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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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2
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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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3
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Sun Y, Gao T, Zhang S, Zhang Y, Tian Q. TINP1 homolog is required for planarian regeneration. Biosci Biotechnol Biochem 2019; 83:1248-1254. [DOI: 10.1080/09168451.2019.1594677] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
ABSTRACT
The planarian flatworm is an ideal system for the study of regeneration in vivo. In this study, we focus on TINP1, which is one of the most conserved proteins in eukaryotic organisms. We found that TINP1 was expressed in parenchymal region through whole body as well as central nervous system (CNS) during the course of regeneration. RNA interference targeting DjTINP1 caused lysis defects in regenerating tissues and a decreased in cell division and expression levels of DjpiwiA and Djpcna. Furthermore, the expression levels of DjTINP1 were decreased when we inhibited the TGF-β signal by knockdown of smad4, which is the sole co-smad and has been proved to control the blastema patterning and central nervous system (CNS) regeneration in planarians. These findings suggest that DjTINP1 participate in the maintenance of neoblasts and be required for proper cell proliferation in planarians as a downstream gene of the TGF-β signal pathway.
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Affiliation(s)
- Yujia Sun
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Tingting Gao
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Shoutao Zhang
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Yizhe Zhang
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Qingnan Tian
- School of Life Sciences, Zhengzhou University, Zhengzhou, Henan, China
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4
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Nop-7-associated 2 (NSA2) is required for ribosome biogenesis and protein synthesis. Biochem Biophys Res Commun 2018; 505:249-254. [PMID: 30243719 DOI: 10.1016/j.bbrc.2018.09.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 09/07/2018] [Indexed: 12/11/2022]
Abstract
Ribosome biogenesis is a fundamental cellular process and occurs mainly in the nucleolus in eukaryotes. The process is exceptionally complex and highly regulated by numerous ribosomal and non-ribosomal factors. A recent discovery strengthened the link between ribosome biogenesis and malignant transformation. Here, we determined that Nop-7-associated 2 (NSA2) is a nucleolar protein required for ribosome biogenesis. NSA2 knockdown reduced the rate of rRNA synthesis, diminishing the 60S ribosomal subunit. Moreover, we demonstrated that depletion of NSA2 suppressed protein synthesis. To investigate the signaling pathway affected by NSA2, NSA2 was depleted, which triggered the inactivation of the mTOR signaling pathway. Taken together, our findings reveal a novel function of NSA2 and provide insight into the regulation of ribosome biogenesis by NSA2.
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5
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Biedka S, Micic J, Wilson D, Brown H, Diorio-Toth L, Woolford JL. Hierarchical recruitment of ribosomal proteins and assembly factors remodels nucleolar pre-60S ribosomes. J Cell Biol 2018; 217:2503-2518. [PMID: 29691304 PMCID: PMC6028539 DOI: 10.1083/jcb.201711037] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 02/20/2018] [Accepted: 03/29/2018] [Indexed: 01/24/2023] Open
Abstract
Ribosome biogenesis involves numerous pre-rRNA processing events to remove internal and external transcribed spacer sequences, ultimately yielding three mature rRNAs. Biedka et al. show that ribosomal proteins and assembly factors remodel several neighborhoods, including two 60S ribosomal subunit functional centers, during removal of the ITS2 spacer RNA. Ribosome biogenesis involves numerous preribosomal RNA (pre-rRNA) processing events to remove internal and external transcribed spacer sequences, ultimately yielding three mature rRNAs. Removal of the internal transcribed spacer 2 spacer RNA is the final step in large subunit pre-rRNA processing and begins with endonucleolytic cleavage at the C2 site of 27SB pre-rRNA. C2 cleavage requires the hierarchical recruitment of 11 ribosomal proteins and 14 ribosome assembly factors. However, the function of these proteins in C2 cleavage remained unclear. In this study, we have performed a detailed analysis of the effects of depleting proteins required for C2 cleavage and interpreted these results using cryo–electron microscopy structures of assembling 60S subunits. This work revealed that these proteins are required for remodeling of several neighborhoods, including two major functional centers of the 60S subunit, suggesting that these remodeling events form a checkpoint leading to C2 cleavage. Interestingly, when C2 cleavage is directly blocked by depleting or inactivating the C2 endonuclease, assembly progresses through all other subsequent steps.
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Affiliation(s)
- Stephanie Biedka
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA
| | - Jelena Micic
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA
| | - Daniel Wilson
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA
| | - Hailey Brown
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA
| | - Luke Diorio-Toth
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA
| | - John L Woolford
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA
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6
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High-throughput RNA structure probing reveals critical folding events during early 60S ribosome assembly in yeast. Nat Commun 2017; 8:714. [PMID: 28959008 PMCID: PMC5620067 DOI: 10.1038/s41467-017-00761-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 07/26/2017] [Indexed: 11/25/2022] Open
Abstract
While the protein composition of various yeast 60S ribosomal subunit assembly intermediates has been studied in detail, little is known about ribosomal RNA (rRNA) structural rearrangements that take place during early 60S assembly steps. Using a high-throughput RNA structure probing method, we provide nucleotide resolution insights into rRNA structural rearrangements during nucleolar 60S assembly. Our results suggest that many rRNA-folding steps, such as folding of 5.8S rRNA, occur at a very specific stage of assembly, and propose that downstream nuclear assembly events can only continue once 5.8S folding has been completed. Our maps of nucleotide flexibility enable making predictions about the establishment of protein–rRNA interactions, providing intriguing insights into the temporal order of protein–rRNA as well as long-range inter-domain rRNA interactions. These data argue that many distant domains in the rRNA can assemble simultaneously during early 60S assembly and underscore the enormous complexity of 60S synthesis. Ribosome biogenesis is a dynamic process that involves the ordered assembly of ribosomal proteins and numerous RNA structural rearrangements. Here the authors apply ChemModSeq, a high-throughput RNA structure probing method, to quantitatively measure changes in RNA flexibility during the nucleolar stages of 60S assembly in yeast.
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Konikkat S, Biedka S, Woolford JL. The assembly factor Erb1 functions in multiple remodeling events during 60S ribosomal subunit assembly in S. cerevisiae. Nucleic Acids Res 2017; 45:4853-4865. [PMID: 28115637 PMCID: PMC5416829 DOI: 10.1093/nar/gkw1361] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 01/19/2017] [Indexed: 11/14/2022] Open
Abstract
A major gap in our understanding of ribosome assembly is knowing the precise function of each of the ∼200 assembly factors. The steps in subunit assembly in which these factors participate have been examined for the most part by depleting each protein from cells. Depletion of the assembly factor Erb1 prevents stable assembly of seven other interdependent assembly factors with pre-60S subunits, resulting in turnover of early preribosomes, before the ITS1 spacer can be removed from 27SA3 pre-rRNA. To investigate more specific functions of Erb1, we constructed eight internal deletions of 40-60 amino acid residues each, spanning the amino-terminal half of Erb1. The erb1Δ161-200 and erb1Δ201-245 deletion mutations block a later step than depletion of Erb1, namely cleavage of the C2 site that initiates removal of the ITS2 spacer. Two other remodeling events fail to occur in these erb1 mutants: association of twelve different assembly factors with domain V of 25S rRNA, including the neighborhood surrounding the peptidyl transferase center, and stable association of ribosomal proteins with rRNA surrounding the polypeptide exit tunnel. This suggests that successful initiation of construction of these functional centers is a checkpoint for committing to spacer removal.
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Affiliation(s)
- Salini Konikkat
- Department of Biological Sciences, Carnegie Mellon University, 616 Mellon Institute, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Stephanie Biedka
- Department of Biological Sciences, Carnegie Mellon University, 616 Mellon Institute, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - John L Woolford
- Department of Biological Sciences, Carnegie Mellon University, 616 Mellon Institute, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
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8
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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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9
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Espinar-Marchena FJ, Babiano R, Cruz J. Placeholder factors in ribosome biogenesis: please, pave my way. MICROBIAL CELL 2017; 4:144-168. [PMID: 28685141 PMCID: PMC5425277 DOI: 10.15698/mic2017.05.572] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The synthesis of cytoplasmic eukaryotic ribosomes is an extraordinarily energy-demanding cellular activity that occurs progressively from the nucleolus to the cytoplasm. In the nucleolus, precursor rRNAs associate with a myriad of trans-acting factors and some ribosomal proteins to form pre-ribosomal particles. These factors include snoRNPs, nucleases, ATPases, GTPases, RNA helicases, and a vast list of proteins with no predicted enzymatic activity. Their coordinate activity orchestrates in a spatiotemporal manner the modification and processing of precursor rRNAs, the rearrangement reactions required for the formation of productive RNA folding intermediates, the ordered assembly of the ribosomal proteins, and the export of pre-ribosomal particles to the cytoplasm; thus, providing speed, directionality and accuracy to the overall process of formation of translation-competent ribosomes. Here, we review a particular class of trans-acting factors known as "placeholders". Placeholder factors temporarily bind selected ribosomal sites until these have achieved a structural context that is appropriate for exchanging the placeholder with another site-specific binding factor. By this strategy, placeholders sterically prevent premature recruitment of subsequently binding factors, premature formation of structures, avoid possible folding traps, and act as molecular clocks that supervise the correct progression of pre-ribosomal particles into functional ribosomal subunits. We summarize the current understanding of those factors that delay the assembly of distinct ribosomal proteins or subsequently bind key sites in pre-ribosomal particles. We also discuss recurrent examples of RNA-protein and protein-protein mimicry between rRNAs and/or factors, which have clear functional implications for the ribosome biogenesis pathway.
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Affiliation(s)
- Francisco J Espinar-Marchena
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, E-41013, Seville, Spain
| | - Reyes Babiano
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, E-41013, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, E-41013, Seville, Spain
| | - Jesús Cruz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, and Departamento de Genética, Universidad de Sevilla, E-41013, Seville, Spain
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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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Manikas RG, Thomson E, Thoms M, Hurt E. The K⁺-dependent GTPase Nug1 is implicated in the association of the helicase Dbp10 to the immature peptidyl transferase centre during ribosome maturation. Nucleic Acids Res 2016; 44:1800-12. [PMID: 26823502 PMCID: PMC4770245 DOI: 10.1093/nar/gkw045] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 01/14/2016] [Indexed: 12/16/2022] Open
Abstract
Ribosome synthesis employs a number of energy-consuming enzymes in both eukaryotes and prokaryotes. One such enzyme is the conserved circularly permuted GTPase Nug1 (nucleostemin in human). Nug1 is essential for 60S subunit assembly and nuclear export, but its role and time of action during maturation remained unclear. Based on in vitro enzymatic assays using the Chaetomium thermophilum (Ct) orthologue, we show that Nug1 exhibits a low intrinsic GTPase activity that is stimulated by potassium ions, rendering Nug1 a cation-dependent GTPase. In vivo we observe 60S biogenesis defects upon depletion of yeast Nug1 or expression of a Nug1 nucleotide-binding mutant. Most prominently, the RNA helicase Dbp10 was lost from early pre-60S particles, which suggested a physical interaction that could be reconstituted in vitro using CtNug1 and CtDbp10. In vivo rRNA-protein crosslinking revealed that Nug1 and Dbp10 bind at proximal and partially overlapping sites on the 60S pre-ribosome, most prominently to H89 that will constitute part of the peptidyl transferase center (PTC). The binding sites of Dbp10 are the same as those identified for the prokaryotic helicase DbpA bound to the 50S subunit. We suggest that Dbp10 and DbpA are performing a conserved role during PTC formation in all organisms.
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Affiliation(s)
- Rizos-Georgios Manikas
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
| | - Emma Thomson
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
| | - Matthias Thoms
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
| | - Ed Hurt
- Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, Heidelberg D-69120, Germany
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12
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Ohmayer U, Gil-Hernández Á, Sauert M, Martín-Marcos P, Tamame M, Tschochner H, Griesenbeck J, Milkereit P. Studies on the Coordination of Ribosomal Protein Assembly Events Involved in Processing and Stabilization of Yeast Early Large Ribosomal Subunit Precursors. PLoS One 2015; 10:e0143768. [PMID: 26642313 PMCID: PMC4671574 DOI: 10.1371/journal.pone.0143768] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 11/09/2015] [Indexed: 12/11/2022] Open
Abstract
Cellular production of ribosomes involves the formation of highly defined interactions between ribosomal proteins (r-proteins) and ribosomal RNAs (rRNAs). Moreover in eukaryotic cells, efficient ribosome maturation requires the transient association of a large number of ribosome biogenesis factors (RBFs) with newly forming ribosomal subunits. Here, we investigated how r-protein assembly events in the large ribosomal subunit (LSU) rRNA domain II are coordinated with each other and with the association of RBFs in early LSU precursors of the yeast Saccharomyces cerevisiae. Specific effects on the pre-ribosomal association of RBFs could be observed in yeast mutants blocked in LSU rRNA domain II assembly. Moreover, formation of a cluster of r-proteins was identified as a downstream event in LSU rRNA domain II assembly. We analyzed in more detail the functional relevance of eukaryote specific bridges established by this r-protein cluster between LSU rRNA domain II and VI and discuss how they can support the stabilization and efficient processing of yeast early LSU precursor RNAs.
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Affiliation(s)
- Uli Ohmayer
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Álvaro Gil-Hernández
- Instituto de Biología Funcional y Genómica (IBFG), CSIC/Universidad de Salamanca, Salamanca, Spain
| | - Martina Sauert
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
| | - Pilar Martín-Marcos
- Instituto de Biología Funcional y Genómica (IBFG), CSIC/Universidad de Salamanca, Salamanca, Spain
| | - Mercedes Tamame
- Instituto de Biología Funcional y Genómica (IBFG), CSIC/Universidad de Salamanca, Salamanca, Spain
- * E-mail: (MT); (HT); (JG); (PM)
| | - Herbert Tschochner
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
- * E-mail: (MT); (HT); (JG); (PM)
| | - Joachim Griesenbeck
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
- * E-mail: (MT); (HT); (JG); (PM)
| | - Philipp Milkereit
- Lehrstuhl für Biochemie III, Universität Regensburg, Regensburg, Germany
- * E-mail: (MT); (HT); (JG); (PM)
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13
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Barrio-Garcia C, Thoms M, Flemming D, Kater L, Berninghausen O, Baßler J, Beckmann R, Hurt E. Architecture of the Rix1-Rea1 checkpoint machinery during pre-60S-ribosome remodeling. Nat Struct Mol Biol 2015; 23:37-44. [PMID: 26619264 DOI: 10.1038/nsmb.3132] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 10/30/2015] [Indexed: 01/01/2023]
Abstract
Ribosome synthesis is catalyzed by ∼200 assembly factors, which facilitate efficient production of mature ribosomes. Here, we determined the cryo-EM structure of a Saccharomyces cerevisiae nucleoplasmic pre-60S particle containing the dynein-related 550-kDa Rea1 AAA(+) ATPase and the Rix1 subcomplex. This particle differs from its preceding state, the early Arx1 particle, by two massive structural rearrangements: an ∼180° rotation of the 5S ribonucleoprotein complex and the central protuberance (CP) rRNA helices, and the removal of the 'foot' structure from the 3' end of the 5.8S rRNA. Progression from the Arx1 to the Rix1 particle was blocked by mutational perturbation of the Rix1-Rea1 interaction but not by a dominant-lethal Rea1 AAA(+) ATPase-ring mutant. After remodeling, the Rix1 subcomplex and Rea1 become suitably positioned to sense correct structural maturation of the CP, which allows unidirectional progression toward mature ribosomes.
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Affiliation(s)
| | - Matthias Thoms
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Dirk Flemming
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | - Lukas Kater
- Gene Center, University of Munich, Munich, Germany
| | | | - Jochen Baßler
- Heidelberg University Biochemistry Center, Heidelberg, Germany
| | | | - Ed Hurt
- Heidelberg University Biochemistry Center, Heidelberg, Germany
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14
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Li X, Jiang Y, Ji Z, Liu Y, Zhang Q. BRHIS1 suppresses rice innate immunity through binding to monoubiquitinated H2A and H2B variants. EMBO Rep 2015. [PMID: 26202491 DOI: 10.15252/embr.201440000] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In the absence of pathogen attack, organisms usually suppress immune responses to reduce the negative effects of disease resistance. Monoubiquitination of histone variants at specific gene loci is crucial for gene expression, but its involvement in the regulation of plant immunity remains unclear. Here, we show that a rice SWI/SNF2 ATPase gene BRHIS1 is downregulated in response to the rice blast fungal pathogen or to the defense-priming-inducing compound BIT (1,2-benzisothiazol-3(2h)-one,1, 1-dioxide). The BRHIS1-containing complex represses the expression of some disease defense-related genes, including the pathogenesis-related gene OsPBZc and the leucine-rich-repeat (LRR) receptor-like protein kinase gene OsSIRK1. This is achieved through BRHIS1 recruitment to the promoter regions of target genes through specific interaction with monoubiquitinated histone variants H2B.7 and H2A.Xa/H2A.Xb/H2A.3, in the absence of pathogen attack or BIT treatment. Our results show that rice disease defense genes are initially organized in an expression-ready state by specific monoubiquitination of H2A and H2B variants deposited on their promoter regions, but are kept suppressed by the BRHIS1 complex, facilitating the prompt initiation of innate immune responses in response to infection through the stringent regulation of BRHIS1.
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Affiliation(s)
- Xiaoyu Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China Key Laboratory of Plant Functional Genomics and Biotechnology of Guangdong Provincial Higher Education Institutions, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Yanxiang Jiang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China Key Laboratory of Plant Functional Genomics and Biotechnology of Guangdong Provincial Higher Education Institutions, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Zhicheng Ji
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China Key Laboratory of Plant Functional Genomics and Biotechnology of Guangdong Provincial Higher Education Institutions, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Yaoguang Liu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China Key Laboratory of Plant Functional Genomics and Biotechnology of Guangdong Provincial Higher Education Institutions, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Qunyu Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China Key Laboratory of Plant Functional Genomics and Biotechnology of Guangdong Provincial Higher Education Institutions, College of Life Sciences, South China Agricultural University, Guangzhou, China
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15
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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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16
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Abstract
The proteome of cells is synthesized by ribosomes, complex ribonucleoproteins that in eukaryotes contain 79-80 proteins and four ribosomal RNAs (rRNAs) more than 5,400 nucleotides long. How these molecules assemble together and how their assembly is regulated in concert with the growth and proliferation of cells remain important unanswered questions. Here, we review recently emerging principles to understand how eukaryotic ribosomal proteins drive ribosome assembly in vivo. Most ribosomal proteins assemble with rRNA cotranscriptionally; their association with nascent particles is strengthened as assembly proceeds. Each subunit is assembled hierarchically by sequential stabilization of their subdomains. The active sites of both subunits are constructed last, perhaps to prevent premature engagement of immature ribosomes with active subunits. Late-assembly intermediates undergo quality-control checks for proper function. Mutations in ribosomal proteins that affect mostly late steps lead to ribosomopathies, diseases that include a spectrum of cell type-specific disorders that often transition from hypoproliferative to hyperproliferative growth.
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Affiliation(s)
- Jesus de la Cruz
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocio/CSIC/Universidad de Sevilla, E-41013 Sevilla, Spain
- Departamento de Genetica, Universidad de Sevilla, E-41013 Sevilla, Spain
| | - Katrin Karbstein
- Department of Cancer Biology, The Scripps Research Institute, Jupiter, Florida 33458
| | - John L Woolford
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
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17
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Baßler J, Paternoga H, Holdermann I, Thoms M, Granneman S, Barrio-Garcia C, Nyarko A, Lee W, Stier G, Clark SA, Schraivogel D, Kallas M, Beckmann R, Tollervey D, Barbar E, Sinning I, Hurt E. A network of assembly factors is involved in remodeling rRNA elements during preribosome maturation. ACTA ACUST UNITED AC 2014; 207:481-98. [PMID: 25404745 PMCID: PMC4242840 DOI: 10.1083/jcb.201408111] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Eukaryotic ribosome biogenesis involves ∼200 assembly factors, but how these contribute to ribosome maturation is poorly understood. Here, we identify a network of factors on the nascent 60S subunit that actively remodels preribosome structure. At its hub is Rsa4, a direct substrate of the force-generating ATPase Rea1. We show that Rsa4 is connected to the central protuberance by binding to Rpl5 and to ribosomal RNA (rRNA) helix 89 of the nascent peptidyl transferase center (PTC) through Nsa2. Importantly, Nsa2 binds to helix 89 before relocation of helix 89 to the PTC. Structure-based mutations of these factors reveal the functional importance of their interactions for ribosome assembly. Thus, Rsa4 is held tightly in the preribosome and can serve as a "distribution box," transmitting remodeling energy from Rea1 into the developing ribosome. We suggest that a relay-like factor network coupled to a mechano-enzyme is strategically positioned to relocate rRNA elements during ribosome maturation.
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Affiliation(s)
- Jochen Baßler
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Helge Paternoga
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Iris Holdermann
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Matthias Thoms
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Sander Granneman
- Centre for Synthetic and Systems Biology (SynthSys) and Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - Clara Barrio-Garcia
- Gene Center, Department of Chemistry and Biochemistry, University of Munich, 80539 Munich, Germany
| | - Afua Nyarko
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Woonghee Lee
- National Magnetic Resonance Facility; Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706
| | - Gunter Stier
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Sarah A Clark
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Daniel Schraivogel
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Martina Kallas
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Roland Beckmann
- Gene Center, Department of Chemistry and Biochemistry, University of Munich, 80539 Munich, Germany
| | - David Tollervey
- Centre for Synthetic and Systems Biology (SynthSys) and Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - Elisar Barbar
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Irmi Sinning
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
| | - Ed Hurt
- Biochemistry Center of Heidelberg University, INF328, D-69120 Heidelberg, Germany
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18
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Wang Y, Sun H, Du W, Blanzieri E, Viero G, Xu Y, Liang Y. Identification of essential proteins based on ranking edge-weights in protein-protein interaction networks. PLoS One 2014; 9:e108716. [PMID: 25268881 PMCID: PMC4182551 DOI: 10.1371/journal.pone.0108716] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 09/03/2014] [Indexed: 12/02/2022] Open
Abstract
Essential proteins are those that are indispensable to cellular survival and development. Existing methods for essential protein identification generally rely on knock-out experiments and/or the relative density of their interactions (edges) with other proteins in a Protein-Protein Interaction (PPI) network. Here, we present a computational method, called EW, to first rank protein-protein interactions in terms of their Edge Weights, and then identify sub-PPI-networks consisting of only the highly-ranked edges and predict their proteins as essential proteins. We have applied this method to publicly-available PPI data on Saccharomyces cerevisiae (Yeast) and Escherichia coli (E. coli) for essential protein identification, and demonstrated that EW achieves better performance than the state-of-the-art methods in terms of the precision-recall and Jackknife measures. The highly-ranked protein-protein interactions by our prediction tend to be biologically significant in both the Yeast and E. coli PPI networks. Further analyses on systematically perturbed Yeast and E. coli PPI networks through randomly deleting edges demonstrate that the proposed method is robust and the top-ranked edges tend to be more associated with known essential proteins than the lowly-ranked edges.
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Affiliation(s)
- Yan Wang
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
- Department of Information and Communication Technology, University of Trento, Povo, Italy
- Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA, United States of America
| | - Huiyan Sun
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
| | - Wei Du
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
| | - Enrico Blanzieri
- Department of Information and Communication Technology, University of Trento, Povo, Italy
- * E-mail: (YCL); (EB)
| | - Gabriella Viero
- Institute of Biophysics, National Research Council, University of Trento, Povo, Italy
| | - Ying Xu
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
- Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA, United States of America
| | - Yanchun Liang
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
- * E-mail: (YCL); (EB)
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19
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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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20
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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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21
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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: 558] [Impact Index Per Article: 50.7] [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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22
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Occhipinti L, Chang Y, Altvater M, Menet AM, Kemmler S, Panse VG. Non-FG mediated transport of the large pre-ribosomal subunit through the nuclear pore complex by the mRNA export factor Gle2. Nucleic Acids Res 2013; 41:8266-79. [PMID: 23907389 PMCID: PMC3783196 DOI: 10.1093/nar/gkt675] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Multiple export receptors passage bound pre-ribosomes through nuclear pore complexes (NPCs) by transiently interacting with the Phe-Gly (FG) meshwork of their transport channels. Here, we reveal how the non-FG interacting yeast mRNA export factor Gly-Leu-FG lethal 2 (Gle2) functions in the export of the large pre-ribosomal subunit (pre-60S). Structure-guided studies uncovered conserved platforms used by Gle2 to export pre-60S: an uncharacterized basic patch required to bind pre-60S, and a second surface that makes non-FG contacts with the nucleoporin Nup116. A basic patch mutant of Gle2 is able to function in mRNA export, but not pre-60S export. Thus, Gle2 provides a distinct interaction platform to transport pre-60S to the cytoplasm. Notably, Gle2’s interaction platforms become crucial for pre-60S export when FG-interacting receptors are either not recruited to pre-60S or are impaired. We propose that large complex cargos rely on non-FG as well as FG-interactions for their efficient translocation through the nuclear pore complex channel.
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Affiliation(s)
- Laura Occhipinti
- Department of Biology (D-BIOL), Institute of Biochemistry (IBC), ETH Zurich, Schafmattstrasse 18, CH-8093 Zurich, Switzerland and MLS Program, Life Sciences Zurich Graduate School, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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23
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Gamalinda M, Jakovljevic J, Babiano R, Talkish J, de la Cruz J, Woolford JL. Yeast polypeptide exit tunnel ribosomal proteins L17, L35 and L37 are necessary to recruit late-assembling factors required for 27SB pre-rRNA processing. Nucleic Acids Res 2012; 41:1965-83. [PMID: 23268442 PMCID: PMC3561946 DOI: 10.1093/nar/gks1272] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Ribosome synthesis involves the coordinated folding and processing of pre-rRNAs with assembly of ribosomal proteins. In eukaryotes, these events are facilitated by trans-acting factors that propel ribosome maturation from the nucleolus to the cytoplasm. However, there is a gap in understanding how ribosomal proteins configure pre-ribosomes in vivo to enable processing to occur. Here, we have examined the role of adjacent yeast r-proteins L17, L35 and L37 in folding and processing of pre-rRNAs, and binding of other proteins within assembling ribosomes. These three essential ribosomal proteins, which surround the polypeptide exit tunnel, are required for 60S subunit formation as a consequence of their role in removal of the ITS2 spacer from 27SB pre-rRNA. L17-, L35- and L37-depleted cells exhibit turnover of aberrant pre-60S assembly intermediates. Although the structure of ITS2 does not appear to be grossly affected in their absence, these three ribosomal proteins are necessary for efficient recruitment of factors required for 27SB pre-rRNA processing, namely, Nsa2 and Nog2, which associate with pre-60S ribosomal particles containing 27SB pre-rRNAs. Altogether, these data support that L17, L35 and L37 are specifically required for a recruiting step immediately preceding removal of ITS2.
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Affiliation(s)
- Michael Gamalinda
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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24
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Shahni R, Czajka A, Mankoo BS, Guvenel AK, King AJ, Malik AN. Nop-7-associated 2 (NSA2), a candidate gene for diabetic nephropathy, is involved in the TGFβ1 pathway. Int J Biochem Cell Biol 2012; 45:626-35. [PMID: 23220173 DOI: 10.1016/j.biocel.2012.11.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 10/28/2012] [Accepted: 11/28/2012] [Indexed: 01/29/2023]
Abstract
We recently showed that Nop-7-associated 2 (NSA2) originally described in yeast as a nuclear protein involved in ribosomal biogenesis, is a hyperglycemia induced gene involved in diabetic nephropathy [Shahni et al., Elevated levels of renal and circulating Nop-7-associated 2 (NSA2) in rat and mouse models of diabetes, in mesangial cells in vitro and in patients with diabetic nephropathy. Diabetologia 2012;55(March(3)):825-34]. However the function of NSA2 in the cell remains unknown. In the current paper we investigate the possible mechanisms for the involvement of NSA2 in diabetic nephropathy by testing the hypothesis that NSA2 expression is linked to the TGFβ1 pathway. Both TGFβ1 and NSA2 mRNAs were significantly up-regulated in cultured renal mesangial cells in response to high glucose, in mouse kidneys during hyperglycemia, and in developing kidneys of mouse embryos during mesenchymal to epithelial transition. Surprisingly, the previously described nuclear NSA2 protein was predominantly located in the cytosol of cultured renal cells. Exogenous TGFβ1 could elevate NSA2 mRNA/protein levels in cultured mesangial cells and could also affect the cellular localization of NSA2, causing the predominantly cytosolic NSA2 protein to rapidly translocate to the nucleus. Increased NSA2 nuclear staining was seen in diabetic mouse kidneys compared to control kidneys. Knock-down of NSA2 expression using RNA interference resulted in significantly decreased TGFβ1 mRNA/protein, almost abolished TGFβ1 activity, and resulted in significantly reduced mRNA levels of the TGFβ1 downstream gene fibronectin. Our data suggest that NSA2 is acting upstream of the TGFβ1 pathway and that NSA2 is needed for TGFβ1 expression and transcriptional activity. In summary, NSA2, which increases in diabetic nephropathy, may be involved in the actions of TGFβ1 and contribute to the development of diabetic nephropathy.
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Affiliation(s)
- Rojeen Shahni
- Diabetes Research Group, Division of Diabetes and Nutritional Sciences, School of Medicine, King's College London, Hodgkin Building, London Bridge, London SE1 1UL, United Kingdom
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25
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Bradatsch B, Leidig C, Granneman S, Gnädig M, Tollervey D, Böttcher B, Beckmann R, Hurt E. Structure of the pre-60S ribosomal subunit with nuclear export factor Arx1 bound at the exit tunnel. Nat Struct Mol Biol 2012; 19:1234-41. [PMID: 23142978 PMCID: PMC3678077 DOI: 10.1038/nsmb.2438] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 10/09/2012] [Indexed: 12/24/2022]
Abstract
Preribosomal particles evolve in the nucleus through transient interaction with biogenesis factors before export to the cytoplasm. Here, we report the architecture of the late pre-60S particle, purified from Saccharomyces cerevisiae, through Arx1, a nuclear export factor with structural homology to methionine aminopeptidases, or its binding partner Alb1. Cryo-EM reconstruction of the Arx1 particle at 11.9-Å resolution reveals regions of extra density on the pre-60S particle attributed to associated biogenesis factors, confirming the immature state of the nascent subunit. One of these densities could be unambiguously assigned to Arx1. Immunoelectron microscopy and UV cross-linking localize Arx1 close to the ribosomal exit tunnel, in direct contact with ES27, a highly dynamic eukaryotic rRNA expansion segment. The binding of Arx1 at the exit tunnel may position this export factor to prevent premature recruitment of ribosome-associated factors active during translation.
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26
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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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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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28
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Saccharomyces cerevisiae ribosomal protein L26 is not essential for ribosome assembly and function. Mol Cell Biol 2012; 32:3228-41. [PMID: 22688513 DOI: 10.1128/mcb.00539-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Ribosomal proteins play important roles in ribosome biogenesis and function. Here, we study the evolutionarily conserved L26 in Saccharomyces cerevisiae, which assembles into pre-60S ribosomal particles in the nucle(ol)us. Yeast L26 is one of the many ribosomal proteins encoded by two functional genes. We have disrupted both genes; surprisingly, the growth of the resulting rpl26 null mutant is apparently identical to that of the isogenic wild-type strain. The absence of L26 minimally alters 60S ribosomal subunit biogenesis. Polysome analysis revealed the appearance of half-mers. Analysis of pre-rRNA processing indicated that L26 is mainly required to optimize 27S pre-rRNA maturation, without which the release of pre-60S particles from the nucle(ol)us is partially impaired. Ribosomes lacking L26 exhibit differential reactivity to dimethylsulfate in domain I of 25S/5.8S rRNAs but apparently are able to support translation in vivo with wild-type accuracy. The bacterial homologue of yeast L26, L24, is a primary rRNA binding protein required for 50S ribosomal subunit assembly in vitro and in vivo. Our results underscore potential differences between prokaryotic and eukaryotic ribosome assembly. We discuss the reasons why yeast L26 plays such an apparently nonessential role in the cell.
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29
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Shahni R, Gnudi L, King A, Jones P, Malik AN. Elevated levels of renal and circulating Nop-7-associated 2 (NSA2) in rat and mouse models of diabetes, in mesangial cells in vitro and in patients with diabetic nephropathy. Diabetologia 2012; 55:825-34. [PMID: 22095236 DOI: 10.1007/s00125-011-2373-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 10/18/2011] [Indexed: 12/11/2022]
Abstract
AIMS/HYPOTHESIS We previously found that Nop-7-associated 2 (NSA2), which is involved in ribosomal biogenesis in yeast and is a putative cell cycle regulator in mammalian cells, is elevated in the kidney of Goto-Kakizaki (GK) rat, a spontaneous model of type 2 diabetes. Here we tested the hypothesis that elevated NSA2 is involved in diabetic nephropathy (DN). METHODS We examined Nsa2/NSA2 expression and NSA2 production in two rodent models of diabetes, in cultured renal glomerular cells, and in diabetic patients with and without nephropathy. Patients with nephropathy who had a history of albuminuria were further divided as responders (DN-NA; DN patients normoalbuminuric at the time of this study with a history of albuminuria) and non-responders (DN-A; diabetic nephropathy patients with albuminuria) to current treatment for albuminuria. RESULTS Renal Nsa2/NSA2 mRNA increased in tandem with hyperglycaemia in GK rats, in a streptozotocin-induced mouse model of diabetes, and in human mesangial cells (HMCs) grown in high glucose (p < 0.05). In the mouse model of diabetes, hyperglycaemia resulted in increased Nsa2 expression and NSA2 levels in tubular and glomerular cells and in circulating cells; this increase was normalised by diabetes treatment. Circulating NSA2 mRNA levels were elevated in patients with DN independently of body weight (BMI), glycaemic (HbA(1c)) and haemodynamic (blood pressure) control, and showed an inverse correlation with renal function (GFR, p < 0.05). NSA2 levels were the only variable that showed a significant difference between patients with albuminuria (DN-A) compared with non-albuminuric patients (DN-NA) and diabetic controls (p < 0.05), this increase being independent of all other variables, including GFR. CONCLUSION We show for the first time that renal and circulating NSA2/NSA2 levels are increased in hyperglycaemia in experimental models of diabetes, and that circulating NSA2 is elevated in DN patients with albuminuria. Further studies will be required to assess whether NSA2 plays a role in the pathogenesis of DN.
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MESH Headings
- Adult
- Aged
- Albuminuria/etiology
- Animals
- Cell Cycle Proteins/blood
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/metabolism
- Cells, Cultured
- Diabetes Mellitus, Type 1/complications
- Diabetes Mellitus, Type 1/metabolism
- Diabetes Mellitus, Type 1/pathology
- Diabetes Mellitus, Type 1/urine
- Diabetes Mellitus, Type 2/complications
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/pathology
- Diabetes Mellitus, Type 2/urine
- Diabetic Nephropathies/blood
- Diabetic Nephropathies/metabolism
- Diabetic Nephropathies/pathology
- Diabetic Nephropathies/physiopathology
- Disease Models, Animal
- Female
- Gene Expression Regulation
- Humans
- Kidney/cytology
- Kidney/metabolism
- Kidney/pathology
- Kidney/physiopathology
- Male
- Mesangial Cells/metabolism
- Mice
- Mice, Inbred C57BL
- Middle Aged
- Nuclear Proteins/blood
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- RNA, Messenger/metabolism
- RNA-Binding Proteins
- Rats
- Rats, Inbred Strains
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Affiliation(s)
- R Shahni
- Diabetes Research Group, Division of Diabetes and Nutritional Sciences, School of Medicine, Kings College London, Hodgkin Building, London Bridge, London SE1 1UL, UK
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30
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Assembly of Saccharomyces cerevisiae 60S ribosomal subunits: role of factors required for 27S pre-rRNA processing. EMBO J 2011; 30:4020-32. [PMID: 21926967 DOI: 10.1038/emboj.2011.338] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 08/25/2011] [Indexed: 11/08/2022] Open
Abstract
The precise functions of most of the ∼200 assembly factors and 79 ribosomal proteins required to construct yeast ribosomes in vivo remain largely unexplored. To better understand the roles of these proteins and the mechanisms driving ribosome biogenesis, we examined in detail one step in 60S ribosomal subunit assembly-processing of 27SA(3) pre-rRNA. Six of seven assembly factors required for this step (A(3) factors) are mutually interdependent for association with preribosomes. These A(3) factors are required to recruit Rrp17, one of three exonucleases required for this processing step. In the absence of A(3) factors, four ribosomal proteins adjacent to each other, rpL17, rpL26, rpL35, and rpL37, fail to assemble, and preribosomes are turned over by Rat1. We conclude that formation of a neighbourhood in preribosomes containing the A(3) factors establishes and maintains stability of functional preribosomes containing 27S pre-rRNAs. In the absence of these assembly factors, at least one exonuclease can switch from processing to turnover of pre-rRNA.
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31
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Zhang H, Ma X, Shi T, Song Q, Zhao H, Ma D. NSA2, a novel nucleolus protein regulates cell proliferation and cell cycle. Biochem Biophys Res Commun 2009; 391:651-8. [PMID: 19932687 DOI: 10.1016/j.bbrc.2009.11.114] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 11/18/2009] [Indexed: 10/20/2022]
Abstract
NSA2 (Nop seven-associated 2) was previously identified in a high throughput screen of novel human genes associated with cell proliferation, and the NSA2 protein is evolutionarily conserved across different species. In this study, we revealed that NSA2 is broadly expressed in human tissues and cultured cell lines, and located in the nucleolus of the cell. Both of the putative nuclear localization signals (NLSs) of NSA2, also overlapped with nucleolar localization signals (NoLSs), are capable of directing nucleolar accumulation. Moreover, over-expression of the NSA2 protein promoted cell growth in different cell lines and regulated the G1/S transition in the cell cycle. SiRNA silencing of the NSA2 transcript attenuated the cell growth and dramatically blocked the cell cycle in G1/S transition. Our results demonstrated that NSA2 is a nucleolar protein involved in cell proliferation and cell cycle regulation.
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Affiliation(s)
- Heyu Zhang
- Department of Immunology, School of Basic Medical Sciences, Peking University, No 38 Xueyuan Road, Beijing 100191, PR China
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32
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Rodríguez-Mateos M, Abia D, García-Gómez JJ, Morreale A, de la Cruz J, Santos C, Remacha M, Ballesta JPG. The amino terminal domain from Mrt4 protein can functionally replace the RNA binding domain of the ribosomal P0 protein. Nucleic Acids Res 2009; 37:3514-21. [PMID: 19346338 PMCID: PMC2699499 DOI: 10.1093/nar/gkp209] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 03/06/2009] [Accepted: 03/14/2009] [Indexed: 11/20/2022] Open
Abstract
In Saccharomyces cerevisiae, the Mrt4 protein is a component of the ribosome assembly machinery that shares notable sequence homology to the P0 ribosomal stalk protein. Here, we show that these proteins can not bind simultaneously to ribosomes and moreover, a chimera containing the first 137 amino acids of Mrt4 and the last 190 amino acids from P0 can partially complement the absence of the ribosomal protein in a conditional P0 null mutant. This chimera is associated with ribosomes isolated from this strain when grown under restrictive conditions, although its binding is weaker than that of P0. These ribosomes contain less P1 and P2 proteins, the other ribosomal stalk components. Similarly, the interaction of the L12 protein, a stalk base component, is affected by the presence of the chimera. These results indicate that Mrt4 and P0 bind to the same site in the 25S rRNA. Indeed, molecular dynamics simulations using modelled Mrt4 and P0 complexes provide further evidence that both proteins bind similarly to rRNA, although their interaction with L12 displays notable differences. Together, these data support the participation of the Mrt4 protein in the assembly of the P0 protein into the ribosome and probably, that also of the L12 protein.
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Affiliation(s)
- María Rodríguez-Mateos
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
| | - David Abia
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
| | - Juan J. García-Gómez
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
| | - Antonio Morreale
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
| | - Jesús de la Cruz
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
| | - Cruz Santos
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
| | - Miguel Remacha
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
| | - Juan P. G. Ballesta
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049 and Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, Sevilla
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33
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Wang JL, Zhang YP, Gu YY, Wang JX, Zhao XF. Function of a TGF-beta inducible nuclear protein in the silk gland in Bombyx mori. INSECT MOLECULAR BIOLOGY 2009; 18:243-251. [PMID: 19220509 DOI: 10.1111/j.1365-2583.2008.00861.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A TGF-beta inducible nuclear protein 1 (BmTINP1) was cloned from silkworm, Bombyx mori. Polyclonal antibodies against BmTINP1 were produced and subsequently used in immunoblotting and immunohistochemistry analyses. The immunoblotting analyses demonstrated that BmTINP1 was specifically expressed in the anterior silk gland (ASG) and the middle silk gland (MSG) but not in the posterior silk gland (PSG). There were two bands that suggested the existence of an isoform of BmTINP1. The expression profiles of BmTINP1 in ASGs and MSGs were similar, and they manifested a high level of expression throughout the period during which silk gland grew exponentially. Immunohistochemistry results revealed that BmTINP1 was translocated from the nucleus into the cytoplasm when larvae developed from the 4th-HCS into the 5th instar. 20-hydroxyecdysone (20E) promotes the translocation, while the methoprene [a juvenile hormone (JH) analog] restrains the process. Our findings indicate that BmTINP1 is involved in silk produce along with the rapid growth of ASGs and MSGs during the last instar larvae, and the process could be regulated by hormones via control of BmTINP1 translocation from the nucleus to the cytoplasm.
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Affiliation(s)
- J-L Wang
- Shandong University, Jinan, Shandong, China
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34
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Lebreton A, Rousselle JC, Lenormand P, Namane A, Jacquier A, Fromont-Racine M, Saveanu C. 60S ribosomal subunit assembly dynamics defined by semi-quantitative mass spectrometry of purified complexes. Nucleic Acids Res 2008; 36:4988-99. [PMID: 18658244 PMCID: PMC2528192 DOI: 10.1093/nar/gkn469] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
During the highly conserved process of eukaryotic ribosome formation, RNA follows a maturation path with well-defined, successive intermediates that dynamically associate with many pre-ribosomal proteins. A comprehensive description of the assembly process is still lacking. To obtain data on the timing and order of association of the different pre-ribosomal factors, a strategy consists in the use of pre-ribsomal particles isolated from mutants that block ribosome formation at different steps. Immunoblots, inherently limited to only a few factors, have been applied to evaluate the accumulation or decrease of pre-ribosomal intermediates under mutant conditions. For a global protein-level description of different 60S ribosomal subunit maturation intermediates in yeast, we have adapted a method of in vivo isotopic labelling and mass spectrometry to study pre-60S complexes isolated from strains in which rRNA processing was affected by individual depletion of five factors: Ebp2, Nog1, Nsa2, Nog2 or Pop3. We obtained quantitative data for 45 distinct pre-60S proteins and detected coordinated changes for over 30 pre-60S factors in the analysed mutants. These results led to the characterisation of the composition of early, intermediate and late pre-ribosomal complexes, specific for crucial maturation steps during 60S assembly in eukaryotes.
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Affiliation(s)
- Alice Lebreton
- Institut Pasteur, Unité de Génétique des Interactions Macromoléculaires, CNRS-URA2171, Paris, France
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35
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Lapik YR, Misra JM, Lau LF, Pestov DG. Restricting conformational flexibility of the switch II region creates a dominant-inhibitory phenotype in Obg GTPase Nog1. Mol Cell Biol 2007; 27:7735-44. [PMID: 17785438 PMCID: PMC2169037 DOI: 10.1128/mcb.01161-07] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nog1 is a conserved eukaryotic GTPase of the Obg family involved in the biogenesis of 60S ribosomal subunits. Here we report the unique dominant-inhibitory properties of a point mutation in the switch II region of mouse Nog1; this mutation is predicted to restrict conformational mobility of the GTP-binding domain. We show that although the mutation does not significantly affect GTP binding, ectopic expression of the mutant in mouse cells disrupts productive assembly of pre-60S subunits and arrests cell proliferation. The mutant impairs processing of multiple pre-rRNA intermediates, resulting in the degradation of the newly synthesized 5.8S/28S rRNA precursors. Sedimentation analysis of nucleolar preribosomes indicates that defective Nog1 function inhibits the conversion of 32S pre-rRNA-containing complexes to a smaller form, resulting in a drastic accumulation of enlarged pre-60S particles in the nucleolus. These results suggest that conformational changes in the switch II element of Nog1 have a critical importance for the dissociation of preribosome-bound factors during intranucleolar maturation and thereby strongly influence the overall efficiency of the assembly process.
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Affiliation(s)
- Yevgeniya R Lapik
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago College of Medicine, Chicago, Illinois 60607, USA
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36
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Demoinet E, Jacquier A, Lutfalla G, Fromont-Racine M. The Hsp40 chaperone Jjj1 is required for the nucleo-cytoplasmic recycling of preribosomal factors in Saccharomyces cerevisiae. RNA (NEW YORK, N.Y.) 2007; 13:1570-81. [PMID: 17652132 PMCID: PMC1950757 DOI: 10.1261/rna.585007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Accepted: 06/12/2007] [Indexed: 05/03/2023]
Abstract
Ribosome biogenesis is a major conserved cellular pathway that requires both ribosomal proteins and many preribosomal factors. Most of the pre-60S factors are recycled into the nucleus; some of them shuttle between the nucleus and the cytoplasm while a few others, like Rei1, are strictly cytoplasmic and are mostly involved in the dissociation/recycling of the pre-60S shuttling factors. Here, we investigated the role of the Jjj1 Hsp40 chaperone in ribosome biogenesis. The absence of Jjj1 leads to a cold sensitive phenotype, a defect in the relative amount of the large ribosomal subunit with the appearance of halfmers, and to cytoplasmic accumulation of shuttling factors such as Arx1 and Alb1, which stay bound to the pre-60S particles. Jjj1 is, thus, a novel pre-60S factor involved in the last cytoplasmic steps of the large ribosomal subunit biogenesis. We report the biochemical association of Jjj1 and Rei1 to similar pre-60S complexes, their two-hybrid interactions, and their functional links. Altogether, these results indicate that Rei1 and Jjj1 share many common features. However, while the functions of Jjj1 and Rei1 partially overlap, we could distinguish specific role of the two proteins in Arx1/Alb1 and Tif6 recycling. We propose that Jjj1 is preferentially required for the release of Arx1 and Alb1 shuttling factors from the cytoplasmic pre-60S particles while Rei1 is preferentially involved in their recycling.
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Affiliation(s)
- Emilie Demoinet
- Défenses Antivirales et Antitumorales, CNRS-UMR5235, Université Montpellier II, France
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37
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Lam YW, Lamond AI, Mann M, Andersen JS. Analysis of nucleolar protein dynamics reveals the nuclear degradation of ribosomal proteins. Curr Biol 2007; 17:749-60. [PMID: 17446074 PMCID: PMC1885954 DOI: 10.1016/j.cub.2007.03.064] [Citation(s) in RCA: 279] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Revised: 02/28/2007] [Accepted: 03/14/2007] [Indexed: 11/21/2022]
Abstract
Background The nucleolus is a subnuclear organelle in which rRNAs are transcribed, processed, and assembled with ribosomal proteins into ribosome subunits. Mass spectrometry combined with pulsed incorporation of stable isotopes of arginine and lysine was used to perform a quantitative and unbiased global analysis of the rates at which newly synthesized, endogenous proteins appear within mammalian nucleoli. Results Newly synthesized ribosomal proteins accumulated in nucleoli more quickly than other nucleolar components. Studies involving time-lapse fluorescence microscopy of stable HeLa cell lines expressing fluorescent-protein-tagged nucleolar factors also showed that ribosomal proteins accumulate more quickly than other components. Photobleaching and mass-spectrometry experiments suggest that only a subset of newly synthesized ribosomal proteins are assembled into ribosomes and exported to the cytoplasm. Inhibition of the proteasome caused an accumulation of ribosomal proteins in the nucleus but not in the cytoplasm. Inhibition of rRNA transcription prior to proteasomal inhibition further increased the accumulation of ribosomal proteins in the nucleoplasm. Conclusions Ribosomal proteins are expressed at high levels beyond that required for the typical rate of ribosome-subunit production and accumulate in the nucleolus more quickly than all other nucleolar components. This is balanced by continual degradation of unassembled ribosomal proteins in the nucleoplasm, thereby providing a mechanism for mammalian cells to ensure that ribosomal protein levels are never rate limiting for the efficient assembly of ribosome subunits. The dual time-lapse strategy used in this study, combining proteomics and imaging, provides a powerful approach for the quantitative analysis of the flux of newly synthesized proteins through a cell organelle.
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Affiliation(s)
- Yun Wah Lam
- Division of Gene Regulation and Expression, Wellcome Trust Biocentre, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom
| | - Angus I. Lamond
- Division of Gene Regulation and Expression, Wellcome Trust Biocentre, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom
- Corresponding author
| | - Matthias Mann
- Proteomics and Signal Transduction, Max Planck Institute for Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany
| | - Jens S. Andersen
- Center for Experimental BioInformatics, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark
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38
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Fuentes JL, Datta K, Sullivan SM, Walker A, Maddock JR. In vivo functional characterization of the Saccharomyces cerevisiae 60S biogenesis GTPase Nog1. Mol Genet Genomics 2007; 278:105-23. [PMID: 17443350 DOI: 10.1007/s00438-007-0233-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Accepted: 03/16/2007] [Indexed: 01/08/2023]
Abstract
The Saccharomyces cerevisiae Nog1 GTPase is critical for assembly of the large ribosomal subunit. Mutations in conserved residues in the GTP-binding pocket cause defects in cell growth and 60S ribosome assembly but mutant proteins retain their ability to associate with the pre-60S. Association of Nog1 with the pre-60S is independent of guanine nucleotide added to cell extracts. Thus, it appears that nucleotide occupancy does not substantially affect Nog1 association with pre-60S particles. Somewhat surprisingly, neither of the conserved threonines in the G2 motif of the GTPase domain is essential for Nog1 function. Neither the steady-state rRNA levels nor the protein composition (as determined by isobaric labeling and identification by mass spectrometry of peptides) of the pre-60S particles in the nog1P176V mutant are grossly perturbed, although levels of four proteins (Nog1, Nop2, Nop15, and Tif6) are modestly reduced in pre-60S particles isolated from the mutant. Deletion analysis revealed that the C-terminal 168 amino acids are not required for function; however, the N-terminal 126 amino acids are required. Optimal association with pre-60S particles requires sequences between amino acids 347-456. Several conserved charge-to-alanine substitutions outside the GTPase domain display modest growth phenotypes indicating that these residues are not critical for function.
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Affiliation(s)
- Jennifer L Fuentes
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48109, USA
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39
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Saveanu C, Rousselle JC, Lenormand P, Namane A, Jacquier A, Fromont-Racine M. The p21-activated protein kinase inhibitor Skb15 and its budding yeast homologue are 60S ribosome assembly factors. Mol Cell Biol 2007; 27:2897-909. [PMID: 17308036 PMCID: PMC1899936 DOI: 10.1128/mcb.00064-07] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ribosome biogenesis is driven by a large number of preribosomal factors that associate with and dissociate from the preribosomal particles along the maturation pathway. We have previously shown that budding yeast Mak11, whose homologues in other eukaryotes were described as modulating a p21-activated protein kinase function, accumulates in Rlp24-associated pre-60S complexes when their maturation is impeded in Saccharomyces cerevisiae. The functional inactivation of WD40 repeat protein Mak11 interfered with the 60S rRNA maturation, led to a cell cycle delay in G(1), and blocked green fluorescent protein-tagged Rpl25 in the nucleoli of yeast cells, indicating an early role of Mak11 in ribosome assembly. Surprisingly, Mak11 inactivation also led to a dramatic destabilization of Rlp24. The suppression of the thermosensitive phenotype of a mak11 mutant by RLP24 overexpression and a direct in vitro interaction between Rlp24 and Mak11 suggest that Mak11 acts as an Rlp24 cofactor during early steps of 60S ribosomal subunit assembly. Moreover, we found that Skb15, the Mak11 homologue in Schizosaccharomyces pombe, also associated with preribosomes and affected 60S biogenesis in fission yeast. It is thus likely that the previously observed phenotypes for MAK11 homologues in other eukaryotes are secondary to the main function of these proteins in ribosome formation.
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Affiliation(s)
- Cosmin Saveanu
- Génétique des Interactions Macromoléculaires, Institut Pasteur, 25 rue du docteur Roux, 75724 Paris Cedex 15, France
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