1
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Kodiha M, Azad N, Chu S, Crampton N, Stochaj U. Oxidative stress and signaling through EGFR and PKA pathways converge on the nuclear transport factor RanBP1. Eur J Cell Biol 2024; 103:151376. [PMID: 38011756 DOI: 10.1016/j.ejcb.2023.151376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 11/01/2023] [Accepted: 11/17/2023] [Indexed: 11/29/2023] Open
Abstract
Nuclear protein trafficking requires the soluble transport factor RanBP1. The subcellular distribution of RanBP1 is dynamic, as the protein shuttles between the nucleus and cytoplasm. To date, the signaling pathways regulating RanBP1 subcellular localization are poorly understood. During interphase, RanBP1 resides mostly in the cytoplasm. We show here that oxidative stress concentrates RanBP1 in the nucleus, and our study defines the underlying mechanisms. Specifically, RanBP1's cysteine residues are not essential for its oxidant-induced relocation. Furthermore, our pharmacological approaches uncover that signaling mediated by epidermal growth factor receptor (EGFR) and protein kinase A (PKA) control RanBP1 localization during stress. In particular, pharmacological inhibitors of EGFR or PKA diminish the oxidant-dependent relocation of RanBP1. Mutant analysis identified serine 60 and tyrosine 103 as regulators of RanBP1 nuclear accumulation during oxidant exposure. Taken together, our results define RanBP1 as a target of oxidative stress and a downstream effector of EGFR and PKA signaling routes. This positions RanBP1 at the intersection of important cellular signaling circuits.
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Affiliation(s)
- Mohamed Kodiha
- Department of Physiology McGill University, Montreal H3G 1Y6, Canada
| | - Nabila Azad
- Department of Physiology McGill University, Montreal H3G 1Y6, Canada
| | - Siwei Chu
- Department of Physiology McGill University, Montreal H3G 1Y6, Canada
| | - Noah Crampton
- Department of Physiology McGill University, Montreal H3G 1Y6, Canada
| | - Ursula Stochaj
- Department of Physiology McGill University, Montreal H3G 1Y6, Canada.
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2
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Yang Y, Guo L, Chen L, Gong B, Jia D, Sun Q. Nuclear transport proteins: structure, function, and disease relevance. Signal Transduct Target Ther 2023; 8:425. [PMID: 37945593 PMCID: PMC10636164 DOI: 10.1038/s41392-023-01649-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 11/12/2023] Open
Abstract
Proper subcellular localization is crucial for the functioning of biomacromolecules, including proteins and RNAs. Nuclear transport is a fundamental cellular process that regulates the localization of many macromolecules within the nuclear or cytoplasmic compartments. In humans, approximately 60 proteins are involved in nuclear transport, including nucleoporins that form membrane-embedded nuclear pore complexes, karyopherins that transport cargoes through these complexes, and Ran system proteins that ensure directed and rapid transport. Many of these nuclear transport proteins play additional and essential roles in mitosis, biomolecular condensation, and gene transcription. Dysregulation of nuclear transport is linked to major human diseases such as cancer, neurodegenerative diseases, and viral infections. Selinexor (KPT-330), an inhibitor targeting the nuclear export factor XPO1 (also known as CRM1), was approved in 2019 to treat two types of blood cancers, and dozens of clinical trials of are ongoing. This review summarizes approximately three decades of research data in this field but focuses on the structure and function of individual nuclear transport proteins from recent studies, providing a cutting-edge and holistic view on the role of nuclear transport proteins in health and disease. In-depth knowledge of this rapidly evolving field has the potential to bring new insights into fundamental biology, pathogenic mechanisms, and therapeutic approaches.
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Affiliation(s)
- Yang Yang
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Lu Guo
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Lin Chen
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Bo Gong
- The Key Laboratory for Human Disease Gene Study of Sichuan Province and Department of Laboratory Medicine, Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, Chengdu, China
| | - Da Jia
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Department of Pediatrics, West China Second University Hospital, State Key Laboratory of Biotherapy, Sichuan University, Chengdu, China.
| | - Qingxiang Sun
- Department of Pulmonary and Critical Care Medicine, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China.
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer Centre, West China Hospital, Sichuan University, and Collaborative Innovation Centre of Biotherapy, Chengdu, China.
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3
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Audia S, Brescia C, Dattilo V, D’Antona L, Calvano P, Iuliano R, Trapasso F, Perrotti N, Amato R. RANBP1 (RAN Binding Protein 1): The Missing Genetic Piece in Cancer Pathophysiology and Other Complex Diseases. Cancers (Basel) 2023; 15:cancers15020486. [PMID: 36672435 PMCID: PMC9857238 DOI: 10.3390/cancers15020486] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/29/2022] [Accepted: 01/11/2023] [Indexed: 01/15/2023] Open
Abstract
RANBP1 encoded by RANBP1 or HTF9A (Hpall Tiny Fragments Locus 9A), plays regulatory functions of the RAN-network, belonging to the RAS superfamily of small GTPases. Through this function, RANBP1 regulates the RANGAP1 activity and, thus, the fluctuations between GTP-RAN and GDP-RAN. In the light of this, RANBP1 take actions in maintaining the nucleus-cytoplasmic gradient, thus making nuclear import-export functional. RANBP1 has been implicated in the inter-nuclear transport of proteins, nucleic acids and microRNAs, fully contributing to cellular epigenomic signature. Recently, a RANBP1 diriment role in spindle checkpoint formation and nucleation has emerged, thus constituting an essential element in the control of mitotic stability. Over time, RANBP1 has been demonstrated to be variously involved in human cancers both for the role in controlling nuclear transport and RAN activity and for its ability to determine the efficiency of the mitotic process. RANBP1 also appears to be implicated in chemo-hormone and radio-resistance. A key role of this small-GTPases related protein has also been demonstrated in alterations of axonal flow and neuronal plasticity, as well as in viral and bacterial metabolism and in embryological maturation. In conclusion, RANBP1 appears not only to be an interesting factor in several pathological conditions but also a putative target of clinical interest.
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Affiliation(s)
- Salvatore Audia
- Dipartimento di Scienze della Salute, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Carolina Brescia
- Dipartimento di Scienze della Salute, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Vincenzo Dattilo
- Dipartimento di Medicina Sperimentale e Clinica, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Lucia D’Antona
- Dipartimento di Scienze della Salute, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Pierluigi Calvano
- Dipartimento di Scienze della Salute, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Rodolfo Iuliano
- Dipartimento di Scienze della Salute, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Francesco Trapasso
- Dipartimento di Medicina Sperimentale e Clinica, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Nicola Perrotti
- Dipartimento di Scienze della Salute, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Rosario Amato
- Dipartimento di Scienze della Salute, Campus Salvatore Venuta, Università degli Studi “Magna Graecia” di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
- Correspondence: ; Tel.: +39-0961-3694084
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4
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Naoumkina M, Thyssen GN, Fang DD, Florane CB, Li P. A deletion/duplication in the Ligon lintless-2 locus induces siRNAs that inhibit cotton fiber cell elongation. PLANT PHYSIOLOGY 2022; 190:1792-1805. [PMID: 35997586 PMCID: PMC9614481 DOI: 10.1093/plphys/kiac384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 07/22/2022] [Indexed: 06/15/2023]
Abstract
Most cultivated cotton (Gossypium hirsutum L.) varieties have two types of seed fibers: short fuzz fiber strongly adhered to the seed coat, and long lint fiber used in the textile industry. The Ligon lintless-2 (Li2) cotton mutant has a normal vegetative phenotype but produces very short lint fiber on the seeds. The Li2 mutation is controlled by a single dominant gene. We discovered a large structural rearrangement at the end of chromosome D13 in the Li2 mutant based on whole-genome sequencing and genetic mapping of segregating populations. The rearrangement contains a 177-kb deletion and a 221-kb duplication positioned as a tandem inverted repeat. The gene Gh_D13G2437 is located at the junction of the inverted repeat in the duplicated region. During transcription such structure spontaneously forms self-complementary hairpin RNA of Gh_D13G2437 followed by production of small interfering RNA (siRNA). Gh_D13G2437 encodes a Ran-Binding Protein 1 (RanBP1) that preferentially expresses during cotton fiber elongation. The abundance of siRNA produced from Gh_D13G2437 reciprocally corresponds with the abundance of highly homologous (68%-98% amino acid sequence identity) RanBP1 family transcripts during fiber elongation, resulting in a shorter fiber phenotype in the Li2. Overexpression of Gh_D13G2437 in the Li2 mutant recovered the long lint fiber phenotype. Taken together, our findings revealed that siRNA-induced silencing of a family of RanBP1s inhibit elongation of cotton fiber cells in the Li2 mutant.
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Affiliation(s)
- Marina Naoumkina
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
| | - Gregory N Thyssen
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
- Cotton Chemistry and Utilization Research Unit, USDA-ARS-SRRC, New Orleans, Louisiana 70124, USA
| | - David D Fang
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
| | - Christopher B Florane
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
| | - Ping Li
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
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5
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Lagadec F, Carlon-Andres I, Ragues J, Port S, Wodrich H, Kehlenbach RH. CRM1 Promotes Capsid Disassembly and Nuclear Envelope Translocation of Adenovirus Independently of Its Export Function. J Virol 2022; 96:e0127321. [PMID: 34757845 PMCID: PMC8826800 DOI: 10.1128/jvi.01273-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 11/01/2021] [Indexed: 11/20/2022] Open
Abstract
After receptor-mediated endocytosis and endosomal escape, adenoviral capsids can travel via microtubule organizing centers to the nuclear envelope. Upon capsid disassembly, viral genome import into nuclei of interphase cells then occurs through nuclear pore complexes, involving the nucleoporins Nup214 and Nup358. Import also requires the activity of the classic nuclear export receptor CRM1, as it is blocked by the selective inhibitor leptomycin B. We have now used artificially enucleated as well as mitotic cells to analyze the role of an intact nucleus in different steps of the viral life cycle. In enucleated U2OS cells, viral capsids traveled to the microtubule organizing center, whereas their removal from this complex was blocked, suggesting that this step required nuclear factors. In mitotic cells, on the other hand, CRM1 promoted capsid disassembly and genome release, suggesting a role of this protein that does not require intact nuclear envelopes or nuclear pore complexes and is distinct from its function as a nuclear export receptor. Similar to enucleation, inhibition of CRM1 by leptomycin B also leads to an arrest of adenoviral capsids at the microtubule organizing center. In a small-scale screen using leptomycin B-resistant versions of CRM1, we identified a mutant, CRM1 W142A P143A, that is compromised with respect to adenoviral capsid disassembly in both interphase and mitotic cells. Strikingly, this mutant is capable of exporting cargo proteins out of the nucleus of living cells or digitonin-permeabilized cells, pointing to a role of the mutated region that is not directly linked to nuclear export. IMPORTANCE A role of nucleoporins and of soluble transport factors in adenoviral genome import into the nucleus of infected cells in interphase has previously been established. The nuclear export receptor CRM1 promotes genome import, but its precise function is not known. Using enucleated and mitotic cells, we showed that CRM1 does not simply function by exporting a crucial factor out of the nucleus that would then trigger capsid disassembly and genome import. Instead, CRM1 has an export-independent role, a notion that is also supported by a mutant, CRM1 W142A P143A, which is export competent but deficient in viral capsid disassembly, in both interphase and mitotic cells.
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Affiliation(s)
- Floriane Lagadec
- Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Göttingen, Germany
- CNRS UMR 5234, Fundamental Microbiology and Pathogenicity, Université de Bordeaux, Bordeaux, France
| | - Irene Carlon-Andres
- CNRS UMR 5234, Fundamental Microbiology and Pathogenicity, Université de Bordeaux, Bordeaux, France
| | - Jessica Ragues
- CNRS UMR 5234, Fundamental Microbiology and Pathogenicity, Université de Bordeaux, Bordeaux, France
| | - Sarah Port
- Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Göttingen, Germany
| | - Harald Wodrich
- CNRS UMR 5234, Fundamental Microbiology and Pathogenicity, Université de Bordeaux, Bordeaux, France
| | - Ralph H. Kehlenbach
- Department of Molecular Biology, Faculty of Medicine, Göttingen Center of Biosciences (GZMB), Georg-August-University Göttingen, Göttingen, Germany
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6
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Li Y, Zhou J, Min S, Zhang Y, Zhang Y, Zhou Q, Shen X, Jia D, Han J, Sun Q. Distinct RanBP1 nuclear export and cargo dissociation mechanisms between fungi and animals. eLife 2019; 8:e41331. [PMID: 31021318 PMCID: PMC6524963 DOI: 10.7554/elife.41331] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 04/24/2019] [Indexed: 02/05/2023] Open
Abstract
Ran binding protein 1 (RanBP1) is a cytoplasmic-enriched and nuclear-cytoplasmic shuttling protein, playing important roles in nuclear transport. Much of what we know about RanBP1 is learned from fungi. Intrigued by the long-standing paradox of harboring an extra NES in animal RanBP1, we discovered utterly unexpected cargo dissociation and nuclear export mechanisms for animal RanBP1. In contrast to CRM1-RanGTP sequestration mechanism of cargo dissociation in fungi, animal RanBP1 solely sequestered RanGTP from nuclear export complexes. In fungi, RanBP1, CRM1 and RanGTP formed a 1:1:1 nuclear export complex; in contrast, animal RanBP1, CRM1 and RanGTP formed a 1:1:2 nuclear export complex. The key feature for the two mechanistic changes from fungi to animals was the loss of affinity between RanBP1-RanGTP and CRM1, since residues mediating their interaction in fungi were not conserved in animals. The biological significances of these different mechanisms in fungi and animals were also studied.
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Affiliation(s)
- Yuling Li
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre of BiotherapyChengduChina
| | - Jinhan Zhou
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre of BiotherapyChengduChina
| | - Sui Min
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre of BiotherapyChengduChina
| | - Yang Zhang
- Division of Abdominal Cancer, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre for BiotherapyChengduChina
| | - Yuqing Zhang
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre of BiotherapyChengduChina
| | - Qiao Zhou
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre of BiotherapyChengduChina
| | - Xiaofei Shen
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Department of Paediatrics, Division of NeurologyWest China Second University Hospital, Sichuan UniversityChengduChina
| | - Da Jia
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Department of Paediatrics, Division of NeurologyWest China Second University Hospital, Sichuan UniversityChengduChina
| | - Junhong Han
- Division of Abdominal Cancer, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre for BiotherapyChengduChina
| | - Qingxiang Sun
- Department of Pathology, State Key Laboratory of Biotherapy and Cancer CenterWest China Hospital, Sichuan University, Collaborative Innovation Centre of BiotherapyChengduChina
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7
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Mizuno Y, Ohtsu M, Shibata Y, Tanaka A, Camagna M, Ojika M, Mori H, Sato I, Chiba S, Kawakita K, Takemoto D. Nicotiana benthamiana RanBP1-1 Is Involved in the Induction of Disease Resistance via Regulation of Nuclear-Cytoplasmic Transport of Small GTPase Ran. FRONTIERS IN PLANT SCIENCE 2019; 10:222. [PMID: 30906303 PMCID: PMC6418045 DOI: 10.3389/fpls.2019.00222] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 02/08/2019] [Indexed: 06/07/2023]
Abstract
Plant cells enhance the tolerances to abiotic and biotic stresses via recognition of the stress, activation and nuclear import of signaling factors, up-regulation of defense genes, nuclear export of mRNA and translation of defense proteins. Nuclear pore-mediated transports should play critical roles in these processes, however, the regulatory mechanisms of nuclear-cytoplasmic transport during stress responses are largely unknown. In this study, a regulator of nuclear export of RNA and proteins, NbRanBP1-1 (Ran-binding protein1-1), was identified as an essential gene for the resistance of Nicotiana benthamiana to potato blight pathogen Phytophthora infestans. NbRanBP1-1-silenced plants showed delayed accumulation of capsidiol, a sesquiterpenoid phytoalexin, in response to elicitor treatment, and reduced resistance to P. infestans. Abnormal accumulation of mRNA was observed in NbRanBP1-1-silenced plants, indicating that NbRanBP1-1 is involved in the nuclear export of mRNA. In NbRanBP1-1-silenced plants, elicitor-induced expression of defense genes, NbEAS and NbWIPK, was not affected in the early stage of defense induction, but the accumulation of NbWIPK protein was reduced. Nuclear export of the small G-protein NbRan1a was activated during the induction of plant defense, whereas this process was compromised in NbRanBP1-1-silenced plants. Silencing of genes encoding the nuclear pore proteins, Nup75 and Nup160, also caused abnormal nuclear accumulation of mRNA, defects in the nuclear export of NbRan1a, and reduced production of capsidiol, resulting in decreased resistance to P. infestans. These results suggest that nuclear export of NbRan is a key event for defense induction in N. benthamiana, and both RanBP1-1 and nucleoporins play important roles in the process.
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8
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Canela-Pérez I, López-Villaseñor I, Mendoza L, Cevallos AM, Hernández R. Nuclear localization signals in trypanosomal proteins. Mol Biochem Parasitol 2019; 229:15-23. [PMID: 30772422 DOI: 10.1016/j.molbiopara.2019.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/14/2019] [Accepted: 02/09/2019] [Indexed: 01/04/2023]
Abstract
The nuclear import of proteins in eukaryotic cells is a fundamental biological process. While it has been analysed to different extents in model eukaryotic organisms, this event has rarely been studied in the early divergent protozoa of the order Kinetoplastida. The work presented here represents an overview of nuclear import in these important species of human pathogens. Initially, an in silico study of classical nuclear localization signals within the published nuclear proteomes of Trypanosoma brucei and Trypanosoma cruzi was carried out. The basic amino acids that comprise the monopartite and bipartite classical nuclear localization signals (cNLS) in trypanosomal proteins are similar to the consensus sequences observed for the nuclear proteins of yeasts, animals and plants. In addition, a summarized description of published studies that experimentally address the NLS of nuclear proteins in trypanosomatids is presented, and the clear occurrence of non-classical NLS (NLS that lack the consensus motifs of basic amino acids) in the analysed reports indicate a complex scenario for the types of receptors in these species. In general, the information presented here agrees with the hypothetical appearance of mechanisms for the recognition of nuclear proteins in early eukaryotic evolution.
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Affiliation(s)
- Israel Canela-Pérez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP 04360, México
| | - Imelda López-Villaseñor
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP 04360, México
| | - Luis Mendoza
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP 04360, México
| | - Ana María Cevallos
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP 04360, México
| | - Roberto Hernández
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP 04360, México.
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9
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Fung HYJ, Fu SC, Chook YM. Nuclear export receptor CRM1 recognizes diverse conformations in nuclear export signals. eLife 2017; 6:e23961. [PMID: 28282025 PMCID: PMC5358978 DOI: 10.7554/elife.23961] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 03/09/2017] [Indexed: 12/14/2022] Open
Abstract
Nuclear export receptor CRM1 binds highly variable nuclear export signals (NESs) in hundreds of different cargoes. Previously we have shown that CRM1 binds NESs in both polypeptide orientations (Fung et al., 2015). Here, we show crystal structures of CRM1 bound to eight additional NESs which reveal diverse conformations that range from loop-like to all-helix, which occupy different extents of the invariant NES-binding groove. Analysis of all NES structures show 5-6 distinct backbone conformations where the only conserved secondary structural element is one turn of helix that binds the central portion of the CRM1 groove. All NESs also participate in main chain hydrogen bonding with human CRM1 Lys568 side chain, which acts as a specificity filter that prevents binding of non-NES peptides. The large conformational range of NES backbones explains the lack of a fixed pattern for its 3-5 hydrophobic anchor residues, which in turn explains the large array of peptide sequences that can function as NESs.
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MESH Headings
- Active Transport, Cell Nucleus
- Amino Acid Sequence
- Binding Sites
- Cell Nucleus/metabolism
- Cloning, Molecular
- Crystallography, X-Ray
- Gene Expression
- Humans
- Hydrogen Bonding
- Hydrophobic and Hydrophilic Interactions
- Karyopherins/chemistry
- Karyopherins/genetics
- Karyopherins/metabolism
- Models, Molecular
- Nuclear Export Signals
- Protein Binding
- Protein Conformation, alpha-Helical
- Protein Conformation, beta-Strand
- Protein Interaction Domains and Motifs
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Sequence Alignment
- Sequence Homology, Amino Acid
- Thermodynamics
- Exportin 1 Protein
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Affiliation(s)
- Ho Yee Joyce Fung
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Szu-Chin Fu
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Yuh Min Chook
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
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10
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Port SA, Mendes A, Valkova C, Spillner C, Fahrenkrog B, Kaether C, Kehlenbach RH. The Oncogenic Fusion Proteins SET-Nup214 and Sequestosome-1 (SQSTM1)-Nup214 Form Dynamic Nuclear Bodies and Differentially Affect Nuclear Protein and Poly(A)+ RNA Export. J Biol Chem 2016; 291:23068-23083. [PMID: 27613868 PMCID: PMC5087727 DOI: 10.1074/jbc.m116.735340] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 08/31/2016] [Indexed: 01/09/2023] Open
Abstract
Genetic rearrangements are a hallmark of several forms of leukemia and can lead to oncogenic fusion proteins. One example of an affected chromosomal region is the gene coding for Nup214, a nucleoporin that localizes to the cytoplasmic side of the nuclear pore complex (NPC). We investigated two such fusion proteins, SET-Nup214 and SQSTM1 (sequestosome)-Nup214, both containing C-terminal portions of Nup214. SET-Nup214 nuclear bodies containing the nuclear export receptor CRM1 were observed in the leukemia cell lines LOUCY and MEGAL. Overexpression of SET-Nup214 in HeLa cells leads to the formation of similar nuclear bodies that recruit CRM1, export cargo proteins, and certain nucleoporins and concomitantly affect nuclear protein and poly(A)+ RNA export. SQSTM1-Nup214, although mostly cytoplasmic, also forms nuclear bodies and inhibits nuclear protein but not poly(A)+ RNA export. The interaction of the fusion proteins with CRM1 is RanGTP-dependent, as shown in co-immunoprecipitation experiments and binding assays. Further analysis revealed that the Nup214 parts mediate the inhibition of nuclear export, whereas the SET or SQSTM1 part determines the localization of the fusion protein and therefore the extent of the effect. SET-Nup214 nuclear bodies are highly mobile structures, which are in equilibrium with the nucleoplasm in interphase and disassemble during mitosis or upon treatment of cells with the CRM1-inhibitor leptomycin B. Strikingly, we found that nucleoporins can be released from nuclear bodies and reintegrated into existing NPC. Our results point to nuclear bodies as a means of preventing the formation of potentially insoluble and harmful protein aggregates that also may serve as storage compartments for nuclear transport factors.
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Affiliation(s)
- Sarah A Port
- From the Department of Molecular Biology, Faculty of Medicine and the Göttingen Center for Molecular Biosciences (GZMB), Georg August University, Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Adélia Mendes
- the Institute of Molecular Biology and Medicine, Université Libre de Bruxelles, 6041 Charleroi, Belgium, and
| | - Christina Valkova
- the Leibniz Institute on Aging,Fritz Lipmann Institute, Beutenbergstrasse 11, 07745 Jena, Germany
| | - Christiane Spillner
- From the Department of Molecular Biology, Faculty of Medicine and the Göttingen Center for Molecular Biosciences (GZMB), Georg August University, Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Birthe Fahrenkrog
- the Institute of Molecular Biology and Medicine, Université Libre de Bruxelles, 6041 Charleroi, Belgium, and
| | - Christoph Kaether
- the Leibniz Institute on Aging,Fritz Lipmann Institute, Beutenbergstrasse 11, 07745 Jena, Germany
| | - Ralph H Kehlenbach
- From the Department of Molecular Biology, Faculty of Medicine and the Göttingen Center for Molecular Biosciences (GZMB), Georg August University, Göttingen, Humboldtallee 23, 37073 Göttingen, Germany,
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11
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Matsuura Y. Mechanistic Insights from Structural Analyses of Ran-GTPase-Driven Nuclear Export of Proteins and RNAs. J Mol Biol 2015; 428:2025-39. [PMID: 26519791 DOI: 10.1016/j.jmb.2015.09.025] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 09/28/2015] [Indexed: 12/13/2022]
Abstract
Understanding how macromolecules are rapidly exchanged between the nucleus and the cytoplasm through nuclear pore complexes is a fundamental problem in biology. Exportins are Ran-GTPase-dependent nuclear transport factors that belong to the karyopherin-β family and mediate nuclear export of a plethora of proteins and RNAs, except for bulk mRNA nuclear export. Exportins bind cargo macromolecules in a Ran-GTP-dependent manner in the nucleus, forming exportin-cargo-Ran-GTP complexes (nuclear export complexes). Transient weak interactions between exportins and nucleoporins containing characteristic FG (phenylalanine-glycine) repeat motifs facilitate nuclear pore complex passage of nuclear export complexes. In the cytoplasm, nuclear export complexes are disassembled, thereby releasing the cargo. GTP hydrolysis by Ran promoted in the cytoplasm makes the disassembly reaction virtually irreversible and provides thermodynamic driving force for the overall export reaction. In the past decade, X-ray crystallography of some of the exportins in various functional states coupled with functional analyses, single-particle electron microscopy, molecular dynamics simulations, and small-angle solution X-ray scattering has provided rich insights into the mechanism of cargo binding and release and also begins to elucidate how exportins interact with the FG repeat motifs. The knowledge gained from structural analyses of nuclear export is being translated into development of clinically useful inhibitors of nuclear export to treat human diseases such as cancer and influenza.
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Affiliation(s)
- Yoshiyuki Matsuura
- Division of Biological Science and Structural Biology Research Center, Graduate School of Science, Nagoya University, Nagoya 466-8550, Japan.
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12
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Marcus JM, Burke RT, DeSisto JA, Landesman Y, Orth JD. Longitudinal tracking of single live cancer cells to understand cell cycle effects of the nuclear export inhibitor, selinexor. Sci Rep 2015; 5:14391. [PMID: 26399741 PMCID: PMC4585873 DOI: 10.1038/srep14391] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 08/28/2015] [Indexed: 12/22/2022] Open
Abstract
Longitudinal tracking is a powerful approach to understand the biology of single cells. In cancer therapy, outcome is determined at the molecular and cellular scale, yet relationships between cellular response and cell fate are often unknown. The selective inhibitor of nuclear export, selinexor, is in development for the treatment of various cancers. Selinexor covalently binds exportin-1, causing nuclear sequestration of cargo proteins, including key regulators of the cell cycle and apoptosis. The cell cycle effects of selinexor and the relationships between cell cycle effects and cell fates, has not been described for individual cells. Using fluorescent cell cycle indicators we report the majority of cell death after selinexor treatment occurs from a protracted G1-phase and early S-phase. G1- or early S-phase treated cells show the strongest response and either die or arrest, while those treated in late S- or G2-phase progress to mitosis and divide. Importantly, the progeny of cell divisions also die or arrest, mostly in the next G1-phase. Cells that survive selinexor are negative for multiple proliferation biomarkers, indicating a penetrant, arrested state. Selinexor acts quickly, shows strong cell cycle selectivity, and is highly effective at arresting cell growth and inducing death in cancer-derived cells.
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Affiliation(s)
- Joshua M Marcus
- Department of Molecular, Cellular, and Developmental Biology, GOLD A240B, 347 UCB, University of Colorado-Boulder, Boulder, CO 80309 USA
| | - Russell T Burke
- Department of Molecular, Cellular, and Developmental Biology, GOLD A240B, 347 UCB, University of Colorado-Boulder, Boulder, CO 80309 USA
| | - John A DeSisto
- Department of Molecular, Cellular, and Developmental Biology, GOLD A240B, 347 UCB, University of Colorado-Boulder, Boulder, CO 80309 USA
| | - Yosef Landesman
- Karyopharm Therapeutics, Inc., 85 Wells Ave., Newton, MA 02459
| | - James D Orth
- Department of Molecular, Cellular, and Developmental Biology, GOLD A240B, 347 UCB, University of Colorado-Boulder, Boulder, CO 80309 USA
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13
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Cautain B, Hill R, de Pedro N, Link W. Components and regulation of nuclear transport processes. FEBS J 2014; 282:445-62. [PMID: 25429850 PMCID: PMC7163960 DOI: 10.1111/febs.13163] [Citation(s) in RCA: 177] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 11/11/2014] [Accepted: 11/12/2014] [Indexed: 12/27/2022]
Abstract
The spatial separation of DNA replication and gene transcription in the nucleus and protein translation in the cytoplasm is a uniform principle of eukaryotic cells. This compartmentalization imposes a requirement for a transport network of macromolecules to shuttle these components in and out of the nucleus. This nucleo‐cytoplasmic transport of macromolecules is critical for both cell physiology and pathology. Consequently, investigating its regulation and disease‐associated alterations can reveal novel therapeutic approaches to fight human diseases, such as cancer or viral infection. The characterization of the nuclear pore complex, the identification of transport signals and transport receptors, as well as the characterization of the Ran system (providing the energy source for efficient cargo transport) has greatly facilitated our understanding of the components, mechanisms and regulation of the nucleo‐cytoplasmic transport of proteins in our cells. Here we review this knowledge with a specific emphasis on the selection of disease‐relevant molecular targets for potential therapeutic intervention.
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Affiliation(s)
- Bastien Cautain
- Fundacion MEDINA Parque tecnológico ciencias de la salud, Granada, Spain
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14
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Paronett EM, Meechan DW, Karpinski BA, LaMantia AS, Maynard TM. Ranbp1, Deleted in DiGeorge/22q11.2 Deletion Syndrome, is a Microcephaly Gene That Selectively Disrupts Layer 2/3 Cortical Projection Neuron Generation. Cereb Cortex 2014; 25:3977-93. [PMID: 25452572 DOI: 10.1093/cercor/bhu285] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Ranbp1, a Ran GTPase-binding protein implicated in nuclear/cytoplasmic trafficking, is included within the DiGeorge/22q11.2 Deletion Syndrome (22q11.2 DS) critical region associated with behavioral impairments including autism and schizophrenia. Ranbp1 is highly expressed in the developing forebrain ventricular/subventricular zone but has no known obligate function during brain development. We assessed the role of Ranbp1 in a targeted mouse mutant. Ranbp1(-/-) mice are not recovered live at birth, and over 60% of Ranbp1(-/-) embryos are exencephalic. Non-exencephalic Ranbp1(-/-) embryos are microcephalic, and proliferation of cortical progenitors is altered. At E10.5, radial progenitors divide more slowly in the Ranpb1(-/-) dorsal pallium. At E14.5, basal, but not apical/radial glial progenitors, are compromised in the cortex. In both E10.5 apical and E14.5 basal progenitors, M phase of the cell cycle appears selectively retarded by loss of Ranpb1 function. Ranbp1(-/-)-dependent proliferative deficits substantially diminish the frequency of layer 2/3, but not layer 5/6 cortical projection neurons. Ranbp1(-/-) cortical phenotypes parallel less severe alterations in LgDel mice that carry a deletion parallel to many (but not all) 22q11.2 DS patients. Thus, Ranbp1 emerges as a microcephaly gene within the 22q11.2 deleted region that may contribute to altered cortical precursor proliferation and neurogenesis associated with broader 22q11.2 deletion.
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Affiliation(s)
| | - Daniel W Meechan
- GW Institute for Neuroscience Department of Pharmacology and Physiology
| | - Beverly A Karpinski
- GW Institute for Neuroscience Department of Anatomy and Regenerative Biology, The George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
| | | | - Thomas M Maynard
- GW Institute for Neuroscience Department of Pharmacology and Physiology
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15
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Zhang MS, Arnaoutov A, Dasso M. RanBP1 governs spindle assembly by defining mitotic Ran-GTP production. Dev Cell 2014; 31:393-404. [PMID: 25458009 DOI: 10.1016/j.devcel.2014.10.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 09/10/2014] [Accepted: 10/22/2014] [Indexed: 01/06/2023]
Abstract
Accurate control of the Ras-related nuclear protein (Ran) GTPase cycle depends on the regulated activity of regulator of chromosome condensation 1 (RCC1), Ran's nucleotide exchange factor. RanBP1 has been characterized as a coactivator of the Ran GTPase-activating protein RanGAP1. RanBP1 can also form a stable complex with Ran and RCC1, although the dynamics and function of this complex remain poorly understood. Here, we show that formation of the heterotrimeric RCC1/Ran/RanBP1 complex in M phase Xenopus egg extracts controls both RCC1's enzymatic activity and partitioning between the chromatin-bound and soluble pools of RCC1. This mechanism is critical for spatial control of Ran-guanosine triphosphate (GTP) gradients that guide mitotic spindle assembly. Moreover, phosphorylation of RanBP1 drives changes in the dynamics of chromatin-bound RCC1 pools at the metaphase-anaphase transition. Our findings reveal an important mitotic role for RanBP1, controlling the spatial distribution and magnitude of mitotic Ran-GTP production and thereby ensuring accurate execution of Ran-dependent mitotic events.
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Affiliation(s)
- Michael Shaofei Zhang
- Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alexei Arnaoutov
- Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Mary Dasso
- Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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16
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Nucleocytoplasmic transport under stress conditions and its role in HSP70 chaperone systems. Biochim Biophys Acta Gen Subj 2014; 1840:2953-60. [DOI: 10.1016/j.bbagen.2014.04.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 04/11/2014] [Accepted: 04/28/2014] [Indexed: 11/20/2022]
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17
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Fung HYJ, Chook YM. Atomic basis of CRM1-cargo recognition, release and inhibition. Semin Cancer Biol 2014; 27:52-61. [PMID: 24631835 PMCID: PMC4108548 DOI: 10.1016/j.semcancer.2014.03.002] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 03/01/2014] [Indexed: 11/19/2022]
Abstract
CRM1 or XPO1 is the major nuclear export receptor in the cell, which controls the nuclear-cytoplasmic localization of many proteins and RNAs. CRM1 is also a promising cancer drug target as the transport receptor is overexpressed in many cancers where some of its cargos are misregulated and mislocalized to the cytoplasm. Atomic level understanding of CRM1 function has greatly facilitated recent drug discovery and development of CRM1 inhibitors to target a variety of malignancies. Numerous atomic resolution CRM1 structures are now available, explaining how the exporter recognizes nuclear export signals in its cargos, how RanGTP and cargo bind with positive cooperativity, how RanBP1 causes release of export cargos in the cytoplasm and how diverse inhibitors such as Leptomycin B and the new KPT-SINE compounds block nuclear export. This review summarizes structure-function studies that explain CRM1-cargo recognition, release and inhibition.
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Affiliation(s)
- Ho Yee Joyce Fung
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390-9041, USA.
| | - Yuh Min Chook
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390-9041, USA.
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18
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Abstract
The ubiquitin/proteasome system has been characterized extensively, although the site of nuclear substrate turnover has not been established definitively. We report here that two well-characterized nuclear proteins are stabilized in nuclear export mutants in Saccharomyces cerevisiae. The requirement for nuclear export defines a new regulatory step in intracellular proteolysis.
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19
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Kimura M, Thakar K, Karaca S, Imamoto N, Kehlenbach RH. Novel approaches for the identification of nuclear transport receptor substrates. Methods Cell Biol 2014; 122:353-78. [PMID: 24857738 DOI: 10.1016/b978-0-12-417160-2.00016-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
Abstract
Nucleocytoplasmic transport affects the subcellular localization of a large proportion of cellular proteins. Transported proteins interact with a set of ~20 transport receptors, importins and exportins, which mediate translocation through the nuclear pore complex. Here we describe two novel methods based on quantitative proteome analysis for the identification of cargo proteins that are transported by a specific importin or exportin. The first approach is based on SILAC (stable isotope labeling of amino acids in cells) using cells that have been treated or not with specific reagents, followed by subcellular fractionation. Applying this approach to cells treated with or without the selective CRM1 inhibitor leptomycin B, we identified substrates of CRM1, the major nuclear export receptor. In the second SILAC approach, digitonin-permeabilized cells are incubated with nuclear and cytosolic extracts in the absence or presence of particular import receptors of interest. Proteomic analysis of the permeabilized cells then yields proteins whose nuclear import depends specifically on the added import receptor. Using this system, we identified substrates of two representative import receptors, transportin and importin-α/β.
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Affiliation(s)
- Makoto Kimura
- Cellular Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
| | - Ketan Thakar
- Department of Molecular Biology, Faculty of Medicine, Georg-August-University of Göttingen, Göttingen, Germany
| | - Samir Karaca
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Naoko Imamoto
- Cellular Dynamics Laboratory, RIKEN, Wako, Saitama, Japan
| | - Ralph H Kehlenbach
- Department of Molecular Biology, Faculty of Medicine, Georg-August-University of Göttingen, Göttingen, Germany
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20
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Patil H, Cho KI, Lee J, Yang Y, Orry A, Ferreira PA. Kinesin-1 and mitochondrial motility control by discrimination of structurally equivalent but distinct subdomains in Ran-GTP-binding domains of Ran-binding protein 2. Open Biol 2013; 3:120183. [PMID: 23536549 PMCID: PMC3718338 DOI: 10.1098/rsob.120183] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The pleckstrin homology (PH) domain is a versatile fold that mediates a variety of protein–protein and protein–phosphatidylinositol lipid interactions. The Ran-binding protein 2 (RanBP2) contains four interspersed Ran GTPase-binding domains (RBDn= 1–4) with close structural homology to the PH domain of Bruton's tyrosine kinase. The RBD2, kinesin-binding domain (KBD) and RBD3 comprise a tripartite domain (R2KR3) of RanBP2 that causes the unfolding, microtubule binding and biphasic activation of kinesin-1, a crucial anterograde motor of mitochondrial motility. However, the interplay between Ran GTPase and R2KR3 of RanBP2 in kinesin-1 activation and mitochondrial motility is elusive. We use structure–function, biochemical, kinetic and cell-based assays with time-lapse live-cell microscopy of over 260 000 mitochondrial-motility-related events to find mutually exclusive subdomains in RBD2 and RBD3 towards Ran GTPase binding, kinesin-1 activation and mitochondrial motility regulation. The RBD2 and RBD3 exhibit Ran-GTP-independent, subdomain and stereochemical-dependent discrimination on the biphasic kinetics of kinesin-1 activation or regulation of mitochondrial motility. Further, KBD alone and R2KR3 stimulate and suppress, respectively, multiple biophysical parameters of mitochondrial motility. The regulation of the bidirectional transport of mitochondria by either KBD or R2KR3 is highly coordinated, because their kinetic effects are accompanied always by changes in mitochondrial motile events of either transport polarity. These studies uncover novel roles in Ran GTPase-independent subdomains of RBD2 and RBD3, and KBD of RanBP2, that confer antagonizing and multi-modal mechanisms of kinesin-1 activation and regulation of mitochondrial motility. These findings open new venues towards the pharmacological harnessing of cooperative and competitive mechanisms regulating kinesins, RanBP2 or mitochondrial motility in disparate human disorders.
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Affiliation(s)
- Hemangi Patil
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
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21
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Thakar K, Karaca S, Port SA, Urlaub H, Kehlenbach RH. Identification of CRM1-dependent Nuclear Export Cargos Using Quantitative Mass Spectrometry. Mol Cell Proteomics 2013; 12:664-78. [PMID: 23242554 PMCID: PMC3591659 DOI: 10.1074/mcp.m112.024877] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Revised: 11/23/2012] [Indexed: 11/06/2022] Open
Abstract
Chromosome region maintenance 1/exportin1/Exp1/Xpo1 (CRM1) is the major transport receptor for the export of proteins from the nucleus. It binds to nuclear export signals (NESs) that are rich in leucines and other hydrophobic amino acids. The prediction of NESs is difficult because of the extreme recognition flexibility of CRM1. Furthermore, proteins can be exported upon binding to an NES-containing adaptor protein. Here we present an approach for identifying targets of the CRM1-export pathway via quantitative mass spectrometry using stable isotope labeling with amino acids in cell culture. With this approach, we identified >100 proteins from HeLa cells that were depleted from cytosolic fractions and/or enriched in nuclear fractions in the presence of the selective CRM1-inhibitor leptomycin B. Novel and validated substrates are the polyubiquitin-binding protein sequestosome 1, the cancerous inhibitor of protein phosphatase 2A (PP2A), the guanine nucleotide-binding protein-like 3-like protein, the programmed cell death protein 2-like protein, and the cytosolic carboxypeptidase 1 (CCP1). We identified a functional NES in CCP1 that mediates direct binding to the export receptor CRM1. The method will be applicable to other nucleocytoplasmic transport pathways, as well as to the analysis of nucleocytoplasmic shuttling proteins under different growth conditions.
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Affiliation(s)
- Ketan Thakar
- From the ‡Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Samir Karaca
- ¶Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Sarah A. Port
- From the ‡Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Henning Urlaub
- ¶Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
- ‖Bioanalytics, Department of Clinical Chemistry, University Medical Center, Robert-Koch-Str. 40, 37075 Göttingen, Germany
| | - Ralph H. Kehlenbach
- From the ‡Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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22
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Liang H, Xu J, Zhao D, Tian H, Yang X, Liang A, Wang W. Subcellular localization and role of Ran1 in Tetrahymena thermophila amitotic macronucleus. FEBS J 2012; 279:2520-33. [PMID: 22594798 DOI: 10.1111/j.1742-4658.2012.08634.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Amitosis, a direct method of cell division is common in ciliated protozoan, fungi and some animal and plant cells. During amitosis, intranuclear microtubules are reorganized into specified arrays which assist in separation of nucleus, despite lack of a bipolar spindle. However, the regulation of amitosis is not understood. Here, we focused on the localization and role of mitotic spindle assembly regulator: Ran GTPase (Ran1) in macronuclear amitosis in binucleated protozoan Tetrahymena thermophila. HA-tagged Ran1 was localized in the macronucleus throughout the cell cycle of Tetrahymena during vegetative growth, and the accessory factor binding domains of Ran1 contributed to its macronuclear localization. Incomplete somatic knockout of RAN1 resulted in aberrant intramacronuclear microtubule array formation, missegregation of macronuclear chromosomes and ultimately blocked macronuclei proliferation. When the Ran1 cycle was perturbed by overexpression of Ran1T25N (GDP-bound Ran1-mimetic) or Ran1Q70L (GTP-bound Ran1-mimetic), intramacronuclear microtubule assembly was inhibited or multi-micronucleate cells formed. These results suggest that Ran GTPase pathway is involved in assembly of a specialized intramacronuclear microtubule network and coordinates amitotic progression in Tetrahymena.
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Affiliation(s)
- Haixia Liang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan, China
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23
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Ran-dependent nuclear export mediators: a structural perspective. EMBO J 2011; 30:3457-74. [PMID: 21878989 DOI: 10.1038/emboj.2011.287] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 07/22/2011] [Indexed: 12/25/2022] Open
Abstract
Nuclear export is an essential eukaryotic activity. It proceeds through nuclear pore complexes (NPCs) and is mediated by soluble receptors that shuttle between nucleus and cytoplasm. RanGTPase-dependent export mediators (exportins) constitute the largest class of these carriers and are functionally highly versatile. All of these exportins load their substrates in response to RanGTP binding in the nucleus and traverse NPCs as ternary RanGTP-exportin-cargo complexes to the cytoplasm, where GTP hydrolysis leads to export complex disassembly. The different exportins vary greatly in their substrate range. Recent structural studies of both protein- and RNA-specific exporters have illuminated how exportins bind their cargoes, how Ran triggers cargo loading and how export complexes are disassembled in the cytoplasm. Here, we review the current state of knowledge and highlight emerging principles as well as prevailing questions.
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24
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Langer K, Dian C, Rybin V, Müller CW, Petosa C. Insights into the function of the CRM1 cofactor RanBP3 from the structure of its Ran-binding domain. PLoS One 2011; 6:e17011. [PMID: 21364925 PMCID: PMC3045386 DOI: 10.1371/journal.pone.0017011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Accepted: 01/18/2011] [Indexed: 02/03/2023] Open
Abstract
Proteins bearing a leucine-rich nuclear export signal (NES) are exported from the nucleus by the transport factor CRM1, which forms a cooperative ternary complex with the NES-bearing cargo and with the small GTPase Ran. CRM1-mediated export is regulated by RanBP3, a Ran-interacting nuclear protein. Unlike the related proteins RanBP1 and RanBP2, which promote disassembly of the export complex in the cytosol, RanBP3 acts as a CRM1 cofactor, enhancing NES export by stabilizing the export complex in the nucleus. RanBP3 also alters the cargo selectivity of CRM1, promoting recognition of the NES of HIV-1 Rev and of other cargos while deterring recognition of the import adaptor protein Snurportin1. Here we report the crystal structure of the Ran-binding domain (RBD) from RanBP3 and compare it to RBD structures from RanBP1 and RanBP2 in complex with Ran and CRM1. Differences among these structures suggest why RanBP3 binds Ran with unusually low affinity, how RanBP3 modulates the cargo selectivity of CRM1, and why RanBP3 promotes assembly rather than disassembly of the export complex. The comparison of RBD structures thus provides an insight into the functional diversity of Ran-binding proteins.
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Affiliation(s)
- Karla Langer
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Cyril Dian
- Institut de Biologie Structurale Jean-Pierre Ebel, Unité Mixte de Recherche 5075 (Commissariat à L'Energie Atomique et aux Energies Alternatives/Centre National de la Recherche Scientifique/Université Joseph Fourier), Grenoble, France
| | - Vladimir Rybin
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Christoph W. Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Carlo Petosa
- Institut de Biologie Structurale Jean-Pierre Ebel, Unité Mixte de Recherche 5075 (Commissariat à L'Energie Atomique et aux Energies Alternatives/Centre National de la Recherche Scientifique/Université Joseph Fourier), Grenoble, France
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25
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Merkle T. Nucleo-cytoplasmic transport of proteins and RNA in plants. PLANT CELL REPORTS 2011; 30:153-76. [PMID: 20960203 PMCID: PMC3020307 DOI: 10.1007/s00299-010-0928-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 09/30/2010] [Indexed: 05/19/2023]
Abstract
Transport of macromolecules between the nucleus and the cytoplasm is an essential necessity in eukaryotic cells, since the nuclear envelope separates transcription from translation. In the past few years, an increasing number of components of the plant nuclear transport machinery have been characterised. This progress, although far from being completed, confirmed that the general characteristics of nuclear transport are conserved between plants and other organisms. However, plant-specific components were also identified. Interestingly, several mutants in genes encoding components of the plant nuclear transport machinery were investigated, revealing differential sensitivity of plant-specific pathways to impaired nuclear transport. These findings attracted attention towards plant-specific cargoes that are transported over the nuclear envelope, unravelling connections between nuclear transport and components of signalling and developmental pathways. The current state of research in plants is summarised in comparison to yeast and vertebrate systems, and special emphasis is given to plant nuclear transport mutants.
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Affiliation(s)
- Thomas Merkle
- Faculty of Biology, Institute for Genome Research and Systems Biology, University of Bielefeld, 33594 Bielefeld, Germany.
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26
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Güttler T, Madl T, Neumann P, Deichsel D, Corsini L, Monecke T, Ficner R, Sattler M, Görlich D. NES consensus redefined by structures of PKI-type and Rev-type nuclear export signals bound to CRM1. Nat Struct Mol Biol 2010; 17:1367-76. [PMID: 20972448 DOI: 10.1038/nsmb.1931] [Citation(s) in RCA: 193] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2010] [Accepted: 09/07/2010] [Indexed: 12/24/2022]
Abstract
Classic nuclear export signals (NESs) confer CRM1-dependent nuclear export. Here we present crystal structures of the RanGTP-CRM1 complex alone and bound to the prototypic PKI or HIV-1 Rev NESs. These NESs differ markedly in the spacing of their key hydrophobic (Φ) residues, yet CRM1 recognizes them with the same rigid set of five Φ pockets. The different Φ spacings are compensated for by different conformations of the bound NESs: in the case of PKI, an α-helical conformation, and in the case of Rev, an extended conformation with a critical proline docking into a Φ pocket. NMR analyses of CRM1-bound and CRM1-free PKI NES suggest that CRM1 selects NES conformers that pre-exist in solution. Our data lead to a new structure-based NES consensus, and explain why NESs differ in their affinities for CRM1 and why supraphysiological NESs bind the exportin so tightly.
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Affiliation(s)
- Thomas Güttler
- Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Germany
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Hilliard M, Frohnert C, Spillner C, Marcone S, Nath A, Lampe T, Fitzgerald DJ, Kehlenbach RH. The anti-inflammatory prostaglandin 15-deoxy-delta(12,14)-PGJ2 inhibits CRM1-dependent nuclear protein export. J Biol Chem 2010; 285:22202-10. [PMID: 20457605 PMCID: PMC2903415 DOI: 10.1074/jbc.m110.131821] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/06/2010] [Indexed: 12/30/2022] Open
Abstract
The signaling molecule 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) has been described as the "anti-inflammatory prostaglandin." Here we show that substrates of the nuclear export receptor CRM1 accumulate in the nucleus in the presence of 15d-PGJ(2), identifying this prostaglandin as a regulator of CRM1-dependent nuclear protein export that can be produced endogenously. Like leptomycin B (LMB), an established fungal CRM1-inhibitor, 15d-PGJ(2) reacts with a conserved cysteine residue in the CRM1 sequence. This covalent modification prevents the formation of nuclear export complexes. Cells that are transfected with mutant CRM1 (C528S) are resistant to the inhibitory effects of LMB and 15d-PGJ(2), demonstrating that the same single amino acid is targeted by the two compounds. Inhibition of the CRM1 pathway by endogenously produced prostaglandin and/or exogenously applied 15d-PGJ(2) may contribute to its anti-inflammatory, anti-proliferative, and anti-viral effects.
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Affiliation(s)
- Mark Hilliard
- From the UCD Conway Institute, Belfield, Dublin 4, Ireland and
| | - Cornelia Frohnert
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Christiane Spillner
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Simone Marcone
- From the UCD Conway Institute, Belfield, Dublin 4, Ireland and
| | - Annegret Nath
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Tina Lampe
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | | | - Ralph H. Kehlenbach
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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28
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Koyama M, Matsuura Y. An allosteric mechanism to displace nuclear export cargo from CRM1 and RanGTP by RanBP1. EMBO J 2010; 29:2002-13. [PMID: 20485264 PMCID: PMC2892370 DOI: 10.1038/emboj.2010.89] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 04/16/2010] [Indexed: 11/09/2022] Open
Abstract
The karyopherin CRM1 mediates nuclear export of proteins and ribonucleoproteins bearing a leucine-rich nuclear export signal (NES). To elucidate the precise mechanism by which NES-cargos are dissociated from CRM1 in the cytoplasm, which is important for transport directionality, we determined a 2.0-A resolution crystal structure of yeast CRM1:RanBP1:RanGTP complex, an intermediate in the disassembly of the CRM1 nuclear export complex. The structure shows that on association of Ran-binding domain (RanBD) of RanBP1 with CRM1:NES-cargo:RanGTP complex, RanBD and the C-terminal acidic tail of Ran induce a large movement of the intra-HEAT9 loop of CRM1. The loop moves to the CRM1 inner surface immediately behind the NES-binding site and causes conformational rearrangements in HEAT repeats 11 and 12 so that the hydrophobic NES-binding cleft on the CRM1 outer surface closes, squeezing out the NES-cargo. This allosteric mechanism accelerates dissociation of NES by over two orders of magnitude. Structure-based mutagenesis indicated that the HEAT9 loop also functions as an allosteric autoinhibitor to stabilize CRM1 in a conformation that is unable to bind NES-cargo in the absence of RanGTP.
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Affiliation(s)
- Masako Koyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
| | - Yoshiyuki Matsuura
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
- Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
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29
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Oka M, Asally M, Yasuda Y, Ogawa Y, Tachibana T, Yoneda Y. The mobile FG nucleoporin Nup98 is a cofactor for Crm1-dependent protein export. Mol Biol Cell 2010; 21:1885-96. [PMID: 20375145 PMCID: PMC2877646 DOI: 10.1091/mbc.e09-12-1041] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 03/26/2010] [Accepted: 03/29/2010] [Indexed: 12/18/2022] Open
Abstract
Nup98 is a mobile nucleoporin that forms distinct dots in the nucleus, and, although a role for Nup98 in nuclear transport has been suggested, its precise function remains unclear. Here, we show that Nup98 plays an important role in Crm1-mediated nuclear protein export. Nuclear, but not cytoplasmic, dots of EGFP-tagged Nup98 disappeared rapidly after cell treatment with leptomycin B, a specific inhibitor of the nuclear export receptor, Crm1. Mutational analysis demonstrated that Nup98 physically and functionally interacts with Crm1 in a RanGTP-dependent manner through its N-terminal phenylalanine-glycine (FG) repeat region. Moreover, the activity of the Nup98-Crm1 complex was modulated by RanBP3, a known cofactor for Crm1-mediated nuclear export. Finally, cytoplasmic microinjection of anti-Nup98 inhibited the Crm1-dependent nuclear export of proteins, concomitant with the accumulation of anti-Nup98 in the nucleus. These results clearly demonstrate that Nup98 functions as a novel shuttling cofactor for Crm1-mediated nuclear export in conjunction with RanBP3.
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Affiliation(s)
- Masahiro Oka
- *Biomolecular Dynamics Group, Graduate School of Frontier Biosciences
- Department of Biochemistry, Graduate School of Medicine, Osaka University, and
- Japan Science and Technology Corporation (JST), Core Research for Evolution Science and Technology (CREST), Osaka University, Suita, Osaka 565-0871, Japan; and
| | - Munehiro Asally
- *Biomolecular Dynamics Group, Graduate School of Frontier Biosciences
| | - Yoshinari Yasuda
- *Biomolecular Dynamics Group, Graduate School of Frontier Biosciences
| | - Yutaka Ogawa
- *Biomolecular Dynamics Group, Graduate School of Frontier Biosciences
| | - Taro Tachibana
- Department of Bioengineering, Graduate School of Engineering, Osaka City University, Osaka 558-8585, Japan
| | - Yoshihiro Yoneda
- *Biomolecular Dynamics Group, Graduate School of Frontier Biosciences
- Department of Biochemistry, Graduate School of Medicine, Osaka University, and
- Japan Science and Technology Corporation (JST), Core Research for Evolution Science and Technology (CREST), Osaka University, Suita, Osaka 565-0871, Japan; and
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30
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Van Neck T, Pannecouque C, Vanstreels E, Stevens M, Dehaen W, Daelemans D. Inhibition of the CRM1-mediated nucleocytoplasmic transport by N-azolylacrylates: structure-activity relationship and mechanism of action. Bioorg Med Chem 2008; 16:9487-97. [PMID: 18835718 DOI: 10.1016/j.bmc.2008.09.051] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Revised: 09/12/2008] [Accepted: 09/16/2008] [Indexed: 12/01/2022]
Abstract
CRM1-mediated nucleocytoplasmic transport plays an important role in many cellular processes and diseases. To investigate the structural basis required for the inhibition of the CRM1-mediated nuclear export we have synthesized analogs of a previously identified small molecule lead compound and monitored their activity against the Rev function of the human immunodeficiency virus. Microscopy studies show that the active congeners of this series inhibit the nucleocytoplasmic transport of Rev and the co-localization between Rev and CRM1 in living cells. Mechanism of action studies show their interaction with the Cys528 residue of CRM1 involving a Michael-addition type of reaction. However, structure-activity relationship demonstrates strict constraints to the structure of the inhibitors, and shows that activity is not solely correlated to Michael-addition suggesting a more complex mechanism of action. Our results are suggestive for the existence of a well-defined interaction at the CRM1-NES binding site. In addition, the most selective congener inhibited the HIV-1 production in latently infected cells. These specific CRM1 inhibitors are of interest as tool for analyzing the mechanisms of post-transcriptional control of gene expression and provide insight in the design of new agents.
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Affiliation(s)
- Tine Van Neck
- Laboratory of Organic Synthesis, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
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31
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Khacho M, Mekhail K, Pilon-Larose K, Pause A, Côté J, Lee S. eEF1A is a novel component of the mammalian nuclear protein export machinery. Mol Biol Cell 2008; 19:5296-308. [PMID: 18799616 DOI: 10.1091/mbc.e08-06-0562] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The cytoplasmic translation factor eEF1A has been implicated in the nuclear export of tRNA species in lower eukaryotes. Here we demonstrate that eEF1A plays a central role in nuclear export of proteins in mammalian cells. TD-NEM (transcription-dependent nuclear export motif), a newly characterized nuclear export signal, mediates efficient nuclear export of several proteins including the von Hippel-Lindau (VHL) tumor suppressor and the poly(A)-binding protein (PABP1) in a manner that is dependent on ongoing RNA polymerase II (RNA PolII)-dependent transcription. eEF1A interacts specifically with TD-NEM of VHL and PABP1 and disrupting this interaction, by point mutations of key TD-NEM residues or treatment with actinomycin D, an inhibitor of RNA PolII-dependent transcription, prevents assembly and nuclear export. siRNA-induced knockdown or antibody-mediated depletion of eEF1A prevents in vivo and in vitro nuclear export of TD-NEM-containing proteins. Nuclear retention experiments and inhibition of the Exportin-5 pathway suggest that eEF1A stimulates nuclear export of proteins from the cytoplasmic side of the nuclear envelope, without entering the nucleus. Together, these data identify a role for eEF1A, a cytoplasmic mediator of tRNA export in yeast, in the nuclear export of proteins in mammalian cells. These results also provide a link between the translational apparatus and subcellular trafficking machinery demonstrating that these two central pathways in basic metabolism can act cooperatively.
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Affiliation(s)
- Mireille Khacho
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada
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32
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Abstract
The small nuclear GTPase Ran controls the directionality of macromolecular transport between the nucleus and the cytoplasm. Ran also has important roles during mitosis, when the nucleus is dramatically reorganized to allow chromosome segregation. Ran directs the assembly of the mitotic spindle, nuclear-envelope dynamics and the timing of cell-cycle transitions. The mechanisms that underlie these functions provide insights into the spatial and temporal coordination of the changes that occur in intracellular organization during the cell-division cycle.
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Affiliation(s)
- Paul R Clarke
- Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, Scotland, UK.
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33
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Kremer BE, Adang LA, Macara IG. Septins regulate actin organization and cell-cycle arrest through nuclear accumulation of NCK mediated by SOCS7. Cell 2007; 130:837-50. [PMID: 17803907 PMCID: PMC2085444 DOI: 10.1016/j.cell.2007.06.053] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 04/16/2007] [Accepted: 06/25/2007] [Indexed: 11/26/2022]
Abstract
Mammalian septins are GTP-binding proteins the functions of which are not well understood. Knockdown of SEPT2, 6, and 7 causes stress fibers to disintegrate and cells to lose polarity. We now show that this phenotype is induced by nuclear accumulation of the adaptor protein NCK, as the effects can be reversed or induced by cytoplasmic or nuclear NCK, respectively. NCK is carried into the nucleus by SOCS7 (suppressor of cytokine signaling 7), which possesses nuclear import/export signals. SOCS7 interacts with septins and NCK through distinct domains. DNA damage induces actin and septin rearrangement and rapid nuclear accumulation of NCK and SOCS7. Moreover, NCK expression is essential for cell-cycle arrest. The septin-SOCS7-NCK axis intersects with the canonical DNA damage cascade downstream of ATM/ATR and is essential for p53 Ser15 phosphorylation. These data illuminate an unanticipated connection between septins, SOCS7, NCK signaling, and the DNA damage response.
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Affiliation(s)
- Brandon E Kremer
- Department of Microbiology, University of Virginia School of Medicine, Charlottesville, VA 22908-0577, USA
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34
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Fujita A, Sato C, Kitajima K. Identification of the nuclear export signals that regulate the intracellular localization of the mouse CMP-sialic acid synthetase. Biochem Biophys Res Commun 2007; 355:174-80. [PMID: 17292865 DOI: 10.1016/j.bbrc.2007.01.139] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 01/23/2007] [Indexed: 11/19/2022]
Abstract
The CMP-sialic acid synthetase (CSS) catalyzes the activation of sialic acid (Sia) to CMP-Sia which is a donor substrate of sialyltransferases. The vertebrate CSSs are usually localized in nucleus due to the nuclear localization signal (NLS) on the molecule. In this study, we first point out that a small, but significant population of the mouse CMP-sialic acid synthetase (mCSS) is also present in cytoplasm, though mostly in nucleus. As a mechanism for the localization in cytoplasm, we first identified two nuclear export signals (NESs) in mCSS, based on the localization studies of the potential NES-deleted mCSS mutants as well as the potential NES-tagged eGFP proteins. These two NESs are conserved among mammalian and fish CSSs, but not present in the bacterial or insect CSS. These results suggest that the intracellular localization of vertebrate CSSs is regulated by not only the NLS, but also the NES sequences.
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Affiliation(s)
- Akiko Fujita
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
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35
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Kendirgi F, Rexer DJ, Alcázar-Román AR, Onishko HM, Wente SR. Interaction between the shuttling mRNA export factor Gle1 and the nucleoporin hCG1: a conserved mechanism in the export of Hsp70 mRNA. Mol Biol Cell 2005; 16:4304-15. [PMID: 16000379 PMCID: PMC1196339 DOI: 10.1091/mbc.e04-11-0998] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Translocation of messenger RNAs through the nuclear pore complex (NPC) requires coordinated physical interactions between stable NPC components, shuttling transport factors, and mRNA-binding proteins. In budding yeast (y) and human (h) cells, Gle1 is an essential mRNA export factor. Nucleocytoplasmic shuttling of hGle1 is required for mRNA export; however, the mechanism by which hGle1 associates with the NPC is unknown. We have previously shown that the interaction of hGle1 with the nucleoporin hNup155 is necessary but not sufficient for targeting hGle1 to NPCs. Here, we report that the unique C-terminal 43 amino acid region of the hGle1B isoform mediates binding to the C-terminal non-FG region of the nucleoporin hCG1/NPL1. Moreover, hNup155, hGle1B, and hCG1 formed a heterotrimeric complex in vitro. This suggested that these two nucleoporins were required for the NPC localization of hGle1. Using an siRNA-based approach, decreased levels of hCG1 resulted in hGle1 accumulation in cytoplasmic foci. This was coincident with inhibition of heat shock-induced production of Hsp70 protein and export of the Hsp70 mRNA in HeLa cells. Because this closely parallels the role of the hCG1 orthologue yNup42/Rip1, we speculate that hGle1-hCG1 function in the mRNA export mechanism is highly conserved.
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Affiliation(s)
- Frederic Kendirgi
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA
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36
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Daelemans D, Costes SV, Lockett S, Pavlakis GN. Kinetic and molecular analysis of nuclear export factor CRM1 association with its cargo in vivo. Mol Cell Biol 2005; 25:728-39. [PMID: 15632073 PMCID: PMC543413 DOI: 10.1128/mcb.25.2.728-739.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2004] [Accepted: 10/21/2004] [Indexed: 11/20/2022] Open
Abstract
The nucleocytoplasmic transport receptor CRM1 mediates the export of macromolecules from the nucleus to the cytoplasm by forming a ternary complex with a cargo molecule and RanGTP. The in vivo mechanism of CRM1 export complex formation and its mobility throughout the nucleus have not been fully elucidated. More information is required to fully understand complex formation and the dynamics of CRM1-cargo-RanGTP complexes in space and time. We demonstrate true molecular interaction of CRM1 with its Rev cargo in living cells by using fluorescence resonance energy transfer (FRET). Interestingly, we found that the inhibitory effect of leptomycin B on this CRM1-cargo interaction is Ran dependent. Using fluorescence recovery after photobleaching (FRAP), we show that CRM1 moves at rates similar to that of free green fluorescent protein in the nucleoplasm. A slower mobility was detected on the nuclear membrane, consistent with known CRM1 interactions with nuclear pores. Based on these data, we propose an in vivo model in which CRM1 roams through the nucleus in search of high-affinity binding sites. CRM1 is able to bind Rev cargo in the nucleolus, and upon RanGTP binding a functional export complex is produced that is exported to the cytoplasm.
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Affiliation(s)
- Dirk Daelemans
- Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium.
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37
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Younis I, Green PL. The human T-cell leukemia virus Rex protein. FRONTIERS IN BIOSCIENCE : A JOURNAL AND VIRTUAL LIBRARY 2005; 10:431-45. [PMID: 15574380 PMCID: PMC2659543 DOI: 10.2741/1539] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A critical step in the life cycle of complex retroviruses, including HTLV-1 and HTLV-2 is the ability of these viruses to adopt a mechanism by which the genome-length unspliced mRNA as well as the partially spliced mRNAs are exported from the nucleus instead of being subjected to splicing or degradation. In HTLV, this is accomplished through the expression of the viral Rex, which recognizes a specific response element on the incompletely spliced mRNAs, stabilizes them, inhibits their splicing, and utilizes the CRM1-dependent cellular pathway for transporting them from the nucleus to the cytoplasm. Rex itself is regulated by phosphorylation, which implies that proper activation of the protein in response to certain cellular cues is an important tool for the virus to ensure that specific viral gene expression is allowed only when the host cell can provide the best conditions for virion production. Having such a critical role in HTLV life cycle, Rex is indispensable for efficient viral replication, infection and spread. Indeed, Rex is considered to regulate the switch between the latent and productive phases of the HTLV life cycle. Without a functional Rex, the virus would still produce regulatory and some accessory gene products; however, structural and enzymatic post-transcriptional gene expression would be severely repressed, essentially leading to non-productive viral replication. More detailed understanding of the exact molecular mechanism of action of Rex will thus allow for better design of therapeutic drugs against Rex function and ultimately HTLV replication. Herein we summarize the progress made towards understanding Rex function and its role in the HTLV life cycle.
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Affiliation(s)
- Ihab Younis
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210
- Molecular, Cellular and Developmental Biology Graduate Program, The Ohio State University, Columbus, OH 43210
| | - Patrick L. Green
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210
- Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, OH 43210
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210
- Molecular, Cellular and Developmental Biology Graduate Program, The Ohio State University, Columbus, OH 43210
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38
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Mingot JM, Bohnsack MT, Jäkle U, Görlich D. Exportin 7 defines a novel general nuclear export pathway. EMBO J 2004; 23:3227-36. [PMID: 15282546 PMCID: PMC514512 DOI: 10.1038/sj.emboj.7600338] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2004] [Accepted: 06/29/2004] [Indexed: 11/09/2022] Open
Abstract
Most transport pathways between cell nucleus and cytoplasm are mediated by nuclear transport receptors of the importin beta family. These receptors are in continuous circulation between the two compartments and transfer cargo molecules from one side of the nuclear envelope to the other. RanBP16 is a family member from higher eukaryotes of so far unknown function. We now show that it exports p50RhoGAP from the nucleus and thereby confines this activity to the cytoplasm. It also accounts for nuclear exclusion of 14-3-3sigma, which in turn is known to anchor, for example, cyclin-dependent kinases in the cytoplasm. Our data further suggest that RanBP16 exports several additional cargoes. It thus appears to be a nuclear export mediator with broad substrate specificity and we will therefore refer to it as exportin 7 (Exp7). Finally, we demonstrate that Exp7-dependent nuclear export signals differ fundamentally from the leucine-rich, CRM1-dependent ones: First, they are not just short linear sequences, but instead include folded motifs. Second, basic residues are critical for Exp7 recruitment.
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39
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Vetter G, Hily JM, Klein E, Schmidlin L, Haas M, Merkle T, Gilmer D. Nucleo-cytoplasmic shuttling of the beet necrotic yellow vein virus RNA-3-encoded p25 protein. J Gen Virol 2004; 85:2459-2469. [PMID: 15269388 DOI: 10.1099/vir.0.80142-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The protein p25 encoded by beet necrotic yellow vein virus (BNYVV) RNA-3 is involved in symptom expression of infected plants. Confocal microscopy analysis of wild-type and mutated p25 fused to GFP and transiently expressed in BY-2 tobacco suspension cells identified a nuclear localization signal (NLS) in the N-terminal part of the protein. Functionality of the NLS was confirmed by pull-down assays using rice and pepper importin-α. Furthermore, it was demonstrated that p25 contains a nuclear export sequence sensitive to leptomycin B. The nuclear export signal (NES) was characterized by mutagenesis. A GFP–p25 fusion protein expressed during a BNYVV infection of Chenopodium quinoa leaves had the same subcellular localization as observed during transient expression in BY-2 cells. The symptom phenotype induced by expression of GFP–p25 during infection was similar to that induced by wild-type virus. Studies with mutated derivatives of GFP–p25 revealed that symptom phenotype was altered when the subcellular localization of GFP–p25 was modified.
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Affiliation(s)
- Guillaume Vetter
- Département de Virologie, Institut de Biologie Moléculaire des Plantes du CNRS, 12 rue du Général Zimmer, 67084 Strasbourg, France
| | - Jean-Michel Hily
- Département de Virologie, Institut de Biologie Moléculaire des Plantes du CNRS, 12 rue du Général Zimmer, 67084 Strasbourg, France
| | - Elodie Klein
- Département de Virologie, Institut de Biologie Moléculaire des Plantes du CNRS, 12 rue du Général Zimmer, 67084 Strasbourg, France
| | - Laure Schmidlin
- Département de Virologie, Institut de Biologie Moléculaire des Plantes du CNRS, 12 rue du Général Zimmer, 67084 Strasbourg, France
| | - Muriel Haas
- Département de Virologie, Institut de Biologie Moléculaire des Plantes du CNRS, 12 rue du Général Zimmer, 67084 Strasbourg, France
| | - Thomas Merkle
- Fakultät für Biologie, Lehrstuhl für Genomforschung, 33594 Bielefeld, Germany
| | - David Gilmer
- Département de Virologie, Institut de Biologie Moléculaire des Plantes du CNRS, 12 rue du Général Zimmer, 67084 Strasbourg, France
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40
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Seewald MJ, Kraemer A, Farkasovsky M, Körner C, Wittinghofer A, Vetter IR. Biochemical characterization of the Ran-RanBP1-RanGAP system: are RanBP proteins and the acidic tail of RanGAP required for the Ran-RanGAP GTPase reaction? Mol Cell Biol 2003; 23:8124-36. [PMID: 14585972 PMCID: PMC262373 DOI: 10.1128/mcb.23.22.8124-8136.2003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
RanBP type proteins have been reported to increase the catalytic efficiency of the RanGAP-mediated GTPase reaction on Ran. Since the structure of the Ran-RanBP1-RanGAP complex showed RanBP1 to be located away from the active site, we reinvestigated the reaction using fluorescence spectroscopy under pre-steady-state conditions. We can show that RanBP1 indeed does not influence the rate-limiting step of the reaction, which is the cleavage of GTP and/or the release of product P(i). It does, however, influence the dynamics of the Ran-RanGAP interaction, its most dramatic effect being the 20-fold stimulation of the already very fast association reaction such that it is under diffusion control (4.5 x 10(8) M(-1) s(-1)). Having established a valuable kinetic system for the interaction analysis, we also found, in contrast to previous findings, that the highly conserved acidic C-terminal end of RanGAP is not required for the switch-off reaction. Rather, genetic experiments in Saccharomyces cerevisiae demonstrate a profound effect of the acidic tail on microtubule organization during mitosis. We propose that the acidic tail of RanGAP is required for a process during mitosis.
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Affiliation(s)
- Michael J Seewald
- Max-Planck Institut für Molekulare Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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41
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Di Fiore B, Ciciarello M, Mangiacasale R, Palena A, Tassin AM, Cundari E, Lavia P. Mammalian RanBP1 regulates centrosome cohesion during mitosis. J Cell Sci 2003; 116:3399-411. [PMID: 12840069 DOI: 10.1242/jcs.00624] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Ran GTPase plays a central function in control of nucleo-cytoplasmic transport in interphase. Mitotic roles of Ran have also been firmly established in Xenopus oocyte extracts. In this system, Ran-GTP, or the RCC1 exchange factor for Ran, drive spindle assembly by regulating the availability of 'aster-promoting activities'. In previous studies to assess whether the Ran network also influences mitosis in mammalian cells, we found that overexpression of Ran-binding protein 1 (RanBP1), a major effector of Ran, induces multipolar spindles. We now show that these abnormal spindles are generated through loss of cohesion in mitotic centrosomes. Specifically, RanBP1 excess induces splitting of mother and daughter centrioles at spindle poles; the resulting split centrioles can individually organize functional microtubule arrays, giving rise to functional spindle poles. RanBP1-dependent centrosome splitting is specifically induced in mitosis and requires microtubule integrity and Eg5 activity. In addition, we have identified a fraction of RanBP1 at the centrosome. These data indicate that overexpressed RanBP1 interferes with crucial factor(s) that control structural and dynamic features of centrosomes during mitosis and contribute to uncover novel mitotic functions downstream of the Ran network.
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Affiliation(s)
- Barbara Di Fiore
- CNR Institute of Molecular Biology and Pathology, Section of Genetics, c/o University 'La Sapienza', 00185 Rome, Italy
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Rodriguez JA, Span SW, Kruyt FAE, Giaccone G. Subcellular localization of CrmA: identification of a novel leucine-rich nuclear export signal conserved in anti-apoptotic serpins. Biochem J 2003; 373:251-9. [PMID: 12667137 PMCID: PMC1223470 DOI: 10.1042/bj20030289] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2003] [Accepted: 04/01/2003] [Indexed: 11/17/2022]
Abstract
The cowpox virus-encoded anti-apoptotic protein cytokine response modifier A (CrmA) is a member of the serpin family that specifically inhibits the cellular proteins caspase 1, caspase 8 and granzyme B. In this study, we have used Flag- and yellow fluorescent protein (YFP)-tagged versions of CrmA to investigate the mechanisms that regulate its subcellular localization. We show that CrmA can actively enter and exit the nucleus and we demonstrate the role of the nuclear export receptor CRM1 in this shuttling process. CrmA contains a novel leucine-rich nuclear export signal (NES) that is functionally conserved in the anti-apoptotic cellular serpin PI-9. Besides this leucine-rich export signal, additional sequences mapping to a 103-amino-acid region flanking the NES contribute to the CRM1-dependent nuclear export of CrmA. Although YFP-tagged CrmA is primarily located in the cytoplasm, shifting its localization to be predominantly nuclear by fusion of a heterologous nuclear localization signal did not impair its ability to prevent Fas-induced apoptosis. We propose that nucleocytoplasmic shuttling would allow CrmA to efficiently target cellular pro-apoptotic proteins not only in the cytoplasm, but also in the nucleus, and thus to carry out its anti-apoptotic function in both compartments.
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Affiliation(s)
- Jose A Rodriguez
- Department of Medical Oncology, VU University Medical Center, HV1081 Amsterdam, The Netherlands.
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Kim SH, Roux SJ. An Arabidopsis Ran-binding protein, AtRanBP1c, is a co-activator of Ran GTPase-activating protein and requires the C-terminus for its cytoplasmic localization. PLANTA 2003; 216:1047-1052. [PMID: 12687374 DOI: 10.1007/s00425-002-0959-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2002] [Accepted: 11/16/2002] [Indexed: 05/24/2023]
Abstract
Ran-binding proteins (RanBPs) are a group of proteins that bind to Ran (Ras-related nuclear small GTP-binding protein), and thus either control the GTP/GDP-bound states of Ran or help couple the Ran GTPase cycle to a cellular process. AtRanBP1c is a Ran-binding protein from Arabidopsis thaliana (L.) Heynh. that was recently shown to be critically involved in the regulation of auxin-induced mitotic progression [S.-H. Kim et al. (2001) Plant Cell 13:2619-2630]. Here we report that AtRanBP1c inhibits the EDTA-induced release of GTP from Ran and serves as a co-activator of Ran-GTPase-activating protein (RanGAP) in vitro. Transient expression of AtRanBP1c fused to a beta-glucuronidase (GUS) reporter reveals that the protein localizes primarily to the cytosol. Neither the N- nor C-terminus of AtRanBP1c, which flank the Ran-binding domain (RanBD), is necessary for the binding of PsRan1-GTP to the protein, but both are needed for the cytosolic localization of GUS-fused AtRanBP1c. These findings, together with a previous report that AtRanBP1c is critically involved in root growth and development, imply that the promotion of GTP hydrolysis by the Ran/RanGAP/AtRanBP1c complex in the cytoplasm, and the resulting concentration gradient of Ran-GDP to Ran-GTP across the nuclear membrane could be important in the regulation of auxin-induced mitotic progression in root tips of A. thaliana.
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Affiliation(s)
- Soo-Hwan Kim
- Section of Molecular Cell and Developmental Biology, University of Texas, Austin, TX 78712, USA
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Steggerda SM, Paschal BM. Regulation of nuclear import and export by the GTPase Ran. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 217:41-91. [PMID: 12019565 DOI: 10.1016/s0074-7696(02)17012-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
This review focuses on the control of nuclear import and export pathways by the small GTPase Ran. Transport of signal-containing cargo substrates is mediated by receptors that bind to the cargo proteins and RNAs and deliver them to the appropriate cellular compartment. Ran is an evolutionarily conserved member of the Ras superfamily that regulates all receptor-mediated transport between the nucleus and the cytoplasm. We describe the identification and characterization of the RanGTPase and its binding partners: the guanine nucleotide exchange factor, RanGEF; the GTPase activating protein, RanGAP; the soluble import and export receptors; Ran-binding domain-(RBD) containing proteins; and NTF2 and related factors.
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Affiliation(s)
- Susanne M Steggerda
- Center for Cell Signaling and Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville 22908, USA
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Zhang C, Goldberg MW, Moore WJ, Allen TD, Clarke PR. Concentration of Ran on chromatin induces decondensation, nuclear envelope formation and nuclear pore complex assembly. Eur J Cell Biol 2002; 81:623-33. [PMID: 12494999 DOI: 10.1078/0171-9335-00288] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nuclear envelope (NE) formation can be studied in a cell-free system made from Xenopus eggs. In this system, NE formation involves the small GTPase Ran. Ran associates with chromatin early in nuclear assembly and concentration of Ran on inert beads is sufficient to induce NE formation. Here, we show that Ran binds to chromatin prior to NE formation and recruits RCC1, the nucleotide exchange factor that generates Ran-GTP. In extracts prepared by high-speed centrifugation, increased concentrations of Ran are sufficient to induce chromatin decondensation and NE assembly. Using field emission in-lens scanning electron microscopy (FEISEM), we show that Ran promotes the formation of smoothed membranes and the assembly of nuclear pore complexes (NPCs). In contrast, RanT24N, a mutant that fails to bind GTP and inhibits RCC1, does not support efficient NE assembly, whereas RanQ69L, a mutant locked in a GTP-bound state, permits some membrane vesicle recruitment to chromatin, but inhibits vesicle fusion and NPC assembly. Thus, binding of Ran to chromatin, followed by local generation of Ran-GTP and GTP hydrolysis by Ran, induces chromatin decondensation, membrane vesicle recruitment, membrane formation and NPC assembly. We propose that the biological activity of Ran is determined by its targeting to structures such as chromatin as well as its guanine nucleotide bound state.
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Affiliation(s)
- Chuanmao Zhang
- Biomedical Research Centre, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, UK
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Fornerod M, Ohno M. Exportin-mediated nuclear export of proteins and ribonucleoproteins. Results Probl Cell Differ 2002; 35:67-91. [PMID: 11791409 DOI: 10.1007/978-3-540-44603-3_4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Maarten Fornerod
- EMBL, Gene Expression Programme, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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Plafker K, Macara IG. Fluorescence resonance energy transfer biosensors that detect Ran conformational changes and a Ran x GDP-importin-beta -RanBP1 complex in vitro and in intact cells. J Biol Chem 2002; 277:30121-7. [PMID: 12034733 DOI: 10.1074/jbc.m203006200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ran GTPase plays a central role in nucleocytoplasmic transport. Association of Ran x GTP with transport carriers (karyopherins) triggers the loading/unloading of export or import cargo, respectively. The C-terminal tail of Ran x GTP is deployed in an extended conformation when associated with a Ran binding domain or importins. To monitor tail orientation, a Ran-GFP fusion was labeled with the fluorophore Alexa546. Fluorescence resonance energy transfer (FRET) occurs efficiently between the green fluorescent protein (GFP) and Alexa546 for Ran x GDP and Ran x GTP, suggesting that the tail is tethered in both states. However, Ran x GTP complexes with importin-beta, RanBP1, and Crm1 all show reduced FRET consistent with tail extension. Displacement of the C-terminal tail of Ran by karyopherins may be a general mechanism to facilitate RanBP1 binding. A Ran x GDP-RanBP1-importin-beta complex also displayed a low FRET signal. To detect this complex in vivo, a bipartite biosensor consisting of Ran-Alexa546 plus GST-GFP-RanBP1, was co-injected into the cytoplasm of cells. The Ran redistributed predominantly to the nucleus, and RanBP1 remained cytoplasmic. Nonetheless, a robust cytoplasmic FRET signal was detectable, which suggests that a significant fraction of cytoplasmic Ran.GDP may exist in a ternary complex with RanBP1 and importins.
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Affiliation(s)
- Kendra Plafker
- Center for Cell Signaling and the Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908-0577, USA
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Hanaka H, Shimizu T, Izumi T. Nuclear-localization-signal-dependent and nuclear-export-signal-dependent mechanisms determine the localization of 5-lipoxygenase. Biochem J 2002; 361:505-14. [PMID: 11802780 PMCID: PMC1222333 DOI: 10.1042/0264-6021:3610505] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
5-Lipoxygenase (5-LO) metabolizes arachidonic acid to leukotriene A4, a key intermediate in leukotriene biosynthesis. To explore the molecular mechanisms of its cell-specific localization, a fusion protein between green fluorescent protein (GFP) and human 5-LO (GFP-5LO) was expressed in various cells. GFP-5LO was localized in the cytosol in HL-60 cells and in both the nucleus and the cytosol in RBL (rat basophilic leukaemia) cells, similarly to the native enzyme in these cells. The localization of GFP fusion proteins for mutant 5-LOs in a putative bipartite nuclear localization signal (NLS), amino acids 638-655, in Chinese hamster ovary (CHO)-K1 and Swiss3T3 cells revealed that this motif is important for the nuclear localization of 5-LO. A GFP fusion protein of this short peptide localized consistently in the nucleus. Leptomycin B, a specific inhibitor of nuclear export signal (NES)-dependent transport, diminished the cytosolic localization of 5-LO in HL-60 cells and that of GFP-5LO in CHO-K1 cells, suggesting that an NES-system might also function in determining 5-LO localization. Analysis of the localization of 5-LO during the cell cycle points to a controlled movement of this enzyme. Thus we conclude that a balance of NLS- and NES-dependent mechanisms determines the cell-type-specific localization of 5-LO, suggesting a nuclear function for this enzyme.
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Affiliation(s)
- Hiromi Hanaka
- Department of Biochemistry, Gunma University School of Medicine, 3-39-22 Showamachi, Maebashi, Gunma 371-8511, Japan
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Abstract
A defining characteristic of eukaryotic cells is the possession of a nuclear envelope. Transport of macromolecules between the nuclear and cytoplasmic compartments occurs through nuclear pore complexes that span the double membrane of this envelope. The molecular basis for transport has been revealed only within the last few years. The transport mechanism lacks motors and pumps and instead operates by a process of facilitated diffusion of soluble carrier proteins, in which vectoriality is provided by compartment-specific assembly and disassembly of cargo-carrier complexes. The carriers recognize localization signals on the cargo and can bind to pore proteins. They also bind a small GTPase, Ran, whose GTP-bound form is predominantly nuclear. Ran-GTP dissociates import carriers from their cargo and promotes the assembly of export carriers with cargo. The ongoing discovery of numerous carriers, Ran-independent transport mechanisms, and cofactors highlights the complexity of the nuclear transport process. Multiple regulatory mechanisms are also being identified that control cargo-carrier interactions. Circadian rhythms, cell cycle, transcription, RNA processing, and signal transduction are all regulated at the level of nucleocytoplasmic transport. This review focuses on recent discoveries in the field, with an emphasis on the carriers and cofactors involved in transport and on possible mechanisms for movement through the nuclear pores.
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Affiliation(s)
- I G Macara
- Center for Cell Signaling, University of Virginia, Charlottesville, Virginia 22908-0577, USA.
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Affiliation(s)
- Y Huang
- Department of Microbiology, University of Connecticut Health Center, Farmington, CT 06030, USA
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