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Decle-Carrasco S, Rodríguez-Piña AL, Rodríguez-Zapata LC, Castano E. Current research on viral proteins that interact with fibrillarin. Mol Biol Rep 2023; 50:4631-4643. [PMID: 36928641 PMCID: PMC10018631 DOI: 10.1007/s11033-023-08343-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 02/15/2023] [Indexed: 03/18/2023]
Abstract
The nucleolus is a multifunctional nuclear domain primarily dedicated to ribosome biogenesis. Certain viruses developed strategies to manipulate host nucleolar proteins to facilitate their replication by modulating ribosomal RNA (rRNA) processing. This association interferes with nucleolar functions resulting in overactivation or arrest of ribosome biogenesis, induction or inhibition of apoptosis, and affecting stress response. The nucleolar protein fibrillarin (FBL) is an important target of some plant and animal viruses. FBL is an essential and highly conserved S-adenosyl methionine (SAM) dependent methyltransferase, capable of rRNA degradation by its intrinsically disordered region (IDR), the glycine/arginine-rich (GAR) domain. It forms a ribonucleoprotein complex that directs 2'-O-methylations in more than 100 sites of pre-rRNAs. It is involved in multiple cellular processes, including initiation of transcription, oncogenesis, and apoptosis, among others. The interaction with animal viruses, including human viruses, triggered its redistribution to the nucleoplasm and cytoplasm, interfering with its role in pre-rRNA processing. Viral-encoded proteins with IDRs as nucleocapsids, matrix, Tat protein, and even a viral snoRNA, can associate with FBL, forcing the nucleolar protein to undergo atypical functions. Here we review the molecular mechanisms employed by animal and human viruses to usurp FBL functions and the effect on cellular processes, particularly in ribosome biogenesis.
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Affiliation(s)
- Stefano Decle-Carrasco
- Unidad de Bioquímica y Biología Molecular de Plantas. Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida, Yucatán, México
| | - Alma Laura Rodríguez-Piña
- Unidad de Bioquímica y Biología Molecular de Plantas. Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida, Yucatán, México
| | - Luis Carlos Rodríguez-Zapata
- Unidad de Biotecnología. Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida, Yucatán, México
| | - Enrique Castano
- Unidad de Bioquímica y Biología Molecular de Plantas. Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida, Yucatán, México.
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Lemus-Diaz N, Ferreira RR, Bohnsack KE, Gruber J, Bohnsack MT. The human box C/D snoRNA U3 is a miRNA source and miR-U3 regulates expression of sortin nexin 27. Nucleic Acids Res 2020; 48:8074-8089. [PMID: 32609813 PMCID: PMC7430653 DOI: 10.1093/nar/gkaa549] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 05/29/2020] [Accepted: 06/22/2020] [Indexed: 02/06/2023] Open
Abstract
MicroRNAs (miRNAs) are important regulators of eukaryotic gene expression and their dysfunction is often associated with cancer. Alongside the canonical miRNA biogenesis pathway involving stepwise processing and export of pri- and pre-miRNA transcripts by the microprocessor complex, Exportin 5 and Dicer, several alternative mechanisms of miRNA production have been described. Here, we reveal that the atypical box C/D snoRNA U3, which functions as a scaffold during early ribosome assembly, is a miRNA source. We show that a unique stem-loop structure in the 5' domain of U3 is processed to form short RNA fragments that associate with Argonaute. miR-U3 production is independent of Drosha, and an increased amount of U3 in the cytoplasm in the absence of Dicer suggests that a portion of the full length snoRNA is exported to the cytoplasm where it is efficiently processed into miRNAs. Using reporter assays, we demonstrate that miR-U3 can act as a low proficiency miRNA in vivo and our data support the 3' UTR of the sortin nexin SNX27 mRNA as an endogenous U3-derived miRNA target. We further reveal that perturbation of U3 snoRNP assembly induces miR-U3 production, highlighting potential cross-regulation of target mRNA expression and ribosome production.
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Affiliation(s)
- Nicolas Lemus-Diaz
- Department of Molecular Biology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
- Junior Research Group Medical RNA Biology, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany
| | - Rafael Rinaldi Ferreira
- Junior Research Group Medical RNA Biology, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany
| | - Katherine E Bohnsack
- Department of Molecular Biology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Jens Gruber
- Junior Research Group Medical RNA Biology, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany
| | - Markus T Bohnsack
- Department of Molecular Biology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
- Göttingen Center for Molecular Biosciences, Georg-August University, Göttingen, Justus-von-Liebig-Weg 11, 37077 Germany
- Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC)
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3
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Impaired chondrocyte U3 snoRNA expression in osteoarthritis impacts the chondrocyte protein translation apparatus. Sci Rep 2020; 10:13426. [PMID: 32778764 PMCID: PMC7417995 DOI: 10.1038/s41598-020-70453-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 07/23/2020] [Indexed: 12/18/2022] Open
Abstract
Although pathways controlling ribosome activity have been described to regulate chondrocyte homeostasis in osteoarthritis, ribosome biogenesis in osteoarthritis is unexplored. We hypothesized that U3 snoRNA, a non-coding RNA involved in ribosomal RNA maturation, is critical for chondrocyte protein translation capacity in osteoarthritis. U3 snoRNA was one of a number of snoRNAs with decreased expression in osteoarthritic cartilage and osteoarthritic chondrocytes. OA synovial fluid impacted U3 snoRNA expression by affecting U3 snoRNA gene promoter activity, while BMP7 was able to increase its expression. Altering U3 snoRNA expression resulted in changes in chondrocyte phenotype. Interference with U3 snoRNA expression led to reduction of rRNA levels and translational capacity, whilst induced expression of U3 snoRNA was accompanied by increased 18S and 28S rRNA levels and elevated protein translation. Whole proteome analysis revealed a global impact of reduced U3 snoRNA expression on protein translational processes and inflammatory pathways. For the first time we demonstrate implications of a snoRNA in osteoarthritis chondrocyte biology and investigated its role in the chondrocyte differentiation status, rRNA levels and protein translational capacity.
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Guillen-Chable F, Rodríguez Corona U, Pereira-Santana A, Bayona A, Rodríguez-Zapata LC, Aquino C, Šebestová L, Vitale N, Hozak P, Castano E. Fibrillarin Ribonuclease Activity is Dependent on the GAR Domain and Modulated by Phospholipids. Cells 2020; 9:cells9051143. [PMID: 32384686 PMCID: PMC7290794 DOI: 10.3390/cells9051143] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 04/24/2020] [Accepted: 04/29/2020] [Indexed: 12/16/2022] Open
Abstract
Fibrillarin is a highly conserved nucleolar methyltransferase responsible for ribosomal RNA methylation across evolution from Archaea to humans. It has been reported that fibrillarin is involved in the methylation of histone H2A in nucleoli and other processes, including viral progression, cellular stress, nuclear shape, and cell cycle progression. We show that fibrillarin has an additional activity as a ribonuclease. The activity is affected by phosphoinositides and phosphatidic acid and insensitive to ribonuclease inhibitors. Furthermore, the presence of phosphatidic acid releases the fibrillarin-U3 snoRNA complex. We show that the ribonuclease activity localizes to the GAR (glycine/arginine-rich) domain conserved in a small group of RNA interacting proteins. The introduction of the GAR domain occurred in evolution in the transition from archaea to eukaryotic cells. The interaction of this domain with phospholipids may allow a phase separation of this protein in nucleoli.
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Affiliation(s)
- Francisco Guillen-Chable
- Biochemistry and Molecular Plant Biology Department, Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida C.P. 97200, Yucatán, Mexico; (F.G.-C.); (U.R.C.); (A.B.); (C.A.)
| | - Ulises Rodríguez Corona
- Biochemistry and Molecular Plant Biology Department, Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida C.P. 97200, Yucatán, Mexico; (F.G.-C.); (U.R.C.); (A.B.); (C.A.)
| | - Alejandro Pereira-Santana
- Industrial Biotechnology Department, Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, A.C., Camino Arenero 1227, el Bajio, Zapopan C.P. 45019, Jalisco, Mexico;
- Dirección de Cátedras, Consejo Nacional de Ciencia y Tecnología, Av. Insurgentes Sur 1582, Alcaldia Benito Juarez C.P. 03940, Ciudad de Mexico, Mexico
| | - Andrea Bayona
- Biochemistry and Molecular Plant Biology Department, Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida C.P. 97200, Yucatán, Mexico; (F.G.-C.); (U.R.C.); (A.B.); (C.A.)
| | - Luis Carlos Rodríguez-Zapata
- Biotechnology Department, Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida C.P. 97200, Yucatan, Mexico;
| | - Cecilia Aquino
- Biochemistry and Molecular Plant Biology Department, Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida C.P. 97200, Yucatán, Mexico; (F.G.-C.); (U.R.C.); (A.B.); (C.A.)
| | - Lenka Šebestová
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the CAS, v.v.i., Videnska 1083, 142 20 Prague, Czech Republic; (L.Š.); (P.H.)
- Faculty of Science, Charles University, Albertov 6, 128 00 Prague, Czech Republic
| | - Nicolas Vitale
- Institute of Celullar and Integrative Neuroscience (INCI), UPR-3212 The French National Centre for Scientific Research & University of Strasbourg, 67000 Strasbourg, France;
| | - Pavel Hozak
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the CAS, v.v.i., Videnska 1083, 142 20 Prague, Czech Republic; (L.Š.); (P.H.)
| | - Enrique Castano
- Biochemistry and Molecular Plant Biology Department, Centro de Investigación Científica de Yucatán, A.C. Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida C.P. 97200, Yucatán, Mexico; (F.G.-C.); (U.R.C.); (A.B.); (C.A.)
- Correspondence:
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Liang J, Wen J, Huang Z, Chen XP, Zhang BX, Chu L. Small Nucleolar RNAs: Insight Into Their Function in Cancer. Front Oncol 2019; 9:587. [PMID: 31338327 PMCID: PMC6629867 DOI: 10.3389/fonc.2019.00587] [Citation(s) in RCA: 164] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Accepted: 06/17/2019] [Indexed: 02/04/2023] Open
Abstract
Small nucleolar RNAs (SnoRNAs) are a class of non-coding RNAs divided into two classes: C/D box snoRNAs and H/ACA box snoRNAs. The canonical function of C/D box and H/ACA box snoRNAs are 2'-O-ribose methylation and pseudouridylation of ribosomal RNAs (rRNAs), respectively. Emerging evidence has demonstrated that snoRNAs are involved in various physiological and pathological cellular processes. Mutations and aberrant expression of snoRNAs have been reported in cell transformation, tumorigenesis, and metastasis, indicating that snoRNAs may serve as biomarkers and/or therapeutic targets of cancer. Hence, further study of the functions and underlying mechanism of snoRNAs is valuable. In this review, we summarize the biogenesis and functions of snoRNAs, as well as the association of snoRNAs in different types of cancers and their potential roles in cancer diagnosis and therapy.
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Affiliation(s)
- Junnan Liang
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jingyuan Wen
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhao Huang
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiao-Ping Chen
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Bi-Xiang Zhang
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Liang Chu
- Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Stamm S, Lodmell JS. C/D box snoRNAs in viral infections: RNA viruses use old dogs for new tricks. Noncoding RNA Res 2019; 4:46-53. [PMID: 31193534 PMCID: PMC6533054 DOI: 10.1016/j.ncrna.2019.02.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/27/2019] [Accepted: 02/13/2019] [Indexed: 12/17/2022] Open
Abstract
C/D box snoRNAs (SNORDs) are a highly expressed class of non-coding RNAs. Besides their well-established role in rRNA modification, C/D box snoRNAs form protein complexes devoid of fibrillarin and regulate pre-mRNA splicing and polyadenylation of numerous genes. There is an emerging body of evidence for functional interactions between RNA viruses and C/D box snoRNAs. The infectivity of some RNA viruses depends on enzymatically active fibrillarin, and many RNA viral proteins associate with nucleolin or nucleophosmin, suggesting that viruses benefit from their cytosolic accumulation. These interactions are likely reflected by morphological changes in the nucleolus, often leading to relocalization of nucleolar proteins and ncRNAs to the cytosol that are a characteristic feature of viral infections. Knock-down studies have also shown that RNA viruses need specific C/D box snoRNAs for optimal replication, suggesting that RNA viruses benefit from gene expression programs regulated by SNORDs, or that viruses have evolved “new” uses for these humble ncRNAs to advance their prospects during infection.
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Affiliation(s)
- Stefan Stamm
- University of Kentucky, Molecular and Cellular Biochemistry, 741 South Limestone, Lexington, KY 40536, USA
| | - J Stephen Lodmell
- Division of Biological Sciences and Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, MT, USA
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Sloan KE, Knox AA, Wells GR, Schneider C, Watkins NJ. Interactions and activities of factors involved in the late stages of human 18S rRNA maturation. RNA Biol 2019; 16:196-210. [PMID: 30638116 PMCID: PMC6380343 DOI: 10.1080/15476286.2018.1564467] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Ribosome production is an essential cellular process involving a plethora of trans-acting factors, such as nucleases, methyltransferases, RNA helicases and kinases that catalyse key maturation steps. Precise temporal and spatial regulation of such enzymes is essential to ensure accurate and efficient subunit assembly. Here, we focus on the maturation of the 3ʹ end of the 18S rRNA in human cells. We reveal that human RIO2 is an active kinase that phosphorylates both itself and the rRNA methyltransferase DIM1 in vitro. In contrast to yeast, our data confirm that human DIM1 predominantly acts in the nucleus and we further demonstrate that the 21S pre-rRNA is the main target for DIM1-catalysed methylation. We show that the PIN domain of the endonuclease NOB1 is required for site 3 cleavage, while the zinc ribbon domain is essential for pre-40S recruitment. Furthermore, we also demonstrate that NOB1, PNO1 and DIM1 bind to a region of the pre-rRNA encompassing the 3ʹ end of 18S and the start of ITS1, in vitro. Interestingly, NOB1 is present in the cell at higher levels than other pre-40S factors. We provide evidence that NOB1 is multimeric within the cell and show that NOB1 multimerisation is lost when ribosome biogenesis is blocked. Taken together, our data indicate a dynamic interplay of key factors associated with the 3ʹ end of the 18S rRNA during human pre-40S biogenesis and highlight potential mechanisms by which this process can be regulated.
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Affiliation(s)
- Katherine Elizabeth Sloan
- a Institute for Cell and Molecular Biosciences, The Medical School , Newcastle University , Newcastle upon Tyne , UK.,b Department of Molecular Biology , University Medical Centre, Goettingen , Goettingen , Germany
| | - Andrew Alexander Knox
- a Institute for Cell and Molecular Biosciences, The Medical School , Newcastle University , Newcastle upon Tyne , UK
| | - Graeme Raymond Wells
- a Institute for Cell and Molecular Biosciences, The Medical School , Newcastle University , Newcastle upon Tyne , UK
| | - Claudia Schneider
- a Institute for Cell and Molecular Biosciences, The Medical School , Newcastle University , Newcastle upon Tyne , UK
| | - Nicholas James Watkins
- a Institute for Cell and Molecular Biosciences, The Medical School , Newcastle University , Newcastle upon Tyne , UK
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Rothé B, Manival X, Rolland N, Charron C, Senty-Ségault V, Branlant C, Charpentier B. Implication of the box C/D snoRNP assembly factor Rsa1p in U3 snoRNP assembly. Nucleic Acids Res 2017; 45:7455-7473. [PMID: 28505348 PMCID: PMC5499572 DOI: 10.1093/nar/gkx424] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 05/02/2017] [Indexed: 01/23/2023] Open
Abstract
The U3 box C/D snoRNA is one key element of 90S pre-ribosome. It contains a 5΄ domain pairing with pre-rRNA and the U3B/C and U3C΄/D motifs for U3 packaging into a unique small nucleolar ribonucleoprotein particle (snoRNP). The RNA-binding protein Snu13/SNU13 nucleates on U3B/C the assembly of box C/D proteins Nop1p/FBL and Nop56p/NOP56, and the U3-specific protein Rrp9p/U3-55K. Snu13p/SNU13 has a much lower affinity for U3C΄/D but nevertheless forms on this motif an RNP with box C/D proteins Nop1p/FBL and Nop58p/NOP58. In this study, we characterized the influence of the RNP assembly protein Rsa1 in the early steps of U3 snoRNP biogenesis in yeast and we propose a refined model of U3 snoRNP biogenesis. While recombinant Snu13p enhances the binding of Rrp9p to U3B/C, we observed that Rsa1p has no effect on this activity but forms with Snu13p and Rrp9p a U3B/C pre-RNP. In contrast, we found that Rsa1p enhances Snu13p binding on U3C΄/D. RNA footprinting experiments indicate that this positive effect most likely occurs by direct contacts of Rsa1p with the U3 snoRNA 5΄ domain. In light of the recent U3 snoRNP cryo-EM structures, our data suggest that Rsa1p has a dual role by also preventing formation of a pre-mature functional U3 RNP.
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Affiliation(s)
- Benjamin Rothé
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS Université de Lorraine, Biopôle, Campus Biologie Santé, 9 avenue de la forêt de Haye, BP 20199, 54505 Vandœuvre-lès-Nancy, France
| | - Xavier Manival
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS Université de Lorraine, Biopôle, Campus Biologie Santé, 9 avenue de la forêt de Haye, BP 20199, 54505 Vandœuvre-lès-Nancy, France
| | - Nicolas Rolland
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS Université de Lorraine, Biopôle, Campus Biologie Santé, 9 avenue de la forêt de Haye, BP 20199, 54505 Vandœuvre-lès-Nancy, France
| | - Christophe Charron
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS Université de Lorraine, Biopôle, Campus Biologie Santé, 9 avenue de la forêt de Haye, BP 20199, 54505 Vandœuvre-lès-Nancy, France
| | - Véronique Senty-Ségault
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS Université de Lorraine, Biopôle, Campus Biologie Santé, 9 avenue de la forêt de Haye, BP 20199, 54505 Vandœuvre-lès-Nancy, France
| | - Christiane Branlant
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS Université de Lorraine, Biopôle, Campus Biologie Santé, 9 avenue de la forêt de Haye, BP 20199, 54505 Vandœuvre-lès-Nancy, France
| | - Bruno Charpentier
- Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS Université de Lorraine, Biopôle, Campus Biologie Santé, 9 avenue de la forêt de Haye, BP 20199, 54505 Vandœuvre-lès-Nancy, France
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Falaleeva M, Welden JR, Duncan MJ, Stamm S. C/D-box snoRNAs form methylating and non-methylating ribonucleoprotein complexes: Old dogs show new tricks. Bioessays 2017; 39:10.1002/bies.201600264. [PMID: 28505386 PMCID: PMC5586538 DOI: 10.1002/bies.201600264] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
C/D box snoRNAs (SNORDs) are an abundantly expressed class of short, non-coding RNAs that have been long known to perform 2'-O-methylation of rRNAs. However, approximately half of human SNORDs have no predictable rRNA targets, and numerous SNORDs have been associated with diseases that show no defects in rRNAs, among them Prader-Willi syndrome, Duplication 15q syndrome and cancer. This apparent discrepancy has been addressed by recent studies showing that SNORDs can act to regulate pre-mRNA alternative splicing, mRNA abundance, activate enzymes, and be processed into shorter ncRNAs resembling miRNAs and piRNAs. Furthermore, recent biochemical studies have shown that a given SNORD can form both methylating and non-methylating ribonucleoprotein complexes, providing an indication of the likely physical basis for such diverse new functions. Thus, SNORDs are more structurally and functionally diverse than previously thought, and their role in gene expression is under-appreciated. The action of SNORDs in non-methylating complexes can be substituted with oligonucleotides, allowing devising therapies for diseases like Prader-Willi syndrome.
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Affiliation(s)
- Marina Falaleeva
- University Kentucky, Institute for Biochemistry, Lexington, KY, USA
| | - Justin R. Welden
- University Kentucky, Institute for Biochemistry, Lexington, KY, USA
| | | | - Stefan Stamm
- University Kentucky, Institute for Biochemistry, Lexington, KY, USA
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10
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Robust statistical modeling improves sensitivity of high-throughput RNA structure probing experiments. Nat Methods 2016; 14:83-89. [DOI: 10.1038/nmeth.4068] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 10/03/2016] [Indexed: 12/20/2022]
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Badertscher L, Wild T, Montellese C, Alexander L, Bammert L, Sarazova M, Stebler M, Csucs G, Mayer T, Zamboni N, Zemp I, Horvath P, Kutay U. Genome-wide RNAi Screening Identifies Protein Modules Required for 40S Subunit Synthesis in Human Cells. Cell Rep 2015; 13:2879-91. [DOI: 10.1016/j.celrep.2015.11.061] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 10/11/2015] [Accepted: 11/18/2015] [Indexed: 02/08/2023] Open
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12
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The NF45/NF90 Heterodimer Contributes to the Biogenesis of 60S Ribosomal Subunits and Influences Nucleolar Morphology. Mol Cell Biol 2015; 35:3491-503. [PMID: 26240280 DOI: 10.1128/mcb.00306-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 07/21/2015] [Indexed: 01/06/2023] Open
Abstract
The interleukin enhancer binding factors ILF2 (NF45) and ILF3 (NF90/NF110) have been implicated in various cellular pathways, such as transcription, microRNA (miRNA) processing, DNA repair, and translation, in mammalian cells. Using tandem affinity purification, we identified human NF45 and NF90 as components of precursors to 60S (pre-60S) ribosomal subunits. NF45 and NF90 are enriched in nucleoli and cosediment with pre-60S ribosomal particles in density gradient analysis. We show that association of the NF45/NF90 heterodimer with pre-60S ribosomal particles requires the double-stranded RNA binding domains of NF90, while depletion of NF45 and NF90 by RNA interference leads to a defect in 60S biogenesis. Nucleoli of cells depleted of NF45 and NF90 have altered morphology and display a characteristic spherical shape. These effects are not due to impaired rRNA transcription or processing of the precursors to 28S rRNA. Consistent with a role of the NF45/NF90 heterodimer in nucleolar steps of 60S subunit biogenesis, downregulation of NF45 and NF90 leads to a p53 response, accompanied by induction of the cyclin-dependent kinase inhibitor p21/CIP1, which can be counteracted by depletion of RPL11. Together, these data indicate that NF45 and NF90 are novel higher-eukaryote-specific factors required for the maturation of 60S ribosomal subunits.
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13
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Shishova KV, Khodarovich YM, Lavrentyeva EA, Zatsepina OV. High-resolution microscopy of active ribosomal genes and key members of the rRNA processing machinery inside nucleolus-like bodies of fully-grown mouse oocytes. Exp Cell Res 2015; 337:208-18. [PMID: 26226217 DOI: 10.1016/j.yexcr.2015.07.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 07/23/2015] [Accepted: 07/25/2015] [Indexed: 11/29/2022]
Abstract
Nucleolus-like bodies (NLBs) of fully-grown (germinal vesicle, GV) mammalian oocytes are traditionally considered as morphologically distinct entities, which, unlike normal nucleoli, contain transcribed ribosomal genes (rDNA) solely at their surface. In the current study, we for the first time showed that active ribosomal genes are present not only on the surface but also inside NLBs of the NSN-type oocytes. The "internal" rRNA synthesis was evidenced by cytoplasmic microinjections of BrUTP as precursor and by fluorescence in situ hybridization with a probe to the short-lived 5'ETS segment of the 47S pre-rRNA. We further showed that in the NLB mass of NSN-oocytes, distribution of active rDNA, RNA polymerase I (UBF) and rRNA processing (fibrillarin) protein factors, U3 snoRNA, pre-rRNAs and 18S/28S rRNAs is remarkably similar to that in somatic nucleoli capable to make pre-ribosomes. Overall, these observations support the occurrence of rDNA transcription, rRNA processing and pre-ribosome assembly in the NSN-type NLBs and so that their functional similarity to normal nucleoli. Unlike the NSN-type NLBs, the NLBs of more mature SN-oocytes do not contain transcribed rRNA genes, U3 snoRNA, pre-rRNAs, 18S and 28S rRNAs. These results favor the idea that in a process of transformation of NSN-oocytes to SN-oocytes, NLBs cease to produce pre-ribosomes and, moreover, lose their rRNAs. We also concluded that a denaturing fixative 70% ethanol used in the study to fix oocytes could be more appropriate for light microscopy analysis of nucleolar RNAs and proteins in mammalian fully-grown oocytes than a commonly used cross-linking aldehyde fixative, formalin.
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Affiliation(s)
- Kseniya V Shishova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russian Federation.
| | - Yuriy M Khodarovich
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russian Federation.
| | - Elena A Lavrentyeva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russian Federation; Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskiye Gory, MSU, 1-73, Office 433, 119991 Moscow, Russian Federation.
| | - Olga V Zatsepina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russian Federation.
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14
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Zhang L, Lin J, Ye K. Structural and functional analysis of the U3 snoRNA binding protein Rrp9. RNA (NEW YORK, N.Y.) 2013; 19:701-711. [PMID: 23509373 PMCID: PMC3677284 DOI: 10.1261/rna.037580.112] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 02/06/2013] [Indexed: 06/01/2023]
Abstract
The U3 snoRNA is required for 18S rRNA processing and small subunit ribosome formation in eukaryotes. Different from other box C/D snoRNAs, U3 contains an extra 5' domain that pairs with pre-rRNA and a unique B/C motif essential for recruitment of the U3-specific Rrp9 protein. Here, we analyze the structure and function of Rrp9 with crystallographic, biochemical, and cellular approaches. Rrp9 is composed of a WD repeat domain and an N-terminal region. The crystal structures of the WD domain of yeast Rrp9 and its human ortholog U3-55K were determined, revealing a typical seven-bladed propeller fold. Several conserved surface patches on the WD domain were identified, and their function in RNP assembly and yeast growth were analyzed by mutagenesis. Prior association of Snu13 with the B/C motif was found to enhance the specific binding of the WD domain. We show that a conserved 7bc loop is crucial for specific recognition of U3, nucleolar localization of Rrp9, and yeast growth. In addition, we show that the N-terminal region of Rrp9 contains a bipartite nuclear localization signal that is dispensable for nucleolar localization. Our results provide insight into the functional sites of Rrp9.
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MESH Headings
- Amino Acid Sequence/genetics
- Binding Sites
- Crystallography, X-Ray
- Humans
- Nucleic Acid Conformation
- Protein Folding
- Protein Structure, Tertiary
- RNA Processing, Post-Transcriptional
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 18S/metabolism
- RNA, Small Nucleolar/chemistry
- RNA, Small Nucleolar/genetics
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Ribonucleoproteins, Small Nucleolar/chemistry
- Ribonucleoproteins, Small Nucleolar/genetics
- Ribonucleoproteins, Small Nucleolar/metabolism
- Ribosome Subunits, Small, Eukaryotic/genetics
- Saccharomyces cerevisiae/chemistry
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Liman Zhang
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China
- National Institute of Biological Sciences, Beijing, Beijing 102206, China
| | - Jinzhong Lin
- National Institute of Biological Sciences, Beijing, Beijing 102206, China
| | - Keqiong Ye
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China
- National Institute of Biological Sciences, Beijing, Beijing 102206, China
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15
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Freed EF, Prieto JL, McCann KL, McStay B, Baserga SJ. NOL11, implicated in the pathogenesis of North American Indian childhood cirrhosis, is required for pre-rRNA transcription and processing. PLoS Genet 2012; 8:e1002892. [PMID: 22916032 PMCID: PMC3420923 DOI: 10.1371/journal.pgen.1002892] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Accepted: 06/20/2012] [Indexed: 01/12/2023] Open
Abstract
The fundamental process of ribosome biogenesis requires hundreds of factors and takes place in the nucleolus. This process has been most thoroughly characterized in baker's yeast and is generally well conserved from yeast to humans. However, some of the required proteins in yeast are not found in humans, raising the possibility that they have been replaced by functional analogs. Our objective was to identify non-conserved interaction partners for the human ribosome biogenesis factor, hUTP4/Cirhin, since the R565W mutation in the C-terminus of hUTP4/Cirhin was reported to cause North American Indian childhood cirrhosis (NAIC). By screening a yeast two-hybrid cDNA library derived from human liver, and through affinity purification followed by mass spectrometry, we identified an uncharacterized nucleolar protein, NOL11, as an interaction partner for hUTP4/Cirhin. Bioinformatic analysis revealed that NOL11 is conserved throughout metazoans and their immediate ancestors but is not found in any other phylogenetic groups. Co-immunoprecipitation experiments show that NOL11 is a component of the human ribosomal small subunit (SSU) processome. siRNA knockdown of NOL11 revealed that it is involved in the cleavage steps required to generate the mature 18S rRNA and is required for optimal rDNA transcription. Furthermore, abnormal nucleolar morphology results from the absence of NOL11. Finally, yeast two-hybrid analysis shows that NOL11 interacts with the C-terminus of hUTP4/Cirhin and that the R565W mutation partially disrupts this interaction. We have therefore identified NOL11 as a novel protein required for the early stages of ribosome biogenesis in humans. Our results further implicate a role for NOL11 in the pathogenesis of NAIC. Ribosomes are the cellular factories that produce proteins. Making a ribosome is a complex and energy intensive process that requires hundreds of different factors. Ribosome biogenesis is an essential process, and therefore mutations that partially disrupt this process lead to disease. One such disease is North American Indian childhood cirrhosis (NAIC), which is caused by a mutation in a ribosome biogenesis protein called hUTP4/Cirhin. We looked for proteins that interact with hUTP4/Cirhin, since we hypothesized that disruption of this interaction could play a role in the development of NAIC. We identified a novel protein called NOL11, which is only found in animals and not in any other organisms. We showed that NOL11 is required for ribosome biogenesis and acts at one of the earliest steps in this process. We then showed that NOL11 interacts with the region of hUTP4/Cirhin that contains the NAIC mutation and that the NAIC mutation interferes with the interaction between hUTP4/Cirhin and NOL11. Further study of the interaction between hUTP4/Cirhin and NOL11 will give insight into the development of NAIC, as well as elucidate some of the differences in ribosome biogenesis between animals and other organisms.
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Affiliation(s)
- Emily F. Freed
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - José-Luis Prieto
- Centre for Chromosome Biology, School of Life Sciences, National University of Ireland Galway, Galway, Ireland
| | - Kathleen L. McCann
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Brian McStay
- Centre for Chromosome Biology, School of Life Sciences, National University of Ireland Galway, Galway, Ireland
| | - Susan J. Baserga
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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16
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Wu J, Zhang Y, Wang Y, Kong R, Hu L, Schuele R, Du X, Ke Y. Transcriptional repressor NIR functions in the ribosome RNA processing of both 40S and 60S subunits. PLoS One 2012; 7:e31692. [PMID: 22363708 PMCID: PMC3282729 DOI: 10.1371/journal.pone.0031692] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Accepted: 01/17/2012] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND NIR was identified as an inhibitor of histone acetyltransferase and it represses transcriptional activation of p53. NIR is predominantly localized in the nucleolus and known as Noc2p, which is involved in the maturation of the 60S ribosomal subunit. However, how NIR functions in the nucleolus remains undetermined. In the nucleolus, a 47S ribosomal RNA precursor (pre-rRNA) is transcribed and processed to produce 18S, 5.8S and 28S rRNAs. The 18S rRNA is incorporated into the 40S ribosomal subunit, whereas the 28S and 5.8S rRNAs are incorporated into the 60S subunit. U3 small nucleolar RNA (snoRNA) directs 18S rRNA processing and U8 snoRNA mediates processing of 28S and 5.8 S rRNAs. Functional disruption of nucleolus often causes p53 activation to inhibit cell proliferation. METHODOLOGY/PRINCIPAL FINDINGS Western blotting showed that NIR is ubiquitously expressed in different human cell lines. Knock-down of NIR by siRNA led to inhibition of the 18S, 28S and 5.8S rRNAs evaluated by pulse-chase experiment. Pre-rRNA particles (pre-rRNPs) were fractionated from the nucleus by sucrose gradient centrifugation and analysis of the pre-RNPs components showed that NIR existed in the pre-RNPs of both the 60S and 40S subunits and co-fractionated with 32S and 12S pre-rRNAs in the 60S pre-rRNP. Protein-RNA binding experiments demonstrated that NIR is associated with the 32S pre-rRNA and U8 snoRNA. In addition, NIR bound U3 snoRNA. It is a novel finding that depletion of NIR did not affect p53 protein level but de-repressed acetylation of p53 and activated p21. CONCLUSIONS We provide the first evidence for a transcriptional repressor to function in the rRNA biogenesis of both the 40S and 60S subunits. Our findings also suggested that a nucleolar protein may alternatively signal to p53 by affecting the p53 modification rather than affecting p53 protein level.
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Affiliation(s)
- Jianguo Wu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital & Institute, Beijing, China
| | - Ying Zhang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital & Institute, Beijing, China
| | - Yingshuang Wang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital & Institute, Beijing, China
| | - Ruirui Kong
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital & Institute, Beijing, China
| | - Lelin Hu
- Department of Cell Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Roland Schuele
- Medical Research Center, Freiburg University, Freiburg, Germany
| | - Xiaojuan Du
- Department of Cell Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Yang Ke
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital & Institute, Beijing, China
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17
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Turner AJ, Knox AA, Watkins NJ. Nucleolar disruption leads to the spatial separation of key 18S rRNA processing factors. RNA Biol 2012; 9:175-86. [PMID: 22418842 DOI: 10.4161/rna.18811] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Many chemotherapeutic drugs cause the downregulation of ribosome production and the disruption of nucleolar function. This stabilizes p53 and leads to either cell cycle arrest or apoptosis. It is not clear, however, how these agents cause nucleolar disruption and block ribosome production. The small subunit (SSU) processome, which has been primarily studied in yeast, is responsible for the processing of the 18S rRNA and assembly of the small ribosomal subunit. Here we have characterized the human homologs of seven SSU processome components. Furthermore, we have investigated the effects of three chemotherapeutic drugs, Actinomycin D (ActD), camptothecin (CPT) and 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) on the subcellular distribution of key SSU processome components and the formation of this processing complex. Interestingly, ActD- and DRB-treatment resulted in the majority of U3 small nucleolar RNP (snoRNP) localizing separately to other key components of the SSU processome. All three agents affected RNA polymerase I transcription, primarily at the level of elongation but only ActD resulted in a clear reduction in SSU processome levels. Taken together, our data indicate that different chemotherapeutic agents, each of which initiates a stress response and cause nucleolar disruption, have different effects on the formation and localization of the SSU processome.
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Affiliation(s)
- Amy Jane Turner
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
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18
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Watkins NJ, Bohnsack MT. The box C/D and H/ACA snoRNPs: key players in the modification, processing and the dynamic folding of ribosomal RNA. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 3:397-414. [DOI: 10.1002/wrna.117] [Citation(s) in RCA: 347] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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19
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Marmier-Gourrier N, Cléry A, Schlotter F, Senty-Ségault V, Branlant C. A second base pair interaction between U3 small nucleolar RNA and the 5'-ETS region is required for early cleavage of the yeast pre-ribosomal RNA. Nucleic Acids Res 2011; 39:9731-45. [PMID: 21890904 PMCID: PMC3239212 DOI: 10.1093/nar/gkr675] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In eukaryotes, U3 snoRNA is essential for pre-rRNA maturation. Its 5'-domain was found to form base pair interactions with the 18S and 5'-ETS parts of the pre-rRNA. In Xenopus laevis, two segments of U3 snoRNA form base-pair interactions with the 5'-ETS region and only one of them is essential to the maturation process. In Saccharomyces cerevisiae, two similar U3 snoRNA-5' ETS interactions are possible; but, the functional importance of only one of them had been tested. Surprisingly, this interaction, which corresponds to the non-essential one in X. laevis, is essential for cell growth and pre-rRNA maturation in yeast. In parallel with [Dutca et al. (2011) The initial U3 snoRNA:pre-rRNA base pairing interaction required for pre-18S rRNA folding revealed by in vivo chemical probing. Nucleic Acids Research, 39, 5164-5180], here we show, that the second possible 11-bp long interaction between the 5' domain of S. cerevisiae U3 snoRNA and the pre-rRNA 5'-ETS region (helix VI) is also essential for pre-rRNA processing and cell growth. Compensatory mutations in one-half of helix VI fully restored cell growth. Only a partial restoration of growth was obtained upon extension of compensatory mutations to the entire helix VI, suggesting sequence requirement for binding of specific proteins. Accordingly, we got strong evidences for a role of segment VI in the association of proteins Mpp10, Imp4 and Imp3.
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Affiliation(s)
- Nathalie Marmier-Gourrier
- Faculté des Sciences et Technologies, Nancy University, UMR AREMS 7214 CNRS-UHP, Boulevard des Aiguillettes, BP70239, 54506 Vandoeuvre-Lès-Nancy cedex, France
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20
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Pérez-Fernández J, Martín-Marcos P, Dosil M. Elucidation of the assembly events required for the recruitment of Utp20, Imp4 and Bms1 onto nascent pre-ribosomes. Nucleic Acids Res 2011; 39:8105-21. [PMID: 21724601 PMCID: PMC3185420 DOI: 10.1093/nar/gkr508] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The 90S pre-ribosome, also known as the small subunit (SSU) processome, is a large multisubunit particle required for the production of the 18S rRNA from a pre-rRNA precursor. Recently, it has been shown that the formation of this particle entails the initial association of the tUTP subunit with the nascent pre-RNA and, subsequently, the binding of Rrp5/UTP-C and U3 snoRNP/UTP-B subunits in two independent assembly branches. However, the mode of assembly of other 90S pre-ribosome components remains obscure as yet. In this study, we have investigated the assembly of three proteins (Utp20, Imp4 and Bms1) previously regarded as potential nucleating factors of the 90S particle. Here, we demonstrate that the loading of those three proteins onto the pre-rRNA takes place independently of Rrp5/UTP-C and, instead, occurs downstream of the tUTP and U3/UTP-B subcomplexes. We also demonstrate that Bms1 and Utp20 are required for the recruitment of a subset of proteins to nascent pre-ribosomes. Finally, we show that proteins associated through secondary steps condition the stability of the two assembly branches in partially assembled pre-ribosomes. These results provide new information about the functional relationships among 90S particle components and the events that are required for their stepwise incorporation onto the primary pre-rRNA.
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Affiliation(s)
- Jorge Pérez-Fernández
- Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer, CSIC-University of Salamanca, Campus Unamuno s/n, E37007 Salamanca, Spain
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21
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Yoshikawa H, Komatsu W, Hayano T, Miura Y, Homma K, Izumikawa K, Ishikawa H, Miyazawa N, Tachikawa H, Yamauchi Y, Isobe T, Takahashi N. Splicing factor 2-associated protein p32 participates in ribosome biogenesis by regulating the binding of Nop52 and fibrillarin to preribosome particles. Mol Cell Proteomics 2011; 10:M110.006148. [PMID: 21536856 DOI: 10.1074/mcp.m110.006148] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribosome biogenesis starts with transcription of the large ribosomal RNA precursor (47S pre-rRNA), which soon combines with numerous factors to form the 90S pre-ribosome in the nucleolus. Although the subsequent separation of the pre-90S particle into pre-40S and pre-60S particles is critical for the production process of mature small and large ribosomal subunits, its molecular mechanisms remain undetermined. Here, we present evidence that p32, fibrillarin (FBL), and Nop52 play key roles in this separation step. Mass-based analyses combined with immunoblotting showed that p32 associated with 155 proteins including 31 rRNA-processing factors (of which nine were components of small subunit processome, and six were those of RIX1 complex), 13 chromatin remodeling components, and six general transcription factors required for RNA polymerase III-mediated transcription. Of these, a late rRNA-processing factor Nop52 interacted directly with p32. Immunocytochemical analyses demonstrated that p32 colocalized with an early rRNA-processing factor FBL or Nop52 in the nucleolus and Cajal bodies, but was excluded from the nucleolus after actinomycin D treatment. p32 was present in the pre-ribosomal fractions prepared by cell fractionation or separated by ultracentrifugation of the nuclear extract. p32 also associated with pre-rRNAs including 47S/45S and 32S pre-rRNAs. Furthermore, knockdown of p32 with a small interfering RNA slowed the early processing from 47S/45S pre-rRNAs to 18S rRNA and 32S pre-rRNA. Finally, Nop52 was found to compete with FBL for binding to p32 probably in the nucleolus. Given the fact that FBL and Nop52 are associated with pre-ribosome particles distinctly different from each other, we suggest that p32 is a new rRNA maturation factor involved in the remodeling from pre-90S particles to pre-40S and pre-60S particles that requires the exchange of FBL for Nop52.
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Affiliation(s)
- Harunori Yoshikawa
- Department of Applied Life Science, United Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan
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22
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Abstract
The rate of ribosome biogenesis, which is downregulated in terminally differentiated cells and upregulated in most cancers, regulates the growth rate and is linked to the cell's proliferative potential. The U3 box C/D small nucleolar RNP (snoRNP) is an integral component of the small subunit (SSU) processome and is essential for 18S rRNA processing. We show that U3 snoRNP assembly, and therefore U3 snoRNA accumulation, is regulated through the U3-specific protein hU3-55K. Furthermore, we report that the levels of several SSU processome components, including the U3 snoRNA but not other box C/D snoRNAs, are specifically downregulated during human lung (CaCo-2) and colon (CaLu-3) epithelial cell differentiation. c-Myc is reported to play an integral role in regulating ribosome production by controlling the expression of many ribosome biogenesis factors. Our data, however, indicate that this regulation is not dependent on c-Myc since the level of this protein does not change during epithelial cell differentiation. In addition, depletion of c-Myc had only a mild affect on the levels of SSU processome proteins. CaCo-2 cells are colon adenocarcinoma epithelial cells that are believed to revert to their precancerous state during differentiation. This suggests a significant increase in the levels of specific SSU processome components during tumorogenesis.
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23
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Boesler C, Kruse J, Söderbom F, Hammann C. Sequence and generation of mature ribosomal RNA transcripts in Dictyostelium discoideum. J Biol Chem 2011; 286:17693-703. [PMID: 21454536 DOI: 10.1074/jbc.m110.208306] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The amoeba Dictyostelium discoideum is a well established model organism for studying numerous aspects of cellular and developmental functions. Its ribosomal RNA (rRNA) is encoded in an extrachromosomal palindrome that exists in ∼100 copies in the cell. In this study, we have set out to investigate the sequence of the expressed rRNA. For this, we have ligated the rRNA ends and performed RT-PCR on these circular RNAs. Sequencing revealed that the mature 26 S, 17 S, 5.8 S, and 5 S rRNAs have sizes of 3741, 1871, 162, and 112 nucleotides, respectively. Unlike the published data, all mature rRNAs of the same type uniformly display the same start and end nucleotides in the analyzed AX2 strain. We show the existence of a short lived primary transcript covering the rRNA transcription unit of 17 S, 5.8 S, and 26 S rRNA. Northern blots and RT-PCR reveal that from this primary transcript two precursor molecules of the 17 S and two precursors of the 26 S rRNA are generated. We have also determined the sequences of these precursor molecules, and based on these data, we propose a model for the maturation of the rRNAs in Dictyostelium discoideum that we compare with the processing of the rRNA transcription unit of Saccharomyces cerevisiae.
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Affiliation(s)
- Carsten Boesler
- Heisenberg Research Group Ribogenetics, Technical University of Darmstadt, 64287 Darmstadt, Germany
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24
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Dutca LM, Gallagher JEG, Baserga SJ. The initial U3 snoRNA:pre-rRNA base pairing interaction required for pre-18S rRNA folding revealed by in vivo chemical probing. Nucleic Acids Res 2011; 39:5164-80. [PMID: 21349877 PMCID: PMC3130255 DOI: 10.1093/nar/gkr044] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The synthesis of ribosomal subunits in the nucleolus is a conserved, essential process that results in cytoplasmic ribosomes with precisely processed and folded rRNAs assembled with ribosomal proteins. It has been proposed, but never directly demonstrated, that the U3 small nucleolar RNA (snoRNA), a nucleolar component required for ribosome biogenesis, is a chaperone for pre-18S rRNA folding. To test this, we used in vivo chemical probing with dimethyl sulfate to detect changes in pre-rRNA structure upon genetic manipulation of the yeast, Saccharomyces cerevisiae. Based on changes in nucleotide reactivity, we found that the U3 snoRNA is indeed required for folding of the pre-18S rRNA. Furthermore, we detected a new essential base pairing interaction that is likely the initial anchor that recruits the U3 snoRNA to the pre-rRNA, is a prerequisite for the subsequent interactions, and is required for the small subunit processome formation. Substitution of the 5′-ETS nucleotides of the pre-rRNA involved in this initial base pairing interaction is lethal, but growth is restored when a complementary U3 snoRNA is expressed. The U3 snoRNP, via base pairing, and its associated proteins, are part of the required machinery that orchestrates the folding of pre-rRNA that results in the assembly of the small ribosomal subunit.
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Affiliation(s)
- Laura M Dutca
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA
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25
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Underwood JG, Uzilov AV, Katzman S, Onodera CS, Mainzer JE, Mathews DH, Lowe TM, Salama SR, Haussler D. FragSeq: transcriptome-wide RNA structure probing using high-throughput sequencing. Nat Methods 2010; 7:995-1001. [PMID: 21057495 PMCID: PMC3247016 DOI: 10.1038/nmeth.1529] [Citation(s) in RCA: 242] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 10/13/2010] [Indexed: 01/07/2023]
Abstract
Previous efforts to determine structures of non-coding RNA (ncRNA) probed only one RNA at a time with enzymes and chemicals, using gel electrophoresis to identify reactive positions. To accelerate RNA structure inference, we have developed FragSeq, a high-throughput RNA structure probing method that uses high-throughput RNA sequencing on fragments generated by nuclease P1, which specifically cleaves single stranded nucleic acids. In experiments probing the entire mouse nuclear transcriptome, we show that we can accurately and simultaneously map single-stranded regions (ssRNA) in multiple ncRNAs with known structure. We carried out probing in two cell types to demonstrate reproducibility. We also identified and experimentally validated structured regions in ncRNAs never previously probed.
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Affiliation(s)
- Jason G Underwood
- Howard Hughes Medical Institute, University of California Santa Cruz, Santa Cruz, California, USA
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26
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Dean P, Scott JA, Knox AA, Quitard S, Watkins NJ, Kenny B. The enteropathogenic E. coli effector EspF targets and disrupts the nucleolus by a process regulated by mitochondrial dysfunction. PLoS Pathog 2010; 6:e1000961. [PMID: 20585567 PMCID: PMC2891835 DOI: 10.1371/journal.ppat.1000961] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Accepted: 05/24/2010] [Indexed: 01/09/2023] Open
Abstract
The nucleolus is a multifunctional structure within the nucleus of eukaryotic cells and is the primary site of ribosome biogenesis. Almost all viruses target and disrupt the nucleolus--a feature exclusive to this pathogen group. Here, using a combination of bio-imaging, genetic and biochemical analyses, we demonstrate that the enteropathogenic E. coli (EPEC) effector protein EspF specifically targets the nucleolus and disrupts a subset of nucleolar factors. Driven by a defined N-terminal nucleolar targeting domain, EspF causes the complete loss from the nucleolus of nucleolin, the most abundant nucleolar protein. We also show that other bacterial species disrupt the nucleolus, dependent on their ability to deliver effector proteins into the host cell. Moreover, we uncover a novel regulatory mechanism whereby nucleolar targeting by EspF is strictly controlled by EPEC's manipulation of host mitochondria. Collectively, this work reveals that the nucleolus may be a common feature of bacterial pathogenesis and demonstrates that a bacterial pathogen has evolved a highly sophisticated mechanism to enable spatio-temporal control over its virulence proteins.
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Affiliation(s)
- Paul Dean
- Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | - Jon A. Scott
- Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | - Andrew A. Knox
- Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | - Sabine Quitard
- Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | - Nicholas J. Watkins
- Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | - Brendan Kenny
- Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle, Newcastle upon Tyne, United Kingdom
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27
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Mrd1p is required for release of base-paired U3 snoRNA within the preribosomal complex. Mol Cell Biol 2009; 29:5763-74. [PMID: 19704003 DOI: 10.1128/mcb.00428-09] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In eukaryotes, ribosomes are made from precursor rRNA (pre-rRNA) and ribosomal proteins in a maturation process that requires a large number of snoRNPs and processing factors. A fundamental problem is how the coordinated and productive folding of the pre-rRNA and assembly of successive pre-rRNA-protein complexes is achieved cotranscriptionally. The conserved protein Mrd1p, which contains five RNA binding domains (RBDs), is essential for processing events leading to small ribosomal subunit synthesis. We show that full function of Mrd1p requires all five RBDs and that the RBDs are functionally distinct and needed during different steps in processing. Mrd1p mutations trap U3 snoRNA in pre-rRNP complexes both in base-paired and non-base-paired interactions. A single essential RBD, RBD5, is involved in both types of interactions, but its conserved RNP1 motif is not needed for releasing the base-paired interactions. RBD5 is also required for the late pre-rRNP compaction preceding A(2) cleavage. Our results suggest that Mrd1p modulates successive conformational rearrangements within the pre-rRNP that influence snoRNA-pre-rRNA contacts and couple U3 snoRNA-pre-rRNA remodeling and late steps in pre-rRNP compaction that are essential for cleavage at A(0) to A(2). Mrd1p therefore coordinates key events in biosynthesis of small ribosome subunits.
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28
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Turner AJ, Knox AA, Prieto JL, McStay B, Watkins NJ. A novel small-subunit processome assembly intermediate that contains the U3 snoRNP, nucleolin, RRP5, and DBP4. Mol Cell Biol 2009; 29:3007-17. [PMID: 19332556 PMCID: PMC2682003 DOI: 10.1128/mcb.00029-09] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 02/12/2009] [Accepted: 03/24/2009] [Indexed: 11/20/2022] Open
Abstract
Eukaryotic 18S rRNA processing is mediated by the small subunit (SSU) processome, a machine comprised of the U3 small nucleolar RNP (U3 snoRNP), tUTP, bUTP, MPP10, and BMS1/RCL1 subcomplexes. We report that the human SSU processome is a dynamic structure with the recruitment and release of subcomplexes occurring during the early stages of ribosome biogenesis. A novel 50S U3 snoRNP accumulated when either pre-rRNA transcription was blocked or the tUTP proteins were depleted. This complex did not contain the tUTP, bUTP, MPP10, and BMS1/RCL1 subcomplexes but was associated with the RNA-binding proteins nucleolin and RRP5 and the RNA helicase DBP4. Our data suggest that the 50S U3 snoRNP is an SSU assembly intermediate that is likely recruited to the pre-rRNA through the RNA-binding proteins nucleolin and RRP5. We predict that nucleolin is only transiently associated with the SSU processome and likely leaves the complex not long after 50S U3 snoRNP recruitment. The nucleolin-binding site potentially overlaps that of several other key factors, and we propose that this protein must leave the SSU processome for pre-rRNA processing to occur.
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Affiliation(s)
- Amy Jane Turner
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom
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29
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Nabavi S, Nellimarla S, Nazar RN. Post-transcriptional Regulation of the U3 Small Nucleolar RNA. J Biol Chem 2008; 283:21404-10. [DOI: 10.1074/jbc.m802189200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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31
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Watkins NJ, Lemm I, Lührmann R. Involvement of nuclear import and export factors in U8 box C/D snoRNP biogenesis. Mol Cell Biol 2007; 27:7018-27. [PMID: 17709390 PMCID: PMC2168896 DOI: 10.1128/mcb.00516-07] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Box C/D snoRNPs, factors essential for ribosome biogenesis, are proposed to be assembled in the nucleoplasm before localizing to the nucleolus. However, recent work demonstrated the involvement of nuclear export factors in this process, suggesting that export may take place. Here we show that there are distinct distributions of U8 pre-snoRNAs and pre-snoRNP complexes in HeLa cell nuclear and cytoplasmic extracts. We observed differential association of nuclear export (PHAX, CRM1, and Ran) factors with complexes in the two extracts, consistent with nucleocytoplasmic transport. Furthermore, we show that the U8 pre-snoRNA in one of the cytoplasmic complexes contains an m3G cap and is associated with the nuclear import factor Snurportin1. Using RNA interference, we show that loss of either PHAX or Snurportin1 results in the incorrect localization of the U8 snoRNA. Our data therefore show that nuclear export and import factors are directly involved in U8 box C/D snoRNP biogenesis. The distinct distribution of U8 pre-snoRNP complexes between the two cellular compartments together with the association of both nuclear import and export factors with the precursor complex suggests that the mammalian U8 snoRNP is exported during biogenesis.
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Affiliation(s)
- Nicholas J Watkins
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom.
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32
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McKeegan KS, Debieux CM, Boulon S, Bertrand E, Watkins NJ. A dynamic scaffold of pre-snoRNP factors facilitates human box C/D snoRNP assembly. Mol Cell Biol 2007; 27:6782-93. [PMID: 17636026 PMCID: PMC2099223 DOI: 10.1128/mcb.01097-07] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The box C/D small nucleolar RNPs (snoRNPs) are essential for the processing and modification of rRNA. The core box C/D proteins are restructured during human U3 box C/D snoRNP biogenesis; however, the molecular basis of this is unclear. Here we show that the U8 snoRNP is also restructured, suggesting that this may occur with all box C/D snoRNPs. We have characterized four novel human biogenesis factors (BCD1, NOP17, NUFIP, and TAF9) which, along with the ATPases TIP48 and TIP49, are likely to be involved in the formation of the pre-snoRNP. We have analyzed the in vitro protein-protein interactions between the assembly factors and core box C/D proteins. Surprisingly, this revealed few interactions between the individual core box C/D proteins. However, the novel biogenesis factors and TIP48 and TIP49 interacted with one or more of the core box C/D proteins, implying that they mediate the assembly of the pre-snoRNP. Consistent with this, we show that NUFIP bridges interactions between the core box C/D proteins in a partially reconstituted pre-snoRNP. Restructuring of the core complex probably reflects the conversion of the pre-snoRNP, where core protein-protein interactions are maintained by the bridging biogenesis factors, to the mature snoRNP.
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Affiliation(s)
- Kenneth Scott McKeegan
- Institute for Cell and Molecular Biosciences, University of Newcastle upon Tyne, Newcastle upon Tyne, UK
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33
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Hogg JR, Collins K. RNA-based affinity purification reveals 7SK RNPs with distinct composition and regulation. RNA (NEW YORK, N.Y.) 2007; 13:868-80. [PMID: 17456562 PMCID: PMC1869041 DOI: 10.1261/rna.565207] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Recent studies have uncovered an unanticipated diversity of noncoding RNAs (ncRNAs), although these studies provide limited insight into their biological significance. Numerous general methods for identification and characterization of protein interactions have been developed, but similar approaches for characterizing cellular ncRNA interactions are lacking. Here we describe RNA Affinity in Tandem (RAT), an original, entirely RNA tag-based method for affinity purification of endogenously assembled RNP complexes. We demonstrate the general utility of RAT by isolating RNPs assembled in vivo on ncRNAs transcribed by RNA polymerase II or III. Using RAT in conjunction with protein identification by mass spectrometry and protein-RNA interaction assays, we define and characterize previously unanticipated protein subunits of endogenously assembled human 7SK RNPs. We show that 7SK RNA resides in a mixed population of RNPs with different protein compositions and responses to cellular stress. Depletion of a newly identified 7SK RNP component, hnRNP K, alters the partitioning of 7SK RNA among distinct RNPs. Our results establish the utility of a generalizable RNA-based RNP affinity purification method and provide insight into 7SK RNP dynamics.
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Affiliation(s)
- J Robert Hogg
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720-3200, USA
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34
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Wang Y, Liu J, Zhao H, Lü W, Zhao J, Yang L, Li N, Du X, Ke Y. Human 1A6/DRIM, the homolog of yeast Utp20, functions in the 18S rRNA processing. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:863-8. [PMID: 17498821 DOI: 10.1016/j.bbamcr.2007.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Revised: 04/05/2007] [Accepted: 04/05/2007] [Indexed: 11/29/2022]
Abstract
1A6/DRIM is a nucleolar protein with a nucleolar targeting sequence in its 3'-terminus. Bioinformatic analysis indicated that human 1A6/DRIM shares 23% identity and 43% similarity with yeast Utp20, which has been reported as a component of U3 snoRNA protein complex and has been implicated in 18S rRNA processing. In the present study, we found, by utilizing RT-PCR with RNA extracted from anti-1A6/DRIM immunoprecipitates and Northern blotting, that 1A6/DRIM is associated with U3 snoRNA. Pulse-chase labeling assays showed that silencing of 1A6/DRIM expression in HeLa cells resulted in a delayed 18S rRNA processing. Furthermore, immunoprecipitations revealed that 1A6/DRIM was also associated with fibrillarin, another U3 RNP component in HeLa cells. These results indicate that 1A6/DRIM is involved in 18S rRNA processing and is the bona fide mammalian Utp20.
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Affiliation(s)
- You Wang
- Beijing Institute for Cancer Research, School of Oncology, Peking University, 52 Fucheng Road, Beijing 100036, China
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35
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Schultz A, Nottrott S, Watkins NJ, Lührmann R. Protein-protein and protein-RNA contacts both contribute to the 15.5K-mediated assembly of the U4/U6 snRNP and the box C/D snoRNPs. Mol Cell Biol 2006; 26:5146-54. [PMID: 16782898 PMCID: PMC1489164 DOI: 10.1128/mcb.02374-05] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The k-turn-binding protein 15.5K is unique in that it is essential for the hierarchical assembly of three RNP complexes distinct in both composition and function, namely, the U4/U6 snRNP, the box C/D snoRNP, and the RNP complex assembled on the U3 box B/C motif. 15.5K interacts with the cognate RNAs via an induced fit mechanism, which results in the folding of the surrounding RNA to create a binding site(s) for the RNP-specific proteins. However, it is possible that 15.5K also mediates RNP formation via protein-protein interactions with the complex-specific proteins. To investigate this possibility, we created a series of 15.5K mutations in which the surface properties of the protein had been changed. We assessed their ability to support the formation of the three distinct RNP complexes and found that the formation of each RNP requires a distinct set of regions on the surface of 15.5K. This implies that protein-protein contacts are essential for RNP formation in each complex. Further supporting this idea, direct protein-protein interaction could be observed between hU3-55K and 15.5K. In conclusion, our data suggest that the formation of each RNP involves the direct recognition of specific elements in both 15.5K protein and the specific RNA.
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Affiliation(s)
- Annemarie Schultz
- Max Planck Institute of Biophysical Chemistry, Am Fassberg 11, D-37070 Göttingen, Germany
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36
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Bax R, Vos HR, Raué HA, Vos JC. Saccharomyces cerevisiae Sof1p associates with 35S Pre-rRNA independent from U3 snoRNA and Rrp5p. EUKARYOTIC CELL 2006; 5:427-34. [PMID: 16524898 PMCID: PMC1398065 DOI: 10.1128/ec.5.3.427-434.2006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sof1p is a trans-acting protein that is essential for biogenesis of the 40S ribosomal subunits in the yeast Saccharomyces cerevisiae. Because of its involvement in the early cleavage steps of precursor rRNA, its interaction with Nop1p and its ability to coprecipitate U3 snoRNA, Sof1p has so far been regarded as a protein that is specific to the U3 snoRNP. To determine whether a site exists within U3 snoRNA with which Sof1p directly or indirectly associates, we studied the ability of ProtA-tagged Sof1p to coimmunoprecipitate mutant versions of U3 snoRNA. None of the tested mutations had a significant effect on the recovery of mutant U3 from cell extracts. Further coimmunoprecipitation experiments, using cells that could be genetically depleted for either Sof1p or U3 snoRNA demonstrated that the two factors associate independently of each other with the 35S precursor RNA. Indeed, association between Sof1p and U3 snoRNA was abolished in cells in which 35S pre-rRNA transcription was blocked. Finally, we found that an overall reduction in the levels of box C/D snoRNPs by genetic depletion of the common Nop58p protein did not affect coprecipitation of 35S pre-rRNA by Sof1p. From these data, we conclude that Sof1p does not assemble into the 90S preribosome as part of the U3, or any other box C/D, snoRNP. The early and independently assembling trans-acting factor Rrp5p also proved to be dispensable for assembly of Sof1p.
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Affiliation(s)
- Ralph Bax
- Section of Biochemistry and Molecular Biology, FEW, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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37
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Borovjagin AV, Gerbi SA. An evolutionary intra-molecular shift in the preferred U3 snoRNA binding site on pre-ribosomal RNA. Nucleic Acids Res 2005; 33:4995-5005. [PMID: 16147982 PMCID: PMC1199564 DOI: 10.1093/nar/gki815] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Correct docking of U3 small nucleolar RNA (snoRNA) on pre-ribosomal RNA (pre-rRNA) is essential for rRNA processing to produce 18S rRNA. In this report, we have used Xenopus oocytes to characterize the structural requirements of the U3 snoRNA 3′-hinge interaction with region E1 of the external transcribed spacer (ETS) of pre-rRNA. This interaction is crucial for docking to initiate rRNA processing. 18S rRNA production was inhibited when fewer than 6 of the 8 bp of the U3 3′–hinge complex with the ETS could form; moreover, base pairing involving the right side of the 3′-hinge was more important than the left. Increasing the length of the U3 hinge–ETS interaction by 9 bp impaired rRNA processing. Formation of 18S rRNA was also inhibited by swapping the U3 5′- and 3′-hinge interactions with the ETS or by shifting the base pairing of the U3 3′-hinge to the sequence directly adjacent to ETS region E1. However, 18S rRNA production was partially restored by a compensatory shift that allowed the sequence adjacent to the U3 3′-hinge to pair with the eight bases directly adjacent to ETS region E1. The results suggest that the geometry of the U3 snoRNA interaction with the ETS is critical for rRNA processing.
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MESH Headings
- Animals
- Base Pairing
- Base Sequence
- Binding Sites
- Evolution, Molecular
- Molecular Sequence Data
- Mutation
- RNA Precursors/chemistry
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional
- RNA, Ribosomal, 18S/chemistry
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 18S/metabolism
- RNA, Small Nucleolar/chemistry
- RNA, Small Nucleolar/genetics
- RNA, Small Nucleolar/metabolism
- Xenopus laevis
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Affiliation(s)
| | - Susan A. Gerbi
- To whom correspondence should be addressed. Tel: +1 401 863 2359; Fax: +1 401 863 1348;
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