1
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Mboukou A, Rajendra V, Kleinova R, Tisné C, Jantsch MF, Barraud P. Transportin-1: A Nuclear Import Receptor with Moonlighting Functions. Front Mol Biosci 2021; 8:638149. [PMID: 33681296 PMCID: PMC7930572 DOI: 10.3389/fmolb.2021.638149] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Accepted: 01/13/2021] [Indexed: 12/11/2022] Open
Abstract
Transportin-1 (Trn1), also known as karyopherin-β2 (Kapβ2), is probably the best-characterized nuclear import receptor of the karyopherin-β family after Importin-β, but certain aspects of its functions in cells are still puzzling or are just recently emerging. Since the initial identification of Trn1 as the nuclear import receptor of hnRNP A1 ∼25 years ago, several molecular and structural studies have unveiled and refined our understanding of Trn1-mediated nuclear import. In particular, the understanding at a molecular level of the NLS recognition by Trn1 made a decisive step forward with the identification of a new class of NLSs called PY-NLSs, which constitute the best-characterized substrates of Trn1. Besides PY-NLSs, many Trn1 cargoes harbour NLSs that do not resemble the archetypical PY-NLS, which complicates the global understanding of cargo recognition by Trn1. Although PY-NLS recognition is well established and supported by several structures, the recognition of non-PY-NLSs by Trn1 is far less understood, but recent reports have started to shed light on the recognition of this type of NLSs. Aside from its principal and long-established activity as a nuclear import receptor, Trn1 was shown more recently to moonlight outside nuclear import. Trn1 has for instance been caught in participating in virus uncoating, ciliary transport and in modulating the phase separation properties of aggregation-prone proteins. Here, we focus on the structural and functional aspects of Trn1-mediated nuclear import, as well as on the moonlighting activities of Trn1.
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Affiliation(s)
- Allegra Mboukou
- Expression Génétique Microbienne, Institut de Biologie Physico-Chimique (IBPC), UMR 8261, CNRS, Université de Paris, Paris, France
| | - Vinod Rajendra
- Department of Cell and Developmental Biology, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | - Renata Kleinova
- Department of Cell and Developmental Biology, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | - Carine Tisné
- Expression Génétique Microbienne, Institut de Biologie Physico-Chimique (IBPC), UMR 8261, CNRS, Université de Paris, Paris, France
| | - Michael F. Jantsch
- Department of Cell and Developmental Biology, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | - Pierre Barraud
- Expression Génétique Microbienne, Institut de Biologie Physico-Chimique (IBPC), UMR 8261, CNRS, Université de Paris, Paris, France
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2
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Lee J, Park J, Kim JH, Lee G, Park TE, Yoon KJ, Kim YK, Lim C. LSM12-EPAC1 defines a neuroprotective pathway that sustains the nucleocytoplasmic RAN gradient. PLoS Biol 2020; 18:e3001002. [PMID: 33362237 PMCID: PMC7757817 DOI: 10.1371/journal.pbio.3001002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 11/19/2020] [Indexed: 02/07/2023] Open
Abstract
Nucleocytoplasmic transport (NCT) defects have been implicated in neurodegenerative diseases such as C9ORF72-associated amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). Here, we identify a neuroprotective pathway of like-Sm protein 12 (LSM12) and exchange protein directly activated by cyclic AMP 1 (EPAC1) that sustains the nucleocytoplasmic RAN gradient and thereby suppresses NCT dysfunction by the C9ORF72-derived poly(glycine-arginine) protein. LSM12 depletion in human neuroblastoma cells aggravated poly(GR)-induced impairment of NCT and nuclear integrity while promoting the nuclear accumulation of poly(GR) granules. In fact, LSM12 posttranscriptionally up-regulated EPAC1 expression, whereas EPAC1 overexpression rescued the RAN gradient and NCT defects in LSM12-deleted cells. C9-ALS patient-derived neurons differentiated from induced pluripotent stem cells (C9-ALS iPSNs) displayed low expression of LSM12 and EPAC1. Lentiviral overexpression of LSM12 or EPAC1 indeed restored the RAN gradient, mitigated the pathogenic mislocalization of TDP-43, and suppressed caspase-3 activation for apoptosis in C9-ALS iPSNs. EPAC1 depletion biochemically dissociated RAN-importin β1 from the cytoplasmic nuclear pore complex, thereby dissipating the nucleocytoplasmic RAN gradient essential for NCT. These findings define the LSM12-EPAC1 pathway as an important suppressor of the NCT-related pathologies in C9-ALS/FTD. A post-transcriptional circuit comprising LSM12 and EPAC1 suppresses neurodegenerative pathologies in C9ORF72-associated amyotrophic lateral sclerosis by establishing the RAN gradient and sustaining nucleocytoplasmic transport.
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Affiliation(s)
- Jongbo Lee
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Jumin Park
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Ji-hyung Kim
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Giwook Lee
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Tae-Eun Park
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Ki-Jun Yoon
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - Yoon Ki Kim
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul, Republic of Korea
- Division of Life Sciences, Korea University, Seoul, Republic of Korea
| | - Chunghun Lim
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
- * E-mail:
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3
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Huang YA, Hsu CH, Chiu HC, Hsi PY, Ho CT, Lo WL, Hwang E. Actin waves transport RanGTP to the neurite tip to regulate non-centrosomal microtubules in neurons. J Cell Sci 2020; 133:jcs241992. [PMID: 32253322 DOI: 10.1242/jcs.241992] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 03/17/2020] [Indexed: 12/18/2022] Open
Abstract
Microtubules (MTs) are the most abundant cytoskeleton in neurons, and control multiple facets of their development. While the MT-organizing center (MTOC) in mitotic cells is typically located at the centrosome, the MTOC in neurons switches to non-centrosomal sites. A handful of cellular components have been shown to promote non-centrosomal MT (ncMT) formation in neurons, yet the regulation mechanism remains unknown. Here, we demonstrate that the small GTPase Ran is a key regulator of ncMTs in neurons. Using an optogenetic tool that enables light-induced local production of RanGTP, we demonstrate that RanGTP promotes ncMT plus-end growth along the neurite. Additionally, we discovered that actin waves drive the anterograde transport of RanGTP. Pharmacological disruption of actin waves abolishes the enrichment of RanGTP and reduces growing ncMT plus-ends at the neurite tip. These observations identify a novel regulation mechanism for ncMTs and pinpoint an indirect connection between the actin and MT cytoskeletons in neurons.
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Affiliation(s)
- Yung-An Huang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Chih-Hsuan Hsu
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Ho-Chieh Chiu
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Pei-Yu Hsi
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Chris T Ho
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Wei-Lun Lo
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Eric Hwang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan 30068
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
- Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, Taiwan 30068
- Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Chiao Tung University, Hsinchu, Taiwan 30068
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4
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Port SA, Monecke T, Dickmanns A, Spillner C, Hofele R, Urlaub H, Ficner R, Kehlenbach RH. Structural and Functional Characterization of CRM1-Nup214 Interactions Reveals Multiple FG-Binding Sites Involved in Nuclear Export. Cell Rep 2015; 13:690-702. [PMID: 26489467 DOI: 10.1016/j.celrep.2015.09.042] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 08/11/2015] [Accepted: 09/14/2015] [Indexed: 12/11/2022] Open
Abstract
CRM1 is the major nuclear export receptor. During translocation through the nuclear pore, transport complexes transiently interact with phenylalanine-glycine (FG) repeats of multiple nucleoporins. On the cytoplasmic side of the nuclear pore, CRM1 tightly interacts with the nucleoporin Nup214. Here, we present the crystal structure of a 117-amino-acid FG-repeat-containing fragment of Nup214, in complex with CRM1, Snurportin 1, and RanGTP at 2.85 Å resolution. The structure reveals eight binding sites for Nup214 FG motifs on CRM1, with intervening stretches that are loosely attached to the transport receptor. Nup214 binds to N- and C-terminal regions of CRM1, thereby clamping CRM1 in a closed conformation and stabilizing the export complex. The role of conserved hydrophobic pockets for the recognition of FG motifs was analyzed in biochemical and cell-based assays. Comparative studies with RanBP3 and Nup62 shed light on specificities of CRM1-nucleoporin binding, which serves as a paradigm for transport receptor-nucleoporin interactions.
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Affiliation(s)
- Sarah A Port
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Thomas Monecke
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, GZMB, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Achim Dickmanns
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, GZMB, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Christiane Spillner
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Romina Hofele
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany; Bioanalytics, Institute for Clinical Chemistry, University Medical Center, Robert-Koch-Str. 40, 37075 Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany; Bioanalytics, Institute for Clinical Chemistry, University Medical Center, Robert-Koch-Str. 40, 37075 Göttingen, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, GZMB, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
| | - Ralph H Kehlenbach
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
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5
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Andersen KR, Onischenko E, Tang JH, Kumar P, Chen JZ, Ulrich A, Liphardt JT, Weis K, Schwartz TU. Scaffold nucleoporins Nup188 and Nup192 share structural and functional properties with nuclear transport receptors. eLife 2013; 2:e00745. [PMID: 23795296 PMCID: PMC3679522 DOI: 10.7554/elife.00745] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 05/08/2013] [Indexed: 02/07/2023] Open
Abstract
Nucleocytoplasmic transport is mediated by nuclear pore complexes (NPCs) embedded in the nuclear envelope. About 30 different proteins (nucleoporins, nups) arrange around a central eightfold rotational axis to build the modular NPC. Nup188 and Nup192 are related and evolutionary conserved, large nucleoporins that are part of the NPC scaffold. Here we determine the structure of Nup188. The protein folds into an extended stack of helices where an N-terminal 130 kDa segment forms an intricate closed ring, while the C-terminal region is a more regular, superhelical structure. Overall, the structure has distant similarity with flexible S-shaped nuclear transport receptors (NTRs). Intriguingly, like NTRs, both Nup188 and Nup192 specifically bind FG-repeats and are able to translocate through NPCs by facilitated diffusion. This blurs the existing dogma of a clear distinction between stationary nups and soluble NTRs and suggests an evolutionary relationship between the NPC and the soluble nuclear transport machinery. DOI:http://dx.doi.org/10.7554/eLife.00745.001 The nucleus of a cell is surrounded by a two-layered membrane that controls the flow of molecules from the cytoplasm into the nucleus and vice versa. The molecular traffic between the cytoplasm and nucleus is essentially controlled by nuclear pore complexes—large, multi-protein structures that are embedded in the membrane. Each nuclear pore complex contains about 30 different proteins called nucleoporins or nups, which combine to form a structure with a central pore that allows the molecules to enter and leave the nucleus. The centre of the nuclear pore complex is thought to be filled with protein filaments that contain a large number of so-called FG repeats (where F and G are the amino acids phenylalanine and glycine). Specialized molecules called soluble nuclear transport receptors, which carry various cargoes between the cytoplasm and nucleus, can bind to these FG repeats, and the interaction between the receptors and the FG repeats is crucial for the selective transport of molecules between the cytoplasm and the nucleus. The large size of the nuclear pore complex has hindered efforts to work out its structure, but in recent years researchers have been able to obtain structures for many individual nups and their subcomplexes. Now, Andersen et al. have determined the structure of one of the largest nups, Nup188. This has led to the discovery that it and a related nup, Nup192, share unexpected features with soluble nuclear transport receptors. In general the first step when attempting to determine the structure of a biomolecule is to form a crystal. Since full-length Nup188 did not crystallize, Andersen et al. instead crystallized two large fragments of Nup188, determined the structures of these fragments, and then combined these to produce the likely structure of the full-length protein. They found that Nup188 has a structure that consists of stacked helices and is more flexible than other nups. Moreover, its structure was very similar to those of soluble nuclear transport receptors, and this led Andersen et al. to investigate whether Nup188 also had similar functional features. Surprisingly, they discovered that both Nup188 and Nup192 could bind FG repeats, just like nuclear transport receptors. What is more, this binding allowed both nups to travel through nuclear pore complexes in in vitro transport reactions. These findings have implications for the understanding of the organization and function of FG-repeats and suggest that the stationary elements of the nuclear pore complex and soluble nuclear transport receptors are evolutionarily related. DOI:http://dx.doi.org/10.7554/eLife.00745.002
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Affiliation(s)
- Kasper R Andersen
- Department of Biology , Massachusetts Institute of Technology , Cambridge , United States
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6
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Abstract
Exchange of macromolecules between the nucleus and cytoplasm is a key regulatory event in the expression of a cell's genome. This exchange requires a dedicated transport system: (1) nuclear pore complexes (NPCs), embedded in the nuclear envelope and composed of proteins termed nucleoporins (or "Nups"), and (2) nuclear transport factors that recognize the cargoes to be transported and ferry them across the NPCs. This transport is regulated at multiple levels, and the NPC itself also plays a key regulatory role in gene expression by influencing nuclear architecture and acting as a point of control for various nuclear processes. Here we summarize how the yeast Saccharomyces has been used extensively as a model system to understand the fundamental and highly conserved features of this transport system, revealing the structure and function of the NPC; the NPC's role in the regulation of gene expression; and the interactions of transport factors with their cargoes, regulatory factors, and specific nucleoporins.
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7
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Braun K, Beining M, Wiessler M, Lammers T, Pipkorn R, Hennrich U, Nokihara K, Semmler W, Debus J, Waldeck W. BioShuttle mobility in living cells studied with high-resolution FCS & CLSM methodologies. Int J Med Sci 2012; 9:339-52. [PMID: 22811608 PMCID: PMC3399214 DOI: 10.7150/ijms.4414] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 06/18/2012] [Indexed: 01/04/2023] Open
Abstract
With the increase in molecular diagnostics and patient-specific therapeutic approaches, the delivery and targeting of imaging molecules and pharmacologically active agents gain increasing importance. The ideal delivery system does not exist yet. The realization of two features is indispensable: first, a locally high concentration of target-specific diagnostic and therapeutic molecules; second, the broad development of effective and safe carrier systems. Here we characterize the transport properties of the peptide-based BioShuttle transporter using FFM and CLSM methods. The modular design of BioShuttle-based formulations results in a multi-faceted field of applications, also as a theranostic tool.
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Affiliation(s)
- Klaus Braun
- Dept. of Imaging and Radiooncology, German Cancer Research Center, Im Neuenheimer Feld 280, Heidelberg, Germany.
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8
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McGuire AT, Mangroo D. Cex1p facilitates Rna1p-mediated dissociation of the Los1p-tRNA-Gsp1p-GTP export complex. Traffic 2011; 13:234-56. [PMID: 22008473 DOI: 10.1111/j.1600-0854.2011.01304.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 10/17/2011] [Accepted: 10/17/2011] [Indexed: 01/17/2023]
Abstract
Nuclear tRNA export plays an essential role in key cellular processes such as regulation of protein synthesis, cell cycle progression, response to nutrient availability and DNA damage and development. Like other nuclear export processes, assembly of the nuclear tRNA export complex in the nucleus is dependent on Ran-GTP/Gsp1p-GTP, and dissociation of the export receptor-tRNA-Ran-GTP/Gsp1p-GTP complex in the cytoplasm requires RanBP1/Yrb1p and RanGAP/Rna1p to activate the GTPase activity of Ran-GTP/Gsp1p-GTP. The Saccharomyces cerevisiae Cex1p and Human Scyl1 have also been proposed to participate in unloading of the tRNA export receptors at the cytoplasmic face of the nuclear pore complex (NPC). Here, we provide evidence suggesting that Cex1p is required for activation of the GTPase activity of Gsp1p and dissociation of the receptor-tRNA-Gsp1p export complex in S. cerevisiae. The data suggest that Cex1p recruits Rna1p from the cytoplasm to the NPC and facilitates Rna1p activation of the GTPase activity of Gsp1p by enabling Rna1p to gain access to Gsp1p-GTP bound to the export receptor tRNA complex. It is possible that this tRNA unloading mechanism is conserved in evolutionarily diverse organisms and that other Gsp1p-GTP-dependent export processes use a pathway-specific component to recruit Rna1p to the NPC.
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Affiliation(s)
- Andrew T McGuire
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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9
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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: 158] [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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10
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Soderholm JF, Bird SL, Kalab P, Sampathkumar Y, Hasegawa K, Uehara-Bingen M, Weis K, Heald R. Importazole, a small molecule inhibitor of the transport receptor importin-β. ACS Chem Biol 2011; 6:700-8. [PMID: 21469738 PMCID: PMC3137676 DOI: 10.1021/cb2000296] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
During interphase, the transport receptor importin-β carries cargoes into the nucleus, where RanGTP releases them. A similar mechanism operates in mitosis to generate a gradient of active spindle assembly factors around mitotic chromosomes. Importin-β and RanGTP have been implicated in additional cellular processes, but the precise roles of the Ran/importin-β pathway throughout the cell cycle remain poorly understood. We implemented a FRET-based, high-throughput small molecule screen for compounds that interfere with the interaction between RanGTP and importin-β and identified importazole, a 2,4-diaminoquinazoline. Importazole specifically blocks importin-β-mediated nuclear import both in Xenopus egg extracts and cultured cells, without disrupting transportin-mediated nuclear import or CRM1-mediated nuclear export. When added during mitosis, importazole impairs the release of an importin-β cargo FRET probe and causes both predicted and novel defects in spindle assembly. Together, these results indicate that importazole specifically inhibits the function of importin-β, likely by altering its interaction with RanGTP. Importazole is a valuable tool to evaluate the function of the importin-β/RanGTP pathway at specific stages during the cell cycle.
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Affiliation(s)
- Jonathan F Soderholm
- The Department of Molecular and Cell Biology, University of California, Berkeley, MC 3200 LSA, Berkeley, California 94720-3200, United States
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11
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The nuclear localization of low risk HPV11 E7 protein mediated by its zinc binding domain is independent of nuclear import receptors. Virology 2010; 407:100-9. [PMID: 20800258 DOI: 10.1016/j.virol.2010.07.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 05/13/2010] [Accepted: 07/28/2010] [Indexed: 12/13/2022]
Abstract
We investigated the nuclear import of low risk HPV11 E7 protein using 1) transfection assays in HeLa cells with EGFP fusion plasmids containing 11E7 and its domains and 2) nuclear import assays in digitonin-permeabilized HeLa cells with GST fusion proteins containing 11E7 and its domains. The EGFP-11E7 and EGFP-11cE7(39-98) localized mostly to the nucleus. The GST-11E7 and GST-11cE7(39-98) were imported into the nuclei in the presence of either Ran-GDP or RanG19V-GTP mutant and in the absence of nuclear import receptors. This suggests that 11E7 enters the nucleus via a Ran-dependent pathway, independent of nuclear import receptors, mediated by a nuclear localization signal located in its C-terminal domain (cNLS). This cNLS contains the zinc binding domain consisting of two copies of Cys-X-X-Cys motif. Mutagenesis of Cys residues in these motifs changed the localization of the EGFP-11cE7/-11E7 mutants to cytoplasmic, suggesting that the zinc binding domain is essential for nuclear localization of 11E7.
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12
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Abstract
Internal membrane bound structures sequester all genetic material in eukaryotic cells. The most prominent of these structures is the nucleus, which is bounded by a double membrane termed the nuclear envelope (NE). Though this NE separates the nucleoplasm and genetic material within the nucleus from the surrounding cytoplasm, it is studded throughout with portals called nuclear pore complexes (NPCs). The NPC is a highly selective, bidirectional transporter for a tremendous range of protein and ribonucleoprotein cargoes. All the while the NPC must prevent the passage of nonspecific macromolecules, yet allow the free diffusion of water, sugars, and ions. These many types of nuclear transport are regulated at multiple stages, and the NPC carries binding sites for many of the proteins that modulate and modify the cargoes as they pass across the NE. Assembly, maintenance, and repair of the NPC must somehow occur while maintaining the integrity of the NE. Finally, the NPC appears to be an anchor for localization of many nuclear processes, including gene activation and cell cycle regulation. All these requirements demonstrate the complex design of the NPC and the integral role it plays in key cellular processes.
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Affiliation(s)
- Susan R Wente
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
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13
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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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14
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Soh S, Byrska M, Kandere-Grzybowska K, Grzybowski BA. Reaction-diffusion systems in intracellular molecular transport and control. Angew Chem Int Ed Engl 2010; 49:4170-98. [PMID: 20518023 PMCID: PMC3697936 DOI: 10.1002/anie.200905513] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Chemical reactions make cells work only if the participating chemicals are delivered to desired locations in a timely and precise fashion. Most research to date has focused on active-transport mechanisms, although passive diffusion is often equally rapid and energetically less costly. Capitalizing on these advantages, cells have developed sophisticated reaction-diffusion (RD) systems that control a wide range of cellular functions-from chemotaxis and cell division, through signaling cascades and oscillations, to cell motility. These apparently diverse systems share many common features and are "wired" according to "generic" motifs such as nonlinear kinetics, autocatalysis, and feedback loops. Understanding the operation of these complex (bio)chemical systems requires the analysis of pertinent transport-kinetic equations or, at least on a qualitative level, of the characteristic times of the constituent subprocesses. Therefore, in reviewing the manifestations of cellular RD, we also describe basic theory of reaction-diffusion phenomena.
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Affiliation(s)
- Siowling Soh
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208
| | - Marta Byrska
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208
| | - Kristiana Kandere-Grzybowska
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208
| | - Bartosz A. Grzybowski
- Department of Chemistry, Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, Homepage: http://www.dysa.northwestern.edu
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Soh S, Byrska M, Kandere-Grzybowska K, Grzybowski B. Reaktions-Diffusions-Systeme für intrazellulären Transport und Kontrolle. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200905513] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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16
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Antony PMA, Mäntele S, Mollenkopf P, Boy J, Kehlenbach RH, Riess O, Schmidt T. Identification and functional dissection of localization signals within ataxin-3. Neurobiol Dis 2009; 36:280-92. [DOI: 10.1016/j.nbd.2009.07.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 07/22/2009] [Accepted: 07/27/2009] [Indexed: 10/20/2022] Open
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Ploski JE, Topisirovic I, Park KW, Borden KLB, Radu A. A mechanism of nucleocytoplasmic trafficking for the homeodomain protein PRH. Mol Cell Biochem 2009; 332:173-81. [PMID: 19588232 DOI: 10.1007/s11010-009-0188-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Accepted: 06/25/2009] [Indexed: 11/24/2022]
Abstract
Proline-rich homeodomain (PRH)/hematopoietically expressed homeodomain (Hex) is a homeodomain protein that plays an important role in early embryonic patterning and hematopoiesis. PRH can act as either a tumor suppressor or an oncogene and its expression is dysregulated in certain types of lymphoid and myeloid leukemias. Aberrant exclusion of PRH from the nuclei has been associated with thyroid and breast cancers and a subset of myeloid leukemias. Accordingly, nuclear localization of PRH was found to be necessary for the inhibition of eIF4E-dependent transformation. Since PRH's nuclear-cytoplasmic localization has been associated with neoplastic transformation we sought to better understand how PRH is transported to the nuclear compartment. Here, we report an essential element that controls the mechanism of PRH nucleocytoplasmic trafficking, namely that it is imported into the nuclei by Karyopherin/Importin 7. Kap7 was identified as a binding partner for PRH in a GST-pull down from a HeLa cell protein lysate, followed by mass-spectrometry. The Kap7-PRH complex is dissociated in the presence of RanGTP, as expected for a nuclear import complex. Kap7 can bind directly to PRH in a GST-pull down assay with purified proteins, as well as mediates the transport of PRH to the nuclear compartment in a digitonin permeabilized cells assay. Finally, in vivo depletion of Kap7 dramatically reduces accumulation of PRH in the nucleus. Our data open the way for investigations of the mechanism of perturbed PRH localization in tumors and possible therapeutic interventions.
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Kap95p binding induces the switch loops of RanGDP to adopt the GTP-bound conformation: implications for nuclear import complex assembly dynamics. J Mol Biol 2008; 383:772-82. [PMID: 18708071 DOI: 10.1016/j.jmb.2008.07.090] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 07/31/2008] [Accepted: 07/31/2008] [Indexed: 11/20/2022]
Abstract
The asymmetric distribution of the nucleotide-bound state of Ran across the nuclear envelope is crucial for determining the directionality of nuclear transport. In the nucleus, Ran is primarily in the guanosine 5'-triphosphate (GTP)-bound state, whereas in the cytoplasm, Ran is primarily guanosine 5'-diphosphate (GDP)-bound. Conformational changes within the Ran switch I and switch II loops are thought to modulate its affinity for importin-beta. Here, we show that RanGDP and importin-beta form a stable complex with a micromolar dissociation constant. This complex can be dissociated by importin-beta binding partners such as importin-alpha. Surprisingly, the crystal structure of the Kap95p-RanGDP complex shows that Kap95p induces the switch I and II regions of RanGDP to adopt a conformation that resembles that of the GTP-bound form. The structure of the complex provides insights into the structural basis for the gradation of affinities regulating nuclear protein transport.
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19
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Sorokin AV, Kim ER, Ovchinnikov LP. Nucleocytoplasmic transport of proteins. BIOCHEMISTRY (MOSCOW) 2008; 72:1439-57. [PMID: 18282135 DOI: 10.1134/s0006297907130032] [Citation(s) in RCA: 168] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In eukaryotic cells, the movement of macromolecules between the nucleus and cytoplasm occurs through the nuclear pore complex (NPC)--a large protein complex spanning the nuclear envelope. The nuclear transport of proteins is usually mediated by a family of transport receptors known as karyopherins. Karyopherins bind to their cargoes via recognition of nuclear localization signal (NLS) for nuclear import or nuclear export signal (NES) for export to form a transport complex. Its transport through NPC is facilitated by transient interactions between the karyopherins and NPC components. The interactions of karyopherins with their cargoes are regulated by GTPase Ran. In the current review, we describe the NPC structure, NLS, and NES, as well as the model of classic Ran-dependent transport, with special emphasis on existing alternative mechanisms; we also propose a classification of the basic mechanisms of protein transport regulation.
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Affiliation(s)
- A V Sorokin
- Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
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20
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Abstract
In eukaryotic cells, segregation of DNA replication and RNA biogenesis in the nucleus and protein synthesis in the cytoplasm poses the requirement of transporting thousands of macromolecules between the two cellular compartments. Transport between nucleus and cytoplasm is mediated by soluble receptors that recognize specific cargoes and carry them through the nuclear pore complex (NPC), the sole gateway between the two compartments at interphase. Nucleocytoplasmic transport is specific not only in terms of cargo recognition, but also in terms of directionality, with nuclear proteins imported into the nucleus and RNAs exported from it. How is directionality achieved? How can the receptors be both specific and versatile in recognizing a multitude of cargoes? And how can their interaction with NPCs allow fast translocation? We describe the molecular mechanisms underlying nucleocytoplasmic transport as they have been revealed by structural studies of the receptors and regulators in different steps of transport cycles.
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Affiliation(s)
- Atlanta Cook
- European Molecular Biology Laboratory, D-69117 Heidelberg, Germany.
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21
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Paradise A, Levin MK, Korza G, Carson JH. Significant proportions of nuclear transport proteins with reduced intracellular mobilities resolved by fluorescence correlation spectroscopy. J Mol Biol 2006; 365:50-65. [PMID: 17056062 PMCID: PMC1831836 DOI: 10.1016/j.jmb.2006.09.089] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2006] [Revised: 09/26/2006] [Accepted: 09/27/2006] [Indexed: 11/20/2022]
Abstract
Nuclear transport requires freely diffusing nuclear transport proteins to facilitate movement of cargo molecules through the nuclear pore. We analyzed dynamic properties of importin alpha, importin beta, Ran and NTF2 in nucleus, cytoplasm and at the nuclear pore of neuroblastoma cells using fluorescence correlation spectroscopy. Mobile components were quantified by global fitting of autocorrelation data from multiple cells. Immobile components were quantified by analysis of photobleaching kinetics. Wild-type Ran was compared to various mutant Ran proteins to identify components representing GTP or GDP forms of Ran. Untreated cells were compared to cells treated with nocodazole or latrunculin to identify components associated with cytoskeletal elements. The results indicate that freely diffusing importin alpha, importin beta, Ran and NTF2 are in dynamic equilibrium with larger pools associated with immobile binding partners such as microtubules in the cytoplasm. These findings suggest that formation of freely diffusing nuclear transport intermediates is in competition with binding to immobile partners. Variation in concentrations of freely diffusing nuclear transport intermediates among cells indicates that the nuclear transport system is sufficiently robust to function over a wide range of conditions.
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Affiliation(s)
- Allison Paradise
- Department of Molecular Microbial and Structural Biology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030, USA
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22
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Lee BJ, Cansizoglu AE, Süel KE, Louis TH, Zhang Z, Chook YM. Rules for nuclear localization sequence recognition by karyopherin beta 2. Cell 2006; 126:543-58. [PMID: 16901787 PMCID: PMC3442361 DOI: 10.1016/j.cell.2006.05.049] [Citation(s) in RCA: 435] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Revised: 03/01/2006] [Accepted: 05/30/2006] [Indexed: 10/24/2022]
Abstract
Karyopherinbeta (Kapbeta) proteins bind nuclear localization and export signals (NLSs and NESs) to mediate nucleocytoplasmic trafficking, a process regulated by Ran GTPase through its nucleotide cycle. Diversity and complexity of signals recognized by Kap betas have prevented prediction of new Kap beta substrates. The structure of Kap beta 2 (also known as Transportin) bound to one of its substrates, the NLS of hnRNP A1, that we report here explains the mechanism of substrate displacement by Ran GTPase. Further analyses reveal three rules for NLS recognition by Kap beta 2: NLSs are structurally disordered in free substrates, have overall basic character, and possess a central hydrophobic or basic motif followed by a C-terminal R/H/KX(2-5)PY consensus sequence. We demonstrate the predictive nature of these rules by identifying NLSs in seven previously known Kap beta 2 substrates and uncovering 81 new candidate substrates, confirming five experimentally. These studies define and validate a new NLS that could not be predicted by primary sequence analysis alone.
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Affiliation(s)
- Brittany J. Lee
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390, USA
| | - Ahmet E. Cansizoglu
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390, USA
| | - Katherine E. Süel
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390, USA
| | - Thomas H. Louis
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390, USA
| | - Zichao Zhang
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390, USA
| | - Yuh Min Chook
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390, USA
- Contact:
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23
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Klucevsek K, Daley J, Darshan MS, Bordeaux J, Moroianu J. Nuclear import strategies of high-risk HPV18 L2 minor capsid protein. Virology 2006; 352:200-8. [PMID: 16733063 DOI: 10.1016/j.virol.2006.04.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Revised: 03/21/2006] [Accepted: 04/06/2006] [Indexed: 11/21/2022]
Abstract
We have investigated the nuclear import strategies of high-risk HPV18 L2 minor capsid protein. HPV18 L2 interacts with Kap alpha2 adapter, and Kap beta2 and Kap beta3 nuclear import receptors. Moreover, binding of RanGTP to either Kap beta2 or Kap beta3 inhibits their interaction with L2, suggesting that these Kap beta/L2 complexes are import competent. Mapping studies show that HPV18 L2 contains two NLSs: in the N-terminus (nNLS) and in the C-terminus (cNLS), both of which can independently mediate nuclear import. Both nNLS and cNLS form a complex with Kap alpha2beta1 heterodimer and mediate nuclear import via a classical pathway. The nNLS is also essential for the interaction of HPV18 L2 with Kap beta2 and Kap beta3. Interestingly, both nNLS and cNLS interact with the viral DNA and this DNA binding occurs without nucleotide sequence specificity. Together, the data suggest that HPV18 L2 can interact via its NLSs with several Kaps and the viral DNA and may enter the nucleus via multiple import pathways mediated by Kap alpha2beta1 heterodimers, Kap beta2 and Kap beta3.
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Affiliation(s)
- K Klucevsek
- Biology Department, Boston College, Higgins Hall, Room 578, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA
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24
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Arnold M, Nath A, Hauber J, Kehlenbach RH. Multiple importins function as nuclear transport receptors for the Rev protein of human immunodeficiency virus type 1. J Biol Chem 2006; 281:20883-20890. [PMID: 16704975 DOI: 10.1074/jbc.m602189200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Rev protein of human immunodeficiency virus type 1 is an RNA-binding protein that is required for nuclear export of unspliced and partially spliced viral mRNAs. Nuclear import of human immunodeficiency virus type 1 Rev has been suggested to depend on the classic nuclear transport receptor importin beta, but not on the adapter protein importin alpha. We now show that, similar to importin alpha, Rev is able to dissociate RanGTP from recycling importin beta, a reaction that leads to the formation of a novel import complex. Besides importin beta, the transport receptors transportin, importin 5, and importin 7 specifically interact with Rev and promote its nuclear import in digitonin-permeabilized cells. A single arginine-rich nuclear localization sequence of Rev is required for interaction with all importins tested so far. In contrast to the importin beta-binding domain of importin alpha, Rev interacts with an N-terminal fragment of importin beta. Transportin contains two independent binding sites for Rev. Hence, the mode of interaction of importin beta and transportin with Rev is clearly distinct from that with their classic import cargoes. Taken together, the viral protein takes advantage of multiple cellular transport pathways for its nuclear accumulation.
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Affiliation(s)
- Marc Arnold
- Universität Heidelberg, Abteilung Virologie, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany; Universität Göttingen, Zentrum für Biochemie und Molekulare Zellbiologie, Humboldtallee 23, 37073 Göttingen, Germany
| | - Annegret Nath
- Universität Göttingen, Zentrum für Biochemie und Molekulare Zellbiologie, Humboldtallee 23, 37073 Göttingen, Germany
| | - Joachim Hauber
- Heinrich Pette Institute for Experimental Virology and Immunology, Martinistrasse 52, 20251 Hamburg, Germany
| | - Ralph H Kehlenbach
- Universität Heidelberg, Abteilung Virologie, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany; Universität Göttingen, Zentrum für Biochemie und Molekulare Zellbiologie, Humboldtallee 23, 37073 Göttingen, Germany.
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25
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Rollenhagen C, Panté N. Nuclear import of spliceosomal snRNPsThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell. Can J Physiol Pharmacol 2006; 84:367-76. [PMID: 16902583 DOI: 10.1139/y05-101] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Uridine-rich small nuclear ribonucleoproteins (U snRNPs) are the building units of the spliceosome. These RNA and protein complexes assemble in the cytoplasm. After proper assembly and RNA maturation, mature U snRNPs are imported into the cell nucleus, where they take part in the splicing process. In this paper we review the current knowledge of how U snRNPs enter the nucleus.
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26
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Caudron M, Bunt G, Bastiaens P, Karsenti E. Spatial coordination of spindle assembly by chromosome-mediated signaling gradients. Science 2005; 309:1373-6. [PMID: 16123300 DOI: 10.1126/science.1115964] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During cell division, chromosomes are distributed to daughter cells by the mitotic spindle. This system requires spatial cues to reproducibly self-organize. We report that such cues are provided by chromosome-mediated interaction gradients between the small guanosine triphosphatase (GTPase) Ran and importin-beta. This produces activity gradients that determine the spatial distribution of microtubule nucleation and stabilization around chromosomes and that are essential for the self-organization of microtubules into a bipolar spindle.
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Affiliation(s)
- Maïwen Caudron
- Cell Biology and Biophysics Department, European Molecular Biology Laboratory (EMBL), EMBL, 69117 Heidelberg, Germany
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27
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Bibak N, Paul RMJ, Freymann DM, Yaseen NR. Purification of RanGDP, RanGTP, and RanGMPPNP by ion exchange chromatography. Anal Biochem 2005; 333:57-64. [PMID: 15351280 DOI: 10.1016/j.ab.2004.06.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Indexed: 11/29/2022]
Abstract
Ran is a small GTPase that cycles between a guanosine diphosphate (GDP)-bound form (RanGDP) and a guanosine triphosphate (GTP)-bound form (RanGTP) and plays important roles in nuclear transport and mitosis. For studies of Ran function and its interactions with partner proteins, pure RanGDP and RanGTP complexes are critical. Ran complexed with the nonhydrolyzable GTP analog, GMPPNP (RanGMPPNP), is used instead of RanGTP when inhibition of hydrolysis is required. In this study, we demonstrate that the binding of Ran to a UNO Q ion exchange column is remarkably sensitive to small shifts in MgCl(2) concentration, and we use this property to purify recombinant RanGTP, RanGMPPNP, and RanGDP complexes. At 10 mM MgCl(2), Ran was found predominantly in the flow-through and, thus, was separated from the vast majority of bacterial proteins. After reducing the concentration of MgCl(2) to 5 mM, further purification of RanGTP, RanGMPPNP, and RanGDP was achieved by loading onto ion exchange columns and elution with an NaCl gradient. Purity of the resulting preparations was confirmed by releasing the bound nucleotide and checking it against a known nucleotide by high-performance liquid chromatography (HPLC). To further confirm the purity and function of the Ran preparations, appropriate protein-binding, enzymatic, and nuclear import assays were carried out. These methods should facilitate studies of cellular processes involving Ran by providing pure functional Ran-nucleotide complexes.
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Affiliation(s)
- Niloufar Bibak
- Department of Pathology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Chicago, IL 60611, USA
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28
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Fay A, Yutzy WH, Roden RBS, Moroianu J. The positively charged termini of L2 minor capsid protein required for bovine papillomavirus infection function separately in nuclear import and DNA binding. J Virol 2004; 78:13447-54. [PMID: 15564455 PMCID: PMC533947 DOI: 10.1128/jvi.78.24.13447-13454.2004] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Accepted: 07/29/2004] [Indexed: 11/20/2022] Open
Abstract
During the papillomavirus (PV) life cycle, the L2 minor capsid protein enters the nucleus twice: in the initial phase after entry of virions into cells and in the productive phase to mediate encapsidation of the newly replicated viral genome. Therefore, we investigated the interactions of the L2 protein of bovine PV type 1 (BPV1) with the nuclear import machinery and the viral DNA. We found that BPV1 L2 bound to the karyopherin alpha2 (Kap alpha2) adapter and formed a complex with Kap alpha2beta1 heterodimers. Previous data have shown that the positively charged termini of BPV1 L2 are required for BPV1 infection after the binding of the virions to the cell surface. We determined that these BPV1 L2 termini function as nuclear localization signals (NLSs). Both the N-terminal NLS (nNLS) and the C-terminal NLS (cNLS) interacted with Kap alpha2, formed a complex with Kap alpha2beta1 heterodimers, and mediated nuclear import via a Kap alpha2beta1 pathway. Interestingly, the cNLS was also the major DNA binding site of BPV1 L2. Consistent with the promiscuous DNA encapsidation by BPV1 pseudovirions, this DNA binding occurred without nucleotide sequence specificity. Moreover, an L2 mutant encoding a scrambled version of the cNLS, which supports production of virions, rescued the DNA binding but not the Kap alpha2 interaction. These data support a model in which BPV1 L2 functions as an adapter between the viral DNA via the cNLS and the Kaps via the nNLS and facilitates nuclear import of the DNA during infection.
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Affiliation(s)
- Alyson Fay
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA
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29
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Darshan MS, Lucchi J, Harding E, Moroianu J. The l2 minor capsid protein of human papillomavirus type 16 interacts with a network of nuclear import receptors. J Virol 2004; 78:12179-88. [PMID: 15507604 PMCID: PMC525100 DOI: 10.1128/jvi.78.22.12179-12188.2004] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The L2 minor capsid proteins enter the nucleus twice during viral infection: in the initial phase after virion disassembly and in the productive phase when, together with the L1 major capsid proteins, they assemble the replicated viral DNA into virions. In this study we investigated the interactions between the L2 protein of high-risk human papillomavirus type 16 (HPV16) and nuclear import receptors. We discovered that HPV16 L2 interacts directly with both Kapbeta(2) and Kapbeta(3). Moreover, binding of Ran-GTP to either Kapbeta(2) or Kapbeta(3) inhibits its interaction with L2, suggesting that the Kapbeta/L2 complex is import competent. In addition, we found that L2 forms a complex with the Kapalpha(2)beta(1) heterodimer via interaction with the Kapalpha(2) adapter. In agreement with the binding data, nuclear import of L2 in digitonin-permeabilized cells could be mediated by either Kapalpha(2)beta(1) heterodimers, Kapbeta(2), or Kapbeta(3). Mapping studies revealed that HPV16 L2 contains two nuclear localization signals (NLSs), in the N terminus (nNLS) and C terminus (cNLS), that could mediate its nuclear import. Together the data suggest that HPV16 L2 interacts via its NLSs with a network of karyopherins and can enter the nucleus via several import pathways mediated by Kapalpha(2)beta(1) heterodimers, Kapbeta(2), and Kapbeta(3).
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Affiliation(s)
- Medha S Darshan
- Biology Department, Boston College, Higgins Hall Room 578, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA
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30
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Ploski JE, Shamsher MK, Radu A. Paired-type homeodomain transcription factors are imported into the nucleus by karyopherin 13. Mol Cell Biol 2004; 24:4824-34. [PMID: 15143176 PMCID: PMC416398 DOI: 10.1128/mcb.24.11.4824-4834.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We report that the paired homeodomain transcription factor Pax6 is imported into the nucleus by the Karyopherin beta family member Karyopherin 13 (Kap13). Pax6 was identified as a potential cargo for Kap13 by a yeast two-hybrid screen. Direct binding of Pax6 to Kap13 was subsequently confirmed by in vitro assays with recombinant proteins, and binding in vivo was shown by coimmunoprecipitation. Ran-dependent import of Pax6 by Kap13 was shown to occur by using a digitonin-permeabilized cells assay. Kap13 binds to Pax6 via a nuclear localization sequence (NLS), which is located within a segment of 80 amino acid residues that includes the homeodomain. Kap13 showed reduced binding to Pax6 when either region located at each end of the homeodomain (208 to 214 and 261 to 267) was deleted. The paired-type homeodomain transcription factor family includes more than 20 members. All members contain a region similar to the NLS found in Pax6 and are therefore likely to be imported by Kap13. We confirmed this hypothesis for Pax3 and Crx, which bind to and are imported by Kap13.
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Affiliation(s)
- Jonathan E Ploski
- The Carl C. Icahn Center for Gene Therapy and Molecular Medicine, Box 1496, The Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA.
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Angeline M, Merle E, Moroianu J. The E7 oncoprotein of high-risk human papillomavirus type 16 enters the nucleus via a nonclassical Ran-dependent pathway. Virology 2004; 317:13-23. [PMID: 14675621 DOI: 10.1016/j.virol.2003.08.024] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
E7, the major transforming protein of high-risk human papillomavirus (HPV), type 16, binds and inactivates the retinoblastoma protein (pRb), and the Rb-related proteins p107 and p130. HPV16 E7 is a nuclear protein lacking a classical basic nuclear localization signal. In this study we investigated the nuclear import of HPV16 E7 oncoprotein in digitonin-permeabilized HeLa cells. HPV16 E7 nuclear import was independent of pRb, as an E7(DeltaDLYC) variant defective in pRb binding was imported into the nuclei of digitonin-permeabilized cells as efficiently as wild-type E7 in the presence of exogenous cytosol. Interestingly, we discovered that HPV16 E7 is imported into the nuclei via a novel pathway different from those mediated by Kap alpha2beta1 heterodimers, Kap beta1, or Kap beta2. Nuclear accumulation of E7 required Ran and was not inhibited by the RanG19V-GTP variant, an inhibitor of Kap beta mediated import pathways. Together the data suggest that HPV16 E7 translocates through the nuclear pores via a nonclassical Ran-dependent pathway, independent of the main cytosolic Kap beta import receptors.
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Affiliation(s)
- Michael Angeline
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA
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32
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Oeffinger M, Dlakic M, Tollervey D. A pre-ribosome-associated HEAT-repeat protein is required for export of both ribosomal subunits. Genes Dev 2004; 18:196-209. [PMID: 14729571 PMCID: PMC324425 DOI: 10.1101/gad.285604] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Accepted: 12/02/2003] [Indexed: 11/24/2022]
Abstract
Rrp12p (Ypl012w) is unusual among characterized ribosome synthesis factors in being associated with late precursors to both the 40S and 60S subunits. Rrp12p is predominantly nuclear with nucleolar enrichment at steady state, but shuttled between the nucleus and cytoplasm in a heterokaryon assay. Strains depleted of Rrp12p are impaired in the nuclear export of both ribosomal subunits. Sequence analysis combined with fold recognition and modeling showed that Rrp12p is a member of a family of pre-ribosome-associated HEAT-repeat proteins. Like other HEAT-repeat transport factors, Rrp12p binds in vitro to nucleoporin FG-repeats of both the GLFG and FXFG families and to the GTPase Gsp1p (yeast RAN). Rrp12p also showed robust in vitro binding to a pre-rRNA transcript, in addition to poly(A) and poly(U). We propose that Rrp12p binds to the RNA components of the pre-ribosomes and promotes export of both subunits via its interactions with the nucleoporins and Gsp1p.
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Affiliation(s)
- Marlene Oeffinger
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
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33
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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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34
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Legate KR, Andrews DW. The beta-subunit of the signal recognition particle receptor is a novel GTP-binding protein without intrinsic GTPase activity. J Biol Chem 2003; 278:27712-20. [PMID: 12759365 DOI: 10.1074/jbc.m302158200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The beta-subunit of the signal recognition particle receptor (SRbeta), a member of the Ras family of small molecular weight GTPases, is involved in the targeting of nascent polypeptide chains to the protein translocation machinery in the endoplasmic reticulum membrane. We purified SRbeta from an expressing strain of Escherichia coli and investigated the properties of the isolated GTPase. We find that, unlike other Ras family GTPases, most SRbeta purifies bound to GTP, and SRbeta-bound GTP is not easily exchanged with solution GTP. SRbeta possesses no detectable GTPase activity. Although a stable interaction between SRbeta and ribosomes is observed, SRbeta is not stimulated to hydrolyze GTP when incubated with ribosomes or ribosome-nascent chains. A GTPase mutant harboring a mutation in a region predicted to be functionally important, based on observations made in related GTPases, binds GTP with faster kinetics and appears to be a less stable protein but otherwise displays similar properties to the wild-type SRbeta GTPase. Our results demonstrate that as an isolated GTPase, SRbeta functions differently from the Arf- and Ras-type GTPases that it is most closely related to by sequence.
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MESH Headings
- Animals
- Chromatography, High Pressure Liquid
- Cross-Linking Reagents/pharmacology
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Endoplasmic Reticulum/metabolism
- Escherichia coli/metabolism
- GTP Phosphohydrolases/metabolism
- GTP-Binding Proteins/metabolism
- Guanosine Triphosphate/metabolism
- Humans
- Hydrolysis
- Intracellular Membranes/metabolism
- Kinetics
- Mutagenesis, Site-Directed
- Mutation
- Plasmids/metabolism
- Precipitin Tests
- Protein Binding
- Protein Structure, Tertiary
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/physiology
- Receptors, Peptide/chemistry
- Receptors, Peptide/physiology
- Ribosomes/metabolism
- Saccharomyces cerevisiae/metabolism
- Spectrometry, Fluorescence
- Time Factors
- Ultraviolet Rays
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Affiliation(s)
- Kyle R Legate
- Department of Biochemistry, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
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35
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Thomas F, Kutay U. Biogenesis and nuclear export of ribosomal subunits in higher eukaryotes depend on the CRM1 export pathway. J Cell Sci 2003; 116:2409-19. [PMID: 12724356 DOI: 10.1242/jcs.00464] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The production of ribosomes constitutes a major biosynthetic task for cells. Eukaryotic small and large ribosomal subunits are assembled in the nucleolus and independently exported to the cytoplasm. Most nuclear export pathways require RanGTP-binding export receptors. We analyzed the role of CRM1, the export receptor for leucine-rich nuclear export signals (NES), in the biogenesis of ribosomal subunits in vertebrate cells. Inhibition of the CRM1 export pathway led to a defect in nuclear export of both 40S and 60S subunits in HeLa cells. Moreover, the export of newly made ribosomal subunits in Xenopus oocytes was efficiently and specifically competed by BSA-NES conjugates. The CRM1 dependence of 60S subunit export suggested a conserved function for NMD3, a factor proposed to be a 60S subunit export adaptor in yeast. Indeed, we observed that nuclear export of human NMD3 (hNMD3) is sensitive to leptomycin B (LMB), which inactivates CRM1. It had, however, not yet been demonstrated that Nmd3 can interact with CRM1. Using purified recombinant proteins we have shown here that hNMD3 binds to CRM1 directly, in a RanGTP-dependent manner, by way of a C-terminal NES sequence. Our results suggest that the functions of CRM1 and NMD3 in ribosomal subunit export are conserved from yeast to higher eukaryotes.
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Affiliation(s)
- Franziska Thomas
- Swiss Federal Institute of Technology (ETH) Zürich, Institute of Biochemistry, HPM F11.1, Switzerland
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36
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Nelson LM, Rose RC, Moroianu J. The L1 major capsid protein of human papillomavirus type 11 interacts with Kap beta2 and Kap beta3 nuclear import receptors. Virology 2003; 306:162-9. [PMID: 12620808 DOI: 10.1016/s0042-6822(02)00025-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We have previously shown that the L1 major capsid protein of low-risk HPV11 binds to the Kap alpha2 adapter and enters the nucleus via a Kap alpha2beta1-mediated pathway. In this study, we discovered that HPV11 L1 capsomeres bind to Kap beta2 import receptor, known to mediate nuclear import of hnRNP A1 via interaction with its nuclear localization signal termed M9. Significantly, binding of HPV11 L1 capsomeres to Kap beta2 inhibited the nuclear import of Kap beta2, and its specific M9-containing cargo. Interestingly, HPV11 L1 capsomeres also interacted with Kap beta3 import receptor and inhibited Kap beta3 nuclear import. Moreover, the L1 capsomeres of high-risk HPV-16 shared these activities. These data suggest that HPV L1 major capsid proteins interact with Kap beta2 and Kap beta3, and they may inhibit the Kap beta2- and Kap beta3-mediated nuclear import pathways during the productive phase of the viral life cycle when the virions are assembled and released.
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Affiliation(s)
- Lisa M Nelson
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA
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37
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Le Roux LG, Moroianu J. Nuclear entry of high-risk human papillomavirus type 16 E6 oncoprotein occurs via several pathways. J Virol 2003; 77:2330-7. [PMID: 12551970 PMCID: PMC141087 DOI: 10.1128/jvi.77.4.2330-2337.2003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The E6 oncoprotein of high-risk human papillomavirus type 16 (HPV16) interacts with several nuclear transcription factors and coactivators in addition to cytoplasmic proteins, suggesting that nuclear import of HPV16 E6 plays a role in the cellular transformation process. In this study we have investigated the nuclear import pathways of HPV16 E6 in digitonin-permeabilized HeLa cells. We found that HPV16 E6 interacted with the karyopherin (Kap) alpha2 adapter and could enter the nucleus via a classical Kap alpha2beta1-mediated pathway. Interestingly, HPV16 E6 also interacted, via its basic nuclear localization signal (NLS) located at the C terminus, with both Kap beta1 and Kap beta2 import receptors. Binding of RanGTP to these Kap betas inhibited their interaction with HPV16 E6 NLS. In agreement with these binding data, nuclear import of the HPV16 E6 oncoprotein in digitonin-permeabilized HeLa cells could be mediated by either Kap beta1 or Kap beta2. Nuclear import via these pathways required RanGDP and was independent of GTP hydrolysis by Ran. Significantly, an E6(R124G) mutant had reduced nuclear import activity, and the E6 deletion mutant lacking (121)KKQR(124) was not imported into the nucleus. The data reveal that the HPV16 E6 oncoprotein interacts via its C-terminal NLS with several karyopherins and exploits these interactions to enter the nucleus of host cells via multiple pathways.
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Affiliation(s)
- Lucia G Le Roux
- Biology Department, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467-3811, USA
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38
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Jacques KM, Nie Z, Stauffer S, Hirsch DS, Chen LX, Stanley KT, Randazzo PA. Arf1 dissociates from the clathrin adaptor GGA prior to being inactivated by Arf GTPase-activating proteins. J Biol Chem 2002; 277:47235-41. [PMID: 12376537 DOI: 10.1074/jbc.m208875200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effectors of monomeric GTP-binding proteins can influence interactions with GTPase-activating proteins (GAPs) in two ways. In one case, effector and GAP binding to the GTP-binding protein is mutually exclusive. In another case, the GTP-binding protein bound to an effector is the substrate for the GTPase-activating protein. Here predictions for these two mechanisms were tested for the Arf1 effector GGA and ASAP family Arf GAPs. GGA inhibited Arf GAP activity of ASAP1, AGAP1, ARAP1, and Arf GAP1 and inhibited binding of Arf1.GTPgammaS to AGAP1 with K(i) values correlating with the K(d) for the GGA.Arf1 complex. ASAP1 blocked Arf1.GTPgammaS binding to GGA with a K(i) similar to the K(d) for the ASAP.Arf1.GTPgammaS complex. No interaction of GGA with ASAP1 was detected. Consistent with GGA sequestering Arf from GAPs, overexpression of GGA slowed the rate of Arf dissociation from the Golgi apparatus following treatment with brefeldin A. Mutational analysis revealed the amino-terminal alpha-helix and switch I of Arf1 contributed to interaction with both GGA and GAPs. These data exclude the mechanism previously documented for Arf GAP1/coatomer in which Arf1 is inactivated in a tripartite complex. Instead, termination of Arf1 signals mediated through GGA require that Arf1.GTP dissociates from GGA prior to interaction with GAP and consequent hydrolysis of GTP.
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Affiliation(s)
- Kerry M Jacques
- Laboratory of Cellular Oncology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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39
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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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40
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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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41
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42
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Lyman SK, Guan T, Bednenko J, Wodrich H, Gerace L. Influence of cargo size on Ran and energy requirements for nuclear protein import. J Cell Biol 2002; 159:55-67. [PMID: 12370244 PMCID: PMC2173498 DOI: 10.1083/jcb.200204163] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Previous work has shown that the transport of some small protein cargoes through the nuclear pore complex (NPC) can occur in vitro in the absence of nucleoside triphosphate hydrolysis. We now demonstrate that in the importin alpha/beta and transportin import pathways, efficient in vitro transport of large proteins, in contrast to smaller proteins, requires hydrolyzable GTP and the small GTPase Ran. Morphological and biochemical analysis indicates that the presence of Ran and GTP allows large cargo to efficiently cross central regions of the NPC. We further demonstrate that this function of RanGTP at least partly involves its direct binding to importin beta and transportin. We suggest that RanGTP functions in these pathways to promote the transport of large cargo by enhancing the ability of import complexes to traverse diffusionally restricted areas of the NPC.
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Affiliation(s)
- Susan K Lyman
- Departments of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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43
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Nelson LM, Rose RC, Moroianu J. Nuclear import strategies of high risk HPV16 L1 major capsid protein. J Biol Chem 2002; 277:23958-64. [PMID: 11971900 DOI: 10.1074/jbc.m200724200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During the late phase of human papillomavirus (HPV) infection, the L1 major capsid proteins enter the nuclei of host epithelial cells and, together with the L2 minor capsid proteins, assemble the replicated viral DNA into virions. We investigated the nuclear import of the L1 major capsid protein of high risk HPV16. When digitonin-permeabilized HeLa cells were incubated with HPV16 L1 capsomeres, the L1 protein was imported into the nucleus in a receptor-mediated manner. HPV16 L1 capsomeres formed complexes with Kap alpha2beta1 heterodimers via interaction with Kap alpha2. Accordingly, nuclear import of HPV16 L1 capsomeres was mediated by Kap alpha2beta1 heterodimers, required RanGDP and free GTP, and was independent of GTP hydrolysis. Remarkably, HPV16 L1 capsomeres also interacted with Kap beta2 and binding of RanGTP to Kap beta2 did not dissociate the HPV16 L1.Kap beta2 complex. Significantly, HPV16 L1 capsomeres inhibited the nuclear import of Kap beta2 and of a Kap beta2-specific M9-containing cargo. These data suggest that, during the productive stage of infection, while the HPV16 L1 major capsid protein enters the nucleus via the Kap alpha2beta1-mediated pathway to assemble the virions, it also inhibits the Kap beta2-mediated nuclear import of host hnRNP A1 protein and, in this way, favors virion formation.
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Affiliation(s)
- Lisa M Nelson
- Biology Department, Boston College, Chestnut Hill, Massachusetts 02467, USA
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44
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Chook YM, Jung A, Rosen MK, Blobel G. Uncoupling Kapbeta2 substrate dissociation and ran binding. Biochemistry 2002; 41:6955-66. [PMID: 12033928 DOI: 10.1021/bi012122p] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Karyopherinbeta2 (Kapbeta2) imports a variety of mRNA binding proteins into the nucleus. Release of import substrates in the nucleus involves formation of a high-affinity Kapbeta2-RanGTP complex and concomitant dissociation of import substrates. The crystal structure of the Kapbeta2-RanGppNHp complex shows that Ran binds in the Kapbeta2 N-terminal arch and substrate most likely binds its C-terminal arch. The structure suggested a mechanism for Ran-mediated substrate dissociation where a long internal acidic loop in Kapbeta2 transmits structural information between the GTPase and substrate sites, leading to displacement of substrate by the loop when Ran is bound. To study the molecular mechanism of substrate dissociation, we have cleaved the acidic loop of Kapbeta2 proteolytically (cl-Kapbeta2) and also constructed a mutant of Kapbeta2 with a truncated loop (TL-Kapbeta2). Both modified Kapbeta2s are unable to undergo Ran-mediated substrate dissociation. We have also mapped the boundaries of the Kapbeta2 binding site of substrate mRNA binding protein A1 using a widely applicable method employing NMR spectroscopy. This has allowed design of reagents to quantitate the affinities of the Kapbeta2 proteins for Ran and substrate. cl-Kapbeta2, TL-Kapbeta2, and native Kapbeta2 have comparable affinities for both RanGppNHp and import substrates, indicating that perturbation of the loop has not altered the strength of binary Kapbeta2-Ran or Kapbeta2-substrate interactions. The TL-Kapbeta2 mutant also binds RanGppNHp and substrate simultaneously to form a ternary complex, indicating that in addition to the loss of coupling between Ran binding and substrate dissociation, the two ligand sites on Kapbeta2 are spatially distinct. The uncoupling of Ran binding and substrate dissociation in the TL-Kapbeta2 mutant is further evident in significant loss of Ran-mediated nuclear uptake of fluorescent substrate in digitonin-permeabilized HeLa cells. These results support our previously proposed GTPase-mediated Kapbeta2-substrate dissociation mechanism where the acidic loop of Kapbeta2 physically couples distinct Ran and substrate binding sites.
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Affiliation(s)
- Yuh Min Chook
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
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45
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Affiliation(s)
- F Ralf Bischoff
- Division for Molecular Biology of Mitosis, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
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46
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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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47
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Yoshida K, Blobel G. The karyopherin Kap142p/Msn5p mediates nuclear import and nuclear export of different cargo proteins. J Cell Biol 2001; 152:729-40. [PMID: 11266464 PMCID: PMC2195777 DOI: 10.1083/jcb.152.4.729] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have identified a novel pathway for protein import into the nucleus. Although the product of Saccharomyces cerevisiae gene MSN5 was previously shown to function as a karyopherin (Kap) for nuclear export of various proteins, we discovered a nuclear import pathway mediated by Msn5p (also referred to as Kap142p). We have purified from yeast cytosol a complex containing Kap142p and the trimeric replication protein A (RPA), which is required for multiple aspects of DNA metabolism, including DNA replication, DNA repair, and recombination. In wild-type cells, RPA was localized primarily to the nucleus but, in a KAP142 deletion strain, RPA was mislocalized to the cytoplasm and the strain was highly sensitive to bleomycin (BLM). BLM causes DNA double-strand breaks and, in S. cerevisiae, the DNA damage is repaired predominantly by RPA-dependent homologous recombination. Therefore, our results indicate that in wild-type cells a critical portion of RPA was imported into the nucleus by Kap142p. Like several other import-related Kap-substrate complexes, the endogenous RPA-Kap142p complex was dissociated by RanGTP, but not by RanGDP. All three RPA genes are essential for viability, whereas KAP142 is not. Perhaps explaining this disparity, we observed an interaction between RPA and Kap95p in a strain lacking Kap142p. This interaction could provide a mechanism for import of RPA into the nucleus and cell viability in the absence of Kap142p. Together with published results (Kaffman, A., N.M. Rank, E.M. O'Neill, L.S. Huang, and E.K. O'Shea. 1998. Nature. 396:482-486; Blondel, M., P.M. Alepuz, L.S. Huang, S. Shaham, G. Ammerer, and M. Peter. 1999. Genes Dev. 13:2284-2300; DeVit, M.J., and M. Johnston. 1999. Curr. Biol. 9:1231-1241; Mahanty, S.K., Y. Wang, F.W. Farley, and E.A. Elion. 1999. Cell. 98:501-512) our data indicate that the karyopherin Kap142p is able to mediate nuclear import of one set of proteins and nuclear export of a different set of proteins.
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Affiliation(s)
- Kimihisa Yoshida
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10021
| | - Günter Blobel
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10021
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48
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Wen Y, Shatkin AJ. Cap methyltransferase selective binding and methylation of GpppG-RNA are stimulated by importin-alpha. Genes Dev 2000; 14:2944-9. [PMID: 11114884 PMCID: PMC317093 DOI: 10.1101/gad.848200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2000] [Accepted: 10/24/2000] [Indexed: 11/24/2022]
Abstract
We screened a human cDNA library for proteins that bind mRNA cap methyltransferase (MT) and isolated nuclear transporter importin-alpha (Impalpha). This direct association was confirmed by glutathione S-transferase (GST) pulldown, coimmunoprecipitation, and nuclear colocalization. In gel shift assays, MT selectively bound RNA containing 5'-terminal GpppG, and binding was inhibited by GpppG and not by m(7)GpppC. Impalpha markedly enhanced MT binding to GpppG-RNA and stimulated MT activity. MT/RNA/Impalpha complexes were dissociated by importin-beta, which also blocked the stimulation of cap methylation by Impalpha. The presence of RanGTP but not RanGDP prevented these effects of importin-beta. These findings indicate that importins play a novel role in mRNA biogenesis at the level of cap methylation.
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Affiliation(s)
- Y Wen
- Center for Advanced Biotechnology and Medicine, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
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49
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Fontoura BM, Blobel G, Yaseen NR. The nucleoporin Nup98 is a site for GDP/GTP exchange on ran and termination of karyopherin beta 2-mediated nuclear import. J Biol Chem 2000; 275:31289-96. [PMID: 10875935 DOI: 10.1074/jbc.m004651200] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Karyopherin beta2 (Kapbeta2, transportin) binds the M9 sequence of human ribonucleoprotein A1 and mediates its nuclear import. Here we show a role for the nucleoporin Nup98 in the disassembly of Kapbeta2 import complexes at the nuclear side of the nuclear pore complex (NPC). Kapbeta2 bound to a region at the N terminus of Nup98 that contains an M9-like sequence. The human ribonucleoprotein A1 M9 sequence competed with Nup98 for binding to Kapbeta2, indicating that Nup98 can dissociate Kapbeta2 from its substrate. Binding of Kapbeta2 to Nup98 was inhibited by Ran loaded with guanylyl imidophosphate, suggesting that RanGTP dissociates Kapbeta2 from Nup98. RanGTP is produced from RanGDP through nucleotide exchange mediated by RanGEF (RCC1). Immunoelectron microscopy and nucleotide exchange assays revealed functional RanGEF on both sides of the NPC. On the nuclear side, the localization of RanGEF coincided with that of Nup98. RanGEF bound to Nup98 at a region adjacent to the Kapbeta2-binding site. These findings suggest a model where 1) import substrate is released from Kapbeta2 at the nucleoplasmic side of the NPC by competition with the Nup98 M9-like site, 2) Nup98-bound RanGEF catalyzes the formation of RanGTP, and 3) RanGTP dissociates Kapbeta2 from Nup98 allowing repeated cycles of import.
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Affiliation(s)
- B M Fontoura
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10021, USA
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50
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Villa Braslavsky CI, Nowak C, Görlich D, Wittinghofer A, Kuhlmann J. Different structural and kinetic requirements for the interaction of Ran with the Ran-binding domains from RanBP2 and importin-beta. Biochemistry 2000; 39:11629-39. [PMID: 10995230 DOI: 10.1021/bi001010f] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cytoplasmic disassembly of Ran.GTP.importin and Ran.GTP.exportin. cargo complexes is an essential step in the corresponding nuclear import and export cycles. It has previously been shown that such disassembly can be mediated by RanBP1 in the presence of RanGAP. The nuclear pore complex protein RanBP2 (Nup358) contains four Ran-binding domains (RanBDi) that might function like RanBP1. We used biophysical assays based on fluorescence-labeled probes and on surface plasmon resonance to investigate the dynamic interplay of Ran in its GDP- and GTP-complexed states with RanBDis and with importin-beta. We show that RanBP1 and the four RanBDis from RanBP2 have comparable affinities for Ran.GTP (10(8)-10(9) M(-1)). Deletion of Ran's C-terminal (211)DEDDDL(216) sequence weakens the interaction of Ran.GTP with RanBPis approximately 2000-fold, but accelerates the association of Ran.GTP with importin-beta 10-fold. Importin-beta binds Ran.GTP with a moderate rate, but attains a high affinity for Ran (K(D) = 140 pM) via an extremely low dissociation rate of 10(-5) s(-)(1). Association with Ran is accelerated 3-fold in the presence of RanBP1, which presumably prevents steric hindrance caused by the Ran C-terminus. In addition, we show that the RanBDis of RanBP2 are full equivalents of RanBP1 in that they also costimulate RanGAP-catalyzed GTP hydrolysis in Ran and relieve the GTPase block in a Ran.GTP.transportin complex. Our data suggest that the C-terminus of Ran functions like a loose tether in Ran.GTP complexes of importins or exportins that exit the nucleus. This flag is then recognized by the multiple RanBDis at or near the nuclear pore complex, allowing efficient disassembly of these Ran.GTP complexes.
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Affiliation(s)
- C I Villa Braslavsky
- Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany
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