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Régnier P, Hajnsdorf E. Poly(A)-assisted RNA decay and modulators of RNA stability. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 85:137-85. [PMID: 19215772 DOI: 10.1016/s0079-6603(08)00804-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In Escherichia coli, RNA degradation is orchestrated by the degradosome with the assistance of complementary pathways and regulatory cofactors described in this chapter. They control the stability of each transcript and regulate the expression of many genes involved in environmental adaptation. The poly(A)-dependent degradation machinery has diverse functions such as the degradation of decay intermediates generated by endoribonucleases, the control of the stability of regulatory non coding RNAs (ncRNAs) and the quality control of stable RNA. The metabolism of poly(A) and mechanism of poly(A)-assisted degradation are beginning to be understood. Regulatory factors, exemplified by RraA and RraB, control the decay rates of subsets of transcripts by binding to RNase E, in contrast to regulatory ncRNAs which, assisted by Hfq, target RNase E to specific transcripts. Destabilization is often consecutive to the translational inactivation of mRNA. However, there are examples where RNA degradation is the primary regulatory step.
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Affiliation(s)
- Philippe Régnier
- CNRS UPR9073, Institut de Biologie Physico-Chimique, Paris, France
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52
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Chapter 1 A Phylogenetic View of Bacterial Ribonucleases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 85:1-41. [DOI: 10.1016/s0079-6603(08)00801-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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53
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Schaeffer D, Tsanova B, Barbas A, Reis FP, Dastidar EG, Sanchez-Rotunno M, Arraiano CM, van Hoof A. The exosome contains domains with specific endoribonuclease, exoribonuclease and cytoplasmic mRNA decay activities. Nat Struct Mol Biol 2009; 16:56-62. [PMID: 19060898 PMCID: PMC2615074 DOI: 10.1038/nsmb.1528] [Citation(s) in RCA: 226] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Accepted: 11/13/2008] [Indexed: 11/13/2022]
Abstract
The eukaryotic exosome is a ten-subunit 3' exoribonucleolytic complex responsible for many RNA-processing and RNA-degradation reactions. How the exosome accomplishes this is unknown. Rrp44 (also known as Dis3), a member of the RNase II family of enzymes, is the catalytic subunit of the exosome. We show that the PIN domain of Rrp44 has endoribonucleolytic activity. The PIN domain is preferentially active toward RNA with a 5' phosphate, suggesting coordination of 5' and 3' processing. We also show that the endonuclease activity is important in vivo. Furthermore, the essential exosome subunit Csl4 does not contain any domains that are required for viability, but its zinc-ribbon domain is required for exosome-mediated mRNA decay. These results suggest that specific exosome domains contribute to specific functions, and that different RNAs probably interact with the exosome differently. The combination of an endoRNase and an exoRNase activity seems to be a widespread feature of RNA-degrading machines.
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Affiliation(s)
- Daneen Schaeffer
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 6431 Fannin Street. MSB 1.212 Houston, TX 77030, USA
| | - Borislava Tsanova
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 6431 Fannin Street. MSB 1.212 Houston, TX 77030, USA
| | - Ana Barbas
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apt 127, 2781-901 Oeiras, Portugal
| | - Filipa Pereira Reis
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apt 127, 2781-901 Oeiras, Portugal
| | - Eeshita Ghosh Dastidar
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 6431 Fannin Street. MSB 1.212 Houston, TX 77030, USA
| | - Maya Sanchez-Rotunno
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 6431 Fannin Street. MSB 1.212 Houston, TX 77030, USA
| | - Cecilia Maria Arraiano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apt 127, 2781-901 Oeiras, Portugal
| | - Ambro van Hoof
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 6431 Fannin Street. MSB 1.212 Houston, TX 77030, USA
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54
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Andrade JM, Pobre V, Silva IJ, Domingues S, Arraiano CM. The role of 3'-5' exoribonucleases in RNA degradation. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 85:187-229. [PMID: 19215773 DOI: 10.1016/s0079-6603(08)00805-2] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
RNA degradation is a major process controlling RNA levels and plays a central role in cell metabolism. From the labile messenger RNA to the more stable noncoding RNAs (mostly rRNA and tRNA, but also the expanding class of small regulatory RNAs) all molecules are eventually degraded. Elimination of superfluous transcripts includes RNAs whose expression is no longer required, but also the removal of defective RNAs. Consequently, RNA degradation is an inherent step in RNA quality control mechanisms. Furthermore, it contributes to the recycling of the nucleotide pool in the cell. Escherichia coli has eight 3'-5' exoribonucleases, which are involved in multiple RNA metabolic pathways. However, only four exoribonucleases appear to accomplish all RNA degradative activities: polynucleotide phosphorylase (PNPase), ribonuclease II (RNase II), RNase R, and oligoribonuclease. Here, we summarize the available information on the role of bacterial 3'-5' exoribonucleases in the degradation of different substrates, highlighting the most recent data that have contributed to the understanding of the diverse modes of operation of these degradative enzymes.
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Affiliation(s)
- José M Andrade
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Qeiras, Portugal
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55
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Vincent HA, Deutscher MP. The roles of individual domains of RNase R in substrate binding and exoribonuclease activity. The nuclease domain is sufficient for digestion of structured RNA. J Biol Chem 2008; 284:486-494. [PMID: 19004832 DOI: 10.1074/jbc.m806468200] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RNase R and RNase II are the two representatives from the RNR family of processive, 3' to 5' exoribonucleases in Escherichia coli. Although RNase II is specific for single-stranded RNA, RNase R readily degrades through structured RNA. Furthermore, RNase R appears to be the only known 3' to 5' exoribonuclease that is able to degrade through double-stranded RNA without the aid of a helicase activity. Consequently, its functional domains and mechanism of action are of great interest. Using a series of truncated RNase R proteins we show that the cold-shock and S1 domains contribute to substrate binding. The cold-shock domains appear to play a role in substrate recruitment, whereas the S1 domain is most likely required to position substrates for efficient catalysis. Most importantly, the nuclease domain alone, devoid of the cold-shock and S1 domains, is sufficient for RNase R to bind and degrade structured RNAs. Moreover, this is a unique property of the nuclease domain of RNase R because this domain in RNase II stalls as it approaches a duplex. We also show that the nuclease domain of RNase R binds RNA more tightly than the nuclease domain of RNase II. This tighter binding may help to explain the difference in catalytic properties between RNase R and RNase II.
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Affiliation(s)
- Helen A Vincent
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, Florida 33101
| | - Murray P Deutscher
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, Florida 33101.
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56
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Barbas A, Matos RG, Amblar M, López-Viñas E, Gomez-Puertas P, Arraiano CM. New insights into the mechanism of RNA degradation by ribonuclease II: identification of the residue responsible for setting the RNase II end product. J Biol Chem 2008; 283:13070-6. [PMID: 18337246 DOI: 10.1074/jbc.m709989200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RNase II is a key exoribonuclease involved in the maturation, turnover, and quality control of RNA. RNase II homologues are components of the exosome, a complex of exoribonucleases. The structure of RNase II unraveled crucial aspects of the mechanism of RNA degradation. Here we show that mutations in highly conserved residues at the active site affect the activity of the enzyme. Moreover, we have identified the residue that is responsible for setting the end product of RNase II. In addition, we present for the first time the models of two members of the RNase II family, RNase R from Escherichia coli and human Rrp44, also called Dis3. Our findings improve the present model for RNA degradation by the RNase II family of enzymes.
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Affiliation(s)
- Ana Barbas
- Instituto de Tecnologia Química e Biológica/Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal
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57
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Andrade JM, Arraiano CM. PNPase is a key player in the regulation of small RNAs that control the expression of outer membrane proteins. RNA (NEW YORK, N.Y.) 2008; 14:543-51. [PMID: 18203924 PMCID: PMC2248267 DOI: 10.1261/rna.683308] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Accepted: 10/24/2007] [Indexed: 05/22/2023]
Abstract
In this report, we demonstrate that exonucleolytic turnover is much more important in the regulation of sRNA levels than was previously recognized. For the first time, PNPase is introduced as a major regulatory feature controlling the levels of the small noncoding RNAs MicA and RybB, which are required for the accurate expression of outer membrane proteins (OMPs). In the absence of PNPase, the pattern of OMPs is changed. In stationary phase, MicA RNA levels are increased in the PNPase mutant, leading to a decrease in the levels of its target ompA mRNA and the respective protein. This growth phase regulation represents a novel pathway of control. We have evaluated other ribonucleases in the control of MicA RNA, and we showed that degradation by PNPase surpasses the effect of endonucleolytic cleavages by RNase E. RybB was also destabilized by PNPase. This work highlights a new role for PNPase in the degradation of small noncoding RNAs and opens the way to evaluate striking similarities between bacteria and eukaryotes.
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Affiliation(s)
- José M Andrade
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal
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58
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Schneider C, Anderson JT, Tollervey D. The exosome subunit Rrp44 plays a direct role in RNA substrate recognition. Mol Cell 2007; 27:324-331. [PMID: 17643380 PMCID: PMC7610968 DOI: 10.1016/j.molcel.2007.06.006] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 04/12/2007] [Accepted: 06/06/2007] [Indexed: 10/23/2022]
Abstract
The exosome plays key roles in RNA maturation and surveillance, but it is unclear how target RNAs are identified. We report the functional characterization of the yeast exosome component Rrp44, a member of the RNase II family. Recombinant Rrp44 and the purified TRAMP polyadenylation complex each specifically recognized tRNA(i)(Met) lacking a single m(1)A(58) modification, even in the presence of a large excess of total tRNA. This tRNA is otherwise mature and functional in translation in vivo but is presumably subtly misfolded. Complete degradation of the hypomodified tRNA required both Rrp44 and the poly(A) polymerase activity of TRAMP. The intact exosome lacking only the catalytic activity of Rrp44 failed to degrade tRNA(i)(Met), showing this to be a specific Rrp44 substrate. Recognition of hypomodified tRNA(i)(Met) by Rrp44 is genetically separable from its catalytic activity on other substrates, with the mutations mapping to distinct regions of the protein.
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Affiliation(s)
- Claudia Schneider
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK
| | - James T Anderson
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA
| | - David Tollervey
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK.
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59
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Arraiano CM, Bamford J, Brüssow H, Carpousis AJ, Pelicic V, Pflüger K, Polard P, Vogel J. Recent advances in the expression, evolution, and dynamics of prokaryotic genomes. J Bacteriol 2007; 189:6093-100. [PMID: 17601780 PMCID: PMC1951890 DOI: 10.1128/jb.00612-07] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Cecilia M Arraiano
- ITQB-Instituto de Tecnologia Química e Biológical/Universidade Nova de Lisboa, Oeiras, Portugal
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60
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Mechold U, Fang G, Ngo S, Ogryzko V, Danchin A. YtqI from Bacillus subtilis has both oligoribonuclease and pAp-phosphatase activity. Nucleic Acids Res 2007; 35:4552-61. [PMID: 17586819 PMCID: PMC1935014 DOI: 10.1093/nar/gkm462] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Oligoribonuclease is the only RNase in Escherichia coli that is able to degrade RNA oligonucleotides five residues and shorter in length. Firmicutes including Bacillus subtilis do not have an Oligoribonuclease (Orn) homologous protein and it is not yet understood which proteins accomplish the equivalent function in these organisms. We had previously identified oligoribonucleases Orn from E. coli and its human homolog Sfn in a screen for proteins that are regulated by 3′-phosphoadenosine 5′-phosphate (pAp). Here, we identify YtqI as a potential functional analog of Orn through its interaction with pAp. YtqI degrades RNA oligonucleotides in vitro with preference for 3-mers. In addition, YtqI has pAp-phosphatase activity in vitro. In agreement with these data, YtqI is able to complement both orn and cysQ mutants in E. coli. An ytqI mutant in B. subtilis shows impairment of growth in the absence of cysteine, a phenotype resembling that of a cysQ mutant in E. coli. Phylogenetic distribution of YtqI, Orn and CysQ supports bifunctionality of YtqI.
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Affiliation(s)
- Undine Mechold
- Institut Pasteur, URA 2171, Unité de Génétique des Génomes Bactériens, 75724 Paris Cedex 15, France.
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61
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Amblar M, Barbas A, Gomez-Puertas P, Arraiano CM. The role of the S1 domain in exoribonucleolytic activity: substrate specificity and multimerization. RNA (NEW YORK, N.Y.) 2007; 13:317-27. [PMID: 17242308 PMCID: PMC1800512 DOI: 10.1261/rna.220407] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
RNase II is a 3'-5' exoribonuclease that processively hydrolyzes single-stranded RNA generating 5' mononucleotides. This enzyme contains a catalytic core that is surrounded by three RNA-binding domains. At its C terminus, there is a typical S1 domain that has been shown to be critical for RNA binding. The S1 domain is also present in the other major 3'-5' exoribonucleases from Escherichia coli: RNase R and polynucleotide phosphorylase (PNPase). In this report, we examined the involvement of the S1 domain in the different abilities of these three enzymes to overcome RNA secondary structures during degradation. Hybrid proteins were constructed by replacing the S1 domain of RNase II for the S1 from RNase R and PNPase, and their exonucleolytic activity and RNA-binding ability were examined. The results revealed that both the S1 domains of RNase R and PNPase are able to partially reverse the drop of RNA-binding ability and exonucleolytic activity resulting from removal of the S1 domain of RNase II. Moreover, the S1 domains investigated are not equivalent. Furthermore, we demonstrate that S1 is neither responsible for the ability to overcome secondary structures during RNA degradation, nor is it related to the size of the final product generated by each enzyme. In addition, we show that the S1 domain from PNPase is able to induce the trimerization of the RNaseII-PNP hybrid protein, indicating that this domain can have a role in the biogenesis of multimers.
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Affiliation(s)
- Mónica Amblar
- Instituto de Tecnologia Química e Biológica/Universidade Nova de Lisboa, Oeiras, Portugal
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62
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Chandran V, Poljak L, Vanzo NF, Leroy A, Miguel RN, Fernandez-Recio J, Parkinson J, Burns C, Carpousis AJ, Luisi BF. Recognition and cooperation between the ATP-dependent RNA helicase RhlB and ribonuclease RNase E. J Mol Biol 2006; 367:113-32. [PMID: 17234211 PMCID: PMC7610992 DOI: 10.1016/j.jmb.2006.12.014] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2006] [Revised: 11/26/2006] [Accepted: 12/07/2006] [Indexed: 12/21/2022]
Abstract
The Escherichia coli protein RhlB is an ATP-dependent motor that unfolds structured RNA for destruction by partner ribonucleases. In E. coli, and probably many other related gamma-proteobacteria, RhlB associates with the essential endoribonuclease RNase E as part of the multi-enzyme RNA degradosome assembly. The interaction with RNase E boosts RhlB's ATPase activity by an order of magnitude. Here, we examine the origins and implications of this effect. The location of the interaction sites on both RNase E and RhlB are refined and analysed using limited protease digestion, domain cross-linking and homology modelling. These data indicate that RhlB's carboxy-terminal RecA-like domain engages a segment of RNase E that is no greater than 64 residues. The interaction between RhlB and RNase E has two important consequences: first, the interaction itself stimulates the unwinding and ATPase activities of RhlB; second, RhlB gains proximity to two RNA-binding sites on RNase E, with which it cooperates to unwind RNA. Our homology model identifies a pattern of residues in RhlB that may be key for recognition of RNase E and which may communicate the activating effects. Our data also suggest that the association with RNase E may partially repress the RNA-binding activity of RhlB. This repression may in fact permit the interplay of the helicase and adjacent RNA binding segments as part of a process that steers substrates to either processing or destruction, depending on context, within the RNA degradosome assembly.
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Affiliation(s)
- Vidya Chandran
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
| | - Leonora Poljak
- Laboratoire de Microbiologie et Génétique Moléculaires, Unité Mixte de Recherche 5100, Centre National de la Recherche Scientifique et Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
| | - Nathalie F. Vanzo
- Laboratoire de Microbiologie et Génétique Moléculaires, Unité Mixte de Recherche 5100, Centre National de la Recherche Scientifique et Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
| | - Anne Leroy
- Laboratoire de Microbiologie et Génétique Moléculaires, Unité Mixte de Recherche 5100, Centre National de la Recherche Scientifique et Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
| | - Ricardo Núñez Miguel
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
| | - Juan Fernandez-Recio
- Molecular Modelling and Bioinformatics Unit, Institute of Biomedical Research, Parc Cientific de Barcelona (IRB-PCB), C/Josep Samitier 1–5, 08028 Barcelona, Spain
| | - James Parkinson
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
| | - Christopher Burns
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912, USA
| | - Agamemnon J. Carpousis
- Laboratoire de Microbiologie et Génétique Moléculaires, Unité Mixte de Recherche 5100, Centre National de la Recherche Scientifique et Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
- Corresponding authors: ;
| | - Ben F. Luisi
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
- Corresponding authors: ;
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63
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Grossman D, van Hoof A. RNase II structure completes group portrait of 3' exoribonucleases. Nat Struct Mol Biol 2006; 13:760-1. [PMID: 16955096 DOI: 10.1038/nsmb0906-760] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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64
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Frazão C, McVey CE, Amblar M, Barbas A, Vonrhein C, Arraiano CM, Carrondo MA. Unravelling the dynamics of RNA degradation by ribonuclease II and its RNA-bound complex. Nature 2006; 443:110-4. [PMID: 16957732 DOI: 10.1038/nature05080] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Accepted: 07/14/2006] [Indexed: 11/08/2022]
Abstract
RNA degradation is a determining factor in the control of gene expression. The maturation, turnover and quality control of RNA is performed by many different classes of ribonucleases. Ribonuclease II (RNase II) is a major exoribonuclease that intervenes in all of these fundamental processes; it can act independently or as a component of the exosome, an essential RNA-degrading multiprotein complex. RNase II-like enzymes are found in all three kingdoms of life, but there are no structural data for any of the proteins of this family. Here we report the X-ray crystallographic structures of both the ligand-free (at 2.44 A resolution) and RNA-bound (at 2.74 A resolution) forms of Escherichia coli RNase II. In contrast to sequence predictions, the structures show that RNase II is organized into four domains: two cold-shock domains, one RNB catalytic domain, which has an unprecedented alphabeta-fold, and one S1 domain. The enzyme establishes contacts with RNA in two distinct regions, the 'anchor' and the 'catalytic' regions, which act synergistically to provide catalysis. The active site is buried within the RNB catalytic domain, in a pocket formed by four conserved sequence motifs. The structure shows that the catalytic pocket is only accessible to single-stranded RNA, and explains the specificity for RNA versus DNA cleavage. It also explains the dynamic mechanism of RNA degradation by providing the structural basis for RNA translocation and enzyme processivity. We propose a reaction mechanism for exonucleolytic RNA degradation involving key conserved residues. Our three-dimensional model corroborates all existing biochemical data for RNase II, and elucidates the general basis for RNA degradation. Moreover, it reveals important structural features that can be extrapolated to other members of this family.
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Affiliation(s)
- Carlos Frazão
- Division of Biological Chemistry, ITQB-Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apt. 127, 2781-901 Oeiras, Portugal
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