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Naoumkina M, Thyssen GN, Fang DD, Florane CB, Li P. A deletion/duplication in the Ligon lintless-2 locus induces siRNAs that inhibit cotton fiber cell elongation. PLANT PHYSIOLOGY 2022; 190:1792-1805. [PMID: 35997586 PMCID: PMC9614481 DOI: 10.1093/plphys/kiac384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 07/22/2022] [Indexed: 06/15/2023]
Abstract
Most cultivated cotton (Gossypium hirsutum L.) varieties have two types of seed fibers: short fuzz fiber strongly adhered to the seed coat, and long lint fiber used in the textile industry. The Ligon lintless-2 (Li2) cotton mutant has a normal vegetative phenotype but produces very short lint fiber on the seeds. The Li2 mutation is controlled by a single dominant gene. We discovered a large structural rearrangement at the end of chromosome D13 in the Li2 mutant based on whole-genome sequencing and genetic mapping of segregating populations. The rearrangement contains a 177-kb deletion and a 221-kb duplication positioned as a tandem inverted repeat. The gene Gh_D13G2437 is located at the junction of the inverted repeat in the duplicated region. During transcription such structure spontaneously forms self-complementary hairpin RNA of Gh_D13G2437 followed by production of small interfering RNA (siRNA). Gh_D13G2437 encodes a Ran-Binding Protein 1 (RanBP1) that preferentially expresses during cotton fiber elongation. The abundance of siRNA produced from Gh_D13G2437 reciprocally corresponds with the abundance of highly homologous (68%-98% amino acid sequence identity) RanBP1 family transcripts during fiber elongation, resulting in a shorter fiber phenotype in the Li2. Overexpression of Gh_D13G2437 in the Li2 mutant recovered the long lint fiber phenotype. Taken together, our findings revealed that siRNA-induced silencing of a family of RanBP1s inhibit elongation of cotton fiber cells in the Li2 mutant.
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Affiliation(s)
- Marina Naoumkina
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
| | - Gregory N Thyssen
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
- Cotton Chemistry and Utilization Research Unit, USDA-ARS-SRRC, New Orleans, Louisiana 70124, USA
| | - David D Fang
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
| | - Christopher B Florane
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
| | - Ping Li
- Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), New Orleans, Louisiana 70124, USA
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Hamed M, Caspar B, Port SA, Kehlenbach RH. A nuclear export sequence promotes CRM1-dependent targeting of the nucleoporin Nup214 to the nuclear pore complex. J Cell Sci 2021; 134:jcs.258095. [PMID: 33589493 DOI: 10.1242/jcs.258095] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 02/02/2021] [Indexed: 11/20/2022] Open
Abstract
Nup214 is a major nucleoporin on the cytoplasmic side of the nuclear pore complex with roles in late steps of nuclear protein and mRNA export. It interacts with the nuclear export receptor CRM1 (also known as XPO1) via characteristic phenylalanine-glycine (FG) repeats in its C-terminal region. Here, we identify a classic nuclear export sequence (NES) in Nup214 that mediates Ran-dependent binding to CRM1. Nup214 versions with mutations in the NES, as well as wild-type Nup214 in the presence of the selective CRM1 inhibitor leptomycin B, accumulate in the nucleus of Nup214-overexpressing cells. Furthermore, physiological binding partners of Nup214, such as Nup62 and Nup88, are recruited to the nucleus together with Nup214. Nuclear export of mutant Nup214 can be rescued by artificial nuclear export sequences at the C-terminal end of Nup214, leading also to a correct localization of Nup88. Our results suggest a function of the Nup214 NES in the biogenesis of the nuclear pore complex and/or in terminal steps of CRM1-dependent protein export.
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Affiliation(s)
- Mohamed Hamed
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Birgit Caspar
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Sarah A Port
- Department of Molecular Biology, Faculty of Medicine, GZMB, Georg-August-University Göttingen, Humboldtallee 23, 37073 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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Motahari Z, Moody SA, Maynard TM, LaMantia AS. In the line-up: deleted genes associated with DiGeorge/22q11.2 deletion syndrome: are they all suspects? J Neurodev Disord 2019; 11:7. [PMID: 31174463 PMCID: PMC6554986 DOI: 10.1186/s11689-019-9267-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 04/21/2019] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND 22q11.2 deletion syndrome (22q11DS), a copy number variation (CNV) disorder, occurs in approximately 1:4000 live births due to a heterozygous microdeletion at position 11.2 (proximal) on the q arm of human chromosome 22 (hChr22) (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011). This disorder was known as DiGeorge syndrome, Velo-cardio-facial syndrome (VCFS) or conotruncal anomaly face syndrome (CTAF) based upon diagnostic cardiovascular, pharyngeal, and craniofacial anomalies (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011; Burn et al., J Med Genet 30:822-4, 1993) before this phenotypic spectrum was associated with 22q11.2 CNVs. Subsequently, 22q11.2 deletion emerged as a major genomic lesion associated with vulnerability for several clinically defined behavioral deficits common to a number of neurodevelopmental disorders (Fernandez et al., Principles of Developmental Genetics, 2015; Robin and Shprintzen, J Pediatr 147:90-6, 2005; Schneider et al., Am J Psychiatry 171:627-39, 2014). RESULTS The mechanistic relationships between heterozygously deleted 22q11.2 genes and 22q11DS phenotypes are still unknown. We assembled a comprehensive "line-up" of the 36 protein coding loci in the 1.5 Mb minimal critical deleted region on hChr22q11.2, plus 20 protein coding loci in the distal 1.5 Mb that defines the 3 Mb typical 22q11DS deletion. We categorized candidates based upon apparent primary cell biological functions. We analyzed 41 of these genes that encode known proteins to determine whether haploinsufficiency of any single 22q11.2 gene-a one gene to one phenotype correspondence due to heterozygous deletion restricted to that locus-versus complex multigenic interactions can account for single or multiple 22q11DS phenotypes. CONCLUSIONS Our 22q11.2 functional genomic assessment does not support current theories of single gene haploinsufficiency for one or all 22q11DS phenotypes. Shared molecular functions, convergence on fundamental cell biological processes, and related consequences of individual 22q11.2 genes point to a matrix of multigenic interactions due to diminished 22q11.2 gene dosage. These interactions target fundamental cellular mechanisms essential for development, maturation, or homeostasis at subsets of 22q11DS phenotypic sites.
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Affiliation(s)
- Zahra Motahari
- The Institute for Neuroscience, and Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington DC, 20037 USA
| | - Sally Ann Moody
- The Institute for Neuroscience, and Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington DC, 20037 USA
| | - Thomas Michael Maynard
- The Institute for Neuroscience, and Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington DC, 20037 USA
| | - Anthony-Samuel LaMantia
- The Institute for Neuroscience, and Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, Washington DC, 20037 USA
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Moore KS, Yagci N, van Alphen F, Meijer AB, ‘t Hoen PAC, von Lindern M. Strap associates with Csde1 and affects expression of select Csde1-bound transcripts. PLoS One 2018; 13:e0201690. [PMID: 30138317 PMCID: PMC6107111 DOI: 10.1371/journal.pone.0201690] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 07/22/2018] [Indexed: 02/06/2023] Open
Abstract
Erythropoiesis is regulated at many levels, including control of mRNA translation. Changing environmental conditions, such as hypoxia or the availability of nutrients and growth factors, require a rapid response enacted by the enhanced or repressed translation of existing transcripts. Cold shock domain protein e1 (Csde1/Unr) is an RNA-binding protein required for erythropoiesis and strongly upregulated in erythroblasts relative to other hematopoietic progenitors. The aim of this study is to identify the Csde1-containing protein complexes and investigate their role in post-transcriptional expression control of Csde1-bound transcripts. We show that Serine/Threonine kinase receptor-associated protein (Strap/Unrip), was the protein most strongly associated with Csde1 in erythroblasts. Strap is a WD40 protein involved in signaling and RNA splicing, but its role when associated with Csde1 is unknown. Reduced expression of Strap did not alter the pool of transcripts bound by Csde1. Instead, it altered the mRNA and/or protein expression of several Csde1-bound transcripts that encode for proteins essential for translational regulation during hypoxia, such as Hmbs, eIF4g3 and Pabpc4. Also affected by Strap knockdown were Vim, a Gata-1 target crucial for erythrocyte enucleation, and Elavl1, which stabilizes Gata-1 mRNA. The major cellular processes affected by both Csde1 and Strap were ribosome function and cell cycle control.
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Affiliation(s)
- Kat S. Moore
- Sanquin Research, Department of Hematopoiesis, and Landsteiner Laboratory Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Nurcan Yagci
- Sanquin Research, Department of Hematopoiesis, and Landsteiner Laboratory Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Floris van Alphen
- Sanquin Research, Department of Research Facilities, Amsterdam, The Netherlands
| | - Alexander B. Meijer
- Sanquin Research, Department of Research Facilities, Amsterdam, The Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands
| | - Peter A. C. ‘t Hoen
- Centre for Molecular and Biomolecular Informatics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marieke von Lindern
- Sanquin Research, Department of Hematopoiesis, and Landsteiner Laboratory Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
- * E-mail:
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Rahmani K, Dean DA. Leptomycin B alters the subcellular distribution of CRM1 (Exportin 1). Biochem Biophys Res Commun 2017; 488:253-258. [PMID: 28412356 PMCID: PMC5551409 DOI: 10.1016/j.bbrc.2017.04.042] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 04/10/2017] [Indexed: 02/04/2023]
Abstract
CRM1 (chromosome maintenance region 1, Exportin 1) binds to nuclear export signals and is required for nucleocytoplasmic transport of a large variety of proteins and RNP complexes. Leptomycin B (LMB), the first specific inhibitor of CRM1 identified, binds covalently to cysteine 528 in the nuclear export signal binding region of CRM1 leading to the inhibition of protein nuclear export. Although the biochemical mechanisms of action of CRM1 inhibitors such as LMB are well studied, the subcellular effects of inhibition on CRM1 are unknown. We have found that LMB causes CRM1 to redistribute from the nucleus to the cytoplasm in A549 cells. A significant decrease in nuclear CRM1 coupled with an increase in cytoplasmic CRM1 was sustained for up to 4 h, while there was no change in total CRM1 protein in fractionated cells. Cells expressing an LMB insensitive HA-tagged CRM1-C528S protein were unaffected by LMB treatment, whereas HA-tagged wildtype CRM1 redistributed from the nucleus to the cytoplasm with LMB treatment, similar to endogenous CRM1. GFP-tagged CRM1 protein microinjected into the cytoplasm of A549 cells distributed throughout the cell in untreated cells remained primarily cytoplasmic in LMB-treated cells. Upon nuclear microinjection, GFP-CRM1 translocated to and accumulated in the cytoplasm of LMB-treated cells. Thus, LMB binds to CRM1 and causes its redistribution to the cytoplasm by inhibiting its nuclear import. Decreasing the nuclear availability of CRM1 likely contributes to the accumulation of CRM1 cargo proteins in the nucleus, suggesting a new mechanism of action for LMB.
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Affiliation(s)
- Khatera Rahmani
- Department of Pediatrics, University of Rochester School of Medicine, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - David A Dean
- Department of Pediatrics, University of Rochester School of Medicine, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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Abstract
Nuclear protein import and export assays in permeabilized cells have been instrumental for the identification of transport factors and for the molecular characterization of nucleocytoplasmic transport pathways. Our original assay to quantitatively analyze CRM1-dependent export was based on stably transfected cells expressing GFP-NFAT. We now present a simplified version of the assay using transiently transfected cells expressing GFP-NFAT or GFP-snurportin1 as a fluorescent export cargo and mCherry-emerin as a marker protein for transfected cells. CRM1- and Ran-dependent export is recapitulated in digitonin-permeabilized cells and quantified by flow cytometry. The assay should be applicable to other combinations of cargo and marker proteins.
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Affiliation(s)
- Ralph H Kehlenbach
- Faculty of Medicine, Institute of Molecular Biology, University of Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.
| | - Sarah A Port
- Faculty of Medicine, Institute of Molecular Biology, University of Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
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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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Dörr A, Pierre S, Zhang DD, Henke M, Holland S, Scholich K. MYCBP2 Is a Guanosine Exchange Factor for Ran Protein and Determines Its Localization in Neurons of Dorsal Root Ganglia. J Biol Chem 2015; 290:25620-35. [PMID: 26304119 DOI: 10.1074/jbc.m115.646901] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Indexed: 11/06/2022] Open
Abstract
The small GTPase Ran coordinates retrograde axonal transport in neurons, spindle assembly during mitosis, and the nucleo-cytoplasmic transport of mRNA. Its localization is tightly regulated by the GTPase-activating protein RanGAP1 and the nuclear guanosine exchange factor (GEF) RCC1. We show that loss of the neuronal E3 ubiquitin ligase MYCBP2 caused the up-regulation of Ran and RanGAP1 in dorsal root ganglia (DRG) under basal conditions and during inflammatory hyperalgesia. SUMOylated RanGAP1 physically interacted with MYCBP2 and inhibited its E3 ubiquitin ligase activity. Stimulation of neurons induced a RanGAP1-dependent translocation of MYCBP2 to the nucleus. In the nucleus of DRG neurons MYCBP2 co-localized with Ran and facilitated through its RCC1-like domain the GDP/GTP exchange of Ran. In accordance with the necessity of a GEF to promote GTP-binding and nuclear export of Ran, the nuclear localization of Ran was strongly increased in MYCBP2-deficient DRGs. The finding that other GEFs for Ran besides RCC1 exist gives new insights in the complexity of the regulation of the Ran signaling pathway.
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Affiliation(s)
- Angela Dörr
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Sandra Pierre
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Dong D Zhang
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Marina Henke
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Sabrina Holland
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Klaus Scholich
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
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Cautain B, Hill R, de Pedro N, Link W. Components and regulation of nuclear transport processes. FEBS J 2014; 282:445-62. [PMID: 25429850 PMCID: PMC7163960 DOI: 10.1111/febs.13163] [Citation(s) in RCA: 177] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 11/11/2014] [Accepted: 11/12/2014] [Indexed: 12/27/2022]
Abstract
The spatial separation of DNA replication and gene transcription in the nucleus and protein translation in the cytoplasm is a uniform principle of eukaryotic cells. This compartmentalization imposes a requirement for a transport network of macromolecules to shuttle these components in and out of the nucleus. This nucleo‐cytoplasmic transport of macromolecules is critical for both cell physiology and pathology. Consequently, investigating its regulation and disease‐associated alterations can reveal novel therapeutic approaches to fight human diseases, such as cancer or viral infection. The characterization of the nuclear pore complex, the identification of transport signals and transport receptors, as well as the characterization of the Ran system (providing the energy source for efficient cargo transport) has greatly facilitated our understanding of the components, mechanisms and regulation of the nucleo‐cytoplasmic transport of proteins in our cells. Here we review this knowledge with a specific emphasis on the selection of disease‐relevant molecular targets for potential therapeutic intervention.
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Affiliation(s)
- Bastien Cautain
- Fundacion MEDINA Parque tecnológico ciencias de la salud, Granada, Spain
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10
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Paronett EM, Meechan DW, Karpinski BA, LaMantia AS, Maynard TM. Ranbp1, Deleted in DiGeorge/22q11.2 Deletion Syndrome, is a Microcephaly Gene That Selectively Disrupts Layer 2/3 Cortical Projection Neuron Generation. Cereb Cortex 2014; 25:3977-93. [PMID: 25452572 DOI: 10.1093/cercor/bhu285] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Ranbp1, a Ran GTPase-binding protein implicated in nuclear/cytoplasmic trafficking, is included within the DiGeorge/22q11.2 Deletion Syndrome (22q11.2 DS) critical region associated with behavioral impairments including autism and schizophrenia. Ranbp1 is highly expressed in the developing forebrain ventricular/subventricular zone but has no known obligate function during brain development. We assessed the role of Ranbp1 in a targeted mouse mutant. Ranbp1(-/-) mice are not recovered live at birth, and over 60% of Ranbp1(-/-) embryos are exencephalic. Non-exencephalic Ranbp1(-/-) embryos are microcephalic, and proliferation of cortical progenitors is altered. At E10.5, radial progenitors divide more slowly in the Ranpb1(-/-) dorsal pallium. At E14.5, basal, but not apical/radial glial progenitors, are compromised in the cortex. In both E10.5 apical and E14.5 basal progenitors, M phase of the cell cycle appears selectively retarded by loss of Ranpb1 function. Ranbp1(-/-)-dependent proliferative deficits substantially diminish the frequency of layer 2/3, but not layer 5/6 cortical projection neurons. Ranbp1(-/-) cortical phenotypes parallel less severe alterations in LgDel mice that carry a deletion parallel to many (but not all) 22q11.2 DS patients. Thus, Ranbp1 emerges as a microcephaly gene within the 22q11.2 deleted region that may contribute to altered cortical precursor proliferation and neurogenesis associated with broader 22q11.2 deletion.
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Affiliation(s)
| | - Daniel W Meechan
- GW Institute for Neuroscience Department of Pharmacology and Physiology
| | - Beverly A Karpinski
- GW Institute for Neuroscience Department of Anatomy and Regenerative Biology, The George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
| | | | - Thomas M Maynard
- GW Institute for Neuroscience Department of Pharmacology and Physiology
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11
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Koyama M, Shirai N, Matsuura Y. Structural insights into how Yrb2p accelerates the assembly of the Xpo1p nuclear export complex. Cell Rep 2014; 9:983-95. [PMID: 25437554 DOI: 10.1016/j.celrep.2014.09.052] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 01/25/2014] [Accepted: 09/28/2014] [Indexed: 11/29/2022] Open
Abstract
Proteins and ribonucleoproteins containing a nuclear export signal (NES) assemble with the exportin Xpo1p (yeast CRM1) and Gsp1p-GTP (yeast Ran-GTP) in the nucleus and exit through the nuclear pore complex. In the cytoplasm, Yrb1p (yeast RanBP1) displaces NES from Xpo1p. Efficient export of NES-cargoes requires Yrb2p (yeast RanBP3), a primarily nuclear protein containing nucleoporin-like phenylalanine-glycine (FG) repeats and a low-affinity Gsp1p-binding domain (RanBD). Here, we show that Yrb2p strikingly accelerates the association of Gsp1p-GTP and NES to Xpo1p. We have solved the crystal structure of the Xpo1p-Yrb2p-Gsp1p-GTP complex, a key assembly intermediate that can bind cargo rapidly. Although the NES-binding cleft of Xpo1p is closed in this intermediate, our data suggest that preloading of Gsp1p-GTP onto Xpo1p by Yrb2p, conformational flexibility of Xpo1p, and the low affinity of RanBD enable active displacement of Yrb2p RanBD by NES to occur effectively. The structure also reveals the major binding sites for FG repeats on Xpo1p.
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Affiliation(s)
- Masako Koyama
- Division of Biological Science, Graduate School of Science, Nagoya University, 464-8602 Furo-cho, Chikusa-ku, Nagoya City, Japan
| | - Natsuki Shirai
- Division of Biological Science, Graduate School of Science, Nagoya University, 464-8602 Furo-cho, Chikusa-ku, Nagoya City, Japan
| | - Yoshiyuki Matsuura
- Division of Biological Science, Graduate School of Science, Nagoya University, 464-8602 Furo-cho, Chikusa-ku, Nagoya City, Japan; Structural Biology Research Center, Graduate School of Science, Nagoya University, 464-8602 Furo-cho, Chikusa-ku, Nagoya City, Japan.
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12
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Takeda A, Yaseen NR. Nucleoporins and nucleocytoplasmic transport in hematologic malignancies. Semin Cancer Biol 2014; 27:3-10. [PMID: 24657637 DOI: 10.1016/j.semcancer.2014.02.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 02/21/2014] [Indexed: 11/19/2022]
Abstract
Hematologic malignancies are often associated with chromosomal rearrangements that lead to the expression of chimeric fusion proteins. Rearrangements of the genes encoding two nucleoporins, NUP98 and NUP214, have been implicated in the pathogenesis of several types of hematologic malignancies, particularly acute myeloid leukemia. NUP98 rearrangements result in fusion of an N-terminal portion of NUP98 to one of numerous proteins. These rearrangements often follow treatment with topoisomerase II inhibitors and tend to occur in younger patients. They have been shown to induce leukemia in mice and to enhance proliferation and disrupt differentiation in primary human hematopoietic precursors. NUP214 has only a few fusion partners. DEK-NUP214 is the most common NUP214 fusion in AML; it tends to occur in younger patients and is usually associated with FLT3 internal tandem duplications. The leukemogenic activity of NUP214 fusions is less well characterized. Normal nucleoporins, including NUP98 and NUP214, have important functions in nucleocytoplasmic transport, transcription, and mitosis. These functions and their disruptions by oncogenic nucleoporin fusions are discussed.
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Affiliation(s)
- Akiko Takeda
- Department of Pathology and Immunology, Washington University in St. Louis, United States.
| | - Nabeel R Yaseen
- Department of Pathology and Immunology, Washington University in St. Louis, United States.
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Bernis C, Swift-Taylor B, Nord M, Carmona S, Chook YM, Forbes DJ. Transportin acts to regulate mitotic assembly events by target binding rather than Ran sequestration. Mol Biol Cell 2014; 25:992-1009. [PMID: 24478460 PMCID: PMC3967982 DOI: 10.1091/mbc.e13-08-0506] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Transportin-specific molecular tools are used to show that the mitotic cell contains importin β and transportin “global positioning system” pathways that are mechanistically parallel. Transportin works to control where the spindle, nuclear membrane, and nuclear pores are formed by directly affecting assembly factor function. The nuclear import receptors importin β and transportin play a different role in mitosis: both act phenotypically as spatial regulators to ensure that mitotic spindle, nuclear membrane, and nuclear pore assembly occur exclusively around chromatin. Importin β is known to act by repressing assembly factors in regions distant from chromatin, whereas RanGTP produced on chromatin frees factors from importin β for localized assembly. The mechanism of transportin regulation was unknown. Diametrically opposed models for transportin action are as follows: 1) indirect action by RanGTP sequestration, thus down-regulating release of assembly factors from importin β, and 2) direct action by transportin binding and inhibiting assembly factors. Experiments in Xenopus assembly extracts with M9M, a superaffinity nuclear localization sequence that displaces cargoes bound by transportin, or TLB, a mutant transportin that can bind cargo and RanGTP simultaneously, support direct inhibition. Consistently, simple addition of M9M to mitotic cytosol induces microtubule aster assembly. ELYS and the nucleoporin 107–160 complex, components of mitotic kinetochores and nuclear pores, are blocked from binding to kinetochores in vitro by transportin, a block reversible by M9M. In vivo, 30% of M9M-transfected cells have spindle/cytokinesis defects. We conclude that the cell contains importin β and transportin “global positioning system”or “GPS” pathways that are mechanistically parallel.
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Affiliation(s)
- Cyril Bernis
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California-San Diego, La Jolla, CA 92093-0347 Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041
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Encephalomyocarditis virus Leader protein hinge domain is responsible for interactions with Ran GTPase. Virology 2013; 443:177-85. [PMID: 23711384 DOI: 10.1016/j.virol.2013.05.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 02/28/2013] [Accepted: 05/02/2013] [Indexed: 11/21/2022]
Abstract
Encephalomyocarditis virus (EMCV), a Cardiovirus, initiates its polyprotein with a short 67 amino acid Leader (L) sequence. The protein acts as a unique pathogenicity factor, with anti-host activities which include the triggering of nuclear pore complex hyperphosphorylation and direct binding inhibition of the active cellular transport protein, Ran GTPase. Chemical modifications and protein mutagenesis now map the Ran binding domain to the L hinge-linker region, and in particular, to amino acids 35-40. Large deletions affecting this region were shown previously to diminish Ran binding. New point mutations, especially K35Q, D37A and W40A, preserve the intact L structure, abolish Ran binding and are deficient for nucleoporin (Nup) hyperphosphorylation. Ran itself morphs through multiple configurations, but reacts most effectively with L when in the GDP format, preferably with an empty nucleotide binding pocket. Therefore, L:Ran binding, mediated by the linker-hinge, is a required step in L-induced nuclear transport inhibition.
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15
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Thakar K, Karaca S, Port SA, Urlaub H, Kehlenbach RH. Identification of CRM1-dependent Nuclear Export Cargos Using Quantitative Mass Spectrometry. Mol Cell Proteomics 2013; 12:664-78. [PMID: 23242554 PMCID: PMC3591659 DOI: 10.1074/mcp.m112.024877] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Revised: 11/23/2012] [Indexed: 11/06/2022] Open
Abstract
Chromosome region maintenance 1/exportin1/Exp1/Xpo1 (CRM1) is the major transport receptor for the export of proteins from the nucleus. It binds to nuclear export signals (NESs) that are rich in leucines and other hydrophobic amino acids. The prediction of NESs is difficult because of the extreme recognition flexibility of CRM1. Furthermore, proteins can be exported upon binding to an NES-containing adaptor protein. Here we present an approach for identifying targets of the CRM1-export pathway via quantitative mass spectrometry using stable isotope labeling with amino acids in cell culture. With this approach, we identified >100 proteins from HeLa cells that were depleted from cytosolic fractions and/or enriched in nuclear fractions in the presence of the selective CRM1-inhibitor leptomycin B. Novel and validated substrates are the polyubiquitin-binding protein sequestosome 1, the cancerous inhibitor of protein phosphatase 2A (PP2A), the guanine nucleotide-binding protein-like 3-like protein, the programmed cell death protein 2-like protein, and the cytosolic carboxypeptidase 1 (CCP1). We identified a functional NES in CCP1 that mediates direct binding to the export receptor CRM1. The method will be applicable to other nucleocytoplasmic transport pathways, as well as to the analysis of nucleocytoplasmic shuttling proteins under different growth conditions.
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Affiliation(s)
- Ketan Thakar
- From the ‡Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Samir Karaca
- ¶Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Sarah A. Port
- From the ‡Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Henning Urlaub
- ¶Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
- ‖Bioanalytics, Department of Clinical Chemistry, University Medical Center, Robert-Koch-Str. 40, 37075 Göttingen, Germany
| | - Ralph H. Kehlenbach
- From the ‡Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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Roloff S, Spillner C, Kehlenbach RH. Several phenylalanine-glycine motives in the nucleoporin Nup214 are essential for binding of the nuclear export receptor CRM1. J Biol Chem 2013; 288:3952-63. [PMID: 23264634 PMCID: PMC3567648 DOI: 10.1074/jbc.m112.433243] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 12/12/2012] [Indexed: 02/06/2023] Open
Abstract
Nucleoporins containing phenylalanine glycine (FG) repeats play an important role in nucleocytoplasmic transport as they bind to transport receptors and mediate translocation of transport complexes across the nuclear pore complex (NPC). Nup214/CAN, a nucleoporin that is found at the cytoplasmic side of the NPC, interacts with both import and export receptors. In functional assays, dominant-negative fragments of Nup214 inhibited CRM1-dependent nuclear export, as the export receptor became rate-limiting. Several nuclear import pathways, by contrast, were not affected by the Nup214 fragments. We now characterize the CRM1-binding region of Nup214 in detail and identify several FG motives that are required for this interaction. Our results support a model where CRM1, like other transport receptors, contacts FG-Nups via multiple binding sites.
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Affiliation(s)
- Stephanie Roloff
- From the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Christiane Spillner
- From the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Ralph H. Kehlenbach
- From the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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17
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Waldmann I, Spillner C, Kehlenbach RH. The nucleoporin-like protein NLP1 (hCG1) promotes CRM1-dependent nuclear protein export. J Cell Sci 2012; 125:144-54. [PMID: 22250199 DOI: 10.1242/jcs.090316] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Translocation of transport complexes across the nuclear envelope is mediated by nucleoporins, proteins of the nuclear pore complex that contain phenylalanine-glycine (FG) repeats as a characteristic binding motif for transport receptors. CRM1 (exportin 1), the major export receptor, forms trimeric complexes with RanGTP and proteins containing nuclear export sequences (NESs). We analyzed the role of the nucleoporin-like protein 1, NLP1 (also known as hCG1 and NUPL2) in CRM1-dependent nuclear transport. NLP1, which contains many FG repeats, localizes to the nuclear envelope and could also be mobile within the nucleus. It promotes the formation of complexes containing CRM1 and RanGTP, with or without NES-containing cargo proteins, that can be dissociated by RanBP1 and/or the cytoplasmic nucleoporin Nup214. The FG repeats of NLP1 do not play a major role in CRM1 binding. Overexpression of NLP1 promotes CRM1-dependent export of certain cargos, whereas its depletion by small interfering RNAs leads to reduced export rates. Thus, NLP1 functions as an accessory factor in CRM1-dependent nuclear protein export.
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Affiliation(s)
- Inga Waldmann
- Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Göttingen, Germany
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18
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Hilliard M, Frohnert C, Spillner C, Marcone S, Nath A, Lampe T, Fitzgerald DJ, Kehlenbach RH. The anti-inflammatory prostaglandin 15-deoxy-delta(12,14)-PGJ2 inhibits CRM1-dependent nuclear protein export. J Biol Chem 2010; 285:22202-10. [PMID: 20457605 PMCID: PMC2903415 DOI: 10.1074/jbc.m110.131821] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/06/2010] [Indexed: 12/30/2022] Open
Abstract
The signaling molecule 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) has been described as the "anti-inflammatory prostaglandin." Here we show that substrates of the nuclear export receptor CRM1 accumulate in the nucleus in the presence of 15d-PGJ(2), identifying this prostaglandin as a regulator of CRM1-dependent nuclear protein export that can be produced endogenously. Like leptomycin B (LMB), an established fungal CRM1-inhibitor, 15d-PGJ(2) reacts with a conserved cysteine residue in the CRM1 sequence. This covalent modification prevents the formation of nuclear export complexes. Cells that are transfected with mutant CRM1 (C528S) are resistant to the inhibitory effects of LMB and 15d-PGJ(2), demonstrating that the same single amino acid is targeted by the two compounds. Inhibition of the CRM1 pathway by endogenously produced prostaglandin and/or exogenously applied 15d-PGJ(2) may contribute to its anti-inflammatory, anti-proliferative, and anti-viral effects.
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Affiliation(s)
- Mark Hilliard
- From the UCD Conway Institute, Belfield, Dublin 4, Ireland and
| | - Cornelia Frohnert
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Christiane Spillner
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Simone Marcone
- From the UCD Conway Institute, Belfield, Dublin 4, Ireland and
| | - Annegret Nath
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Tina Lampe
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | | | - Ralph H. Kehlenbach
- the Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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19
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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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20
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Ben-Efraim I, Frosst PD, Gerace L. Karyopherin binding interactions and nuclear import mechanism of nuclear pore complex protein Tpr. BMC Cell Biol 2009; 10:74. [PMID: 19835572 PMCID: PMC2770460 DOI: 10.1186/1471-2121-10-74] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Accepted: 10/16/2009] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Tpr is a large protein with an extended coiled-coil domain that is localized within the nuclear basket of the nuclear pore complex. Previous studies 1 involving antibody microinjection into mammalian cells suggested a role for Tpr in nuclear export of proteins via the CRM1 export receptor. In addition, Tpr was found to co-immunoprecipitate with importins alpha and beta from Xenopus laevis egg extracts 2, although the function of this is unresolved. Yeast Mlp1p and Mlp2p, which are homologous to vertebrate Tpr, have been implicated in mRNA surveillance to retain unspliced mRNAs in the nucleus34. To augment an understanding of the role of Tpr in nucleocytoplasmic trafficking, we explored the interactions of recombinant Tpr with the karyopherins CRM1, importin beta and importin alpha by solid phase binding assays. We also investigated the conditions required for nuclear import of Tpr using an in vitro assay. RESULTS We found that Tpr binds strongly and specifically to importin alpha, importin beta, and a CRM1 containing trimeric export complex, and that the binding sites for importins alpha and beta are distinct. We also determined that the nuclear import of Tpr is dependent on cytosolic factors and energy and is efficiently mediated by the importin alpha/beta import pathway. CONCLUSION Based on the binding and nuclear import assays, we propose that Tpr is imported into the nucleus by the importin alpha/beta heterodimer. In addition, we suggest that Tpr can serve as a nucleoporin binding site for importin beta during import of importin beta cargo complexes and/or importin beta recycling. Our finding that Tpr bound preferentially to CRM1 in an export complex strengthens the notion that Tpr is involved in protein export.
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Affiliation(s)
- Iris Ben-Efraim
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Phyllis D Frosst
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
- National Human Genome Research Institute, National Institutes of Health Bethesda, Maryland 20892, USA
| | - Larry Gerace
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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21
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Hutten S, Flotho A, Melchior F, Kehlenbach RH. The Nup358-RanGAP complex is required for efficient importin alpha/beta-dependent nuclear import. Mol Biol Cell 2008; 19:2300-10. [PMID: 18305100 DOI: 10.1091/mbc.e07-12-1279] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In vertebrate cells, the nucleoporin Nup358/RanBP2 is a major component of the filaments that emanate from the nuclear pore complex into the cytoplasm. Nup358 forms a complex with SUMOylated RanGAP1, the GTPase activating protein for Ran. RanGAP1 plays a pivotal role in the establishment of a RanGTP gradient across the nuclear envelope and, hence, in the majority of nucleocytoplasmic transport pathways. Here, we investigate the roles of the Nup358-RanGAP1 complex and of soluble RanGAP1 in nuclear protein transport, combining in vivo and in vitro approaches. Depletion of Nup358 by RNA interference led to a clear reduction of importin alpha/beta-dependent nuclear import of various reporter proteins. In vitro, transport could be partially restored by the addition of importin beta, RanBP1, and/or RanGAP1 to the transport reaction. In intact Nup358-depleted cells, overexpression of importin beta strongly stimulated nuclear import, demonstrating that the transport receptor is the most rate-limiting factor at reduced Nup358-concentrations. As an alternative approach, we used antibody-inhibition experiments. Antibodies against RanGAP1 inhibited the enzymatic activity of soluble and nuclear pore-associated RanGAP1, as well as nuclear import and export. Although export could be fully restored by soluble RanGAP, import was only partially rescued. Together, these data suggest a dual function of the Nup358-RanGAP1 complex as a coordinator of importin beta recycling and reformation of novel import complexes.
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Affiliation(s)
- Saskia Hutten
- Department of Biochemistry I, Faculty of Medicine, Georg-August University of Göttingen, 37073, Göttingen, Germany
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22
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Faustino RS, Cheung P, Richard MN, Dibrov E, Kneesch AL, Deniset JF, Chahine MN, Lee K, Blackwood D, Pierce GN. Ceramide regulation of nuclear protein import. J Lipid Res 2007; 49:654-62. [PMID: 18083977 DOI: 10.1194/jlr.m700464-jlr200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nucleocytoplasmic trafficking is an essential and responsive cellular mechanism that directly affects cell growth and proliferation, and its potential to address metabolic challenge is incompletely defined. Ceramide is an antiproliferative sphingolipid found within vascular smooth muscle cells in atherosclerotic plaques, but its mechanism of action remains unclear. The hypothesis that ceramide inhibits cell growth through nuclear transport regulation was tested. In smooth muscle cells, exogenously supplemented ceramide inhibited classical nuclear protein import that involved the activation of cytosolic p38 mitogen-activated protein kinase (MAPK). After application of SB 202190, a specific and potent pharmacological antagonist of p38 MAPK, sphingolipid impingement on nuclear transport was corrected. Distribution pattern assessments of two essential nuclear transport proteins, importin-alpha and Cellular Apoptosis Susceptibility, revealed ceramide-mediated relocalization that was reversed upon the addition of SB 202190. Furthermore, cell counts, nuclear cyclin A, and proliferating cell nuclear antigen expression, markers of cellular proliferation, were diminished after ceramide treatment and effectively rescued by the addition of inhibitor. Together, these data demonstrate, for the first time, the sphingolipid regulation of nuclear import that defines and expands the adaptive capacity of the nucleocytoplasmic transport machinery.
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Affiliation(s)
- Randolph S Faustino
- Institute of Cardiovascular Sciences, St. Boniface Hospital Research Centre, Department of Physiology, Faculties of Medicine and Pharmacy, University of Manitoba, Winnipeg, Manitoba, Canada
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23
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Hutten S, Kehlenbach RH. CRM1-mediated nuclear export: to the pore and beyond. Trends Cell Biol 2007; 17:193-201. [PMID: 17317185 DOI: 10.1016/j.tcb.2007.02.003] [Citation(s) in RCA: 290] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 01/11/2007] [Accepted: 02/09/2007] [Indexed: 02/07/2023]
Abstract
CRM1 (chromosome region maintenance 1; also referred to as exportin1 or Xpo1) is a member of the importin beta superfamily of nuclear transport receptors, recognizing proteins bearing a leucine-rich nuclear export sequence. CRM1 is the major receptor for the export of proteins out of the nucleus and is also required for transport of many RNAs. Besides its established role in nuclear export, CRM1 is also implicated in various steps during mitosis, widening its functional spectrum within the cell.
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Affiliation(s)
- Saskia Hutten
- Universität Göttingen; Zentrum für Biochemie und Molekulare Zellbiologie; Humboldtallee 23; 37073 Göttingen, Germany
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24
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Wodrich H, Cassany A, D'Angelo MA, Guan T, Nemerow G, Gerace L. Adenovirus core protein pVII is translocated into the nucleus by multiple import receptor pathways. J Virol 2006; 80:9608-18. [PMID: 16973564 PMCID: PMC1617226 DOI: 10.1128/jvi.00850-06] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Adenoviruses are nonenveloped viruses with an approximately 36-kb double-stranded DNA genome that replicate in the nucleus. Protein VII, an abundant structural component of the adenovirus core that is strongly associated with adenovirus DNA, is imported into the nucleus contemporaneously with the adenovirus genome shortly after virus infection and may promote DNA import. In this study, we evaluated whether protein VII uses specific receptor-mediated mechanisms for import into the nucleus. We found that it contains potent nuclear localization signal (NLS) activity by transfection of cultured cells with protein VII fusion constructs and by microinjection of cells with recombinant protein VII fusions. We identified three NLS-containing regions in protein VII by deletion mapping and determined important NLS residues by site-specific mutagenesis. We found that recombinant protein VII and its NLS-containing domains strongly and specifically bind to importin alpha, importin beta, importin 7, and transportin, which are among the most abundant cellular nuclear import receptors. Moreover, these receptors can mediate the nuclear import of protein VII fusions in vitro in permeabilized cells. Considered together, these data support the hypothesis that protein VII is a major NLS-containing adaptor for receptor-mediated import of adenovirus DNA and that multiple import pathways are utilized to promote efficient nuclear entry of the viral genome.
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Affiliation(s)
- Harald Wodrich
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 05, France.
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25
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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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26
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Hutten S, Kehlenbach RH. Nup214 is required for CRM1-dependent nuclear protein export in vivo. Mol Cell Biol 2006; 26:6772-85. [PMID: 16943420 PMCID: PMC1592874 DOI: 10.1128/mcb.00342-06] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 03/24/2006] [Accepted: 06/30/2006] [Indexed: 11/20/2022] Open
Abstract
Nucleoporins mediate transport of macromolecules across the nuclear pore complex, yet the function of many individual nucleoporins is largely unresolved. To address this question, we depleted cells of the cytoplasmic nucleoporins Nup214/CAN and Nup358/RanBP2 by RNA interference. Depletion of Nup214 resulted in codepletion of its binding partner, Nup88. Nuclear pore complexes assembled in the absence of Nup214/Nup88 or Nup358 were fully functional in nuclear protein import, whereas nuclear mRNA export was slightly impaired. Depletion of Nup358 had only a minor effect on nuclear protein export. In contrast, depletion of Nup214/Nup88 led to strongly reduced CRM1-mediated export of the shuttling transcription factor NFAT as well as a human immunodeficiency virus-Rev derivative. A specific role of Nup214 in protein export is furthered by the biochemical properties of a high-affinity complex containing Nup214, CRM1, RanGTP, and an export cargo. Our results show that the Nup214/Nup88 complex is required for efficient CRM1-mediated transport, supporting a model involving a high-affinity binding site for CRM1 at Nup214 in the terminal steps of export.
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Affiliation(s)
- Saskia Hutten
- Universität Göttingen, Zentrum für Biochemie und Molekulare Zellbiologie, Humboldtallee 23, 37073 Göttingen, Germany
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27
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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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Wodrich H, Guan T, Cingolani G, Von Seggern D, Nemerow G, Gerace L. Switch from capsid protein import to adenovirus assembly by cleavage of nuclear transport signals. EMBO J 2004; 22:6245-55. [PMID: 14633984 PMCID: PMC291855 DOI: 10.1093/emboj/cdg614] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Replication and assembly of adenovirus occurs in the nucleus of infected cells, requiring the nuclear import of all viral structural proteins. In this report we show that nuclear import of the major capsid protein, hexon, is mediated by protein VI, a structural protein located underneath the 12 vertices of the adenoviral capsid. Our data indicate that protein VI shuttles between the nucleus and the cytoplasm and that it links hexon to the nuclear import machinery via an importin alpha/beta-dependent mechanism. Key nuclear import and export signals of protein VI are located in a short C-terminal segment, which is proteolytically removed during virus maturation. The removal of these C-terminal transport signals appears to trigger a functional transition in protein VI, from a role in supporting hexon nuclear import to a structural role in virus assembly.
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Affiliation(s)
- Harald Wodrich
- Department of Cell Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
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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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