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Kruszewska-Naczk B, Grinholc M, Waleron K, Bandow JE, Rapacka-Zdończyk A. Can antimicrobial blue light contribute to resistance development? Genome-wide analysis revealed aBL-protective genes in Escherichia coli. Microbiol Spectr 2024; 12:e0249023. [PMID: 38063383 PMCID: PMC10782963 DOI: 10.1128/spectrum.02490-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 10/24/2023] [Indexed: 01/13/2024] Open
Abstract
IMPORTANCE Increasing antibiotic resistance and the lack of new antibiotic-like compounds to combat bacterial resistance are significant problems of modern medicine. The development of new alternative therapeutic strategies is extremely important. Antimicrobial blue light (aBL) is an innovative approach to combat multidrug-resistant microorganisms. aBL has a multitarget mode of action; however, the full mechanism of aBL antibacterial action requires further investigation. In addition, the potential risk of resistance development to this treatment should be considered.
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Affiliation(s)
- Beata Kruszewska-Naczk
- Laboratory of Photobiology and Molecular Diagnostics, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
- Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Medical University of Gdansk, Gdansk, Poland
| | - Mariusz Grinholc
- Laboratory of Photobiology and Molecular Diagnostics, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Krzysztof Waleron
- Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Medical University of Gdansk, Gdansk, Poland
| | - Julia Elisabeth Bandow
- Applied Microbiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitätsstraße, Bochum, Germany
| | - Aleksandra Rapacka-Zdończyk
- Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Medical University of Gdansk, Gdansk, Poland
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2
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Mechanistic insights into Lhr helicase function in DNA repair. Biochem J 2021; 477:2935-2947. [PMID: 32706021 PMCID: PMC7437997 DOI: 10.1042/bcj20200379] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 07/23/2020] [Accepted: 07/23/2020] [Indexed: 12/16/2022]
Abstract
The DNA helicase Large helicase-related (Lhr) is present throughout archaea, including in the Asgard and Nanoarchaea, and has homologues in bacteria and eukaryotes. It is thought to function in DNA repair but in a context that is not known. Our data show that archaeal Lhr preferentially targets DNA replication fork structures. In a genetic assay, expression of archaeal Lhr gave a phenotype identical to the replication-coupled DNA repair enzymes Hel308 and RecQ. Purified archaeal Lhr preferentially unwound model forked DNA substrates compared with DNA duplexes, flaps and Holliday junctions, and unwound them with directionality. Single-molecule FRET measurements showed that binding of Lhr to a DNA fork causes ATP-independent distortion and base-pair melting at, or close to, the fork branchpoint. ATP-dependent directional translocation of Lhr resulted in fork DNA unwinding through the ‘parental’ DNA strands. Interaction of Lhr with replication forks in vivo and in vitro suggests that it contributes to DNA repair at stalled or broken DNA replication.
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Knutson SD, Sanford AA, Swenson CS, Korn MM, Manuel BA, Heemstra JM. Thermoreversible Control of Nucleic Acid Structure and Function with Glyoxal Caging. J Am Chem Soc 2020; 142:17766-17781. [PMID: 33017148 DOI: 10.1021/jacs.0c08996] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Controlling the structure and activity of nucleic acids dramatically expands their potential for application in therapeutics, biosensing, nanotechnology, and biocomputing. Several methods have been developed to impart responsiveness of DNA and RNA to small-molecule and light-based stimuli. However, heat-triggered control of nucleic acids has remained largely unexplored, leaving a significant gap in responsive nucleic acid technology. Moreover, current technologies have been limited to natural nucleic acids and are often incompatible with polymerase-generated sequences. Here we show that glyoxal, a well-characterized compound that covalently attaches to the Watson-Crick-Franklin face of several nucleobases, addresses these limitations by thermoreversibly modulating the structure and activity of virtually any nucleic acid scaffold. Using a variety of DNA and RNA constructs, we demonstrate that glyoxal modification is easily installed and potently disrupts nucleic acid structure and function. We also characterize the kinetics of decaging and show that activity can be restored via tunable thermal removal of glyoxal adducts under a variety of conditions. We further illustrate the versatility of this approach by reversibly caging a 2'-O-methylated RNA aptamer as well as synthetic threose nucleic acid (TNA) and peptide nucleic acid (PNA) scaffolds. Glyoxal caging can also be used to reversibly disrupt enzyme-nucleic acid interactions, and we show that caging of guide RNA allows for tunable and reversible control over CRISPR-Cas9 activity. We also demonstrate glyoxal caging as an effective method for enhancing PCR specificity, and we cage a biostable antisense oligonucleotide for time-release activation and titration of gene expression in living cells. Together, glyoxalation is a straightforward and scarless method for imparting reversible thermal responsiveness to theoretically any nucleic acid architecture, addressing a significant need in synthetic biology and offering a versatile new tool for constructing programmable nucleic acid components in medicine, nanotechnology, and biocomputing.
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Affiliation(s)
- Steve D Knutson
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Aimee A Sanford
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Colin S Swenson
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Megan M Korn
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Brea A Manuel
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Jennifer M Heemstra
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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Abstract
In light of the rising prevalence of antimicrobial resistance (AMR) and the slow pace of new antimicrobial development, there has been increasing interest in the development of adjuvants that improve or restore the effectiveness of existing drugs. Here, we use a novel small RNA (sRNA) screening approach to identify genes whose knockdown increases ciprofloxacin (CIP) sensitivity in a resistant strain of Escherichia coli 5000 sRNA constructs were initially screened on a gyrA S83L background, ultimately leading to 30 validated genes whose disruption reduces CIP resistance. This set includes genes involved in DNA replication, repair, recombination, efflux, and other regulatory systems. Our findings increase understanding of the functional interactions of DNA Gyrase, and may aid in the development of new therapeutic approaches for combating AMR.
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Bechhofer DH, Deutscher MP. Bacterial ribonucleases and their roles in RNA metabolism. Crit Rev Biochem Mol Biol 2019; 54:242-300. [PMID: 31464530 PMCID: PMC6776250 DOI: 10.1080/10409238.2019.1651816] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/22/2019] [Accepted: 07/31/2019] [Indexed: 12/16/2022]
Abstract
Ribonucleases (RNases) are mediators in most reactions of RNA metabolism. In recent years, there has been a surge of new information about RNases and the roles they play in cell physiology. In this review, a detailed description of bacterial RNases is presented, focusing primarily on those from Escherichia coli and Bacillus subtilis, the model Gram-negative and Gram-positive organisms, from which most of our current knowledge has been derived. Information from other organisms is also included, where relevant. In an extensive catalog of the known bacterial RNases, their structure, mechanism of action, physiological roles, genetics, and possible regulation are described. The RNase complement of E. coli and B. subtilis is compared, emphasizing the similarities, but especially the differences, between the two. Included are figures showing the three major RNA metabolic pathways in E. coli and B. subtilis and highlighting specific steps in each of the pathways catalyzed by the different RNases. This compilation of the currently available knowledge about bacterial RNases will be a useful tool for workers in the RNA field and for others interested in learning about this area.
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Affiliation(s)
- David H. Bechhofer
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Murray P. Deutscher
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, FL, USA
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6
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Abstract
This review provides a description of the known Escherichia coli ribonucleases (RNases), focusing on their structures, catalytic properties, genes, physiological roles, and possible regulation. Currently, eight E. coli exoribonucleases are known. These are RNases II, R, D, T, PH, BN, polynucleotide phosphorylase (PNPase), and oligoribonuclease (ORNase). Based on sequence analysis and catalytic properties, the eight exoribonucleases have been grouped into four families. These are the RNR family, including RNase II and RNase R; the DEDD family, including RNase D, RNase T, and ORNase; the RBN family, consisting of RNase BN; and the PDX family, including PNPase and RNase PH. Seven well-characterized endoribonucleases are known in E. coli. These are RNases I, III, P, E, G, HI, and HII. Homologues to most of these enzymes are also present in Salmonella. Most of the endoribonucleases cleave RNA in the presence of divalent cations, producing fragments with 3'-hydroxyl and 5'-phosphate termini. RNase H selectively hydrolyzes the RNA strand of RNA?DNA hybrids. Members of the RNase H family are widely distributed among prokaryotic and eukaryotic organisms in three distinct lineages, RNases HI, HII, and HIII. It is likely that E. coli contains additional endoribonucleases that have not yet been characterized. First of all, endonucleolytic activities are needed for certain known processes that cannot be attributed to any of the known enzymes. Second, homologues of known endoribonucleases are present in E. coli. Third, endonucleolytic activities have been observed in cell extracts that have different properties from known enzymes.
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Abstract
DNA exonucleases, enzymes that hydrolyze phosphodiester bonds in DNA from a free end, play important cellular roles in DNA repair, genetic recombination and mutation avoidance in all organisms. This article reviews the structure, biochemistry, and biological functions of the 17 exonucleases currently identified in the bacterium Escherichia coli. These include the exonucleases associated with DNA polymerases I (polA), II (polB), and III (dnaQ/mutD); Exonucleases I (xonA/sbcB), III (xthA), IV, VII (xseAB), IX (xni/xgdG), and X (exoX); the RecBCD, RecJ, and RecE exonucleases; SbcCD endo/exonucleases; the DNA exonuclease activities of RNase T (rnt) and Endonuclease IV (nfo); and TatD. These enzymes are diverse in terms of substrate specificity and biochemical properties and have specialized biological roles. Most of these enzymes fall into structural families with characteristic sequence motifs, and members of many of these families can be found in all domains of life.
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Functions that Protect Escherichia coli from Tightly Bound DNA-Protein Complexes Created by Mutant EcoRII Methyltransferase. PLoS One 2015; 10:e0128092. [PMID: 25993347 PMCID: PMC4437897 DOI: 10.1371/journal.pone.0128092] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 04/23/2015] [Indexed: 11/19/2022] Open
Abstract
Expression of mutant EcoRII methyltransferase protein (M.EcoRII-C186A) in Escherichia coli leads to tightly bound DNA-protein complexes (TBCs), located sporadically on the chromosome rather than in tandem arrays. The mechanisms behind the lethality induced by such sporadic TBCs are not well studied, nor is it clear whether very tight binding but non-covalent complexes are processed in the same way as covalent DNA-protein crosslinks (DPCs). Using 2D gel electrophoresis, we found that TBCs induced by M.EcoRII-C186A block replication forks in vivo. Specific bubble molecules were detected as spots on the 2D gel, only when M.EcoRII-C186A was induced, and a mutation that eliminates a specific EcoRII methylation site led to disappearance of the corresponding spot. We also performed a candidate gene screen for mutants that are hypersensitive to TBCs induced by M.EcoRII-C186A. We found several gene products necessary for protection against these TBCs that are known to also protect against DPCs induced with wild-type M.EcoRII (after 5-azacytidine incorporation): RecA, RecBC, RecG, RuvABC, UvrD, FtsK, XerCD and SsrA (tmRNA). In contrast, the RecFOR pathway and Rep helicase are needed for protection against TBCs but not DPCs induced by M.EcoRII. We propose that stalled fork processing by RecFOR and RecA promotes release of tightly bound (but non-covalent) blocking proteins, perhaps by licensing Rep helicase-driven dissociation of the blocking M.EcoRII-C186A. Our studies also argued against the involvement of several proteins that might be expected to protect against TBCs. We took the opportunity to directly compare the sensitivity of all tested mutants to two quinolone antibiotics, which target bacterial type II topoisomerases and induce a unique form of DPC. We uncovered rep, ftsK and xerCD as novel quinolone hypersensitive mutants, and also obtained evidence against the involvement of a number of functions that might be expected to protect against quinolones.
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Hsiao YY, Fang WH, Lee CC, Chen YP, Yuan HS. Structural insights into DNA repair by RNase T--an exonuclease processing 3' end of structured DNA in repair pathways. PLoS Biol 2014; 12:e1001803. [PMID: 24594808 PMCID: PMC3942315 DOI: 10.1371/journal.pbio.1001803] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 01/21/2014] [Indexed: 11/19/2022] Open
Abstract
DNA repair mechanisms are essential for preservation of genome integrity. However, it is not clear how DNA are selected and processed at broken ends by exonucleases during repair pathways. Here we show that the DnaQ-like exonuclease RNase T is critical for Escherichia coli resistance to various DNA-damaging agents and UV radiation. RNase T specifically trims the 3' end of structured DNA, including bulge, bubble, and Y-structured DNA, and it can work with Endonuclease V to restore the deaminated base in an inosine-containing heteroduplex DNA. Crystal structure analyses further reveal how RNase T recognizes the bulge DNA by inserting a phenylalanine into the bulge, and as a result the 3' end of blunt-end bulge DNA can be digested by RNase T. In contrast, the homodimeric RNase T interacts with the Y-structured DNA by a different binding mode via a single protomer so that the 3' overhang of the Y-structured DNA can be trimmed closely to the duplex region. Our data suggest that RNase T likely processes bulge and bubble DNA in the Endonuclease V-dependent DNA repair, whereas it processes Y-structured DNA in UV-induced and various other DNA repair pathways. This study thus provides mechanistic insights for RNase T and thousands of DnaQ-like exonucleases in DNA 3'-end processing.
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Affiliation(s)
- Yu-Yuan Hsiao
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan, Republic of China
| | - Woei-Horng Fang
- Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China
| | - Chia-Chia Lee
- Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China
| | - Yi-Ping Chen
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Hanna S. Yuan
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, Republic of China
- Graduate Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei, Taiwan, Republic of China
- * E-mail:
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10
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Hsiao YY, Duh Y, Chen YP, Wang YT, Yuan HS. How an exonuclease decides where to stop in trimming of nucleic acids: crystal structures of RNase T-product complexes. Nucleic Acids Res 2012; 40:8144-54. [PMID: 22718982 PMCID: PMC3439924 DOI: 10.1093/nar/gks548] [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: 12/01/2022] Open
Abstract
Exonucleases are key enzymes in the maintenance of genome stability, processing of immature RNA precursors and degradation of unnecessary nucleic acids. However, it remains unclear how exonucleases digest nucleic acids to generate correct end products for next-step processing. Here we show how the exonuclease RNase T stops its trimming precisely. The crystal structures of RNase T in complex with a stem-loop DNA, a GG dinucleotide and single-stranded DNA with different 3′-end sequences demonstrate why a duplex with a short 3′-overhang, a dinucleotide and a ssDNA with a 3′-end C cannot be further digested by RNase T. Several hydrophobic residues in RNase T change their conformation upon substrate binding and induce an active or inactive conformation in the active site that construct a precise machine to determine which substrate should be digested based on its sequence, length and structure. These studies thus provide mechanistic insights into how RNase T prevents over digestion of its various substrates, and the results can be extrapolated to the thousands of members of the DEDDh family of exonucleases.
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Affiliation(s)
- Yu-Yuan Hsiao
- Institute of Molecular Biology, Academia Sinica, Taipei, 11529, Taiwan, ROC
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11
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Rath D, Mangoli SH, Pagedar AR, Jawali N. Involvement of pnp in survival of UV radiation in Escherichia coli K-12. MICROBIOLOGY-SGM 2012; 158:1196-1205. [PMID: 22322961 DOI: 10.1099/mic.0.056309-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Polynucleotide phosphorylase (PNPase), a multifunctional protein, is a 3'→5' exoribonuclease or exoDNase in the presence of inorganic phosphate (P(i)), and extends a 3'-OH of RNA or ssDNA in the presence of ADP or dADP. In Escherichia coli, PNPase is known to protect against H(2)O(2)- and mitomycin C-induced damage. Recent reports show that Bacillus subtilis PNPase is required for repair of H(2)O(2)-induced double-strand breaks. Here we show that absence of PNPase makes E. coli cells sensitive to UV, indicating that PNPase has a role in survival of UV radiation damage. Analyses of various DNA repair pathways show that in the absence of nucleotide excision repair, survival of UV radiation depends critically on PNPase function. Consequently, uvrA pnp, uvrB pnp and uvrC pnp strains show hypersensitivity to UV radiation. Whereas the pnp mutation is non-epistatic to recJ, recQ and recG mutations with respect to the UV-sensitivity phenotype, it is epistatic to uvrD, recB and ruvA mutations, implicating it in the recombinational repair process.
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Affiliation(s)
- Devashish Rath
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
| | - Suhas H Mangoli
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
| | - Amruta R Pagedar
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
| | - Narendra Jawali
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
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12
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Structural basis for RNA trimming by RNase T in stable RNA 3'-end maturation. Nat Chem Biol 2011; 7:236-43. [PMID: 21317904 DOI: 10.1038/nchembio.524] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 01/07/2011] [Indexed: 01/28/2023]
Abstract
RNA maturation relies on various exonucleases to remove nucleotides successively from the 5' or 3' end of nucleic acids. However, little is known regarding the molecular basis for substrate and cleavage preference of exonucleases. Our biochemical and structural analyses on RNase T-DNA complexes show that the RNase T dimer has an ideal architecture for binding a duplex with a short 3' overhang to produce a digestion product of a duplex with a 2-nucleotide (nt) or 1-nt 3' overhang, depending on the composition of the last base pair in the duplex. A 'C-filter' in RNase T screens out the nucleic acids with 3'-terminal cytosines for hydrolysis by inducing a disruptive conformational change at the active site. Our results reveal the general principles and the working mechanism for the final trimming step made by RNase T in the maturation of stable RNA and pave the way for the understanding of other DEDD family exonucleases.
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13
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Mismatch-induced lethality due to a defect in Escherichia coli RecQ helicase in exonuclease-deficient background: Dependence on MutS and UvrD functions. Plasmid 2010; 63:119-27. [DOI: 10.1016/j.plasmid.2009.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 12/01/2009] [Accepted: 12/02/2009] [Indexed: 11/23/2022]
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Larrea AA, Pedroso IM, Malhotra A, Myers RS. Identification of two conserved aspartic acid residues required for DNA digestion by a novel thermophilic Exonuclease VII in Thermotoga maritima. Nucleic Acids Res 2008; 36:5992-6003. [PMID: 18812402 PMCID: PMC2566859 DOI: 10.1093/nar/gkn588] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Exonuclease VII was first identified in 1974 as a DNA exonuclease that did not require any divalent cations for activity. Indeed, Escherichia coli ExoVII was identified in partially purified extracts in the presence of EDTA. ExoVII is comprised of two subunits (XseA and XseB) that are highly conserved and present in most sequenced prokaryotic genomes, but are not seen in eukaryotes. To better understand this exonuclease family, we have characterized an ExoVII homolog from Thermotoga maritima. Thermotoga maritima XseA/B homologs TM1768 and TM1769 were co-expressed and purified, and show robust nuclease activity at 80°C. This activity is magnesium dependent and is inhibited by phosphate ions, which distinguish it from E. coli ExoVII. Nevertheless, both E. coli and T. maritima ExoVII share a similar putative active site motif with two conserved aspartate residues in the large (XseA/TM1768) subunit. We show that these residues, Asp235 and Asp240, are essential for the nuclease activity of T. maritima ExoVII. We hypothesize that the ExoVII family of nucleases can be sub-divided into two sub-families based on EDTA resistance and that T. maritima ExoVII is the first member of the branch that is characterized by EDTA sensitivity and inhibition by phosphate.
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Affiliation(s)
- Andres A Larrea
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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15
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Serment-Guerrero J, Brena-Valle M, Espinosa-Aguirre JJ. In vivo role of Escherichia coli single-strand exonucleases in SOS induction by gamma radiation. Mutagenesis 2008; 23:317-23. [DOI: 10.1093/mutage/gen017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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16
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Yang XC, Purdy M, Marzluff WF, Dominski Z. Characterization of 3'hExo, a 3' exonuclease specifically interacting with the 3' end of histone mRNA. J Biol Chem 2006; 281:30447-54. [PMID: 16912046 DOI: 10.1074/jbc.m602947200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 3' end of mammalian histone mRNAs consisting of a conserved stem-loop and a terminal ACCCA interacts with a recently identified human 3' exonuclease designated 3'hExo. The sequence-specific interaction suggests that 3'hExo may participate in the degradation of histone mRNAs. ERI-1, a Caenorhabditis elegans homologue of 3'hExo, has been implicated in degradation of small interfering RNAs. We introduced a number of mutations to 3'hExo to identify residues required for RNA binding and catalysis. To assure that the introduced mutations specifically target one of these two activities of 3'hExo rather than cause global structural defects, the mutant proteins were tested in parallel for the ability both to bind the stem-loop RNA and to degrade RNA substrates. Our analysis confirms that 3'hExo is a member of the DEDDh family of 3' exonucleases. Specific binding to the RNA requires the SAP domain and two lysines located immediately to its C terminus. 3'hExo binds with the highest affinity to the wild-type 3' end of histone mRNA, and any changes to this sequence reduce efficiency of binding. 3'hExo has only residual, if any, 3' exonuclease activity on DNA substrates and localizes mostly to the cytoplasm, suggesting that in vivo it performs exclusively RNA-specific functions. Efficient degradation of RNA substrates by 3'hExo requires 2' and 3' hydroxyl groups at the last nucleotide. 3'hExo removes 3' overhangs of small interfering RNAs, whereas the double-stranded region is resistant to the enzymatic activity.
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Affiliation(s)
- Xiao-cui Yang
- Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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17
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Jiang X, Huang H, Zhang Y, Zhang Y. Dynamically cured polypropylene/epoxy blends. J Appl Polym Sci 2004. [DOI: 10.1002/app.13700] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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18
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Dominski Z, Yang XC, Kaygun H, Dadlez M, Marzluff WF. A 3' exonuclease that specifically interacts with the 3' end of histone mRNA. Mol Cell 2003; 12:295-305. [PMID: 14536070 DOI: 10.1016/s1097-2765(03)00278-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Metazoan histone mRNAs end in a highly conserved stem-loop structure followed by ACCCA. Previous studies have suggested that the stem-loop binding protein (SLBP) is the only protein binding this region. Using RNA affinity purification, we identified a second protein, designated 3'hExo, that contains a SAP and a 3' exonuclease domain and binds the same sequence. Strikingly, 3'hExo can bind the stem-loop region both separately and simultaneously with SLBP. Binding of 3'hExo requires the terminal ACCCA, whereas binding of SLBP requires the 5' side of the stem-loop region. Recombinant 3'hExo degrades RNA substrates in a 3'-5' direction and has the highest activity toward the wild-type histone mRNA. Binding of SLBP to the stem-loop at the 3' end of RNA prevents its degradation by 3'hExo. These features make 3'hExo a primary candidate for the exonuclease that initiates rapid decay of histone mRNA upon completion and/or inhibition of DNA replication.
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Affiliation(s)
- Zbigniew Dominski
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
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19
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Zuo Y, Deutscher MP. The physiological role of RNase T can be explained by its unusual substrate specificity. J Biol Chem 2002; 277:29654-61. [PMID: 12050169 DOI: 10.1074/jbc.m204252200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli RNase T, the enzyme responsible for the end-turnover of tRNA and for the 3' maturation of 5 S and 23 S rRNAs and many other small, stable RNAs, was examined in detail with respect to its substrate specificity. The enzyme was found to be a single-strand-specific exoribonuclease that acts in the 3' to 5' direction in a non-processive manner. However, although other Escherichia coli exoribonucleases stop several nucleotides downstream of an RNA duplex, RNase T can digest RNA up to the first base pair. The presence of a free 3'-hydroxyl group is required for the enzyme to initiate digestion. Studies with RNA homopolymers and a variety of oligoribonucleotides revealed that RNase T displays an unusual base specificity, discriminating against pyrimidine and, particularly, C residues. Although RNase T appears to bind up to 10 nucleotides in its active site, its specificity is defined largely by the last 4 residues. A single 3'-terminal C residue can reduce RNase T action by >100-fold, and 2-terminal C residues essentially stop the enzyme. In vivo, the substrates of RNase T are similar in that they all contain a double-stranded stem followed by a single-stranded 3' overhang; yet, the action of RNase T on these substrates differs. The substrate specificity described here helps to explain why the different substrates yield different products, and why certain RNA molecules are not substrates at all.
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Affiliation(s)
- Yuhong Zuo
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, Florida 33101-6129, USA
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Mazur DJ, Perrino FW. Excision of 3' termini by the Trex1 and TREX2 3'-->5' exonucleases. Characterization of the recombinant proteins. J Biol Chem 2001; 276:17022-9. [PMID: 11279105 DOI: 10.1074/jbc.m100623200] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The excision of nucleotides from DNA 3' termini is an important step in DNA replication, repair, and recombination pathways to generate correctly base paired termini for subsequent processing. The mammalian TREX1 and TREX2 proteins contain potent 3'-->5' exonucleases capable of functioning in this capacity. To study the activities of these exonucleases we have developed strategies to express and purify the recombinant mouse Trex1 and human TREX2 proteins in Escherichia coli in quantities sufficient for biochemical characterization. The Trex1 and TREX2 proteins are homodimers that exhibit robust 3' excision activities with very similar preferred reaction conditions and preferences for specific DNA substrates. In a steady-state kinetic analysis, oligonucleotide substrates were used to measure 3' nucleotide excision by Trex1 and TREX2. The Michaelis constants derived from these data indicate similar apparent kcat values of 22 s(-1) for Trex1 and 16 s(-1) for TREX2 using single-stranded oligonucleotides. The apparent KM values of 19 nm for Trex1 and 190 nm for TREX2 suggest relatively high affinities for DNA for both Trex1 and TREX2. An exonuclease competition assay was designed using heparin as a nonsubstrate inhibitor with a series of partial duplex DNAs to delineate the substrate structure preferences for 3' nucleotide excision by Trex1 and TREX2. The catalytic properties of the TREX proteins suggest roles for these enzymes in the 3' end-trimming processes necessary for producing correctly base paired 3' termini.
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Affiliation(s)
- D J Mazur
- Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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21
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Abstract
We present a summary of recent progress in understanding Escherichia coli K-12 gene and protein functions. New information has come both from classical biological experimentation and from using the analytical tools of functional genomics. The content of the E. coli genome can clearly be seen to contain elements acquired by horizontal transfer. Nevertheless, there is probably a large, stable core of >3500 genes that are shared among all E. coli strains. The gene-enzyme relationship is examined, and, in many cases, it exhibits complexity beyond a simple one-to-one relationship. Also, the E. coli genome can now be seen to contain many multiple enzymes that carry out the same or closely similar reactions. Some are similar in sequence and may share common ancestry; some are not. We discuss the concept of a minimal genome as being variable among organisms and obligatorily linked to their life styles and defined environmental conditions. We also address classification of functions of gene products and avenues of insight into the history of protein evolution.
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Affiliation(s)
- M Riley
- The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA. ,
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22
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Deutscher MP, Li Z. Exoribonucleases and their multiple roles in RNA metabolism. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2001; 66:67-105. [PMID: 11051762 DOI: 10.1016/s0079-6603(00)66027-0] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In recent years there has been a dramatic shift in our thinking about ribonucleases (RNases). Although they were once considered to be nonspecific, degradative enzymes, it is now clear that RNases play a central role in every aspect of cellular RNA metabolism, including decay of mRNA, conversion of RNA precursors to their mature forms, and end-turnover of certain RNAs. Recognition of the importance of this class of enzymes has led to an explosion of work and the establishment of significant new concepts. Thus, we now realize that RNases, both endoribonucleases and exoribonucleases, can be highly specific for particular sequences or structures. It has also become apparent that a single cell can contain a large number of distinct RNases, approaching as many as 20 members, often with overlapping specificities. Some RNases also have been found to be components of supramolecular complexes and to function in concert with other enzymes to carry out their role in RNA metabolism. This review focuses on the exoribonucleases, both prokaryotic and eukaryotic, and details their structure, catalytic properties, and physiological function.
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Affiliation(s)
- M P Deutscher
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Florida 33101, USA
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Viswanathan M, Lovett ST. Exonuclease X of Escherichia coli. A novel 3'-5' DNase and Dnaq superfamily member involved in DNA repair. J Biol Chem 1999; 274:30094-100. [PMID: 10514496 DOI: 10.1074/jbc.274.42.30094] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA exonucleases are critical for DNA replication, repair, and recombination. In the bacterium Escherichia coli there are 14 DNA exonucleases including exonucleases I-IX (including the two DNA polymerase I exonucleases), RecJ exonuclease, SbcCD exonuclease, RNase T, and the exonuclease domains of DNA polymerase II and III. Here we report the discovery and characterization of a new E. coli exonuclease, exonuclease X. Exonuclease X is a member of a superfamily of proteins that have homology to the 3'-5' exonuclease proofreading subunit (DnaQ) of E. coli DNA polymerase III. We have engineered and purified a (His)(6)-exonuclease X fusion protein and characterized its activity. Exonuclease X is a potent distributive exonuclease, capable of degrading both single-stranded and duplex DNA with 3'-5' polarity. Its high affinity for single-strand DNA and its rapid catalytic rate are similar to the processive exonucleases RecJ and exonuclease I. Deletion of the exoX gene exacerbated the UV sensitivity of a strain lacking RecJ, exonuclease I, and exonuclease VII. When overexpressed, exonuclease X is capable of substituting for exonuclease I in UV repair. As we have proposed for the other single-strand DNA exonucleases, exonuclease X may facilitate recombinational repair by pre-synaptic and/or post-synaptic DNA degradation.
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Affiliation(s)
- M Viswanathan
- Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110, USA
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