1
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Heber S, McClintock MA, Simon B, Mehtab E, Lapouge K, Hennig J, Bullock SL, Ephrussi A. Tropomyosin 1-I/C coordinates kinesin-1 and dynein motors during oskar mRNA transport. Nat Struct Mol Biol 2024; 31:476-488. [PMID: 38297086 PMCID: PMC10948360 DOI: 10.1038/s41594-024-01212-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 01/02/2024] [Indexed: 02/02/2024]
Abstract
Dynein and kinesin motors mediate long-range intracellular transport, translocating towards microtubule minus and plus ends, respectively. Cargoes often undergo bidirectional transport by binding to both motors simultaneously. However, it is not known how motor activities are coordinated in such circumstances. In the Drosophila female germline, sequential activities of the dynein-dynactin-BicD-Egalitarian (DDBE) complex and of kinesin-1 deliver oskar messenger RNA from nurse cells to the oocyte, and within the oocyte to the posterior pole. We show through in vitro reconstitution that Tm1-I/C, a tropomyosin-1 isoform, links kinesin-1 in a strongly inhibited state to DDBE-associated oskar mRNA. Nuclear magnetic resonance spectroscopy, small-angle X-ray scattering and structural modeling indicate that Tm1-I/C suppresses kinesin-1 activity by stabilizing its autoinhibited conformation, thus preventing competition with dynein until kinesin-1 is activated in the oocyte. Our work reveals a new strategy for ensuring sequential activity of microtubule motors.
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Affiliation(s)
- Simone Heber
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Mark A McClintock
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Bernd Simon
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA
| | - Eve Mehtab
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Karine Lapouge
- Protein Expression and Purification Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Janosch Hennig
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Biochemistry IV, Biophysical Chemistry, University of Bayreuth, Bayreuth, Germany
| | - Simon L Bullock
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, UK.
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
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2
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Wippich F, Vaishali, Hennrich ML, Ephrussi A. Nutritional stress-induced regulation of microtubule organization and mRNP transport by HDAC1 controlled α-tubulin acetylation. Commun Biol 2023; 6:776. [PMID: 37491525 PMCID: PMC10368696 DOI: 10.1038/s42003-023-05138-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 07/12/2023] [Indexed: 07/27/2023] Open
Abstract
In response to nutritional stress, microtubules in cells of the Drosophila female germline are depleted from the cytoplasm and accumulate cortically. This triggers aggregation of mRNPs into large processing bodies (P-bodies) and oogenesis arrest. Here, we show that hyperacetylation of α-tubulin at lysine 40 (K40) alters microtubule dynamics and P-body formation. We found that depletion of histone deacetylase 1 (HDAC1) by RNAi phenocopies the nutritional stress response, causing α-tubulin hyperacetylation and accumulation of maternally deposited mRNPs in P-bodies. Through in vitro and in vivo studies, we identify HDAC1 as a direct regulator of α-tubulin K40 acetylation status. In well-fed flies, HDAC1 maintains low levels of α-tubulin acetylation, enabling the microtubule dynamics required for mRNP transport. Using quantitative phosphoproteomics we identify nutritional stress-induced changes in protein phosphorylation that act upstream of α-tubulin acetylation, including phosphorylation of HDAC1 at S391, which reduces its ability to deacetylate α-tubulin. These results reveal that Drosophila HDAC1 senses and relays the nutritional status, which regulates germline development through modulation of cytoskeleton dynamics.
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Affiliation(s)
- Frank Wippich
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg, 69117, Germany
- Cellzome GmbH, GlaxoSmithKline, Heidelberg, Germany
| | - Vaishali
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg, 69117, Germany
- Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Marco L Hennrich
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg, 69117, Germany
- Cellzome GmbH, GlaxoSmithKline, Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, Meyerhofstrasse 1, Heidelberg, 69117, Germany.
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3
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Gáspár I, Phea LJ, McClintock MA, Heber S, Bullock SL, Ephrussi A. An RNA-based feed-forward mechanism ensures motor switching in oskar mRNA transport. J Cell Biol 2023; 222:214126. [PMID: 37213090 DOI: 10.1083/jcb.202301113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 04/01/2023] [Accepted: 04/05/2023] [Indexed: 05/23/2023] Open
Abstract
Regulated recruitment and activity of motor proteins is essential for intracellular transport of cargoes, including messenger ribonucleoprotein complexes (RNPs). Here, we show that orchestration of oskar RNP transport in the Drosophila germline relies on interplay between two double-stranded RNA-binding proteins, Staufen and the dynein adaptor Egalitarian (Egl). We find that Staufen antagonizes Egl-mediated transport of oskar mRNA by dynein both in vitro and in vivo. Following delivery of nurse cell-synthesized oskar mRNA into the oocyte by dynein, recruitment of Staufen to the RNPs results in dissociation of Egl and a switch to kinesin-1-mediated translocation of the mRNA to its final destination at the posterior pole of the oocyte. We additionally show that Egl associates with staufen (stau) mRNA in the nurse cells, mediating its enrichment and translation in the ooplasm. Our observations identify a novel feed-forward mechanism, whereby dynein-dependent accumulation of stau mRNA, and thus protein, in the oocyte enables motor switching on oskar RNPs by downregulating dynein activity.
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Affiliation(s)
- Imre Gáspár
- Developmental Biology Unit, European Molecular Biology Laboratory , Heidelberg, Germany
| | - Ly Jane Phea
- Developmental Biology Unit, European Molecular Biology Laboratory , Heidelberg, Germany
| | - Mark A McClintock
- Division of Cell Biology, MRC Laboratory of Molecular Biology , Cambridge, UK
| | - Simone Heber
- Developmental Biology Unit, European Molecular Biology Laboratory , Heidelberg, Germany
| | - Simon L Bullock
- Division of Cell Biology, MRC Laboratory of Molecular Biology , Cambridge, UK
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory , Heidelberg, Germany
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4
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Bose M, Lampe M, Mahamid J, Ephrussi A. Liquid-to-solid phase transition of oskar ribonucleoprotein granules is essential for their function in Drosophila embryonic development. Cell 2022; 185:1308-1324.e23. [PMID: 35325593 PMCID: PMC9042795 DOI: 10.1016/j.cell.2022.02.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 11/24/2021] [Accepted: 02/18/2022] [Indexed: 01/05/2023]
Abstract
Asymmetric localization of oskar ribonucleoprotein (RNP) granules to the oocyte posterior is crucial for abdominal patterning and germline formation in the Drosophila embryo. We show that oskar RNP granules in the oocyte are condensates with solid-like physical properties. Using purified oskar RNA and scaffold proteins Bruno and Hrp48, we confirm in vitro that oskar granules undergo a liquid-to-solid phase transition. Whereas the liquid phase allows RNA incorporation, the solid phase precludes incorporation of additional RNA while allowing RNA-dependent partitioning of client proteins. Genetic modification of scaffold granule proteins or tethering the intrinsically disordered region of human fused in sarcoma (FUS) to oskar mRNA allowed modulation of granule material properties in vivo. The resulting liquid-like properties impaired oskar localization and translation with severe consequences on embryonic development. Our study reflects how physiological phase transitions shape RNA-protein condensates to regulate the localization and expression of a maternal RNA that instructs germline formation. oskar RNP granules in the developing oocyte are solid-like condensates oskar RNP granules undergo liquid-to-solid phase transition in vitro The liquid phase incorporates mRNA, while the solid phase enriches specific proteins Perturbing the solid state impairs oskar localization, translation, and development
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Affiliation(s)
- Mainak Bose
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | - Marko Lampe
- Advanced Light Microscopy Facility, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
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5
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Abstract
Live-imaging of axonal cargoes within central nervous system has been a long-lasting interest for neurobiologists as axonal transport plays critical roles in neuronal growth, function, and survival. Many kinds of cargoes are transported within axons, including synaptic vesicles and a variety of membrane-bound and membrane-less organelles. Imaging these cargoes at high spatial and temporal resolution, and within living brains, is technically very challenging. Here, we describe a quantitative method, based on customized mounting chambers, allowing live-imaging of axonal cargoes transported within the maturing brain of the fruit fly, Drosophila melanogaster. With this method, we could visualize in real time, using confocal microscopy, cargoes transported along axons. Our protocol is simple and easy to set up, as brains are mounted in our imaging chambers and ready to be imaged in about 1 h. Another advantage of our method is that it can be combined with pharmacological treatments or super-resolution microscopy.
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Affiliation(s)
| | - Anne Ephrussi
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
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6
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Medioni C, Vijayakumar J, Ephrussi A, Besse F. High-Resolution Live Imaging of Axonal RNP Granules in Drosophila Pupal Brain Explants. Methods Mol Biol 2022; 2431:451-462. [PMID: 35412292 DOI: 10.1007/978-1-0716-1990-2_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Dynamic and local adjustments of the axonal proteome are observed in response to extracellular cues and achieved via translation of axonally localized mRNAs. To be localized, these mRNAs must be recognized by RNA binding proteins and packaged into higher-order ribonucleoprotein (RNP) granules transported along axonal microtubules via molecular motors. Axonal recruitment of RNP granules is not constitutive, but rather regulated by external signals such as developmental cues, through pathways yet to be identified. The Drosophila brain represents an excellent model system where to study the transport of RNP granules as it is triggered in specific populations of neurons undergoing remodeling during metamorphosis. Here, we describe a protocol enabling live imaging of axonal RNP granule transport with high spatiotemporal resolution in Drosophila maturing brains. In this protocol, pupal brains expressing endogenous or ectopic fluorescent RNP components are dissected, mounted in a customized imaging chamber, and imaged with an inverted confocal microscope equipped with sensitive detectors. Axonal RNP granules are then individually tracked for further analysis of their trajectories. This protocol is rapid (less than 1 hour to prepare brains for imaging) and is easy to handle and to implement.
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Affiliation(s)
- Caroline Medioni
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
| | - Jeshlee Vijayakumar
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
| | - Anne Ephrussi
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Florence Besse
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France.
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7
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Vaishali, Dimitrova-Paternoga L, Haubrich K, Sun M, Ephrussi A, Hennig J. Validation and classification of RNA binding proteins identified by mRNA interactome capture. RNA 2021; 27:1173-1185. [PMID: 34215685 PMCID: PMC8456996 DOI: 10.1261/rna.078700.121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 06/29/2021] [Indexed: 06/13/2023]
Abstract
RNA binding proteins (RBPs) take part in all steps of the RNA life cycle and are often essential for cell viability. Most RBPs have a modular organization and comprise a set of canonical RNA binding domains. However, in recent years a number of high-throughput mRNA interactome studies on yeast, mammalian cell lines, and whole organisms have uncovered a multitude of novel mRNA interacting proteins that lack classical RNA binding domains. Whereas a few have been confirmed to be direct and functionally relevant RNA binders, biochemical and functional validation of RNA binding of most others is lacking. In this study, we used a combination of NMR spectroscopy and biochemical studies to test the RNA binding properties of six putative RBPs. Half of the analyzed proteins showed no interaction, whereas the other half displayed weak chemical shift perturbations upon titration with RNA. One of the candidates we found to interact weakly with RNA in vitro is Drosophila melanogaster end binding protein 1 (EB1), a master regulator of microtubule plus-end dynamics. Further analysis showed that EB1's RNA binding occurs on the same surface as that with which EB1 interacts with microtubules. RNA immunoprecipitation and colocalization experiments suggest that EB1 is a rather nonspecific, opportunistic RNA binder. Our data suggest that care should be taken when embarking on an RNA binding study involving these unconventional, novel RBPs, and we recommend initial and simple in vitro RNA binding experiments.
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Affiliation(s)
- Vaishali
- Developmental Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
- Faculty of Biosciences, Heidelberg University, Heidelberg 69120, Germany
| | - Lyudmila Dimitrova-Paternoga
- Developmental Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
- Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Kevin Haubrich
- Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Mai Sun
- Genome Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Janosch Hennig
- Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
- Biochemistry IV, Biophysical Chemistry, University of Bayreuth, 95447 Bayreuth, Germany
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8
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Ronchi P, Mizzon G, Machado P, D’Imprima E, Best BT, Cassella L, Schnorrenberg S, Montero MG, Jechlinger M, Ephrussi A, Leptin M, Mahamid J, Schwab Y. High-precision targeting workflow for volume electron microscopy. J Cell Biol 2021; 220:e202104069. [PMID: 34160561 PMCID: PMC8225610 DOI: 10.1083/jcb.202104069] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 05/27/2021] [Accepted: 06/06/2021] [Indexed: 02/07/2023] Open
Abstract
Cells are 3D objects. Therefore, volume EM (vEM) is often crucial for correct interpretation of ultrastructural data. Today, scanning EM (SEM) methods such as focused ion beam (FIB)-SEM are frequently used for vEM analyses. While they allow automated data acquisition, precise targeting of volumes of interest within a large sample remains challenging. Here, we provide a workflow to target FIB-SEM acquisition of fluorescently labeled cells or subcellular structures with micrometer precision. The strategy relies on fluorescence preservation during sample preparation and targeted trimming guided by confocal maps of the fluorescence signal in the resin block. Laser branding is used to create landmarks on the block surface to position the FIB-SEM acquisition. Using this method, we acquired volumes of specific single cells within large tissues such as 3D cultures of mouse mammary gland organoids, tracheal terminal cells in Drosophila melanogaster larvae, and ovarian follicular cells in adult Drosophila, discovering ultrastructural details that could not be appreciated before.
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Affiliation(s)
- Paolo Ronchi
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Giulia Mizzon
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Pedro Machado
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Edoardo D’Imprima
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Benedikt T. Best
- Directors’ Research, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Lucia Cassella
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Faculty of Biosciences, Heidelberg University, Heidelberg, Germany
| | - Sebastian Schnorrenberg
- Advanced Light Microscopy Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Marta G. Montero
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Martin Jechlinger
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Maria Leptin
- Directors’ Research, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Yannick Schwab
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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9
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Dimitrova-Paternoga L, Jagtap PKA, Cyrklaff A, Vaishali, Lapouge K, Sehr P, Perez K, Heber S, Löw C, Hennig J, Ephrussi A. Molecular basis of mRNA transport by a kinesin-1-atypical tropomyosin complex. Genes Dev 2021; 35:976-991. [PMID: 34140355 PMCID: PMC8247599 DOI: 10.1101/gad.348443.121] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/14/2021] [Indexed: 11/24/2022]
Abstract
Here, Dimitrova-Paternoga et al. present the high-resolution crystal structure of Khc–aTm1 (Drosophila kinesin-1, also called kinesin heavy chain [Khc], in complex with a putative cargo adaptor, the atypical tropomyosin [aTm1]), which mediates transport of oskar mRNA to the posterior pole of the Drosophila oocyte. They show that aTm1 binds to an evolutionarily conserved cargo binding site on Khc, demonstrate that Khc binds RNA directly, and show that aTm1 plays a stabilizing role in the interaction of Khc with RNA, which distinguishes aTm1 from classical motor adaptors. Kinesin-1 carries cargos including proteins, RNAs, vesicles, and pathogens over long distances within cells. The mechanochemical cycle of kinesins is well described, but how they establish cargo specificity is not fully understood. Transport of oskar mRNA to the posterior pole of the Drosophila oocyte is mediated by Drosophila kinesin-1, also called kinesin heavy chain (Khc), and a putative cargo adaptor, the atypical tropomyosin, aTm1. How the proteins cooperate in mRNA transport is unknown. Here, we present the high-resolution crystal structure of a Khc–aTm1 complex. The proteins form a tripartite coiled coil comprising two in-register Khc chains and one aTm1 chain, in antiparallel orientation. We show that aTm1 binds to an evolutionarily conserved cargo binding site on Khc, and mutational analysis confirms the importance of this interaction for mRNA transport in vivo. Furthermore, we demonstrate that Khc binds RNA directly and that it does so via its alternative cargo binding domain, which forms a positively charged joint surface with aTm1, as well as through its adjacent auxiliary microtubule binding domain. Finally, we show that aTm1 plays a stabilizing role in the interaction of Khc with RNA, which distinguishes aTm1 from classical motor adaptors.
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Affiliation(s)
- Lyudmila Dimitrova-Paternoga
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, 69117 Heidelberg, Germany.,Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany.,Centre for Structural Systems Biology (CSSB), Deutsches Elektronen-Synchrotron (DESY), EMBL Hamburg, 22607 Hamburg, Germany
| | | | - Anna Cyrklaff
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, 69117 Heidelberg, Germany
| | - Vaishali
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, 69117 Heidelberg, Germany.,Faculty of Biosciences, Heidelberg University, 69120 Heidelberg, Germany
| | - Karine Lapouge
- Protein Expression and Purification Core Facility, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Peter Sehr
- Chemical Biology Core Facility, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Kathryn Perez
- Protein Expression and Purification Core Facility, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Simone Heber
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, 69117 Heidelberg, Germany
| | - Christian Löw
- Centre for Structural Systems Biology (CSSB), Deutsches Elektronen-Synchrotron (DESY), EMBL Hamburg, 22607 Hamburg, Germany
| | - Janosch Hennig
- Structural and Computational Biology Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL) Heidelberg, 69117 Heidelberg, Germany
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10
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Obrdlik A, Lin G, Haberman N, Ule J, Ephrussi A. The Transcriptome-wide Landscape and Modalities of EJC Binding in Adult Drosophila. Cell Rep 2020; 28:1219-1236.e11. [PMID: 31365866 DOI: 10.1016/j.celrep.2019.06.088] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 04/30/2019] [Accepted: 06/24/2019] [Indexed: 12/27/2022] Open
Abstract
Exon junction complex (EJC) assembles after splicing at specific positions upstream of exon-exon junctions in mRNAs of all higher eukaryotes, affecting major regulatory events. In mammalian cell cytoplasm, EJC is essential for efficient RNA surveillance, while in Drosophila, EJC is essential for localization of oskar mRNA. Here we developed a method for isolation of protein complexes and associated RNA targets (ipaRt) to explore the EJC RNA-binding landscape in a transcriptome-wide manner in adult Drosophila. We find the EJC at canonical positions, preferably on mRNAs from genes comprising multiple splice sites and long introns. Moreover, EJC occupancy is highest at junctions adjacent to strong splice sites, CG-rich hexamers, and RNA structures. Highly occupied mRNAs tend to be maternally localized and derive from genes involved in differentiation or development. These modalities, which have not been reported in mammals, specify EJC assembly on a biologically coherent set of transcripts in Drosophila.
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Affiliation(s)
- Ales Obrdlik
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| | - Gen Lin
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Nejc Haberman
- Department for Neuromuscular Diseases, UCL Institute of Neurology, London WC1N 3BG, UK
| | - Jernej Ule
- Department for Neuromuscular Diseases, UCL Institute of Neurology, London WC1N 3BG, UK; The Francis Crick Institute, London NW1 1AT, UK
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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11
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Abstract
The conserved RNA helicase Vasa is required for germ cell development in many organisms. In Drosophila melanogaster loss of PIWI-interacting RNA pathway components, including Vasa, causes Chk2-dependent oogenesis arrest. However, whether the arrest is due to Chk2 signaling at a specific stage and whether continuous Chk2 signaling is required for the arrest is unknown. Here, we show that absence of Vasa during the germarial stages causes Chk2-dependent oogenesis arrest. Additionally, we report the age-dependent decline of the ovariole number both in flies lacking Vasa expression only in the germarium and in loss-of-function vasa mutant flies. We show that Chk2 activation exclusively in the germarium is sufficient to interrupt oogenesis and to reduce ovariole number in aging flies. Once induced in the germarium, Chk2-mediated arrest of germ cell development cannot be overcome by restoration of Vasa or by downregulation of Chk2 in the arrested egg chambers. These findings, together with the identity of Vasa-associated proteins identified in this study, demonstrate an essential role of the helicase in the germ cell lineage maintenance and indicate a function of Vasa in germline stem cell homeostasis.
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Affiliation(s)
- Zeljko Durdevic
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg D-69117, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg D-69117, Germany
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12
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Hampoelz B, Schwarz A, Ronchi P, Bragulat-Teixidor H, Tischer C, Gaspar I, Ephrussi A, Schwab Y, Beck M. Nuclear Pores Assemble from Nucleoporin Condensates During Oogenesis. Cell 2019; 179:671-686.e17. [PMID: 31626769 PMCID: PMC6838685 DOI: 10.1016/j.cell.2019.09.022] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 08/09/2019] [Accepted: 09/20/2019] [Indexed: 02/02/2023]
Abstract
The molecular events that direct nuclear pore complex (NPC) assembly toward nuclear envelopes have been conceptualized in two pathways that occur during mitosis or interphase, respectively. In gametes and embryonic cells, NPCs also occur within stacked cytoplasmic membrane sheets, termed annulate lamellae (AL), which serve as NPC storage for early development. The mechanism of NPC biogenesis at cytoplasmic membranes remains unknown. Here, we show that during Drosophila oogenesis, Nucleoporins condense into different precursor granules that interact and progress into NPCs. Nup358 is a key player that condenses into NPC assembly platforms while its mRNA localizes to their surface in a translation-dependent manner. In concert, Microtubule-dependent transport, the small GTPase Ran and nuclear transport receptors regulate NPC biogenesis in oocytes. We delineate a non-canonical NPC assembly mechanism that relies on Nucleoporin condensates and occurs away from the nucleus under conditions of cell cycle arrest.
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Affiliation(s)
- Bernhard Hampoelz
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Heidelberg, Germany; Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
| | - Andre Schwarz
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Heidelberg, Germany; Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences
| | - Paolo Ronchi
- European Molecular Biology Laboratory, Electron Microscopy Core Facility, Heidelberg, Germany
| | | | - Christian Tischer
- Center for Bioimage Analysis, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Imre Gaspar
- European Molecular Biology Laboratory, Developmental Biology Unit, Heidelberg, Germany
| | - Anne Ephrussi
- European Molecular Biology Laboratory, Developmental Biology Unit, Heidelberg, Germany
| | - Yannick Schwab
- European Molecular Biology Laboratory, Electron Microscopy Core Facility, Heidelberg, Germany; European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Martin Beck
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Heidelberg, Germany; Max Planck Institute of Biophysics, Frankfurt am Main, Germany; European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany.
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13
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Wippich F, Ephrussi A. Transcript specific mRNP capture from Drosophila egg-chambers for proteomic analysis. Methods 2019; 178:83-88. [PMID: 31493515 DOI: 10.1016/j.ymeth.2019.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 09/02/2019] [Accepted: 09/02/2019] [Indexed: 01/23/2023] Open
Abstract
mRNA binding proteins (RBPs) play a major role in post-transcriptional control of gene expression. To understand the complex regulatory processes regulating a specific mRNA during its life-time, a comprehensive view of the bound RBPs is essential. Here, we describe a method for transcript-specific isolation of endogenous ribonucleoprotein complexes (RNPs) from Drosophila egg-chambers. The method, which is based on in-solution hybridization of short biotinylated antisense DNA oligonucleotide probes to multiple segments of a transcript of interest allows unbiased identification of associated proteins by quantitative proteomics.
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Affiliation(s)
- Frank Wippich
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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14
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Heber S, Gáspár I, Tants JN, Günther J, Moya SMF, Janowski R, Ephrussi A, Sattler M, Niessing D. Staufen2-mediated RNA recognition and localization requires combinatorial action of multiple domains. Nat Commun 2019; 10:1659. [PMID: 30971701 PMCID: PMC6477676 DOI: 10.1038/s41467-019-09655-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 03/20/2019] [Indexed: 11/08/2022] Open
Abstract
Throughout metazoans, Staufen (Stau) proteins are core factors of mRNA localization particles. They consist of three to four double-stranded RNA binding domains (dsRBDs) and a C-terminal dsRBD-like domain. Mouse Staufen2 (mStau2)-like Drosophila Stau (dmStau) contains four dsRBDs. Existing data suggest that only dsRBDs 3-4 are necessary and sufficient for mRNA binding. Here, we show that dsRBDs 1 and 2 of mStau2 bind RNA with similar affinities and kinetics as dsRBDs 3 and 4. While RNA binding by these tandem domains is transient, all four dsRBDs recognize their target RNAs with high stability. Rescue experiments in Drosophila oocytes demonstrate that mStau2 partially rescues dmStau-dependent mRNA localization. In contrast, a rescue with mStau2 bearing RNA-binding mutations in dsRBD1-2 fails, confirming the physiological relevance of our findings. In summary, our data show that the dsRBDs 1-2 play essential roles in the mRNA recognition and function of Stau-family proteins of different species.
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Affiliation(s)
- Simone Heber
- Institute of Pharmaceutical Biotechnology, 89081 Ulm University, Ulm, Germany
- Institute of Structural Biology, Helmholtz Zentrum München, 85764, Neuherberg, Germany
| | - Imre Gáspár
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Institute of Molecular Biotechnology, 1030, Vienna, Austria
| | - Jan-Niklas Tants
- Center for Integrated Protein Science Munich at Chair of Biomolecular NMR Spectroscopy, Department Chemistry, Technische Universität München, 85747, Garching, Germany
| | - Johannes Günther
- Center for Integrated Protein Science Munich at Chair of Biomolecular NMR Spectroscopy, Department Chemistry, Technische Universität München, 85747, Garching, Germany
| | - Sandra M Fernandez Moya
- Biomedical Center Munich, Department of Cell Biology, Ludwig-Maximilians-Universität München, 82152, Planegg-Martinsried, Germany
| | - Robert Janowski
- Institute of Structural Biology, Helmholtz Zentrum München, 85764, Neuherberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München, 85764, Neuherberg, Germany
- Center for Integrated Protein Science Munich at Chair of Biomolecular NMR Spectroscopy, Department Chemistry, Technische Universität München, 85747, Garching, Germany
| | - Dierk Niessing
- Institute of Pharmaceutical Biotechnology, 89081 Ulm University, Ulm, Germany.
- Institute of Structural Biology, Helmholtz Zentrum München, 85764, Neuherberg, Germany.
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15
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Durdevic Z, Pillai RS, Ephrussi A. Transposon silencing in the Drosophila female germline is essential for genome stability in progeny embryos. Life Sci Alliance 2018; 1:e201800179. [PMID: 30456388 PMCID: PMC6238532 DOI: 10.26508/lsa.201800179] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 09/04/2018] [Accepted: 09/05/2018] [Indexed: 12/21/2022] Open
Abstract
The Piwi-interacting RNA pathway functions in transposon control in the germline of metazoans. The conserved RNA helicase Vasa is an essential Piwi-interacting RNA pathway component, but has additional important developmental functions. Here, we address the importance of Vasa-dependent transposon control in the Drosophila female germline and early embryos. We find that transient loss of vasa expression during early oogenesis leads to transposon up-regulation in supporting nurse cells of the fly egg-chamber. We show that elevated transposon levels have dramatic consequences, as de-repressed transposons accumulate in the oocyte where they cause DNA damage. We find that suppression of Chk2-mediated DNA damage signaling in vasa mutant females restores oogenesis and egg production. Damaged DNA and up-regulated transposons are transmitted from the mother to the embryos, which sustain severe nuclear defects and arrest development. Our findings reveal that the Vasa-dependent protection against selfish genetic elements in the nuage of nurse cell is essential to prevent DNA damage-induced arrest of embryonic development.
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Affiliation(s)
- Zeljko Durdevic
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Ramesh S Pillai
- Department of Molecular Biology, University of Geneva, Geneva, Switzerland
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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16
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Gaspar I, Hövelmann F, Chamiolo J, Ephrussi A, Seitz O. Quantitative mRNA Imaging with Dual Channel qFIT Probes to Monitor Distribution and Degree of Hybridization. ACS Chem Biol 2018; 13:742-749. [PMID: 29378392 DOI: 10.1021/acschembio.7b01007] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Fluorogenic oligonucleotide probes facilitate the detection and localization of RNA targets within cells. However, quantitative measurements of mRNA abundance are difficult when fluorescence signaling is based on intensity changes because a high concentration of unbound probes cannot be distinguished from a low concentration of target-bound probes. Here, we introduce qFIT (quantitative forced intercalation) probes that allow the detection both of probe-target complexes and of unbound probes on separate, independent channels. A surrogate nucleobase based on thiazole orange (TO) probes the hybridization status. The second channel involves a nonresponsive near-IR dye, which serves as a reporter of concentration. We show that the undesirable perturbation of the hybridization reporter TO is avoided when the near-IR dye Cy7 is connected by means of short triazole linkages in an ≥18 nucleotides distance. We used the qFIT probes to localize and quantify oskar mRNA in fixed egg chambers of wild-type and mutant Drosophila melanogaster by wash-free fluorescence in situ hybridization. The measurements revealed a relative 400-fold enrichment of oskar within a 3000 μm3 large volume at the posterior pole of stage 8-9 oocytes, which peaked at a remarkably high 1.8 μM local concentration inside 0.075 μm3 volume units. We discuss detection limits and show that the number of oskar mRNA molecules per oocyte is independent of the oocyte size, which suggests that the final levels are attained already during the onset of oskar localization at stage 8.
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Affiliation(s)
- Imre Gaspar
- European Molecular Biology Laboratory (EMBL) Heidelberg, 69117 Heidelberg, Germany
| | - Felix Hövelmann
- Institut für Chemie der Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Jasmine Chamiolo
- Institut für Chemie der Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Anne Ephrussi
- European Molecular Biology Laboratory (EMBL) Heidelberg, 69117 Heidelberg, Germany
| | - Oliver Seitz
- Institut für Chemie der Humboldt-Universität zu Berlin, 12489 Berlin, Germany
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17
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Gaspar I, Wippich F, Ephrussi A. Terminal Deoxynucleotidyl Transferase Mediated Production of Labeled Probes for Single-molecule FISH or RNA Capture. Bio Protoc 2018; 8:e2750. [PMID: 34179277 DOI: 10.21769/bioprotoc.2750] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 02/14/2018] [Accepted: 02/26/2018] [Indexed: 11/02/2022] Open
Abstract
Arrays of short, singly-labeled ssDNA oligonucleotides enable in situ hybridization with single molecule sensitivity and efficient transcript specific RNA capture. Here, we describe a simple, enzymatic protocol that can be carried out using basic laboratory equipment to convert arrays of PCR oligos into smFISH and RAP probesets in a quantitative, cost-efficient and flexible way.
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Affiliation(s)
- Imre Gaspar
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Meyerhofstrasse 1, 69117 Germany
| | - Frank Wippich
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Meyerhofstrasse 1, 69117 Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Meyerhofstrasse 1, 69117 Germany
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18
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Gaspar I, Wippich F, Ephrussi A. Enzymatic production of single-molecule FISH and RNA capture probes. RNA 2017; 23:1582-1591. [PMID: 28698239 PMCID: PMC5602115 DOI: 10.1261/rna.061184.117] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Accepted: 06/22/2017] [Indexed: 05/20/2023]
Abstract
Arrays of singly labeled short oligonucleotides that hybridize to a specific target revolutionized RNA biology, enabling quantitative, single-molecule microscopy analysis and high-efficiency RNA/RNP capture. Here, we describe a simple and efficient method that allows flexible functionalization of inexpensive DNA oligonucleotides by different fluorescent dyes or biotin using terminal deoxynucleotidyl transferase and custom-made functional group conjugated dideoxy-UTP. We show that (i) all steps of the oligonucleotide labeling-including conjugation, enzymatic synthesis, and product purification-can be performed in a standard biology laboratory, (ii) the process yields >90%, often >95% labeled product with minimal carryover of impurities, and (iii) the oligonucleotides can be labeled with different dyes or biotin, allowing single-molecule FISH, RNA affinity purification, and Northern blot analysis to be performed.
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Affiliation(s)
- Imre Gaspar
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg 69117, Germany
| | - Frank Wippich
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg 69117, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg 69117, Germany
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19
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Abstract
RNAs of the protein synthesis machinery relocalize to enhance the response to nutrients
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Affiliation(s)
- Imre Gáspár
- Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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20
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Ephrussi A. Assembly and transport of oskar mRNPs in the Drosophila oocyte. Mech Dev 2017. [DOI: 10.1016/j.mod.2017.04.529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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21
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Jeske M, Müller CW, Ephrussi A. The LOTUS domain is a conserved DEAD-box RNA helicase regulator essential for the recruitment of Vasa to the germ plasm and nuage. Genes Dev 2017; 31:939-952. [PMID: 28536148 PMCID: PMC5458760 DOI: 10.1101/gad.297051.117] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 05/08/2017] [Indexed: 12/15/2022]
Abstract
DEAD-box RNA helicases play important roles in a wide range of metabolic processes. Regulatory proteins can stimulate or block the activity of DEAD-box helicases. Here, we show that LOTUS (Limkain, Oskar, and Tudor containing proteins 5 and 7) domains present in the germline proteins Oskar, TDRD5 (Tudor domain-containing 5), and TDRD7 bind and stimulate the germline-specific DEAD-box RNA helicase Vasa. Our crystal structure of the LOTUS domain of Oskar in complex with the C-terminal RecA-like domain of Vasa reveals that the LOTUS domain occupies a surface on a DEAD-box helicase not implicated previously in the regulation of the enzyme's activity. We show that, in vivo, the localization of Drosophila Vasa to the nuage and germ plasm depends on its interaction with LOTUS domain proteins. The binding and stimulation of Vasa DEAD-box helicases by LOTUS domains are widely conserved.
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Affiliation(s)
- Mandy Jeske
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Christoph W Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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22
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Abstract
Understanding the dynamic behavior and the continuously changing composition of macromolecular complexes, subcellular structures and organelles is one of areas of active research in both cell and developmental biology, as these changes directly relate to function and subsequently to the development and homeostasis of the organism. Here, we demonstrate the use of the developing Drosophila oocyte to study dynamics of messenger ribonucleoprotein complexes (mRNPs) with high spatiotemporal resolution. The combination of Drosophila genetics with total internal reflection (TIRF) microscopy, image processing and data analysis gives insight into mRNP motility and composition dynamics with unprecedented precision.
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Affiliation(s)
- Imre Gaspar
- European Molecular Biology Laboratory (EMBL), Developmental Biology Unit, Heidelberg, Meyerhofstrasse 1, D-69117, Germany
| | - Anne Ephrussi
- European Molecular Biology Laboratory (EMBL), Developmental Biology Unit, Heidelberg, Meyerhofstrasse 1, D-69117, Germany
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23
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Gáspár I, Sysoev V, Komissarov A, Ephrussi A. An RNA-binding atypical tropomyosin recruits kinesin-1 dynamically to oskar mRNPs. EMBO J 2016; 36:319-333. [PMID: 28028052 PMCID: PMC5286366 DOI: 10.15252/embj.201696038] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 11/28/2016] [Accepted: 11/29/2016] [Indexed: 11/14/2022] Open
Abstract
Localization and local translation of oskar mRNA at the posterior pole of the Drosophila oocyte directs abdominal patterning and germline formation in the embryo. The process requires recruitment and precise regulation of motor proteins to form transport‐competent mRNPs. We show that the posterior‐targeting kinesin‐1 is loaded upon nuclear export of oskar mRNPs, prior to their dynein‐dependent transport from the nurse cells into the oocyte. We demonstrate that kinesin‐1 recruitment requires the DmTropomyosin1‐I/C isoform, an atypical RNA‐binding tropomyosin that binds directly to dimerizing oskar 3′UTRs. Finally, we show that a small but dynamically changing subset of oskar mRNPs gets loaded with inactive kinesin‐1 and that the motor is activated during mid‐oogenesis by the functionalized spliced oskar RNA localization element. This inefficient, dynamic recruitment of Khc decoupled from cargo‐dependent motor activation constitutes an optimized, coordinated mechanism of mRNP transport, by minimizing interference with other cargo‐transport processes and between the cargo‐associated dynein and kinesin‐1.
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Affiliation(s)
- Imre Gáspár
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Vasiliy Sysoev
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Artem Komissarov
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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24
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Abstract
RNAs are known to regulate diverse biological processes, either as protein-encoding molecules or as non-coding RNAs. However, a third class that comprises RNAs endowed with both protein coding and non-coding functions has recently emerged. Such bi-functional 'coding and non-coding RNAs' (cncRNAs) have been shown to play important roles in distinct developmental processes in plants and animals. Here, we discuss key examples of cncRNAs and review their roles, regulation and mechanisms of action during development.
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Affiliation(s)
- Karuna Sampath
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AJ, UK
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, Heidelberg 69117, Germany
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25
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Sysoev VO, Fischer B, Frese CK, Gupta I, Krijgsveld J, Hentze MW, Castello A, Ephrussi A. Global changes of the RNA-bound proteome during the maternal-to-zygotic transition in Drosophila. Nat Commun 2016; 7:12128. [PMID: 27378189 PMCID: PMC4935972 DOI: 10.1038/ncomms12128] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 06/03/2016] [Indexed: 12/15/2022] Open
Abstract
The maternal-to-zygotic transition (MZT) is a process that occurs in animal embryos at the earliest developmental stages, during which maternally deposited mRNAs and other molecules are degraded and replaced by products of the zygotic genome. The zygotic genome is not activated immediately upon fertilization, and in the pre-MZT embryo post-transcriptional control by RNA-binding proteins (RBPs) orchestrates the first steps of development. To identify relevant Drosophila RBPs organism-wide, we refined the RNA interactome capture method for comparative analysis of the pre- and post-MZT embryos. We determine 523 proteins as high-confidence RBPs, half of which were not previously reported to bind RNA. Comparison of the RNA interactomes of pre- and post-MZT embryos reveals high dynamicity of the RNA-bound proteome during early development, and suggests active regulation of RNA binding of some RBPs. This resource provides unprecedented insight into the system of RBPs that govern the earliest steps of Drosophila development.
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Affiliation(s)
- Vasiliy O. Sysoev
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Bernd Fischer
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
- German Cancer Research Center, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany
| | - Christian K. Frese
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Ishaan Gupta
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Jeroen Krijgsveld
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Matthias W. Hentze
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Alfredo Castello
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, England
| | - Anne Ephrussi
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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26
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Halstead JM, Wilbertz JH, Wippich F, Lionnet T, Ephrussi A, Chao JA. TRICK: A Single-Molecule Method for Imaging the First Round of Translation in Living Cells and Animals. Methods Enzymol 2016; 572:123-57. [PMID: 27241753 DOI: 10.1016/bs.mie.2016.02.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
The life of an mRNA is dynamic within a cell. The development of quantitative fluorescent microscopy techniques to image single molecules of RNA has allowed many aspects of the mRNA lifecycle to be directly observed in living cells. Recent advances in live-cell multicolor RNA imaging, however, have now made it possible to investigate RNA metabolism in greater detail. In this chapter, we present an overview of the design and implementation of the translating RNA imaging by coat protein knockoff RNA biosensor, which allows untranslated mRNAs to be distinguished from ones that have undergone a round of translation. The methods required for establishing this system in mammalian cell lines and Drosophila melanogaster oocytes are described here, but the principles may be applied to any experimental system.
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Affiliation(s)
- J M Halstead
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - J H Wilbertz
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - F Wippich
- European Molecular Biology Laboratory, Heidelberg, Germany
| | - T Lionnet
- Transcription Imaging Consortium, HHMI Janelia Research Campus, Ashburn, VA, United States
| | - A Ephrussi
- European Molecular Biology Laboratory, Heidelberg, Germany
| | - J A Chao
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
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27
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Hövelmann F, Gaspar I, Chamiolo J, Kasper M, Steffen J, Ephrussi A, Seitz O. LNA-enhanced DNA FIT-probes for multicolour RNA imaging. Chem Sci 2016; 7:128-135. [PMID: 29861973 PMCID: PMC5950760 DOI: 10.1039/c5sc03053f] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 11/01/2015] [Indexed: 01/04/2023] Open
Abstract
The simultaneous imaging of different RNA molecules in homogeneous solution is a challenge and requires optimisation to enable unambiguous staining of intracellular RNA targets. Our approach relies on single dye forced intercalation (FIT) probes, in which a visco-sensitive reporter of the thiazole orange (TO) family serves as a surrogate nucleobase and provides enhancements of fluorescence upon hybridisation. Previous FIT probes spanned the cyan and green emission range. Herein, we report for the first time chromophores for FIT probes that emit in the red range (above 600 nm). Such probes are valuable to overcome cellular auto-fluorescent background and enable multiplexed detection. In order to find suitable chromophores, we developed a submonomer approach that facilitated the rapid analysis of different TO family dyes in varied sequence positions. A carboxymethylated 4,4'-methine linked cyanine, which we named quinoline blue (QB), provided exceptional response characteristics at the 605 nm emission maximum. Exceeding previously reported base surrogates, the emission of the QB nucleotide intensified by up to 195-fold upon binding of complementary RNA. Owing to large extinction coefficients and quantum yields (up to ε = 129.000 L mol-1 cm-1 and Φ = 0.47, respectively) QB-FIT probes enable imaging of intracellular mRNA. A mixture of BO-, TO- and QB-containing FIT probes allowed the simultaneous detection of three different RNA targets in homogenous solution. TO- and QB-FIT probes were used to localize oskar mRNA and other polyadenylated mRNA molecules in developing oocytes from Drosphila melanogaster by means of wash-free fluorescent in situ hybridisation and super resolution microscopy (STED).
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Affiliation(s)
- F Hövelmann
- Department of Chemistry , Humboldt University Berlin , Brook-Taylor-Str. 2 , D-12489 Berlin , Germany .
- European Molecular Biology Laboratory (EMBL) Heidelberg , Meyerhofstr. 1 , 69117 Heidelberg , Germany
| | - I Gaspar
- European Molecular Biology Laboratory (EMBL) Heidelberg , Meyerhofstr. 1 , 69117 Heidelberg , Germany
| | - J Chamiolo
- Department of Chemistry , Humboldt University Berlin , Brook-Taylor-Str. 2 , D-12489 Berlin , Germany .
| | - M Kasper
- Department of Chemistry , Humboldt University Berlin , Brook-Taylor-Str. 2 , D-12489 Berlin , Germany .
| | - J Steffen
- Department of Chemistry , Humboldt University Berlin , Brook-Taylor-Str. 2 , D-12489 Berlin , Germany .
| | - A Ephrussi
- European Molecular Biology Laboratory (EMBL) Heidelberg , Meyerhofstr. 1 , 69117 Heidelberg , Germany
| | - O Seitz
- Department of Chemistry , Humboldt University Berlin , Brook-Taylor-Str. 2 , D-12489 Berlin , Germany .
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28
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Abstract
mRNA localization by active transport is a regulated process that requires association of mRNPs with protein motors for transport along either the microtubule or the actin cytoskeleton. oskar mRNA localization at the posterior pole of the Drosophila oocyte requires a specific mRNA sequence, termed the SOLE, which comprises nucleotides of both exon 1 and exon 2 and is assembled upon splicing. The SOLE folds into a stem-loop structure. Both SOLE RNA and the exon junction complex (EJC) are required for oskar mRNA transport along the microtubules by kinesin. The SOLE RNA likely constitutes a recognition element for a yet unknown protein, which either belongs to the EJC or functions as a bridge between the EJC and the mRNA. Here, we determine the solution structure of the SOLE RNA by Nuclear Magnetic Resonance spectroscopy. We show that the SOLE forms a continuous helical structure, including a few noncanonical base pairs, capped by a pentanucleotide loop. The helix displays a widened major groove, which could accommodate a protein partner. In addition, the apical helical segment undergoes complex dynamics, with potential functional significance.
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Affiliation(s)
- Bernd Simon
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany
| | - Pawel Masiewicz
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany
| | - Teresa Carlomagno
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany Helmholtz Zentrum für Infektionsforschung, Braunschweig, D-38124, Germany
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29
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Simon B, Masiewicz P, Ephrussi A, Carlomagno T. The structure of the SOLE element of oskar mRNA. RNA 2015; 21:1444-1453. [PMID: 26089324 DOI: 10.1261/rna.049601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/29/2015] [Indexed: 05/23/2023]
Abstract
mRNA localization by active transport is a regulated process that requires association of mRNPs with protein motors for transport along either the microtubule or the actin cytoskeleton. oskar mRNA localization at the posterior pole of the Drosophila oocyte requires a specific mRNA sequence, termed the SOLE, which comprises nucleotides of both exon 1 and exon 2 and is assembled upon splicing. The SOLE folds into a stem-loop structure. Both SOLE RNA and the exon junction complex (EJC) are required for oskar mRNA transport along the microtubules by kinesin. The SOLE RNA likely constitutes a recognition element for a yet unknown protein, which either belongs to the EJC or functions as a bridge between the EJC and the mRNA. Here, we determine the solution structure of the SOLE RNA by Nuclear Magnetic Resonance spectroscopy. We show that the SOLE forms a continuous helical structure, including a few noncanonical base pairs, capped by a pentanucleotide loop. The helix displays a widened major groove, which could accommodate a protein partner. In addition, the apical helical segment undergoes complex dynamics, with potential functional significance.
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Affiliation(s)
- Bernd Simon
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany
| | - Pawel Masiewicz
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany
| | - Teresa Carlomagno
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, D-69117, Germany Helmholtz Zentrum für Infektionsforschung, Braunschweig, D-38124, Germany
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Jeske M, Bordi M, Glatt S, Müller S, Rybin V, Müller CW, Ephrussi A. The Crystal Structure of the Drosophila Germline Inducer Oskar Identifies Two Domains with Distinct Vasa Helicase- and RNA-Binding Activities. Cell Rep 2015; 12:587-98. [PMID: 26190108 DOI: 10.1016/j.celrep.2015.06.055] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 05/25/2015] [Accepted: 06/15/2015] [Indexed: 12/31/2022] Open
Abstract
In many animals, the germ plasm segregates germline from soma during early development. Oskar protein is known for its ability to induce germ plasm formation and germ cells in Drosophila. However, the molecular basis of germ plasm formation remains unclear. Here, we show that Oskar is an RNA-binding protein in vivo, crosslinking to nanos, polar granule component, and germ cell-less mRNAs, each of which has a role in germline formation. Furthermore, we present high-resolution crystal structures of the two Oskar domains. RNA-binding maps in vitro to the C-terminal domain, which shows structural similarity to SGNH hydrolases. The highly conserved N-terminal LOTUS domain forms dimers and mediates Oskar interaction with the germline-specific RNA helicase Vasa in vitro. Our findings suggest a dual function of Oskar in RNA and Vasa binding, providing molecular clues to its germ plasm function.
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Affiliation(s)
- Mandy Jeske
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Matteo Bordi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sebastian Glatt
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sandra Müller
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Vladimir Rybin
- Protein Expression and Purification Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Christoph W Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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31
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Kanke M, Jambor H, Reich J, Marches B, Gstir R, Ryu YH, Ephrussi A, Macdonald PM. oskar RNA plays multiple noncoding roles to support oogenesis and maintain integrity of the germline/soma distinction. RNA 2015; 21:1096-109. [PMID: 25862242 PMCID: PMC4436663 DOI: 10.1261/rna.048298.114] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 02/12/2015] [Indexed: 05/05/2023]
Abstract
The Drosophila oskar (osk) mRNA is unusual in that it has both coding and noncoding functions. As an mRNA, osk encodes a protein required for embryonic patterning and germ cell formation. Independent of that function, the absence of osk mRNA disrupts formation of the karyosome and blocks progression through oogenesis. Here we show that loss of osk mRNA also affects the distribution of regulatory proteins, relaxing their association with large RNPs within the germline, and allowing them to accumulate in the somatic follicle cells. This and other noncoding functions of the osk mRNA are mediated by multiple sequence elements with distinct roles. One role, provided by numerous binding sites in two distinct regions of the osk 3' UTR, is to sequester the translational regulator Bruno (Bru), which itself controls translation of osk mRNA. This defines a novel regulatory circuit, with Bru restricting the activity of osk, and osk in turn restricting the activity of Bru. Other functional elements, which do not bind Bru and are positioned close to the 3' end of the RNA, act in the oocyte and are essential. Despite the different roles played by the different types of elements contributing to RNA function, mutation of any leads to accumulation of the germline regulatory factors in the follicle cells.
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Affiliation(s)
- Matt Kanke
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Helena Jambor
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - John Reich
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Brittany Marches
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Ronald Gstir
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Young Hee Ryu
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Paul M Macdonald
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
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32
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Halstead JM, Lionnet T, Wilbertz JH, Wippich F, Ephrussi A, Singer RH, Chao JA. Translation. An RNA biosensor for imaging the first round of translation from single cells to living animals. Science 2015; 347:1367-671. [PMID: 25792328 DOI: 10.1126/science.aaa3380] [Citation(s) in RCA: 196] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Analysis of single molecules in living cells has provided quantitative insights into the kinetics of fundamental biological processes; however, the dynamics of messenger RNA (mRNA) translation have yet to be addressed. We have developed a fluorescence microscopy technique that reports on the first translation events of individual mRNA molecules. This allowed us to examine the spatiotemporal regulation of translation during normal growth and stress and during Drosophila oocyte development. We have shown that mRNAs are not translated in the nucleus but translate within minutes after export, that sequestration within P-bodies regulates translation, and that oskar mRNA is not translated until it reaches the posterior pole of the oocyte. This methodology provides a framework for studying initiation of protein synthesis on single mRNAs in living cells.
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Affiliation(s)
- James M Halstead
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Timothée Lionnet
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Transcription Imaging Consortium, Howard Hughes Medical Institute Janelia Farm Research Campus, Ashburn, VA 20147, USA
| | - Johannes H Wilbertz
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland. University of Basel, CH-4003 Basel, Switzerland
| | - Frank Wippich
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| | - Robert H Singer
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Transcription Imaging Consortium, Howard Hughes Medical Institute Janelia Farm Research Campus, Ashburn, VA 20147, USA.
| | - Jeffrey A Chao
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland. Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Abstract
Axonal transport is essential for the initial growth, maintenance and synaptic plasticity of axons, and altered axonal transport has been observed in different models of neurodegenerative pathologies. Dissecting the mechanisms underlying axonal transport in developing or degenerating brains requires dynamic imaging of axonal cargo movement in living samples. Whereas methods exist to image axonal transport in Drosophila larval neurons, they are not suitable to follow this process during metamorphosis, when brains undergo extensive remodeling. Here we present a simple method that enables confocal imaging of both fast and slow axonal transport in Drosophila pupal brain explants. We describe how to prepare chambers adapted for live imaging, how to maintain brain explants under physiological conditions and how to monitor and quantitatively analyze the movement of fluorescently labeled cargoes. This protocol requires minimal equipment and is ideally suited for experiments that combine genetics, optogenetics and pharmacological approaches. The brains can be prepared for image acquisition in 1.5 h, and the protocol can be performed easily in any fly laboratory.
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Affiliation(s)
- Caroline Medioni
- Institute of Biology Valrose, Centre National de la Recherche Scientifique (CNRS)-Unité Mixte de Recherche (UMR) 7277, Institut National de la Santé et de la Recherche Médicale (INSERM)-UMR1091, University of Nice-Sophia Antipolis, Nice, France
| | | | - Florence Besse
- Institute of Biology Valrose, Centre National de la Recherche Scientifique (CNRS)-Unité Mixte de Recherche (UMR) 7277, Institut National de la Santé et de la Recherche Médicale (INSERM)-UMR1091, University of Nice-Sophia Antipolis, Nice, France
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Gaspar I, Ephrussi A. Strength in numbers: quantitative single-molecule RNA detection assays. Wiley Interdiscip Rev Dev Biol 2015; 4:135-50. [PMID: 25645249 PMCID: PMC5024021 DOI: 10.1002/wdev.170] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 12/02/2014] [Indexed: 01/19/2023]
Abstract
Gene expression is a fundamental process that underlies development, homeostasis, and behavior of organisms. The fact that it relies on nucleic acid intermediates, which can specifically interact with complementary probes, provides an excellent opportunity for studying the multiple steps—transcription, RNA processing, transport, translation, degradation, and so forth—through which gene function manifests. Over the past three decades, the toolbox of nucleic acid science has expanded tremendously, making high‐precision in situ detection of DNA and RNA possible. This has revealed that many—probably the vast majority of—transcripts are distributed within the cytoplasm or the nucleus in a nonrandom fashion. With the development of microscopy techniques we have learned not only about the qualitative localization of these molecules but also about their absolute numbers with great precision. Single‐molecule techniques for nucleic acid detection have been transforming our views of biology with elementary power: cells are not average members of their population but are highly distinct individuals with greatly and suddenly changing gene expression, and this behavior of theirs can be measured, modeled, and thus predicted and, finally, comprehended. WIREs Dev Biol 2015, 4:135–150. doi: 10.1002/wdev.170 For further resources related to this article, please visit the
WIREs website. Conflict of interest: The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- Imre Gaspar
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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Gaspar I, Yu YV, Cotton SL, Kim DH, Ephrussi A, Welte MA. Klar ensures thermal robustness of oskar localization by restraining RNP motility. ACTA ACUST UNITED AC 2014; 206:199-215. [PMID: 25049271 PMCID: PMC4107779 DOI: 10.1083/jcb.201310010] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
When temperature fluctuation threatens the fidelity of Drosophila oogenesis, Klar restrains posterior-ward translocation of oskar mRNA, thereby adapting the rate of oskar delivery to the capacity of the anchoring machinery. Communication usually applies feedback loop–based filters and amplifiers to ensure undistorted delivery of messages. Such an amplifier acts during Drosophila melanogaster midoogenesis, when oskar messenger ribonucleic acid (mRNA) anchoring depends on its own locally translated protein product. We find that the motor regulator Klar β mediates a gain-control process that prevents saturation-based distortions in this positive feedback loop. We demonstrate that, like oskar mRNA, Klar β localizes to the posterior pole of oocytes in a kinesin-1–dependent manner. By live imaging and semiquantitative fluorescent in situ hybridization, we show that Klar β restrains oskar ribonucleoprotein motility and decreases the posterior-ward translocation of oskar mRNA, thereby adapting the rate of oskar delivery to the output of the anchoring machinery. This negative regulatory effect of Klar is particularly important for overriding temperature-induced changes in motility. We conclude that by preventing defects in oskar anchoring, this mechanism contributes to the developmental robustness of a poikilothermic organism living in a variable temperature environment.
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Affiliation(s)
- Imre Gaspar
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Yanxun V Yu
- Department of Biology, University of Rochester, Rochester, NY 14627
| | - Sean L Cotton
- Department of Biology, Brandeis University, Waltham, MA 02454
| | - Dae-Hwan Kim
- Department of Biology, Brandeis University, Waltham, MA 02454
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Michael A Welte
- Department of Biology, University of Rochester, Rochester, NY 14627 Department of Biology, Brandeis University, Waltham, MA 02454
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Hövelmann F, Gaspar I, Loibl S, Ermilov EA, Röder B, Wengel J, Ephrussi A, Seitz O. Brightness through local constraint--LNA-enhanced FIT hybridization probes for in vivo ribonucleotide particle tracking. Angew Chem Int Ed Engl 2014; 53:11370-5. [PMID: 25167966 DOI: 10.1002/anie.201406022] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Indexed: 11/11/2022]
Abstract
Imaging the dynamics of RNA in living cells is usually performed by means of transgenic approaches that require modification of RNA targets and cells. Fluorogenic hybridization probes would also allow the analysis of wild-type organisms. We developed nuclease-resistant DNA forced intercalation (FIT) probes that combine the high enhancement of fluorescence upon hybridization with the high brightness required to allow tracking of individual ribonucleotide particles (RNPs). In our design, a single thiazole orange (TO) intercalator dye is linked as a nucleobase surrogate and an adjacent locked nucleic acid (LNA) unit serves to introduce a local constraint. This closes fluorescence decay channels and thereby increases the brightness of the probe-target duplexes. As few as two probes were sufficient to enable the tracking of oskar mRNPs in wild-type living Drosophila melanogaster oocytes.
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Affiliation(s)
- Felix Hövelmann
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin (Germany)
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37
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Hövelmann F, Gaspar I, Loibl S, Ermilov EA, Röder B, Wengel J, Ephrussi A, Seitz O. Helligkeit durch lokale Rigidifizierung - LNA-verstärkte FIT-Sonden zur bildgebenden Darstellung von Ribonukleotidpartikeln in vivo. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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38
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Bassett AR, Akhtar A, Barlow DP, Bird AP, Brockdorff N, Duboule D, Ephrussi A, Ferguson-Smith AC, Gingeras TR, Haerty W, Higgs DR, Miska EA, Ponting CP. Considerations when investigating lncRNA function in vivo. eLife 2014; 3:e03058. [PMID: 25124674 PMCID: PMC4132285 DOI: 10.7554/elife.03058] [Citation(s) in RCA: 264] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Although a small number of the vast array of animal long non-coding RNAs (lncRNAs) have known effects on cellular processes examined in vitro, the extent of their contributions to normal cell processes throughout development, differentiation and disease for the most part remains less clear. Phenotypes arising from deletion of an entire genomic locus cannot be unequivocally attributed either to the loss of the lncRNA per se or to the associated loss of other overlapping DNA regulatory elements. The distinction between cis- or trans-effects is also often problematic. We discuss the advantages and challenges associated with the current techniques for studying the in vivo function of lncRNAs in the light of different models of lncRNA molecular mechanism, and reflect on the design of experiments to mutate lncRNA loci. These considerations should assist in the further investigation of these transcriptional products of the genome. DOI:http://dx.doi.org/10.7554/eLife.03058.001
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Affiliation(s)
- Andrew R Bassett
- Andrew R Bassett is in the MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom.
| | - Asifa Akhtar
- Asifa Akhtar is in the Department of Chromatin Regulation, Max-Planck-Institut für Immunbiologie und Epigenetik, Freiburg im Breisgau, Germany
| | - Denise P Barlow
- Denise P Barlow is in the CeMM, Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Adrian P Bird
- Adrian P Bird is in the Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Neil Brockdorff
- Neil Brockdorff is in the Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Denis Duboule
- Denis Duboule is in the School of Life Sciences, Ecole Polytechnique Fédérale Lausanne, Lausanne, Switzerland; Department of Genetics and Evolution, Université de Genève, Geneva, Switzerland
| | - Anne Ephrussi
- Anne Ephrussi is in the Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Anne C Ferguson-Smith
- Anne C Ferguson-Smith is in the Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Thomas R Gingeras
- Thomas R Gingeras is in the Functional Genomics Group, Cold Spring Harbor Laboratory, Cold Spring Harbor, United States
| | - Wilfried Haerty
- Wilfried Haerty is in the MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Douglas R Higgs
- Douglas R Higgs is in the MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, Oxford, United Kingdom
| | - Eric A Miska
- Eric A Miska is in the Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, United Kingdom; Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Chris P Ponting
- Chris P Ponting is in the MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom; Wellcome Trust Sanger Institute, Cambridge, United Kingdom
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Xiol J, Spinelli P, Laussmann MA, Homolka D, Yang Z, Cora E, Couté Y, Conn S, Kadlec J, Sachidanandam R, Kaksonen M, Cusack S, Ephrussi A, Pillai RS. RNA clamping by Vasa assembles a piRNA amplifier complex on transposon transcripts. Cell 2014; 157:1698-711. [PMID: 24910301 DOI: 10.1016/j.cell.2014.05.018] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 04/28/2014] [Accepted: 05/15/2014] [Indexed: 01/25/2023]
Abstract
Germline-specific Piwi-interacting RNAs (piRNAs) protect animal genomes against transposons and are essential for fertility. piRNAs targeting active transposons are amplified by the ping-pong cycle, which couples Piwi endonucleolytic slicing of target RNAs to biogenesis of new piRNAs. Here, we describe the identification of a transient Amplifier complex that mediates biogenesis of secondary piRNAs in insect cells. Amplifier is nucleated by the DEAD box RNA helicase Vasa and contains the two Piwi proteins participating in the ping-pong loop, the Tudor protein Qin/Kumo and antisense piRNA guides. These components assemble on the surface of Vasa's helicase domain, which functions as an RNA clamp to anchor Amplifier onto transposon transcripts. We show that ATP-dependent RNP remodeling by Vasa facilitates transfer of 5' sliced piRNA precursors between ping-pong partners, and loss of this activity causes sterility in Drosophila. Our results reveal the molecular basis for the small RNA amplification that confers adaptive immunity against transposons.
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Affiliation(s)
- Jordi Xiol
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Pietro Spinelli
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Maike A Laussmann
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Cell Biology and Biophysics Unit, EMBL, 69117 Heidelberg, Germany
| | - David Homolka
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Zhaolin Yang
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Elisa Cora
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Yohann Couté
- Laboratoire Biologie à Grande Echelle, IRTSV, CEA, 38054 Grenoble, France
| | - Simon Conn
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Jan Kadlec
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Ravi Sachidanandam
- Department of Oncological Sciences, Icahn School of Medicine at Sinai, New York, NY 10029, USA
| | - Marko Kaksonen
- Cell Biology and Biophysics Unit, EMBL, 69117 Heidelberg, Germany
| | - Stephen Cusack
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France
| | - Anne Ephrussi
- Developmental Biology Unit, EMBL, 69117 Heidelberg, Germany
| | - Ramesh S Pillai
- European Molecular Biology Laboratory, Grenoble Outstation, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France; Unit for Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, 71 avenue des Martyrs, 38042, France.
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Jambor H, Mueller S, Bullock SL, Ephrussi A. A stem-loop structure directs oskar mRNA to microtubule minus ends. RNA 2014; 20:429-39. [PMID: 24572808 PMCID: PMC3964905 DOI: 10.1261/rna.041566.113] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 01/06/2014] [Indexed: 05/22/2023]
Abstract
mRNA transport coupled with translational control underlies the intracellular localization of many proteins in eukaryotic cells. This is exemplified in Drosophila, where oskar mRNA transport and translation at the posterior pole of the oocyte direct posterior patterning of the embryo. oskar localization is a multistep process. Within the oocyte, a spliced oskar localization element (SOLE) targets oskar mRNA for plus end-directed transport by kinesin-1 to the posterior pole. However, the signals mediating the initial minus end-directed, dynein-dependent transport of the mRNA from nurse cells into the oocyte have remained unknown. Here, we show that a 67-nt stem-loop in the oskar 3' UTR promotes oskar mRNA delivery to the developing oocyte and that it shares functional features with the fs(1)K10 oocyte localization signal. Thus, two independent cis-acting signals, the oocyte entry signal (OES) and the SOLE, mediate sequential dynein- and kinesin-dependent phases of oskar mRNA transport during oogenesis. The OES also promotes apical localization of injected RNAs in blastoderm stage embryos, another dynein-mediated process. Similarly, when ectopically expressed in polarized cells of the follicular epithelium or salivary glands, reporter RNAs bearing the oskar OES are apically enriched, demonstrating that this element promotes mRNA localization independently of cell type. Our work sheds new light on how oskar mRNA is trafficked during oogenesis and the RNA features that mediate minus end-directed transport.
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Affiliation(s)
- Helena Jambor
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sandra Mueller
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Simon L. Bullock
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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41
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Medioni C, Ramialison M, Ephrussi A, Besse F. Imp promotes axonal remodeling by regulating profilin mRNA during brain development. Curr Biol 2014; 24:793-800. [PMID: 24656828 DOI: 10.1016/j.cub.2014.02.038] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 01/07/2014] [Accepted: 02/13/2014] [Indexed: 11/17/2022]
Abstract
Neuronal remodeling is essential for the refinement of neuronal circuits in response to developmental cues [1-4]. Although this process involves pruning or retraction of axonal projections followed by axonal regrowth and branching, how these steps are controlled is poorly understood. Drosophila mushroom body (MB) γ neurons provide a paradigm for the study of neuronal remodeling, as their larval axonal branches are pruned during metamorphosis and re-extend to form adult-specific branches [5]. Here, we identify the RNA binding protein Imp as a key regulator of axonal remodeling. Imp is the sole fly member of a conserved family of proteins that bind target mRNAs to promote their subcellular targeting [6-12]. We show that whereas Imp is dispensable for the initial growth of MB γ neuron axons, it is required for the regrowth and ramification of axonal branches that have undergone pruning. Furthermore, Imp is actively transported to axons undergoing developmental remodeling. Finally, we demonstrate that profilin mRNA is a direct and functional target of Imp that localizes to axons and controls axonal regrowth. Our study reveals that mRNA localization machineries are actively recruited to axons upon remodeling and suggests a role of mRNA transport in developmentally programmed rewiring of neuronal circuits during brain maturation.
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Affiliation(s)
- Caroline Medioni
- Institute of Biology Valrose, CNRS-UMR7277/INSERM-UMR1091, University of Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France
| | - Mirana Ramialison
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Florence Besse
- Institute of Biology Valrose, CNRS-UMR7277/INSERM-UMR1091, University of Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France; European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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Abstract
Fluorogenic oligonucleotides enable RNA imaging in cells and tissues. A high responsiveness of fluorescence is required when unbound probes cannot be washed away. Furthermore, emission should be bright in order to enable detection against autofluorescent background. The development of fluorescence-quenched hybridization probes has led to remarkable improvement of fluorescence responsiveness. Yet, comparably little attention has been paid to the brightness of smart probes. We describe hybridization probes that combine responsiveness with a high brightness of the measured signal. The method relies upon quencher-free DNA forced intercalation (FIT)-probes, in which two (or more) intercalator dyes of the thiazole orange (TO) family serve as nucleobase surrogates. Initial experiments on multi-TO-labeled probes led to improvements of responsiveness, but self-quenching limited their brightness. To enhance both brightness and responsiveness the highly responsive TO nucleoside was combined with the highly emissive oxazolopyridine analogue JO. Single-stranded TO/JO FIT-probes are dark. In the probe-target duplex, quenching caused by torsional twisting and dye-dye contact is prevented. The TO nucleoside appears to serve as a light collector that increases the extinction coefficient and transfers excitation energy to the JO emitter. This leads to very bright JO emission upon hybridization (F/F0 = 23, brightness = 43 mL mol(-1) cm(-1) at λex = 516 nm). TO/JO FIT-probes allowed the direct fluorescence microscopic imaging of oskar mRNA within a complex tissue. Of note, RNA imaging was feasible under wide-field excitation conditions. The described protocol enables rapid RNA imaging in tissue without the need for cutting-edge equipment, time-consuming washing, or signal amplification.
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Affiliation(s)
- Felix Hövelmann
- Institut für Chemie der Humboldt-Universität zu Berlin , 12489 Berlin, Germany
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43
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Abstract
Spindle assembly and chromosome segregation rely on a complex interplay of biochemical and mechanical processes. Analysis of this interplay requires precise manipulation of endogenous cellular components and high-resolution visualization. Here we provide a protocol for generating an extract from individual Drosophila syncytial embryos that supports repeated mitotic nuclear divisions with native characteristics. In contrast to the large-scale, metaphase-arrested Xenopus egg extract system, this assay enables the serial generation of extracts from single embryos of a genetically tractable organism, and each extract contains dozens of autonomously dividing nuclei that can be prepared and imaged within 60-90 min after embryo collection. We describe the microscopy setup and micropipette production that facilitate single-embryo manipulation, the preparation of embryos and the steps for making functional extracts that allow time-lapse microscopy of mitotic divisions ex vivo. The assay enables a unique combination of genetic, biochemical, optical and mechanical manipulations of the mitotic machinery.
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Affiliation(s)
- Ivo A Telley
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
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44
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Abstract
Polarity of the Drosophila oocyte is essential for correct development of the egg and future embryo. The Par proteins Par-6, aPKC and Bazooka are needed to maintain oocyte polarity and localize to specific domains early in oocyte development. To date, no upstream regulator or mechanism for localization of the Par proteins in the oocyte has been identified. We have analyzed the role of the small GTPase Cdc42 in oocyte polarity. We show that Cdc42 is required to maintain oocyte fate, which it achieves by mediating localization of Par proteins at distinct sites within this cell. We establish that Cdc42 localization itself is polarized to the anterolateral cortex of the oocyte and that Cdc42 is needed for maintenance of oocyte polarity throughout oogenesis. Our data show that Cdc42 ensures the integrity of the oocyte actin network and that disruption of this network with Latrunculin A phenocopies loss of Cdc42 or Par protein function in early stages of oogenesis. Finally, we show that Cdc42 and Par proteins, as well as Cdc42/Par and Arp3, interact in the context of oocyte polarity, and that loss of Par proteins reciprocally affects Cdc42 localization and the actin network. These results reveal a mutual dependence between Par proteins and Cdc42 for their localization, regulation of the actin cytoskeleton and, consequently, for the establishment of oocyte polarity. This most likely allows for the robustness in symmetry breaking in the cell.
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Affiliation(s)
- Andrea Leibfried
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sandra Müller
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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45
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Telley IA, Gáspár I, Ephrussi A, Surrey T. Aster migration determines the length scale of nuclear separation in the Drosophila syncytial embryo. J Cell Biol 2012; 197:887-95. [PMID: 22711698 PMCID: PMC3384421 DOI: 10.1083/jcb.201204019] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 05/24/2012] [Indexed: 11/22/2022] Open
Abstract
In the early embryo of many species, comparatively small spindles are positioned near the cell center for subsequent cytokinesis. In most insects, however, rapid nuclear divisions occur in the absence of cytokinesis, and nuclei distribute rapidly throughout the large syncytial embryo. Even distribution and anchoring of nuclei at the embryo cortex are crucial for cellularization of the blastoderm embryo. The principles underlying nuclear dispersal in a syncytium are unclear. We established a cell-free system from individual Drosophila melanogaster embryos that supports successive nuclear division cycles with native characteristics. This allowed us to investigate nuclear separation in predefined volumes. Encapsulating nuclei in microchambers revealed that the early cytoplasm is programmed to separate nuclei a distinct distance. Laser microsurgery revealed an important role of microtubule aster migration through cytoplasmic space, which depended on F-actin and cooperated with anaphase spindle elongation. These activities define a characteristic separation length scale that appears to be a conserved property of developing insect embryos.
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Affiliation(s)
- Ivo A Telley
- Cell Biology and Biophysics Unit and 2 Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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46
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Jambor H, Brunel C, Ephrussi A. Dimerization of oskar 3' UTRs promotes hitchhiking for RNA localization in the Drosophila oocyte. RNA 2011; 17:2049-2057. [PMID: 22028360 PMCID: PMC3222118 DOI: 10.1261/rna.2686411] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 08/23/2011] [Indexed: 05/29/2023]
Abstract
mRNA localization coupled with translational control is a highly conserved and widespread mechanism for restricting protein expression to specific sites within eukaryotic cells. In Drosophila, patterning of the embryo requires oskar mRNA transport to the posterior pole of the oocyte and translational repression prior to localization. oskar RNA splicing and the 3' untranslated region (UTR) are required for posterior enrichment of the mRNA. However, reporter RNAs harboring the oskar 3' UTR can localize by hitchhiking with endogenous oskar transcripts. Here we show that the oskar 3' UTR contains a stem-loop structure that promotes RNA dimerization in vitro and hitchhiking in vivo. Mutations in the loop that abolish in vitro dimerization interfere with reporter RNA localization, and restoring loop complementarity restores hitchhiking. Our analysis provides insight into the molecular basis of RNA hitchhiking, whereby localization-incompetent RNA molecules can become locally enriched in the cytoplasm, by virtue of their association with transport-competent RNAs.
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Affiliation(s)
- Helena Jambor
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Christine Brunel
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, 67084 Strasbourg Cedex, France
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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47
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Abstract
mRNA localization coupled with translational control is a widespread and conserved strategy that allows the localized production of proteins within eukaryotic cells. In Drosophila, oskar (osk) mRNA localization and translation at the posterior pole of the oocyte are essential for proper patterning of the embryo. Several P body components are involved in osk mRNA localization and translational repression, suggesting a link between P bodies and osk RNPs. In cultured mammalian cells, Ge-1 protein is required for P body formation. Combining genetic, biochemical and immunohistochemical approaches, we show that, in vivo, Drosophila Ge-1 (dGe-1) is an essential gene encoding a P body component that promotes formation of these structures in the germline. dGe-1 partially colocalizes with osk mRNA and is required for osk RNP integrity. Our analysis reveals that although under normal conditions dGe-1 function is not essential for osk mRNA localization, it becomes critical when other components of the localization machinery, such as staufen, Drosophila decapping protein 1 and barentsz are limiting. Our findings suggest an important role of dGe-1 in optimization of the osk mRNA localization process required for patterning the Drosophila embryo.
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Affiliation(s)
- Shih-Jung Fan
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Virginie Marchand
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- * E-mail:
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48
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Trucco A, Gaspar I, Ephrussi A. Retraction notice to: Assembly of endogenous oskar mRNA particles for motor-dependent transport in the Drosophila oocyte. Cell 2010; 143:485. [PMID: 21029867 DOI: 10.1016/j.cell.2010.10.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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49
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Trucco A, Gaspar I, Ephrussi A. Assembly of endogenous oskar mRNA particles for motor-dependent transport in the Drosophila oocyte. Cell 2009; 139:983-98. [PMID: 19945381 DOI: 10.1016/j.cell.2009.10.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Revised: 08/12/2009] [Accepted: 10/13/2009] [Indexed: 10/20/2022]
Abstract
oskar mRNA localization at the oocyte posterior pole is essential for correct patterning of the Drosophila embryo. Here we show at the ultrastructural level that endogenous oskar ribonucleoprotein complexes (RNPs) assemble sequentially with initial recruitment of Hrp48 and the exon junction complex (EJC) to oskar transcripts in the nurse cell nuclei, and subsequent recruitment of Staufen and microtubule motors, following transport to the cytoplasm. oskar particles are non-membrane-bound structures that coalesce as they move from the oocyte anterior to the posterior pole. Our analysis uncovers a role for the EJC component Barentsz in recruiting Tropomyosin II (TmII) to oskar particles in the ooplasm and reveals that TmII is required for kinesin binding to the RNPs. Finally, we show that both kinesin and dynein associate with oskar particles and are the primary microtubule motors responsible for transport of the RNPs within the oocyte.
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Affiliation(s)
- Alvar Trucco
- Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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50
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Abstract
The localization of mRNAs to subcellular compartments provides a mechanism for regulating gene expression with exquisite temporal and spatial control. Recent studies suggest that a large fraction of mRNAs localize to distinct cytoplasmic domains. In this Review, we focus on cis-acting RNA localization elements, RNA-binding proteins, and the assembly of mRNAs into granules that are transported by molecular motors along cytoskeletal elements to their final destination in the cell.
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Affiliation(s)
- Kelsey C Martin
- Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA 90095-1737, USA.
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