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Vanden Broeck A, Klinge S. Principles of human pre-60 S biogenesis. Science 2023; 381:eadh3892. [PMID: 37410842 DOI: 10.1126/science.adh3892] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 05/20/2023] [Indexed: 07/08/2023]
Abstract
During the early stages of human large ribosomal subunit (60S) biogenesis, an ensemble of assembly factors establishes and fine-tunes the essential RNA functional centers of pre-60S particles by an unknown mechanism. Here, we report a series of cryo-electron microscopy structures of human nucleolar and nuclear pre-60S assembly intermediates at resolutions of 2.5 to 3.2 angstroms. These structures show how protein interaction hubs tether assembly factor complexes to nucleolar particles and how guanosine triphosphatases and adenosine triphosphatase couple irreversible nucleotide hydrolysis steps to the installation of functional centers. Nuclear stages highlight how a conserved RNA-processing complex, the rixosome, couples large-scale RNA conformational changes with pre-ribosomal RNA processing by the RNA degradation machinery. Our ensemble of human pre-60S particles provides a rich foundation with which to elucidate the molecular principles of ribosome formation.
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Affiliation(s)
- Arnaud Vanden Broeck
- Laboratory of Protein and Nucleic Acid Chemistry, The Rockefeller University, New York, NY 10065, USA
| | - Sebastian Klinge
- Laboratory of Protein and Nucleic Acid Chemistry, The Rockefeller University, New York, NY 10065, USA
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2
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Broeck AV, Klinge S. Principles of human pre-60 S biogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.14.532478. [PMID: 36993238 PMCID: PMC10054963 DOI: 10.1101/2023.03.14.532478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
During early stages of human large ribosomal subunit (60 S ) biogenesis, an ensemble of assembly factors establishes and fine-tunes the essential RNA functional centers of pre-60 S particles by an unknown mechanism. Here, we report a series of cryo-electron microscopy structures of human nucleolar and nuclear pre-60 S assembly intermediates at resolutions of 2.5-3.2 Ã…. These structures show how protein interaction hubs tether assembly factor complexes to nucleolar particles and how GTPases and ATPases couple irreversible nucleotide hydrolysis steps to the installation of functional centers. Nuclear stages highlight how a conserved RNA processing complex, the rixosome, couples large-scale RNA conformational changes to pre-rRNA processing by the RNA degradation machinery. Our ensemble of human pre-60 S particles provides a rich foundation to elucidate the molecular principles of ribosome formation. One-Sentence Summary High-resolution cryo-EM structures of human pre-60S particles reveal new principles of eukaryotic ribosome assembly.
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3
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Mutational Analysis of the Nsa2 N-Terminus Reveals Its Essential Role in Ribosomal 60S Subunit Assembly. Int J Mol Sci 2020; 21:ijms21239108. [PMID: 33266193 PMCID: PMC7730687 DOI: 10.3390/ijms21239108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 11/23/2020] [Accepted: 11/25/2020] [Indexed: 11/23/2022] Open
Abstract
The ribosome assembly factor Nsa2 is part of the Rea1-Rsa4-Nsa2 interconnected relay on nuclear pre-60S particles that is essential for 60S ribosome biogenesis. Cryo-EM structures depict Nsa2 docked via its C-terminal β-barrel domain to nuclear pre-60S particles, whereas the extended N-terminus, consisting of three α-helical segments, meanders between various 25S rRNA helices with the extreme N-terminus in close vicinity to the Nog1 GTPase center. Here, we tested whether this unappreciated proximity between Nsa2 and Nog1 is of functional importance. Our findings demonstrate that a conservative mutation, Nsa2 Q3N, abolished cell growth and impaired 60S biogenesis. Subsequent genetic and biochemical analyses verified that the Nsa2 N-terminus is required to target Nsa2 to early pre-60S particles. However, overexpression of the Nsa2 N-terminus abolished cytoplasmic recycling of the Nog1 GTPase, and both Nog1 and the Nsa2-N (1-58) construct, but not the respective Nsa2-N (1-58) Q3N mutant, were found arrested on late cytoplasmic pre-60S particles. These findings point to specific roles of the different Nsa2 domains for 60S ribosome biogenesis.
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4
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Klingauf-Nerurkar P, Gillet LC, Portugal-Calisto D, Oborská-Oplová M, Jäger M, Schubert OT, Pisano A, Peña C, Rao S, Altvater M, Chang Y, Aebersold R, Panse VG. The GTPase Nog1 co-ordinates the assembly, maturation and quality control of distant ribosomal functional centers. eLife 2020; 9:52474. [PMID: 31909713 PMCID: PMC6968927 DOI: 10.7554/elife.52474] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 12/20/2019] [Indexed: 01/08/2023] Open
Abstract
Eukaryotic ribosome precursors acquire translation competence in the cytoplasm through stepwise release of bound assembly factors, and proofreading of their functional centers. In case of the pre-60S, these steps include removal of placeholders Rlp24, Arx1 and Mrt4 that prevent premature loading of the ribosomal protein eL24, the protein-folding machinery at the polypeptide exit tunnel (PET), and the ribosomal stalk, respectively. Here, we reveal that sequential ATPase and GTPase activities license release factors Rei1 and Yvh1 to trigger Arx1 and Mrt4 removal. Drg1-ATPase activity removes Rlp24 from the GTPase Nog1 on the pre-60S; consequently, the C-terminal tail of Nog1 is extracted from the PET. These events enable Rei1 to probe PET integrity and catalyze Arx1 release. Concomitantly, Nog1 eviction from the pre-60S permits peptidyl transferase center maturation, and allows Yvh1 to mediate Mrt4 release for stalk assembly. Thus, Nog1 co-ordinates the assembly, maturation and quality control of distant functional centers during ribosome formation.
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Affiliation(s)
| | - Ludovic C Gillet
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | | | - Michaela Oborská-Oplová
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.,Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Martin Jäger
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Olga T Schubert
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Agnese Pisano
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Cohue Peña
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Sanjana Rao
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | | | - Yiming Chang
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Ruedi Aebersold
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.,Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Vikram G Panse
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
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5
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The Conserved RNA Exonuclease Rexo5 Is Required for 3' End Maturation of 28S rRNA, 5S rRNA, and snoRNAs. Cell Rep 2018; 21:758-772. [PMID: 29045842 DOI: 10.1016/j.celrep.2017.09.067] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 07/16/2017] [Accepted: 09/20/2017] [Indexed: 12/21/2022] Open
Abstract
Non-coding RNA biogenesis in higher eukaryotes has not been fully characterized. Here, we studied the Drosophila melanogaster Rexo5 (CG8368) protein, a metazoan-specific member of the DEDDh 3'-5' single-stranded RNA exonucleases, by genetic, biochemical, and RNA-sequencing approaches. Rexo5 is required for small nucleolar RNA (snoRNA) and rRNA biogenesis and is essential in D. melanogaster. Loss-of-function mutants accumulate improperly 3' end-trimmed 28S rRNA, 5S rRNA, and snoRNA precursors in vivo. Rexo5 is ubiquitously expressed at low levels in somatic metazoan cells but extremely elevated in male and female germ cells. Loss of Rexo5 leads to increased nucleolar size, genomic instability, defective ribosome subunit export, and larval death. Loss of germline expression compromises gonadal growth and meiotic entry during germline development.
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6
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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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7
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Bentov Y, Jurisicova A, Kenigsberg S, Casper RF. What maintains the high intra-follicular estradiol concentration in pre-ovulatory follicles? J Assist Reprod Genet 2015; 33:85-94. [PMID: 26552664 DOI: 10.1007/s10815-015-0612-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 10/28/2015] [Indexed: 12/13/2022] Open
Abstract
PURPOSE The purpose of the study was to establish the mechanism by which the estrogen concentration difference between the follicular fluid and the serum is maintained. METHODS We used dialysis membrane with a pore size of <3 KD to characterize the estrogen-binding capacity of the follicular fluid. We performed PCR, western blot, and ELISA on luteinized granulosa cells to determine if sex hormone-binding globulin (SHBG) is produced by granulosa cells, and finally we used affinity columns and mass spectrometry to identify the estrogen-binding protein in the follicular fluid. RESULTS We found that a significant estrogen concentration difference is maintained in a cell-free system and is lost with proteolysis of the follicular fluid proteins. Luteinized granulosa cells are likely not a source of SHBG, as we were not able to detect expression of SHBG in these cells. Perlecan was the most highly enriched follicular fluid protein in the affinity columns. CONCLUSIONS We were able to identify perlecan as the most likely candidate for the major estrogen-binding protein in the follicular fluid.
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Affiliation(s)
- Yaakov Bentov
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada. .,Toronto Center for Assisted Reproductive Technologies, Toronto, Canada. .,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada.
| | - Andrea Jurisicova
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
| | - Shlomit Kenigsberg
- CReATe Fertility Centre, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
| | - Robert F Casper
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Toronto Center for Assisted Reproductive Technologies, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
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8
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Yoshikawa H, Ishikawa H, Izumikawa K, Miura Y, Hayano T, Isobe T, Simpson RJ, Takahashi N. Human nucleolar protein Nop52 (RRP1/NNP-1) is involved in site 2 cleavage in internal transcribed spacer 1 of pre-rRNAs at early stages of ribosome biogenesis. Nucleic Acids Res 2015; 43:5524-36. [PMID: 25969445 PMCID: PMC4477673 DOI: 10.1093/nar/gkv470] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 04/29/2015] [Indexed: 01/02/2023] Open
Abstract
During the early steps of ribosome biogenesis in mammals, the two ribosomal subunits 40S and 60S are produced via splitting of the large 90S pre-ribosomal particle (90S) into pre-40S and pre-60S pre-ribosomal particles (pre-40S and pre-60S). We previously proposed that replacement of fibrillarin by Nop52 (RRP1/NNP-1) for the binding to p32 (C1QBP) is a key event that drives this splitting process. However, how the replacement by RRP1 is coupled with the endo- and/or exo-ribonucleolytic cleavage of pre-rRNA remains unknown. In this study, we demonstrate that RRP1 deficiency suppressed site 2 cleavage on ITS1 of 47S/45S, 41S and 36S pre-rRNAs in human cells. RRP1 was also present in 90S and was localized in the dense fibrillar component of the nucleolus dependently on active RNA polymerase I transcription. In addition, double knockdown of XRN2 and RRP1 revealed that RRP1 accelerated the site 2 cleavage of 47S, 45S and 41S pre-rRNAs. These data suggest that RRP1 is involved not only in competitive binding with fibrillarin to C1QBP on 90S but also in site 2 cleavage in ITS1 of pre-rRNAs at early stages of human ribosome biogenesis; thus, it is likely that RRP1 integrates the cleavage of site 2 with the physical split of 90S into pre-40S and pre-60S.
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Affiliation(s)
- Harunori Yoshikawa
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Centre for Gene Regulation & Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Hideaki Ishikawa
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan
| | - Keiichi Izumikawa
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan
| | - Yutaka Miura
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Toshiya Hayano
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Toshiaki Isobe
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan Department of Chemistry, Graduate School of Sciences and Engineering, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachiouji-shi, Tokyo 192-0397, Japan
| | - Richard J Simpson
- La Trobe Institute for Molecular Science (LIMS), LIMS Building 1, Room 412 La Trobe University, Bundoora Victoria 3086, Australia
| | - Nobuhiro Takahashi
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan
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9
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Wang M, Anikin L, Pestov DG. Two orthogonal cleavages separate subunit RNAs in mouse ribosome biogenesis. Nucleic Acids Res 2014; 42:11180-91. [PMID: 25190460 PMCID: PMC4176171 DOI: 10.1093/nar/gku787] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Ribosome biogenesis is a dynamic multistep process, many features of which are still incompletely documented. Here, we show that changes in this pathway can be captured and annotated by means of a graphic set of pre-rRNA ratios, a technique we call Ratio Analysis of Multiple Precursors (RAMP). We find that knocking down a ribosome synthesis factor produces a characteristic RAMP profile that exhibits consistency across a range of depletion levels. This facilitates the inference of affected steps and simplifies comparative analysis. We applied RAMP to examine how endonucleolytic cleavages of the mouse pre-rRNA transcript in the internal transcribed spacer 1 (ITS1) are affected by depletion of factors required for maturation of the small ribosomal subunit (Rcl1, Fcf1/Utp24, Utp23) and the large subunit (Pes1, Nog1). The data suggest that completion of early maturation in a subunit triggers its release from the common pre-rRNA transcript by stimulating cleavage at the proximal site in ITS1. We also find that splitting of pre-rRNA in the 3' region of ITS1 is prevalent in adult mouse tissues and quiescent cells, as it is in human cells. We propose a model for subunit separation during mammalian ribosome synthesis and discuss its implications for understanding pre-rRNA processing pathways.
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Affiliation(s)
- Minshi Wang
- Department of Cell Biology, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA Graduate School of Biomedical Sciences, Rowan University, Stratford, NJ 08084, USA
| | - Leonid Anikin
- Department of Cell Biology, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA Graduate School of Biomedical Sciences, Rowan University, Stratford, NJ 08084, USA
| | - Dimitri G Pestov
- Department of Cell Biology, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
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10
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Kim YI, Bandyopadhyay J, Cho I, Lee J, Park DH, Cho JH. Nucleolar GTPase NOG-1 regulates development, fat storage, and longevity through insulin/IGF signaling in C. elegans. Mol Cells 2014; 37:51-7. [PMID: 24552710 PMCID: PMC3907010 DOI: 10.14348/molcells.2014.2251] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 11/28/2013] [Accepted: 11/29/2013] [Indexed: 12/11/2022] Open
Abstract
NOG1 is a nucleolar GTPase that is critical for 60S ribosome biogenesis. Recently, NOG1 was identified as one of the downstream regulators of target of rapamycin (TOR) in yeast. It is reported that TOR is involved in regulating lifespan and fat storage in Caenorhabditis elegans. Here, we show that the nog1 ortholog (T07A9.9: nog-1) in C. elegans regulates growth, development, lifespan, and fat metabolism. A green fluorescence protein (GFP) promoter assay revealed ubiquitous expression of C. elegans nog-1 from the early embryonic to the adult stage. Furthermore, the GFP-tagged NOG-1 protein is localized to the nucleus, whereas the aberrant NOG-1 protein is concentrated in the nucleolus. Functional studies of NOG-1 in C. elegans further revealed that nog-1 knockdown resulted in smaller broodsize, slower growth, increased life span, and more fat storage. Moreover, nog-1 over-expression resulted in decreased life span. Taken together, our data suggest that nog-1 in C. elegans may be an important player in regulating life span and fat storage via the insulin/IGF pathway.
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Affiliation(s)
- Young-Il Kim
- Biomedical Research Center, Korea Advanced Institute of Science and Technology, Daejeon 305-701,
Korea
| | - Jaya Bandyopadhyay
- Department of Biotechnology, West Bengal University of Technology, Salt Lake City, Kolkata 700-064,
India
| | - Injeong Cho
- Department of Biology Education, College of Education, Chosun University, Gwangju 501-759,
Korea
| | - Juyeon Lee
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712,
Korea
| | - Dae Ho Park
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712,
Korea
| | - Jeong Hoon Cho
- Department of Biology Education, College of Education, Chosun University, Gwangju 501-759,
Korea
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11
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Matsuo Y, Granneman S, Thoms M, Manikas RG, Tollervey D, Hurt E. Coupled GTPase and remodelling ATPase activities form a checkpoint for ribosome export. Nature 2013; 505:112-116. [PMID: 24240281 PMCID: PMC3880858 DOI: 10.1038/nature12731] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 10/03/2013] [Indexed: 01/05/2023]
Abstract
Eukaryotic ribosomes are assembled by a complex pathway that extends from the nucleolus to the cytoplasm and is powered by many energy-consuming enzymes 1-3. Nuclear export is a key, irreversible step in pre-ribosome maturation4-8, but mechanisms underlying the timely acquisition of export competence remain poorly understood. Here we show that a conserved GTPase Nug2/Nog2 (called NGP-1, Gnl2 or nucleostemin 2 in human9) plays a key role in the timing of export competence. Nug2 binds the inter-subunit face of maturing, nucleoplasmic pre-60S particles, and the location clashes with the position of Nmd3, a key pre-60S export adaptor10. Nug2 and Nmd3 are not present on the same pre-60S particles, with Nug2 binding prior to Nmd3. Depletion of Nug2 causes premature Nmd3 binding to the pre-60S particles, whereas mutations in the G-domain of Nug2 block Nmd3 recruitment, resulting in severe 60S export defects. Two pre-60S remodeling factors, the Rea1 ATPase and its co-substrate Rsa4, are present on Nug2-associated particles, and both show synthetic lethal interactions with nug2 mutants. Release of Nug2 from pre-60S particles requires both its K+-dependent GTPase activity and the remodeling ATPase activity of Rea1. We conclude that Nug2 is a regulatory GTPase that monitors pre-60S maturation, with release from its placeholder site linked to recruitment of the nuclear export machinery.
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Affiliation(s)
- Yoshitaka Matsuo
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
| | - Sander Granneman
- Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh UK.,Centre for Synthetic and Systems Biology (SynthSys), University of Edinburgh, Edinburgh, UK
| | - Matthias Thoms
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
| | - Rizos-Georgios Manikas
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
| | - David Tollervey
- Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh UK
| | - Ed Hurt
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
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12
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Kint CI, Verstraeten N, Wens I, Liebens VR, Hofkens J, Versées W, Fauvart M, Michiels J. The Escherichia coli GTPase ObgE modulates hydroxyl radical levels in response to DNA replication fork arrest. FEBS J 2012; 279:3692-3704. [PMID: 22863262 DOI: 10.1111/j.1742-4658.2012.08731.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Obg proteins are universally conserved GTP-binding proteins that are essential for viability in bacteria. Homologs in different organisms are involved in various cellular processes, including DNA replication. The goal of this study was to analyse the structure-function relationship of Escherichia coli ObgE with regard to DNA replication in general and sensitivity to stalled replication forks in particular. Defined C-terminal chromosomal deletion mutants of obgE were constructed and tested for sensitivity to the replication inhibitor hydroxyurea. The ObgE C-terminal domain was shown to be dispensable for normal growth of E.coli. However, a region within this domain is involved in the cellular response to replication fork stress. In addition, a mutant obgE over-expression library was constructed by error-prone PCR and screened for increased hydroxyurea sensitivity. ObgE proteins with substitutions L159Q, G163V, P168V, G216A or R237C, located within distinct domains of ObgE, display dominant-negative effects leading to hydroxyurea hypersensitivity when over-expressed. These effects are abolished in strains with a single deletion of the iron transporter TonB or combined deletions the toxin/antitoxin modules RelBE/MazEF, strains both of which have been shown to be involved in a pathway that stimulates hydroxyl radical formation following hydroxyurea treatment. Moreover, the observed dominant-negative effects are lost in the presence of the hydroxyl radical scavenger thiourea. Together, these results indicate involvement of hydroxyl radical toxicity in ObgE-mediated protection against replication fork stress.
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Affiliation(s)
- Cyrielle I Kint
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Natalie Verstraeten
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Inez Wens
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Veerle R Liebens
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Johan Hofkens
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Wim Versées
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Maarten Fauvart
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
| | - Jan Michiels
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium Structural Biology Brussels, Vrije Universiteit Brussel, Belgium Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
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13
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Bang WY, Chen J, Jeong IS, Kim SW, Kim CW, Jung HS, Lee KH, Kweon HS, Yoko I, Shiina T, Bahk JD. Functional characterization of ObgC in ribosome biogenesis during chloroplast development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 71:122-34. [PMID: 22380942 DOI: 10.1111/j.1365-313x.2012.04976.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The Spo0B-associated GTP-binding protein (Obg) GTPase, essential for bacterial viability, is also conserved in eukaryotes, but its primary role in eukaryotes remains unknown. Here, our functional characterization of Arabidopsis and rice obgc mutants strongly underlines the evolutionarily conserved role of eukaryotic Obgs in organellar ribosome biogenesis. The mutants exhibited a chlorotic phenotype, caused by retarded chloroplast development. A plastid DNA macroarray revealed a plastid-encoded RNA polymerase (PEP) deficiency in an obgc mutant, caused by incompleteness of the PEP complex, as its western blot exhibited reduced levels of RpoA protein, a component of PEP. Plastid rRNA profiling indicated that plastid rRNA processing is defective in obgc mutants, probably resulting in impaired ribosome biogenesis and, in turn, in reduced levels of RpoA protein. RNA co-immunoprecipitation revealed that ObgC specifically co-precipitates with 23S rRNA in vivo. These findings indicate that ObgC functions primarily in plastid ribosome biogenesis during chloroplast development. Furthermore, complementation analysis can provide new insights into the functional modes of three ObgC domains, including the Obg fold, G domain and OCT.
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Affiliation(s)
- Woo Young Bang
- Swine Science and Technology Center, Gyeongnam National University of Science and Technology-GNTECH, Jinju 660-758, Korea
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Sasindran SJ, Saikolappan S, Scofield VL, Dhandayuthapani S. Biochemical and physiological characterization of the GTP-binding protein Obg of Mycobacterium tuberculosis. BMC Microbiol 2011; 11:43. [PMID: 21352546 PMCID: PMC3056739 DOI: 10.1186/1471-2180-11-43] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 02/25/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Obg is a highly conserved GTP-binding protein that has homologues in bacteria, archaea and eukaryotes. In bacteria, Obg proteins are essential for growth, and they participate in spore formation, stress adaptation, ribosome assembly and chromosomal partitioning. This study was undertaken to investigate the biochemical and physiological characteristics of Obg in Mycobacterium tuberculosis, which causes tuberculosis in humans. RESULTS We overexpressed M. tuberculosis Obg in Escherichia coli and then purified the protein. This protein binds to, hydrolyzes and is phosphorylated with GTP. An anti-Obg antiserum, raised against the purified Obg, detects a 55 kDa protein in immunoblots of M. tuberculosis extracts. Immunoblotting also discloses that cultured M. tuberculosis cells contain increased amounts of Obg in the late log phase and in the stationary phase. Obg is also associated with ribosomes in M. tuberculosis, and it is distributed to all three ribosomal fractions (30 S, 50 S and 70 S). Finally, yeast two-hybrid analysis reveals that Obg interacts with the stress protein UsfX, indicating that M. tuberculosis Obg, like other bacterial Obgs, is a stress related protein. CONCLUSIONS Although its GTP-hydrolyzing and phosphorylating activities resemble those of other bacterial Obg homologues, M. tuberculosis Obg differs from them in these respects: (a) preferential association with the bacterial membrane; (b) association with all three ribosomal subunits, and (c) binding to the stress protein UsfX, rather than to RelA. Generation of mutant alleles of Obg of M. tuberculosis, and their characterization in vivo, may provide additional insights regarding its role in this important human pathogen.
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Affiliation(s)
- Smitha J Sasindran
- Regional Academic Health Center and Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, Edinburg, Texas 78541, USA
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Wang M, Pestov DG. 5'-end surveillance by Xrn2 acts as a shared mechanism for mammalian pre-rRNA maturation and decay. Nucleic Acids Res 2010; 39:1811-22. [PMID: 21036871 PMCID: PMC3061060 DOI: 10.1093/nar/gkq1050] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Ribosome biogenesis requires multiple nuclease activities to process pre-rRNA transcripts into mature rRNA species and eliminate defective products of transcription and processing. We find that in mammalian cells, the 5′ exonuclease Xrn2 plays a major role in both maturation of rRNA and degradation of a variety of discarded pre-rRNA species. Precursors of 5.8S and 28S rRNAs containing 5′ extensions accumulate in mouse cells after siRNA-mediated knockdown of Xrn2, indicating similarity in the 5′-end maturation mechanisms between mammals and yeast. Strikingly, degradation of many aberrant pre-rRNA species, attributed mainly to 3′ exonucleases in yeast studies, occurs 5′ to 3′ in mammalian cells and is mediated by Xrn2. Furthermore, depletion of Xrn2 reveals pre-rRNAs derived by cleavage events that deviate from the main processing pathway. We propose that probing of pre-rRNA maturation intermediates by exonucleases serves the dual function of generating mature rRNAs and suppressing suboptimal processing paths during ribosome assembly.
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Affiliation(s)
- Minshi Wang
- Department of Cell Biology, University of Medicine and Dentistry of New Jersey, Stratford, NJ 08084, USA
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Mammalian DEAD box protein Ddx51 acts in 3' end maturation of 28S rRNA by promoting the release of U8 snoRNA. Mol Cell Biol 2010; 30:2947-56. [PMID: 20404093 DOI: 10.1128/mcb.00226-10] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biogenesis of eukaryotic ribosomes requires a number of RNA helicases that drive molecular rearrangements at various points of the assembly pathway. While many ribosome synthesis factors are conserved among all eukaryotes, certain features of ribosome maturation, such as U8 snoRNA-assisted processing of the 5.8S and 28S rRNA precursors, are observed only in metazoan cells. Here, we identify the mammalian DEAD box helicase family member Ddx51 as a novel ribosome synthesis factor and an interacting partner of the nucleolar GTP-binding protein Nog1. Unlike any previously studied yeast helicases, Ddx51 is required for the formation of the 3' end of 28S rRNA. Ddx51 binds to pre-60S subunit complexes and promotes displacement of U8 snoRNA from pre-rRNA, which is necessary for the removal of the 3' external transcribed spacer from 28S rRNA and productive downstream processing. These data demonstrate the emergence of a novel factor that facilitates a pre-rRNA processing event specific for higher eukaryotes.
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A genome-scale protein interaction profile of Drosophila p53 uncovers additional nodes of the human p53 network. Proc Natl Acad Sci U S A 2010; 107:6322-7. [PMID: 20308539 DOI: 10.1073/pnas.1002447107] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The genome of the fruitfly Drosophila melanogaster contains a single p53-like protein, phylogenetically related to the ancestor of the mammalian p53 family of tumor suppressors. We reasoned that a comprehensive map of the protein interaction profile of Drosophila p53 (Dmp53) might help identify conserved interactions of the entire p53 family in man. Using a genome-scale in vitro expression cloning approach, we identified 91 previously unreported Dmp53 interactors, considerably expanding the current Drosophila p53 interactome. Looking for evolutionary conservation of these interactions, we tested 41 mammalian orthologs and found that 37 bound to one or more p53-family members when overexpressed in human cells. An RNAi-based functional assay for modulation of the p53 pathway returned five positive hits, validating the biological relevance of these interactions. One p53 interactor is GTPBP4, a nucleolar protein involved in 60S ribosome biogenesis. We demonstrate that GTPBP4 knockdown induces p53 accumulation and activation in the absence of nucleolar disruption. In breast tumors with wild-type p53, increased expression of GTPBP4 correlates with reduced patient survival, emphasizing a potential relevance of this regulatory axis in cancer.
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Saccharomyces cerevisiae Rbg1 protein and its binding partner Gir2 interact on Polyribosomes with Gcn1. EUKARYOTIC CELL 2009; 8:1061-71. [PMID: 19448108 DOI: 10.1128/ec.00356-08] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Rbg1 is a previously uncharacterized protein of Saccharomyces cerevisiae belonging to the Obg/CgtA subfamily of GTP-binding proteins whose members are involved in ribosome function in both prokaryotes and eukaryotes. We show here that Rbg1 specifically associates with translating ribosomes. In addition, in this study proteins were identified that interact with Rbg1 by yeast two-hybrid screening and include Tma46, Ygr250c, Yap1, and Gir2. Gir2 contains a GI (Gcn2 and Impact) domain similar to that of Gcn2, an essential factor of the general amino acid control pathway required for overcoming amino acid shortage. Interestingly, we found that Gir2, like Gcn2, interacts with Gcn1 through its GI domain, and overexpression of Gir2, under conditions mimicking amino acid starvation, resulted in inhibition of growth that could be reversed by Gcn2 co-overexpression. Moreover, we found that Gir2 also cofractionated with polyribosomes, and this fractionation pattern was partially dependent on the presence of Gcn1. Based on these findings, we conclude that Rbg1 and its interacting partner Gir2 associate with ribosomes, and their possible biological roles are discussed.
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