telophase chromatin in the absence of securin and cyclin B1 without being cleaved.
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Affiliation(s)
- Susanne Hellmuth
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Scott Rata
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Andreas Brown
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Stefan Heidmann
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Bela Novak
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany.
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Hellmuth S, Pöhlmann C, Brown A, Böttger F, Sprinzl M, Stemmann O. Positive and negative regulation of vertebrate separase by Cdk1-cyclin B1 may explain why securin is dispensable. J Biol Chem 2015; 290:8002-10. [PMID: 25659430 DOI: 10.1074/jbc.m114.615310] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sister chromatid cohesion is established during replication by entrapment of both dsDNAs within the cohesin ring complex. It is dissolved in anaphase when separase, a giant cysteine endopeptidase, cleaves the Scc1/Rad21 subunit of cohesin, thereby triggering chromosome segregation. Separase is held inactive by association with securin until this anaphase inhibitor is destroyed at the metaphase-to-anaphase transition by ubiquitin-dependent degradation. The relevant ubiquitin ligase, the anaphase-promoting complex/cyclosome, also targets cyclin B1, thereby causing inactivation of Cdk1 and mitotic exit. Although separase is essential, securin knock-out mice are surprisingly viable and fertile. Capitalizing on our previous finding that Cdk1-cyclin B1 can also bind and inhibit separase, we investigated whether this kinase might be suitable to maintain faithful timing and execution of anaphase in the absence of securin. We found that, similar to securin, Cdk1-cyclin B1 regulates separase in both a positive and negative manner. Although securin associates with nascent separase to co-translationally assist proper folding, Cdk1-cyclin B1 acts on native state separase. Upon entry into mitosis, Cdk1-cyclin B1-dependent phosphorylation of Ser-1126 renders separase prone to inactivation by aggregation/precipitation. Stable association of Cdk1-cyclin B1 with phosphorylated separase counteracts this tendency and stabilizes separase in an inhibited yet activatable state. These opposing effects are suited to prevent premature cleavage of cohesin in early mitosis while ensuring timely activation of separase by anaphase-promoting complex/cyclosome-dependent degradation of cyclin B1. Coupling sister chromatid separation with subsequent exit from mitosis by this simplified mode might have been the common scheme of mitotic control prior to the evolution of securin.
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Affiliation(s)
| | | | | | | | - Mathias Sprinzl
- Biochemistry, University of Bayreuth, 95440 Bayreuth, Germany
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12
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Abstract
The universal triggering event of eukaryotic chromosome segregation is cleavage of centromeric cohesin by separase. Prior to anaphase, most separase is kept inactive by association with securin. Protein phosphatase 2A (PP2A) constitutes another binding partner of human separase, but the functional relevance of this interaction has remained enigmatic. We demonstrate that PP2A stabilizes separase-associated securin by dephosphorylation, while phosphorylation of free securin enhances its polyubiquitylation by the ubiquitin ligase APC/C and proteasomal degradation. Changing PP2A substrate phosphorylation sites to alanines slows degradation of free securin, delays separase activation, lengthens early anaphase, and results in anaphase bridges and DNA damage. In contrast, separase-associated securin is destabilized by introduction of phosphorylation-mimetic aspartates or extinction of separase-associated PP2A activity. G2- or prometaphase-arrested cells suffer from unscheduled activation of separase when endogenous securin is replaced by aspartate-mutant securin. Thus, PP2A-dependent stabilization of separase-associated securin prevents precocious activation of separase during checkpoint-mediated arrests with basal APC/C activity and increases the abruptness and fidelity of sister chromatid separation in anaphase.
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Affiliation(s)
| | | | - Cuiping Pan
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Matthias Mann
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Olaf Stemmann
- Chair of Genetics, University of Bayreuth, Bayreuth, Germany
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Rattani A, Wolna M, Ploquin M, Helmhart W, Morrone S, Mayer B, Godwin J, Xu W, Stemmann O, Pendas A, Nasmyth K. Sgol2 provides a regulatory platform that coordinates essential cell cycle processes during meiosis I in oocytes. eLife 2013; 2:e01133. [PMID: 24192037 PMCID: PMC3816256 DOI: 10.7554/elife.01133] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Accurate chromosome segregation depends on coordination between cohesion resolution and kinetochore-microtubule interactions (K-fibers), a process regulated by the spindle assembly checkpoint (SAC). How these diverse processes are coordinated remains unclear. We show that in mammalian oocytes Shugoshin-like protein 2 (Sgol2) in addition to protecting cohesin, plays an important role in turning off the SAC, in promoting the congression and bi-orientation of bivalents on meiosis I spindles, in facilitating formation of K-fibers and in limiting bivalent stretching. Sgol2’s ability to protect cohesin depends on its interaction with PP2A, as is its ability to silence the SAC, with the latter being mediated by direct binding to Mad2. In contrast, its effect on bivalent stretching and K-fiber formation is independent of PP2A and mediated by recruitment of MCAK and inhibition of Aurora C kinase activity respectively. By virtue of its multiple interactions, Sgol2 links many of the processes essential for faithful chromosome segregation. DOI:http://dx.doi.org/10.7554/eLife.01133.001 Human reproductive cells—eggs and sperm—are produced through a process called meiosis. This means a ‘parent’ cell in the ovaries or testes undergoes two stages of cell division: it first divides into two cells, which then divide again to produce four ‘daughter’ cells. A crucial part of meiosis is ensuring that each daughter cell has half the number of chromosomes that the parent cell did. Before the first round of meiosis, the chromosomes in the parent cell are copied to produce enough chromosomes for the four daughter cells. The distribution of these chromosomes between the daughter cells is determined by the opposing forces acting on them. The pairs of identical chromosomes produced during the copying process are held together by a proteinaceous glue, while microtubules attached to a structure called the spindle—which has poles at opposite ends of the cell—try to pull these pairs of chromosomes apart. Rattani et al. now show that a protein called shugoshin-like 2 (Sgol2), which is involved in holding pairs of identical chromosomes together after the first round of division, has a bigger role than was previously realised. Sgol2 performs three other functions: it helps to align the chromosomes prior to division by, it is thought, facilitating the formation of the K-fibers that attach the microtubules to the chromosomes; it turns off the checkpoint that monitors the alignment of the chromosomes and the attachment of the microtubules; and it regulates a number of the enzymes involved in the process. The specific interactions that allow Sgol2 to perform these diverse functions in meiosis were also identified. Thus, Rattani et al. show that in linking so many essential processes throughout meiosis, Sgol2 appears to have a key, if not unique, role in determining the fate of chromosomes as cells divide. DOI:http://dx.doi.org/10.7554/eLife.01133.002
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Affiliation(s)
- Ahmed Rattani
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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14
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Buheitel J, Stemmann O. Prophase pathway-dependent removal of cohesin from human chromosomes requires opening of the Smc3-Scc1 gate. EMBO J 2013; 32:666-76. [PMID: 23361318 PMCID: PMC3590994 DOI: 10.1038/emboj.2013.7] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Accepted: 01/08/2013] [Indexed: 01/16/2023] Open
Abstract
Faithful transmission of chromosomes during eukaryotic cell division requires sister chromatids to be paired from their generation in S phase until their separation in M phase. Cohesion is mediated by the cohesin complex, whose Smc1, Smc3 and Scc1 subunits form a tripartite ring that entraps both DNA double strands. Whereas centromeric cohesin is removed in late metaphase by Scc1 cleavage, metazoan cohesin at chromosome arms is displaced already in prophase by proteolysis-independent signalling. Which of the three gates is triggered by the prophase pathway to open has remained enigmatic. Here, we show that displacement of human cohesin from early mitotic chromosomes requires dissociation of Smc3 from Scc1 but no opening of the other two gates. In contrast, loading of human cohesin onto chromatin in telophase occurs through the Smc1-Smc3 hinge. We propose that the use of differently regulated gates for loading and release facilitates unidirectionality of DNA's entry into and exit from the cohesin ring.
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15
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Touati SA, Cladière D, Lister LM, Leontiou I, Chambon JP, Rattani A, Böttger F, Stemmann O, Nasmyth K, Herbert M, Wassmann K. Cyclin A2 is required for sister chromatid segregation, but not separase control, in mouse oocyte meiosis. Cell Rep 2012; 2:1077-87. [PMID: 23122964 DOI: 10.1016/j.celrep.2012.10.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 09/04/2012] [Accepted: 10/02/2012] [Indexed: 11/18/2022] Open
Abstract
In meiosis, two specialized cell divisions allow the separation of paired chromosomes first, then of sister chromatids. Separase removes the cohesin complex holding sister chromatids together in a stepwise manner from chromosome arms in meiosis I, then from the centromere region in meiosis II. Using mouse oocytes, our study reveals that cyclin A2 promotes entry into meiosis, as well as an additional unexpected role; namely, its requirement for separase-dependent sister chromatid separation in meiosis II. Untimely cyclin A2-associated kinase activity in meiosis I leads to precocious sister separation, whereas inhibition of cyclin A2 in meiosis II prevents it. Accordingly, endogenous cyclin A is localized to kinetochores throughout meiosis II, but not in anaphase I. Additionally, we found that cyclin B1, but not cyclin A2, inhibits separase in meiosis I. These findings indicate that separase-dependent cohesin removal is differentially regulated by cyclin B1 and A2 in mammalian meiosis.
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Affiliation(s)
- Sandra A Touati
- UPMC Université Paris 06, UMR7622 Laboratoire de Biologie du Développement, 9 quai St. Bernard, Paris 75005, France
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16
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Schöckel L, Möckel M, Mayer B, Boos D, Stemmann O. Cleavage of cohesin rings coordinates the separation of centrioles and chromatids. Nat Cell Biol 2011; 13:966-72. [PMID: 21743463 DOI: 10.1038/ncb2280] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 05/13/2011] [Indexed: 12/28/2022]
Abstract
Cohesin pairs sister chromatids by forming a tripartite Scc1-Smc1-Smc3 ring around them. In mitosis, cohesin is removed from chromosome arms by the phosphorylation-dependent prophase pathway. Centromeric cohesin is protected by shugoshin 1 and protein phosphatase 2A (Sgo1-PP2A) and opened only in anaphase by separase-dependent cleavage of Scc1 (refs 4-6). Following chromosome segregation, centrioles loosen their tight orthogonal arrangement, which licenses later centrosome duplication in S phase. Although a role of separase in centriole disengagement has been reported, the molecular details of this process remain enigmatic. Here, we identify cohesin as a centriole-engagement factor. Both premature sister-chromatid separation and centriole disengagement are induced by ectopic activation of separase or depletion of Sgo1. These unscheduled events are suppressed by expression of non-cleavable Scc1 or inhibition of the prophase pathway. When endogenous Scc1 is replaced by artificially cleavable Scc1, the corresponding site-specific protease triggers centriole disengagement. Separation of centrioles can alternatively be induced by ectopic cleavage of an engineered Smc3. Thus, the chromosome and centrosome cycles exhibit extensive parallels and are coordinated with each other by dual use of the cohesin ring complex.
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17
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Orth M, Mayer B, Rehm K, Rothweiler U, Heidmann D, Holak TA, Stemmann O. Shugoshin is a Mad1/Cdc20-like interactor of Mad2. EMBO J 2011; 30:2868-80. [PMID: 21666598 DOI: 10.1038/emboj.2011.187] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 05/18/2011] [Indexed: 12/24/2022] Open
Abstract
Mammalian centromeric cohesin is protected from phosphorylation-dependent displacement in mitotic prophase by shugoshin-1 (Sgo1), while shugoshin-2 (Sgo2) protects cohesin from separase-dependent cleavage in meiosis I. In higher eukaryotes, progression and faithful execution of both mitosis and meiosis are controlled by the spindle assembly checkpoint, which delays anaphase onset until chromosomes have achieved proper attachment to microtubules. According to the so-called template model, Mad1-Mad2 complexes at unattached kinetochores instruct conformational change of soluble Mad2, thus catalysing Mad2 binding to its target Cdc20. Here, we show that human Sgo2, but not Sgo1, specifically interacts with Mad2 in a manner that strongly resembles the interactions of Mad2 with Mad1 or Cdc20. Sgo2 contains a Mad1/Cdc20-like Mad2-interaction motif and competes with Mad1 and Cdc20 for binding to Mad2. NMR and biochemical analyses show that shugoshin binding induces similar conformational changes in Mad2 as do Mad1 or Cdc20. Mad2 binding regulates fine-tuning of Sgo2's sub-centromeric localization. Mad2 binding is conserved in the only known Xenopus laevis shugoshin homologue and, compatible with a putative meiotic function, the interaction occurs in oocytes.
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Affiliation(s)
- Michael Orth
- Department of Genetics, University of Bayreuth, Bayreuth, Germany
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18
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Hörmanseder E, Tischer T, Heubes S, Stemmann O, Mayer TU. Non-proteolytic ubiquitylation counteracts the APC/C-inhibitory function of XErp1. EMBO Rep 2011; 12:436-43. [PMID: 21399619 DOI: 10.1038/embor.2011.32] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 02/01/2011] [Accepted: 02/03/2011] [Indexed: 11/09/2022] Open
Abstract
Mature Xenopus oocytes are arrested in meiosis by the activity of XErp1/Emi2, an inhibitor of the ubiquitin-ligase anaphase-promoting complex/cyclosome (APC/C). On fertilization, XErp1 is degraded, resulting in APC/C activation and the consequent degradation of cell-cycle regulators and exit from meiosis. In this study, we show that a modest increase in the activity of the ubiquitin-conjugating enzyme UbcX overrides the meiotic arrest in an APC/C-dependent reaction. Intriguingly, XErp1 remains stable in these conditions. We found that UbcX causes the ubiquitylation of XErp1, followed by its dissociation from the APC/C. Our data support the idea that ubiquitylation regulates the APC/C-inhibitory activity of XErp1.
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Affiliation(s)
- Eva Hörmanseder
- Department of Molecular Genetics, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany
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19
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Wang LHC, Mayer B, Stemmann O, Nigg EA. Centromere DNA decatenation depends on cohesin removal and is required for mammalian cell division. J Cell Sci 2010; 123:806-13. [PMID: 20144989 DOI: 10.1242/jcs.058255] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Sister chromatid cohesion is mediated by DNA catenation and proteinaceous cohesin complexes. The recent visualization of PICH (Plk1-interacting checkpoint helicase)-coated DNA threads in anaphase cells raises new questions as to the role of DNA catenation and its regulation in time and space. In the present study we show that persistent DNA catenation induced by inhibition of Topoisomerase-IIalpha can contribute to sister chromatid cohesion in the absence of cohesin complexes and that resolution of catenation is essential for abscission. Furthermore, we use an in vitro chromatid separation assay to investigate the temporal and functional relationship between cohesin removal and Topoisomerase-IIalpha-mediated decatenation. Our data suggest that centromere decatenation can occur only after separase activation and cohesin removal, providing a plausible explanation for the persistence of centromere threads after anaphase onset.
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Affiliation(s)
- Lily Hui-Ching Wang
- Department of Cell Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany.
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20
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Kudo NR, Anger M, Peters AHFM, Stemmann O, Theussl HC, Helmhart W, Kudo H, Heyting C, Nasmyth K. Role of cleavage by separase of the Rec8 kleisin subunit of cohesin during mammalian meiosis I. J Cell Sci 2009; 122:2686-98. [PMID: 19625504 PMCID: PMC2909317 DOI: 10.1242/jcs.035287] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2009] [Indexed: 01/02/2023] Open
Abstract
Proteolytic activity of separase is required for chiasma resolution during meiosis I in mouse oocytes. Rec8, the meiosis-specific alpha-kleisin subunit of cohesin, is a key target of separase in yeast. Is the equivalent protein also a target in mammals? We show here that separase cleaves mouse Rec8 at three positions in vitro but only when the latter is hyper-phosphorylated. Expression of a Rec8 variant (Rec8-N) that cannot be cleaved in vitro at these sites causes sterility in male mice. Their seminiferous tubules lack a normal complement of 2 C secondary spermatocytes and 1 C spermatids and contain instead a high proportion of cells with enlarged nuclei. Chromosome spreads reveal that Rec8-N expression has no effect in primary spermatocytes but produces secondary spermatocytes and spermatids with a 4 C DNA content, suggesting that the first and possibly also the second meiotic division is abolished. Expression of Rec8-N in oocytes causes chromosome segregation to be asynchronous and delays its completion by 2-3 hours during anaphase I, probably due to inefficient proteolysis of Rec8-N by separase. Despite this effect, chromosome segregation must be quite accurate as Rec8-N does not greatly reduce female fertility. Our data is consistent with the notion that Rec8 cleavage is important and probably crucial for the resolution of chiasmata in males and females.
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Affiliation(s)
- Nobuaki R. Kudo
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
- Institute of Reproductive and Developmental Biology, Imperial College London, London W12 0NN, UK
| | - Martin Anger
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
- University of Oxford, Department of Biochemistry, Oxford OX1 3QU, UK
| | - Antoine H. F. M. Peters
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Olaf Stemmann
- Department of Molecular Cell Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany
| | | | - Wolfgang Helmhart
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
- University of Oxford, Department of Biochemistry, Oxford OX1 3QU, UK
| | - Hiromi Kudo
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
| | - Christa Heyting
- Molecular Genetics Group, Wageningen University, NL-6703 BD Wageningen, The Netherlands
| | - Kim Nasmyth
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
- University of Oxford, Department of Biochemistry, Oxford OX1 3QU, UK
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21
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Daub H, Olsen JV, Bairlein M, Gnad F, Oppermann FS, Körner R, Greff Z, Kéri G, Stemmann O, Mann M. Kinase-selective enrichment enables quantitative phosphoproteomics of the kinome across the cell cycle. Mol Cell 2008; 31:438-48. [PMID: 18691976 DOI: 10.1016/j.molcel.2008.07.007] [Citation(s) in RCA: 478] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 04/24/2008] [Accepted: 07/18/2008] [Indexed: 12/15/2022]
Abstract
Protein kinases are pivotal regulators of cell signaling that modulate each other's functions and activities through site-specific phosphorylation events. These key regulatory modifications have not been studied comprehensively, because low cellular abundance of kinases has resulted in their underrepresentation in previous phosphoproteome studies. Here, we combine kinase-selective affinity purification with quantitative mass spectrometry to analyze the cell-cycle regulation of protein kinases. This proteomics approach enabled us to quantify 219 protein kinases from S and M phase-arrested human cancer cells. We identified more than 1000 phosphorylation sites on protein kinases. Intriguingly, half of all kinase phosphopeptides were upregulated in mitosis. Our data reveal numerous unknown M phase-induced phosphorylation sites on kinases with established mitotic functions. We also find potential phosphorylation networks involving many protein kinases not previously implicated in mitotic progression. These results provide a vastly extended knowledge base for functional studies on kinases and their regulation through site-specific phosphorylation.
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Affiliation(s)
- Henrik Daub
- Cell Signaling Group, Department of Molecular Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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22
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Rothweiler U, Czarna A, Weber L, Popowicz GM, Brongel K, Kowalska K, Orth M, Stemmann O, Holak TA. NMR Screening for Lead Compounds Using Tryptophan-Mutated Proteins. J Med Chem 2008; 51:5035-42. [DOI: 10.1021/jm8002813] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Ulli Rothweiler
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Anna Czarna
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Lutz Weber
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Grzegorz M. Popowicz
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Kinga Brongel
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Kaja Kowalska
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Michael Orth
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Olaf Stemmann
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
| | - Tad A. Holak
- Max Planck Institute for Biochemistry, D-82152 Martinsried, Germany, NexusPharma Inc., 253-13 Summit Square Center, Langhorne, Pennsylvania 19047-1098
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23
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Nabti I, Reis A, Levasseur M, Stemmann O, Jones KT. Securin and not CDK1/cyclin B1 regulates sister chromatid disjunction during meiosis II in mouse eggs. Dev Biol 2008; 321:379-86. [PMID: 18639540 DOI: 10.1016/j.ydbio.2008.06.036] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 06/23/2008] [Accepted: 06/25/2008] [Indexed: 11/17/2022]
Abstract
Mammalian eggs remain arrested at metaphase of the second meiotic division (metII) for an indeterminate time before fertilization. During this period, which can last several hours, the continued attachment of sister chromatids is thought to be achieved by inhibition of the protease separase. Separase is known to be inhibited by binding either securin or Maturation (M-Phase)-Promoting Factor, a heterodimer of CDK1/cyclin B1. However, the relative contribution of securin and CDK/cyclin B1 to sister chromatid attachment during metII arrest has not been assessed. Although there are conditions in which either CDK1/cyclinB1 activity or securin can prevent sister chromatid disjunction, principally by overexpression of non-degradable cyclin B1 or securin, we find here that separase activity is primarily regulated by securin and not CDK1/cyclin B1. Thus the CDK1 inhibitor roscovitine and an antibody we designed to block the interaction of CDK1/cyclin B1 with separase, both failed to induce sister disjunction. In contrast, securin morpholino knockdown specifically induced loss of sister attachment, that could be restored by securin cRNA rescue. During metII arrest separase appears primarily regulated by securin binding, not CDK1/cyclin B1.
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Affiliation(s)
- Ibtissem Nabti
- Institute for Cell and Molecular Biosciences, The Medical School, Framlington Place, University of Newcastle, Newcastle, NE2 4HH, UK
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24
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Boos D, Kuffer C, Lenobel R, Körner R, Stemmann O. Phosphorylation-dependent binding of cyclin B1 to a Cdc6-like domain of human separase. J Biol Chem 2007; 283:816-23. [PMID: 17974570 DOI: 10.1074/jbc.m706748200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sister chromatids are held together by the ring-shaped cohesin complex, which likely entraps both DNA-double strands in its middle. This tie is resolved in anaphase when separase, a giant protease, becomes active and cleaves the kleisin subunit of cohesin. Premature activation of separase and, hence, chromosome missegregation are prevented by at least two inhibitory mechanisms. Although securin has long been appreciated as a direct inhibitor of separase, surprisingly its loss has basically no phenotype in mammals. Phosphorylation-dependent binding of Cdk1 constitutes an alternative way to inhibit vertebrate separase. Its importance is illustrated by the premature loss of cohesion when Cdk1-resistant separase is expressed in mammalian cells without or with limiting amounts of securin. Here, we demonstrate that crucial inhibitory phosphorylations occur within a region of human separase that is also shown to make direct contact with the cyclin B1 subunit of Cdk1. This region exhibits a weak homology to Saccharomyces cerevisiae Cdc6 of similar Cdk1 binding behavior, thereby establishing phosphoserine/threonine-mediated binding of partners as a conserved characteristic of B-type cyclins. In contrast to the Cdc6-like domain, the previously identified serine 1126 phosphorylation is fully dispensable for Cdk1 binding to separase fragments. This suggests that despite its in vivo relevance, it promotes complex formation indirectly, possibly by inducing a conformational change in full-length separase.
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Affiliation(s)
- Dominik Boos
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany
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25
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Abstract
The onset of anaphase is triggered by the activation of a site-specific protease called separase. Separase cleaves the chromosomal cohesins holding the duplicated sister chromatids together, allowing sisters to simultaneously separate and segregate to opposite ends of the cell before division. Activated separase cleaves not only cohesin, but also itself; however, the biological significance of separase self-cleavage has remained elusive. Before anaphase, separase is inhibited by at least two mechanisms. The first involves the binding of securin, whereas the second requires the phosphorylation-dependent binding of cyclin-dependent kinase 1 (Cdk1)/cyclin B1. Because securin and Cdk1/cyclin B1 interact with separase in a mutually exclusive manner, the degradation of both these inhibitors plays an important role in activating separase at anaphase. Here we identify a new separase interacting partner, a specific subtype of the heterotrimeric protein phosphatase 2A (PP2A). PP2A associates with separase through the B' (B56) regulatory subunit and does so independently of securin and cyclin B1 binding. The association of PP2A with separase requires a 55-amino acid domain closely juxtaposed to separase autocleavage sites. Strikingly, mutation of these cleavage sites increases PP2A binding, suggesting that separase cleavage disrupts the interaction of PP2A with separase. Furthermore, expression of a non-cleavable separase, but not a non-cleavable mutant that cannot bind PP2A, causes a premature loss of centromeric cohesion. Together these observations provide a new mechanistic insight into a physiological function for separase self-cleavage.
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Affiliation(s)
- Andrew J Holland
- Faculty of Life Sciences, Michael Smith Building, Oxford Road, University of Manchester, Manchester M13 9PT, United Kingdom
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26
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Abstract
The highly abundant AAA-ATPase p97 is required for diverse cellular processes, of which ER-associated protein degradation (ERAD) is understood best. Previously, a new role of p97 in spindle disassembly at the end of mitosis has been reported. However, we show that neither addition of dominant-negative p97 mutants nor depletion of crucial p97 adaptors impairs transition of meiotic spindles into interphase arrays of microtubules. The dominant-negative approach is validated by inhibition of ERAD, which we reconstitute for the first time in the powerful biochemical system of Xenopus egg extracts. The role of p97 in spindle disassembly during meiotic exit should therefore be reconsidered.
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Affiliation(s)
- Simone Heubes
- Department of Molecular Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
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27
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Gorr IH, Reis A, Boos D, Wühr M, Madgwick S, Jones KT, Stemmann O. Essential CDK1-inhibitory role for separase during meiosis I in vertebrate oocytes. Nat Cell Biol 2006; 8:1035-7. [PMID: 16906143 PMCID: PMC2435240 DOI: 10.1038/ncb1467] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Accepted: 07/24/2006] [Indexed: 11/08/2022]
Abstract
Separase not only triggers anaphase of meiosis I by proteolytic cleavage of cohesin on chromosome arms, but in vitro vertebrate separase also acts as a direct inhibitor of cyclin-dependent kinase 1 (Cdk1) on liberation from the inhibitory protein, securin. Blocking separase-Cdk1 complex formation by microinjection of anti-separase antibodies prevents polar-body extrusion in vertebrate oocytes. Importantly, proper meiotic maturation is rescued by chemical inhibition of Cdk1 or expression of Cdk1-binding separase fragments lacking cohesin-cleaving activity.
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Affiliation(s)
- Ingo H. Gorr
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Alexandra Reis
- Institute for Cell and Molecular Biosciences, The Medical School, Framlington Place, University of Newcastle-upon-Tyne, Newcastle, NE2 4HH, UK
| | - Dominik Boos
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Martin Wühr
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Suzanne Madgwick
- Institute for Cell and Molecular Biosciences, The Medical School, Framlington Place, University of Newcastle-upon-Tyne, Newcastle, NE2 4HH, UK
| | - Keith T. Jones
- Institute for Cell and Molecular Biosciences, The Medical School, Framlington Place, University of Newcastle-upon-Tyne, Newcastle, NE2 4HH, UK
- Correspondence should be addressed to KTJ and OS (, )
| | - Olaf Stemmann
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
- Correspondence should be addressed to KTJ and OS (, )
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28
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Abstract
Chromosome segregation in mitosis and meiosis is triggered by activation of a large protease, separase. While it has been known for some time that the anaphase inhibitor securin regulates separase activity recent work shows that this is only half the story. In vertebrates Cdk1-dependent inhibition of separase represents a second, securin-independent branch of anaphase regulation. Furthermore, an unanticipated ability of separase to inhibit Cdk1 suggests additional, nonproteolytic functions of separase.
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Affiliation(s)
- Olaf Stemmann
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany.
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29
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Abstract
Abnormalities of chromosome number are frequently observed in cancers. The mechanisms regulating chromosome segregation in human cells are therefore of great interest. Recently it has been reported that human cells without an hSecurin gene lose chromosomes at a high frequency. Here we show that, after hSecurin knockout through homologous recombination, chromosome losses are only a short, transient effect. After a few passages hSecurin(-/-) cells became chromosomally stable and executed mitoses normally. This was unexpected, as the securin loss resulted in a persisting reduction of the sister-separating protease separase and inefficient cleavage of the cohesin subunit Scc1. Our data demonstrate that securin is dispensable for chromosomal stability in human cells. We propose that human cells possess efficient mechanisms to compensate for the loss of genes involved in chromosome segregation.
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Affiliation(s)
- Katrin Pfleghaar
- 1Institute of Human Genetics, Technical University Munich, Munich, Germany
- 2Institute of Human Genetics, GSF National Research Center for Environment and Health, Neuherberg, Germany
| | - Simone Heubes
- 3Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | | | - Olaf Stemmann
- 3Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Michael R Speicher
- 1Institute of Human Genetics, Technical University Munich, Munich, Germany
- 2Institute of Human Genetics, GSF National Research Center for Environment and Health, Neuherberg, Germany
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30
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Gorr IH, Boos D, Stemmann O. Mutual inhibition of separase and Cdk1 by two-step complex formation. Mol Cell 2005; 19:135-41. [PMID: 15989971 DOI: 10.1016/j.molcel.2005.05.022] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2005] [Revised: 04/28/2005] [Accepted: 05/25/2005] [Indexed: 11/28/2022]
Abstract
Stable maintenance of genetic information requires chromosome segregation to occur with high accuracy. Anaphase is triggered when ring-shaped cohesin is cleaved by separase, a protease regulated by association with its inhibitor securin. Dispensability of vertebrate securin strongly suggests additional means of separase regulation. Indeed, sister chromatid separation but not securin degradation is inhibited by constitutively active cyclin-dependent kinase 1 (Cdk1) and can be rescued solely by preventing phosphorylation of separase. We demonstrate that Cdk1-dependent phosphorylation of separase is not sufficient for inhibition. In a second step, Cdk1 stably binds phosphorylated separase via its regulatory cyclin B1 subunit. Complex formation results in inhibition of both protease and kinase, and we show that vertebrate separase is a direct inhibitor of Cdk1. This unanticipated function of separase is negatively regulated by securin but independent of separase's proteolytic activity.
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Affiliation(s)
- Ingo H Gorr
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
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31
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Viadiu H, Stemmann O, Kirschner MW, Walz T. Domain structure of separase and its binding to securin as determined by EM. Nat Struct Mol Biol 2005; 12:552-3. [PMID: 15880121 DOI: 10.1038/nsmb935] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Accepted: 04/13/2005] [Indexed: 11/08/2022]
Abstract
After the degradation of its inhibitor securin, separase initiates chromosome segregation during the metaphase-to-anaphase transition by cleaving cohesin. Here we present a density map at a resolution of 25 A of negatively stained separase-securin complex. Based on labeling data and sequence analysis, we propose a model for the structure of separase, consisting of 26 ARM repeats, an unstructured region of 280 residues and two caspase-like domains, with securin binding to the ARM repeats.
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Affiliation(s)
- Hector Viadiu
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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32
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Abstract
Cleavage of the ring-like cohesin complex by separase triggers segregation of sister chromatids in anaphase. This simplistic model has recently been extended by exciting discoveries on three levels: regulation of anaphase by posttranslational modifications and the cohesin protector shugoshin; non-proteolytic roles of separase; and cohesin-independent linkage of sister chromatids.
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Affiliation(s)
- Olaf Stemmann
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany.
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33
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Abstract
Binding of CBF3, a protein complex consisting of Ndc10p, Cep3p, Ctf13p, and Skp1p, to the centromere DNA nucleates kinetochore formation in budding yeast. Here, we investigate how the Ctf13p/Skp1p complex becomes competent to form the CBF3-centromere DNA complex. As revealed by mass spectrometry, Ctf13p and Skp1p carry two and four phosphate groups, respectively. Complete dephosphorylation of Ctf13p and Skp1p does not interfere with the formation of CBF3-centromere DNA complexes in vitro. Furthermore, deletion of corresponding phosphorylation sites results in viable cells. Thus, in contrast to the current view, phosphorylation of Ctf13p and Skp1p is not essential for the formation of CBF3-centromere DNA complexes. Instead, the formation of active Ctf13p/Skp1p requires Hsp90. Several lines of evidence support this conclusion: activation of heterologous Ctf13p/Skp1p by reticulocyte lysate is inhibited by geldanamycin and Hsp90 depletion. skp1 mutants exhibit growth defects on media containing geldanamycin. A skp1 mutation together with Hsp90 mutations exhibits synthetic lethality. An Hsp90 mutant contains decreased levels of active Ctf13p/Skp1p.
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Affiliation(s)
- Olaf Stemmann
- Biochemie-Zentrum, Ruprecht-Karls Universität, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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34
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Abstract
Separation of sister chromatids in anaphase is mediated by separase, an endopeptidase that cleaves the chromosomal cohesin SCC1. Separase is inhibited by securin, which is degraded at the metaphase-anaphase transition. Using Xenopus egg extracts, we demonstrate that high CDC2 activity inhibits anaphase but not securin degradation. We show that separase is kept inactive under these conditions by a mechanism independent of binding to securin. Mutation of a single phosphorylation site on separase relieves the inhibition and rescues chromatid separation in extracts with high CDC2 activity. Using quantitative mass spectrometry, we show that, in intact cells, there is complete phosphorylation of this site in metaphase and significant dephosphorylation in anaphase. We propose that separase activation at the metaphase-anaphase transition requires the removal of both securin and an inhibitory phosphate.
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Affiliation(s)
- O Stemmann
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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35
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Ortiz J, Stemmann O, Rank S, Lechner J. A putative protein complex consisting of Ctf19, Mcm21, and Okp1 represents a missing link in the budding yeast kinetochore. Genes Dev 1999; 13:1140-55. [PMID: 10323865 PMCID: PMC316948 DOI: 10.1101/gad.13.9.1140] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We have established a one-hybrid screen that allows the in vivo localization of proteins at a functional Saccharomyces cerevisiae centromere. Applying this screen we have identified three proteins-Ctf19, Mcm21, and the product of an unspecified open reading frame that we named Okp1-as components of the budding yeast centromere. Ctf19, Mcm21, and Okp1 most likely form a protein complex that links CBF3, a protein complex directly associated with the CDE III element of the centromere DNA, with further components of the budding yeast centromere, Cbf1, Mif2, and Cse4. We demonstrate that the CDE III element is essential and sufficient to localize the established protein network to the centromere and propose that the interaction of the CDE II element with the CDE III localized protein complex facilitates a protein-DNA conformation that evokes the active centromere.
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Affiliation(s)
- J Ortiz
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, 93040 Regensburg, Germany
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36
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Pietrasanta LI, Thrower D, Hsieh W, Rao S, Stemmann O, Lechner J, Carbon J, Hansma H. Probing the Saccharomyces cerevisiae centromeric DNA (CEN DNA)-binding factor 3 (CBF3) kinetochore complex by using atomic force microscopy. Proc Natl Acad Sci U S A 1999; 96:3757-62. [PMID: 10097110 PMCID: PMC22367 DOI: 10.1073/pnas.96.7.3757] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Yeast centromeric DNA (CEN DNA) binding factor 3 (CBF3) is a multisubunit protein complex that binds to the essential CDEIII element in CEN DNA. The four CBF3 proteins are required for accurate chromosome segregation and are considered to be core components of the yeast kinetochore. We have examined the structure of the CBF3-CEN DNA complex by atomic force microscopy. Assembly of CBF3-CEN DNA complexes was performed by combining purified CBF3 proteins with a DNA fragment that includes the CEN region from yeast chromosome III. Atomic force microscopy images showed DNA molecules with attached globular bodies. The contour length of the DNA containing the complex is approximately 9% shorter than the DNA alone, suggesting some winding of DNA within the complex. The measured location of the single binding site indicates that the complex is located asymmetrically to the right of CDEIII extending away from CDEI and CDEII, which is consistent with previous data. The CEN DNA is bent approximately 55 degrees at the site of complex formation. A significant fraction of the complexes are linked in pairs, showing three to four DNA arms, with molecular volumes approximately three times the mean volumes of two-armed complexes. These multi-armed complexes indicate that CBF3 can bind two DNA molecules together in vitro and, thus, may be involved in holding together chromatid pairs during mitosis.
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Affiliation(s)
- L I Pietrasanta
- Department of Physics, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA
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37
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Stemmann O, Lechner J. The Saccharomyces cerevisiae kinetochore contains a cyclin-CDK complexing homologue, as identified by in vitro reconstitution. EMBO J 1996. [DOI: 10.1002/j.1460-2075.1996.tb00730.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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38
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Stemmann O, Lechner J. The Saccharomyces cerevisiae kinetochore contains a cyclin-CDK complexing homologue, as identified by in vitro reconstitution. EMBO J 1996; 15:3611-20. [PMID: 8670864 PMCID: PMC451974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We have developed methods to reconstitute the centromere DNA (CEN)-bound Saccharomyces cerevisiae kinetochore complex, CBF3, from isolated CBF3 components in vitro. This revealed that cooperation of at least three CBF3 components is imperatively required to form an activity that specifically binds to the centromere DNA in vitro. Two of the CBF3 proteins, Cbf3a and Cbf3b, that were used in the reconstitution were obtained from heterologous systems. In contrast, Cbf3c, the third CBF3 component known, had to be purified from S. cerevisiae to obtain a Cbf3c preparation that was competent to reconstitute the CBF3-CEN complex in combination with Cbf3a and Cbf3b. This led to the identification of a 29 kDa protein that co-purified with Cbf3c. The 29 kDa protein was shown to be a fourth component of CBF3 and therefore was named Cbf3d. Analysing the Cbf3d gene revealed that Cbf3d exhibits strong homology to p19SKP1, a human protein that is part of active cyclin A-CDK2 complexes. Therefore, Cbf3d is the only CBF3 protein that has a known homologue in higher eukaryotes and may provide the anchor that directs cell cycle-regulated proteins to the kinetochore.
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Affiliation(s)
- O Stemmann
- Institut für Biochemie, Universität Regensburg, Germany
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39
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Brikun I, Suziedelis K, Stemmann O, Zhong R, Alikhanian L, Linkova E, Mironov A, Berg DE. Analysis of CRP-CytR interactions at the Escherichia coli udp promoter. J Bacteriol 1996; 178:1614-22. [PMID: 8626289 PMCID: PMC177846 DOI: 10.1128/jb.178.6.1614-1622.1996] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Multiprotein complexes regulate the transcription of certain bacterial genes in a sensitive, physiologically responsive manner. In particular, the transcription of genes needed for utilization of nucleosides in Escherichia coli is regulated by a repressor protein, CytR, in concert with the cyclic AMP (cAMP) activated form of cAMP receptor protein (CRP). We studied this regulation by selecting and characterizing spontaneous constitutive mutations in the promoter of the udp (uridine phosphorylase) gene, one of the genes most strongly regulated by CytR. We found deletions, duplications, and point mutations that affect key regulatory sites in the udp promoter, insertion sequence element insertions that activated cryptic internal promoters or provided new promoters, and large duplications that may have increased expression by udp gene amplification. Unusual duplications and deletions that resulted in constitutive udp expression that depended on the presence of CytR were also found. Our results support the model in which repression normally involves the binding of CytR to cAMP-CRP to form a complex which binds to specific sites in the udp promoter, without direct interaction between CytR protein and a specific operator DNA sequence, and in which induction by specific inducer cytidine involves dissociation of CytR from cAMP-CRP and the RNA polymerase interaction with cAMP-CRP bound to a site upstream of then transcription start point. The stimulation of udp expression by CytR in certain mutants may reflect its stabilization of cAMP-CRP binding to target DNA and illustrates that only modest evolutionary changes could allow particular multiprotein complexes to serve as either repressors or transcriptional activators.
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Affiliation(s)
- I Brikun
- Department of Molecular Microbiology, Washington University Medical School, St. Louis, Missouri 63110, USA
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