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Chica N, Portantier M, Nyquist-Andersen M, Espada-Burriel S, Lopez-Aviles S. Uncoupling of Mitosis and Cytokinesis Upon a Prolonged Arrest in Metaphase Is Influenced by Protein Phosphatases and Mitotic Transcription in Fission Yeast. Front Cell Dev Biol 2022; 10:876810. [PMID: 35923846 PMCID: PMC9340479 DOI: 10.3389/fcell.2022.876810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 05/11/2022] [Indexed: 11/22/2022] Open
Abstract
Depletion of the Anaphase-Promoting Complex/Cyclosome (APC/C) activator Cdc20 arrests cells in metaphase with high levels of the mitotic cyclin (Cyclin B) and the Separase inhibitor Securin. In mammalian cells this arrest has been exploited for the treatment of cancer with drugs that engage the spindle assembly checkpoint and, recently, with chemical inhibitors of the APC/C. While most cells arrested in mitosis for prolonged periods undergo apoptosis, others skip cytokinesis and enter G1 with unsegregated chromosomes. This process, known as mitotic slippage, generates aneuploidy and increases genomic instability in the cancer cell. Here, we analyze the behavior of fission yeast cells arrested in mitosis through the transcriptional silencing of the Cdc20 homolog slp1. While depletion of slp1 readily halts cells in metaphase, this arrest is only transient and a majority of cells eventually undergo cytokinesis and show steady mitotic dephosphorylation. Notably, this occurs in the absence of Cyclin B (Cdc13) degradation. We investigate the involvement of phosphatase activity in these events and demonstrate that PP2A-B55Pab1 is required to prevent septation and, during the arrest, its CDK-mediated inhibition facilitates the induction of cytokinesis. In contrast, deletion of PP2A-B56Par1 completely abrogates septation. We show that this effect is partly due to this mutant entering mitosis with reduced CDK activity. Interestingly, both PP2A-B55Pab1 and PP2A-B56Par1, as well as Clp1 (the homolog of the budding yeast mitotic phosphatase Cdc14) are required for the dephosphorylation of mitotic substrates during the escape. Finally, we show that the mitotic transcriptional wave controlled by the RFX transcription factor Sak1 facilitates the induction of cytokinesis and also requires the activity of PP2A-B56Par1 in a mechanism independent of CDK.
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Affiliation(s)
- Nathalia Chica
- Centre for Molecular Medicine Norway (NCMM), Nordic EMBL partnership, Faculty of Medicine, University of Oslo, Oslo, Norway
- *Correspondence: Sandra Lopez-Aviles, ; Nathalia Chica,
| | - Marina Portantier
- Centre for Molecular Medicine Norway (NCMM), Nordic EMBL partnership, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Mari Nyquist-Andersen
- Centre for Molecular Medicine Norway (NCMM), Nordic EMBL partnership, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Silvia Espada-Burriel
- Centre for Molecular Medicine Norway (NCMM), Nordic EMBL partnership, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Sandra Lopez-Aviles
- Centre for Molecular Medicine Norway (NCMM), Nordic EMBL partnership, Faculty of Medicine, University of Oslo, Oslo, Norway
- Institute of Biosciences (IBV), Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
- *Correspondence: Sandra Lopez-Aviles, ; Nathalia Chica,
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Kachaev ZM, Ivashchenko SD, Kozlov EN, Lebedeva LA, Shidlovskii YV. Localization and Functional Roles of Components of the Translation Apparatus in the Eukaryotic Cell Nucleus. Cells 2021; 10:3239. [PMID: 34831461 PMCID: PMC8623629 DOI: 10.3390/cells10113239] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 11/11/2021] [Accepted: 11/16/2021] [Indexed: 12/15/2022] Open
Abstract
Components of the translation apparatus, including ribosomal proteins, have been found in cell nuclei in various organisms. Components of the translation apparatus are involved in various nuclear processes, particularly those associated with genome integrity control and the nuclear stages of gene expression, such as transcription, mRNA processing, and mRNA export. Components of the translation apparatus control intranuclear trafficking; the nuclear import and export of RNA and proteins; and regulate the activity, stability, and functional recruitment of nuclear proteins. The nuclear translocation of these components is often involved in the cell response to stimulation and stress, in addition to playing critical roles in oncogenesis and viral infection. Many components of the translation apparatus are moonlighting proteins, involved in integral cell stress response and coupling of gene expression subprocesses. Thus, this phenomenon represents a significant interest for both basic and applied molecular biology. Here, we provide an overview of the current data regarding the molecular functions of translation factors and ribosomal proteins in the cell nucleus.
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Affiliation(s)
- Zaur M. Kachaev
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
- Center for Genetics and Life Science, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Sergey D. Ivashchenko
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
| | - Eugene N. Kozlov
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
| | - Lyubov A. Lebedeva
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
| | - Yulii V. Shidlovskii
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
- Center for Genetics and Life Science, Sirius University of Science and Technology, 354340 Sochi, Russia
- Department of Biology and General Genetics, Sechenov First Moscow State Medical University (Sechenov University), 119992 Moscow, Russia
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3
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Raabe K, Honys D, Michailidis C. The role of eukaryotic initiation factor 3 in plant translation regulation. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 145:75-83. [PMID: 31665669 DOI: 10.1016/j.plaphy.2019.10.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/07/2019] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
Regulation of translation represents a critical step in the regulation of gene expression. In plants, the translation regulation plays an important role at all stages of development and, during stress responses, functions as a fast and flexible tool which not only modulates the global translation rate but also controls the production of specific proteins. Regulation of translation is mostly focused on the initiation phase. There, one of essential initiation factors is the large multisubunit protein complex of eukaryotic translation initiation factor 3 (eIF3). In all eukaryotes, the general eIF3 function is to scaffold the formation of the translation initiation complex and to enhance the accuracy of scanning mechanism for start codon selection. Over the past decades, additional eIF3 functions were described as necessary for development in various eukaryotic organisms, including plants. The importance of the eIF3 complex lies not only at the global level of initiation event, but also in the precise translation regulation of specific transcripts. This review gathers the available information on functions of the plant eIF3 complex.
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Affiliation(s)
- Karel Raabe
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic
| | - David Honys
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic
| | - Christos Michailidis
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic.
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4
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Hemming ML, Lawlor MA, Andersen JL, Hagan T, Chipashvili O, Scott TG, Raut CP, Sicinska E, Armstrong SA, Demetri GD, Bradner JE, Ganz PA, Tomlinson G, Olopade OI, Couch FJ, Wang X, Lindor NM, Pankratz VS, Radice P, Manoukian S, Peissel B, Zaffaroni D, Barile M, Viel A, Allavena A, Dall'Olio V, Peterlongo P, Szabo CI, Zikan M, Claes K, Poppe B, Foretova L, Mai PL, Greene MH, Rennert G, Lejbkowicz F, Glendon G, Ozcelik H, Andrulis IL, Thomassen M, Gerdes AM, Sunde L, Cruger D, Birk Jensen U, Caligo M, Friedman E, Kaufman B, Laitman Y, Milgrom R, Dubrovsky M, Cohen S, Borg A, Jernström H, Lindblom A, Rantala J, Stenmark-Askmalm M, Melin B, Nathanson K, Domchek S, Jakubowska A, Lubinski J, Huzarski T, Osorio A, Lasa A, Durán M, Tejada MI, Godino J, Benitez J, Hamann U, Kriege M, Hoogerbrugge N, van der Luijt RB, van Asperen CJ, Devilee P, Meijers-Heijboer EJ, Blok MJ, Aalfs CM, Hogervorst F, Rookus M, Cook M, Oliver C, Frost D, Conroy D, Evans DG, Lalloo F, Pichert G, Davidson R, Cole T, Cook J, Paterson J, Hodgson S, Morrison PJ, Porteous ME, Walker L, Kennedy MJ, Dorkins H, Peock S, Godwin AK, Stoppa-Lyonnet D, de Pauw A, Mazoyer S, Bonadona V, Lasset C, Dreyfus H, Leroux D, Hardouin A, Berthet P, Faivre L, Loustalot C, Noguchi T, Sobol H, Rouleau E, Nogues C, Frénay M, Vénat-Bouvet L, Hopper JL, Daly MB, Terry MB, John EM, Buys SS, Yassin Y, Miron A, Goldgar D, Singer CF, Dressler AC, Gschwantler-Kaulich D, Pfeiler G, Hansen TVO, Jønson L, Agnarsson BA, Kirchhoff T, Offit K, Devlin V, Dutra-Clarke A, Piedmonte M, Rodriguez GC, Wakeley K, Boggess JF, Basil J, Schwartz PE, Blank SV, Toland AE, Montagna M, Casella C, Imyanitov E, Tihomirova L, Blanco I, Lazaro C, Ramus SJ, Sucheston L, Karlan BY, Gross J, Schmutzler R, Wappenschmidt B, Engel C, Meindl A, Lochmann M, Arnold N, Heidemann S, Varon-Mateeva R, Niederacher D, Sutter C, Deissler H, Gadzicki D, Preisler-Adams S, Kast K, Schönbuchner I, Caldes T, de la Hoya M, Aittomäki K, Nevanlinna H, Simard J, Spurdle AB, Holland H, Chen X, Platte R, Chenevix-Trench G, Easton DF. Enhancer Domains in Gastrointestinal Stromal Tumor Regulate KIT Expression and Are Targetable by BET Bromodomain Inhibition. Cancer Res 2019. [PMID: 18483246 DOI: 10.1158/0008-5472] [Citation(s) in RCA: 690] [Impact Index Per Article: 138.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gastrointestinal stromal tumor (GIST) is a mesenchymal neoplasm characterized by activating mutations in the related receptor tyrosine kinases KIT and PDGFRA. GIST relies on expression of these unamplified receptor tyrosine kinase (RTK) genes through a large enhancer domain, resulting in high expression levels of the oncogene required for tumor growth. Although kinase inhibition is an effective therapy for many patients with GIST, disease progression from kinase-resistant mutations is common and no other effective classes of systemic therapy exist. In this study, we identify regulatory regions of the KIT enhancer essential for KIT gene expression and GIST cell viability. Given the dependence of GIST upon enhancer-driven expression of RTKs, we hypothesized that the enhancer domains could be therapeutically targeted by a BET bromodomain inhibitor (BBI). Treatment of GIST cells with BBIs led to cell-cycle arrest, apoptosis, and cell death, with unique sensitivity in GIST cells arising from attenuation of the KIT enhancer domain and reduced KIT gene expression. BBI treatment in KIT-dependent GIST cells produced genome-wide changes in the H3K27ac enhancer landscape and gene expression program, which was also seen with direct KIT inhibition using a tyrosine kinase inhibitor (TKI). Combination treatment with BBI and TKI led to superior cytotoxic effects in vitro and in vivo, with BBI preventing tumor growth in TKI-resistant xenografts. Resistance to select BBI in GIST was attributable to drug efflux pumps. These results define a therapeutic vulnerability and clinical strategy for targeting oncogenic kinase dependency in GIST. SIGNIFICANCE: Expression and activity of mutant KIT is essential for driving the majority of GIST neoplasms, which can be therapeutically targeted using BET bromodomain inhibitors.
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Affiliation(s)
- Matthew L Hemming
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts. .,Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Matthew A Lawlor
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Jessica L Andersen
- Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Timothy Hagan
- Department of Oncologic Pathology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Otari Chipashvili
- Department of Oncologic Pathology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Thomas G Scott
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Chandrajit P Raut
- Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Ewa Sicinska
- Department of Oncologic Pathology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Scott A Armstrong
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - George D Demetri
- Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.,Ludwig Center at Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts
| | - James E Bradner
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
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5
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Sadato D, Ono T, Gotoh-Saito S, Kajiwara N, Nomura N, Ukaji M, Yang L, Sakimura K, Tajima Y, Oboki K, Shibasaki F. Eukaryotic translation initiation factor 3 (eIF3) subunit e is essential for embryonic development and cell proliferation. FEBS Open Bio 2018; 8:1188-1201. [PMID: 30087825 PMCID: PMC6070656 DOI: 10.1002/2211-5463.12482] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/13/2018] [Accepted: 06/12/2018] [Indexed: 11/06/2022] Open
Abstract
Mammalian eukaryotic translation initiation factor 3 (eIF3) is the largest complex of the translation initiation factors. The eIF3 complex is comprised of thirteen subunits, which are named eIF3a to eIF3 m in most multicellular organisms. The eIF3e gene locus is one of the most frequent integration sites of mouse mammary tumor virus (MMTV), which induces mammary tumors in mice. MMTV-integration events result in the expression of C-terminal-truncated eIF3e proteins, leading to mammary tumor formation. We have shown that tumor formation can be partly caused by activation of hypoxia-inducible factor 2α. To investigate the function of eIF3e in mammals, we generated eIF3e-deficient mice. These eIF3e-/- mice are embryonically lethal, while eIF3e+/- mice are much smaller than wild-type mice. In addition, eIF3e+/- mouse embryonic fibroblasts (MEFs) contained reduced levels of eIF3a and eIF3c subunits and exhibited reduced cellular proliferation. These results suggest that eIF3e is essential for embryonic development in mice and plays a role in maintaining eIF3 integrity.
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Affiliation(s)
- Daichi Sadato
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan.,Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
| | - Tomio Ono
- Center for Basic Technology Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Saki Gotoh-Saito
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Naoki Kajiwara
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Namiko Nomura
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Masako Ukaji
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Liying Yang
- Center for Basic Technology Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology Brain Research Institute Niigata University Japan
| | - Youichi Tajima
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Keisuke Oboki
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Futoshi Shibasaki
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
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6
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Renda F, Pellacani C, Strunov A, Bucciarelli E, Naim V, Bosso G, Kiseleva E, Bonaccorsi S, Sharp DJ, Khodjakov A, Gatti M, Somma MP. The Drosophila orthologue of the INT6 onco-protein regulates mitotic microtubule growth and kinetochore structure. PLoS Genet 2017; 13:e1006784. [PMID: 28505193 PMCID: PMC5448806 DOI: 10.1371/journal.pgen.1006784] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 05/30/2017] [Accepted: 04/27/2017] [Indexed: 12/01/2022] Open
Abstract
INT6/eIF3e is a highly conserved component of the translation initiation complex that interacts with both the 26S proteasome and the COP9 signalosome, two complexes implicated in ubiquitin-mediated protein degradation. The INT6 gene was originally identified as the insertion site of the mouse mammary tumor virus (MMTV), and later shown to be involved in human tumorigenesis. Here we show that depletion of the Drosophila orthologue of INT6 (Int6) results in short mitotic spindles and deformed centromeres and kinetochores with low intra-kinetochore distance. Poleward flux of microtubule subunits during metaphase is reduced, although fluorescence recovery after photobleaching (FRAP) demonstrates that microtubules remain dynamic both near the kinetochores and at spindle poles. Mitotic progression is delayed during metaphase due to the activity of the spindle assembly checkpoint (SAC). Interestingly, a deubiquitinated form of the kinesin Klp67A (a putative orthologue of human Kif18A) accumulates near the kinetochores in Int6-depleted cells. Consistent with this finding, Klp67A overexpression mimics the Int6 RNAi phenotype. Furthermore, simultaneous depletion of Int6 and Klp67A results in a phenotype identical to RNAi of just Klp67A, which indicates that Klp67A deficiency is epistatic over Int6 deficiency. We propose that Int6-mediated ubiquitination is required to control the activity of Klp67A. In the absence of this control, excess of Klp67A at the kinetochore suppresses microtubule plus-end polymerization, which in turn results in reduced microtubule flux, spindle shortening, and centromere/kinetochore deformation.
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Affiliation(s)
- Fioranna Renda
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Claudia Pellacani
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Roma, Italy
| | - Anton Strunov
- Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk, Russia
- Institute of Cytology and Genetics, Siberian Branch of RAS, Novosibirsk, Russia
| | | | - Valeria Naim
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Giuseppe Bosso
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - Elena Kiseleva
- Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk, Russia
- Institute of Cytology and Genetics, Siberian Branch of RAS, Novosibirsk, Russia
| | - Silvia Bonaccorsi
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
| | - David J. Sharp
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Alexey Khodjakov
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Maurizio Gatti
- Dipartimento di Biologia e Biotecnologie “C. Darwin”, Sapienza, Università di Roma, Roma, Italy
- Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Roma, Italy
- Institute of Molecular and Cellular Biology, Siberian Branch of RAS, Novosibirsk, Russia
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7
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Wang W, Xu M, Liu X, Tu J. The Rice Eukaryotic Translation Initiation Factor 3 Subunit e (OseIF3e) Influences Organ Size and Pollen Maturation. FRONTIERS IN PLANT SCIENCE 2016; 7:1399. [PMID: 27703462 PMCID: PMC5028392 DOI: 10.3389/fpls.2016.01399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/02/2016] [Indexed: 05/24/2023]
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a large protein complex that participates in most translation initiation processes. While eIF3 has been well characterized, less is known about the roles of individual eIF3 subunits, particularly in plants. Here, we identified and characterized OseIF3e in rice (Oryza sativa L.). OseIF3e was constitutively expressed in various tissues, but most strongly in vigorously growing organs. Transgenic OseIF3e-silenced rice plants showed inhibited growth in seedling and vegetative stages. Repression of OseIF3e led to defects in pollen maturation but did not affect pollen mitosis. In rice, eIF3e interacted with eIF3 subunits b, d, e, f, h, and k, and with eIF6, forming homo- and heterodimers to initiate translation. Furthermore, OseIF3e was shown by yeast two-hybrid assay to specifically bind to inhibitors of cyclin-dependent kinases 1, 5, and 6. This interaction was mediated by the sequence of amino acid residues at positions 118-138, which included a conserved motif (IGPEQIETLYQFAKF). These results suggested although OseIF3e is not a "functional core" subunit of eIF3, it still plays crucial roles in rice growth and development, in combination with other factors. We proposed a pathway by which OseIF3e influence organ size and pollen maturation in rice, providing an opportunity to optimize plant architecture for crop breeding.
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8
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Morris C, Tomimatsu N, Burma S, Jalinot P. INT6/EIF3E Controls the RNF8-Dependent Ubiquitylation Pathway and Facilitates DNA Double-Strand Break Repair in Human Cells. Cancer Res 2016; 76:6054-6065. [PMID: 27550454 DOI: 10.1158/0008-5472.can-16-0723] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 07/27/2016] [Indexed: 11/16/2022]
Abstract
Unrepaired DNA double-strand breaks (DSB) are the most destructive chromosomal lesions driving genomic instability, a core hallmark of cancer. Here, we identify the antioncogenic breast cancer factor INT6/EIF3E as an essential regulator of DSB repair that promotes homologous recombination (HR)-mediated repair and, to a lesser extent, nonhomologous end-joining repair. INT6 silencing impaired the accrual of the ubiquitin ligase RNF8 at DSBs and the formation of ubiquitin conjugates at DSB sites, especially Lys63-linked polyubiquitin chains, resulting in impaired recruitment of BRCA1, BRCA2, and RAD51, which are all involved in HR repair. In contrast, INT6 deficiency did not affect the accumulation of RNF168, 53BP1, or RPA at DSBs. In INT6-silenced cells, there was also an alteration in DNA damage-induced localization of MDC1, a key target for ATM phosphorylation, which is a prerequisite for RNF8 recruitment. The attenuated DNA damage localization of RNF8 resulting from INT6 depletion could be attributed to the defective retention of ATM previously reported by us. Our findings deepen insights into how INT6 protects against breast cancer by showing how it functions in DSB repair, with potential clinical implications for cancer therapy. Cancer Res; 76(20); 6054-65. ©2016 AACR.
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Affiliation(s)
- Christelle Morris
- Laboratory of Biology and Modelling of the Cell, CNRS UMR 5239, INSERM U1210, ENS de Lyon, University of Lyon, Lyon, France
| | - Nozomi Tomimatsu
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Sandeep Burma
- Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Pierre Jalinot
- Laboratory of Biology and Modelling of the Cell, CNRS UMR 5239, INSERM U1210, ENS de Lyon, University of Lyon, Lyon, France.
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9
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Suo J, Medina D, Herrera S, Zheng ZY, Jin L, Chamness GC, Contreras A, Gutierrez C, Hilsenbeck S, Umar A, Foekens JA, Hanash S, Schiff R, Zhang XHF, Chang EC. Int6 reduction activates stromal fibroblasts to enhance transforming activity in breast epithelial cells. Cell Biosci 2015; 5:10. [PMID: 25774287 PMCID: PMC4359526 DOI: 10.1186/s13578-015-0001-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 02/09/2015] [Indexed: 12/21/2022] Open
Abstract
Background The INT6 gene was first discovered as a site of integration in mouse mammary tumors by the mouse mammary tumor virus; however, INT6’s role in the development of human breast cancer remains largely unknown. By gene silencing, we have previously shown that repressing INT6 promotes transforming activity in untransformed human mammary epithelial cells. In the present study, guided by microarray data of human tumors, we have discovered a role of Int6 in stromal fibroblasts. Results We searched microarray databases of human tumors to assess Int6’s role in breast cancer. While INT6 expression levels, as expected, were lower in breast tumors than in adjacent normal breast tissue samples, INT6 expression levels were also substantially lower in tumor stroma. By immunohistochemistry, we determined that the low levels of INT6 mRNA observed in the microarray databases most likely occurs in stromal fibroblasts, because far fewer fibroblasts in the tumor tissue showed detectable levels of the Int6 protein. To directly investigate the effects of Int6 repression on fibroblasts, we silenced INT6 expression in immortalized human mammary fibroblasts (HMFs). When these INT6-repressed HMFs were co-cultured with breast cancer cells, the abilities of the latter to form colonies in soft agar and to invade were enhanced. We analyzed INT6-repressed HMFs and found an increase in the levels of a key carcinoma-associated fibroblast (CAF) marker, smooth muscle actin. Furthermore, like CAFs, these INT6-repressed HMFs secreted more stromal cell–derived factor 1 (SDF-1), and the addition of an SDF-1 antagonist attenuated the INT6-repressed HMFs’ ability to enhance soft agar colony formation when co-cultured with cancer cells. These INT6-repressed HMFs also expressed high levels of mesenchymal markers such as vimentin and N-cadherin. Intriguingly, when mesenchymal stem cells (MSCs) were induced to form CAFs, Int6 levels were reduced. Conclusion These data suggest that besides enhancing transforming activity in epithelial cells, INT6 repression can also induce fibroblasts, and possibly MSCs as well, via mesenchymal-mesenchymal transitions to promote the formation of CAFs, leading to a proinvasive microenvironment for tumorigenesis.
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Affiliation(s)
- Jinfeng Suo
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, 77030 TX USA ; Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Daniel Medina
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Sabrina Herrera
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Ze-Yi Zheng
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Lei Jin
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Gary C Chamness
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Alejandro Contreras
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Carolina Gutierrez
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Susan Hilsenbeck
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Arzu Umar
- Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | - John A Foekens
- Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Samir Hanash
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, 77030 TX USA
| | - Rachel Schiff
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Xiang H-F Zhang
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Eric C Chang
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
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10
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Abstract
For centuries yeast species have been popular hosts for classical biotechnology processes, such as baking, brewing, and wine making, and more recently for recombinant proteins production, thanks to the advantages of unicellular organisms (i.e., ease of genetic manipulation and rapid growth) together with the ability to perform eukaryotic posttranslational modifications. Moreover, yeast cells have been used for few decades as a tool for identifying the genes and pathways involved in basic cellular processes such as the cell cycle, aging, and stress response. In the budding yeast S. cerevisiae the Ras/cAMP/PKA pathway is directly involved in the regulation of metabolism, cell growth, stress resistance, and proliferation in response to the availability of nutrients and in the adaptation to glucose, controlling cytosolic cAMP levels and consequently the cAMP-dependent protein kinase (PKA) activity. Moreover, Ras signalling has been identified in several pathogenic yeasts as a key controller for virulence, due to its involvement in yeast morphogenesis. Nowadays, yeasts are still useful for Ras-like proteins investigation, both as model organisms and as a test tube to study variants of heterologous Ras-like proteins.
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Affiliation(s)
- Renata Tisi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
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11
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Buda P, Reinbothe T, Nagaraj V, Mahdi T, Luan C, Tang Y, Axelsson AS, Li D, Rosengren AH, Renström E, Zhang E. Eukaryotic translation initiation factor 3 subunit e controls intracellular calcium homeostasis by regulation of cav1.2 surface expression. PLoS One 2013; 8:e64462. [PMID: 23737983 PMCID: PMC3667822 DOI: 10.1371/journal.pone.0064462] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Accepted: 04/15/2013] [Indexed: 01/09/2023] Open
Abstract
Inappropriate surface expression of voltage-gated Ca2+channels (CaV) in pancreatic ß-cells may contribute to the development of type 2 diabetes. First, failure to increase intracellular Ca2+ concentrations at the sites of exocytosis impedes insulin release. Furthermore, excessive Ca2+ influx may trigger cytotoxic effects. The regulation of surface expression of CaV channels in the pancreatic β-cells remains unknown. Here, we used real-time 3D confocal and TIRFM imaging, immunocytochemistry, cellular fractionation, immunoprecipitation and electrophysiology to study trafficking of L-type CaV1.2 channels upon β-cell stimulation. We found decreased surface expression of CaV1.2 and a corresponding reduction in L-type whole-cell Ca2+ currents in insulin-secreting INS-1 832/13 cells upon protracted (15–30 min) stimulation. This internalization occurs by clathrin-dependent endocytosis and could be prevented by microtubule or dynamin inhibitors. eIF3e (Eukaryotic translation initiation factor 3 subunit E) is part of the protein translation initiation complex, but its effect on translation are modest and effects in ion channel trafficking have been suggested. The factor interacted with CaV1.2 and regulated CaV1.2 traffic bidirectionally. eIF3e silencing impaired CaV1.2 internalization, which resulted in an increased intracellular Ca2+ load upon stimulation. These findings provide a mechanism for regulation of L-type CaV channel surface expression with consequences for β-cell calcium homeostasis, which will affect pancreatic β-cell function and insulin production.
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Affiliation(s)
- Pawel Buda
- Lund University Diabetes Center, Malmö, Sweden
| | | | | | - Taman Mahdi
- Lund University Diabetes Center, Malmö, Sweden
| | - Cheng Luan
- Lund University Diabetes Center, Malmö, Sweden
| | - Yunzhao Tang
- Lund University Diabetes Center, Malmö, Sweden
- Key Lab of Hormones and Development, Ministry of Health, and Metabolic Diseases Hospital, Tianjin Medical University, Tianjin, China
| | | | - Daiqing Li
- Key Lab of Hormones and Development, Ministry of Health, and Metabolic Diseases Hospital, Tianjin Medical University, Tianjin, China
| | | | - Erik Renström
- Lund University Diabetes Center, Malmö, Sweden
- * E-mail: (ER); (EZ)
| | - Enming Zhang
- Lund University Diabetes Center, Malmö, Sweden
- * E-mail: (ER); (EZ)
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12
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Decreased eIF3e/Int6 expression causes epithelial-to-mesenchymal transition in breast epithelial cells. Oncogene 2012; 32:3598-605. [PMID: 22907435 DOI: 10.1038/onc.2012.371] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 06/19/2012] [Accepted: 07/09/2012] [Indexed: 02/07/2023]
Abstract
eIF3e/Int6 is a component of the multi-subunit eIF3 complex, which binds directly to the 40S ribosome to facilitate ribosome recruitment to mRNA and hence protein synthesis. Reduced expression of eIF3e/Int6 has been found in up to 37% of human breast cancers, and expression of a truncated mutant version of the mouse eIF3e/Int6 protein leads to malignant transformation of normal mammary cells. These findings suggest that eIF3e/Int6 is a tumor suppressor; however, a recent study has reported that a reduction of eIF3e/Int6 expression in breast cancer cells leads to reduced translation of oncogenes, suggesting that eIF3e/Int6 may in fact have an oncogenic role in breast cancer. To gain a better understanding of the role of eIF3e/Int6 in breast cancer, we have examined the effects of decreased eIF3e/Int6 expression in an immortalized breast epithelial cell line, MCF-10A. Surprisingly, we find that decreased expression of eIF3e/Int6 causes breast epithelial cells to undergo epithelial-to-mesenchymal transition (EMT). We show that EMT induced by a decrease in eIF3e/Int6 expression imparts invasive and migratory properties to breast epithelial cells, suggesting that regulation of EMT by eIF3e/Int6 may have an important role in breast cancer metastasis. Furthermore, we show that reduced eIF3e/Int6 expression in breast epithelial cells causes a specific increase in the expression of the key EMT regulators Snail1 and Zeb2, which occurs at both the transcriptional and post-transcriptional levels. Together, our data indicate a novel role of eIF3e/Int6 in the regulation of EMT in breast epithelial cells and support a tumor suppressor role of eIF3e/Int6.
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13
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Neusiedler J, Mocquet V, Limousin T, Ohlmann T, Morris C, Jalinot P. INT6 interacts with MIF4GD/SLIP1 and is necessary for efficient histone mRNA translation. RNA (NEW YORK, N.Y.) 2012; 18:1163-1177. [PMID: 22532700 PMCID: PMC3358639 DOI: 10.1261/rna.032631.112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 03/06/2012] [Indexed: 05/31/2023]
Abstract
The INT6/EIF3E protein has been implicated in mouse and human breast carcinogenesis. This subunit of the eIF3 translation initiation factor that includes a PCI domain exhibits specific features such as presence in the nucleus and ability to interact with other important cellular protein complexes like the 26S proteasome and the COP9 signalosome. It has been previously shown that INT6 was not essential for bulk translation, and this protein is considered to regulate expression of specific mRNAs. Based on the results of a two-hybrid screen performed with INT6 as bait, we characterize in this article the MIF4GD/SLIP1 protein as an interactor of this eIF3 subunit. MIF4GD was previously shown to associate with SLBP, which binds the stem-loop located at the 3' end of the histone mRNAs, and to be necessary for efficient translation of these cell cycle-regulated mRNAs that lack a poly(A) tail. In line with the interaction of both proteins, we show using the RNA interference approach that INT6 is also essential to S-phase histone mRNA translation. This was observed by analyzing expression of endogenous histones and by testing heterologous constructs placing the luciferase reporter gene under the control of the stem-loop element of various histone genes. With such a reporter plasmid, silencing and overexpression of INT6 exerted opposite effects. In agreement with these results, INT6 and MIF4GD were observed to colocalize in cytoplasmic foci. We conclude from these data that INT6, by establishing interactions with MIF4GD and SLBP, plays an important role in translation of poly(A) minus histone mRNAs.
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Affiliation(s)
- Julia Neusiedler
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Vincent Mocquet
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Taran Limousin
- Virologie Humaine, Unité 758, Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Theophile Ohlmann
- Virologie Humaine, Unité 758, Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Christelle Morris
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Pierre Jalinot
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
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14
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Abstract
Proteasome is a highly organized protease complex comprising a catalytic 20S core particle (CP) and two 19S regulatory particles (RP), which together form the 26S structure. The 26S proteasome is responsible for the degradation of most ubiquitylated proteins through a multistep process involving recognition of the polyubiquitin chain, unfolding of the substrate, and translocation of the substrate into the active site in the cavity of the CP. Recent studies have shed light on various aspects of the complex functions of the 26S proteasome. In addition, the recent identification of various proteasome-dedicated chaperones indicates that the assembly pathways of the RP and CP are multistep processes. In this review, we summarize recent advances in the understanding of the proteasome structure, function, and assembly.
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15
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Andersen KM, Jensen C, Kriegenburg F, Lauridsen AMB, Gordon C, Hartmann-Petersen R. Txl1 and Txc1 are co-factors of the 26S proteasome in fission yeast. Antioxid Redox Signal 2011; 14:1601-8. [PMID: 21091378 DOI: 10.1089/ars.2010.3329] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The 26S proteasome is a large proteolytic particle present in the cytosol and nucleus of eukaryotic cells. Most intracellular proteins, including those affected by oxidative damage, are degraded by the proteasome. The human thioredoxin, Txnl1, is known to associate with the 26S proteasome and thereby equips proteasomes with redox capabilities. Here, we characterize the fission yeast orthologue of Txnl1, called Txl1. Txl1 associates with the 26S proteasome via its C-terminal domain. This domain is also found in the uncharacterized protein, Txc1, which was also found to interact with 26S proteasomes. A txl1 null mutant, but not a txc1 null, displayed a synthetic growth defect with cut8, encoding a protein that tethers the proteasome to the nuclear membrane. Txc1 is present throughout the cytoplasm and nucleus, whereas Txl1 co-localizes with 26S proteasomes in both wild-type cells and in cut8 mutants, indicating that Txl1 is tightly associated with 26S proteasomes, while Txc1 might be only transiently bound to the complex. Finally, we show that Txl1 is an active thioredoxin. Accordingly, Txl1 was able to reduce and mediate the degradation of an oxidized model proteasome substrate in vitro. Thus, Txl1 and Txc1 are proteasome co-factors connected with oxidative stress.
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16
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Int6 regulates both proteasomal degradation and translation initiation and is critical for proper formation of acini by human mammary epithelium. Oncogene 2010; 30:724-36. [PMID: 20890303 PMCID: PMC3017639 DOI: 10.1038/onc.2010.445] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
INT6/EIF3E has been implicated in breast tumorigenesis, but its functional activities remain poorly defined. We found that repressing INT6 expression induced transformed properties in normal human mammary epithelium (MCF10A); in contrast, Int6 silencing induced apoptosis in HeLa cells. As in yeast, Int6 in human cells was required for assembly of active proteasomes. A reverse phase protein array screen identified SRC3/AIB1 as one oncoprotein whose level and stability increased when Int6 was silenced in MCF10A cells. Our data further show that Int6 binds SRC3 and its ubiquitin ligase Fbw7, thus perhaps mediating the interaction between SRC3-Fbw7 and proteasomes. Consistent with this, Int6 silencing did not increase SRC3 levels in HeLa cells, which have low Fbw7 levels. Surprisingly, however, polyubiquitylated proteins do not accumulate or may even decrease in Int6-silenced cells that contain defective proteasomes. Considering that decreased ubiquitin might explain this observation and that Int6 might control ubiquitin levels in its role as a subunit of eIF3 (eukaryote translation initiation factor), we found that silencing Int6 reduced monoubiquitin protein levels, which correlated with a shift of ubiquitin mRNAs from larger polysomes to non-translating ribosomes. In contrast, levels of many housekeeping proteins did not change. This apparent reduction in the translation of ubiquitin genes correlated with a modest reduction in protein synthesis rate and formation of large polysomes. To further determine whether Int6 can selectively control translation, we analyzed translation of different 5′-UTR reporters and found that indeed, loss of Int6 had differential effects on these reporters. Together the data suggest that Int6 depletion blocks ubiquitin-dependent proteolysis by decreasing both ubiquitin levels and the assembly of functional proteasome machinery, leading to accumulation of oncoproteins such as SRC3 that can transform mammary epithelium. Our data also raise the possibility that Int6 can further fine-tune protein levels by selectively controlling translation of specific mRNAs.
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17
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Choudhuri A, Evans T, Maitra U. Non-core subunit eIF3h of translation initiation factor eIF3 regulates zebrafish embryonic development. Dev Dyn 2010; 239:1632-44. [PMID: 20503360 DOI: 10.1002/dvdy.22289] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Eukaryotic translation initiation factor eIF3, which plays a central role in translation initiation, consists of five core subunits that are present in both the budding yeast and higher eukaryotes. However, higher eukaryotic eIF3 contains additional (non-core) subunits that are absent in the budding yeast. We investigated the role of one such non-core eIF3 subunit eIF3h, encoded by two distinct genes-eif3ha and eif3hb, as a regulator of embryonic development in zebrafish. Both eif3h genes are expressed during early embryogenesis, and display overlapping yet distinct and highly dynamic spatial expression patterns. Loss of function analysis using specific morpholino oligomers indicates that each isoform has specific as well as redundant functions during early development. The morphant phenotypes correlate with their spatial expression patterns, indicating that eif3h regulates development of the brain, heart, vasculature, and lateral line. These results indicate that the non-core subunits of eIF3 regulate specific developmental programs during vertebrate embryogenesis.
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Affiliation(s)
- Avik Choudhuri
- Department of Developmental and Molecular Biology, Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA
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18
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Cabrera R, Sha Z, Vadakkan TJ, Otero J, Kriegenburg F, Hartmann-Petersen R, Dickinson ME, Chang EC. Proteasome nuclear import mediated by Arc3 can influence efficient DNA damage repair and mitosis in Schizosaccharomyces pombe. Mol Biol Cell 2010; 21:3125-36. [PMID: 20668161 PMCID: PMC2938379 DOI: 10.1091/mbc.e10-06-0506] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Proteasomes must efficiently remove their substrates throughout the cells in a timely manner as many of these proteins can be toxic. This study shows that proteasomes can do so efficiently because they are highly mobile. Furthermore this study uncovers that proteasome mobility requires functional Arc3, a subunit of the Arp2/3 complex. Proteasomes must remove regulatory molecules and abnormal proteins throughout the cell, but how proteasomes can do so efficiently remains unclear. We have isolated a subunit of the Arp2/3 complex, Arc3, which binds proteasomes. When overexpressed, Arc3 rescues phenotypes associated with proteasome deficiencies; when its expression is repressed, proteasome deficiencies intensify. Arp2/3 is best known for regulating membrane dynamics and vesicular transport; thus, we performed photobleaching experiments and showed that proteasomes are readily imported into the nucleus but exit the nucleus slowly. Proteasome nuclear import is reduced when Arc3 is inactivated, leading to hypersensitivity to DNA damage and inefficient cyclin-B degradation, two events occurring in the nucleus. These data suggest that proteasomes display Arc3-dependent mobility in the cell, and mobile proteasomes can efficiently access substrates throughout the cell, allowing them to effectively regulate cell-compartment–specific activities.
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Affiliation(s)
- Rodrigo Cabrera
- Department of Molecular and Cellular Biology, Interdepartmental Program of Cell and Molecular Biology, and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030, USA
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19
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Grzmil M, Rzymski T, Milani M, Harris AL, Capper RG, Saunders NJ, Salhan A, Ragoussis J, Norbury CJ. An oncogenic role of eIF3e/INT6 in human breast cancer. Oncogene 2010; 29:4080-9. [PMID: 20453879 DOI: 10.1038/onc.2010.152] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Altered expression of the eukaryotic translation initiation factor 3 (eIF3) subunit eIF3e/INT6 has been described in various types of human cancer, but the nature of its involvement in tumorigenesis is not yet clear. Using immunohistochemical analysis of 81 primary breast cancers, we found that high tumor grade correlated significantly with elevated cytoplasmic eIF3e level in epithelial tumor cells. Analysis of protein synthesis after siRNA-mediated knockdown in breast cancer cell lines indicated that eIF3e is not required for bulk translation. Microarray analysis of total and polysomal RNAs nonetheless identified distinct sets of mRNAs regulated either positively or negatively by eIF3e; functional classification of these revealed a marked enrichment of genes involved in cell proliferation, invasion and apoptosis. Validated mRNA targets regulated positively at the translational level by eIF3e included urokinase-type plasminogen activator and apoptotic regulator BCL-XL, whereas synthesis of proteins including the mitotic checkpoint component MAD2L1 was negatively regulated. Finally, eIF3e-depleted breast carcinoma cells showed reduced in vitro invasion and proliferation. Taken together, our study data suggest that eIF3e has a positive role in breast cancer progression. It regulates the translation, and in some cases abundance, of mRNAs involved in key aspects of cancer cell biology.
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Affiliation(s)
- M Grzmil
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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20
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Salomons FA, Acs K, Dantuma NP. Illuminating the ubiquitin/proteasome system. Exp Cell Res 2010; 316:1289-95. [PMID: 20149791 DOI: 10.1016/j.yexcr.2010.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 02/01/2010] [Indexed: 12/01/2022]
Abstract
The ubiquitin/proteasome system (UPS) is responsible for the regulated processive degradation of proteins residing in the cytosol, nucleus, and endoplasmic reticulum. The two central players are ubiquitin, a small protein that is conjugated to substrates, and the proteasome, a large multi-subunit proteolytic complex that executes degradation of ubiquitylated proteins. Ubiquitylation and proteasomal degradation are highly dynamic processes. During the last decade, many researchers have started taking advantage of fluorescent proteins, which allow studying the dynamic nature of this system in the context of its natural environment: the living cell. In this review, we will summarize studies that have implemented this approach to examine the UPS and discuss novel insights in the dynamic organization of the UPS.
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Affiliation(s)
- Florian A Salomons
- Department of Cell and Molecular Biology, Karolinska Institutet, S-17177 Stockholm, Sweden
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21
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Otero JH, Suo J, Gordon C, Chang EC. Int6 and Moe1 interact with Cdc48 to regulate ERAD and proper chromosome segregation. Cell Cycle 2010; 9:147-61. [PMID: 20016281 DOI: 10.4161/cc.9.1.10312] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Int6/eIF3e is implicated in tumorigenesis, but its molecular functions remain unclear. We have studied its fission yeast homolog Yin6, reporting that it regulates proteolysis by controlling the assembly/localization of proteasomes, and binds directly to another conserved protein, Moe1. In the present study, we isolated Cdc48 as a Moe1-binding protein from a yeast two-hybrid screen, and confirmed biochemically that they form a stable complex in fission yeast. Overexpressing Moe1 or Yin6 partially rescued phenotypes of cdc48 mutants; conversely, overexpressing Cdc48 partially rescued phenotypes of moe1 or yin6 mutants. Mutants defective in both Cdc48 and the Yin6-Moe1 complex showed growth defects that were far more severe than either alone. These double mutants were severely deficient in endoplasmic reticulum associated degradation (ERAD), as they were hypersensitive to accumulation of misfolded proteins. In addition, their chromosomes showed frequent defects in spindle attachment and segregation--these mitotic defects correlated with Ase1 and Bir1/survivin mislocalization. These results suggest that Cdc48, Yin6 and Moe1 act in the same protein complex to concertedly control ERAD and chromosome segregation. Many of these properties are evolutionarily conserved in humans, since human Cdc48 rescued the lethality of the yeast cdc48Delta mutant, and Int6 and Moe1/eIF3d bind Cdc48 in human cells.
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Affiliation(s)
- Joel H Otero
- Interdepartmental Program in Cell and Molecular Biology, and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX, USA
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22
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Schwechheimer C, Isono E. The COP9 signalosome and its role in plant development. Eur J Cell Biol 2009; 89:157-62. [PMID: 20036030 DOI: 10.1016/j.ejcb.2009.11.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The COP9 signalosome (CSN) is an evolutionarily conserved multiprotein complex with a role in the regulation of cullin-RING type E3 ubiquitin ligases (CRLs). CSN exerts its function on E3 ligases by deconjugating the ubiquitin-related protein NEDD8 from the CRL cullin subunit. Thereby, CSN has an impact on multiple CRL-dependent processes. In recent years, advances have been made in understanding the structural organisation and biochemical function of CSN: Crystal structure analysis and mass spectrometry-assisted studies have come up with first models of the pair-wise and complex interactions of the 8 CSN subunits. Based on the analysis of mutant phenotypes, it can now be taken as an accepted fact that--at least in plants--the major biochemical function of CSN resides in its deneddylation activity, which is mediated by CSN subunit 5 (CSN5). Furthermore, it could be demonstrated that CSN function and deneddylation are required but not essential for CRL-mediated processes, and models for the role of neddylation and deneddylation in controlling CRL activity are emerging. Significant advances have also been made in identifying pathways that are growth restricting in the Arabidopsis csn mutants. Recently it has been shown that a G2 phase arrest, possibly due to genomic instability, restricts growth in Arabidopsis csn mutants. This review provides an update on recent advances in understanding CSN structure and function and summarises the current knowledge on its role in plant development and cell cycle progression.
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Affiliation(s)
- Claus Schwechheimer
- Department of Developmental Genetics, Center for Plant Molecular Biology, University of Tübingen, Tübingen, Germany.
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23
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Sha Z, Brill LM, Cabrera R, Kleifeld O, Scheliga JS, Glickman MH, Chang EC, Wolf DA. The eIF3 interactome reveals the translasome, a supercomplex linking protein synthesis and degradation machineries. Mol Cell 2009; 36:141-52. [PMID: 19818717 PMCID: PMC2789680 DOI: 10.1016/j.molcel.2009.09.026] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 06/23/2009] [Accepted: 09/11/2009] [Indexed: 01/18/2023]
Abstract
eIF3 promotes translation initiation, but relatively little is known about its full range of activities in the cell. Here, we employed affinity purification and highly sensitive LC-MS/MS to decipher the fission yeast eIF3 interactome, which was found to contain 230 proteins. eIF3 assembles into a large supercomplex, the translasome, which contains elongation factors, tRNA synthetases, 40S and 60S ribosomal proteins, chaperones, and the proteasome. eIF3 also associates with ribosome biogenesis factors and the importins-beta Kap123p and Sal3p. Our genetic data indicated that the binding to both importins-beta is essential for cell growth, and photobleaching experiments revealed a critical role for Sal3p in the nuclear import of one of the translasome constituents, the proteasome. Our data reveal the breadth of the eIF3 interactome and suggest that factors involved in translation initiation, ribosome biogenesis, translation elongation, quality control, and transport are physically linked to facilitate efficient protein synthesis.
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Affiliation(s)
- Zhe Sha
- 1 Baylor Plaza, Molecular and Cellular Biology Department, Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030
| | - Laurence M. Brill
- Burnham Institute for Medical Research, Signal Transduction Program, NCI Cancer Center Proteomics Facility, 10901 North Torrey Pines Road, La Jolla, CA 92037
| | - Rodrigo Cabrera
- 1 Baylor Plaza, Molecular and Cellular Biology Department, Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030
| | - Oded Kleifeld
- Department of Biology, Technion - Israel Institute of Technology, 32000 Haifa Israel
| | - Judith S. Scheliga
- Burnham Institute for Medical Research, Signal Transduction Program, NCI Cancer Center Proteomics Facility, 10901 North Torrey Pines Road, La Jolla, CA 92037
| | - Michael H. Glickman
- Department of Biology, Technion - Israel Institute of Technology, 32000 Haifa Israel
| | - Eric C. Chang
- 1 Baylor Plaza, Molecular and Cellular Biology Department, Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030
| | - Dieter A. Wolf
- Burnham Institute for Medical Research, Signal Transduction Program, NCI Cancer Center Proteomics Facility, 10901 North Torrey Pines Road, La Jolla, CA 92037
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Genome-wide screen of genes required for caffeine tolerance in fission yeast. PLoS One 2009; 4:e6619. [PMID: 19672306 PMCID: PMC2720375 DOI: 10.1371/journal.pone.0006619] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Accepted: 07/09/2009] [Indexed: 11/19/2022] Open
Abstract
Background An excess of caffeine is cytotoxic to all eukaryotic cell types. We aim to study how cells become tolerant to a toxic dose of this drug, and the relationship between caffeine and oxidative stress pathways. Methodology/Principal Findings We searched for Schizosaccharomyces pombe mutants with inhibited growth on caffeine-containing plates. We screened a collection of 2,700 haploid mutant cells, of which 98 were sensitive to caffeine. The genes mutated in these sensitive clones were involved in a number of cellular roles including the H2O2-induced Pap1 and Sty1 stress pathways, the integrity and calcineurin pathways, cell morphology and chromatin remodeling. We have investigated the role of the oxidative stress pathways in sensing and promoting survival to caffeine. The Pap1 and the Sty1 pathways are both required for normal tolerance to caffeine, but only the Sty1 pathway is activated by the drug. Cells lacking Pap1 are sensitive to caffeine due to the decreased expression of the efflux pump Hba2. Indeed, ?hba2 cells are sensitive to caffeine, and constitutive activation of the Pap1 pathway enhances resistance to caffeine in an Hba2-dependent manner. Conclusions/Significance With our caffeine-sensitive, genome-wide screen of an S. pombe deletion collection, we have demonstrated the importance of some oxidative stress pathway components on wild-type tolerance to the drug.
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Marques AJ, Palanimurugan R, Matias AC, Ramos PC, Dohmen RJ. Catalytic mechanism and assembly of the proteasome. Chem Rev 2009; 109:1509-36. [PMID: 19265443 DOI: 10.1021/cr8004857] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- António J Marques
- Institute for Genetics, University of Cologne, Zulpicher Strasse 47, D-50674 Cologne, Germany
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Ma C, Yoshioka M, Boivin A, Gan L, Takase Y, Labrie F, St-Amand J. Atlas of dihydrotestosterone actions on the transcriptome of prostate in vivo. Prostate 2009; 69:293-316. [PMID: 19023869 DOI: 10.1002/pros.20883] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Using serial analysis of gene expression (SAGE), we studied the transcriptomic changes in vivo by dihydrotestosterone (DHT) treatment in mice to better understand androgen effects in the prostate. METHODS Approximately 872,000 SAGE tags were isolated from intact and castrated (GDX) mice with and without DHT injection. RESULTS GDX significantly altered 431 transcripts, including 110 transcripts restored by DHT, and 146 potentially new transcripts. Totally, 187 transcripts were significantly affected by DHT treatment, of which 124 were induced and 63 were repressed. Interestingly and consistent with the prostate's secretory role, DHT up-regulated the expression of many genes involved in various steps of protein metabolism such as synthesis, folding, and secretion. GDX modulated the expression of genes which induce cell apoptosis and inhibit cell proliferation through polyamine biosynthesis, retinoid X receptor actions as well as several signaling pathways and some related factors. These results clarify DHT effects on prostate transcriptome in the areas of protein metabolism, cell proliferation and apoptosis. In addition, we detected gene expression changes in metabolic pathways, cytoskeleton, immunity and endoplasmic reticulum stress. Furthermore, knockdown of S-adenosylmethionine decarboxylase 1 in LNCaP cells confirmed the importance of androgen-regulated genes (ARGs) in prostate cancer cell growth. CONCLUSION Our data support the idea that ARGs are essential for the normal development of the prostate and can also be responsible for the pathogenesis of the prostate cancer.
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Affiliation(s)
- Ci Ma
- Department of Anatomy and Physiology, Molecular Endocrinology and Oncology Research Center, Laval University Medical Center, Laval University, Québec, Canada
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27
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Murata S, Yashiroda H, Tanaka K. Molecular mechanisms of proteasome assembly. Nat Rev Mol Cell Biol 2009; 10:104-15. [DOI: 10.1038/nrm2630] [Citation(s) in RCA: 400] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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28
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Establishing new sites of polarization by microtubules. Curr Biol 2009; 19:83-94. [PMID: 19147354 DOI: 10.1016/j.cub.2008.12.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 12/03/2008] [Accepted: 12/04/2008] [Indexed: 11/21/2022]
Abstract
BACKGROUND Microtubules (MTs) participate in the spatial regulation of actin-based processes such as cytokinesis and cell polarization. The fission yeast Schizosaccharomyces pombe is a rod-shaped cell that exhibits polarized cell growth at cell tips. MT plus ends contact and shrink from the cell tips and contribute to polarity regulation. RESULTS Here, we investigate the effects of changing cell shape on MTs and cell-polarization machinery. We physically bend fission yeast cells by forcing them into microfabricated femtoliter chambers. In these bent cells, MTs maintain a straight axis and contact and shrink from cortical sites at the sides of cells. At these ectopic sites, polarity factors such as bud6p, for3p (formin), and cdc42p are recruited and assemble actin cables in a MT-dependent manner. MT contact at the cortex induces the appearance of a bud6p dot within seconds. The accumulation of polarity factors leads to cell growth at these sites, when the MT-associated polarity factor tea1p is absent. This process is dependent on MTs, mal3p (EB1), moe1p (an EB1-binding protein), and for3p but, surprisingly, is independent of the tea1p-tea4p pathway. CONCLUSIONS These studies provide a direct demonstration for how MTs induce actin assembly at specific locations on the cell cortex and begin to identify a new pathway involved in this process. MT interactions with the cortex may be regulated by cortical-attachment sites. These findings highlight the crosstalk between cell shape, polarity mechanisms, and MTs responsible for cell morphogenesis.
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Ray A, Bandyopadhyay A, Matsumoto T, Deng H, Maitra U. Fission yeast translation initiation factor 3 subunit eIF3h is not essential for global translation initiation, but deletion of eif3h+ affects spore formation. Yeast 2009; 25:809-23. [PMID: 19061185 DOI: 10.1002/yea.1635] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe homologue of the p40/eIF3h subunit of mammalian translation initiation factor eIF3 has been characterized in this study. We show that this protein physically associates with the 40S ribosomal particles as a constituent of the multimeric eIF3 protein complex, which consists of all five known eIF3 core subunits (eIF3a, eIF3b, eIF3c, eIF3g and eIF3i) as well as the five non-core subunits (eIF3d, eIF3e, eIF3f, eIF3h and eIF3m) that constitute an eIF3 holocomplex in fission yeast. However, affinity purification of eIF3 from fission yeast cells expressing TAP-tagged eIF3h suggests the presence of distinct forms of eIF3 that differ in their composition of the non-core subunits. Further characterization of eIF3h shows that strains lacking eif3h(+) (eif3hDelta) are viable and show no gross defects, either in vegetative growth or in the rate of in vivo protein synthesis. Polysome profile analysis shows no apparent defects in translation initiation. Furthermore, deletion of eif3h(+) does not affect the ability of the other eIF3 subunits to remain associated with one another in a tight protein complex similar to the situation in wild-type cells. Additionally, we show that human eIF3h can functionally substitute fission yeast eIF3h in complementing in vivo a genetic deletion of eif3h(+). Interestingly, mutant eif3hDelta cells show several prominent phenotypic properties. They are hypersensitive to caffeine and highly defective in meiosis, producing either no spores or incomplete tetrads with a very high frequency. The implications of these results in relation to the functions of eIF3h in Sz. pombe are discussed.
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Affiliation(s)
- Anirban Ray
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York, NY 10461, USA
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Transcriptome analysis and identification of regulators for long-term plasticity in Aplysia kurodai. Proc Natl Acad Sci U S A 2008; 105:18602-7. [PMID: 19017802 DOI: 10.1073/pnas.0808893105] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The marine mollusk Aplysia is a useful model organism for studying the cellular bases of behavior and plasticity. However, molecular studies of Aplysia have been limited by the lack of genomic information. Recently, a large scale characterization of neuronal transcripts was performed in A. californica. Here, we report the analysis of a parallel set of neuronal transcripts from a closely related species A. kurodai found in the northwestern Pacific. We collected 4,859 nonredundant sequences from the nervous system tissue of A. kurodai. By performing microarray and real-time PCR analyses, we found that ApC/EBP, matrilin, antistasin, and eIF3e clones were significantly up-regulated and a BAT1 homologous clone was significantly down-regulated by 5-HT treatment. Among these, we further demonstrated that the Ap-eIF3e plays a key role in 5-HT-induced long-term facilitation (LTF) as a positive regulator.
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Dessau M, Halimi Y, Erez T, Chomsky-Hecht O, Chamovitz DA, Hirsch JA. The Arabidopsis COP9 signalosome subunit 7 is a model PCI domain protein with subdomains involved in COP9 signalosome assembly. THE PLANT CELL 2008; 20:2815-34. [PMID: 18854373 PMCID: PMC2590729 DOI: 10.1105/tpc.107.053801] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 09/09/2008] [Accepted: 09/28/2008] [Indexed: 05/21/2023]
Abstract
The COP9 Signalosome (CSN) is a multiprotein complex that was originally identified in Arabidopsis thaliana as a negative regulator of photomorphogenesis and subsequently shown to be a general eukaryotic regulator of developmental signaling. The CSN plays various roles, but it has been most often implicated in regulating protein degradation pathways. Six of eight CSN subunits bear a sequence motif called PCI. Here, we report studies of subunit 7 (CSN7) from Arabidopsis, which contains such a motif. Our in vitro and structural results, based on 1.5 A crystallographic data, enable a definition of a PCI domain, built from helical bundle and winged helix subdomains. Using functional binding assays, we demonstrate that the PCI domain (residues 1 to 169) interacts with two other PCI proteins, CSN8 and CSN1. CSN7 interactions with CSN8 use both PCI subdomains. Furthermore, we show that a C-terminal tail outside of this PCI domain is responsible for association with the non-PCI subunit, CSN6. In vivo studies of transgenic plants revealed that the overexpressed CSN7 PCI domain does not assemble into the CSN, nor can it complement a null mutation of CSN7. However, a CSN7 clone that contains the PCI domain plus part of the CSN6 binding domain can complement the null mutation in terms of seedling viability and photomorphogenesis. These transgenic plants, though, are defective in adult growth, suggesting that the CSN7 C-terminal tail plays additional functional roles. Together, the findings have implications for CSN assembly and function, highlighting necessary interactions between subunits.
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Affiliation(s)
- Moshe Dessau
- Department of Biochemistry, Daniella Rich Institute for Structural Biology, Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel
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Udagawa T, Nemoto N, Wilkinson CRM, Narashimhan J, Jiang L, Watt S, Zook A, Jones N, Wek RC, Bähler J, Asano K. Int6/eIF3e promotes general translation and Atf1 abundance to modulate Sty1 MAPK-dependent stress response in fission yeast. J Biol Chem 2008; 283:22063-75. [PMID: 18502752 PMCID: PMC2494926 DOI: 10.1074/jbc.m710017200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 05/22/2008] [Indexed: 11/06/2022] Open
Abstract
int-6 is one of the frequent integration sites for mouse mammary tumor viruses. Although its product is the e-subunit of translation initiation factor eIF3, other evidence indicates that it interacts with proteasomes or other proteins to regulate protein stability. Here we report that the fission yeast int6(+) is required for overcoming stress imposed by histidine starvation, using the drug 3-aminotriazole (3AT). Microarray and complementary Northern studies using wild-type, int6Delta or gcn2Delta mutants indicate that 3AT-treated wild-type yeast induces core environmental stress response (CESR) genes in addition to typical general amino acid control (GAAC) genes whose transcription depends on the eIF2 kinase, Gcn2. In agreement with this, Sty1 MAPK and its target transcription factor Atf1, which signal the CESR, are required for overcoming 3AT-induced starvation. We find that Int6 is required for maintaining the basal level of Atf1 and for rapid transcriptional activation of the CESR on 3AT-insult. Pulse labeling experiments indicate that int6Delta significantly slows down de novo protein synthesis. Moreover, Atf1 protein half-life was reduced in int6Delta cells. These effects would account for the compromised Atf1 activity on 3AT-induced stress. Thus, the robust protein synthesis promoted by intact eIF3 appears to be a part of the requisites for sound Sty1 MAPK-dependent signaling governed by the activity of the Atf1 transcription factor.
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Affiliation(s)
- Tsuyoshi Udagawa
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, Kansas 66506, USA
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Paz-Aviram T, Yahalom A, Chamovitz DA. Arabidopsis eIF3e interacts with subunits of the ribosome, Cop9 signalosome and proteasome. PLANT SIGNALING & BEHAVIOR 2008; 3:409-11. [PMID: 19704582 PMCID: PMC2634318 DOI: 10.4161/psb.3.6.5434] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Accepted: 12/17/2007] [Indexed: 05/08/2023]
Abstract
The roles of individual Eukaryotic translation Initiation Factor 3 (eIF3) subunits are largely unclear. Though some are essential, while others are thought to have regulatory roles. The "e" subunit, also known as Int-6, is a candidate for a regulatory subunit as it is not essential for translation initiation in yeasts. To further elucidate the roles of eIF3e, we have employed an interaction-trap screen using the yeast two-hybrid system. eIF3e interacts in yeast with subunits of the ribosome, COP9 signalosome and 26S proteasome. These interactions mesh well with our recent results which showed that eIF3e is degraded in a CSN-dependent, proteasome-dependent fashion, and inhibits translation when present in excess.
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Affiliation(s)
- Tal Paz-Aviram
- Department of Plant Sciences; Tel Aviv University; Tel Aviv, Israel
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Rencus-Lazar S, Amir Y, Wu J, Chien CT, Chamovitz DA, Segal D. The proto-oncogene Int6 is essential for neddylation of Cul1 and Cul3 in Drosophila. PLoS One 2008; 3:e2239. [PMID: 18493598 PMCID: PMC2375110 DOI: 10.1371/journal.pone.0002239] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Accepted: 04/04/2008] [Indexed: 11/24/2022] Open
Abstract
Int6 is a proto-oncogene implicated in various types of cancer, but the mechanisms underlying its activity are not clear. Int6 encodes a subunit of the eukaryotic translation initiation factor 3, and interacts with two related complexes, the proteasome, whose activity is regulated by Int6 in S. pombe, and the COP9 signalosome. The COP9 signalosome regulates the activity of Cullin-Ring Ubiquitin Ligases via deneddylation of their cullin subunit. We report here the generation and analysis of two Drosophila mutants in Int6. The mutants are lethal demonstrating that Int6 is an essential gene. The mutant larvae accumulate high levels of non-neddylated Cul1, suggesting that Int6 is a positive regulator of cullin neddylation. Overexpression in Int6 in cell culture leads to accumulation of neddylated cullins, further supporting a positive role for Int6 in regulating neddylation. Thus Int6 and the COP9 signalosome play opposing roles in regulation of cullin neddylation.
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Affiliation(s)
- Sigal Rencus-Lazar
- Department of Molecular Microbiology, Tel Aviv University, Tel Aviv, Israel
- Department of Biotechnology, Tel Aviv University, Tel Aviv, Israel
| | - Yaniv Amir
- Department of Molecular Microbiology, Tel Aviv University, Tel Aviv, Israel
- Department of Biotechnology, Tel Aviv University, Tel Aviv, Israel
| | - Junetai Wu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | | | - Daniel A. Chamovitz
- Department of Plant Sciences, Tel Aviv University, Tel Aviv, Israel
- * E-mail: (DC); (DS)
| | - Daniel Segal
- Department of Molecular Microbiology, Tel Aviv University, Tel Aviv, Israel
- Department of Biotechnology, Tel Aviv University, Tel Aviv, Israel
- * E-mail: (DC); (DS)
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Ralston SH. Juvenile Paget's disease, familial expansile osteolysis and other genetic osteolytic disorders. Best Pract Res Clin Rheumatol 2008; 22:101-11. [DOI: 10.1016/j.berh.2007.11.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Yahalom A, Kim TH, Roy B, Singer R, von Arnim AG, Chamovitz DA. Arabidopsis eIF3e is regulated by the COP9 signalosome and has an impact on development and protein translation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 53:300-11. [PMID: 18067529 DOI: 10.1111/j.1365-313x.2007.03347.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The roles of individual eukaryotic translation initiation factor 3 (eIF3) subunits are largely unclear, although some are essential, while others are thought to have regulatory roles. The 'e' subunit, also known as Int-6/Int6, is a candidate for a regulatory subunit as it is not essential for translation initiation in yeasts. eIF3e associates with the COP9 signalosome, and localizes to the nucleus in certain tissues. To further elucidate the roles of eIF3e, we have taken a genetic approach using Arabidopsis as a model system. Overexpression of eIF3e results in defects similar to mutations in the COP9 signalosome. eIF3e protein, but not transcript, over accumulates in csn mutants, and eIF3e is degraded in a proteasome-dependent fashion. In vitro and in vivo assays suggest that excess eIF3e inhibits translation. We conclude that the COP9 signalosome maintains a precise regulation of eIF3e levels, which is necessary for normal development in Arabidopsis.
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Affiliation(s)
- Avital Yahalom
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Sha Z, Yen HCS, Scheel H, Suo J, Hofmann K, Chang EC. Isolation of the Schizosaccharomyces pombe proteasome subunit Rpn7 and a structure-function study of the proteasome-COP9-initiation factor domain. J Biol Chem 2007; 282:32414-23. [PMID: 17761670 PMCID: PMC3012426 DOI: 10.1074/jbc.m706276200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proper assembly of the 26 S proteasome is required to efficiently degrade polyubiquitinated proteins. Many proteasome subunits contain the proteasome-COP9-initiation factor (PCI) domain, thus raising the possibility that the PCI domain may play a role in mediating proteasome assembly. We have previously characterized the PCI protein Yin6, a fission yeast ortholog of the mammalian Int6 that has been implicated in breast oncogenesis, and demonstrated that it binds and regulates the assembly of the proteasome. In this study, we isolated another PCI proteasome subunit, Rpn7, as a high copy suppressor that rescued the proteasome defects in yin6 null cells. To better define the function of the PCI domain, we aligned protein sequences to identify a conserved leucine residue that is present in nearly all known PCI domains. Replacing it with aspartate in yeast Rpn7, Yin6, and Rpn5 inactivated these proteins, and mutant human Int6 mislocalized in HeLa cells. Rpn7 and Rpn5 bind Rpn9 with high affinity, but their mutant versions do not. Our data suggest that this leucine may interact with several hydrophobic amino acid residues to influence the spatial arrangement either within the N-terminal tandem alpha-helical repeats or between these repeats and the more C-terminal winged helix subdomain. Disruption of such an arrangement in the PCI domain may substantially inactivate many PCI proteins and block their binding to other proteins.
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Affiliation(s)
- Zhe Sha
- Department of Molecular and Cell Biology, The Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA
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Morris C, Wittmann J, Jäck HM, Jalinot P. Human INT6/eIF3e is required for nonsense-mediated mRNA decay. EMBO Rep 2007; 8:596-602. [PMID: 17468741 PMCID: PMC2002529 DOI: 10.1038/sj.embor.7400955] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 02/20/2007] [Accepted: 03/01/2007] [Indexed: 11/08/2022] Open
Abstract
The mammalian integration site 6 (INT6) protein has been implicated in breast carcinogenesis and characterized as the eIF3e non-core subunit of the translation initiation factor eIF3, but its role in this complex is not known. Here, we show that INT6 knockdown by RNA interference strongly inhibits nonsense-mediated messenger RNA decay (NMD), which triggers degradation of mRNAs with premature stop codons. In contrast to the eIF3b core subunit, which is required for both NMD and general translation, INT6 is only necessary for the former process. Consistent with such a role, immunoprecipitation experiments showed that INT6 co-purifies with CBP80 and the NMD factor UPF2. In addition, several transcripts known to be upregulated by UPF1 or UPF2 depletion were also found to be sensitive to INT6 suppression. From these observations, we propose that INT6, in association with eIF3, is involved in routing specific mRNAs for degradation.
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Affiliation(s)
- Christelle Morris
- LBMC, UMR5239 CNRS-ENS de Lyon, IFR 128 Biosciences Lyon Gerland, 46 Allée d'Italie, 69364 Lyon cedex 07, France
| | - Jürgen Wittmann
- Division of Molecular Immunology, Department of Internal Medicine 3, Nikolaus-Fiebiger-Center, University of Erlangen-Nürnberg, Gluckstrasse 6, D-91054 Erlangen, Germany
| | - Hans-Martin Jäck
- Division of Molecular Immunology, Department of Internal Medicine 3, Nikolaus-Fiebiger-Center, University of Erlangen-Nürnberg, Gluckstrasse 6, D-91054 Erlangen, Germany
| | - Pierre Jalinot
- LBMC, UMR5239 CNRS-ENS de Lyon, IFR 128 Biosciences Lyon Gerland, 46 Allée d'Italie, 69364 Lyon cedex 07, France
- Tel: +33 4 7272 8563; Fax: +33 4 7272 8080; E-mail:
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Luke-Glaser S, Roy M, Larsen B, Le Bihan T, Metalnikov P, Tyers M, Peter M, Pintard L. CIF-1, a shared subunit of the COP9/signalosome and eukaryotic initiation factor 3 complexes, regulates MEL-26 levels in the Caenorhabditis elegans embryo. Mol Cell Biol 2007; 27:4526-40. [PMID: 17403899 PMCID: PMC1900047 DOI: 10.1128/mcb.01724-06] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The COP9/signalosome (CSN) is an evolutionarily conserved macromolecular complex that regulates the cullin-RING ligase (CRL) class of E3 ubiquitin ligases, primarily by removing the ubiquitin-like protein Nedd8 from the cullin subunit. In the Caenorhabditis elegans embryo, the CSN controls the degradation of the microtubule-severing protein MEI-1 through CUL-3 deneddylation. However, the molecular mechanisms of CSN function and its subunit composition remain to be elucidated. Here, using a proteomic approach, we have characterized the CSN and CUL-3 complexes from C. elegans embryos. We show that the CSN physically interacts with the CUL-3-based CRL and regulates its activity by counteracting the autocatalytic instability of the substrate-specific adaptor MEL-26. Importantly, we identified the uncharacterized protein K08F11.3/CIF-1 (for CSN-eukaryotic initiation factor 3 [eIF3]) as a stoichiometric and functionally important subunit of the CSN complex. CIF-1 appears to be the only ortholog of Csn7 encoded by the C. elegans genome, but it also exhibits extensive sequence similarity to eIF3m family members, which are required for the initiation of protein translation. Indeed, CIF-1 binds eIF-3.F and inactivation of cif-1 impairs translation in vivo. Taken together, our results indicate that CIF-1 is a shared subunit of the CSN and eIF3 complexes and may therefore link protein translation and degradation.
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Affiliation(s)
- Sarah Luke-Glaser
- Swiss Federal Institute of Technology, Zurich, Institute of Biochemistry, Zurich, Switzerland
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Traicoff JL, Chung JY, Braunschweig T, Mazo I, Shu Y, Ramesh A, D'Amico MW, Galperin MM, Knezevic V, Hewitt SM. Expression of EIF3-p48/INT6, TID1 and Patched in cancer, a profiling of multiple tumor types and correlation of expression. J Biomed Sci 2007; 14:395-405. [PMID: 17385060 DOI: 10.1007/s11373-007-9149-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 12/21/2006] [Indexed: 10/23/2022] Open
Abstract
Alterations in eIF3-p48/INT6 gene expression have been implicated in murine and human mammary carcinogenesis. We examined levels of INT6 protein in human tumors and determined that breast and colon tumors clustered into distinct groups based on levels of INT6 expression and clinicopathological variables. We performed multiplex tissue immunoblotting of breast, colon, lung, and ovarian tumor tissues and found that INT6 protein levels positively correlated with those of TID1, Patched, p53, c-Jun, and phosphorylated-c-Jun proteins in a tissue-specific manner. INT6 and TID1 showed significant positive correlation in all tissue types tested. These findings were confirmed by immunohistochemical staining of INT6 and TID1. Further evidence supporting a cooperative role for INT6 and TID1 is the presence of endogenous INT6 and TID1 proteins as complexes. We detected co-immunoprecipitation between INT6 and TID1, as well as between INT6 and Patched. These findings suggest potential integrated roles for INT6, TID1, and Patched proteins in cell growth, development, and tumorigenesis. Additionally, these data suggest that the combination of INT6, TID1, and Patched protein levels may be useful biomarkers for the development of diagnostic assays.
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41
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García P, Tajadura V, García I, Sánchez Y. Role of Rho GTPases and Rho-GEFs in the regulation of cell shape and integrity in fission yeast. Yeast 2007; 23:1031-43. [PMID: 17072882 DOI: 10.1002/yea.1409] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The Rho family of GTPases are highly conserved molecular switches that control some of the most fundamental processes of cell biology, including morphogenesis, vesicular transport, cell division and motility. Guanine nucleotide-exchange factors (GEFs) are directly responsible for the activation of Rho-family GTPases in response to extracellular stimuli. In fission yeast, there are seven Dbl-related GEFs and they activate six Rho-type GTPases within a particular spatio-temporal context. The failure to do so might have consequences reflected in aberrant phenotypes and in some cases lead to cell death. In this review, we briefly summarize the role of Rho GTPases and Rho-GEFs in the establishment and maintenance of cell polarity and cell integrity in Schizosaccharomyces pombe.
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Affiliation(s)
- Patricia García
- Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca and Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain
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42
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Buchsbaum S, Morris C, Bochard V, Jalinot P. Human INT6 interacts with MCM7 and regulates its stability during S phase of the cell cycle. Oncogene 2007; 26:5132-44. [PMID: 17310990 DOI: 10.1038/sj.onc.1210314] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mouse int6 gene is a frequent integration site of the mouse mammary tumor virus and INT6 silencing by RNA interference in HeLa cells causes an increased number of cells in the G2/M phases of the cell cycle, along with mitotic defects. In this report, we investigated the functional significance of the interaction between INT6 and MCM7, which was observed in a two-hybrid screen performed with INT6 as bait. It was found that proteasome inhibition strengthens interaction between both proteins and that INT6 stabilizes MCM7. Removal of MCM7 from chromatin as replication proceeds was accelerated in INT6-silenced cells and reduced amounts of protein were transiently observed, followed by a correction resulting from stimulation of mcm7 gene expression. Synchronized cells depleted for either INT6 or MCM7 display a reduction in thymidine incorporation and a reinforced association of RPA and claspin with chromatin. These data show that INT6 stabilizes chromatin-bound MCM7 and that alteration of this effect is associated with replication deficiency.
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Affiliation(s)
- S Buchsbaum
- Laboratoire de Biologie Moléculaire de la Cellule, UMR5161 CNRS/ENS de Lyon, IFR 128 Biosciences Lyon Gerland, Lyon cedex 07, Rhone, France
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43
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Isono E, Nishihara K, Saeki Y, Yashiroda H, Kamata N, Ge L, Ueda T, Kikuchi Y, Tanaka K, Nakano A, Toh-e A. The assembly pathway of the 19S regulatory particle of the yeast 26S proteasome. Mol Biol Cell 2007; 18:569-80. [PMID: 17135287 PMCID: PMC1783769 DOI: 10.1091/mbc.e06-07-0635] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 11/13/2006] [Accepted: 11/20/2006] [Indexed: 12/13/2022] Open
Abstract
The 26S proteasome consists of the 20S proteasome (core particle) and the 19S regulatory particle made of the base and lid substructures, and it is mainly localized in the nucleus in yeast. To examine how and where this huge enzyme complex is assembled, we performed biochemical and microscopic characterization of proteasomes produced in two lid mutants, rpn5-1 and rpn7-3, and a base mutant DeltaN rpn2, of the yeast Saccharomyces cerevisiae. We found that, although lid formation was abolished in rpn5-1 mutant cells at the restrictive temperature, an apparently intact base was produced and localized in the nucleus. In contrast, in DeltaN rpn2 cells, a free lid was formed and localized in the nucleus even at the restrictive temperature. These results indicate that the modules of the 26S proteasome, namely, the core particle, base, and lid, can be formed and imported into the nucleus independently of each other. Based on these observations, we propose a model for the assembly process of the yeast 26S proteasome.
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Affiliation(s)
- Erika Isono
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
- Entwicklungsgenetik, ZMBP, University of Tübingen, D-72076 Tübingen, Germany
| | - Kiyoshi Nishihara
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Yasushi Saeki
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Hideki Yashiroda
- Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan; and
| | - Naoko Kamata
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Liying Ge
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Takashi Ueda
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Yoshiko Kikuchi
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Keiji Tanaka
- Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan; and
| | - Akihiko Nakano
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
- RIKEN Discovery Research Institute, Saitama 351-0198, Japan
| | - Akio Toh-e
- *Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
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44
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Kearsey SE, Stevenson AL, Toda T, Wang SW. Fission yeast Cut8 is required for the repair of DNA double-strand breaks, ribosomal DNA maintenance, and cell survival in the absence of Rqh1 helicase. Mol Cell Biol 2006; 27:1558-67. [PMID: 17178839 PMCID: PMC1820446 DOI: 10.1128/mcb.01495-06] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Schizosaccharomyces pombe Rqh1 is a member of the RecQ DNA helicase family. Members of this protein family are mutated in cancer predisposition diseases, causing Bloom's, Werner, and Rothmund-Thomson syndromes. Rqh1 forms a complex with topoisomerase III and is proposed to process or disrupt aberrant recombination structures that arise during S phase to allow proper chromosome segregation during mitosis. Intriguingly, in the absence of Rqh1, processing of these structures appears to be dependent on Rad3 (human ATR) in a manner that is distinct from its role in checkpoint control. Here, we show that rad3 rqh1 mutants are normally committed to a lethal pathway of DNA repair requiring homologous recombination, but blocking this pathway by Rhp51 inactivation restores viability. Remarkably, viability is also restored by overexpression of Cut8, a nuclear envelope protein involved in tethering and proper function of the proteasome. In keeping with a recently described function of the proteasome in the repair of DNA double-strand breaks, we found that Cut8 is also required for DNA double-strand break repair and is essential for proper chromosome segregation in the absence of Rqh1, suggesting that these proteins might function in a common pathway in homologous recombination repair to ensure accurate nuclear division in S. pombe.
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Affiliation(s)
- Stephen E Kearsey
- Department of Zoology, South Parks Road, Oxford OX1 3PS, United Kingdom.
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45
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Zhang L, Pan X, Hershey JWB. Individual overexpression of five subunits of human translation initiation factor eIF3 promotes malignant transformation of immortal fibroblast cells. J Biol Chem 2006; 282:5790-800. [PMID: 17170115 DOI: 10.1074/jbc.m606284200] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Transcriptional and post-transcriptional regulatory mechanisms are commonly accepted paradigms of tumorigenesis. The view is emerging that deregulation of translation contributes importantly to cancer development, a role not generally appreciated before. Eukaryotic initiation factor eIF3 contains at least thirteen non-identical subunits, named from eIF3a to eIF3m, and plays an essential role in the rate-limiting initiation phase of translation. Increased mRNA and protein levels of the eIF3a, -3b, -3c, -3h, and -3i subunits have been detected in a wide variety of human tumors and are frequently identified as prognostic biomarkers for poor clinical outcome. However, it remains to be established whether up-regulation of eIF3 subunits is a consequence or a cause of the malignant phenotypes. Here we report that ectopic expression of eIF3a, -3b, -3c, -3h, or -3i in stably transfected NIH3T3 cells leads to a number of oncogenic properties: decreased doubling times, increased clonogenicity and viability, facilitated S-phase entry, attenuation of apoptosis, formation of transformed foci, and anchorage-independent growth. Only overexpression of the transforming subunits results in a stimulation of initiation and global protein synthesis rates and enhanced translation of poorly translated mRNAs that encode growth-regulating proteins, including cyclinD1, c-Myc, fibroblast growth factor-2, and ornithine decarboxylase, which may be responsible for oncogenic malignancy in the transformed cell lines. Based on these results, we hypothesize that eIF3 contributes to hyperactivation of the translation initiation machinery and thereby may play an important role in neoplasia. Cancer cells appear to require an aberrantly activated translational state to survive, suggesting that the initiation factors may be promising therapeutic targets for treating cancer.
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Affiliation(s)
- Lili Zhang
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, California 95616, USA
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46
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Sharon M, Taverner T, Ambroggio XI, Deshaies RJ, Robinson CV. Structural organization of the 19S proteasome lid: insights from MS of intact complexes. PLoS Biol 2006; 4:e267. [PMID: 16869714 PMCID: PMC1523230 DOI: 10.1371/journal.pbio.0040267] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Accepted: 06/09/2006] [Indexed: 11/26/2022] Open
Abstract
The 26S proteasome contains a 19S regulatory particle that selects and unfolds ubiquitinated substrates for degradation in the 20S catalytic particle. To date there are no high-resolution structures of the 19S assembly, nor of the lid or base subcomplexes that constitute the 19S. Mass spectra of the intact lid complex from
Saccharomyces cerevisiae show that eight of the nine subunits are present stoichiometrically and that a stable tetrameric subcomplex forms in solution. Application of tandem mass spectrometry to the intact lid complex reveals the subunit architecture, while the coupling of a cross-linking approach identifies further interaction partners. Taking together our results with previous analyses we are able to construct a comprehensive interaction map. In summary, our findings allow us to identify a scaffold for the assembly of the particle and to propose a regulatory mechanism that prevents exposure of the active site until assembly is complete. More generally, the results highlight the potential of mass spectrometry to add crucial insight into the structural organization of an endogenous, wild-type complex.
Tandem mass spectrometry coupled with structural cross-linking enabled a depiction of how components of the 19S proteasome lid interact and the active site remains hidden until assembly is complete.
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Affiliation(s)
- Michal Sharon
- 1Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Thomas Taverner
- 1Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Xavier I Ambroggio
- 2Division of Biology, California Institute of Technology, Pasadena, California, United States of America
| | - Raymond J Deshaies
- 2Division of Biology, California Institute of Technology, Pasadena, California, United States of America
| | - Carol V Robinson
- 1Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
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Abstract
The Ras GTPases act as binary switches for signal transduction pathways that are important for growth regulation and tumorigenesis. Despite the biochemical simplicity of this switch, Ras proteins control multiple pathways, and the functions of the four mammalian Ras proteins are not overlapping. This raises an important question--how does a Ras protein selectively regulate a particular activity? One recently emerging model suggests that a single Ras protein can control different functions by acting in distinct cellular compartments. A critical test of this model is to identify pathways that are selectively controlled by Ras when it is localized to a particular compartment. A recent study has examined Ras signaling in the fission yeast Schizosaccharomyces pombe, which expresses only one Ras protein that controls two separate evolutionarily conserved pathways. This study demonstrates that whereas Ras localized to the plasma membrane selectively regulates a MAP kinase pathway to mediate mating pheromone signaling, Ras localized to the endomembrane activates a Cdc42 pathway to mediate cell polarity and protein trafficking. This study has provided unambiguous evidence for compartmentalized signaling of Ras.
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Affiliation(s)
- Eric C. Chang
- Baylor College of Medicine; Department of Molecular and Cell Biology; The Breast Center; Houston, Texas
- Correspondence to: Eric C. Chang; Baylor College of Medicine; Baylor Plaza, BCM 600; Department of Molecular and Cell Biology; The Breast Center; Houston, Texas, 77030; Tel.: 713-798-3519; Fax: 713-798-1462; /Mark R. Philips; New York University School of Medicine; 550 1st Avenue; Departments of Medicine, Cell Biology and Pharmacology; New York, New York 10016, USA; Tel.: 212.263.7404;
| | - Mark R. Philips
- New York University School of Medicine; Department of Medicine, Cell Biology and Pharmacology; New York, New York
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48
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Abstract
Three structurally related protein complexes, the COP9 signalosome, the proteasome lid, and the eukaryotic translation initiation factor 3, are revealing new insights into developmental processes and into cell cycle control in healthy cells and cells exposed to genotoxic stress. Newly discovered cullin-RING E3 ubiquitin ligases assembled on the CUL4 platform may provide links between DNA replication, chromatin, and proteolysis.
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Affiliation(s)
- Albrecht G von Arnim
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee 37996, USA.
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49
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Onken B, Wiener H, Philips MR, Chang EC. Compartmentalized signaling of Ras in fission yeast. Proc Natl Acad Sci U S A 2006; 103:9045-50. [PMID: 16754851 PMCID: PMC1482563 DOI: 10.1073/pnas.0603318103] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Compartment-specific Ras signaling is an emerging paradigm that may explain the multiplex outputs from a single GTPase. The fission yeast, Schizosaccharomyces pombe, affords a simple system in which to study Ras signaling because it has a single Ras protein, Ras1, that regulates two distinct pathways: one that controls mating through a Byr2-mitogen-activated protein kinase cascade and one that signals through Scd1-Cdc42 to maintain elongated cell morphology. We generated Ras1 mutants that are restricted to either the endomembrane or the plasma membrane. Protein binding studies showed that each could interact with the effectors of both pathways. However, when examined in ras1 null cells, endomembrane-restricted Ras1 supported morphology but not mating, and, conversely, plasma membrane-restricted Ras1 supported mating but did not signal to Scd1-Cdc42. These observations provide a striking demonstration of compartment-specific Ras signaling and indicate that spatial specificity in the Ras pathway is evolutionarily conserved.
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Affiliation(s)
- Brian Onken
- *Department of Molecular and Cell Biology, The Breast Center, Baylor College of Medicine, 1 Baylor Plaza, BCM 600, Houston, TX 77030; and
| | - Heidi Wiener
- Department of Medicine, Cell Biology, and Pharmacology, New York University School of Medicine, 550 1st Avenue, New York, NY 10016
| | - Mark R. Philips
- Department of Medicine, Cell Biology, and Pharmacology, New York University School of Medicine, 550 1st Avenue, New York, NY 10016
- To whom correspondence may be addressed. E-mail:
or
| | - Eric C. Chang
- *Department of Molecular and Cell Biology, The Breast Center, Baylor College of Medicine, 1 Baylor Plaza, BCM 600, Houston, TX 77030; and
- To whom correspondence may be addressed. E-mail:
or
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50
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Abstract
The 2004 Nobel Prize in chemistry for the discovery of protein ubiquitination has led to the recognition of cellular proteolysis as a central area of research in biology. Eukaryotic proteins targeted for degradation by this pathway are first 'tagged' by multimers of a protein known as ubiquitin and are later proteolyzed by a giant enzyme known as the proteasome. This article recounts the key observations that led to the discovery of ubiquitin-proteasome system (UPS). In addition, different aspects of proteasome biology are highlighted. Finally, some key roles of the UPS in different areas of biology and the use of inhibitors of this pathway as possible drug targets are discussed.
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Affiliation(s)
- Dipankar Nandi
- Department of Biochemistry, Indian Institute of Science, Bangalore.
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