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Zablowsky N, Farack L, Rofall S, Kramer J, Meyer H, Nguyen D, Ulrich AKC, Bader B, Steigemann P. High Throughput FISH Screening Identifies Small Molecules That Modulate Oncogenic lncRNA MALAT1 via GSK3B and hnRNPs. Noncoding RNA 2023; 9:ncrna9010002. [PMID: 36649031 PMCID: PMC9844399 DOI: 10.3390/ncrna9010002] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 12/12/2022] [Accepted: 12/20/2022] [Indexed: 01/06/2023] Open
Abstract
Traditionally, small molecule-based drug discovery has mainly focused on proteins as the drug target. Opening RNA as an additional target space for small molecules offers the possibility to therapeutically modulate disease-driving non-coding RNA targets as well as mRNA of otherwise undruggable protein targets. MALAT1 is a highly conserved long-noncoding RNA whose overexpression correlates with poor overall patient survival in some cancers. We report here a fluorescence in-situ hybridization-based high-content imaging screen to identify small molecules that modulate the oncogenic lncRNA MALAT1 in a cellular setting. From a library of FDA approved drugs and known bioactive molecules, we identified two compounds, including Niclosamide, an FDA-approved drug, that lead to a rapid decrease of MALAT1 nuclear levels with good potency. Mode-of-action studies suggest a novel cellular regulatory pathway that impacts MALAT1 lncRNA nuclear levels by GSK3B activation and the involvement of the RNA modulating family of heterogenous nuclear ribonucleoproteins (hnRNPs). This study is the basis for the identification of novel targets that lead to a reduction of the oncogenic lncRNA MALAT1 in a cancer setting.
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Peirsman A, Blondeel E, Ahmed T, Anckaert J, Audenaert D, Boterberg T, Buzas K, Carragher N, Castellani G, Castro F, Dangles-Marie V, Dawson J, De Tullio P, De Vlieghere E, Dedeyne S, Depypere H, Diosdi A, Dmitriev RI, Dolznig H, Fischer S, Gespach C, Goossens V, Heino J, Hendrix A, Horvath P, Kunz-Schughart LA, Maes S, Mangodt C, Mestdagh P, Michlíková S, Oliveira MJ, Pampaloni F, Piccinini F, Pinheiro C, Rahn J, Robbins SM, Siljamäki E, Steigemann P, Sys G, Takayama S, Tesei A, Tulkens J, Van Waeyenberge M, Vandesompele J, Wagemans G, Weindorfer C, Yigit N, Zablowsky N, Zanoni M, Blondeel P, De Wever O. MISpheroID: a knowledgebase and transparency tool for minimum information in spheroid identity. Nat Methods 2021; 18:1294-1303. [PMID: 34725485 PMCID: PMC8566242 DOI: 10.1038/s41592-021-01291-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 09/09/2021] [Indexed: 01/21/2023]
Abstract
Spheroids are three-dimensional cellular models with widespread basic and translational application across academia and industry. However, methodological transparency and guidelines for spheroid research have not yet been established. The MISpheroID Consortium developed a crowdsourcing knowledgebase that assembles the experimental parameters of 3,058 published spheroid-related experiments. Interrogation of this knowledgebase identified heterogeneity in the methodological setup of spheroids. Empirical evaluation and interlaboratory validation of selected variations in spheroid methodology revealed diverse impacts on spheroid metrics. To facilitate interpretation, stimulate transparency and increase awareness, the Consortium defines the MISpheroID string, a minimum set of experimental parameters required to report spheroid research. Thus, MISpheroID combines a valuable resource and a tool for three-dimensional cellular models to mine experimental parameters and to improve reproducibility.
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Affiliation(s)
- Arne Peirsman
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
- Plastic, Reconstructive and Aesthetic Surgery, Ghent University Hospital, Ghent, Belgium
| | - Eva Blondeel
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Tasdiq Ahmed
- Wallace H Coulter Department of Biomedical Engineering and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology and Emory School of Medicine, Atlanta, GA, USA
| | - Jasper Anckaert
- OncoRNALab, Cancer Research Institute, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Dominique Audenaert
- VIB Screening Core and Ghent University Expertise Centre for Bioassay Development and Screening (C-BIOS-VIB), Ghent University, Ghent, Belgium
| | - Tom Boterberg
- Department of Radiation Oncology, Ghent University Hospital, Ghent, Belgium
| | - Krisztina Buzas
- Department of Immunology, University of Szeged, Faculty of Medicine-Faculty of Science and Informatics, Szeged, Hungary
| | - Neil Carragher
- Institute of Genetics and Cancer, Cancer Research UK Edinburgh Centre, University of Edinburgh, Edinburgh, UK
| | - Gastone Castellani
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy
| | - Flávia Castro
- i3S - Institute for Research and Innovation in Health, University of Porto, Porto, Portugal
| | - Virginie Dangles-Marie
- Translational Research Department, Institut Curie, PSL Research University, and Faculty of Pharmacy, Paris, France
- Faculty of Pharmacy, Université Paris Descartes, Paris, France
| | - John Dawson
- Institute of Genetics and Cancer, Cancer Research UK Edinburgh Centre, University of Edinburgh, Edinburgh, UK
| | - Pascal De Tullio
- Center for Interdisciplinary Research on Medicines (CIRM), Metabolomics Group, Université de Liège, Liège, Belgium
| | - Elly De Vlieghere
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Sándor Dedeyne
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Herman Depypere
- Menopause and Breast Clinic, Ghent University Hospital, Ghent, Belgium
| | - Akos Diosdi
- Synthetic and Systems Biology Unit, Hungarian Academy of Sciences, Biological Research Center (BRC), Szeged, Hungary
| | - Ruslan I Dmitriev
- Tissue Engineering and Biomaterials Group, Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Helmut Dolznig
- Institute of Medical Genetics, Medical University of Vienna, Vienna, Austria
| | - Suzanne Fischer
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Christian Gespach
- INSERM U938 Hospital Saint-Antoine Research Center CRSA, Team Céline Prunier, TGFbeta Signaling in Cellular Plasticity and Cancer, Sorbonne University, Paris, France
| | - Vera Goossens
- VIB Screening Core and Ghent University Expertise Centre for Bioassay Development and Screening (C-BIOS-VIB), Ghent University, Ghent, Belgium
| | - Jyrki Heino
- Department of Life Technologies, University of Turku, Turku, Finland
| | - An Hendrix
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Peter Horvath
- Synthetic and Systems Biology Unit, Hungarian Academy of Sciences, Biological Research Center (BRC), Szeged, Hungary
| | - Leoni A Kunz-Schughart
- OncoRay - National Center for Radiation Research in Oncology, University Hospital Carl Gustav Carus Dresden, Carl Gustav Carus Faculty of Medicine at TU Dresden, and Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - Sebastiaan Maes
- Plastic, Reconstructive and Aesthetic Surgery, Ghent University Hospital, Ghent, Belgium
| | - Christophe Mangodt
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Pieter Mestdagh
- OncoRNALab, Cancer Research Institute, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Soňa Michlíková
- OncoRay - National Center for Radiation Research in Oncology, University Hospital Carl Gustav Carus Dresden, Carl Gustav Carus Faculty of Medicine at TU Dresden, and Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - Maria José Oliveira
- i3S - Institute for Research and Innovation in Health, University of Porto, Porto, Portugal
| | - Francesco Pampaloni
- Physical Biology Group, Buchmann Institute for Molecular Life Sciences (BMLS), Goethe Universität Frankfurt am Main, Frankfurt am Main, Germany
| | - Filippo Piccinini
- IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) 'Dino Amadori', Meldola, Italy
| | - Cláudio Pinheiro
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Jennifer Rahn
- Departments of Oncology and Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Stephen M Robbins
- Departments of Oncology and Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Elina Siljamäki
- Department of Life Technologies, University of Turku, Turku, Finland
| | | | - Gwen Sys
- Department of Orthopedics and Traumatology, Ghent University Hospital, Ghent University, Ghent, Belgium
| | - Shuichi Takayama
- Wallace H Coulter Department of Biomedical Engineering and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology and Emory School of Medicine, Atlanta, GA, USA
| | - Anna Tesei
- IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) 'Dino Amadori', Meldola, Italy
| | - Joeri Tulkens
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | | | - Jo Vandesompele
- OncoRNALab, Cancer Research Institute, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Glenn Wagemans
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Claudia Weindorfer
- Institute of Medical Genetics, Medical University of Vienna, Vienna, Austria
| | - Nurten Yigit
- OncoRNALab, Cancer Research Institute, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | | | - Michele Zanoni
- IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) 'Dino Amadori', Meldola, Italy
| | - Phillip Blondeel
- Plastic, Reconstructive and Aesthetic Surgery, Ghent University Hospital, Ghent, Belgium
| | - Olivier De Wever
- Laboratory of Experimental Cancer Research, Cancer Research Institute, Ghent, Belgium.
- Department of Human Structure and Repair, Ghent University, Ghent, Belgium.
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Lemos C, Schulze L, Weiske J, Meyer H, Braeuer N, Barak N, Eberspächer U, Werbeck N, Stresemann C, Lange M, Lesche R, Zablowsky N, Juenemann K, Kamburov A, Luh LM, Leissing TM, Mortier J, Steckel M, Steuber H, Eis K, Eheim A, Steigemann P. Identification of Small Molecules that Modulate Mutant p53 Condensation. iScience 2020; 23:101517. [PMID: 32927263 PMCID: PMC7495113 DOI: 10.1016/j.isci.2020.101517] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [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] [Received: 04/30/2020] [Revised: 07/27/2020] [Accepted: 08/26/2020] [Indexed: 02/07/2023] Open
Abstract
Structural mutants of p53 induce global p53 protein destabilization and misfolding, followed by p53 protein aggregation. First evidence indicates that p53 can be part of protein condensates and that p53 aggregation potentially transitions through a condensate-like state. We show condensate-like states of fluorescently labeled structural mutant p53 in the nucleus of living cancer cells. We furthermore identified small molecule compounds that interact with the p53 protein and lead to dissolution of p53 structural mutant condensates. The same compounds lead to condensation of a fluorescently tagged p53 DNA-binding mutant, indicating that the identified compounds differentially alter p53 condensation behavior depending on the type of p53 mutation. In contrast to p53 aggregation inhibitors, these compounds are active on p53 condensates and do not lead to mutant p53 reactivation. Taken together our study provides evidence for structural mutant p53 condensation in living cells and tools to modulate this process.
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Affiliation(s)
- Clara Lemos
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Luise Schulze
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Joerg Weiske
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Hanna Meyer
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Nico Braeuer
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Naomi Barak
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Uwe Eberspächer
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Nicolas Werbeck
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Carlo Stresemann
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Martin Lange
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Ralf Lesche
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Nina Zablowsky
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Katrin Juenemann
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Atanas Kamburov
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Laura Martina Luh
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Thomas Markus Leissing
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Jeremie Mortier
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Michael Steckel
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Holger Steuber
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Knut Eis
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Ashley Eheim
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
| | - Patrick Steigemann
- Bayer AG Research and Development, Pharmaceuticals, Müllerstr. 178, 13342 Berlin, Germany
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4
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Mortier J, Friberg A, Badock V, Moosmayer D, Schroeder J, Steigemann P, Siegel F, Gradl S, Bauser M, Hillig RC, Briem H, Eis K, Bader B, Nguyen D, Christ CD. Front Cover: Computationally Empowered Workflow Identifies Novel Covalent Allosteric Binders for KRAS
G12C
(ChemMedChem 10/2020). ChemMedChem 2020. [DOI: 10.1002/cmdc.202000297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Jérémie Mortier
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Anders Friberg
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Volker Badock
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Dieter Moosmayer
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Jens Schroeder
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Patrick Steigemann
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Franziska Siegel
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Stefan Gradl
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Marcus Bauser
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Roman C. Hillig
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Hans Briem
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Knut Eis
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Benjamin Bader
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Duy Nguyen
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
| | - Clara D. Christ
- Bayer AGResearch & Development, Pharmaceuticals Müllerstrasse 178 13342 Berlin Germany
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5
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Mortier J, Friberg A, Badock V, Moosmayer D, Schroeder J, Steigemann P, Siegel F, Gradl S, Bauser M, Hillig RC, Briem H, Eis K, Bader B, Nguyen D, Christ CD. Computationally Empowered Workflow Identifies Novel Covalent Allosteric Binders for KRAS G12C. ChemMedChem 2020; 15:827-832. [PMID: 32237114 PMCID: PMC7318243 DOI: 10.1002/cmdc.201900727] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [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] [Received: 12/20/2019] [Indexed: 01/25/2023]
Abstract
Due to its frequent mutations in multiple lethal cancers, KRAS is one of the most-studied anticancer targets nowadays. Since the discovery of the druggable allosteric binding site containing a G12C mutation, KRASG12C has been the focus of attention in oncology research. We report here a computationally driven approach aimed at identifying novel and selective KRASG12C covalent inhibitors. The workflow involved initial enumeration of virtual molecules tailored for the KRAS allosteric binding site. Tools such as pharmacophore modeling, docking, and free-energy perturbations were deployed to prioritize the compounds with the best profiles. The synthesized naphthyridinone scaffold showed the ability to react with G12C and inhibit KRASG12C . Analogues were prepared to establish structure-activity relationships, while molecular dynamics simulations and crystallization of the inhibitor-KRASG12C complex highlighted an unprecedented binding mode.
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Affiliation(s)
- Jérémie Mortier
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Anders Friberg
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Volker Badock
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Dieter Moosmayer
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Jens Schroeder
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Patrick Steigemann
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Franziska Siegel
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Stefan Gradl
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Marcus Bauser
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Roman C Hillig
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Hans Briem
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Knut Eis
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Benjamin Bader
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Duy Nguyen
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
| | - Clara D Christ
- Bayer AG, Research & Development, Pharmaceuticals, Müllerstrasse 178, 13342, Berlin, Germany
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Gruenewald S, Sperl C, Steigemann P, Walter A, Zacharias S, Eberspaecher U, Neuhaus R, Zorn L, Schwede W, Thede K, Christian S. Abstract 4989: 3D spheroid screen yields SCD1 pathway inhibitors for the treatment of cancer. Cancer Res 2017. [DOI: 10.1158/1538-7445.am2017-4989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
With three-dimensional growth conditions, multicellular tumor spheroids reproduce several parameters of the tumor microenvironment, including oxygen and nutrient gradients, characteristic of poorly vascularized tumor regions. 3D high content screening (HCS) identified compounds that selectively kill tumor cells in the inner core of tumor cell spheroids by targeting the Stearoyl CoA Desaturase 1 (SCD1) pathway. SCD1 catalyzes the rate-limiting step in the production of mono-unsaturated fatty acids (MUFAs). Cancer cells are dependent on higher levels of MUFAs compared to normal cells and SCD1 is highly expressed in multiple tumor types. Changes in the MUFA / SFA (saturated fatty acid) ratio alters lipid biosynthesis and thus triggers cellular (ER) stress and induces the Unfolded Protein Response. Although the lead compound was very effective in vitro, it had unfavorable PK and physical chemistry properties, including low permeability and solubility and very high lipophilicity. This led to insufficient oral bioavailability, which could be overcome by optimization of PK and physical chemistry properties. Here, we report on the in vitro/in vivo effects of our 3D HCS compounds which showed high potency in the 3D spheroid inner core death assay with T47D breast cancer cells. In this in vitro model compound-induced inner core cell death is enhanced by SCD1 substrates palmitic or stearic acid and rescued by the SCD1 products palmitoleic or oleic acid. Furthermore, the effects can be reproduced in 2D cultures, which become increasingly sensitive to inhibition by our 3D HCS compounds with decreasing FBS concentration in the culture medium and this effect can also be rescued by addition of MUFAs but not of palmitic acid. Mode of action analysis showed that our compounds reduced palmitoleoyl- or oleoyl-CoA levels and simultaneously increased saturated fatty acyl-CoAs of palmitate or stearate in several cell lines as well as in vivo. In the sensitive T47D cells, the compounds induced expression of stress response genes and genes related to lipid metabolism. While these results support the SCD1 pathway as target for our 3D HCS compounds, we also observed striking differences to published SCD1 inhibitors suggesting a new cancer target beyond SCD1. Thus, further validation of our inhibitors in vitro and in vivo will be required, but these results suggest that 3D spheroid cultures may be a valuable tool for elucidation of new drug targets for cancer therapy.
Citation Format: Sylvia Gruenewald, Carolyn Sperl, Patrick Steigemann, Alexander Walter, Sylvia Zacharias, Uwe Eberspaecher, Roland Neuhaus, Ludwig Zorn, Wolfgang Schwede, Kai Thede, Sven Christian. 3D spheroid screen yields SCD1 pathway inhibitors for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4989. doi:10.1158/1538-7445.AM2017-4989
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Klutzny S, Lesche R, Keck M, Kaulfuss S, Schlicker A, Christian S, Sperl C, Neuhaus R, Mowat J, Steckel M, Riefke B, Prechtl S, Parczyk K, Steigemann P. Functional inhibition of acid sphingomyelinase by Fluphenazine triggers hypoxia-specific tumor cell death. Cell Death Dis 2017; 8:e2709. [PMID: 28358364 PMCID: PMC5386533 DOI: 10.1038/cddis.2017.130] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 02/14/2017] [Accepted: 02/16/2017] [Indexed: 12/12/2022]
Abstract
Owing to lagging or insufficient neo-angiogenesis, hypoxia is a feature of most solid tumors. Hypoxic tumor regions contribute to resistance against antiproliferative chemotherapeutics, radiotherapy and immunotherapy. Targeting cells in hypoxic tumor areas is therefore an important strategy for cancer treatment. Most approaches for targeting hypoxic cells focus on the inhibition of hypoxia adaption pathways but only a limited number of compounds with the potential to specifically target hypoxic tumor regions have been identified. By using tumor spheroids in hypoxic conditions as screening system, we identified a set of compounds, including the phenothiazine antipsychotic Fluphenazine, as hits with novel mode of action. Fluphenazine functionally inhibits acid sphingomyelinase and causes cellular sphingomyelin accumulation, which induces cancer cell death specifically in hypoxic tumor spheroids. Moreover, we found that functional inhibition of acid sphingomyelinase leads to overactivation of hypoxia stress-response pathways and that hypoxia-specific cell death is mediated by the stress-responsive transcription factor ATF4. Taken together, the here presented data suggest a novel, yet unexplored mechanism in which induction of sphingolipid stress leads to the overactivation of hypoxia stress-response pathways and thereby promotes their pro-apoptotic tumor-suppressor functions to specifically kill cells in hypoxic tumor areas.
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Affiliation(s)
- Saskia Klutzny
- Drug Discovery, Bayer AG, Berlin 13353, Germany.,Department of Bioanalytics, Institute for Biotechnology, Technical University of Berlin, Berlin, Germany
| | - Ralf Lesche
- Drug Discovery, Bayer AG, Berlin 13353, Germany
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8
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Hernando H, Gelato KA, Lesche R, Beckmann G, Koehr S, Otto S, Steigemann P, Stresemann C. EZH2 Inhibition Blocks Multiple Myeloma Cell Growth through Upregulation of Epithelial Tumor Suppressor Genes. Mol Cancer Ther 2015; 15:287-98. [DOI: 10.1158/1535-7163.mct-15-0486] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 11/09/2015] [Indexed: 11/16/2022]
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Wenzel C, Christian S, Algire C, Schwede W, Neuhaus R, Guenther J, Liu N, Raese S, Parczyk K, Prechtl S, Steigemann P. Abstract 317: 3D high-content screening for the identification of compounds that target cells in dormant tumor spheroid regions. Tumour Biol 2015. [DOI: 10.1158/1538-7445.am2015-317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Gentili C, Castor D, Kaden S, Lauterbach D, Gysi M, Steigemann P, Gerlich DW, Jiricny J, Ferrari S. Chromosome Missegregation Associated with RUVBL1 Deficiency. PLoS One 2015; 10:e0133576. [PMID: 26201077 PMCID: PMC4511761 DOI: 10.1371/journal.pone.0133576] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 06/30/2015] [Indexed: 12/31/2022] Open
Abstract
RUVBL1 (RuvB-like1) and RUVBL2 (RuvB-like 2) are integral components of multisubunit protein complexes involved in processes ranging from cellular metabolism, transcription and chromatin remodeling to DNA repair. Here, we show that although RUVBL1 and RUVBL2 are known to form heterodimeric complexes in which they stabilize each other, the subunits separate during cytokinesis. In anaphase-to-telophase transition, RUVBL1 localizes to structures of the mitotic spindle apparatus, where it partially co-localizes with polo-like kinase 1 (PLK1). The ability of PLK1 to phosphorylate RUVBL1-but not RUVBL2-in vitro and their physical association in vivo suggest that this kinase differentially regulates the function of the RuvB-like proteins during mitosis. We further show that siRNA-mediated knock-down of RuvB-like proteins causes severe defects in chromosome alignment and segregation. In addition, we show that the ATPase activity of RUVBL1 is indispensable for cell proliferation. Our data thus demonstrate that RUVBL1 is essential for efficient mitosis and proliferation.
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Affiliation(s)
- Christian Gentili
- Institute of Molecular Cancer Research of the University of Zurich and the ETH Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Dennis Castor
- Institute of Molecular Cancer Research of the University of Zurich and the ETH Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Svenja Kaden
- Institute of Molecular Cancer Research of the University of Zurich and the ETH Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - David Lauterbach
- Institute of Molecular Cancer Research of the University of Zurich and the ETH Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Mario Gysi
- Institute of Molecular Cancer Research of the University of Zurich and the ETH Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Patrick Steigemann
- Institute of Biochemistry, Schafmattstrasse 18, HPM E17.2, Swiss Institute of Technology Zurich (ETHZ), CH-8093, Zurich, Switzerland
| | - Daniel W. Gerlich
- Institute of Biochemistry, Schafmattstrasse 18, HPM E17.2, Swiss Institute of Technology Zurich (ETHZ), CH-8093, Zurich, Switzerland
| | - Josef Jiricny
- Institute of Molecular Cancer Research of the University of Zurich and the ETH Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Stefano Ferrari
- Institute of Molecular Cancer Research of the University of Zurich and the ETH Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
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11
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Wenzel C, Riefke B, Gründemann S, Krebs A, Christian S, Prinz F, Osterland M, Golfier S, Räse S, Ansari N, Esner M, Bickle M, Pampaloni F, Mattheyer C, Stelzer EH, Parczyk K, Prechtl S, Steigemann P. 3D high-content screening for the identification of compounds that target cells in dormant tumor spheroid regions. Exp Cell Res 2014; 323:131-143. [PMID: 24480576 DOI: 10.1016/j.yexcr.2014.01.017] [Citation(s) in RCA: 177] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 01/15/2014] [Accepted: 01/16/2014] [Indexed: 12/31/2022]
Abstract
Cancer cells in poorly vascularized tumor regions need to adapt to an unfavorable metabolic microenvironment. As distance from supplying blood vessels increases, oxygen and nutrient concentrations decrease and cancer cells react by stopping cell cycle progression and becoming dormant. As cytostatic drugs mainly target proliferating cells, cancer cell dormancy is considered as a major resistance mechanism to this class of anti-cancer drugs. Therefore, substances that target cancer cells in poorly vascularized tumor regions have the potential to enhance cytostatic-based chemotherapy of solid tumors. With three-dimensional growth conditions, multicellular tumor spheroids (MCTS) reproduce several parameters of the tumor microenvironment, including oxygen and nutrient gradients as well as the development of dormant tumor regions. We here report the setup of a 3D cell culture compatible high-content screening system and the identification of nine substances from two commercially available drug libraries that specifically target cells in inner MCTS core regions, while cells in outer MCTS regions or in 2D cell culture remain unaffected. We elucidated the mode of action of the identified compounds as inhibitors of the respiratory chain and show that induction of cell death in inner MCTS core regions critically depends on extracellular glucose concentrations. Finally, combinational treatment with cytostatics showed increased induction of cell death in MCTS. The data presented here shows for the first time a high-content based screening setup on 3D tumor spheroids for the identification of substances that specifically induce cell death in inner tumor spheroid core regions. This validates the approach to use 3D cell culture screening systems to identify substances that would not be detectable by 2D based screening in otherwise similar culture conditions.
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Affiliation(s)
- Carsten Wenzel
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Björn Riefke
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Stephan Gründemann
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Alice Krebs
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Sven Christian
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Florian Prinz
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Marc Osterland
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Sven Golfier
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Sebastian Räse
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Nariman Ansari
- Physical Biology Group, Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University Frankfurt, Germany
| | - Milan Esner
- Max Planck Institute of Molecular Cell Biology and Genetics, High-Throughput Technology Development Studio (TDS), Dresden, Germany
| | - Marc Bickle
- Max Planck Institute of Molecular Cell Biology and Genetics, High-Throughput Technology Development Studio (TDS), Dresden, Germany
| | - Francesco Pampaloni
- Physical Biology Group, Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University Frankfurt, Germany
| | - Christian Mattheyer
- Physical Biology Group, Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University Frankfurt, Germany
| | - Ernst H Stelzer
- Physical Biology Group, Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University Frankfurt, Germany
| | - Karsten Parczyk
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Stefan Prechtl
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany
| | - Patrick Steigemann
- Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin, Germany.
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12
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Maerki S, Olma MH, Staubli T, Steigemann P, Gerlich DW, Quadroni M, Sumara I, Peter M. The Cul3-KLHL21 E3 ubiquitin ligase targets aurora B to midzone microtubules in anaphase and is required for cytokinesis. ACTA ACUST UNITED AC 2010; 187:791-800. [PMID: 19995937 PMCID: PMC2806313 DOI: 10.1083/jcb.200906117] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Selective ubiquitination of Aurora B by different Cul3 adaptors targets it at the correct time to the correct place during mitosis. Cul3 (Cullin3)-based E3 ubiquitin ligases recently emerged as critical regulators of mitosis. In this study, we identify two mammalian BTB (Bric-a-brac–Tramtrack–Broad complex)-Kelch proteins, KLHL21 and KLHL22, that interact with Cul3 and are required for efficient chromosome alignment. Interestingly, KLHL21 but not KLHL22 is necessary for cytokinesis and regulates translocation of the chromosomal passenger complex (CPC) from chromosomes to the spindle midzone in anaphase, similar to the previously described BTB-Kelch proteins KLHL9 and KLHL13. KLHL21 directly binds to Aurora B and mediates ubiquitination of Aurora B in vitro. In contrast to KLHL9 and KLHL13, KLHL21 localizes to midzone microtubules in anaphase and recruits Aurora B and Cul3 to this region. Together, our results suggest that different Cul3 adaptors nonredundantly regulate Aurora B during mitosis, possibly by ubiquitinating different pools of Aurora B at distinct subcellular localizations.
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Affiliation(s)
- Sarah Maerki
- Institute of Biochemistry, Swiss Federal Institute of Technology Zurich, CH-8093 Zurich, Switzerland
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13
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Steigemann P, Gerlich DW. Cytokinetic abscission: cellular dynamics at the midbody. Trends Cell Biol 2009; 19:606-16. [PMID: 19733077 DOI: 10.1016/j.tcb.2009.07.008] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 07/18/2009] [Accepted: 07/20/2009] [Indexed: 10/20/2022]
Abstract
The intercellular canal containing the midbody is one of the most prominent structures in dividing animal cells, yet its function in the completion of cytokinesis by abscission remains largely unknown. This is because of its small size, which makes it difficult to investigate the cytoskeletal and membrane dynamics underlying abscission by standard light microscopy. The advent of new fluorescent probes and imaging technologies, along with sophisticated perturbation tools, provides new possibilities to elucidate the molecular control of this essential cell biological process. Here we discuss the control of midbody assembly and current models for the mechanism of abscission in animal cells. We highlight new methodologies that will facilitate testing and refining of these models.
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Affiliation(s)
- Patrick Steigemann
- Institute of Biochemistry, Swiss Federal Institute of Technology Zurich (ETHZ), Schafmattstr. 18, CH-8093 Zurich, Switzerland
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14
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Steigemann P, Gerlich DW. An evolutionary conserved checkpoint controls abscission timing. Cell Cycle 2009; 8:1814-1815. [PMID: 19471121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
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15
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Steigemann P, Wurzenberger C, Schmitz MHA, Held M, Guizetti J, Maar S, Gerlich DW. Aurora B-mediated abscission checkpoint protects against tetraploidization. Cell 2009; 136:473-84. [PMID: 19203582 DOI: 10.1016/j.cell.2008.12.020] [Citation(s) in RCA: 463] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Revised: 09/24/2008] [Accepted: 12/05/2008] [Indexed: 01/12/2023]
Abstract
Genomic abnormalities are often seen in tumor cells, and tetraploidization, which results from failures during cytokinesis, is presumed to be an early step in cancer formation. Here, we report a cell division control mechanism that prevents tetraploidization in human cells with perturbed chromosome segregation. First, we found that Aurora B inactivation promotes completion of cytokinesis by abscission. Chromosome bridges sustained Aurora B activity to posttelophase stages and thereby delayed abscission at stabilized intercellular canals. This was essential to suppress tetraploidization by furrow regression in a pathway further involving the phosphorylation of mitotic kinesin-like protein 1 (Mklp1). We propose that Aurora B is part of a sensor that responds to unsegregated chromatin at the cleavage site. Our study provides evidence that in human cells abscission is coordinated with the completion of chromosome segregation to protect against tetraploidization by furrow regression.
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Affiliation(s)
- Patrick Steigemann
- Institute of Biochemistry, Swiss Institute of Technology Zurich, ETHZ, Zurich, Switzerland
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16
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Steigemann P, Molitor A, Fellert S, Jäckle H, Vorbrüggen G. Heparan sulfate proteoglycan syndecan promotes axonal and myotube guidance by slit/robo signaling. Curr Biol 2004; 14:225-30. [PMID: 14761655 DOI: 10.1016/j.cub.2004.01.006] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.1] [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: 10/23/2003] [Revised: 12/16/2003] [Accepted: 12/16/2003] [Indexed: 10/22/2022]
Abstract
Slit, the ligand for the Roundabout (Robo) receptors, is secreted from midline cells of the Drosophila central nervous system (CNS). It acts as a short-range repellent that controls midline crossing of axons and allows growth cones to select specific pathways along each side of the midline. In addition, Slit directs the migration of muscle precursors and ventral branches of the tracheal system, showing that it provides long-range activity beyond the limit of the developing CNS. Biochemical studies suggest that guidance activity requires cell-surface heparan sulfate to promote binding of mammalian Slit/Robo homologs. Here, we report that the Drosophila homolog of Syndecan (reviewed in ), a heparan sulfate proteoglycan (HSPG), is required for proper Slit signaling. We generated syndecan (sdc) mutations and show that they affect all aspects of Slit activity and cause robo-like phenotypes. sdc interacts genetically with robo and slit, and double mutations cause a synergistic strengthening of the single-mutant phenotypes. The results suggest that Syndecan is a necessary component of Slit/Robo signaling and is required in the Slit target cells.
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Affiliation(s)
- Patrick Steigemann
- Abteilung Molekulare Entwicklungsbiologie, Max-Planck-Institut für biophysikalische Chemie, Am Fassberg 11, 37077 Goettingen, Germany
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17
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Abstract
Proteolysis triggered by the anaphase-promoting complex (APC) is needed for sister chromatid separation and the exit from mitosis. APC is a ubiquitin ligase whose activity is tightly controlled during the cell cycle. To identify factors involved in the regulation of APC-mediated proteolysis, a Saccharomyces cerevisiae GAL-cDNA library was screened for genes whose overexpression prevented degradation of an APC target protein, the mitotic cyclin Clb2. Genes encoding G1, S, and mitotic cyclins were identified, consistent with previous data showing that the cyclin-dependent kinase Cdk1 associated with different cyclins is a key factor for inhibiting APC(Cdh1) activity from late-G1 phase until mitosis. In addition, the meiosis-specific protein kinase Ime2 was identified as a negative regulator of APC-mediated proteolysis. Ectopic expression of IME2 in G1 arrested cells inhibited the degradation of mitotic cyclins and of other APC substrates. IME2 expression resulted in the phosphorylation of Cdh1 in G1 cells, indicating that Ime2 and Cdk1 regulate APC(Cdh1) in a similar manner. The expression of IME2 in cycling cells inhibited bud formation and caused cells to arrest in mitosis. We show further that Ime2 itself is an unstable protein whose proteolysis occurs independently of the APC and SCF (Skp1/Cdc53/F-box) ubiquitin ligases. Our findings suggest that Ime2 represents an unstable, meiosis-specific regulator of APC(Cdh1).
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Affiliation(s)
- Melanie Bolte
- Institute of Microbiology and Genetics, Georg-August-University, Grisebachstrasse 8, D-37077 Göttingen, Germany
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18
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Bäumer M, Künzler M, Steigemann P, Braus GH, Irniger S. Yeast Ran-binding protein Yrb1p is required for efficient proteolysis of cell cycle regulatory proteins Pds1p and Sic1p. J Biol Chem 2000; 275:38929-37. [PMID: 10991951 DOI: 10.1074/jbc.m007925200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ubiquitin-dependent proteolysis of specific target proteins is required for several important steps during the cell cycle. Degradation of such proteins is strictly cell cycle-regulated and triggered by two large ubiquitin ligases, termed anaphase-promoting complex (APC) and Skp1/Cullin/F-box complex (SCF). Here we show that yeast Ran-binding protein 1 (Yrb1p), a predominantly cytoplasmic protein implicated in nucleocytoplasmic transport, is required for cell cycle regulated protein degradation. Depletion of Yrb1p results in the accumulation of unbudded G(1) cells and of cells arrested in mitosis implying a function of Yrb1p in the G(1)/S transition and in the progression through mitosis. Temperature-sensitive yrb1-51 mutants are defective in APC-mediated degradation of the anaphase inhibitor protein Pds1p and in degradation of the cyclin-dependent kinase inhibitor Sic1p, a target of SCF. Thus, Yrb1p is crucial for efficient APC- and SCF-mediated proteolysis of important cell cycle regulatory proteins. We have identified the UBS1 gene as a multicopy suppressor of yrb1-51 mutants. Ubs1p is a nuclear protein, and its deletion is synthetic lethal with a yrb1-51 mutation. Interestingly, UBS1 was previously identified as a multicopy suppressor of cdc34-2 mutants, which are defective in SCF activity. We suggest that Ubs1p may represent a link between nucleocytoplasmic transport and ubiquitin ligase activity.
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Affiliation(s)
- M Bäumer
- Institute of Microbiology and Genetics, Georg-August-University, Grisebachstrasse 8, D-37077 Göttingen, Germany
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