1
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Sekulski K, Cruz VE, Weirich CS, Erzberger JP. rRNA methylation by Spb1 regulates the GTPase activity of Nog2 during 60S ribosomal subunit assembly. Nat Commun 2023; 14:1207. [PMID: 36864048 PMCID: PMC9981671 DOI: 10.1038/s41467-023-36867-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 02/17/2023] [Indexed: 03/04/2023] Open
Abstract
Biogenesis of the large ribosomal (60S) subunit involves the assembly of three rRNAs and 46 proteins, a process requiring approximately 70 ribosome biogenesis factors (RBFs) that bind and release the pre-60S at specific steps along the assembly pathway. The methyltransferase Spb1 and the K-loop GTPase Nog2 are essential RBFs that engage the rRNA A-loop during sequential steps in 60S maturation. Spb1 methylates the A-loop nucleotide G2922 and a catalytically deficient mutant strain (spb1D52A) has a severe 60S biogenesis defect. However, the assembly function of this modification is currently unknown. Here, we present cryo-EM reconstructions that reveal that unmethylated G2922 leads to the premature activation of Nog2 GTPase activity and capture a Nog2-GDP-AlF4- transition state structure that implicates the direct involvement of unmodified G2922 in Nog2 GTPase activation. Genetic suppressors and in vivo imaging indicate that premature GTP hydrolysis prevents the efficient binding of Nog2 to early nucleoplasmic 60S intermediates. We propose that G2922 methylation levels regulate Nog2 recruitment to the pre-60S near the nucleolar/nucleoplasmic phase boundary, forming a kinetic checkpoint to regulate 60S production. Our approach and findings provide a template to study the GTPase cycles and regulatory factor interactions of the other K-loop GTPases involved in ribosome assembly.
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Affiliation(s)
- Kamil Sekulski
- Department of Biophysics, UT Southwestern Medical Center, 5323 Harry Hines Blvd., ND10.104B, Dallas, TX, 75390-8816, USA
| | - Victor Emmanuel Cruz
- Department of Biophysics, UT Southwestern Medical Center, 5323 Harry Hines Blvd., ND10.104B, Dallas, TX, 75390-8816, USA
| | - Christine S Weirich
- Department of Biophysics, UT Southwestern Medical Center, 5323 Harry Hines Blvd., ND10.104B, Dallas, TX, 75390-8816, USA
| | - Jan P Erzberger
- Department of Biophysics, UT Southwestern Medical Center, 5323 Harry Hines Blvd., ND10.104B, Dallas, TX, 75390-8816, USA.
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2
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Dörner K, Ruggeri C, Zemp I, Kutay U. Ribosome biogenesis factors-from names to functions. EMBO J 2023; 42:e112699. [PMID: 36762427 PMCID: PMC10068337 DOI: 10.15252/embj.2022112699] [Citation(s) in RCA: 26] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 12/13/2022] [Accepted: 01/19/2023] [Indexed: 02/11/2023] Open
Abstract
The assembly of ribosomal subunits is a highly orchestrated process that involves a huge cohort of accessory factors. Most eukaryotic ribosome biogenesis factors were first identified by genetic screens and proteomic approaches of pre-ribosomal particles in Saccharomyces cerevisiae. Later, research on human ribosome synthesis not only demonstrated that the requirement for many of these factors is conserved in evolution, but also revealed the involvement of additional players, reflecting a more complex assembly pathway in mammalian cells. Yet, it remained a challenge for the field to assign a function to many of the identified factors and to reveal their molecular mode of action. Over the past decade, structural, biochemical, and cellular studies have largely filled this gap in knowledge and led to a detailed understanding of the molecular role that many of the players have during the stepwise process of ribosome maturation. Such detailed knowledge of the function of ribosome biogenesis factors will be key to further understand and better treat diseases linked to disturbed ribosome assembly, including ribosomopathies, as well as different types of cancer.
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Affiliation(s)
- Kerstin Dörner
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.,Molecular Life Sciences Ph.D. Program, Zurich, Switzerland
| | - Chiara Ruggeri
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.,RNA Biology Ph.D. Program, Zurich, Switzerland
| | - Ivo Zemp
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Ulrike Kutay
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
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3
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Chowdhury MN, Jin H. The RGG motif proteins: Interactions, functions, and regulations. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 14:e1748. [PMID: 35661420 PMCID: PMC9718894 DOI: 10.1002/wrna.1748] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 04/25/2022] [Accepted: 05/09/2022] [Indexed: 01/31/2023]
Abstract
Proteins with motifs rich in arginines and glycines were discovered decades ago and are functionally involved in a staggering range of essential processes in the cell. Versatile, specific, yet adaptable molecular interactions enabled by the unique combination of arginine and glycine, combined with multiplicity of molecular recognition conferred by repeated di-, tri-, and multiple peptide motifs, allow RGG motif proteins to interact with a broad range of proteins and nucleic acids. Furthermore, posttranslational modifications at the arginines in the motif extend the RGG protein's capacity for a fine-tuned regulation. In this review, we focus on the biochemical properties of the RGG motif, its molecular interactions with RNAs and proteins, and roles of the posttranslational modification in modulating their interactions. We discuss current knowledge of the RGG motif proteins involved in mRNA transport and translation, highlight our merging understanding of their molecular functions in translational regulation and summarize areas of research in the future critical in understanding this important family of proteins. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications Translation > Mechanisms.
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Affiliation(s)
- Mashiat N. Chowdhury
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801
| | - Hong Jin
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801,Carl R. Woese Institute for Genomic Biology, 1206 West Gregory Drive, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801,Corresponding author: Phone: (217)244-9493, Fax: (217)244-5858,
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4
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Dörner K, Badertscher L, Horváth B, Hollandi R, Molnár C, Fuhrer T, Meier R, Sárazová M, van den Heuvel J, Zamboni N, Horvath P, Kutay U. Genome-wide RNAi screen identifies novel players in human 60S subunit biogenesis including key enzymes of polyamine metabolism. Nucleic Acids Res 2022; 50:2872-2888. [PMID: 35150276 PMCID: PMC8934630 DOI: 10.1093/nar/gkac072] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 01/18/2022] [Accepted: 01/25/2022] [Indexed: 12/19/2022] Open
Abstract
Ribosome assembly is an essential process that is linked to human congenital diseases and tumorigenesis. While great progress has been made in deciphering mechanisms governing ribosome biogenesis in eukaryotes, an inventory of factors that support ribosome synthesis in human cells is still missing, in particular regarding the maturation of the large 60S subunit. Here, we performed a genome-wide RNAi screen using an imaging-based, single cell assay to unravel the cellular machinery promoting 60S subunit assembly in human cells. Our screen identified a group of 310 high confidence factors. These highlight the conservation of the process across eukaryotes and reveal the intricate connectivity of 60S subunit maturation with other key cellular processes, including splicing, translation, protein degradation, chromatin organization and transcription. Intriguingly, we also identified a cluster of hits comprising metabolic enzymes of the polyamine synthesis pathway. We demonstrate that polyamines, which have long been used as buffer additives to support ribosome assembly in vitro, are required for 60S maturation in living cells. Perturbation of polyamine metabolism results in early defects in 60S but not 40S subunit maturation. Collectively, our data reveal a novel function for polyamines in living cells and provide a rich source for future studies on ribosome synthesis.
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Affiliation(s)
- Kerstin Dörner
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland.,Molecular Life Sciences Ph.D. Program, 8057 Zurich, Switzerland
| | - Lukas Badertscher
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland.,Molecular Life Sciences Ph.D. Program, 8057 Zurich, Switzerland
| | - Bianka Horváth
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland.,Molecular Life Sciences Ph.D. Program, 8057 Zurich, Switzerland
| | - Réka Hollandi
- Synthetic and Systems Biology Unit, Biological Research Center, 6726 Szeged, Hungary
| | - Csaba Molnár
- Synthetic and Systems Biology Unit, Biological Research Center, 6726 Szeged, Hungary
| | - Tobias Fuhrer
- Institute of Molecular Systems Biology, Department of Biology, ETH Zürich, 8093 Zürich, Switzerland
| | - Roger Meier
- ScopeM, ETH Zürich, 8093 Zürich, Switzerland
| | - Marie Sárazová
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Jasmin van den Heuvel
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Nicola Zamboni
- Institute of Molecular Systems Biology, Department of Biology, ETH Zürich, 8093 Zürich, Switzerland
| | - Peter Horvath
- Synthetic and Systems Biology Unit, Biological Research Center, 6726 Szeged, Hungary.,Institute for Molecular Medicine Finland, University of Helsinki, 00014 Helsinki, Finland
| | - Ulrike Kutay
- Institute of Biochemistry, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
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5
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Oborská-Oplová M, Fischer U, Altvater M, Panse VG. Eukaryotic Ribosome assembly and Nucleocytoplasmic Transport. Methods Mol Biol 2022; 2533:99-126. [PMID: 35796985 PMCID: PMC9761919 DOI: 10.1007/978-1-0716-2501-9_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The process of eukaryotic ribosome assembly stretches across the nucleolus, the nucleoplasm and the cytoplasm, and therefore relies on efficient nucleocytoplasmic transport. In yeast, the import machinery delivers ~140,000 ribosomal proteins every minute to the nucleus for ribosome assembly. At the same time, the export machinery facilitates translocation of ~2000 pre-ribosomal particles every minute through ~200 nuclear pore complexes (NPC) into the cytoplasm. Eukaryotic ribosome assembly also requires >200 conserved assembly factors, which transiently associate with pre-ribosomal particles. Their site(s) of action on maturing pre-ribosomes are beginning to be elucidated. In this chapter, we outline protocols that enable rapid biochemical isolation of pre-ribosomal particles for single particle cryo-electron microscopy (cryo-EM) and in vitro reconstitution of nuclear transport processes. We discuss cell-biological and genetic approaches to investigate how the ribosome assembly and the nucleocytoplasmic transport machineries collaborate to produce functional ribosomes.
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Affiliation(s)
- Michaela Oborská-Oplová
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Ute Fischer
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | | | - Vikram Govind Panse
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
- Faculty of Science, University of Zurich, Zurich, Switzerland.
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6
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Birikmen M, Bohnsack KE, Tran V, Somayaji S, Bohnsack MT, Ebersberger I. Tracing Eukaryotic Ribosome Biogenesis Factors Into the Archaeal Domain Sheds Light on the Evolution of Functional Complexity. Front Microbiol 2021; 12:739000. [PMID: 34603269 PMCID: PMC8481954 DOI: 10.3389/fmicb.2021.739000] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/17/2021] [Indexed: 01/23/2023] Open
Abstract
Ribosome assembly is an essential and carefully choreographed cellular process. In eukaryotes, several 100 proteins, distributed across the nucleolus, nucleus, and cytoplasm, co-ordinate the step-wise assembly of four ribosomal RNAs (rRNAs) and approximately 80 ribosomal proteins (RPs) into the mature ribosomal subunits. Due to the inherent complexity of the assembly process, functional studies identifying ribosome biogenesis factors and, more importantly, their precise functions and interplay are confined to a few and very well-established model organisms. Although best characterized in yeast (Saccharomyces cerevisiae), emerging links to disease and the discovery of additional layers of regulation have recently encouraged deeper analysis of the pathway in human cells. In archaea, ribosome biogenesis is less well-understood. However, their simpler sub-cellular structure should allow a less elaborated assembly procedure, potentially providing insights into the functional essentials of ribosome biogenesis that evolved long before the diversification of archaea and eukaryotes. Here, we use a comprehensive phylogenetic profiling setup, integrating targeted ortholog searches with automated scoring of protein domain architecture similarities and an assessment of when search sensitivity becomes limiting, to trace 301 curated eukaryotic ribosome biogenesis factors across 982 taxa spanning the tree of life and including 727 archaea. We show that both factor loss and lineage-specific modifications of factor function modulate ribosome biogenesis, and we highlight that limited sensitivity of the ortholog search can confound evolutionary conclusions. Projecting into the archaeal domain, we find that only few factors are consistently present across the analyzed taxa, and lineage-specific loss is common. While members of the Asgard group are not special with respect to their inventory of ribosome biogenesis factors (RBFs), they unite the highest number of orthologs to eukaryotic RBFs in one taxon. Using large ribosomal subunit maturation as an example, we demonstrate that archaea pursue a simplified version of the corresponding steps in eukaryotes. Much of the complexity of this process evolved on the eukaryotic lineage by the duplication of ribosomal proteins and their subsequent functional diversification into ribosome biogenesis factors. This highlights that studying ribosome biogenesis in archaea provides fundamental information also for understanding the process in eukaryotes.
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Affiliation(s)
- Mehmet Birikmen
- Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Frankfurt, Germany
| | - Katherine E Bohnsack
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Vinh Tran
- Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Frankfurt, Germany
| | - Sharvari Somayaji
- Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Frankfurt, Germany
| | - Markus T Bohnsack
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany.,Göttingen Center for Molecular Biosciences, Georg-August University, Göttingen, Germany
| | - Ingo Ebersberger
- Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Frankfurt, Germany.,Senckenberg Biodiversity and Climate Research Center (S-BIK-F), Frankfurt, Germany.,LOEWE Center for Translational Biodiversity Genomics (LOEWE-TBG), Frankfurt, Germany
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7
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Sajidah ES, Lim K, Wong RW. How SARS-CoV-2 and Other Viruses Build an Invasion Route to Hijack the Host Nucleocytoplasmic Trafficking System. Cells 2021; 10:1424. [PMID: 34200500 PMCID: PMC8230057 DOI: 10.3390/cells10061424] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 05/31/2021] [Accepted: 06/03/2021] [Indexed: 12/14/2022] Open
Abstract
The host nucleocytoplasmic trafficking system is often hijacked by viruses to accomplish their replication and to suppress the host immune response. Viruses encode many factors that interact with the host nuclear transport receptors (NTRs) and the nucleoporins of the nuclear pore complex (NPC) to access the host nucleus. In this review, we discuss the viral factors and the host factors involved in the nuclear import and export of viral components. As nucleocytoplasmic shuttling is vital for the replication of many viruses, we also review several drugs that target the host nuclear transport machinery and discuss their feasibility for use in antiviral treatment.
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Affiliation(s)
- Elma Sakinatus Sajidah
- Division of Nano Life Science in the Graduate School of Frontier Science Initiative, Kanazawa University, Kanazawa 920-1192, Japan;
| | - Keesiang Lim
- WPI-Nano Life Science Institute, Kanazawa University, Kanazawa 920-1192, Japan
| | - Richard W. Wong
- Division of Nano Life Science in the Graduate School of Frontier Science Initiative, Kanazawa University, Kanazawa 920-1192, Japan;
- WPI-Nano Life Science Institute, Kanazawa University, Kanazawa 920-1192, Japan
- Cell-Bionomics Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa 920-1192, Japan
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8
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Allegretti M, Zimmerli CE, Rantos V, Wilfling F, Ronchi P, Fung HKH, Lee CW, Hagen W, Turoňová B, Karius K, Börmel M, Zhang X, Müller CW, Schwab Y, Mahamid J, Pfander B, Kosinski J, Beck M. In-cell architecture of the nuclear pore and snapshots of its turnover. Nature 2020; 586:796-800. [PMID: 32879490 DOI: 10.1038/s41586-020-2670-5] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 06/01/2020] [Indexed: 12/25/2022]
Abstract
Nuclear pore complexes (NPCs) fuse the inner and outer membranes of the nuclear envelope. They comprise hundreds of nucleoporins (Nups) that assemble into multiple subcomplexes and form large central channels for nucleocytoplasmic exchange1,2. How this architecture facilitates messenger RNA export, NPC biogenesis and turnover remains poorly understood. Here we combine in situ structural biology and integrative modelling with correlative light and electron microscopy and molecular perturbation to structurally analyse NPCs in intact Saccharomyces cerevisiae cells within the context of nuclear envelope remodelling. We find an in situ conformation and configuration of the Nup subcomplexes that was unexpected from the results of previous in vitro analyses. The configuration of the Nup159 complex appears critical to spatially accommodate its function as an mRNA export platform, and as a mediator of NPC turnover. The omega-shaped nuclear envelope herniae that accumulate in nup116Δ cells3 conceal partially assembled NPCs lacking multiple subcomplexes, including the Nup159 complex. Under conditions of starvation, herniae of a second type are formed that cytoplasmically expose NPCs. These results point to a model of NPC turnover in which NPC-containing vesicles bud off from the nuclear envelope before degradation by the autophagy machinery. Our study emphasizes the importance of investigating the structure-function relationship of macromolecular complexes in their cellular context.
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Affiliation(s)
- Matteo Allegretti
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Christian E Zimmerli
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.,Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, Heidelberg, Germany
| | - Vasileios Rantos
- Centre for Structural Systems Biology (CSSB), DESY and European Molecular Biology Laboratory, Hamburg, Germany
| | | | - Paolo Ronchi
- Electron Microscopy Core Facility (EMCF), European Molecular Biology Laboratory, Heidelberg, Germany
| | - Herman K H Fung
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Chia-Wei Lee
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Wim Hagen
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Beata Turoňová
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Kai Karius
- Centre for Structural Systems Biology (CSSB), DESY and European Molecular Biology Laboratory, Hamburg, Germany
| | - Mandy Börmel
- Electron Microscopy Core Facility (EMCF), European Molecular Biology Laboratory, Heidelberg, Germany
| | - Xiaojie Zhang
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Christoph W Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Yannick Schwab
- Electron Microscopy Core Facility (EMCF), European Molecular Biology Laboratory, Heidelberg, Germany.,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Boris Pfander
- Max Planck Institute of Biochemistry, Martinsried, Germany.
| | - Jan Kosinski
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany. .,Centre for Structural Systems Biology (CSSB), DESY and European Molecular Biology Laboratory, Hamburg, Germany.
| | - Martin Beck
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany. .,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany. .,Department of Molecular Sociology, Max Planck Institute of Biophysics, Frankfurt, Germany.
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9
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Abstract
Ribonucleic acid (RNA) is involved in translation and transcription, which are the mechanisms in which cells express genes (Alberts et al., 2002). The three classes of RNA discussed are transfer RNA (tRNA), messenger RNA (mRNA), and ribosomal RNA (rRNA). mRNA is the transcript encoded from DNA, rRNA is associated with ribosomes, and tRNA is associated with amino acids and is used to read mRNA transcripts to make proteins (Lodish, Berk, Zipursky, et al., 2000). Interestingly, the function of tRNA, rRNA, and mRNA can be significantly altered by chemical modifications at the co-transcriptional and post-transcriptional levels, and there are over 171 of these modifications identified thus far (Boccaletto et al., 2018; Modomics-Modified bases, 2017). Several of these modifications are linked to diseases such as cancer, diabetes, and neurological disorders. In this review, we will introduce a few RNA modifications with biological functions and how dysregulation of these RNA modifications is linked to human disease.
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Affiliation(s)
- Amber Yanas
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Kathy Fange Liu
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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10
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The chemical diversity of RNA modifications. Biochem J 2019; 476:1227-1245. [PMID: 31028151 DOI: 10.1042/bcj20180445] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 02/25/2019] [Accepted: 02/26/2019] [Indexed: 12/16/2022]
Abstract
Nucleic acid modifications in DNA and RNA ubiquitously exist among all the three kingdoms of life. This trait significantly broadens the genome diversity and works as an important means of gene transcription regulation. Although mammalian systems have limited types of DNA modifications, over 150 different RNA modification types have been identified, with a wide variety of chemical diversities. Most modifications occur on transfer RNA and ribosomal RNA, however many of the modifications also occur on other types of RNA species including mammalian mRNA and small nuclear RNA, where they are essential for many biological roles, including developmental processes and stem cell differentiation. These post-transcriptional modifications are enzymatically installed and removed in a site-specific manner by writer and eraser proteins respectively, while reader proteins can interpret modifications and transduce the signal for downstream functions. Dysregulation of mRNA modifications manifests as disease states, including multiple types of human cancer. In this review, we will introduce the chemical features and biological functions of these modifications in the coding and non-coding RNA species.
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11
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Patchett S, Musalgaonkar S, Malyutin AG, Johnson AW. The T-cell leukemia related rpl10-R98S mutant traps the 60S export adapter Nmd3 in the ribosomal P site in yeast. PLoS Genet 2017; 13:e1006894. [PMID: 28715419 PMCID: PMC5536393 DOI: 10.1371/journal.pgen.1006894] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 07/31/2017] [Accepted: 06/23/2017] [Indexed: 12/12/2022] Open
Abstract
Mutations in the ribosomal protein Rpl10 (uL16) can be drivers of T-cell acute lymphoblastic leukemia (T-ALL). We previously showed that these T-ALL mutations disrupt late cytoplasmic maturation of the 60S ribosomal subunit, blocking the release of the trans-acting factors Nmd3 and Tif6 in S. cerevisiae. Consequently, these mutant ribosomes do not efficiently pass the cytoplasmic quality control checkpoint and are blocked from engaging in translation. Here, we characterize suppressing mutations of the T-ALL-related rpl10-R98S mutant that bypass this block and show that the molecular defect of rpl10-R98S is a failure to release Nmd3 from the P site. Suppressing mutations were identified in Nmd3 and Tif6 that disrupted interactions between Nmd3 and the ribosome, or between Nmd3 and Tif6. Using an in vitro system with purified components, we found that Nmd3 inhibited Sdo1-stimulated Efl1 activity on mutant rpl10-R98S but not wild-type 60S subunits. Importantly, this inhibition was overcome in vitro by mutations in Nmd3 that suppressed rpl10-R98S in vivo. These results strongly support a model that Nmd3 must be dislodged from the P site to allow Sdo1 activation of Efl1, and define a failure in the removal of Nmd3 as the molecular defect of the T-ALL-associated rpl10-R98S mutation. The ribosome is a large and structurally complex macromolecular machine, responsible for synthesizing proteins in all living cells, across all domains of life. The correct assembly of ribosomes is important for their ability to faithfully decode messenger RNAs and synthesize proteins. The insertion of the ribosomal protein Rpl10 into the ribosome completes the catalytic center of the large subunit and is necessary for the removal of the assembly factors Nmd3 and Tif6, which allows the subunit to participate in translation. The insertion of Rpl10 is monitored by proteins that mimic translation factors during a quality control check for ribosome function. Ribosomes containing mutations in Rpl10 associated with pediatric T-cell leukemia fail in this quality control check and prevent the removal of Tif6 and Nmd3. However, it was not known how these mutations in Rpl10 block the quality control check. We recently presented the structure of Nmd3 and Tif6 on the large ribosomal subunit from yeast. In this work, we take advantage of our recent structural work and use a combination of genetic and biochemical techniques to delineate the molecular defect in the ribosome when Rpl10 is mutated.
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Affiliation(s)
- Stephanie Patchett
- Depatment of Molecular Biosciences, the University of Texas at Austin, Austin, Texas, United States of America
| | - Sharmishtha Musalgaonkar
- Depatment of Molecular Biosciences, the University of Texas at Austin, Austin, Texas, United States of America
| | - Andrey G Malyutin
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, United States of America
| | - Arlen W Johnson
- Depatment of Molecular Biosciences, the University of Texas at Austin, Austin, Texas, United States of America
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12
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Principles of 60S ribosomal subunit assembly emerging from recent studies in yeast. Biochem J 2017; 474:195-214. [PMID: 28062837 DOI: 10.1042/bcj20160516] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/22/2016] [Accepted: 11/24/2016] [Indexed: 12/31/2022]
Abstract
Ribosome biogenesis requires the intertwined processes of folding, modification, and processing of ribosomal RNA, together with binding of ribosomal proteins. In eukaryotic cells, ribosome assembly begins in the nucleolus, continues in the nucleoplasm, and is not completed until after nascent particles are exported to the cytoplasm. The efficiency and fidelity of ribosome biogenesis are facilitated by >200 assembly factors and ∼76 different small nucleolar RNAs. The pathway is driven forward by numerous remodeling events to rearrange the ribonucleoprotein architecture of pre-ribosomes. Here, we describe principles of ribosome assembly that have emerged from recent studies of biogenesis of the large ribosomal subunit in the yeast Saccharomyces cerevisiae We describe tools that have empowered investigations of ribosome biogenesis, and then summarize recent discoveries about each of the consecutive steps of subunit assembly.
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13
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Gonzales-Zubiate FA, Okuda EK, Da Cunha JPC, Oliveira CC. Identification of karyopherins involved in the nuclear import of RNA exosome subunit Rrp6 in Saccharomyces cerevisiae. J Biol Chem 2017; 292:12267-12284. [PMID: 28539363 DOI: 10.1074/jbc.m116.772376] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 05/11/2017] [Indexed: 11/06/2022] Open
Abstract
The exosome is a conserved multiprotein complex essential for RNA processing and degradation. The nuclear exosome is a key factor for pre-rRNA processing through the activity of its catalytic subunits, Rrp6 and Rrp44. In Saccharomyces cerevisiae, Rrp6 is exclusively nuclear and has been shown to interact with exosome cofactors. With the aim of analyzing proteins associated with the nuclear exosome, in this work, we purified the complex with Rrp6-TAP, identified the co-purified proteins by mass spectrometry, and found karyopherins to be one of the major groups of proteins enriched in the samples. By investigating the biological importance of these protein interactions, we identified Srp1, Kap95, and Sxm1 as the most important karyopherins for Rrp6 nuclear import and the nuclear localization signals recognized by them. Based on the results shown here, we propose a model of multiple pathways for the transport of Rrp6 to the nucleus.
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Affiliation(s)
| | - Ellen K Okuda
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo 05508-000 SP, Brazil
| | - Julia P C Da Cunha
- Cell Cycle Laboratory, Center of Toxins, Immune Response and Cell Signaling-Center for Research on Toxins, Immune-response, and Cell Signaling (CeTICS), Butantan Institute, São Paulo 05503-900 SP, Brazil
| | - Carla Columbano Oliveira
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo 05508-000 SP, Brazil.
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14
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Structural snapshot of cytoplasmic pre-60S ribosomal particles bound by Nmd3, Lsg1, Tif6 and Reh1. Nat Struct Mol Biol 2017; 24:214-220. [PMID: 28112732 DOI: 10.1038/nsmb.3364] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 12/19/2016] [Indexed: 01/01/2023]
Abstract
A key step in ribosome biogenesis is the nuclear export of pre-ribosomal particles. Nmd3, a highly conserved protein in eukaryotes, is a specific adaptor required for the export of pre-60S particles. Here we used cryo-electron microscopy (cryo-EM) to characterize Saccharomyces cerevisiae pre-60S particles purified with epitope-tagged Nmd3. Our structural analysis indicates that these particles belong to a specific late stage of cytoplasmic pre-60S maturation in which ribosomal proteins uL16, uL10, uL11, eL40 and eL41 are deficient, but ribosome assembly factors Nmd3, Lsg1, Tif6 and Reh1 are present. Nmd3 and Lsg1 are located near the peptidyl-transferase center (PTC). In particular, Nmd3 recognizes the PTC in its near-mature conformation. In contrast, Reh1 is anchored to the exit of the polypeptide tunnel, with its C terminus inserted into the tunnel. These findings pinpoint a structural checkpoint role for Nmd3 in PTC assembly, and provide information about functional and mechanistic roles of these assembly factors in the maturation of the 60S ribosomal subunit.
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15
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Using Fluorescent Reporters in Conjunction with Cytometry and Statistics to Assess Nuclear Accumulation of Ribosomal Proteins. Methods Mol Biol 2016. [PMID: 27797082 DOI: 10.1007/978-1-4939-6545-8_13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Fluorescently labeled ribosomal proteins can be used to detect and monitor the intracellular localization of these proteins. Both Rps2, a subunit of the 40S ribosome, and Rpl25, a subunit of the 60S ribosome, have been fused to the coding sequence of GFP at their C-termini and the fusions have been used to monitor their localization within cells using fluorescent microscopy. Normally these proteins are efficiently incorporated into ribosomes and exported into the cytoplasm where they exhibit a low uniform fluorescence. However, these Rps2- and Rpl25-GFP proteins accumulate in the nucleus of mutants defective in ribosome biogenesis or export. Here, we describe a single-cell quantitative method to assess the nuclear accumulation of ribosomal proteins using cytometry and biostatistics. This assay was developed for use with GFP reporters for ribosome biogenesis in budding yeast but could be adapted for use with any GFP reporter that accumulates into the nucleus under adverse conditions.
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16
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Neumann B, Wu H, Hackmann A, Krebber H. Nuclear Export of Pre-Ribosomal Subunits Requires Dbp5, but Not as an RNA-Helicase as for mRNA Export. PLoS One 2016; 11:e0149571. [PMID: 26872259 PMCID: PMC4752221 DOI: 10.1371/journal.pone.0149571] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 02/01/2016] [Indexed: 11/28/2022] Open
Abstract
The DEAD-box RNA-helicase Dbp5/Rat8 is known for its function in nuclear mRNA export, where it displaces the export receptor Mex67 from the mRNA at the cytoplasmic side of the nuclear pore complex (NPC). Here we show that Dbp5 is also required for the nuclear export of both pre-ribosomal subunits. Yeast temperature-sensitive dbp5 mutants accumulate both ribosomal particles in their nuclei. Furthermore, Dbp5 genetically and physically interacts with known ribosomal transport factors such as Nmd3. Similar to mRNA export we show that also for ribosomal transport Dbp5 is required at the cytoplasmic side of the NPC. However, unlike its role in mRNA export, Dbp5 does not seem to undergo its ATPase cycle for this function, as ATPase-deficient dbp5 mutants that selectively inhibit mRNA export do not affect ribosomal transport. Furthermore, mutants of GLE1, the ATPase stimulating factor of Dbp5, show no major ribosomal export defects. Consequently, while Dbp5 uses its ATPase cycle to displace the export receptor Mex67 from the translocated mRNAs, Mex67 remains bound to ribosomal subunits upon transit to the cytoplasm, where it is detectable on translating ribosomes. Therefore, we propose a model, in which Dbp5 supports ribosomal transport by capturing ribosomal subunits upon their cytoplasmic appearance at the NPC, possibly by binding export factors such as Mex67. Thus, our findings reveal that although different ribonucleoparticles, mRNAs and pre-ribosomal subunits, use shared export factors, they utilize different transport mechanisms.
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Affiliation(s)
- Bettina Neumann
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften (GZMB), Georg-August Universität Göttingen, Germany
| | - Haijia Wu
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften (GZMB), Georg-August Universität Göttingen, Germany
| | - Alexandra Hackmann
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften (GZMB), Georg-August Universität Göttingen, Germany
| | - Heike Krebber
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften (GZMB), Georg-August Universität Göttingen, Germany
- * E-mail:
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17
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Sloan KE, Gleizes PE, Bohnsack MT. Nucleocytoplasmic Transport of RNAs and RNA-Protein Complexes. J Mol Biol 2015; 428:2040-59. [PMID: 26434509 DOI: 10.1016/j.jmb.2015.09.023] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 09/26/2015] [Accepted: 09/28/2015] [Indexed: 12/15/2022]
Abstract
RNAs and ribonucleoprotein complexes (RNPs) play key roles in mediating and regulating gene expression. In eukaryotes, most RNAs are transcribed, processed and assembled with proteins in the nucleus and then either function in the cytoplasm or also undergo a cytoplasmic phase in their biogenesis. This compartmentalization ensures that sequential steps in gene expression and RNP production are performed in the correct order and it allows important quality control mechanisms that prevent the involvement of aberrant RNAs/RNPs in these cellular pathways. The selective exchange of RNAs/RNPs between the nucleus and cytoplasm is enabled by nuclear pore complexes, which function as gateways between these compartments. RNA/RNP transport is facilitated by a range of nuclear transport receptors and adaptors, which are specifically recruited to their cargos and mediate interactions with nucleoporins to allow directional translocation through nuclear pore complexes. While some transport factors are only responsible for the export/import of a certain class of RNA/RNP, others are multifunctional and, in the case of large RNPs, several export factors appear to work together to bring about export. Recent structural studies have revealed aspects of the mechanisms employed by transport receptors to enable specific cargo recognition, and genome-wide approaches have provided the first insights into the diverse composition of pre-mRNPs during export. Furthermore, the regulation of RNA/RNP export is emerging as an important means to modulate gene expression under stress conditions and in disease.
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Affiliation(s)
- Katherine E Sloan
- Institute for Molecular Biology, Goettingen University Medical Department, 37073 Goettingen, Germany
| | - Pierre-Emmanuel Gleizes
- Laboratoire de Biologie Moléculaire Eucaryote, UMR 5099, Université de Toulouse-Paul Sabatier, CNRS, Toulouse, France
| | - Markus T Bohnsack
- Institute for Molecular Biology, Goettingen University Medical Department, 37073 Goettingen, Germany; Goettingen Centre for Molecular Biosciences, Georg-August-University, 37075 Goettingen, Germany.
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18
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Nerurkar P, Altvater M, Gerhardy S, Schütz S, Fischer U, Weirich C, Panse VG. Eukaryotic Ribosome Assembly and Nuclear Export. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 319:107-40. [DOI: 10.1016/bs.ircmb.2015.07.002] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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19
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Lui J, Castelli LM, Pizzinga M, Simpson CE, Hoyle NP, Bailey KL, Campbell SG, Ashe MP. Granules harboring translationally active mRNAs provide a platform for P-body formation following stress. Cell Rep 2014; 9:944-54. [PMID: 25437551 PMCID: PMC4536303 DOI: 10.1016/j.celrep.2014.09.040] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 08/16/2014] [Accepted: 09/22/2014] [Indexed: 12/13/2022] Open
Abstract
The localization of mRNA to defined cytoplasmic sites in eukaryotic cells not only allows localized protein production but also determines the fate of mRNAs. For instance, translationally repressed mRNAs localize to P-bodies and stress granules where their decay and storage, respectively, are directed. Here, we find that several mRNAs are localized to granules in unstressed, actively growing cells. These granules play a key role in the stress-dependent formation of P-bodies. Specific glycolytic mRNAs are colocalized in multiple granules per cell, which aggregate during P-body formation. Such aggregation is still observed under conditions or in mutants where P-bodies do not form. In unstressed cells, the mRNA granules appear associated with active translation; this might enable a coregulation of protein expression from the same pathways or complexes. Parallels can be drawn between this coregulation and the advantage of operons in prokaryotic systems.
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Affiliation(s)
- Jennifer Lui
- Faculty of Life Sciences, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Lydia M Castelli
- Faculty of Life Sciences, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Mariavittoria Pizzinga
- Faculty of Life Sciences, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Clare E Simpson
- Faculty of Life Sciences, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Nathaniel P Hoyle
- Faculty of Life Sciences, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Kathryn L Bailey
- Faculty of Life Sciences, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Susan G Campbell
- Biosciences Department, Faculty of Health and Wellbeing, Sheffield Hallam University, Howards Street, Sheffield S1 1WB, UK
| | - Mark P Ashe
- Faculty of Life Sciences, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK.
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20
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Nguyen MM, Harmon RM, Wang Z. Characterization of karyopherins in androgen receptor intracellular trafficking in the yeast model. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2014; 7:2768-2779. [PMID: 25031696 PMCID: PMC4097219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 05/25/2014] [Indexed: 06/03/2023]
Abstract
BACKGROUND Mechanisms regulating androgen receptor (AR) subcellular localization represent an essential component of AR signaling. Karyopherins are a family of nucleocytoplasmic trafficking factors. In this paper, we used the yeast model to study the effects of karyopherins on the subcellular localization of the AR. METHODS Yeast mutants deficient in different nuclear transport factors were transformed with various AR based, GFP tagged constructs and their localization was monitored using microscopy. RESULTS We showed that yeast can mediate androgen-induced AR nuclear localization and that in addition to the import factor, Importinα/β, this process required the import karyopherin Sxm1. We also showed that a previously identified nuclear export sequence (NES(AR)) in the ligand binding domain of AR does not appear to rely on karyopherins for cytoplasmic localization. CONCLUSIONS These results suggest that while AR nuclear import relies on karyopherin activity, AR nuclear export and/or cytoplasmic localization may require other undefined mechanisms.
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Affiliation(s)
- Minh M Nguyen
- Department of Urology, School of Medicine Pittsburgh, University of Pittsburgh Cancer InstitutePA 15232, USA
| | - Robert M Harmon
- Department of Pathology, Northwestern UniversityChicago, IL 60611, USA
| | - Zhou Wang
- Department of Urology, School of Medicine Pittsburgh, University of Pittsburgh Cancer InstitutePA 15232, USA
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21
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Assembly and nuclear export of pre-ribosomal particles in budding yeast. Chromosoma 2014; 123:327-44. [PMID: 24817020 DOI: 10.1007/s00412-014-0463-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 03/18/2014] [Accepted: 04/07/2014] [Indexed: 11/27/2022]
Abstract
The ribosome is responsible for the final step of decoding genetic information into proteins. Therefore, correct assembly of ribosomes is a fundamental task for all living cells. In eukaryotes, the construction of the ribosome which begins in the nucleolus requires coordinated efforts of >350 specialized factors that associate with pre-ribosomal particles at distinct stages to perform specific assembly steps. On their way through the nucleus, diverse energy-consuming enzymes are thought to release assembly factors from maturing pre-ribosomal particles after accomplishing their task(s). Subsequently, recruitment of export factors prepares pre-ribosomal particles for transport through nuclear pore complexes. Pre-ribosomes are exported into the cytoplasm in a functionally inactive state, where they undergo final maturation before initiating translation. Accumulating evidence indicates a tight coupling between nuclear export, cytoplasmic maturation, and final proofreading of the ribosome. In this review, we summarize our current understanding of nuclear export of pre-ribosomal subunits and cytoplasmic maturation steps that render pre-ribosomal subunits translation-competent.
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22
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Abstract
Construction of the eukaryotic ribosome begins in the nucleolus and requires >300 evolutionarily conserved nonribosomal trans-acting factors, which transiently associate with preribosomal subunits at distinct assembly stages. A subset of trans-acting and transport factors passage assembled preribosomal subunits in a functionally inactive state through the nuclear pore complexes (NPC) into the cytoplasm, where they undergo final maturation before initiating translation. Here, we summarize the repertoire of tools developed in the model organism budding yeast that are spearheading the functional analyses of trans-acting factors involved in the assembly and intracellular transport of preribosomal subunits. We elaborate on different GFP-tagged ribosomal protein reporters and a pre-rRNA reporter that reliably monitors the movement of preribosomal particles from the nucleolus to cytoplasm. We discuss the powerful yeast heterokaryon assay, which can be employed to uncover shuttling trans-acting factors that need to accompany preribosomal subunits to the cytoplasm to be released prior to initiating translation. Moreover, we present two biochemical approaches, namely sucrose gradient analyses and tandem affinity purification, that are rapidly facilitating the uncovering of regulatory processes that control the compositional dynamics of trans-acting factors on maturing preribosomal particles. Altogether, these approaches when combined with traditional analytical biochemistry, targeted proteomics and structural methodologies, will contribute to the dissection of the assembly and intracellular transport of preribosomal subunits, as well as other macromolecular assemblies that influence diverse biological pathways.
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MESH Headings
- Biological Transport/genetics
- Green Fluorescent Proteins/genetics
- In Situ Hybridization, Fluorescence/methods
- Karyopherins/genetics
- Mass Spectrometry/methods
- Microscopy, Fluorescence/methods
- Nuclear Pore/genetics
- Nuclear Pore/metabolism
- Nucleolus Organizer Region/genetics
- RNA, Ribosomal/biosynthesis
- RNA, Ribosomal/genetics
- Receptors, Cytoplasmic and Nuclear/genetics
- Ribosome Subunits, Large, Eukaryotic/genetics
- Ribosome Subunits, Large, Eukaryotic/metabolism
- Ribosome Subunits, Small, Eukaryotic/genetics
- Ribosome Subunits, Small, Eukaryotic/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Ultracentrifugation/methods
- Exportin 1 Protein
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Affiliation(s)
- Martin Altvater
- Institute of Biochemistry (IBC), ETH Zürich, Otto-Stern-Weg 3, Zurich, Switzerland; MLS Program, Life Science Zurich Graduate School, Winterthurerstrasse 190, Zurich, Switzerland
| | - Sabina Schütz
- Institute of Biochemistry (IBC), ETH Zürich, Otto-Stern-Weg 3, Zurich, Switzerland; MLS Program, Life Science Zurich Graduate School, Winterthurerstrasse 190, Zurich, Switzerland
| | - Yiming Chang
- Institute of Biochemistry (IBC), ETH Zürich, Otto-Stern-Weg 3, Zurich, Switzerland
| | - Vikram Govind Panse
- Institute of Biochemistry (IBC), ETH Zürich, Otto-Stern-Weg 3, Zurich, Switzerland
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23
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Woolford JL, Baserga SJ. Ribosome biogenesis in the yeast Saccharomyces cerevisiae. Genetics 2013; 195:643-81. [PMID: 24190922 PMCID: PMC3813855 DOI: 10.1534/genetics.113.153197] [Citation(s) in RCA: 548] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 08/26/2013] [Indexed: 01/09/2023] Open
Abstract
Ribosomes are highly conserved ribonucleoprotein nanomachines that translate information in the genome to create the proteome in all cells. In yeast these complex particles contain four RNAs (>5400 nucleotides) and 79 different proteins. During the past 25 years, studies in yeast have led the way to understanding how these molecules are assembled into ribosomes in vivo. Assembly begins with transcription of ribosomal RNA in the nucleolus, where the RNA then undergoes complex pathways of folding, coupled with nucleotide modification, removal of spacer sequences, and binding to ribosomal proteins. More than 200 assembly factors and 76 small nucleolar RNAs transiently associate with assembling ribosomes, to enable their accurate and efficient construction. Following export of preribosomes from the nucleus to the cytoplasm, they undergo final stages of maturation before entering the pool of functioning ribosomes. Elaborate mechanisms exist to monitor the formation of correct structural and functional neighborhoods within ribosomes and to destroy preribosomes that fail to assemble properly. Studies of yeast ribosome biogenesis provide useful models for ribosomopathies, diseases in humans that result from failure to properly assemble ribosomes.
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Affiliation(s)
- John L. Woolford
- Department of Biological Sciences, Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Susan J. Baserga
- Molecular Biophysics and Biochemistry, Genetics and Therapeutic Radiology, Yale University, New Haven, Connecticut 06520-8024
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24
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Regulation of ribosome biogenesis by nucleostemin 3 promotes local and systemic growth in Drosophila. Genetics 2013; 194:101-15. [PMID: 23436180 DOI: 10.1534/genetics.112.149104] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Nucleostemin 3 (NS3) is an evolutionarily conserved protein with profound roles in cell growth and viability. Here we analyze cell-autonomous and non-cell-autonomous growth control roles of NS3 in Drosophila and demonstrate its GTPase activity using genetic and biochemical assays. Two null alleles of ns3, and RNAi, demonstrate the necessity of NS3 for cell autonomous growth. A hypomorphic allele highlights the hypersensitivity of neurons to lowered NS3 function. We propose that NS3 is the functional ortholog of yeast and human Lsg1, which promotes release of the nuclear export adapter from the large ribosomal subunit. Release of the adapter and its recycling to the nucleus are essential for sustained production of ribosomes. The ribosome biogenesis role of NS3 is essential for proper rates of translation in all tissues and is necessary for functions of growth-promoting neurons.
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25
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Fernández-Pevida A, Rodríguez-Galán O, Díaz-Quintana A, Kressler D, de la Cruz J. Yeast ribosomal protein L40 assembles late into precursor 60 S ribosomes and is required for their cytoplasmic maturation. J Biol Chem 2012; 287:38390-407. [PMID: 22995916 DOI: 10.1074/jbc.m112.400564] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most ribosomal proteins play important roles in ribosome biogenesis and function. Here, we have examined the contribution of the essential ribosomal protein L40 in these processes in the yeast Saccharomyces cerevisiae. Deletion of either the RPL40A or RPL40B gene and in vivo depletion of L40 impair 60 S ribosomal subunit biogenesis. Polysome profile analyses reveal the accumulation of half-mers and a moderate reduction in free 60 S ribosomal subunits. Pulse-chase, Northern blotting, and primer extension analyses in the L40-depleted strain clearly indicate that L40 is not strictly required for the precursor rRNA (pre-rRNA) processing reactions but contributes to optimal 27 SB pre-rRNA maturation. Moreover, depletion of L40 hinders the nucleo-cytoplasmic export of pre-60 S ribosomal particles. Importantly, all these defects most likely appear as the direct consequence of impaired Nmd3 and Rlp24 release from cytoplasmic pre-60 S ribosomal subunits and their inefficient recycling back into the nucle(ol)us. In agreement, we show that hemagglutinin epitope-tagged L40A assembles in the cytoplasm into almost mature pre-60 S ribosomal particles. Finally, we have identified that the hemagglutinin epitope-tagged L40A confers resistance to sordarin, a translation inhibitor that impairs the function of eukaryotic elongation factor 2, whereas the rpl40a and rpl40b null mutants are hypersensitive to this antibiotic. We conclude that L40 is assembled at a very late stage into pre-60 S ribosomal subunits and that its incorporation into 60 S ribosomal subunits is a prerequisite for subunit joining and may ensure proper functioning of the translocation process.
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Abstract
Exchange of macromolecules between the nucleus and cytoplasm is a key regulatory event in the expression of a cell's genome. This exchange requires a dedicated transport system: (1) nuclear pore complexes (NPCs), embedded in the nuclear envelope and composed of proteins termed nucleoporins (or "Nups"), and (2) nuclear transport factors that recognize the cargoes to be transported and ferry them across the NPCs. This transport is regulated at multiple levels, and the NPC itself also plays a key regulatory role in gene expression by influencing nuclear architecture and acting as a point of control for various nuclear processes. Here we summarize how the yeast Saccharomyces has been used extensively as a model system to understand the fundamental and highly conserved features of this transport system, revealing the structure and function of the NPC; the NPC's role in the regulation of gene expression; and the interactions of transport factors with their cargoes, regulatory factors, and specific nucleoporins.
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27
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Integrity and function of the Saccharomyces cerevisiae spindle pole body depends on connections between the membrane proteins Ndc1, Rtn1, and Yop1. Genetics 2012; 192:441-55. [PMID: 22798490 DOI: 10.1534/genetics.112.141465] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The nuclear envelope in Saccharomyces cerevisiae harbors two essential macromolecular protein assemblies: the nuclear pore complexes (NPCs) that enable nucleocytoplasmic transport, and the spindle pole bodies (SPBs) that mediate chromosome segregation. Previously, based on metazoan and budding yeast studies, we reported that reticulons and Yop1/DP1 play a role in the early steps of de novo NPC assembly. Here, we examined if Rtn1 and Yop1 are required for SPB function in S. cerevisiae. Electron microscopy of rtn1Δ yop1Δ cells revealed lobular abnormalities in SPB structure. Using an assay that monitors lateral expansion of the SPB central layer, we found that rtn1Δ yop1Δ SPBs had decreased connections to the NE compared to wild type, suggesting that SPBs are less stable in the NE. Furthermore, large budded rtn1Δ yop1Δ cells exhibited a high incidence of short mitotic spindles, which were frequently misoriented with respect to the mother-daughter axis. This correlated with cytoplasmic microtubule defects. We found that overexpression of the SPB insertion factors NDC1, MPS2, or BBP1 rescued the SPB defects observed in rtn1Δ yop1Δ cells. However, only overexpression of NDC1, which is also required for NPC biogenesis, rescued both the SPB and NPC associated defects. Rtn1 and Yop1 also physically interacted with Ndc1 and other NPC membrane proteins. We propose that NPC and SPB biogenesis are altered in cells lacking Rtn1 and Yop1 due to competition between these complexes for Ndc1, an essential common component of both NPCs and SPBs.
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28
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The mRNA export factor Npl3 mediates the nuclear export of large ribosomal subunits. EMBO Rep 2011; 12:1024-31. [PMID: 21852791 DOI: 10.1038/embor.2011.155] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 06/21/2011] [Accepted: 06/28/2011] [Indexed: 12/27/2022] Open
Abstract
The nuclear export of large ribonucleoparticles is complex and requires specific transport factors. Messenger RNAs are exported through the RNA-binding protein Npl3 and the interacting export receptor Mex67. Export of large ribosomal subunits also requires Mex67; however, in this case, Mex67 binds directly to the 5S ribosomal RNA (rRNA) and does not require the Npl3 adaptor. Here, we have discovered a new function of Npl3 in mediating the export of pre-60S ribosomal subunit independently of Mex67. Npl3 interacts with the 25S rRNA, ribosomal and ribosome-associated proteins, as well as with the nuclear pore complex. Mutations in NPL3 lead to export defects of the large subunit and genetic interactions with other pre-60S export factors.
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29
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Rhodin MHJ, Dinman JD. A flexible loop in yeast ribosomal protein L11 coordinates P-site tRNA binding. Nucleic Acids Res 2010; 38:8377-89. [PMID: 20705654 PMCID: PMC3001080 DOI: 10.1093/nar/gkq711] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 07/26/2010] [Accepted: 07/27/2010] [Indexed: 11/12/2022] Open
Abstract
High-resolution structures reveal that yeast ribosomal protein L11 and its bacterial/archael homologs called L5 contain a highly conserved, basically charged internal loop that interacts with the peptidyl-transfer RNA (tRNA) T-loop. We call this the L11 'P-site loop'. Chemical protection of wild-type ribosome shows that that the P-site loop is inherently flexible, i.e. it is extended into the ribosomal P-site when this is unoccupied by tRNA, while it is retracted into the terminal loop of 25S rRNA Helix 84 when the P-site is occupied. To further analyze the function of this structure, a series of mutants within the P-site loop were created and analyzed. A mutant that favors interaction of the P-site loop with the terminal loop of Helix 84 promoted increased affinity for peptidyl-tRNA, while another that favors its extension into the ribosomal P-site had the opposite effect. The two mutants also had opposing effects on binding of aa-tRNA to the ribosomal A-site, and downstream functional effects were observed on translational fidelity, drug resistance/hypersensitivity, virus maintenance and overall cell growth. These analyses suggest that the L11 P-site loop normally helps to optimize ribosome function by monitoring the occupancy status of the ribosomal P-site.
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Affiliation(s)
| | - Jonathan D. Dinman
- Department of Cell Biology and Molecular Genetics, Microbiology Building Room 2135, University of Maryland, College Park, MD 20742, USA
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30
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Wild T, Horvath P, Wyler E, Widmann B, Badertscher L, Zemp I, Kozak K, Csucs G, Lund E, Kutay U. A protein inventory of human ribosome biogenesis reveals an essential function of exportin 5 in 60S subunit export. PLoS Biol 2010; 8:e1000522. [PMID: 21048991 PMCID: PMC2964341 DOI: 10.1371/journal.pbio.1000522] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 09/03/2010] [Indexed: 12/20/2022] Open
Abstract
The assembly of ribosomal subunits in eukaryotes is a complex, multistep process so far mostly studied in yeast. In S. cerevisiae, more than 200 factors including ribosomal proteins and trans-acting factors are required for the ordered assembly of 40S and 60S ribosomal subunits. To date, only few human homologs of these yeast ribosome synthesis factors have been characterized. Here, we used a systematic RNA interference (RNAi) approach to analyze the contribution of 464 candidate factors to ribosomal subunit biogenesis in human cells. The screen was based on visual readouts, using inducible, fluorescent ribosomal proteins as reporters. By performing computer-based image analysis utilizing supervised machine-learning techniques, we obtained evidence for a functional link of 153 human proteins to ribosome synthesis. Our data show that core features of ribosome assembly are conserved from yeast to human, but differences exist for instance with respect to 60S subunit export. Unexpectedly, our RNAi screen uncovered a requirement for the export receptor Exportin 5 (Exp5) in nuclear export of 60S subunits in human cells. We show that Exp5, like the known 60S exportin Crm1, binds to pre-60S particles in a RanGTP-dependent manner. Interference with either Exp5 or Crm1 function blocks 60S export in both human cells and frog oocytes, whereas 40S export is compromised only upon inhibition of Crm1. Thus, 60S subunit export is dependent on at least two RanGTP-binding exportins in vertebrate cells.
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Affiliation(s)
- Thomas Wild
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- Molecular Life Science Ph.D. Program, Zurich, Switzerland
| | - Peter Horvath
- Light Microscopy Center, RISC, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Emanuel Wyler
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- Molecular Life Science Ph.D. Program, Zurich, Switzerland
| | - Barbara Widmann
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- Molecular Life Science Ph.D. Program, Zurich, Switzerland
| | - Lukas Badertscher
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- Molecular Life Science Ph.D. Program, Zurich, Switzerland
| | - Ivo Zemp
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Karol Kozak
- Light Microscopy Center, RISC, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Gabor Csucs
- Light Microscopy Center, RISC, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Elsebet Lund
- University of Wisconsin, Madison, Wisconsin, United States of America
| | - Ulrike Kutay
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
- * E-mail:
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31
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Panse VG, Johnson AW. Maturation of eukaryotic ribosomes: acquisition of functionality. Trends Biochem Sci 2010; 35:260-6. [PMID: 20137954 DOI: 10.1016/j.tibs.2010.01.001] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 01/03/2010] [Accepted: 01/04/2010] [Indexed: 11/29/2022]
Abstract
In eukaryotic cells, ribosomes are pre-assembled in the nucleus and exported to the cytoplasm where they undergo final maturation. This involves the release of trans-acting shuttling factors, transport factors, incorporation of the remaining ribosomal proteins, and final rRNA processing steps. Recent work, particularly on the large (60S) ribosomal subunit, has confirmed that the 60S subunit is exported from the nucleus in a functionally inactive state. Its arrival in the cytoplasm triggers events that render it translationally competent. Here we focus on these cytoplasmic maturation events and speculate why eukaryotic cells have evolved such an elaborate maturation pathway.
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Dominant mutations in the late 40S biogenesis factor Ltv1 affect cytoplasmic maturation of the small ribosomal subunit in Saccharomyces cerevisiae. Genetics 2010; 185:199-209. [PMID: 20215468 DOI: 10.1534/genetics.110.115584] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In eukaryotes, 40S and 60S ribosomal subunits are assembled in the nucleus from rRNAs and ribosomal proteins, exported as premature complexes, and processed in final maturation steps in the cytoplasm. Ltv1 is a conserved 40S ribosome biogenesis factor that interacts with pre-40S complexes in vivo and is proposed to function in yeast in nuclear export. Cells lacking LTV1 grow slowly and are significantly impaired in mature 40S subunit production. Here we show that mutation or deletion of a putative nuclear export sequence in LTV1 is strongly dominant negative, but the protein does not accumulate in the nucleus, as expected for a mutation affecting export. In fact, most of the mutant protein is cytoplasmic and associated with pre-40S subunits. Cells expressing mutant Ltv1 have a 40S biogenesis defect, accumulate 20S rRNA in the cytoplasm as detected by FISH, and retain the late-acting biogenesis factor Tsr1 in the cytoplasm. Finally, overexpression of mutant Ltv1 is associated with nuclear retention of 40S subunit marker proteins, RpS2-GFP and RpS3-GFP. We suggest that the proximal consequence of these LTV1 mutations is inhibition of the cytoplasmic maturation of 40S subunits and that nuclear retention of pre-40S subunits is a downstream consequence of the failure to release and recycle critical factors back to the nucleus.
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33
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Cisterna B, Biggiogera M. Ribosome biogenesis: from structure to dynamics. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 284:67-111. [PMID: 20875629 DOI: 10.1016/s1937-6448(10)84002-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In this chapter we describe the status of the research concerning the nucleolus, the major nuclear body. The nucleolus has been recognized as a dynamic organelle with many more functions than one could imagine. In fact, in addition to its fundamental role in the biogenesis of preribosomes, the nucleolus takes part in many other cellular processes and functions, such as the cell-cycle control and the p53 pathway: the direct or indirect involvement of the nucleolus in these various processes makes it sensitive to their alteration. Moreover, it is worth noting that the different nucleolar factors participating to independent mechanisms show different dynamics of association/disassociation with the nucleolar body.
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Affiliation(s)
- Barbara Cisterna
- Laboratory of Cell Biology and Neurobiology, Department of Animal Biology, University of Pavia, Pavia, Italy
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34
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Kemmler S, Occhipinti L, Veisu M, Panse VG. Yvh1 is required for a late maturation step in the 60S biogenesis pathway. ACTA ACUST UNITED AC 2009; 186:863-80. [PMID: 19797079 PMCID: PMC2753168 DOI: 10.1083/jcb.200904111] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The step by step assembly process from preribosome in the nucleus to translation-competent 60S ribosome subunit in the cytoplasm is revealed (also see Lo et al. in this issue). Before entering translation, preribosomal particles undergo sequential late maturation steps. In the case of pre-60S particles, these steps involve the release of shuttling maturation factors and transport receptors. In this study, we report a new maturation step in the 60S biogenesis pathway in budding yeast. We show that efficient release of the nucleolar/nuclear ribosomal-like protein Mrt4 (homologous to the acidic ribosomal P-protein Rpp0) from pre-60S particles requires the highly conserved protein Yvh1, which associates only with late pre-60S particles. Cell biological and biochemical analyses reveal that Mrt4 fails to dissociate from late pre-60S particles in yvh1Δ cells, inducing a delay in nuclear pre–ribosomal RNA processing and a pre-60S export defect in yvh1Δ cells. Moreover, we have isolated gain of function alleles of Mrt4 that specifically bypass the requirement for Yvh1 and rescue all yvh1Δ-associated phenotypes. Together, our data suggest that Yvh1-mediated release of Mrt4 precedes cytoplasmic loading of Rpp0 on pre-60S particles and is an obligatory late step toward construction of translation-competent 60S subunits.
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Affiliation(s)
- Stefan Kemmler
- Institute of Biochemistry, ETH Zürich, CH-8093 Zürich, Switzerland
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35
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Suzuki T, Mochizuki K, Goda T. Localized expression of genes related to carbohydrate and lipid absorption along the crypt-villus axis of rat jejunum. Biochim Biophys Acta Gen Subj 2009; 1790:1624-35. [PMID: 19715743 DOI: 10.1016/j.bbagen.2009.08.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2008] [Revised: 08/13/2009] [Accepted: 08/18/2009] [Indexed: 02/07/2023]
Abstract
BACKGROUND Enterocytes of the jejunum express several genes related to digestion/absorption of nutrients and ions when these cells rapidly differentiate from crypt to villus cells. However, it is unknown whether the distribution of extensive gene expression along the villus-crypt axis of the jejunum is altered during differentiation. METHODS We investigated the changes in jejunal gene expression during differentiation from crypt to villus cells in rats using DNA microarray analysis on cryostat sections of the villus-crypt columns. RESULTS During differentiation, the expression of many genes related to cell growth rapidly decreased, while expression of genes related to digestion and absorption of nutrients and ions increased. Expression of a subset of genes related to the digestion and absorption of starch and sucrose was highest at the middle of the villi, whereas expression of genes related to dietary fat absorption was highest at the top of the villi. Several transcriptional factors such as Pdx1, Foxa2 and Thra were expressed in the crypt, whereas Klf15 was highly expressed during the crypt-villus transition. Expression of Klf4 and Pparg was highest at the top of the villi. CONCLUSIONS Subsets of genes related to the digestion and absorption of starch/sucrose and dietary fat as well as their transcriptional factors/co-factors are expressed in the specific locations along the crypt-villus axis. GENERAL SIGNIFICANCE The jejunum may absorb nutrients effectively by simultaneously expressing subsets of genes along the villus-crypt axis.
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Affiliation(s)
- Takuji Suzuki
- Laboratory of Nutritional Physiology, The University of Shizuoka Graduate School of Nutritional and Environmental Sciences and Global COE, Shizuoka, Japan
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36
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Neef DW, Thiele DJ. Enhancer of decapping proteins 1 and 2 are important for translation during heat stress in Saccharomyces cerevisiae. Mol Microbiol 2009; 73:1032-42. [PMID: 19682251 DOI: 10.1111/j.1365-2958.2009.06827.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In mammalian and Drosophila cells, heat stress strongly reduces general protein translation while activating cap-independent translation mechanisms to promote the expression of stress-response proteins. In contrast, in Saccharomyces cerevisiae general translation is only mildly and transiently reduced by heat stress and cap-independent translation mechanisms have not been correlated with the heat stress response. Recently we have identified direct target genes of the heat shock transcription factor (HSF), including genes encoding proteins thought to be important for general translation. One gene activated by HSF during heat stress encodes the enhancer of decapping protein, Edc2, previously shown to enhance mRNA decapping under conditions when the decapping machinery is limited. In this report we show that strains lacking Edc2, as well as the paralogous protein Edc1, are compromised for growth under persistent heat stress. This growth deficiency can be rescued by expression of a mutant Edc1 protein deficient in mRNA decapping indicative of a decapping independent function during heat stress. Yeast strains lacking Edc1 and Edc2 are also sensitive to the pharmacological inhibitor of translation paromomycin and exposure to heat stress and paromomycin functions synergistically to reduce yeast viability, suggesting that in the absence of Edc1 and Edc2 translation is compromised under heat stress conditions. Strains lacking Edc1 and Edc2 have significantly reduced rates of protein translation during growth under heat stress conditions, but not under normal growth conditions. We propose that Edc1 and the stress responsive isoform Edc2 play important roles in protein translation during stress.
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Affiliation(s)
- Daniel W Neef
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
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37
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Zemp I, Wild T, O'Donohue MF, Wandrey F, Widmann B, Gleizes PE, Kutay U. Distinct cytoplasmic maturation steps of 40S ribosomal subunit precursors require hRio2. J Cell Biol 2009; 185:1167-80. [PMID: 19564402 PMCID: PMC2712965 DOI: 10.1083/jcb.200904048] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Accepted: 06/02/2009] [Indexed: 01/04/2023] Open
Abstract
During their biogenesis, 40S ribosomal subunit precursors are exported from the nucleus to the cytoplasm, where final maturation occurs. In this study, we show that the protein kinase human Rio2 (hRio2) is part of a late 40S preribosomal particle in human cells. Using a novel 40S biogenesis and export assay, we analyzed the contribution of hRio2 to late 40S maturation. Although hRio2 is not absolutely required for pre-40S export, deletion of its binding site for the export receptor CRM1 decelerated the kinetics of this process. Moreover, in the absence of hRio2, final cytoplasmic 40S maturation is blocked because the recycling of several trans-acting factors and cytoplasmic 18S-E precursor ribosomal RNA (rRNA [pre-rRNA]) processing are defective. Intriguingly, the physical presence of hRio2 but not its kinase activity is necessary for the release of hEnp1 from cytoplasmic 40S precursors. In contrast, hRio2 kinase activity is essential for the recycling of hDim2, hLtv1, and hNob1 as well as for 18S-E pre-rRNA processing. Thus, hRio2 is involved in late 40S maturation at several distinct steps.
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Affiliation(s)
- Ivo Zemp
- Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland
- Molecular Life Sciences Program, Life Science Zurich Graduate School, University of Zurich, CH-8057 Zurich, Switzerland
| | - Thomas Wild
- Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland
- Molecular Life Sciences Program, Life Science Zurich Graduate School, University of Zurich, CH-8057 Zurich, Switzerland
| | - Marie-Françoise O'Donohue
- Laboratoire de Biologie Moléculaire Eucaryote, Centre National de la Recherche Scientifique, Université Paul Sabatier, Université de Toulouse, F-31062 Toulouse, Cedex 4, France
| | - Franziska Wandrey
- Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland
- Molecular Life Sciences Program, Life Science Zurich Graduate School, University of Zurich, CH-8057 Zurich, Switzerland
| | - Barbara Widmann
- Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland
- Molecular Life Sciences Program, Life Science Zurich Graduate School, University of Zurich, CH-8057 Zurich, Switzerland
| | - Pierre-Emmanuel Gleizes
- Laboratoire de Biologie Moléculaire Eucaryote, Centre National de la Recherche Scientifique, Université Paul Sabatier, Université de Toulouse, F-31062 Toulouse, Cedex 4, France
| | - Ulrike Kutay
- Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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38
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Perreault A, Bellemer C, Bachand F. Nuclear export competence of pre-40S subunits in fission yeast requires the ribosomal protein Rps2. Nucleic Acids Res 2008; 36:6132-42. [PMID: 18820293 PMCID: PMC2577348 DOI: 10.1093/nar/gkn625] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Ribosome biogenesis is an evolutionarily conserved pathway that requires ribosomal and nonribosomal proteins. Here, we investigated the role of the ribosomal protein S2 (Rps2) in fission yeast ribosome synthesis. As for many budding yeast ribosomal proteins, Rps2 was essential for cell viability in fission yeast and the genetic depletion of Rps2 caused a complete inhibition of 40S ribosomal subunit production. The pattern of pre-rRNA processing upon depletion of Rps2 revealed a reduction of 27SA2 pre-rRNAs and the concomitant production of 21S rRNA precursors, consistent with a role for Rps2 in efficient cleavage at site A2 within the 32S pre-rRNA. Importantly, kinetics of pre-rRNA accumulation as determined by rRNA pulse-chases assays indicated that a small fraction of 35S precursors matured into 20S-containing particles, suggesting that most 40S precursors were rapidly degraded in the absence of Rps2. Analysis of steady-state RNA levels revealed that some pre-40S particles were produced in Rps2-depleted cells, but that these precursors were retained in the nucleolus. Our findings suggest a role for Rps2 in a mechanism that monitors pre-40S export competence.
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Affiliation(s)
- Audrey Perreault
- RNA Group, Department of Biochemistry, Université de Sherbrooke, Québec, Canada
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39
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Bolger TA, Folkmann AW, Tran EJ, Wente SR. The mRNA export factor Gle1 and inositol hexakisphosphate regulate distinct stages of translation. Cell 2008; 134:624-33. [PMID: 18724935 DOI: 10.1016/j.cell.2008.06.027] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 05/13/2008] [Accepted: 06/10/2008] [Indexed: 10/21/2022]
Abstract
Gene expression requires proper messenger RNA (mRNA) export and translation. However, the functional links between these consecutive steps have not been fully defined. Gle1 is an essential, conserved mRNA export factor whose export function is dependent on the small molecule inositol hexakisphosphate (IP(6)). Here, we show that both Gle1 and IP(6) are required for efficient translation termination in Saccharomyces cerevisiae and that Gle1 interacts with termination factors. In addition, Gle1 has a conserved physical association with the initiation factor eIF3, and gle1 mutants display genetic interactions with the eIF3 mutant nip1-1. Strikingly, gle1 mutants have defects in initiation, whereas strains lacking IP(6) do not. We propose that Gle1 functions together with IP(6) and the DEAD-box protein Dbp5 to regulate termination. However, Gle1 also independently mediates initiation. Thus, Gle1 is uniquely positioned to coordinate the mRNA export and translation mechanisms. These results directly impact models for perturbation of Gle1 function in pathophysiology.
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Affiliation(s)
- Timothy A Bolger
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, U-3209 MRBIII, 465 21st Avenue South, Nashville, TN 37232-8240, USA
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40
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Chen IJ, Wang IA, Tai LR, Lin A. The role of expansion segment of human ribosomal protein L35 in nuclear entry, translation activity, and endoplasmic reticulum docking. Biochem Cell Biol 2008; 86:271-7. [PMID: 18523488 DOI: 10.1139/o08-032] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The phylogenic alignment of homologous L35 protein suggests that human large subunit ribosomal protein L35 carries a 54 aa eukaryotic expansion segment (ES) at the C-terminal end. Within this ES, the first 25 amino acid residues were found to be essential for the nuclear import of the protein. The last 29 residues of the ES were shown to be uninvolved in the ribosome's structural and translational functions, although this region proved to be one of the contact sites for ribosomal docking to endoplasmic reticulum, as evident from the results of an in vivo recombinant ribosome analysis.
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Affiliation(s)
- In-Jay Chen
- Institute of Genetics, National Yang-Ming University, Shih-Pai, Taipei 112, Taiwan, ROC
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41
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Hung NJ, Lo KY, Patel SS, Helmke K, Johnson AW. Arx1 is a nuclear export receptor for the 60S ribosomal subunit in yeast. Mol Biol Cell 2007; 19:735-44. [PMID: 18077551 DOI: 10.1091/mbc.e07-09-0968] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We previously showed that nuclear export of the large (60S) ribosomal subunit relies on Nmd3 in a Crm1-dependent manner. Recently the general mRNA export factor, the Mtr2/Mex67 heterodimer, was shown to act as an export receptor in parallel with Crm1. These observations raise the possibility that nuclear export of the 60S subunit in Saccharomyces cerevisiae requires multiple export receptors. Here, we show that the previously characterized 60S subunit biogenesis factor, Arx1, also acts as an export receptor for the 60S subunit. We found that deletion of ARX1 was synthetic lethal with nmd3 and mtr2 mutants and was synthetic sick with several nucleoporin mutants. Deletion of ARX1 led to accumulation of pre-60S particles in the nucleus that were enriched for Nmd3, Crm1, Mex67, and Mtr2, suggesting that in the absence of Arx1, 60S export is impaired even though the subunit is loaded with export receptors. Finally, Arx1 interacted with several nucleoporins in yeast two-hybrid as well as in vitro assays. These results show that Arx1 can directly bridge the interaction between the pre-60S particle and the NPC and thus is a third export receptor for the 60S subunit in yeast.
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Affiliation(s)
- Nai-Jung Hung
- Section of Molecular Genetics and Microbiology and the Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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42
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Abstract
The transport of RNA molecules from the nucleus to the cytoplasm is fundamental for gene expression. The different RNA species that are produced in the nucleus are exported through the nuclear pore complexes via mobile export receptors. Small RNAs (such as tRNAs and microRNAs) follow relatively simple export routes by binding directly to export receptors. Large RNAs (such as ribosomal RNAs and mRNAs) assemble into complicated ribonucleoprotein (RNP) particles and recruit their exporters via class-specific adaptor proteins. Export of mRNAs is unique as it is extensively coupled to transcription (in yeast) and splicing (in metazoa). Understanding the mechanisms that connect RNP formation with export is a major challenge in the field.
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Affiliation(s)
- Alwin Köhler
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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43
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Alcázar-Román AR, Wente SR. Inositol polyphosphates: a new frontier for regulating gene expression. Chromosoma 2007; 117:1-13. [DOI: 10.1007/s00412-007-0126-4] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2007] [Revised: 09/12/2007] [Accepted: 09/13/2007] [Indexed: 10/22/2022]
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44
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Dez C, Dlakić M, Tollervey D. Roles of the HEAT repeat proteins Utp10 and Utp20 in 40S ribosome maturation. RNA (NEW YORK, N.Y.) 2007; 13:1516-27. [PMID: 17652137 PMCID: PMC1950751 DOI: 10.1261/rna.609807] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A family of HEAT-repeat containing ribosome synthesis factors was previously identified in Saccharomyces cerevisiae. We report the detailed characterization of two of these factors, Utp10 and Utp20, which were initially identified as components of the small subunit processome. Coprecipitation analyses confirmed the association of Utp10 and Utp20 with U3 snoRNA and the early pre-rRNA processing intermediates. Particularly strong association was seen with aberrant processing intermediates, which may help target these RNAs for degradation. Genetic depletion of either protein inhibited the early pre-rRNA processing steps in 18S rRNA maturation but had little effect on pre-rRNA transcription or synthesis of the 25S or 5.8S rRNAs. The absence of the poly(A) polymerase Trf5, a component of the TRAMP5 complex and exosome cofactor, led to stabilization of the aberrant 23S RNA in strains depleted of Utp10 or Utp20. In the case of Utp10, 20S pre-rRNA synthesis was also modestly increased by this loss of surveillance activity.
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MESH Headings
- Models, Molecular
- RNA Processing, Post-Transcriptional/physiology
- RNA, Ribosomal, 18S/biosynthesis
- RNA, Small Nucleolar/genetics
- RNA, Small Nucleolar/physiology
- Repetitive Sequences, Amino Acid
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/physiology
- Ribonucleoproteins, Small Nucleolar/genetics
- Ribonucleoproteins, Small Nucleolar/physiology
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/growth & development
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins/genetics
- Saccharomyces cerevisiae Proteins/physiology
- Signal Transduction/genetics
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Affiliation(s)
- Christophe Dez
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Scotland
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45
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Zemp I, Kutay U. Nuclear export and cytoplasmic maturation of ribosomal subunits. FEBS Lett 2007; 581:2783-93. [PMID: 17509569 DOI: 10.1016/j.febslet.2007.05.013] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 05/06/2007] [Indexed: 01/20/2023]
Abstract
Based on the characterization of ribosome precursor particles and associated trans-acting factors, a biogenesis pathway for the 40S and 60S subunits has emerged. After nuclear synthesis and assembly steps, pre-ribosomal subunits are exported through the nuclear pore complex in a Crm1- and RanGTP-dependent manner. Subsequent cytoplasmic biogenesis steps of pre-60S particles include the facilitated release of several non-ribosomal proteins, yielding fully functional 60S subunits. Cytoplasmic maturation of 40S subunit precursors includes rRNA dimethylation and pre-rRNA cleavage, allowing 40S subunits to achieve translation competence. We review current knowledge of nuclear export and cytoplasmic maturation of ribosomal subunits.
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Affiliation(s)
- Ivo Zemp
- Institute of Biochemistry, HPM F11.1, Schafmattstr. 18, ETH Zurich, 8093 Zurich, Switzerland
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46
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West M, Hedges JB, Lo KY, Johnson AW. Novel interaction of the 60S ribosomal subunit export adapter Nmd3 at the nuclear pore complex. J Biol Chem 2007; 282:14028-37. [PMID: 17347149 DOI: 10.1074/jbc.m700256200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Nuclear export of the large (60S) ribosomal subunit depends on the adapter protein Nmd3 to provide a nuclear export signal (NES). The leucine-rich NES is recognized by the export receptor Crm1 to mediate export via interaction with the nuclear pore complex (NPC). Here, we show that certain mutant Nmd3 proteins that are impaired for binding to the 60S subunit accumulate at the nuclear envelope. These mutant proteins also show enhanced binding to Crm1, both in vivo and in vitro. Although their interaction with the NPC is dependent on recognition of the NES by Crm1, their interaction with Crm1 is not strictly dependent on RanGTP. Using a collection of GFP-tagged nucleoporin mutants, we identified several nucleoporins, including components of the Nup82 complex that copurified with the mutant Nmd3. The Nup82 complex is on the cytoplasmic face of the NPC and has previously been shown to be important as a terminal binding site for Crm1-mediated export. Mutations in the Nup82 complex led to accumulation of wild-type Nmd3 in the nucleoplasm, suggesting that the interaction of mutant Nmd3 with the Nup82 complex reflects a defect in the bona fide export pathway for the 60S subunit. These results suggest that in the absence of the ribosome, Nmd3 is not efficiently released from Crm1 at the NPC.
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Affiliation(s)
- Matthew West
- Section of Molecular Genetics and Microbiology and the Institute for Cellular and Molecular Biology, the University of Texas, Austin, TX 78712, USA
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47
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Gardiner FC, Costa R, Ayscough KR. Nucleocytoplasmic trafficking is required for functioning of the adaptor protein Sla1p in endocytosis. Traffic 2007; 8:347-58. [PMID: 17286805 PMCID: PMC1989034 DOI: 10.1111/j.1600-0854.2007.00534.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Dual localization of proteins at the plasma membrane and within the nucleus has been reported in mammalian cells. Among these proteins are those involved in cell adhesion structures and in clathrin-mediated endocytosis. In the case of endocytic proteins, trafficking to the nucleus is not known to play a role in their endocytic function. Here, we show localization of the yeast endocytic adaptor protein Sla1p to the nucleus as well as to the cell cortex and we demonstrate the importance of specific regions of Sla1p for this nuclear localization. A role for specific karyopherins (importins and exportins) in Sla1p nuclear localization is revealed. Furthermore, endocytosis of Sla1p-dependent cargo is defective in three strains with karyopherin mutations. Finally, we investigate possible functions for nuclear trafficking of endocytic proteins. Our data reveal for the first time that nuclear transport of endocytic proteins is important for functional endocytosis in Saccharomyces cerevisiae. We determine the mechanism, involving an alpha/beta importin pair, that facilitates uptake of Sla1p and demonstrate that nuclear transport is required for the functioning of Sla1p during endocytosis.
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Affiliation(s)
- Fiona C. Gardiner
- Department of Molecular Biology and Biotechnology, University of Sheffield Firth Court, Western Bank Sheffield, S10 2TN Tel: +44 114 222 2309 Fax: +44 114 222 2800
| | - Rosaria Costa
- Department of Molecular Biology and Biotechnology, University of Sheffield Firth Court, Western Bank Sheffield, S10 2TN Tel: +44 114 222 2309 Fax: +44 114 222 2800
| | - Kathryn R. Ayscough
- Department of Molecular Biology and Biotechnology, University of Sheffield Firth Court, Western Bank Sheffield, S10 2TN Tel: +44 114 222 2309 Fax: +44 114 222 2800
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48
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Oeffinger M, Fatica A, Rout MP, Tollervey D. Yeast Rrp14p is required for ribosomal subunit synthesis and for correct positioning of the mitotic spindle during mitosis. Nucleic Acids Res 2007; 35:1354-66. [PMID: 17272295 PMCID: PMC1849896 DOI: 10.1093/nar/gkl824] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Here we report that Rrp14p/Ykl082p is associated with pre-60S particles and to a lesser extent with earlier 90S pre-ribosomes. Depletion of Rrp14p inhibited pre-rRNA synthesis on both the 40S and 60S synthesis pathways. Synthesis of the 20S precursor to the 18S rRNA was largely blocked, as was maturation of the 27SB pre-rRNA to the 5.8S and 25S rRNAs. Unexpectedly, Rrp14p-depleted cells also showed apparently specific cell-cycle defects. Following release from synchronization in S phase, Rrp14p-depleted cells uniformly arrested in metaphase with short mitotic spindles that were frequently incorrectly aligned with the site of bud formation. In the absence of Bub2p, which is required for the spindle orientation checkpoint, this metaphase arrest was not seen in Rrp14p-depleted cells, which then arrested with multiple buds, several SPBs and binucleate mother cells. These data suggest that Rrp14p may play some role in cell polarity and/or spindle positioning, in addition to its function in ribosome synthesis.
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Affiliation(s)
| | - Alessandro Fatica
- Wellcome Trust Centre for Cell Biology, University of EdinburghEdinburgh EH9 3JR, Scotland, UK
- Department of Genetics and Molecular Biology, University of Rome ‘La Sapienza’P. Aldo Moro, 5, 00185 Rome, Italy
| | - Michael P. Rout
- Rockefeller University, 1230 York AvenueNew York, NY10021, USA
| | - David Tollervey
- Wellcome Trust Centre for Cell Biology, University of EdinburghEdinburgh EH9 3JR, Scotland, UK
- To whom correspondence should be addressed. Tel: +44 131 650 7092; Fax: +44 131 650 7040;
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49
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Zanelli CF, Maragno ALC, Gregio APB, Komili S, Pandolfi JR, Mestriner CA, Lustri WR, Valentini SR. eIF5A binds to translational machinery components and affects translation in yeast. Biochem Biophys Res Commun 2006; 348:1358-66. [PMID: 16914118 DOI: 10.1016/j.bbrc.2006.07.195] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Accepted: 07/28/2006] [Indexed: 11/20/2022]
Abstract
The putative translation factor eIF5A is essential for cell viability and is highly conserved from archebacteria to mammals. Although this protein was originally identified as a translation initiation factor, subsequent experiments did not support a role for eIF5A in general translation. In this work, we demonstrate that eIF-5A interacts with structural components of the 80S ribosome, as well as with the translation elongation factor 2 (eEF2). Moreover, eIF5A is further shown to cofractionate with monosomes in a translation-dependent manner. Finally, eIF5A mutants show altered polysome profiles and are sensitive to translation inhibitors. Our results re-establish a function for eIF5A in translation and suggest a role for this factor in translation elongation instead of translation initiation.
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Affiliation(s)
- Cleslei F Zanelli
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Araraquara, SP 14801-902, Brazil
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50
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Seiser RM, Sundberg AE, Wollam BJ, Zobel-Thropp P, Baldwin K, Spector MD, Lycan DE. Ltv1 is required for efficient nuclear export of the ribosomal small subunit in Saccharomyces cerevisiae. Genetics 2006; 174:679-91. [PMID: 16888326 PMCID: PMC1602086 DOI: 10.1534/genetics.106.062117] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Accepted: 07/31/2006] [Indexed: 01/28/2023] Open
Abstract
In eukaryotes, 40S and 60S ribosomal subunits are assembled in the nucleus and exported to the cytoplasm independently of one another. Nuclear export of the 60S requires the adapter protein Nmd3, but no analogous adapter has been identified for the 40S. Ltv1 is a nonessential, nonribosomal protein that is required for 40S subunit biogenesis in yeast. Cells lacking LTV1 grow slowly, are hypersensitive to inhibitors of protein synthesis, and produce about half as many 40S subunits as do wild-type cells. Ltv1 interacts with Crm1, co-sediments in sucrose gradients with 43S/40S subunits, and copurifies with late 43S particles. Here we show that Ltv1 shuttles between nucleus and cytoplasm in a Crm1-dependent manner and that it contains a functional NES that is sufficient to direct the export of an NLS-containing reporter. Small subunit export is reduced in Deltaltv1 mutants, as judged by the altered distribution of the 5'-ITS1 rRNA and the 40S ribosomal protein RpS3. Finally, we show a genetic interaction between LTV1 and YRB2, a gene that encodes a Ran-GTP-, Crm1-binding protein that facilitates the small subunit export. We propose that Ltv1 functions as one of several possible adapter proteins that link the nuclear export machinery to the small subunit.
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Affiliation(s)
- Robert M Seiser
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, IL 60605, USA
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