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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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2
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Lin S, Rajan S, Lemberg S, Altawil M, Anderson K, Bryant R, Cappeta S, Chin B, Hamdan I, Hamer A, Hyzny R, Karp A, Lee D, Lim A, Nayak M, Palaniappan V, Park S, Satishkumar S, Seth A, Sri Dasari U, Toppari E, Vyas A, Walker J, Weston E, Zafar A, Zielke C, Mahabeleshwar GH, Tartakoff AM. Production of nascent ribosome precursors within the nucleolar microenvironment of Saccharomyces cerevisiae. Genetics 2022; 221:iyac070. [PMID: 35657327 PMCID: PMC9252279 DOI: 10.1093/genetics/iyac070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
35S rRNA transcripts include a 5'-external transcribed spacer followed by rRNAs of the small and large ribosomal subunits. Their processing yields massive precursors that include dozens of assembly factor proteins. In Saccharomyces cerevisiae, nucleolar assembly factors form 2 coaxial layers/volumes around ribosomal DNA. Most of these factors are cyclically recruited from a latent state to an operative state, and are extensively conserved. The layers match, at least approximately, known subcompartments found in higher eukaryotic cells. ∼80% of assembly factors are essential. The number of copies of these assembly factors is comparable to the number of nascent transcripts. Moreover, they exhibit "isoelectric balance," with RNA-binding candidate "nucleator" assembly factors being notably basic. The physical properties of pre-small subunit and pre-large subunit assembly factors are similar, as are their 19 motif signatures detected by hierarchical clustering, unlike motif signatures of the 5'-external transcribed spacer rRNP. Additionally, many assembly factors lack shared motifs. Taken together with the progression of rRNP composition during subunit maturation, and the realization that the ribosomal DNA cable is initially bathed in a subunit-nonspecific assembly factor reservoir/microenvironment, we propose a "3-step subdomain assembly model": Step (1): predominantly basic assembly factors sequentially nucleate sites along nascent rRNA; Step (2): the resulting rRNPs recruit numerous less basic assembly factors along with notably basic ribosomal proteins; Step (3): rRNPs in nearby subdomains consolidate. Cleavages of rRNA then promote release of rRNPs to the nucleoplasm, likely facilitated by the persistence of assembly factors that were already associated with nucleolar precursors.
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Affiliation(s)
- Samantha Lin
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Suchita Rajan
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Sofia Lemberg
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Mark Altawil
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Katherine Anderson
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Ruth Bryant
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Sebastian Cappeta
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Brandon Chin
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Isabella Hamdan
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Annelise Hamer
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Rachel Hyzny
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Andrew Karp
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Daniel Lee
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Alexandria Lim
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Medha Nayak
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Vishnu Palaniappan
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Soomin Park
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Sarika Satishkumar
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Anika Seth
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Uva Sri Dasari
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Emili Toppari
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Ayush Vyas
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Julianne Walker
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Evan Weston
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Atif Zafar
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Cecelia Zielke
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Ganapati H Mahabeleshwar
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Alan M Tartakoff
- Pathology Department and The Cell Biology Program, Case Western Reserve University, Cleveland, OH 44106, USA
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3
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Mitterer V, Pertschy B. RNA folding and functions of RNA helicases in ribosome biogenesis. RNA Biol 2022; 19:781-810. [PMID: 35678541 PMCID: PMC9196750 DOI: 10.1080/15476286.2022.2079890] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 05/16/2022] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic ribosome biogenesis involves the synthesis of ribosomal RNA (rRNA) and its stepwise folding into the unique structure present in mature ribosomes. rRNA folding starts already co-transcriptionally in the nucleolus and continues when pre-ribosomal particles further maturate in the nucleolus and upon their transit to the nucleoplasm and cytoplasm. While the approximate order of folding of rRNA subdomains is known, especially from cryo-EM structures of pre-ribosomal particles, the actual mechanisms of rRNA folding are less well understood. Both small nucleolar RNAs (snoRNAs) and proteins have been implicated in rRNA folding. snoRNAs hybridize to precursor rRNAs (pre-rRNAs) and thereby prevent premature folding of the respective rRNA elements. Ribosomal proteins (r-proteins) and ribosome assembly factors might have a similar function by binding to rRNA elements and preventing their premature folding. Besides that, a small group of ribosome assembly factors are thought to play a more active role in rRNA folding. In particular, multiple RNA helicases participate in individual ribosome assembly steps, where they are believed to coordinate RNA folding/unfolding events or the release of proteins from the rRNA. In this review, we summarize the current knowledge on mechanisms of RNA folding and on the specific function of the individual RNA helicases involved. As the yeast Saccharomyces cerevisiae is the organism in which ribosome biogenesis and the role of RNA helicases in this process is best studied, we focused our review on insights from this model organism, but also make comparisons to other organisms where applicable.
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Affiliation(s)
- Valentin Mitterer
- Biochemistry Center, Heidelberg University, Im Neuenheimer Feld 328, Heidelberg, Germany
- BioTechMed-Graz, Graz, Austria
| | - Brigitte Pertschy
- BioTechMed-Graz, Graz, Austria
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, Graz, Austria
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4
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Tartakoff AM, Chen L, Raghavachari S, Gitiforooz D, Dhinakaran A, Ni CL, Pasadyn C, Mahabeleshwar GH, Pasadyn V, Woolford JL. The nucleolus as a polarized coaxial cable in which the rDNA axis is surrounded by dynamic subunit-specific phases. Curr Biol 2021; 31:2507-2519.e4. [PMID: 33862007 PMCID: PMC8222187 DOI: 10.1016/j.cub.2021.03.041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 01/18/2021] [Accepted: 03/11/2021] [Indexed: 12/24/2022]
Abstract
In ribosomal DNA (rDNA) repeats, sequences encoding small-subunit (SSU) rRNA precede those encoding large-subunit (LSU) rRNAs. Processing the composite transcript and subunit assembly requires >100 subunit-specific nucleolar assembly factors (AFs). To investigate the functional organization of the nucleolus, we localized AFs in S. cerevisiae in which the rDNA axis was "linearized" to reduce its dimensionality, thereby revealing its coaxial organization. In this situation, rRNA synthesis and processing continue. The axis is embedded in an inner layer/phase of SSU AFs that is surrounded by an outer layer/phase of LSU AFs. When subunit production is inhibited, subsets of AFs differentially relocate between the inner and outer layers, as expected if there is a cycle of repeated relocation whereby "latent" AFs become "operative" when recruited to nascent subunits. Recognition of AF cycling and localization of segments of rRNA make it possible to infer the existence of assembly intermediates that span between the inner and outer layers and to chart the cotranscriptional assembly of each subunit. AF cycling also can explain how having more than one protein phase in the nucleolus makes possible "vectorial 2-phase partitioning" as a driving force for relocation of nascent rRNPs. Because nucleoplasmic AFs are also present in the outer layer, we propose that critical surface remodeling occurs at this site, thereby partitioning subunit precursors into the nucleoplasm for post-transcriptional maturation. Comparison to observations on higher eukaryotes shows that the coaxial paradigm is likely to be applicable for the many other organisms that have rDNA repeats.
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Affiliation(s)
- Alan M Tartakoff
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA.
| | - Lan Chen
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA
| | - Shashank Raghavachari
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA
| | - Daria Gitiforooz
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA
| | - Akshyasri Dhinakaran
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA
| | - Chun-Lun Ni
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA
| | | | - Ganapati H Mahabeleshwar
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA
| | - Vanessa Pasadyn
- Department of Pathology and Cell Biology Program, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA
| | - John L Woolford
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
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5
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Montellese C, van den Heuvel J, Ashiono C, Dörner K, Melnik A, Jonas S, Zemp I, Picotti P, Gillet LC, Kutay U. USP16 counteracts mono-ubiquitination of RPS27a and promotes maturation of the 40S ribosomal subunit. eLife 2020; 9:54435. [PMID: 32129764 PMCID: PMC7065907 DOI: 10.7554/elife.54435] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 03/03/2020] [Indexed: 12/12/2022] Open
Abstract
Establishment of translational competence represents a decisive cytoplasmic step in the biogenesis of 40S ribosomal subunits. This involves final 18S rRNA processing and release of residual biogenesis factors, including the protein kinase RIOK1. To identify novel proteins promoting the final maturation of human 40S subunits, we characterized pre-ribosomal subunits trapped on RIOK1 by mass spectrometry, and identified the deubiquitinase USP16 among the captured factors. We demonstrate that USP16 constitutes a component of late cytoplasmic pre-40S subunits that promotes the removal of ubiquitin from an internal lysine of ribosomal protein RPS27a/eS31. USP16 deletion leads to late 40S subunit maturation defects, manifesting in incomplete processing of 18S rRNA and retarded recycling of late-acting ribosome biogenesis factors, revealing an unexpected contribution of USP16 to the ultimate step of 40S synthesis. Finally, ubiquitination of RPS27a appears to depend on active translation, pointing at a potential connection between 40S maturation and protein synthesis.
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Affiliation(s)
| | - Jasmin van den Heuvel
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.,Molecular Life Sciences Ph.D. Program, Zurich, Switzerland
| | | | - Kerstin Dörner
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.,Molecular Life Sciences Ph.D. Program, Zurich, Switzerland
| | - André Melnik
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Stefanie Jonas
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Ivo Zemp
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Paola Picotti
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | | | - Ulrike Kutay
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
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6
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Espinar-Marchena F, Rodríguez-Galán O, Fernández-Fernández J, Linnemann J, de la Cruz J. Ribosomal protein L14 contributes to the early assembly of 60S ribosomal subunits in Saccharomyces cerevisiae. Nucleic Acids Res 2019; 46:4715-4732. [PMID: 29788267 PMCID: PMC5961077 DOI: 10.1093/nar/gky123] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 02/12/2018] [Indexed: 12/11/2022] Open
Abstract
The contribution of most ribosomal proteins to ribosome synthesis has been quite well analysed in Saccharomyces cerevisiae. However, few yeast ribosomal proteins still await characterization. Herein, we show that L14, an essential 60S ribosomal protein, assembles in the nucleolus at an early stage into pre-60S particles. Depletion of L14 results in a deficit in 60S subunits and defective processing of 27SA2 and 27SA3 to 27SB pre-rRNAs. As a result, 27S pre-rRNAs are subjected to turnover and export of pre-60S particles is blocked. These phenotypes likely appear as the direct consequence of the reduced pre-60S particle association not only of L14 upon its depletion but also of a set of neighboring ribosomal proteins located at the solvent interface of 60S subunits and the adjacent region surrounding the polypeptide exit tunnel. These pre-60S intermediates also lack some essential trans-acting factors required for 27SB pre-rRNA processing but accumulate practically all factors required for processing of 27SA3 pre-rRNA. We have also analysed the functional interaction between the eukaryote-specific carboxy-terminal extensions of the neighboring L14 and L16 proteins. Our results indicate that removal of the most distal parts of these extensions cause slight translation alterations in mature 60S subunits.
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Affiliation(s)
- Francisco Espinar-Marchena
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, Seville, Spain. Avda. Manuel Siurot, E-41013 Seville, Spain
| | - Olga Rodríguez-Galán
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, Seville, Spain. Avda. Manuel Siurot, E-41013 Seville, Spain
| | - José Fernández-Fernández
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, Seville, Spain. Avda. Manuel Siurot, E-41013 Seville, Spain
| | - Jan Linnemann
- Institut für Biochemie III, Universität Regensburg, 93053, Regensburg, Germany
| | - Jesús de la Cruz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, Seville, Spain. Avda. Manuel Siurot, E-41013 Seville, Spain
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7
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Hannig K, Babl V, Hergert K, Maier A, Pilsl M, Schächner C, Stöckl U, Milkereit P, Tschochner H, Seufert W, Griesenbeck J. The C-terminal region of Net1 is an activator of RNA polymerase I transcription with conserved features from yeast to human. PLoS Genet 2019; 15:e1008006. [PMID: 30802237 PMCID: PMC6415870 DOI: 10.1371/journal.pgen.1008006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 03/13/2019] [Accepted: 02/05/2019] [Indexed: 01/25/2023] Open
Abstract
RNA polymerase I (Pol I) synthesizes ribosomal RNA (rRNA) in all eukaryotes, accounting for the major part of transcriptional activity in proliferating cells. Although basal Pol I transcription factors have been characterized in diverse organisms, the molecular basis of the robust rRNA production in vivo remains largely unknown. In S. cerevisiae, the multifunctional Net1 protein was reported to stimulate Pol I transcription. We found that the Pol I-stimulating function can be attributed to the very C-terminal region (CTR) of Net1. The CTR was required for normal cell growth and Pol I recruitment to rRNA genes in vivo and sufficient to promote Pol I transcription in vitro. Similarity with the acidic tail region of mammalian Pol I transcription factor UBF, which could partly functionally substitute for the CTR, suggests conserved roles for CTR-like domains in Pol I transcription from yeast to human. The production of ribosomes, cellular factories of protein synthesis, is an essential process driving proliferation and cell growth. Ribosome biogenesis is controlled at the level of synthesis of its components, ribosomal proteins and ribosomal RNA. In eukaryotes, RNA polymerase I is dedicated to transcribe the ribosomal RNA. RNA polymerase I has been identified as a potential target for cell proliferation inhibition. Here we describe the C-terminal region of Net1 as an activator of RNA polymerase I transcription in baker’s yeast. In the absence of this activator RNA polymerase I transcription is downregulated and cell proliferation is strongly impaired. Strikingly, this activator might be conserved in human cells, which points to a general mechanism. Our discovery will help to gain a better understanding of the molecular basis of ribosomal RNA synthesis and may have implications in developing strategies to control cellular growth.
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Affiliation(s)
- Katharina Hannig
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Virginia Babl
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Kristin Hergert
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Andreas Maier
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Michael Pilsl
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Christopher Schächner
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Ulrike Stöckl
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
| | - Philipp Milkereit
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
| | - Herbert Tschochner
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
| | - Wolfgang Seufert
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
| | - Joachim Griesenbeck
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Regensburg, Germany
- * E-mail: (PM); (HT); (WS); (JG)
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8
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The path of pre-ribosomes through the nuclear pore complex revealed by electron tomography. Nat Commun 2019; 10:497. [PMID: 30700705 PMCID: PMC6353910 DOI: 10.1038/s41467-019-08342-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Accepted: 12/17/2018] [Indexed: 01/24/2023] Open
Abstract
Determining the path of single ribonucleoprotein (RNP) particles through the 100 nm-wide nuclear pore complex (NPC) by fluorescence microscopy remains challenging due to resolution limitation and RNP labeling constraints. By using high-pressure freezing and electron tomography, here we captured snapshots of the translocation of native RNP particles through NPCs in yeast and analyzed their trajectory at nanometer-scale resolution. Morphological and functional analyses indicate that these particles mostly correspond to pre-ribosomes. They are detected in 5–6% of the NPCs, with no apparent bias for NPCs adjacent to the nucleolus. Their path closely follows the central axis of the NPC through the nuclear and inner rings, but diverges at the cytoplasmic ring, suggesting interactions with the cytoplasmic nucleoporins. By applying a probabilistic queueing model to our data, we estimated that the dwell time of pre-ribosomes in the yeast NPC is ~90 ms. These data reveal distinct steps of pre-ribosome translocation through the NPC. Large protein complexes and ribonucleoprotein particles (RNPs) such as pre-ribosomes are transported from the nucleus to the cytoplasm through the nuclear pore complex (NPC). Here the authors use ultrafast freezing and electron tomography to catch snapshots of native RNPs crossing the NPC and estimate their transit time using a probabilistic model.
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9
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Joret C, Capeyrou R, Belhabich-Baumas K, Plisson-Chastang C, Ghandour R, Humbert O, Fribourg S, Leulliot N, Lebaron S, Henras AK, Henry Y. The Npa1p complex chaperones the assembly of the earliest eukaryotic large ribosomal subunit precursor. PLoS Genet 2018; 14:e1007597. [PMID: 30169518 PMCID: PMC6136799 DOI: 10.1371/journal.pgen.1007597] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 09/13/2018] [Accepted: 07/30/2018] [Indexed: 11/18/2022] Open
Abstract
The early steps of the production of the large ribosomal subunit are probably the least understood stages of eukaryotic ribosome biogenesis. The first specific precursor to the yeast large ribosomal subunit, the first pre-60S particle, contains 30 assembly factors (AFs), including 8 RNA helicases. These helicases, presumed to drive conformational rearrangements, usually lack substrate specificity in vitro. The mechanisms by which they are targeted to their correct substrate within pre-ribosomal particles and their precise molecular roles remain largely unknown. We demonstrate that the Dbp6p helicase, essential for the normal accumulation of the first pre-60S pre-ribosomal particle in S. cerevisiae, associates with a complex of four AFs, namely Npa1p, Npa2p, Nop8p and Rsa3p, prior to their incorporation into the 90S pre-ribosomal particles. By tandem affinity purifications using yeast extracts depleted of one component of the complex, we show that Npa1p forms the backbone of the complex. We provide evidence that Npa1p and Npa2p directly bind Dbp6p and we demonstrate that Npa1p is essential for the insertion of the Dbp6p helicase within 90S pre-ribosomal particles. In addition, by an in vivo cross-linking analysis (CRAC), we map Npa1p rRNA binding sites on 25S rRNA adjacent to the root helices of the first and last secondary structure domains of 25S rRNA. This finding supports the notion that Npa1p and Dbp6p function in the formation and/or clustering of root helices of large subunit rRNAs which creates the core of the large ribosomal subunit RNA structure. Npa1p also crosslinks to snoRNAs involved in decoding center and peptidyl transferase center modifications and in the immediate vicinity of the binding sites of these snoRNAs on 25S rRNA. Our data suggest that the Dbp6p helicase and the Npa1p complex play key roles in the compaction of the central core of 25S rRNA and the control of snoRNA-pre-rRNA interactions. Ribosomes, the molecular machines synthesizing proteins, are composed of a small and large subunit, formed by the binding of numerous ribosomal proteins (RPs) to properly folded ribosomal RNAs (rRNAs). RP incorporation as well as processing and folding of rRNAs occur within a succession of pre-ribosomal particles. Formation of the initial pre-60S particle, the first precursor to the large ribosomal subunit, is the least understood step of ribosome biogenesis in eukaryotes. This pre-ribosomal particle contains several assembly factors (AFs), including RNA helicases believed to catalyse key conformational rearrangements. These helicases usually lack substrate specificity on their own. Here, we show that the Dbp6p helicase, a component of the first pre-60S particle and essential for its normal accumulation, associates with a complex of four AFs, including Npa1p. We demonstrate that Npa1p directly binds Dbp6p, forms the backbone of the complex and is required for the integration of Dbp6p within pre-ribosomal particles. We show that Npa1p binds to sequences forming the core of large subunit rRNAs as well as small nucleolar RNAs required for chemical modification of large subunit rRNAs. Altogether our results suggest that the Npa1p complex plays a crucial role in the chemical modification and folding of large subunit rRNAs.
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Affiliation(s)
- Clément Joret
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Régine Capeyrou
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Kamila Belhabich-Baumas
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Célia Plisson-Chastang
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Rabea Ghandour
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Odile Humbert
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | | | - Nicolas Leulliot
- Laboratoire de Cristallographie et RMN Biologiques, UMR CNRS 8015, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, Paris, France
| | - Simon Lebaron
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
- * E-mail: (SL); (AKH); (YH)
| | - Anthony K. Henras
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
- * E-mail: (SL); (AKH); (YH)
| | - Yves Henry
- Laboratoire de Biologie Moléculaire Eucaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
- * E-mail: (SL); (AKH); (YH)
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10
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Greber BJ. Mechanistic insight into eukaryotic 60S ribosomal subunit biogenesis by cryo-electron microscopy. RNA (NEW YORK, N.Y.) 2016; 22:1643-1662. [PMID: 27875256 PMCID: PMC5066618 DOI: 10.1261/rna.057927.116] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Eukaryotic ribosomes, the protein-producing factories of the cell, are composed of four ribosomal RNA molecules and roughly 80 proteins. Their biogenesis is a complex process that involves more than 200 biogenesis factors that facilitate the production, modification, and assembly of ribosomal components and the structural transitions along the maturation pathways of the pre-ribosomal particles. Here, I review recent structural and mechanistic insights into the biogenesis of the large ribosomal subunit that were furthered by cryo-electron microscopy of natively purified pre-60S particles and in vitro reconstituted ribosome assembly factor complexes. Combined with biochemical, genetic, and previous structural data, these structures have provided detailed insights into the assembly and maturation of the central protuberance of the 60S subunit, the network of biogenesis factors near the ribosomal tunnel exit, and the functional activation of the large ribosomal subunit during cytoplasmic maturation.
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Affiliation(s)
- Basil J Greber
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720-3220, USA
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11
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Talkish J, Biedka S, Jakovljevic J, Zhang J, Tang L, Strahler JR, Andrews PC, Maddock JR, Woolford JL. Disruption of ribosome assembly in yeast blocks cotranscriptional pre-rRNA processing and affects the global hierarchy of ribosome biogenesis. RNA (NEW YORK, N.Y.) 2016; 22:852-66. [PMID: 27036125 PMCID: PMC4878612 DOI: 10.1261/rna.055780.115] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 02/18/2016] [Indexed: 05/11/2023]
Abstract
In higher eukaryotes, pre-rRNA processing occurs almost exclusively post-transcriptionally. This is not the case in rapidly dividing yeast, as the majority of nascent pre-rRNAs are processed cotranscriptionally, with cleavage at the A2 site first releasing a pre-40S ribosomal subunit followed by release of a pre-60S ribosomal subunit upon transcription termination. Ribosome assembly is driven in part by hierarchical association of assembly factors and r-proteins. Groups of proteins are thought to associate with pre-ribosomes cotranscriptionally during early assembly steps, whereas others associate later, after transcription is completed. Here we describe a previously uncharacterized phenotype observed upon disruption of ribosome assembly, in which normally late-binding proteins associate earlier, with pre-ribosomes containing 35S pre-rRNA. As previously observed by many other groups, we show that disruption of 60S subunit biogenesis results in increased amounts of 35S pre-rRNA, suggesting that a greater fraction of pre-rRNAs are processed post-transcriptionally. Surprisingly, we found that early pre-ribosomes containing 35S pre-rRNA also contain proteins previously thought to only associate with pre-ribosomes after early pre-rRNA processing steps have separated maturation of the two subunits. We believe the shift to post-transcriptional processing is ultimately due to decreased cellular division upon disruption of ribosome assembly. When cells are grown under stress or to high density, a greater fraction of pre-rRNAs are processed post-transcriptionally and follow an alternative processing pathway. Together, these results affirm the principle that ribosome assembly occurs through different, parallel assembly pathways and suggest that there is a kinetic foot-race between the formation of protein binding sites and pre-rRNA processing events.
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Affiliation(s)
- Jason Talkish
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA The Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - Stephanie Biedka
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA The Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Jelena Jakovljevic
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA The Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Jingyu Zhang
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Lan Tang
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - John R Strahler
- Department of Biological Chemistry, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Philip C Andrews
- Department of Biological Chemistry, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Janine R Maddock
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - John L Woolford
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA The Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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12
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Greber BJ, Gerhardy S, Leitner A, Leibundgut M, Salem M, Boehringer D, Leulliot N, Aebersold R, Panse VG, Ban N. Insertion of the Biogenesis Factor Rei1 Probes the Ribosomal Tunnel during 60S Maturation. Cell 2015; 164:91-102. [PMID: 26709046 DOI: 10.1016/j.cell.2015.11.027] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 10/08/2015] [Accepted: 11/05/2015] [Indexed: 10/22/2022]
Abstract
Eukaryotic ribosome biogenesis depends on several hundred assembly factors to produce functional 40S and 60S ribosomal subunits. The final phase of 60S subunit biogenesis is cytoplasmic maturation, which includes the proofreading of functional centers of the 60S subunit and the release of several ribosome biogenesis factors. We report the cryo-electron microscopy (cryo-EM) structure of the yeast 60S subunit in complex with the biogenesis factors Rei1, Arx1, and Alb1 at 3.4 Å resolution. In addition to the network of interactions formed by Alb1, the structure reveals a mechanism for ensuring the integrity of the ribosomal polypeptide exit tunnel. Arx1 probes the entire set of inner-ring proteins surrounding the tunnel exit, and the C terminus of Rei1 is deeply inserted into the ribosomal tunnel, where it forms specific contacts along almost its entire length. We provide genetic and biochemical evidence that failure to insert the C terminus of Rei1 precludes subsequent steps of 60S maturation.
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Affiliation(s)
- Basil Johannes Greber
- Institute of Molecular Biology and Biophysics, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Stefan Gerhardy
- Institute of Biochemistry, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Alexander Leitner
- Institute of Molecular Systems Biology, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Marc Leibundgut
- Institute of Molecular Biology and Biophysics, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Michèle Salem
- Laboratoire de Cristallographie et RMN Biologiques, UMR CNRS 8015, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, 75006 Paris, France
| | - Daniel Boehringer
- Institute of Molecular Biology and Biophysics, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Nicolas Leulliot
- Laboratoire de Cristallographie et RMN Biologiques, UMR CNRS 8015, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, 75006 Paris, France
| | - Ruedi Aebersold
- Institute of Molecular Systems Biology, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland; Faculty of Science, University of Zurich, CH-8057 Zurich, Switzerland
| | - Vikram Govind Panse
- Institute of Biochemistry, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Nenad Ban
- Institute of Molecular Biology and Biophysics, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland.
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13
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Thoms M, Ahmed YL, Maddi K, Hurt E, Sinning I. Concerted removal of the Erb1-Ytm1 complex in ribosome biogenesis relies on an elaborate interface. Nucleic Acids Res 2015; 44:926-39. [PMID: 26657628 PMCID: PMC4737154 DOI: 10.1093/nar/gkv1365] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 11/24/2015] [Indexed: 12/21/2022] Open
Abstract
The complicated process of eukaryotic ribosome biogenesis involves about 200 assembly factors that transiently associate with the nascent pre-ribosome in a spatiotemporally ordered way. During the early steps of 60S subunit formation, several proteins, collectively called A3 cluster factors, participate in the removal of the internal transcribed spacer 1 (ITS1) from 27SA3 pre-rRNA. Among these factors is the conserved hetero-trimeric Nop7–Erb1–Ytm1 complex (or human Pes1–Bop1–Wdr12), which is removed from the evolving pre-60S particle by the AAA ATPase Rea1 to allow progression in the pathway. Here, we clarify how Ytm1 and Erb1 interact, which has implications for the release mechanism of both factors from the pre-ribosome. Biochemical studies show that Ytm1 and Erb1 bind each other via their ß-propeller domains. The crystal structure of the Erb1–Ytm1 heterodimer determined at 2.67Å resolution reveals an extended interaction surface between the propellers in a rarely observed binding mode. Structure-based mutations in the interface that impair the Erb1–Ytm1 interaction do not support growth, with specific defects in 60S subunit synthesis. Under these mutant conditions, it becomes clear that an intact Erb1–Ytm1 complex is required for 60S maturation and that loss of this stable interaction prevents ribosome production.
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Affiliation(s)
- Matthias Thoms
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Yasar Luqman Ahmed
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Karthik Maddi
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Ed Hurt
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
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14
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McCann KL, Charette JM, Vincent NG, Baserga SJ. A protein interaction map of the LSU processome. Genes Dev 2015; 29:862-75. [PMID: 25877921 PMCID: PMC4403261 DOI: 10.1101/gad.256370.114] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 03/04/2015] [Indexed: 01/12/2023]
Abstract
Maturation of the large ribosomal subunit (LSU) in eukaryotes is a complex and highly coordinated process that requires the concerted action of a large, dynamic, ribonucleoprotein complex, the LSU processome. To interrogate its organization and architecture, McCann et al. assayed 4800 protein–protein interactions and identified 232 high-confidence, binary-interacting protein pairs, representing a fourfold increase from current knowledge. The resulting LSU processome interactome map enhances our understanding of the organization and function of the biogenesis factors within the LSU processome. Maturation of the large ribosomal subunit (LSU) in eukaryotes is a complex and highly coordinated process that requires the concerted action of a large, dynamic, ribonucleoprotein complex, the LSU processome. While we know that >80 ribosome biogenesis factors are required throughout the course of LSU assembly, little is known about how these factors interact with each other within the LSU processome. To interrogate its organization and architecture, we took a systems biology approach and performed a semi-high-throughput, array-based, directed yeast two-hybrid assay. Assaying 4800 protein–protein interactions, we identified 232 high-confidence, binary-interacting protein pairs, representing a fourfold increase from current knowledge. The resulting LSU processome interactome map has enhanced our understanding of the organization and function of the biogenesis factors within the LSU processome, revealing both novel and previously identified subcomplexes and hub proteins, including Nop4.
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Affiliation(s)
- Kathleen L McCann
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | - J Michael Charette
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA; Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | - Nicholas G Vincent
- Department of Microbiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | - Susan J Baserga
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA; Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA; Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA;
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15
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Kellner M, Rohrmoser M, Forné I, Voss K, Burger K, Mühl B, Gruber-Eber A, Kremmer E, Imhof A, Eick D. DEAD-box helicase DDX27 regulates 3' end formation of ribosomal 47S RNA and stably associates with the PeBoW-complex. Exp Cell Res 2015; 334:146-59. [PMID: 25825154 DOI: 10.1016/j.yexcr.2015.03.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 03/18/2015] [Accepted: 03/19/2015] [Indexed: 02/07/2023]
Abstract
PeBoW, a trimeric complex consisting of pescadillo (Pes1), block of proliferation (Bop1), and the WD repeat protein 12 (WDR12), is essential for processing and maturation of mammalian 5.8S and 28S ribosomal RNAs. Applying a mass spectrometric analysis, we identified the DEAD-box helicase DDX27 as stably associated factor of the PeBoW-complex. DDX27 interacts with the PeBoW-complex via an evolutionary conserved F×F motif in the N-terminal domain and is recruited to the nucleolus via its basic C-terminal domain. This recruitment is RNA-dependent and occurs independently of the PeBoW-complex. Interestingly, knockdown of DDX27, but not of Pes1, induces the accumulation of an extended form of the primary 47S rRNA. We conclude that DDX27 can interact specifically with the Pes1 and Bop1 but fulfils critical function(s) for proper 3' end formation of 47S rRNA independently of the PeBoW-complex.
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Affiliation(s)
- Markus Kellner
- Department of Molecular Epigenetics, Helmholtz Center Munich, Center for Integrated Protein Science Munich (CIPSM), Marchioninistr. 25, Munich 81377, Germany
| | - Michaela Rohrmoser
- Department of Molecular Epigenetics, Helmholtz Center Munich, Center for Integrated Protein Science Munich (CIPSM), Marchioninistr. 25, Munich 81377, Germany
| | - Ignasi Forné
- Adolf Butenandt Institute, Ludwig Maximilians University of Munich, Center for Integrated Protein Science Munich (CIPSM), Schillerstr. 44, Munich 80336, Germany
| | - Kirsten Voss
- Department of Molecular Epigenetics, Helmholtz Center Munich, Center for Integrated Protein Science Munich (CIPSM), Marchioninistr. 25, Munich 81377, Germany
| | - Kaspar Burger
- Department of Molecular Epigenetics, Helmholtz Center Munich, Center for Integrated Protein Science Munich (CIPSM), Marchioninistr. 25, Munich 81377, Germany
| | - Bastian Mühl
- Department of Molecular Epigenetics, Helmholtz Center Munich, Center for Integrated Protein Science Munich (CIPSM), Marchioninistr. 25, Munich 81377, Germany
| | - Anita Gruber-Eber
- Department of Molecular Epigenetics, Helmholtz Center Munich, Center for Integrated Protein Science Munich (CIPSM), Marchioninistr. 25, Munich 81377, Germany
| | - Elisabeth Kremmer
- Institute of Molecular Immunology, Helmholtz Center Munich, Marchioninistr. 25, Munich 81377, Germany
| | - Axel Imhof
- Adolf Butenandt Institute, Ludwig Maximilians University of Munich, Center for Integrated Protein Science Munich (CIPSM), Schillerstr. 44, Munich 80336, Germany
| | - Dirk Eick
- Department of Molecular Epigenetics, Helmholtz Center Munich, Center for Integrated Protein Science Munich (CIPSM), Marchioninistr. 25, Munich 81377, Germany.
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16
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Zheng S, Lan P, Liu X, Ye K. Interaction between ribosome assembly factors Krr1 and Faf1 is essential for formation of small ribosomal subunit in yeast. J Biol Chem 2014; 289:22692-22703. [PMID: 24990943 DOI: 10.1074/jbc.m114.584490] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Ribosome formation in Saccharomyces cerevisiae requires a large number of transiently associated assembly factors that coordinate processing and folding of pre-rRNA and binding of ribosomal proteins. Krr1 and Faf1 are two interacting proteins present in early 90 S precursor particles of the small ribosomal subunit. Here, we determined a co-crystal structure of the core domain of Krr1 bound to a 19-residue fragment of Faf1 at 2.8 Å resolution. The structure reveals that Krr1 consists of two packed K homology (KH) domains, KH1 and KH2, and resembles archaeal Dim2-like proteins. We show that KH1 is a divergent KH domain that lacks the RNA-binding GXXG motif and is involved in binding another assembly factor, Kri1. KH2 contains a canonical RNA-binding surface and additionally associates with an α-helix of Faf1. Specific disruption of the Krr1-Faf1 interaction impaired early 18 S rRNA processing at sites A0, A1, and A2 and caused cell lethality, but it did not prevent incorporation of the two proteins into pre-ribosomes. The Krr1-Faf1 interaction likely maintains a critical conformation of 90 S pre-ribosomes required for pre-rRNA processing. Our results illustrate the versatility of KH domains in protein interaction and provide insight into the role of Krr1-Faf1 interaction in ribosome biogenesis.
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Affiliation(s)
- Sanduo Zheng
- Department of Biochemistry and Molecular Biology, College of Life Sciences, Beijing Normal University, Beijing 100875,; National Institute of Biological Sciences at Beijing, Beijing 102206, and
| | - Pengfei Lan
- National Institute of Biological Sciences at Beijing, Beijing 102206, and; Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730
| | - Ximing Liu
- National Institute of Biological Sciences at Beijing, Beijing 102206, and
| | - Keqiong Ye
- National Institute of Biological Sciences at Beijing, Beijing 102206, and; Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730,; Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
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17
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Ribosome assembly factors Pwp1 and Nop12 are important for folding of 5.8S rRNA during ribosome biogenesis in Saccharomyces cerevisiae. Mol Cell Biol 2014; 34:1863-77. [PMID: 24636992 DOI: 10.1128/mcb.01322-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Previous work from our lab suggests that a group of interdependent assembly factors (A(3) factors) is necessary to create early, stable preribosomes. Many of these proteins bind at or near internal transcribed spacer 2 (ITS2), but in their absence, ITS1 is not removed from rRNA, suggesting long-range communication between these two spacers. By comparing the nonessential assembly factors Nop12 and Pwp1, we show that misfolding of rRNA is sufficient to perturb early steps of biogenesis, but it is the lack of A(3) factors that results in turnover of early preribosomes. Deletion of NOP12 significantly inhibits 27SA(3) pre-rRNA processing, even though the A(3) factors are present in preribosomes. Furthermore, pre-rRNAs are stable, indicating that the block in processing is not sufficient to trigger turnover. This is in contrast to the absence of Pwp1, in which the A(3) factors are not present and pre-rRNAs are unstable. In vivo RNA structure probing revealed that the pre-rRNA processing defects are due to misfolding of 5.8S rRNA. In the absence of Nop12 and Pwp1, rRNA helix 5 is not stably formed. Interestingly, the absence of Nop12 results in the formation of an alternative yet unproductive helix 5 when cells are grown at low temperatures.
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18
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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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19
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Ohmayer U, Gamalinda M, Sauert M, Ossowski J, Pöll G, Linnemann J, Hierlmeier T, Perez-Fernandez J, Kumcuoglu B, Leger-Silvestre I, Faubladier M, Griesenbeck J, Woolford J, Tschochner H, Milkereit P. Studies on the assembly characteristics of large subunit ribosomal proteins in S. cerevisae. PLoS One 2013; 8:e68412. [PMID: 23874617 PMCID: PMC3707915 DOI: 10.1371/journal.pone.0068412] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 05/29/2013] [Indexed: 11/18/2022] Open
Abstract
During the assembly process of ribosomal subunits, their structural components, the ribosomal RNAs (rRNAs) and the ribosomal proteins (r-proteins) have to join together in a highly dynamic and defined manner to enable the efficient formation of functional ribosomes. In this work, the assembly of large ribosomal subunit (LSU) r-proteins from the eukaryote S. cerevisiae was systematically investigated. Groups of LSU r-proteins with specific assembly characteristics were detected by comparing the protein composition of affinity purified early, middle, late or mature LSU (precursor) particles by semi-quantitative mass spectrometry. The impact of yeast LSU r-proteins rpL25, rpL2, rpL43, and rpL21 on the composition of intermediate to late nuclear LSU precursors was analyzed in more detail. Effects of these proteins on the assembly states of other r-proteins and on the transient LSU precursor association of several ribosome biogenesis factors, including Nog2, Rsa4 and Nop53, are discussed.
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Affiliation(s)
- Uli Ohmayer
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Michael Gamalinda
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Martina Sauert
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Julius Ossowski
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Gisela Pöll
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Jan Linnemann
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Thomas Hierlmeier
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | | | - Beril Kumcuoglu
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Isabelle Leger-Silvestre
- Laboratoire de Biologie Moléculaire Eucaryote, UMR 5099, Universite Paul Sabatier, Toulouse, France
| | - Marlène Faubladier
- Laboratoire de Biologie Moléculaire Eucaryote, UMR 5099, Universite Paul Sabatier, Toulouse, France
| | | | - John Woolford
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Herbert Tschochner
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Philipp Milkereit
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
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20
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Hierlmeier T, Merl J, Sauert M, Perez-Fernandez J, Schultz P, Bruckmann A, Hamperl S, Ohmayer U, Rachel R, Jacob A, Hergert K, Deutzmann R, Griesenbeck J, Hurt E, Milkereit P, Baßler J, Tschochner H. Rrp5p, Noc1p and Noc2p form a protein module which is part of early large ribosomal subunit precursors in S. cerevisiae. Nucleic Acids Res 2012. [PMID: 23209026 PMCID: PMC3553968 DOI: 10.1093/nar/gks1056] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Eukaryotic ribosome biogenesis requires more than 150 auxiliary proteins, which transiently interact with pre-ribosomal particles. Previous studies suggest that several of these biogenesis factors function together as modules. Using a heterologous expression system, we show that the large ribosomal subunit (LSU) biogenesis factor Noc1p of Saccharomyces cerevisiae can simultaneously interact with the LSU biogenesis factor Noc2p and Rrp5p, a factor required for biogenesis of the large and the small ribosomal subunit. Proteome analysis of RNA polymerase-I-associated chromatin and chromatin immunopurification experiments indicated that all members of this protein module and a specific set of LSU biogenesis factors are co-transcriptionally recruited to nascent ribosomal RNA (rRNA) precursors in yeast cells. Further ex vivo analyses showed that all module members predominantly interact with early pre-LSU particles after the initial pre-rRNA processing events have occurred. In yeast strains depleted of Noc1p, Noc2p or Rrp5p, levels of the major LSU pre-rRNAs decreased and the respective other module members were associated with accumulating aberrant rRNA fragments. Therefore, we conclude that the module exhibits several binding interfaces with pre-ribosomes. Taken together, our results suggest a co- and post-transcriptional role of the yeast Rrp5p-Noc1p-Noc2p module in the structural organization of early LSU precursors protecting them from non-productive RNase activity.
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Affiliation(s)
- Thomas Hierlmeier
- Universität Regensburg, Biochemie-Zentrum Regensburg (BZR), Lehrstuhl Biochemie III, 93053 Regensburg, Germany
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21
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Greber BJ, Boehringer D, Montellese C, Ban N. Cryo-EM structures of Arx1 and maturation factors Rei1 and Jjj1 bound to the 60S ribosomal subunit. Nat Struct Mol Biol 2012; 19:1228-33. [PMID: 23142985 DOI: 10.1038/nsmb.2425] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 09/24/2012] [Indexed: 11/09/2022]
Abstract
Eukaryotic ribosome biogenesis requires many protein factors that facilitate the assembly, nuclear export and final maturation of 40S and 60S particles. We have biochemically characterized ribosomal complexes of the yeast 60S-biogenesis factor Arx1 and late-maturation factors Rei1 and Jjj1 and determined their cryo-EM structures. Arx1 was visualized bound to the 60S subunit together with Rei1, at 8.1-Å resolution, to reveal the molecular details of Arx1 binding whereby Arx1 arrests the eukaryotic-specific rRNA expansion segment 27 near the polypeptide tunnel exit. Rei1 and Jjj1, which have been implicated in Arx1 recycling, bind in the vicinity of Arx1 and form a network of interactions. We suggest that, in addition to the role of Arx1 during pre-60S nuclear export, the binding of Arx1 conformationally locks the pre-60S subunit and inhibits the premature association of nascent chain-processing factors to the polypeptide tunnel exit.
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Affiliation(s)
- Basil J Greber
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
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22
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Jakovljevic J, Ohmayer U, Gamalinda M, Talkish J, Alexander L, Linnemann J, Milkereit P, Woolford JL. Ribosomal proteins L7 and L8 function in concert with six A₃ assembly factors to propagate assembly of domains I and II of 25S rRNA in yeast 60S ribosomal subunits. RNA (NEW YORK, N.Y.) 2012; 18:1805-22. [PMID: 22893726 PMCID: PMC3446705 DOI: 10.1261/rna.032540.112] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 07/02/2012] [Indexed: 05/24/2023]
Abstract
Ribosome biogenesis is a complex multistep process that involves alternating steps of folding and processing of pre-rRNAs in concert with assembly of ribosomal proteins. Recently, there has been increased interest in the roles of ribosomal proteins in eukaryotic ribosome biogenesis in vivo, focusing primarily on their function in pre-rRNA processing. However, much less is known about participation of ribosomal proteins in the formation and rearrangement of preribosomal particles as they mature to functional subunits. We have studied ribosomal proteins L7 and L8, which are required for the same early steps in pre-rRNA processing during assembly of 60S subunits but are located in different domains within ribosomes. Depletion of either leads to defects in processing of 27SA(3) to 27SB pre-rRNA and turnover of pre-rRNAs destined for large ribosomal subunits. A specific subset of proteins is diminished from these residual assembly intermediates: six assembly factors required for processing of 27SA(3) pre-rRNA and four ribosomal proteins bound to domain I of 25S and 5.8S rRNAs surrounding the polypeptide exit tunnel. In addition, specific sets of ribosomal proteins are affected in each mutant: In the absence of L7, proteins bound to domain II, L6, L14, L20, and L33 are greatly diminished, while proteins L13, L15, and L36 that bind to domain I are affected in the absence of L8. Thus, L7 and L8 might establish RNP structures within assembling ribosomes necessary for the stable association and function of the A(3) assembly factors and for proper assembly of the neighborhoods containing domains I and II.
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MESH Headings
- Active Transport, Cell Nucleus/genetics
- Active Transport, Cell Nucleus/physiology
- Cell Nucleus/genetics
- Cell Nucleus/metabolism
- Gene Expression Profiling
- Gene Expression Regulation, Fungal
- Microarray Analysis
- Organisms, Genetically Modified
- Protein Interaction Domains and Motifs/genetics
- Protein Interaction Domains and Motifs/physiology
- Protein Multimerization/genetics
- Protein Multimerization/physiology
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional/genetics
- RNA Processing, Post-Transcriptional/physiology
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- RNA-Binding Proteins/physiology
- Ribosomal Proteins/genetics
- Ribosomal Proteins/metabolism
- Ribosomal Proteins/physiology
- Ribosome Subunits, Large, Eukaryotic/chemistry
- Ribosome Subunits, Large, Eukaryotic/genetics
- Ribosome Subunits, Large, Eukaryotic/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae/ultrastructure
- Saccharomyces cerevisiae Proteins/genetics
- Saccharomyces cerevisiae Proteins/metabolism
- Saccharomyces cerevisiae Proteins/physiology
- Yeasts/genetics
- Yeasts/metabolism
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Affiliation(s)
- Jelena Jakovljevic
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Uli Ohmayer
- Institut für Biochemie III, Universität Regensburg, 93053 Regensburg, Germany
| | - Michael Gamalinda
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Jason Talkish
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Lisa Alexander
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Jan Linnemann
- Institut für Biochemie III, Universität Regensburg, 93053 Regensburg, Germany
| | - Philipp Milkereit
- Institut für Biochemie III, Universität Regensburg, 93053 Regensburg, Germany
| | - John L. Woolford
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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23
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Talkish J, Zhang J, Jakovljevic J, Horsey EW, Woolford JL. Hierarchical recruitment into nascent ribosomes of assembly factors required for 27SB pre-rRNA processing in Saccharomyces cerevisiae. Nucleic Acids Res 2012; 40:8646-61. [PMID: 22735702 PMCID: PMC3458554 DOI: 10.1093/nar/gks609] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
To better define the roles of assembly factors required for eukaryotic ribosome biogenesis, we have focused on one specific step in maturation of yeast 60 S ribosomal subunits: processing of 27SB pre-ribosomal RNA. At least 14 assembly factors, the 'B-factor' proteins, are required for this step. These include most of the major functional classes of assembly factors: RNA-binding proteins, scaffolding protein, DEAD-box ATPases and GTPases. We have investigated the mechanisms by which these factors associate with assembling ribosomes. Our data establish a recruitment model in which assembly of the B-factors into nascent ribosomes ultimately leads to the recruitment of the GTPase Nog2. A more detailed analysis suggests that this occurs in a hierarchical manner via two largely independent recruiting pathways that converge on Nog2. Understanding recruitment has allowed us to better determine the order of association of all assembly factors functioning in one step of ribosome assembly. Furthermore, we have identified a novel subcomplex composed of the B-factors Nop2 and Nip7. Finally, we identified a means by which this step in ribosome biogenesis is regulated in concert with cell growth via the TOR protein kinase pathway. Inhibition of TOR kinase decreases association of Rpf2, Spb4, Nog1 and Nog2 with pre-ribosomes.
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Affiliation(s)
- Jason Talkish
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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24
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Jakob S, Ohmayer U, Neueder A, Hierlmeier T, Perez-Fernandez J, Hochmuth E, Deutzmann R, Griesenbeck J, Tschochner H, Milkereit P. Interrelationships between yeast ribosomal protein assembly events and transient ribosome biogenesis factors interactions in early pre-ribosomes. PLoS One 2012; 7:e32552. [PMID: 22431976 PMCID: PMC3303783 DOI: 10.1371/journal.pone.0032552] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 01/31/2012] [Indexed: 12/12/2022] Open
Abstract
Early steps of eukaryotic ribosome biogenesis require a large set of ribosome biogenesis factors which transiently interact with nascent rRNA precursors (pre-rRNA). Most likely, concomitant with that initial contacts between ribosomal proteins (r-proteins) and ribosome precursors (pre-ribosomes) are established which are converted into robust interactions between pre-rRNA and r-proteins during the course of ribosome maturation. Here we analysed the interrelationship between r-protein assembly events and the transient interactions of ribosome biogenesis factors with early pre-ribosomal intermediates termed 90S pre-ribosomes or small ribosomal subunit (SSU) processome in yeast cells. We observed that components of the SSU processome UTP-A and UTP-B sub-modules were recruited to early pre-ribosomes independently of all tested r-proteins. On the other hand, groups of SSU processome components were identified whose association with early pre-ribosomes was affected by specific r-protein assembly events in the head-platform interface of the SSU. One of these components, Noc4p, appeared to be itself required for robust incorporation of r-proteins into the SSU head domain. Altogether, the data reveal an emerging network of specific interrelationships between local r-protein assembly events and the functional interactions of SSU processome components with early pre-ribosomes. They point towards some of these components being transient primary pre-rRNA in vivo binders and towards a role for others in coordinating the assembly of major SSU domains.
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Affiliation(s)
- Steffen Jakob
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Uli Ohmayer
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Andreas Neueder
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Thomas Hierlmeier
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | | | - Eduard Hochmuth
- Lehrstuhl für Biochemie I, Universität Regensburg, Regensburg, Germany
| | - Rainer Deutzmann
- Lehrstuhl für Biochemie I, Universität Regensburg, Regensburg, Germany
| | | | - Herbert Tschochner
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Philipp Milkereit
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
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25
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Woolls HA, Lamanna AC, Karbstein K. Roles of Dim2 in ribosome assembly. J Biol Chem 2011; 286:2578-86. [PMID: 21075849 PMCID: PMC3024753 DOI: 10.1074/jbc.m110.191494] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 11/12/2010] [Indexed: 12/25/2022] Open
Abstract
In eukaryotes, ribosome assembly requires hundreds of conserved essential proteins not present in the mature particle. Despite their importance, the function of most factors remains unknown. This is because protein deletion often affects the composition of the entire particle. Additionally, many proteins are present in assembling ribosomes for extended times, which makes it difficult to pinpoint their role to a particular step. Here we have combined classical yeast biochemistry with experiments using recombinant proteins and RNA to study the role of Dim2 and its interaction with Nob1, the nuclease that generates the 3'-end of 18 S rRNA. Analysis of Dim2 mutants in which the interaction with Nob1 is disrupted demonstrates that this interaction between Dim2 and Nob1 is essential for optimal growth, and RNA binding experiments show that Dim2 increases Nob1 RNA affinity. Furthermore, our data indicate that Dim2 helps regulate Nob1 cleavage activity at the 3'-end of 18 S rRNA, as point mutants where this interaction is abolished in vitro accumulate pre-ribosomes containing Nob1 and 20 S rRNA in vivo. Interestingly, the site of interaction with Nob1 is mapped to the canonical RNA binding surface of a KH-like domain in Dim2, providing another example where an RNA-binding domain can be repurposed for protein interactions.
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Affiliation(s)
| | - Allison C. Lamanna
- the Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055
| | - Katrin Karbstein
- From the Program in Chemical Biology and
- the Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055
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26
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Campbell MG, Karbstein K. Protein-protein interactions within late pre-40S ribosomes. PLoS One 2011; 6:e16194. [PMID: 21283762 PMCID: PMC3024409 DOI: 10.1371/journal.pone.0016194] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 12/07/2010] [Indexed: 12/28/2022] Open
Abstract
Ribosome assembly in eukaryotic organisms requires more than 200 assembly factors to facilitate and coordinate rRNA transcription, processing, and folding with the binding of the ribosomal proteins. Many of these assembly factors bind and dissociate at defined times giving rise to discrete assembly intermediates, some of which have been partially characterized with regards to their protein and RNA composition. Here, we have analyzed the protein-protein interactions between the seven assembly factors bound to late cytoplasmic pre-40S ribosomes using recombinant proteins in binding assays. Our data show that these factors form two modules: one comprising Enp1 and the export adaptor Ltv1 near the beak structure, and the second comprising the kinase Rio2, the nuclease Nob1, and a regulatory RNA binding protein Dim2/Pno1 on the front of the head. The GTPase-like Tsr1 and the universally conserved methylase Dim1 are also peripherally connected to this second module. Additionally, in an effort to further define the locations for these essential proteins, we have analyzed the interactions between these assembly factors and six ribosomal proteins: Rps0, Rps3, Rps5, Rps14, Rps15 and Rps29. Together, these results and previous RNA-protein crosslinking data allow us to propose a model for the binding sites of these seven assembly factors. Furthermore, our data show that the essential kinase Rio2 is located at the center of the pre-ribosomal particle and interacts, directly or indirectly, with every other assembly factor, as well as three ribosomal proteins required for cytoplasmic 40S maturation. These data suggest that Rio2 could play a central role in regulating cytoplasmic maturation steps.
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Affiliation(s)
- Melody G. Campbell
- Department of Cancer Biology, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Katrin Karbstein
- Department of Cancer Biology, The Scripps Research Institute, Jupiter, Florida, United States of America
- * E-mail:
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27
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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