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Lourenço RF, Leme AFP, Oliveira CC. Proteomic Analysis of Yeast Mutant RNA Exosome Complexes. J Proteome Res 2013; 12:5912-22. [DOI: 10.1021/pr400972x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rogério F. Lourenço
- Department
of Biochemistry, Chemistry Institute, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
| | - Adriana F. P. Leme
- Mass
Spectrometry Laboratory, Brazilian Biosciences National Laboratory- CNPEM, R. Giuseppe Máximo Scolfaro 10000, 13083-970 Campinas, Brazil
| | - Carla C. Oliveira
- Department
of Biochemistry, Chemistry Institute, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
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52
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Feigenbutz M, Garland W, Turner M, Mitchell P. The exosome cofactor Rrp47 is critical for the stability and normal expression of its associated exoribonuclease Rrp6 in Saccharomyces cerevisiae. PLoS One 2013; 8:e80752. [PMID: 24224060 PMCID: PMC3818262 DOI: 10.1371/journal.pone.0080752] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 10/15/2013] [Indexed: 11/18/2022] Open
Abstract
Rrp6 is a conserved catalytic subunit of the eukaryotic nuclear exosome ribonuclease complex that functions in the productive 3' end maturation of stable RNAs, the degradation of transiently expressed noncoding transcripts and in discard pathways that eradicate the cell of incorrectly processed or assembled RNAs. The function of Rrp6 in these pathways is at least partially dependent upon its interaction with a small nuclear protein called Rrp47/Lrp1, but the underlying mechanism(s) by which Rrp47 functions in concert with Rrp6 are not established. Previous work on yeast grown in rich medium has suggested that Rrp6 expression is not markedly reduced in strains lacking Rrp47. Here we show that Rrp6 expression in rrp47∆ mutants is substantially reduced during growth in minimal medium through effects on both transcript levels and protein stability. Exogenous expression of Rrp6 enables normal levels to be attained in rrp47∆ mutants. Strikingly, exogenous expression of Rrp6 suppresses many, but not all, of the RNA processing and maturation defects observed in an rrp47∆ mutant and complements the synthetic lethality of rrp47∆ mpp6∆ and rrp47∆ rex1∆ double mutants. Increased Rrp6 expression in the resultant rrp47∆ rex1∆ double mutant suppresses the defect in the 3' maturation of box C/D snoRNAs. In contrast, increased Rrp6 expression in the rrp47∆ mpp6∆ double mutant diminishes the block in the turnover of CUTs and in the degradation of the substrates of RNA discard pathways. These results demonstrate that a principal function of Rrp47 is to facilitate appropriate expression levels of Rrp6 and support the conclusion that the Rrp6/Rrp47 complex and Rex1 provide redundant exonuclease activities for the 3' end maturation of box C/D snoRNAs.
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Affiliation(s)
- Monika Feigenbutz
- Molecular Biology and Biotechnology Department, The University of Sheffield, Sheffield, United Kingdom
| | - William Garland
- Molecular Biology and Biotechnology Department, The University of Sheffield, Sheffield, United Kingdom
| | - Martin Turner
- Molecular Biology and Biotechnology Department, The University of Sheffield, Sheffield, United Kingdom
| | - Phil Mitchell
- Molecular Biology and Biotechnology Department, The University of Sheffield, Sheffield, United Kingdom
- * E-mail:
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53
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Stuparevic I, Mosrin-Huaman C, Hervouet-Coste N, Remenaric M, Rahmouni AR. Cotranscriptional recruitment of RNA exosome cofactors Rrp47p and Mpp6p and two distinct Trf-Air-Mtr4 polyadenylation (TRAMP) complexes assists the exonuclease Rrp6p in the targeting and degradation of an aberrant messenger ribonucleoprotein particle (mRNP) in yeast. J Biol Chem 2013; 288:31816-29. [PMID: 24047896 DOI: 10.1074/jbc.m113.491290] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The cotranscriptional mRNA processing and packaging reactions that lead to the formation of export-competent messenger ribonucleoprotein particles (mRNPs) are under the surveillance of quality control steps. Aberrant mRNPs resulting from faulty events are retained in the nucleus with ensuing elimination of their mRNA component. The molecular mechanisms by which the surveillance system recognizes defective mRNPs and stimulates their destruction by the RNA degradation machinery are still not completely elucidated. Using an experimental approach in which mRNP formation in yeast is disturbed by the action of the bacterial Rho helicase, we have shown previously that the targeting of Rho-induced aberrant mRNPs is mediated by Rrp6p, which is recruited cotranscriptionally in association with Nrd1p following Rho action. Here we investigated the specific involvement in this quality control process of different cofactors associated with the nuclear RNA degradation machinery. We show that, in addition to the main hydrolytic action of the exonuclease Rrp6p, the cofactors Rrp47p, Mpp6p as well as the Trf-Air-Mtr4 polyadenylation (TRAMP) components Trf4p, Trf5p, and Air2p contribute significantly by stimulating the degradation process upon their cotranscriptional recruitment. Trf4p and Trf5p are apparently recruited in two distinct TRAMP complexes that both contain Air2p as component. Surprisingly, Rrp47p appears to play an important role in mutual protein stabilization with Rrp6p, which highlights a close association between the two partners. Together, our results provide an integrated view of how different cofactors of the RNA degradation machinery cooperate to target and eliminate aberrant mRNPs.
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Affiliation(s)
- Igor Stuparevic
- From the Centre de Biophysique Moléculaire, Unité Propre de Recherche (UPR) 4301 du CNRS, rue Charles Sadron, 45071 Orléans, France
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54
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The RNA exosome and proteasome: common principles of degradation control. Nat Rev Mol Cell Biol 2013; 14:654-60. [PMID: 23989960 DOI: 10.1038/nrm3657] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Defective RNAs and proteins are swiftly degraded by cellular quality control mechanisms. A large fraction of their degradation is mediated by the exosome and the proteasome. These complexes have a similar architectural framework based on cylindrical, hollow structures that are conserved from bacteria and archaea to eukaryotes. Mechanistic similarities have also been identified for how RNAs and proteins are channelled into these structures and prepared for degradation. Insights gained from studies of the proteasome should now set the stage for elucidating the regulation, assembly and small-molecule inhibition of the exosome.
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55
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Goring ME, Leibovitch M, Gea-Mallorqui E, Karls S, Richard F, Hanic-Joyce PJ, Joyce PBM. The ability of an arginine to tryptophan substitution in Saccharomyces cerevisiae tRNA nucleotidyltransferase to alleviate a temperature-sensitive phenotype suggests a role for motif C in active site organization. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2097-106. [PMID: 23872483 DOI: 10.1016/j.bbapap.2013.07.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 07/08/2013] [Accepted: 07/10/2013] [Indexed: 11/15/2022]
Abstract
We report that the temperature-sensitive (ts) phenotype in Saccharomyces cerevisiae associated with a variant tRNA nucleotidyltransferase containing an amino acid substitution at position 189 results from a reduced ability to incorporate AMP and CMP into tRNAs. We show that this defect can be compensated for by a second-site suppressor converting residue arginine 64 to tryptophan. The R64W substitution does not alter the structure or thermal stability of the enzyme dramatically but restores catalytic activity in vitro and suppresses the ts phenotype in vivo. R64 is found in motif A known to be involved in catalysis and nucleotide triphosphate binding while E189 lies within motif C previously thought only to connect the head and neck domains of the protein. Although mutagenesis experiments indicate that residues R64 and E189 do not interact directly, our data suggest a critical role for residue E189 in enzyme structure and function. Both R64 and E189 may contribute to the organization of the catalytic domain of the enzyme. These results, along with overexpression and deletion analyses, show that the ts phenotype of cca1-E189F does not arise from thermal instability of the variant tRNA nucleotidyltransferase but instead from the inability of a partially active enzyme to support growth only at higher temperatures.
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Affiliation(s)
- Mark E Goring
- Department of Biology, Concordia University, Montréal, H4B 1R6, Canada
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Coy S, Volanakis A, Shah S, Vasiljeva L. The Sm complex is required for the processing of non-coding RNAs by the exosome. PLoS One 2013; 8:e65606. [PMID: 23755256 PMCID: PMC3675052 DOI: 10.1371/journal.pone.0065606] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 04/27/2013] [Indexed: 12/25/2022] Open
Abstract
A key question in the field of RNA regulation is how some exosome substrates, such as spliceosomal snRNAs and telomerase RNA, evade degradation and are processed into stable, functional RNA molecules. Typical feature of these non-coding RNAs is presence of the Sm complex at the 3′end of the mature RNA molecule. Here, we report that in Saccharomyces cerevisiae presence of intact Sm binding site is required for the exosome-mediated processing of telomerase RNA from a polyadenylated precursor into its mature form and is essential for its function in elongating telomeres. Additionally, we demonstrate that the same pathway is involved in the maturation of snRNAs. Furthermore, the insertion of an Sm binding site into an unstable RNA that is normally completely destroyed by the exosome, leads to its partial stabilization. We also show that telomerase RNA accumulates in Schizosaccharomyces pombe exosome mutants, suggesting a conserved role for the exosome in processing and degradation of telomerase RNA. In summary, our data provide important mechanistic insight into the regulation of exosome dependent RNA processing as well as telomerase RNA biogenesis.
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Affiliation(s)
- Sarah Coy
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Adam Volanakis
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Sneha Shah
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Lidia Vasiljeva
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- * E-mail:
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58
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Feigenbutz M, Jones R, Besong TMD, Harding SE, Mitchell P. Assembly of the yeast exoribonuclease Rrp6 with its associated cofactor Rrp47 occurs in the nucleus and is critical for the controlled expression of Rrp47. J Biol Chem 2013; 288:15959-70. [PMID: 23580640 PMCID: PMC3668751 DOI: 10.1074/jbc.m112.445759] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Rrp6 is a key catalytic subunit of the nuclear RNA exosome that plays a pivotal role in the processing, degradation, and quality control of a wide range of cellular RNAs. Here we report our findings on the assembly of the complex involving Rrp6 and its associated protein Rrp47, which is required for many Rrp6-mediated RNA processes. Recombinant Rrp47 is expressed as a non-globular homodimer. Analysis of the purified recombinant Rrp6·Rrp47 complex revealed a heterodimer, suggesting that Rrp47 undergoes a structural reconfiguration upon interaction with Rrp6. Studies using GFP fusion proteins show that Rrp6 and Rrp47 are localized to the yeast cell nucleus independently of one another. Consistent with this data, Rrp6, but not Rrp47, is found associated with the nuclear import adaptor protein Srp1. We show that the interaction with Rrp6 is critical for Rrp47 stability in vivo; in the absence of Rrp6, newly synthesized Rrp47 is rapidly degraded in a proteasome-dependent manner. These data resolve independent nuclear import routes for Rrp6 and Rrp47, reveal a structural reorganization of Rrp47 upon its interaction with Rrp6, and demonstrate a proteasome-dependent mechanism that efficiently suppresses the expression of Rrp47 in the absence of Rrp6.
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Affiliation(s)
- Monika Feigenbutz
- Molecular Biology and Biotechnology Department, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
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59
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Chlebowski A, Lubas M, Jensen TH, Dziembowski A. RNA decay machines: the exosome. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:552-60. [PMID: 23352926 DOI: 10.1016/j.bbagrm.2013.01.006] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 01/03/2013] [Indexed: 10/27/2022]
Abstract
The multisubunit RNA exosome complex is a major ribonuclease of eukaryotic cells that participates in the processing, quality control and degradation of virtually all classes of RNA in Eukaryota. All this is achieved by about a dozen proteins with only three ribonuclease activities between them. At first glance, the versatility of the pathways involving the exosome and the sheer multitude of its substrates are astounding. However, after fifteen years of research we have some understanding of how exosome activity is controlled and applied inside the cell. The catalytic properties of the eukaryotic exosome are fairly well described and attention is now drawn to how the interplay between these activities impacts cell physiology. Also, it has become evident that exosome function relies on many auxiliary factors, which are intensely studied themselves. In this way, the focus of exosome research is slowly leaving the test tube and moving back into the cell. The exosome also has an interesting evolutionary history, which is evident within the eukaryotic lineage but only fully appreciated when considering similar protein complexes found in Bacteria and Archaea. Thus, while we keep this review focused on the most comprehensively described yeast and human exosomes, we shall point out similarities or dissimilarities to prokaryotic complexes and proteins where appropriate. The article is divided into three parts. In Part One we describe how the exosome is built and how it manifests in cells of different organisms. In Part Two we detail the enzymatic properties of the exosome, especially recent data obtained for holocomplexes. Finally, Part Three presents an overview of the RNA metabolism pathways that involve the exosome. This article is part of a Special Issue entitled: RNA Decay mechanisms.
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60
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Abstract
Most RNAs in eukaryotic cells are produced as precursors that undergo processing at the 3' and/or 5' end to generate the mature transcript. In addition, many transcripts are degraded not only as part of normal recycling, but also when recognized as aberrant by the RNA surveillance machinery. The exosome, a conserved multiprotein complex containing two nucleases, is involved in both the 3' processing and the turnover of many RNAs in the cell. A series of factors, including the TRAMP (Trf4-Air2-Mtr4 polyadenylation) complex, Mpp6 and Rrp47, help to define the targets to be processed and/or degraded and assist in exosome function. The majority of the data on the exosome and RNA maturation/decay have been derived from work performed in the yeast Saccharomyces cerevisiae. In the present paper, we provide an overview of the exosome and its role in RNA processing/degradation and discuss important new insights into exosome composition and function in human cells.
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61
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Mistry DS, Chen Y, Sen GL. Progenitor function in self-renewing human epidermis is maintained by the exosome. Cell Stem Cell 2012; 11:127-35. [PMID: 22770246 DOI: 10.1016/j.stem.2012.04.022] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Revised: 03/22/2012] [Accepted: 04/24/2012] [Indexed: 01/25/2023]
Abstract
Stem and progenitor cells maintain the tissue they reside in for life by regulating the balance between proliferation and differentiation. How this is done is not well understood. Here, we report that the human exosome maintains progenitor cell function. The expression of several subunits of the exosome were found to be enriched in epidermal progenitor cells, which were required to retain proliferative capacity and to prevent premature differentiation. Loss of PM/Scl-75 also known as EXOSC9, a key subunit of the exosome complex, resulted in loss of cells from the progenitor cell compartment, premature differentiation, and loss of epidermal tissue. EXOSC9 promotes self-renewal and prevents premature differentiation by maintaining transcript levels of a transcription factor necessary for epidermal differentiation, GRHL3, at low levels through mRNA degradation. These data demonstrate that control of differentiation specific transcription factors through mRNA degradation is required for progenitor cell maintenance in mammalian tissue.
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Affiliation(s)
- Devendra S Mistry
- Division of Dermatology, Department of Medicine, Department of Cellular and Molecular Medicine, UCSD Stem Cell Program, University of California, San Diego, La Jolla, CA 92093-0869, USA
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62
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Larochelle M, Lemay JF, Bachand F. The THO complex cooperates with the nuclear RNA surveillance machinery to control small nucleolar RNA expression. Nucleic Acids Res 2012; 40:10240-53. [PMID: 22965128 PMCID: PMC3488260 DOI: 10.1093/nar/gks838] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
THO is a multi-protein complex that promotes coupling between transcription and mRNA processing. In contrast to its role in mRNA biogenesis, we show here that the fission yeast THO complex negatively controls the expression of non-coding small nucleolar (sno) RNAs. Accordingly, the deletion of genes encoding subunits of the evolutionarily conserved THO complex results in increased levels of mature snoRNAs. We also show physical and functional connections between THO and components of the TRAMP polyadenylation complex, whose loss of function also results in snoRNA accumulation. Consistent with a role in snoRNA expression, we demonstrate that THO and TRAMP complexes are recruited to snoRNA genes, and that a functional THO complex is required to maintain TRAMP occupancy at sites of snoRNA transcription. Our findings suggest that THO promotes exosome-mediated degradation of snoRNA precursors by ensuring the presence of the TRAMP complex at snoRNA genes. This study unveils an unexpected role for THO in the control of snoRNA expression and provides a new link between transcription and nuclear RNA decay.
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Affiliation(s)
- Marc Larochelle
- Department of Biochemistry, RNA Group, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4
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63
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Schaeffer D, Reis FP, Johnson SJ, Arraiano CM, van Hoof A. The CR3 motif of Rrp44p is important for interaction with the core exosome and exosome function. Nucleic Acids Res 2012; 40:9298-307. [PMID: 22833611 PMCID: PMC3467083 DOI: 10.1093/nar/gks693] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The 10-subunit RNA exosome is involved in a large number of diverse RNA processing and degradation events in eukaryotes. These reactions are carried out by the single catalytic subunit, Rrp44p/Dis3p, which is composed of three parts that are conserved throughout eukaryotes. The exosome is named for the 3' to 5' exoribonuclease activity provided by a large C-terminal region of the Rrp44p subunit that resembles other exoribonucleases. Rrp44p also contains an endoribonuclease domain. Finally, the very N-terminus of Rrp44p contains three Cys residues (CR3 motif) that are conserved in many eukaryotes but have no known function. These three conserved Cys residues cluster with a previously unrecognized conserved His residue in what resembles a metal-ion-binding site. Genetic and biochemical data show that this CR3 motif affects both endo- and exonuclease activity in vivo and both the nuclear and cytoplasmic exosome, as well as the ability of Rrp44p to associate with the other exosome subunits. These data provide the first direct evidence that the exosome-Rrp44p interaction is functionally important and also provides a molecular explanation for the functional defects when the conserved Cys residues are mutated.
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Affiliation(s)
- Daneen Schaeffer
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, Houston, TX 77030, USA
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64
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Abstract
All RNA species in yeast cells are subject to turnover. Work over the past 20 years has defined degradation mechanisms for messenger RNAs, transfer RNAs, ribosomal RNAs, and noncoding RNAs. In addition, numerous quality control mechanisms that target aberrant RNAs have been identified. Generally, each decay mechanism contains factors that funnel RNA substrates to abundant exo- and/or endonucleases. Key issues for future work include determining the mechanisms that control the specificity of RNA degradation and how RNA degradation processes interact with translation, RNA transport, and other cellular processes.
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Affiliation(s)
- Roy Parker
- Department of Molecular and Cellular Biology, University of Arizona and Howard Hughes Medical Institute, Tucson, AZ 85721, USA.
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65
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Berndt H, Harnisch C, Rammelt C, Stöhr N, Zirkel A, Dohm JC, Himmelbauer H, Tavanez JP, Hüttelmaier S, Wahle E. Maturation of mammalian H/ACA box snoRNAs: PAPD5-dependent adenylation and PARN-dependent trimming. RNA (NEW YORK, N.Y.) 2012; 18:958-72. [PMID: 22442037 PMCID: PMC3334704 DOI: 10.1261/rna.032292.112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 02/14/2012] [Indexed: 05/17/2023]
Abstract
Small nucleolar and small Cajal body RNAs (snoRNAs and scaRNAs) of the H/ACA box and C/D box type are generated by exonucleolytic shortening of longer precursors. Removal of the last few nucleotides at the 3' end is known to be a distinct step. We report that, in human cells, knock-down of the poly(A) specific ribonuclease (PARN), previously implicated only in mRNA metabolism, causes the accumulation of oligoadenylated processing intermediates of H/ACA box but not C/D box RNAs. In agreement with a role of PARN in snoRNA and scaRNA processing, the enzyme is concentrated in nucleoli and Cajal bodies. Oligo(A) tails are attached to a short stub of intron sequence remaining beyond the mature 3' end of the snoRNAs. The noncanonical poly(A) polymerase PAPD5 is responsible for addition of the oligo(A) tails. We suggest that deadenylation is coupled to clean 3' end trimming, which might serve to enhance snoRNA stability.
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Affiliation(s)
- Heike Berndt
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
| | - Christiane Harnisch
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
| | - Christiane Rammelt
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
| | - Nadine Stöhr
- Section for Molecular Cell Biology, Department of Medicine, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
| | - Anne Zirkel
- Section for Molecular Cell Biology, Department of Medicine, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
| | - Juliane C. Dohm
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
- Centre for Genomic Regulation (CRG) and UPF, 08003 Barcelona, Spain
| | | | - Joao-Paulo Tavanez
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Stefan Hüttelmaier
- Section for Molecular Cell Biology, Department of Medicine, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
| | - Elmar Wahle
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
- Corresponding author.E-mail .
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Gupta AK, Panigrahi SK, Bhattacharya A, Bhattacharya S. Self-circularizing 5'-ETS RNAs accumulate along with unprocessed pre ribosomal RNAs in growth-stressed Entamoeba histolytica. Sci Rep 2012; 2:303. [PMID: 22396851 PMCID: PMC3294279 DOI: 10.1038/srep00303] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 02/15/2012] [Indexed: 01/13/2023] Open
Abstract
The primary transcript of rRNA genes is a large pre rRNA which is precisely processed to release the mature rRNAs. The 5'-external transcribed spacer (ETS) of rRNA genes contains important sites for pre rRNA processing. Once the processing is accomplished the ETS is rapidly degraded. We show that in growth-stressed cells of the human parasitic protist Entamoeba histolytica the A'-A(0) sub-fragment of the 5'-ETS accumulates to high levels as a family of RNA molecules of size 666 to 912 nt. These etsRNAs are circular in vivo and can spontaneously self-circularize in vitro. The accumulation of etsRNAs is accompanied by accumulation of unprocessed pre rRNA, indicating a possible role of etsRNAs in inhibition of processing during growth stress. Our data shows for the first time that processed etsRNA is not a mere by-product destined for degradation but is stabilized by circularization and could play a regulatory role as noncoding RNA.
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67
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Bernstein J, Toth EA. Yeast nuclear RNA processing. World J Biol Chem 2012; 3:7-26. [PMID: 22312453 PMCID: PMC3272586 DOI: 10.4331/wjbc.v3.i1.7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2011] [Revised: 11/27/2011] [Accepted: 12/04/2011] [Indexed: 02/05/2023] Open
Abstract
Nuclear RNA processing requires dynamic and intricately regulated machinery composed of multiple enzymes and their cofactors. In this review, we summarize recent experiments using Saccharomyces cerevisiae as a model system that have yielded important insights regarding the conversion of pre-RNAs to functional RNAs, and the elimination of aberrant RNAs and unneeded intermediates from the nuclear RNA pool. Much progress has been made recently in describing the 3D structure of many elements of the nuclear degradation machinery and its cofactors. Similarly, the regulatory mechanisms that govern RNA processing are gradually coming into focus. Such advances invariably generate many new questions, which we highlight in this review.
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Affiliation(s)
- Jade Bernstein
- Jade Bernstein, Eric A Toth, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, United States
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68
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Lubas M, Chlebowski A, Dziembowski A, Jensen TH. Biochemistry and Function of RNA Exosomes. EUKARYOTIC RNASES AND THEIR PARTNERS IN RNA DEGRADATION AND BIOGENESIS, PART A 2012; 31:1-30. [DOI: 10.1016/b978-0-12-404740-2.00001-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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69
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Plant Exosomes and Cofactors. EUKARYOTIC RNASES AND THEIR PARTNERS IN RNA DEGRADATION AND BIOGENESIS, PART A 2012; 31:31-52. [DOI: 10.1016/b978-0-12-404740-2.00002-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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70
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Interaction profiling identifies the human nuclear exosome targeting complex. Mol Cell 2011; 43:624-37. [PMID: 21855801 DOI: 10.1016/j.molcel.2011.06.028] [Citation(s) in RCA: 309] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 06/13/2011] [Accepted: 06/28/2011] [Indexed: 11/20/2022]
Abstract
The RNA exosome is a conserved degradation machinery, which obtains full activity only when associated with cofactors. The most prominent activator of the yeast nuclear exosome is the RNA helicase Mtr4p, acting in the context of the Trf4p/Air2p/Mtr4p polyadenylation (TRAMP) complex. The existence of a similar activator(s) in humans remains elusive. By establishing an interaction network of the human nuclear exosome, we identify the trimeric Nuclear Exosome Targeting (NEXT) complex, containing hMTR4, the Zn-knuckle protein ZCCHC8, and the putative RNA binding protein RBM7. ZCCHC8 and RBM7 are excluded from nucleoli, and consistently NEXT is specifically required for the exosomal degradation of promoter upstream transcripts (PROMPTs). We also detect putative homolog TRAMP subunits hTRF4-2 (Trf4p) and ZCCHC7 (Air2p) in hRRP6 and hMTR4 precipitates. However, at least ZCCHC7 function is restricted to nucleoli. Our results suggest that human nuclear exosome degradation pathways comprise modules of spatially organized cofactors that diverge from the yeast model.
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Smith SB, Kiss DL, Turk E, Tartakoff AM, Andrulis ED. Pronounced and extensive microtubule defects in a Saccharomyces cerevisiae DIS3 mutant. Yeast 2011; 28:755-69. [PMID: 21919057 DOI: 10.1002/yea.1899] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/21/2011] [Accepted: 07/10/2011] [Indexed: 11/05/2022] Open
Abstract
Subunits of the RNA processing exosome assemble into structurally distinct protein complexes that function in disparate cellular compartments and RNA metabolic pathways. Here, in a genetic, cell biological and transcriptomic analysis, we examined the role of Dis3, an essential polypeptide with endo- and 3'→5' exo-ribonuclease activity, in cell cycle progression. We present several lines of evidence that perturbation of DIS3 affects microtubule (MT) localization and structure in Saccharomyces cerevisiae. Cells with a DIS3 mutant: (a) accumulate anaphase and pre-anaphase mitotic spindles; (b) exhibit spindles that are misorientated and displaced from the bud neck; (c) harbour elongated spindle-associated astral MTs; (d) have an increased G1 astral MT length and number; and (e) are hypersensitive to MT poisons. Mutations in the core exosome genes RRP4 and MTR3 and the exosome cofactor gene MTR4, but not other exosome subunit gene mutants, also elicit MT phenotypes. RNA deep sequencing analysis (RNA-seq) shows broad changes in the levels of cell cycle- and MT-related transcripts in mutant strains. Collectively, the data presented in this study suggest an evolutionarily conserved role for Dis3 in linking RNA metabolism, MTs and cell cycle progression.
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Affiliation(s)
- Sarah B Smith
- Department of Molecular Biology and Microbiology, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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72
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Januszyk K, Liu Q, Lima CD. Activities of human RRP6 and structure of the human RRP6 catalytic domain. RNA (NEW YORK, N.Y.) 2011; 17:1566-77. [PMID: 21705430 PMCID: PMC3153979 DOI: 10.1261/rna.2763111] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 05/19/2011] [Indexed: 05/24/2023]
Abstract
The eukaryotic RNA exosome is a highly conserved multi-subunit complex that catalyzes degradation and processing of coding and noncoding RNA. A noncatalytic nine-subunit exosome core interacts with Rrp44 and Rrp6, two subunits that possess processive and distributive 3'-to-5' exoribonuclease activity, respectively. While both Rrp6 and Rrp44 are responsible for RNA processing in budding yeast, Rrp6 may play a more prominent role in processing, as it has been demonstrated to be inhibited by stable RNA secondary structure in vitro and because the null allele in budding yeast leads to the buildup of specific structured RNA substrates. Human RRP6, otherwise known as PM/SCL-100 or EXOSC10, shares sequence similarity to budding yeast Rrp6 and is proposed to catalyze 3'-to-5' exoribonuclease activity on a variety of nuclear transcripts including ribosomal RNA subunits, RNA that has been poly-adenylated by TRAMP, as well as other nuclear RNA transcripts destined for processing and/or destruction. To characterize human RRP6, we expressed the full-length enzyme as well as truncation mutants that retain catalytic activity, compared their activities to analogous constructs for Saccharomyces cerevisiae Rrp6, and determined the X-ray structure of a human construct containing the exoribonuclease and HRDC domains that retains catalytic activity. Structural data show that the human active site is more exposed when compared to the yeast structure, and biochemical data suggest that this feature may play a role in the ability of human RRP6 to productively engage and degrade structured RNA substrates more effectively than the analogous budding yeast enzyme.
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Affiliation(s)
- Kurt Januszyk
- Structural Biology Program, Sloan-Kettering Institute, New York, New York 10065, USA
| | - Quansheng Liu
- Structural Biology Program, Sloan-Kettering Institute, New York, New York 10065, USA
| | - Christopher D. Lima
- Structural Biology Program, Sloan-Kettering Institute, New York, New York 10065, USA
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73
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Santos MCT, Goldfeder MB, Zanchin NIT, Oliveira CC. The essential nucleolar yeast protein Nop8p controls the exosome function during 60S ribosomal subunit maturation. PLoS One 2011; 6:e21686. [PMID: 21747919 PMCID: PMC3126838 DOI: 10.1371/journal.pone.0021686] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 06/08/2011] [Indexed: 11/19/2022] Open
Abstract
The yeast nucleolar protein Nop8p has previously been shown to interact with Nip7p and to be required for 60S ribosomal subunit formation. Although depletion of Nop8p in yeast cells leads to premature degradation of rRNAs, the biochemical mechanism responsible for this phenotype is still not known. In this work, we show that the Nop8p amino-terminal region mediates interaction with the 5.8S rRNA, while its carboxyl-terminal portion interacts with Nip7p and can partially complement the growth defect of the conditional mutant strain Δnop8/GAL::NOP8. Interestingly, Nop8p mediates association of Nip7p to pre-ribosomal particles. Nop8p also interacts with the exosome subunit Rrp6p and inhibits the complex activity in vitro, suggesting that the decrease in 60S ribosomal subunit levels detected upon depletion of Nop8p may result from degradation of pre-rRNAs by the exosome. These results strongly indicate that Nop8p may control the exosome function during pre-rRNA processing.
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Affiliation(s)
- Marcia C. T. Santos
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Mauricio B. Goldfeder
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Nilson I. T. Zanchin
- Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas, São Paulo, Brazil
- Faculdade de Ciências Aplicadas, Universidade Estadual de Campinas, Limeira, São Paulo, Brazil
| | - Carla C. Oliveira
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
- * E-mail:
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74
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Costello JL, Stead JA, Feigenbutz M, Jones RM, Mitchell P. The C-terminal region of the exosome-associated protein Rrp47 is specifically required for box C/D small nucleolar RNA 3'-maturation. J Biol Chem 2010; 286:4535-43. [PMID: 21135092 PMCID: PMC3039359 DOI: 10.1074/jbc.m110.162826] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Cells lacking the exosome-associated protein Rrp47 show similar defects in stable RNA processing to those observed in the absence of the catalytic subunit Rrp6, but the precise mechanism(s) by which Rrp47 functions together with Rrp6 remains unclear. Deletion complementation analyses defined an N-terminal region of Rrp47, largely coincident with the bioinformatically defined Sas10/C1D domain, which was sufficient for protein function in vivo. In vitro protein interaction studies demonstrated that this domain of Rrp47 binds the PMC2NT domain of Rrp6. Expression of the N-terminal domain of Rrp47 in yeast complemented most RNA-processing defects associated with the rrp47Δ mutant but failed to complement the defect observed in 3′-end maturation of box C/D small nucleolar RNAs. Consistent with these results, protein capture assays revealed an interaction between the C-terminal region of Rrp47 and the small nucleolar ribonucleoproteins Nop56 and Nop58. Filter binding assays demonstrated that deletion of the lysine-rich sequence at the C terminus of Rrp47 blocked RNA binding in vitro. Furthermore, a protein mutated both at the C terminus and within the N-terminal domain showed a synergistic defect in RNA binding without impacting on its ability to interact with Rrp6. These studies provide evidence for a role of Rrp47 in registering a small nucleolar ribonucleoprotein particle assembly, functionally characterize the Sas10/C1D domain of Rrp47, and show that both the C terminus of Rrp47 and the N-terminal domain contribute to its RNA-binding activity.
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Affiliation(s)
- Joe L Costello
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
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75
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Abstract
The Sas10/C1D domain is found in a small group of eukaryotic proteins that have functions in RNA processing events, translational control and DNA repair mechanisms. The domain is predicted to be alpha-helical in nature and comprises approx. 80 amino acid residues. Whereas the Sas10/C1D domain has yet to be functionally characterized, available results suggest that this domain forms a binding surface for specific interactions with other proteins and can concomitantly interact with RNA or DNA. This property of the Sas10/C1D domain may facilitate this family of proteins to dock other proteins on to nucleic acid substrates.
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76
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Slomovic S, Schuster G. Exonucleases and endonucleases involved in polyadenylation-assisted RNA decay. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 2:106-23. [PMID: 21956972 DOI: 10.1002/wrna.45] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
RNA polyadenylation occurs in most forms of life, excluding a small number of biological systems. This posttranscriptional modification undertakes two roles, both of which influence the stability of the polyadenylated transcript. One is associated with the mature 3' ends of nucleus-encoded mRNAs in eukaryotic cells and is important for nuclear exit, translatability, and longevity. The second form of RNA polyadenylation assumes an almost opposite role; it is termed 'transient' and serves to mediate the degradation of RNA. Poly(A)-assisted RNA decay pathways were once thought to occur only in prokaryotes/organelles but are now known to be a common phenomenon, present in bacteria, organelles, archaea, and the nucleus and cytoplasm of eukaryotic cells, regardless of the fact that in some of these systems, stable polyadenylation exists as well. This article will summarize the current knowledge of polyadenylation and degradation factors involved in poly(A)-assisted RNA decay in the domains of life, focusing mainly on that which occurs in prokaryotes and organelles. In addition, it will offer an evolutionary view of the development of RNA polyadenylation and degradation and the cellular machinery that is involved.
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Affiliation(s)
- Shimyn Slomovic
- Faculty of Biology, Technion - Israel Institue of Technology, Haifa, Israel
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77
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Biological roles of translin and translin-associated factor-X: RNA metabolism comes to the fore. Biochem J 2010; 429:225-34. [PMID: 20578993 DOI: 10.1042/bj20100273] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Translin, and its binding partner protein TRAX (translin-associated factor-X) are a paralogous pair of conserved proteins, which have been implicated in a broad spectrum of biological activities, including cell growth regulation, mRNA processing, spermatogenesis, neuronal development/function, genome stability regulation and carcinogenesis, although their precise role in some of these processes remains unclear. Furthermore, translin (with or without TRAX) has nucleic-acid-binding activity and it is apparent that controlling nucleic acid metabolism and distribution are central to the biological role(s) of this protein and its partner TRAX. More recently, translin and TRAX have together been identified as enhancer components of an RNAi (RNA interference) pathway in at least one organism and this might provide critical insight into the biological roles of this enigmatic partnership. In the present review we discuss the biological and the biochemical properties of these proteins that indicate that they play a central and important role in eukaryotic cell biology.
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78
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Luz JS, Ramos CRR, Santos MCT, Coltri PP, Palhano FL, Foguel D, Zanchin NIT, Oliveira CC. Identification of archaeal proteins that affect the exosome function in vitro. BMC BIOCHEMISTRY 2010; 11:22. [PMID: 20507607 PMCID: PMC2890523 DOI: 10.1186/1471-2091-11-22] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 05/27/2010] [Indexed: 11/17/2022]
Abstract
Background The archaeal exosome is formed by a hexameric RNase PH ring and three RNA binding subunits and has been shown to bind and degrade RNA in vitro. Despite extensive studies on the eukaryotic exosome and on the proteins interacting with this complex, little information is yet available on the identification and function of archaeal exosome regulatory factors. Results Here, we show that the proteins PaSBDS and PaNip7, which bind preferentially to poly-A and AU-rich RNAs, respectively, affect the Pyrococcus abyssi exosome activity in vitro. PaSBDS inhibits slightly degradation of a poly-rA substrate, while PaNip7 strongly inhibits the degradation of poly-A and poly-AU by the exosome. The exosome inhibition by PaNip7 appears to depend at least partially on its interaction with RNA, since mutants of PaNip7 that no longer bind RNA, inhibit the exosome less strongly. We also show that FITC-labeled PaNip7 associates with the exosome in the absence of substrate RNA. Conclusions Given the high structural homology between the archaeal and eukaryotic proteins, the effect of archaeal Nip7 and SBDS on the exosome provides a model for an evolutionarily conserved exosome control mechanism.
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Affiliation(s)
- Juliana S Luz
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000, São Paulo, SP, Brazil
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79
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Mamolen M, Smith A, Andrulis ED. Drosophila melanogaster Dis3 N-terminal domains are required for ribonuclease activities, nuclear localization and exosome interactions. Nucleic Acids Res 2010; 38:5507-17. [PMID: 20421210 PMCID: PMC2938213 DOI: 10.1093/nar/gkq295] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Eukaryotic cells use numerous pathways to regulate RNA production, localization and stability. Several of these pathways are controlled by ribonucleases. The essential ribonuclease, Dis3, plays important roles in distinct RNA metabolic pathways. Despite much progress in understanding general characteristics of the Dis3 enzyme in vitro and in vivo, much less is known about the contributions of Dis3 domains to its activities, subcellular localization and protein–protein interactions. To address these gaps, we constructed a set of Drosophila melanogaster Dis3 (dDis3) mutants and assessed their enzymatic activity in vitro and their localizations and interactions in S2 tissue culture cells. We show that the dDis3 N-terminus is sufficient for endoribonuclease activity in vitro and that proper N-terminal domain structure is critical for activity of the full-length polypeptide. We find that the dDis3 N-terminus also contributes to its subcellular distribution, and is necessary and sufficient for interactions with core exosome proteins. Finally, dDis3 interaction with dRrp6 and dImportin-α3 is independent of core interactions and occurs though two different regions. Taken together, our data suggest that the dDis3 N-terminus is a dynamic and complex hub for RNA metabolism and exosome interactions.
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Affiliation(s)
- Megan Mamolen
- Department of Molecular Biology and Microbiology and Cell Biology Program, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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80
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Lemay JF, D'Amours A, Lemieux C, Lackner DH, St-Sauveur VG, Bähler J, Bachand F. The nuclear poly(A)-binding protein interacts with the exosome to promote synthesis of noncoding small nucleolar RNAs. Mol Cell 2010; 37:34-45. [PMID: 20129053 DOI: 10.1016/j.molcel.2009.12.019] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Revised: 08/11/2009] [Accepted: 11/09/2009] [Indexed: 11/19/2022]
Abstract
Poly(A)-binding proteins (PABPs) are important to eukaryotic gene expression. In the nucleus, the PABP PABPN1 is thought to function in polyadenylation of pre-mRNAs. Deletion of fission yeast pab2, the homolog of mammalian PABPN1, results in transcripts with markedly longer poly(A) tails, but the nature of the hyperadenylated transcripts and the mechanism that leads to RNA hyperadenylation remain unclear. Here we report that Pab2 functions in the synthesis of noncoding RNAs, contrary to the notion that PABPs function exclusively on protein-coding mRNAs. Accordingly, the absence of Pab2 leads to the accumulation of polyadenylated small nucleolar RNAs (snoRNAs). Our findings suggest that Pab2 promotes poly(A) tail trimming from pre-snoRNAs by recruiting the nuclear exosome. This work unveils a function for the nuclear PABP in snoRNA synthesis and provides insights into exosome recruitment to polyadenylated RNAs.
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Affiliation(s)
- Jean-François Lemay
- RNA Group, Department of Biochemistry, Université de Sherbrooke, Sherbrooke, QC JIH 5N4, Canada
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81
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Lu C, Ding F, Ke A. Crystal structure of the S. solfataricus archaeal exosome reveals conformational flexibility in the RNA-binding ring. PLoS One 2010; 5:e8739. [PMID: 20090900 PMCID: PMC2806925 DOI: 10.1371/journal.pone.0008739] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 12/18/2009] [Indexed: 11/18/2022] Open
Abstract
Background The exosome complex is an essential RNA 3′-end processing and degradation machinery. In archaeal organisms, the exosome consists of a catalytic ring and an RNA-binding ring, both of which were previously reported to assume three-fold symmetry. Methodology/Principal Findings Here we report an asymmetric 2.9 Å Sulfolobus solfataricus archaeal exosome structure in which the three-fold symmetry is broken due to combined rigid body and thermal motions mainly within the RNA-binding ring. Since increased conformational flexibility was also observed in the RNA-binding ring of the related bacterial PNPase, we speculate that this may reflect an evolutionarily conserved mechanism to accommodate diverse RNA substrates for degradation. Conclusion/Significance This study clearly shows the dynamic structures within the RNA-binding domains, which provides additional insights on mechanism of asymmetric RNA binding and processing.
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Affiliation(s)
- Changrui Lu
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Fang Ding
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Ailong Ke
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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82
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The Exosome and 3′–5′ RNA Degradation in Plants. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 702:50-62. [DOI: 10.1007/978-1-4419-7841-7_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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83
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Clayton C, Estevez A. The exosomes of trypanosomes and other protists. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 702:39-49. [PMID: 21713676 DOI: 10.1007/978-1-4419-7841-7_4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The archaeal exosome contains three heterodimeric RNase PH subunits, forming a hexamer with RNase activity; on top sits a trimer of two different SI domain proteins. In animals and yeast, six different, but related subunits form the RNase PH-like core, but these lack enzyme activity; there are three different Si-domain proteins and enzyme activity is provided by the endo/exonuc lease Rrp44 or-mainly in the nuclear exosome-the Rnase D enzyme Rrp6. Trypanosomes diverged from yeast and mammals very early in eukaryotic evolution. The trypanosome exosome is similar in subunit composition to the human exosome, but instead of being an optional component, trypanosome RRP6 is present in the nucleus and cytoplasm and is required for exosome stability. As in human cells and yeast, the trypanosome exosome has been shown to be required for processing and quality control of rRNA and to be involved in mRNA degradation. Electron microscopy results for a Leishmania exosome suggest that RRP6 is located on the side of the RnasePH ring, interacting with several exosome core proteins. Results of a search for exosome subunits in the genomes of widely diverged protists revealed varied exosome complexity; the Giardia exosome may be as simple as that of Archaea.
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Affiliation(s)
- Christine Clayton
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany,
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84
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Butler JS, Mitchell P. Rrp6, Rrp47 and Cofactors of the Nuclear Exosome. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 702:91-104. [DOI: 10.1007/978-1-4419-7841-7_8] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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85
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Azzouz N, Panasenko OO, Colau G, Collart MA. The CCR4-NOT complex physically and functionally interacts with TRAMP and the nuclear exosome. PLoS One 2009; 4:e6760. [PMID: 19707589 PMCID: PMC2727002 DOI: 10.1371/journal.pone.0006760] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Accepted: 07/14/2009] [Indexed: 01/14/2023] Open
Abstract
Background Ccr4-Not is a highly conserved multi-protein complex consisting in yeast of 9 subunits, including Not5 and the major yeast deadenylase Ccr4. It has been connected functionally in the nucleus to transcription by RNA polymerase II and in the cytoplasm to mRNA degradation. However, there has been no evidence so far that this complex is important for RNA degradation in the nucleus. Methodology/Principal Findings In this work we point to a new role for the Ccr4-Not complex in nuclear RNA metabolism. We determine the importance of the Ccr4-Not complex for the levels of non-coding nuclear RNAs, such as mis-processed and polyadenylated snoRNAs, whose turnover depends upon the nuclear exosome and TRAMP. Consistently, mutation of both the Ccr4-Not complex and the nuclear exosome results in synthetic slow growth phenotypes. We demonstrate physical interactions between the Ccr4-Not complex and the exosome. First, Not5 co-purifies with the exosome. Second, several exosome subunits co-purify with the Ccr4-Not complex. Third, the Ccr4-Not complex is important for the integrity of large exosome-containing complexes. Finally, we reveal a connection between the Ccr4-Not complex and TRAMP through the association of the Mtr4 helicase with the Ccr4-Not complex and the importance of specific subunits of Ccr4-Not for the association of Mtr4 with the nuclear exosome subunit Rrp6. Conclusions/Significance We propose a model in which the Ccr4-Not complex may provide a platform contributing to dynamic interactions between the nuclear exosome and its co-factor TRAMP. Our findings connect for the first time the different players involved in nuclear and cytoplasmic RNA degradation.
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Affiliation(s)
- Nowel Azzouz
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Olesya O. Panasenko
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Geoffroy Colau
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Martine A. Collart
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- * E-mail:
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86
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Lykke-Andersen S, Brodersen DE, Jensen TH. Origins and activities of the eukaryotic exosome. J Cell Sci 2009; 122:1487-94. [PMID: 19420235 DOI: 10.1242/jcs.047399] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The exosome is a multi-subunit 3'-5' exonucleolytic complex that is conserved in structure and function in all eukaryotes studied to date. The complex is present in both the nucleus and cytoplasm, where it continuously works to ensure adequate quantities and quality of RNAs by facilitating normal RNA processing and turnover, as well as by participating in more complex RNA quality-control mechanisms. Recent progress in the field has convincingly shown that the nucleolytic activity of the exosome is maintained by only two exonuclease co-factors, one of which is also an endonuclease. The additional association of the exosome with RNA-helicase and poly(A) polymerase activities results in a flexible molecular machine that is capable of dealing with the multitude of cellular RNA substrates that are found in eukaryotic cells. Interestingly, the same basic set of enzymatic activities is found in prokaryotic cells, which might therefore illustrate the evolutionary origin of the eukaryotic system. In this Commentary, we compare the structural and functional characteristics of the eukaryotic and prokaryotic RNA-degradation systems, with an emphasis on some of the functional networks in which the RNA exosome participates in eukaryotes.
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Affiliation(s)
- Søren Lykke-Andersen
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology, C. F. Møllers Allé 1130, University of Aarhus, DK-8000 Aarhus C, Denmark
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Hessle V, Björk P, Sokolowski M, González de Valdivia E, Silverstein R, Artemenko K, Tyagi A, Maddalo G, Ilag L, Helbig R, Zubarev RA, Visa N. The exosome associates cotranscriptionally with the nascent pre-mRNP through interactions with heterogeneous nuclear ribonucleoproteins. Mol Biol Cell 2009; 20:3459-70. [PMID: 19494042 DOI: 10.1091/mbc.e09-01-0079] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Eukaryotic cells have evolved quality control mechanisms to degrade aberrant mRNA molecules and prevent the synthesis of defective proteins that could be deleterious for the cell. The exosome, a protein complex with ribonuclease activity, is a key player in quality control. An early quality checkpoint takes place cotranscriptionally but little is known about the molecular mechanisms by which the exosome is recruited to the transcribed genes. Here we study the core exosome subunit Rrp4 in two insect model systems, Chironomus and Drosophila. We show that a significant fraction of Rrp4 is associated with the nascent pre-mRNPs and that a specific mRNA-binding protein, Hrp59/hnRNP M, interacts in vivo with multiple exosome subunits. Depletion of Hrp59 by RNA interference reduces the levels of Rrp4 at transcription sites, which suggests that Hrp59 is needed for the exosome to stably interact with nascent pre-mRNPs. Our results lead to a revised mechanistic model for cotranscriptional quality control in which the exosome is constantly recruited to newly synthesized RNAs through direct interactions with specific hnRNP proteins.
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Affiliation(s)
- Viktoria Hessle
- Department of Molecular Biology and Functional Genomics, Stockholm University, SE-10691 Stockholm, Sweden
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88
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Roth KM, Byam J, Fang F, Butler JS. Regulation of NAB2 mRNA 3'-end formation requires the core exosome and the Trf4p component of the TRAMP complex. RNA (NEW YORK, N.Y.) 2009; 15:1045-58. [PMID: 19369424 PMCID: PMC2685527 DOI: 10.1261/rna.709609] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The nuclear exosome functions in a variety of pathways catalyzing formation of mature RNA 3'-ends or the destruction of aberrant RNA transcripts. The RNA 3'-end formation activity of the exosome appeared restricted to small noncoding RNAs. However, the nuclear exosome controls the level of the mRNA encoding the poly(A)-binding protein Nab2p in a manner requiring an A(26) sequence in the mRNA 3' untranslated regions (UTR), and the activities of Nab2p and the exosome-associated exoribonuclease Rrp6p. Here we show that the A(26) sequence inhibits normal 3'-end processing of NAB2 mRNA in vivo and in vitro, and makes formation of the mature 3'-end dependent on trimming of the transcript by the core exosome and the Trf4p component of the TRAMP complex from a downstream site. The detection of mature, polyadenylated transcripts ending at, or within, the A(26) sequence indicates that exosome trimming sometimes gives way to polyadenylation of the mRNA. Alternatively, Rrp6p and the TRAMP-associated Mtr4p degrade these transcripts thereby limiting the amount of Nab2p in the cell. These findings suggest that NAB2 mRNA 3'-end formation requires the exosome and TRAMP complex, and that competition between polyadenylation and Rrp6p-dependent degradation controls the level of this mRNA.
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Affiliation(s)
- Kelly M Roth
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA
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89
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Anderson JT, Wang X. Nuclear RNA surveillance: no sign of substrates tailing off. Crit Rev Biochem Mol Biol 2009; 44:16-24. [PMID: 19280429 DOI: 10.1080/10409230802640218] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The production of cellular RNAs is tightly regulated to ensure gene expression is limited to appropriate times and locations. Elimination of RNA can be rapid and programmed to quickly terminate gene expression, or can be used to purge old, damaged or inappropriately formed RNAs. It is elimination of RNAs through the action of a polyadenylation complex (TRAMP), first described in the yeast Saccharomyces cerevisiae, which is the focus of this review. The discovery of TRAMP and presence of orthologs in most eukaryotes, along with an increasing number of potential TRAMP substrates in the form of new small non-coding RNAs, many of which emanate from areas of genomes once thought transcriptionally silent; promise to make this area of research of great interest for the foreseeable future.
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Affiliation(s)
- James T Anderson
- Department of Biological Sciences, Marquette University, Milwaukee, WI, USA.
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90
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Graham AC, Davis SM, Andrulis ED. Interdependent nucleocytoplasmic trafficking and interactions of Dis3 with Rrp6, the core exosome and importin-alpha3. Traffic 2009; 10:499-513. [PMID: 19220816 DOI: 10.1111/j.1600-0854.2009.00888.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Subcellular compartmentalization of exoribonucleases (RNAses) is an important control mechanism in the temporal and spatial regulation of RNA processing and decay. Despite much progress towards understanding RNAse substrates and functions, we know little of how RNAses are transported and assembled into functional, subcellularly restricted complexes. To gain insight into this issue, we are studying the exosome-binding protein Dis3, a processive 3' to 5' exoribonuclease. Here, we examine the interactions and subcellular localization of the Drosophila melanogaster Dis3 (dDis3) protein. N-terminal domain mutants of dDis3 abolish associations with the 'core' exosome, yet only reduce binding to the 'nuclear' exosome-associated factor dRrp6. We show that nuclear localization of dDis3 requires a C-terminal classic nuclear localization signal (NLS). Consistent with this, dDis3 specifically co-precipitates the NLS-binding protein importin-alpha3. Surprisingly, dDis3 constructs that lack or mutate the C-terminal NLS retain importin-alpha3 binding, suggesting that the interaction is indirect. Finally, we find that endogenous dDis3 and dRrp6 exhibit coordinated nuclear enrichment or exclusion, suggesting that dDis3, Rrp6 and importin-alpha3 interact in a complex independent of the core. We propose that the movement and deposition of this complex is important for the subcellular compartmentalization and regulation of the exosome core.
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Affiliation(s)
- Amy C Graham
- Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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91
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Schaeffer D, Meaux S, Clark A, van Hoof A. Determining in vivo activity of the yeast cytoplasmic exosome. Methods Enzymol 2009; 448:227-39. [PMID: 19111179 DOI: 10.1016/s0076-6879(08)02612-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
A 3'-exoribonuclease complex, termed the exosome, has important functions in the cytoplasm, as well as in the nucleus, and is involved in 3'-processing and/or decay of many RNAs. This chapter will discuss methods to study cytoplasmic exosome function in yeast with in vivo approaches. The first section will describe mutants that are available to study the processing or decay of a specific RNA by the nuclear or cytoplasmic exosome. The second section will discuss methods to determine whether the cytoplasmic exosome is functional under a specific condition(s) with reporter mRNAs that are known substrates of this complex.
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Affiliation(s)
- Daneen Schaeffer
- University of Texas Health Science Center-Houston, Department of Microbiology and Molecular Genetics, Houston, Texas, USA
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92
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Schneider C, Leung E, Brown J, Tollervey D. The N-terminal PIN domain of the exosome subunit Rrp44 harbors endonuclease activity and tethers Rrp44 to the yeast core exosome. Nucleic Acids Res 2009; 37:1127-40. [PMID: 19129231 PMCID: PMC2651783 DOI: 10.1093/nar/gkn1020] [Citation(s) in RCA: 175] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Nuclear and cytoplasmic forms of the yeast exosome share 10 components, of which only Rrp44/Dis3 is believed to possess 3′ exonuclease activity. We report that expression only of Rrp44 lacking 3′-exonuclease activity (Rrp44-exo) supports growth in S288c-related strains (BY4741). In BY4741, rrp44-exo was synthetic-lethal with loss of the cytoplasmic 5′-exonuclease Xrn1, indicating block of mRNA turnover, but not with loss of the nuclear 3′-exonuclease Rrp6. The RNA processing phenotype of rrp44-exo was milder than that seen on Rrp44 depletion, indicating that Rrp44-exo retains important functions. Recombinant Rrp44 was shown to possess manganese-dependent endonuclease activity in vitro that was abolished by four point mutations in the putative metal binding residues of its N-terminal PIN domain. Rrp44 lacking both exonuclease and endonuclease activity failed to support growth in strains depleted of endogenous Rrp44. Strains expressing Rrp44-exo and Rrp44-endo–exo exhibited different RNA processing patterns in vivo suggesting Rrp44-dependent endonucleolytic cleavages in the 5′-ETS and ITS2 regions of the pre-rRNA. Finally, the N-terminal PIN domain was shown to be necessary and sufficient for association with the core exosome, indicating its dual function as a nuclease and structural element.
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Affiliation(s)
- Claudia Schneider
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK
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93
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Grzechnik P, Kufel J. Polyadenylation linked to transcription termination directs the processing of snoRNA precursors in yeast. Mol Cell 2008; 32:247-58. [PMID: 18951092 PMCID: PMC2593888 DOI: 10.1016/j.molcel.2008.10.003] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 06/20/2008] [Accepted: 10/06/2008] [Indexed: 11/04/2022]
Abstract
Transcription termination by RNA polymerase II is coupled to transcript 3′ end formation. A large cleavage and polyadenylation complex containing the major poly(A) polymerase Pap1 produces mRNA 3′ ends, whereas those of nonpolyadenylated snoRNAs in yeast are formed either by endonucleolytic cleavage or by termination, followed by trimming by the nuclear exosome. We show that synthesis of independently transcribed snoRNAs involves default polyadenylation of two classes of precursors derived from termination at a main Nrd1/Nab3-dependent site or a “fail-safe” mRNA-like signal. Poly(A) tails are added by Pap1 to both forms, whereas the alternative poly(A) polymerase Tfr4 adenylates major precursors and processing intermediates to facilitate further polyadenylation by Pap1 and maturation by the exosome/Rrp6. A more important role of Trf4/TRAMP, however, is to enhance Nrd1 association with snoRNA genes. We propose a model in which polyadenylation of pre-snoRNAs is a key event linking their transcription termination, 3′ end processing, and degradation.
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Affiliation(s)
- Pawel Grzechnik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
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94
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Synowsky SA, van Wijk M, Raijmakers R, Heck AJR. Comparative multiplexed mass spectrometric analyses of endogenously expressed yeast nuclear and cytoplasmic exosomes. J Mol Biol 2008; 385:1300-13. [PMID: 19046973 DOI: 10.1016/j.jmb.2008.11.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 11/10/2008] [Accepted: 11/11/2008] [Indexed: 10/21/2022]
Abstract
Here we combined tandem affinity purification with several mass-spectrometry-based approaches to gain more insight into the composition and structure of the yeast nuclear-cytoplasmic exosome protein complex. The yeast exosome fulfills several different functions in RNA metabolism and can be localized in both the cytoplasm and the nucleus. These two exosome complexes differ in protein composition, although they share several constituents. We focused on these differences in composition by selecting a nuclear-specific exosome protein (Rrp6) and a cytoplasmic-specific protein (Ski7) as the tandem-affinity-purification-tagged affinity bait protein. First, we investigated both these purified exosome assemblies by macromolecular mass spectrometry (MS) to determine the stability and mass of the intact protein complexes and to obtain information on composition and core constituents. We used tandem MS on these intact protein complexes to further probe the composition and to obtain insight into the peripheral nature of some of the constituents. Finally, we combine stable isotope labeling with MS to quantitate differences in exosome composition and posttranslational modifications. We identified a few phosphorylation sites that are differentially regulated between the cytoplasmic exosome and the nuclear exosome. From all of these data, we conclude that the yeast nuclear exosome and the cytoplasmic exosome share a common stable core complex, but are decorated with quite a few differing peripheral proteins. We show that the nuclear exosome selectively copurifies with the alpha/beta importin heterodimer, which is known to be involved in the transport of proteins across the nuclear membrane.
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Affiliation(s)
- Silvia A Synowsky
- Biomolecular Mass Spectrometry and Proteomics Group, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
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95
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Hausmann S, Zheng S, Costanzo M, Brost RL, Garcin D, Boone C, Shuman S, Schwer B. Genetic and biochemical analysis of yeast and human cap trimethylguanosine synthase: functional overlap of 2,2,7-trimethylguanosine caps, small nuclear ribonucleoprotein components, pre-mRNA splicing factors, and RNA decay pathways. J Biol Chem 2008; 283:31706-18. [PMID: 18775984 PMCID: PMC2581544 DOI: 10.1074/jbc.m806127200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 09/04/2008] [Indexed: 12/26/2022] Open
Abstract
Trimethylguanosine synthase (Tgs1) is the enzyme that converts standard m(7)G caps to the 2,2,7-trimethylguanosine (TMG) caps characteristic of spliceosomal small nuclear RNAs. Fungi and mammalian somatic cells are able to grow in the absence of Tgs1 and TMG caps, suggesting that an essential function of the TMG cap might be obscured by functional redundancy. A systematic screen in budding yeast identified nonessential genes that, when deleted, caused synthetic growth defects with tgs1Delta. The Tgs1 interaction network embraced proteins implicated in small nuclear ribonucleoprotein function and spliceosome assembly, including Mud2, Nam8, Brr1, Lea1, Ist3, Isy1, Cwc21, and Bud13. Complementation of the synthetic lethality of mud2Delta tgs1Delta and nam8Delta tgs1Delta strains by wild-type TGS1, but not by catalytically defective mutants, indicated that the TMG cap is essential for mitotic growth when redundant splicing factors are missing. Our genetic analysis also highlighted synthetic interactions of Tgs1 with proteins implicated in RNA end processing and decay (Pat1, Lsm1, and Trf4) and regulation of polymerase II transcription (Rpn4, Spt3, Srb2, Soh1, Swr1, and Htz1). We find that the C-terminal domain of human Tgs1 can function in lieu of the yeast protein in vivo. We present a biochemical characterization of the human Tgs1 guanine-N2 methyltransferase reaction and identify individual amino acids required for methyltransferase activity in vitro and in vivo.
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Affiliation(s)
- Stéphane Hausmann
- Department of Microbiology and Molecular Medicine, University of Geneva, CH1211 Geneva, Switzerland.
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96
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Assenholt J, Mouaikel J, Andersen KR, Brodersen DE, Libri D, Jensen TH. Exonucleolysis is required for nuclear mRNA quality control in yeast THO mutants. RNA (NEW YORK, N.Y.) 2008; 14:2305-13. [PMID: 18824516 PMCID: PMC2578857 DOI: 10.1261/rna.1108008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Production of aberrant messenger ribonucleoprotein particles (mRNPs) is subject to quality control (QC). In yeast strains carrying mutations of the THO complex, transcription induction triggers a number of interconnected QC phenotypes: (1) rapid degradation of several mRNAs; (2) retention of a fraction of THO-dependent mRNAs in transcription site-associated foci; and (3) formation of a high molecular weight DNA/protein complex in the 3'-ends of THO target genes. Here, we demonstrate that the 3'-5' exonucleolytic domain of the nuclear exosome factor Rrp6p is necessary for establishing all QC phenotypes associated with THO mutations. The N terminus of Rrp6p is also important presumably through its binding to the Rrp6p co-factor Rrp47p. Interestingly, the 3'-5' exonucleolytic activity of Dis3p, the only other active exonuclease of the nuclear exosome, can also contribute to RNA QC in THO mutants, while other nuclear 3'-5' exonucleases cannot. Our data show that exonucleolytic attack by the nuclear exosome is needed both for provoking mRNP QC and for its ensuing elimination of faulty RNA.
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Affiliation(s)
- Jannie Assenholt
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology, The Faculty of Science, Aarhus University, DK-8000 Aarhus C, Denmark
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97
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Callahan KP, Butler JS. Evidence for core exosome independent function of the nuclear exoribonuclease Rrp6p. Nucleic Acids Res 2008; 36:6645-55. [PMID: 18940861 PMCID: PMC2588529 DOI: 10.1093/nar/gkn743] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The RNA exosome processes and degrades RNAs in archaeal and eukaryotic cells. Exosomes from yeast and humans contain two active exoribonuclease components, Rrp6p and Dis3p/Rrp44p. Rrp6p is concentrated in the nucleus and the dependence of its function on the nine-subunit core exosome and Dis3p remains unclear. We found that cells lacking Rrp6p accumulate poly(A)+ rRNA degradation intermediates distinct from those found in cells depleted of Dis3p, or the core exosome component Rrp43p. Depletion of Dis3p in the absence of Rrp6p causes a synergistic increase in the levels of degradation substrates common to the core exosome and Rrp6p, but has no effect on Rrp6p-specific substrates. Rrp6p lacking a portion of its C-terminal domain no longer co-purifies with the core exosome, but continues to carry out RNA 3'-end processing of 5.8S rRNA and snoRNAs, as well as the degradation of certain truncated Rrp6-specific rRNA intermediates. However, disruption of Rrp6p-core exosome interaction results in the inability of the cell to efficiently degrade certain poly(A)+ rRNA processing products that require the combined activities of Dis3p and Rrp6p. These findings indicate that Rrp6p may carry out some of its critical functions without physical association with the core exosome.
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Affiliation(s)
- Kevin P Callahan
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
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98
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Genome-based analysis of Chlamydomonas reinhardtii exoribonucleases and poly(A) polymerases predicts unexpected organellar and exosomal features. Genetics 2008; 179:125-36. [PMID: 18493045 DOI: 10.1534/genetics.107.086223] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Enzymes from several gene families modify RNA molecules at their extremities. These reactions occur in several cellular compartments and affect every class of RNA. To assess the diversity of a subclass of these enzymes, we searched Chlamydomonas for open reading frames (ORFs) potentially encoding exoribonucleases, poly(A) polymerases, and proteins known to associate with and/or regulate them. The ORFs were further analyzed for indications of protein localization to the nucleus, cytosol, mitochondrion, and/or chloroplast. By comparing predicted proteins with homologs in Arabidopsis and yeast, we derived several tentative conclusions regarding RNA 5'- and 3'-end metabolism in Chlamydomonas. First, the alga possesses only one each of the following likely organellar enzymes: polynucleotide phosphorylase, hydrolytic exoribonuclease, poly(A) polymerase, and CCA transferase, a surprisingly small complement. Second, although the core of the nuclear/cytosolic exosome decay complex is well conserved, neither nucleus-specific activators nor the cytosolic exosome activators are present. Finally, our discovery of nine noncanonical poly(A) polymerases, a divergent family retaining the catalytic domains of conventional poly(A) polymerases, leads to the hypothesis that polyadenylation may play an especially important regulatory role throughout the Chlamydomonas cell, stabilizing some transcripts and targeting degradation machinery to others.
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99
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Schmid M, Jensen TH. The exosome: a multipurpose RNA-decay machine. Trends Biochem Sci 2008; 33:501-10. [PMID: 18786828 DOI: 10.1016/j.tibs.2008.07.003] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 07/03/2008] [Accepted: 07/07/2008] [Indexed: 10/21/2022]
Abstract
The diversity of RNAs in the cell continues to amaze. In addition to the 'classic' species of mRNA, tRNA, rRNA, snRNA and snoRNA, it is now clear that the majority of genomic information is transcribed into RNA molecules. The resulting complexity of the transcriptome poses a serious challenge to cells because they must manage numerous RNA-processing reactions, yet, at the same time, eradicate surplus and aberrant material without destroying functional RNA. The 3'-->5' exonucleolytic RNA exosome is emerging as a major facilitator of such events. Recent structural and functional data regarding this fascinating complex and its many co-factors illuminate its diverse biochemical properties and indicate mechanisms by which RNAs are targeted for either processing or degradation.
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Affiliation(s)
- Manfred Schmid
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology, University of Aarhus, C.F. Møllers Alle, Bldg. 130, 8000 Aarhus C., Denmark
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100
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Granato DC, Machado-Santelli GM, Oliveira CC. Nop53p interacts with 5.8S rRNA co-transcriptionally, and regulates processing of pre-rRNA by the exosome. FEBS J 2008; 275:4164-78. [PMID: 18631361 DOI: 10.1111/j.1742-4658.2008.06565.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In eukaryotes, pre-rRNA processing depends on a large number of nonribosomal trans-acting factors that form intriguingly organized complexes. One of the early stages of pre-rRNA processing includes formation of the two intermediate complexes pre-40S and pre-60S, which then form the mature ribosome subunits. Each of these complexes contains specific pre-rRNAs, ribosomal proteins and processing factors. The yeast nucleolar protein Nop53p has previously been identified in the pre-60S complex and shown to affect pre-rRNA processing by directly binding to 5.8S rRNA, and to interact with Nop17p and Nip7p, which are also involved in this process. Here we show that Nop53p binds 5.8S rRNA co-transcriptionally through its N-terminal region, and that this protein portion can also partially complement growth of the conditional mutant strain Deltanop53/GAL::NOP53. Nop53p interacts with Rrp6p and activates the exosome in vitro. These results indicate that Nop53p may recruit the exosome to 7S pre-rRNA for processing. Consistent with this observation and similar to the observed in exosome mutants, depletion of Nop53p leads to accumulation of polyadenylated pre-rRNAs.
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Affiliation(s)
- Daniela C Granato
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, Brazil
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