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Vandanashree M, Singh AK, Gopal B. Characterization of RNase J. Methods Enzymol 2023; 692:177-215. [PMID: 37925179 DOI: 10.1016/bs.mie.2023.03.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2023]
Abstract
RNase J is involved in RNA maturation as well as degradation of RNA to the level of mononucleotides. This enzyme plays a vital role in maintaining intracellular RNA levels and governs different steps of the cellular metabolism in bacteria. RNase J is the first ribonuclease that was shown to have both endonuclease and 5'-3' exonuclease activity. RNase J enzymes can be identified by their characteristic sequence features and domain architecture. The quaternary structure of RNase J plays a role in regulating enzyme activity. The structure of RNase J has been characterized from several homologs. These reveal extensive overall structural similarity alongside a distinct active site topology that coordinates a metal cofactor. The metal cofactor is essential for catalytic activity. The catalytic activity of RNase J is influenced by oligomerization, the choice and stoichiometry of metal cofactors, and the 5' phosphorylation state of the RNA substrate. Here we describe the sequence and structural features of RNase J alongside phylogenetic analysis and reported functional roles in diverse organisms. We also provide a detailed purification strategy to obtain an RNase J enzyme sample with or without a metal cofactor. Different methods to identify the nature of the bound metal cofactor, the binding affinity and stoichiometry are presented. Finally, we describe enzyme assays to characterize RNase J using radioactive and fluorescence-based strategies with diverse RNA substrates.
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Affiliation(s)
- Muralidharan Vandanashree
- Molecular Biophysics Unit, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Ankur Kumar Singh
- Molecular Biophysics Unit, Division of Biological Sciences, Indian Institute of Science, Bangalore, India
| | - Balasubramanian Gopal
- Molecular Biophysics Unit, Division of Biological Sciences, Indian Institute of Science, Bangalore, India.
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2
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Ribonuclease J-Mediated mRNA Turnover Modulates Cell Shape, Metabolism and Virulence in Corynebacterium diphtheriae. Microorganisms 2021; 9:microorganisms9020389. [PMID: 33672886 PMCID: PMC7917786 DOI: 10.3390/microorganisms9020389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/08/2021] [Accepted: 02/09/2021] [Indexed: 01/16/2023] Open
Abstract
Controlled RNA degradation is a crucial process in bacterial cell biology for maintaining proper transcriptome homeostasis and adaptation to changing environments. mRNA turnover in many Gram-positive bacteria involves a specialized ribonuclease called RNase J (RnJ). To date, however, nothing is known about this process in the diphtheria-causative pathogen Corynebacterium diphtheriae, nor is known the identity of this ribonuclease in this organism. Here, we report that C. diphtheriae DIP1463 encodes a predicted RnJ homolog, comprised of a conserved N-terminal β-lactamase domain, followed by β-CASP and C-terminal domains. A recombinant protein encompassing the β-lactamase domain alone displays 5'-exoribonuclease activity, which is abolished by alanine-substitution of the conserved catalytic residues His186 and His188. Intriguingly, deletion of DIP1463/rnj in C. diphtheriae reduces bacterial growth and generates cell shape abnormality with markedly augmented cell width. Comparative RNA-seq analysis revealed that RnJ controls a large regulon encoding many factors predicted to be involved in biosynthesis, regulation, transport, and iron acquisition. One upregulated gene in the ∆rnj mutant is ftsH, coding for a membrane protease (FtsH) involved in cell division, whose overexpression in the wild-type strain also caused cell-width augmentation. Critically, the ∆rnj mutant is severely attenuated in virulence in a Caenorhabditis elegans model of infection, while the FtsH-overexpressing and toxin-less strains exhibit full virulence as the wild-type strain. Evidently, RNase J is a key ribonuclease in C. diphtheriae that post-transcriptionally influences the expression of numerous factors vital to corynebacterial cell physiology and virulence. Our findings have significant implications for basic biological processes and mechanisms of corynebacterial pathogenesis.
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3
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Raj R, Nadig S, Patel T, Gopal B. Structural and biochemical characteristics of two Staphylococcus epidermidis RNase J paralogs RNase J1 and RNase J2. J Biol Chem 2020; 295:16863-16876. [PMID: 32994223 PMCID: PMC7864078 DOI: 10.1074/jbc.ra120.014876] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 09/21/2020] [Indexed: 11/06/2022] Open
Abstract
RNase J enzymes are metallohydrolases that are involved in RNA maturation and RNA recycling, govern gene expression in bacteria, and catalyze both exonuclease and endonuclease activity. The catalytic activity of RNase J is regulated by multiple mechanisms which include oligomerization, conformational changes to aid substrate recognition, and the metal cofactor at the active site. However, little is known of how RNase J paralogs differ in expression and activity. Here we describe structural and biochemical features of two Staphylococcus epidermidis RNase J paralogs, RNase J1 and RNase J2. RNase J1 is a homodimer with exonuclease activity aided by two metal cofactors at the active site. RNase J2, on the other hand, has endonuclease activity and one metal ion at the active site and is predominantly a monomer. We note that the expression levels of these enzymes vary across Staphylococcal strains. Together, these observations suggest that multiple interacting RNase J paralogs could provide a strategy for functional improvisation utilizing differences in intracellular concentration, quaternary structure, and distinct active site architecture despite overall structural similarity.
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Affiliation(s)
- Rishi Raj
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Savitha Nadig
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Twinkal Patel
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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4
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Li J, Hou Y, Gu X, Yue L, Guo L, Li D, Dong X. A newly identified duplex RNA unwinding activity of archaeal RNase J depends on processive exoribonucleolysis coupled steric occlusion by its structural archaeal loops. RNA Biol 2020; 17:1480-1491. [PMID: 32552320 DOI: 10.1080/15476286.2020.1777379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
RNase J is a prokaryotic 5'-3' exo/endoribonuclease that functions in mRNA decay and rRNA maturation. Here, we report a novel duplex unwinding activity of mpy-RNase J, an archaeal RNase J from Methanolobus psychrophilus, which enables it to degrade duplex RNAs with hairpins up to 40 bp when linking a 5' single-stranded overhangs of ≥ 7 nt, corresponding to the RNA channel length. A 6-nt RNA-mpy-RNase J-S247A structure reveals the RNA-interacting residues and a steric barrier at the RNA channel entrance comprising two archaeal loops and two helices. Mutagenesis of the residues key to either exoribonucleolysis or RNA translocation diminished the duplex unwinding activity. Substitution of the residues in the steric barrier yielded stalled degradation intermediates at the duplex RNA regions. Thus, an exoribonucleolysis-driven and steric occlusion-based duplex unwinding mechanism was identified. The duplex unwinding activity confers mpy-RNase J the capability of degrading highly structured RNAs, including the bacterial REP RNA, and archaeal mRNAs, rRNAs, tRNAs, SRPs, RNase P and CD-box RNAs, providing an indicative of the potential key roles of mpy-RNase J in pleiotropic RNA metabolisms. Hydrolysis-coupled duplex unwinding activity was also detected in a bacterial RNase J, which may use a shared but slightly different unwinding mechanism from archaeal RNase Js, indicating that duplex unwinding is a common property of the prokaryotic RNase Js.
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Affiliation(s)
- Jie Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences , Beijing, PR China.,Colleges of Life Sciences, University of Chinese Academy of Sciences , Beijing, China
| | - Yanjie Hou
- Institute of Biophysics, Chinese Academy of Sciences , Beijing, PR China
| | - Xien Gu
- School of Basic Medical Sciences, Hubei University of Medicine , Shiyan, China
| | - Lei Yue
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences , Beijing, PR China.,Colleges of Life Sciences, University of Chinese Academy of Sciences , Beijing, China
| | - Lu Guo
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences , Beijing, PR China
| | - Defeng Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences , Beijing, PR China.,Colleges of Life Sciences, University of Chinese Academy of Sciences , Beijing, China
| | - Xiuzhu Dong
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences , Beijing, PR China.,Colleges of Life Sciences, University of Chinese Academy of Sciences , Beijing, China
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5
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Marx P, Sang Y, Qin H, Wang Q, Guo R, Pfeifer C, Kreth J, Merritt J. Environmental stress perception activates structural remodeling of extant Streptococcus mutans biofilms. NPJ Biofilms Microbiomes 2020; 6:17. [PMID: 32221309 PMCID: PMC7101444 DOI: 10.1038/s41522-020-0128-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 03/12/2020] [Indexed: 01/28/2023] Open
Abstract
Transcription regulators from the LexA-like Protein Superfamily control a highly diverse assortment of genetic pathways in response to environmental stress. All characterized members of this family modulate their functionality and stability via a strict coordination with the coprotease function of RecA. Using the LexA-like protein IrvR from Streptococcus mutans, we demonstrate an exception to the RecA paradigm and illustrate how this evolutionary innovation has been coopted to diversify the stress responsiveness of S. mutans biofilms. Using a combination of genetics and biophysical measurements, we demonstrate how non-SOS stresses and SOS stresses each trigger separate regulatory mechanisms that stimulate production of a surface lectin responsible for remodeling the viscoelastic properties of extant biofilms during episodes of environmental stress. These studies demonstrate how changes in the external environment or even anti-biofilm therapeutic agents can activate biofilm-specific adaptive mechanisms responsible for bolstering the integrity of established biofilm communities. Such changes in biofilm community structure are likely to play central roles in the notorious recalcitrance of biofilm infections.
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Affiliation(s)
- Patrick Marx
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA
| | - Yu Sang
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA
| | - Hua Qin
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA
| | - Qingjing Wang
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA
| | - Rongkai Guo
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA
| | - Carmem Pfeifer
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA
| | - Jens Kreth
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA ,0000 0000 9758 5690grid.5288.7Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR 97239 USA
| | - Justin Merritt
- 0000 0000 9758 5690grid.5288.7Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR 97239 USA ,0000 0000 9758 5690grid.5288.7Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR 97239 USA
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Lei L, Zhang B, Mao M, Chen H, Wu S, Deng Y, Yang Y, Zhou H, Hu T. Carbohydrate Metabolism Regulated by Antisense vicR RNA in Cariogenicity. J Dent Res 2019; 99:204-213. [PMID: 31821772 DOI: 10.1177/0022034519890570] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Streptococcus mutans is a major cariogenic pathogen that resides in multispecies oral microbial biofilms. The VicRK 2-component system is crucial for bacterial adaptation, virulence, and biofilm organization and contains a global and vital response regulator, VicR. Notably, we identified an antisense vicR RNA (AS vicR) associated with an adjacent RNase III–encoding ( rnc) gene that was relevant to microRNA-size small RNAs (msRNAs). Here, we report that ASvicR overexpression significantly impeded bacterial growth, biofilm exopolysaccharide synthesis, and cariogenicity in vivo. Transcriptome analysis revealed that the AS vicR RNA mainly regulated carbohydrate metabolism. In particular, overproducing AS vicR demonstrated a reduction in galactose and glucose metabolism by monosaccharide composition analysis. The results of high-performance gel permeation chromatography revealed that the water-insoluble glucans isolated from AS vicR presented much lower molecular weights. Furthermore, direct evidence showed that total RNAs were disrupted by rnc-encoded RNase III. With the coexpression of T4 RNA ligase, putative msRNA1657, which is an rnc-related messenger RNA, was verified to bind to the 5′-UTR regions of the vicR gene. Furthermore, AS vicR regulation revealed a sponge regulatory-mediated network for msRNA associated with adjacent RNase III–encoding genes. There was an increase in AS vicR transcript levels in clinical S. mutans strains from caries-free children, while the expression of AS vicR was decreased in early childhood caries patients; this outcome may be explored as a potential strategy contributing to the management of dental caries. Taken together, our findings suggest an important role of AS vicR-mediated sponge regulation in S. mutans, indicating the characterization of lactose metabolism by a vital response regulator in cariogenicity. These findings have a number of implications and have reshaped our understanding of bacterial gene regulation from its transcriptional conception to the key roles of regulatory RNAs.
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Affiliation(s)
- L. Lei
- State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - B. Zhang
- State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - M. Mao
- State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
- Department of Endodontics, College of Stomatology, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - H. Chen
- State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - S. Wu
- West China School of Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Y. Deng
- State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Y. Yang
- State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - H. Zhou
- Department of Oral Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - T. Hu
- State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
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Mu R, Shinde P, Zou Z, Kreth J, Merritt J. Examining the Protein Interactome and Subcellular Localization of RNase J2 Complexes in Streptococcus mutans. Front Microbiol 2019; 10:2150. [PMID: 31620106 PMCID: PMC6759994 DOI: 10.3389/fmicb.2019.02150] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 09/02/2019] [Indexed: 12/18/2022] Open
Abstract
Regulated RNA turnover is vital for the control of gene expression in all cellular life. In Escherichia coli, this process is largely controlled by a stable degradosome complex containing RNase E and a variety of additional enzymes. In the Firmicutes phylum, species lack RNase E and often encode the paralogous enzymes RNase J1 and RNase J2. Unlike RNase J1, surprisingly little is known about the regulatory function and protein interactions of RNase J2, despite being a central pleiotropic regulator for the streptococci and other closely related organisms. Using crosslink coimmunoprecipitation in Streptococcus mutans, we have identified the major proteins found within RNase J2 protein complexes located in the cytoplasm and at the cell membrane. In both subcellular fractions, RNase J2 exhibited the most robust interactions with RNase J1, while additional transient and/or weaker "degradosome-like" interactions were also detected. In addition, RNase J2 exhibits multiple novel interactions that have not been previously reported for any RNase J proteins, some of which were highly biased for either the cytoplasmic or membrane fractions. We also determined that the RNase J2 C-terminal domain (CTD) encodes a structure that is likely conserved among RNase J enzymes and may have an analogous function to the C-terminal portion of RNase E. While we did observe a number of parallels between the RNase J2 interactome and the E. coli degradosome paradigm, our results suggest that S. mutans degradosomes are either unlikely to exist or are quite distinct from those of E. coli.
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Affiliation(s)
- Rong Mu
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, United States
| | - Pushkar Shinde
- Emory College of Arts and Sciences, Atlanta, GA, United States
| | - Zhengzhong Zou
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, United States
| | - Jens Kreth
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, United States.,Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Justin Merritt
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, United States.,Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, Portland, OR, United States
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8
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Abstract
RNases are key enzymes involved in RNA maturation and degradation. Although they play a crucial role in all domains of life, bacteria, archaea, and eukaryotes have evolved with their own sets of RNases and proteins modulating their activities. In bacteria, these enzymes allow modulation of gene expression to adapt to rapidly changing environments. Today, >20 RNases have been identified in both Escherichia coli and Bacillus subtilis, the paradigms of the Gram-negative and Gram-positive bacteria, respectively. However, only a handful of these enzymes are common to these two organisms and some of them are essential to only one. Moreover, although sets of RNases can be very similar in closely related bacteria such as the Firmicutes Staphylococcus aureus and B. subtilis, the relative importance of individual enzymes in posttranscriptional regulation in these organisms varies. In this review, we detail the role of the main RNases involved in RNA maturation and degradation in Gram-positive bacteria, with an emphasis on the roles of RNase J1, RNase III, and RNase Y. We also discuss how other proteins such as helicases can modulate the RNA-degradation activities of these enzymes.
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Liu N, Chaudhry MT, Xie Z, Kreth J, Merritt J. Identification of New Degrons in Streptococcus mutans Reveals a Novel Strategy for Engineering Targeted, Controllable Proteolysis. Front Microbiol 2017; 8:2572. [PMID: 29312250 PMCID: PMC5742171 DOI: 10.3389/fmicb.2017.02572] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 12/11/2017] [Indexed: 12/20/2022] Open
Abstract
Recently, controllable, targeted proteolysis has emerged as one of the most promising new strategies to study essential genes and otherwise toxic mutations. One of the principal limitations preventing the wider adoption of this approach is due to the lack of easily identifiable species-specific degrons that can be used to trigger the degradation of target proteins. Here, we report new advancements in the targeted proteolysis concept by creating the first prokaryotic N-terminal targeted proteolysis system. We demonstrate how proteins from the LexA-like protein superfamily can be exploited as species-specific reservoirs of N- and/or C-degrons, which are easily identifiable due to their proximity to strictly conserved residues found among LexA-like proteins. Using the LexA-like regulator HdiR of Streptococcus mutans, we identified two separate N-degrons derived from HdiR that confer highly efficient constitutive proteolysis upon target proteins when added as N-terminal peptide tags. Both degrons mediate degradation via AAA+ family housekeeping proteases with one degron primarily targeting FtsH and the other targeting the ClpP-dependent proteases. To modulate degron activity, our approach incorporates a hybrid N-terminal protein tag consisting of the ubiquitin-like protein NEDD8 fused to an HdiR degron. The NEDD8 fusion inhibits degron function until the NEDD8-specific endopeptidase NEDP1 is heterologously expressed to expose the N-degron. By fusing the NEDD8-degron tag onto GFP, luciferase, and the pleiotropic regulator RNase J2, we demonstrate that the N-terminal proteolysis approach exhibits far superior performance compared to the classic transcriptional depletion approach and is similarly applicable for the study of highly toxic mutations.
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Affiliation(s)
- Nan Liu
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, United States
| | | | - Zhoujie Xie
- MOE Key Laboratory of Industrial Fermentation Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Jens Kreth
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, United States
| | - Justin Merritt
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, United States.,Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, Portland, OR, United States
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Pei XY, Bralley P, Jones GH, Luisi BF. Linkage of catalysis and 5' end recognition in ribonuclease RNase J. Nucleic Acids Res 2015; 43:8066-76. [PMID: 26253740 PMCID: PMC4652760 DOI: 10.1093/nar/gkv732] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/07/2015] [Indexed: 11/25/2022] Open
Abstract
In diverse bacterial species, the turnover and processing of many RNAs is mediated by the ribonuclease RNase J, a member of the widely occurring metallo-β-lactamase enzyme family. We present crystal structures of Streptomyces coelicolor RNase J with bound RNA in pre- and post-cleavage states, at 2.27 Å and 2.80 Å resolution, respectively. These structures reveal snapshots of the enzyme cleaving substrate directionally and sequentially from the 5′ terminus. In the pre-cleavage state, a water molecule is coordinated to a zinc ion pair in the active site but is imperfectly oriented to launch a nucleophilic attack on the phosphate backbone. A conformational switch is envisaged that enables the in-line positioning of the attacking water and may be facilitated by magnesium ions. Adjacent to the scissile bond, four bases are stacked in a tightly sandwiching pocket, and mutagenesis results indicate that this organization helps to drive processive exo-ribonucleolytic cleavage. Like its numerous homologues, S. coelicolor RNase J can also cleave some RNA internally, and the structural data suggest how the preference for exo- versus endo-cleavage mode is linked with recognition of the chemical status of the substrate's 5′ end.
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Affiliation(s)
- Xue-Yuan Pei
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | | | - George H Jones
- Department of Biology, Emory University, Atlanta Georgia, USA
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
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