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Gladysheva-Azgari M, Sharko F, Evteeva M, Kuvyrchenkova A, Boulygina E, Tsygankova S, Slobodova N, Pustovoit K, Melkina O, Nedoluzhko A, Korzhenkov A, Kudryavtseva A, Utkina A, Manukhov I, Rastorguev S, Zavilgelsky G. ArdA genes from pKM101 and from B. bifidum chromosome have a different range of regulated genes. Heliyon 2023; 9:e22986. [PMID: 38144267 PMCID: PMC10746416 DOI: 10.1016/j.heliyon.2023.e22986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 09/18/2023] [Accepted: 11/23/2023] [Indexed: 12/26/2023] Open
Abstract
The ardA genes are present in a wide variety of conjugative plasmids and play an important role in overcoming the restriction barrier. To date, there is no information on the chromosomal ardA genes. It is still unclear whether they keep their antirestriction activity and why bacterial chromosomes contain these genes. In the present study, we confirmed the antirestriction function of the ardA gene from the Bifidobacterium bifidum chromosome. Transcriptome analysis in Escherichia coli showed that the range of regulated genes varies significantly for ardA from conjugative plasmid pKM101 and from the B. bifidum chromosome. Moreover, if the targets for both ardA genes match, they often show an opposite effect on regulated gene expression. The results obtained indicate two seemingly mutually exclusive conclusions. On the one hand, the pleiotropic effect of ardA genes was shown not only on restriction-modification system, but also on expression of a number of other genes. On the other hand, the range of affected genes varies significally for ardA genes from different sources, which indicates the specificity of ardA to inhibited targets. Author Summary. Conjugative plasmids, bacteriophages, as well as transposons, are capable to transfer various genes, including antibiotic resistance genes, among bacterial cells. However, many of those genes pose a threat to the bacterial cells, therefore bacterial cells have special restriction systems that limit such transfer. Antirestriction genes have previously been described as a part of conjugative plasmids, and bacteriophages and transposons. Those plasmids are able to overcome bacterial cell protection in the presence of antirestriction genes, which inhibit bacterial restriction systems. This work unveils the antirestriction mechanisms, which play an important role in the bacterial life cycle. Here, we clearly show that antirestriction genes, which are able to inhibit cell protection, exist not only in plasmids but also in the bacterial chromosomes themselves. Moreover, antirestrictases have not only an inhibitory function but also participate in the regulation of other bacterial genes. The regulatory function of plasmid antirestriction genes also helps them to overcome the bacterial cell protection against gene transfer, whereas the regulatory function of genomic antirestrictases has no such effect.
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Affiliation(s)
| | - F.S. Sharko
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
- Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
| | - M.A. Evteeva
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | | | - E.S. Boulygina
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | - S.V. Tsygankova
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | - N.V. Slobodova
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | - K.S. Pustovoit
- State Research Institute of Genetics and Selection of Industrial Microorganisms of the National Research Center “Kurchatov Institute”, Moscow, Russia, 115454
| | - O.E. Melkina
- State Research Institute of Genetics and Selection of Industrial Microorganisms of the National Research Center “Kurchatov Institute”, Moscow, Russia, 115454
| | - A.V. Nedoluzhko
- European University at Saint Petersburg, 191187, Saint-Petersburg, Russia
| | - A.A. Korzhenkov
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
| | - A.A. Kudryavtseva
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141701, Dolgoprudny, Russia
| | - A.A. Utkina
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141701, Dolgoprudny, Russia
| | - I.V. Manukhov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141701, Dolgoprudny, Russia
- Faculty of Physics, HSE University, 109028, Moscow, Russia
- Laboratory for Microbiology, BIOTECH University, 125080, Moscow, Russia
| | - S.M. Rastorguev
- National Research Center "Kurchatov Institute", 123182, Moscow, Russia
- Pirogov Russian National Research Medical University, Ostrovityanova Str. 1, Moscow, 117997, Russia
| | - G.B. Zavilgelsky
- State Research Institute of Genetics and Selection of Industrial Microorganisms of the National Research Center “Kurchatov Institute”, Moscow, Russia, 115454
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Shintani M, Vestergaard G, Milaković M, Kublik S, Smalla K, Schloter M, Udiković-Kolić N. Integrons, transposons and IS elements promote diversification of multidrug resistance plasmids and adaptation of their hosts to antibiotic pollutants from pharmaceutical companies. Environ Microbiol 2023; 25:3035-3051. [PMID: 37655671 DOI: 10.1111/1462-2920.16481] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 08/01/2023] [Indexed: 09/02/2023]
Abstract
Plasmids are important vehicles for the dissemination of antibiotic resistance genes (ARGs) among bacteria by conjugation. Here, we determined the complete nucleotide sequences of nine different plasmids previously obtained by exogenous plasmid isolation from river and creek sediments and wastewater from a pharmaceutical company. We identified six IncP/P-1ε plasmids and single members of IncL, IncN and IncFII-like plasmids. Genetic structures of the accessory regions of the IncP/P-1ε plasmids obtained implied that multiple insertions and deletions had occurred, mediated by different transposons and Class 1 integrons with various ARGs. Our study provides compelling evidence that Class 1 integrons, Tn402-like transposons, Tn3-like transposons and/or IS26 played important roles in the acquisition of ARGs across all investigated plasmids. Our plasmid sequencing data provide new insights into how these mobile genetic elements could mediate the acquisition and spread of ARGs in environmental bacteria.
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Affiliation(s)
- Masaki Shintani
- Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, Japan
- Research Institute of Green Science and Technology, Shizuoka University, Shizuoka, Japan
- Japan Collection of Microorganisms, RIKEN BioResource Research Center, Ibaraki, Japan
| | | | - Milena Milaković
- Division for Marine and Environmental Research, Ruđer Bošković Institute, Croatia
| | - Susanne Kublik
- Research Unit for Comparative Microbiome Analysis, Helmholtz Zentrum München, Zagreb, Germany
| | - Kornelia Smalla
- Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Braunschweig, Germany
| | - Michael Schloter
- Research Unit for Comparative Microbiome Analysis, Helmholtz Zentrum München, Zagreb, Germany
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3
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Cooke MB, Herman C. Conjugation's Toolkit: the Roles of Nonstructural Proteins in Bacterial Sex. J Bacteriol 2023; 205:e0043822. [PMID: 36847532 PMCID: PMC10029717 DOI: 10.1128/jb.00438-22] [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] [Indexed: 03/01/2023] Open
Abstract
Bacterial conjugation, a form of horizontal gene transfer, relies on a type 4 secretion system (T4SS) and a set of nonstructural genes that are closely linked. These nonstructural genes aid in the mobile lifestyle of conjugative elements but are not part of the T4SS apparatus for conjugative transfer, such as the membrane pore and relaxosome, or the plasmid maintenance and replication machineries. While these nonstructural genes are not essential for conjugation, they assist in core conjugative functions and mitigate the cellular burden on the host. This review compiles and categorizes known functions of nonstructural genes by the stage of conjugation they modulate: dormancy, transfer, and new host establishment. Themes include establishing a commensalistic relationship with the host, manipulating the host for efficient T4SS assembly and function and assisting in conjugative evasion of recipient cell immune functions. These genes, taken in a broad ecological context, play important roles in ensuring proper propagation of the conjugation system in a natural environment.
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Affiliation(s)
- Matthew B. Cooke
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Christophe Herman
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
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4
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Seo PW, Hofmann A, Kim JH, Hwangbo SA, Kim JH, Kim JW, Huynh TYL, Choy HE, Kim SJ, Lee J, Lee JO, Jin KS, Park SY, Kim JS. Structural features of a minimal intact methyltransferase of a type I restriction-modification system. Int J Biol Macromol 2022; 208:381-389. [PMID: 35337914 DOI: 10.1016/j.ijbiomac.2022.03.115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/16/2022] [Accepted: 03/17/2022] [Indexed: 11/05/2022]
Abstract
Type I restriction-modification enzymes are oligomeric proteins composed of methylation (M), DNA sequence-recognition (S), and restriction (R) subunits. The different bipartite DNA sequences of 2-4 consecutive bases are recognized by two discerned target recognition domains (TRDs) located at the two-helix bundle of the two conserved regions (CRs). Two M-subunits and a single S-subunit form an oligomeric protein that functions as a methyltransferase (M2S1 MTase). Here, we present the crystal structure of the intact MTase from Vibrio vulnificus YJ016 in complex with the DNA-mimicking Ocr protein and the S-adenosyl-L-homocysteine (SAH). This MTase includes the M-domain with a helix tail (M-tail helix) and the S1/2-domain of a TRD and a CR α-helix. The Ocr binds to the cleft of the TRD surface and SAH is located in the pocket within the M-domain. The solution- and negative-staining electron microscopy-based reconstructed (M1S1/2)2 structure reveals a symmetric (S1/2)2 assembly using two CR-helices and two M-tail helices as a pivot, which is plausible for recognizing two DNA regions of same sequence. The conformational flexibility of the minimal M1S1/2 MTase dimer indicates a particular state resembling the structure of M2S1 MTases.
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Affiliation(s)
- Pil-Won Seo
- Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Andreas Hofmann
- Department of Veterinary Biosciences, Melbourne Veterinary School, The University of Melbourne, Parkville, Victoria 3010, Australia; Max Rubner-Institut, Federal Research Institute of Nutrition and Food, 95326 Kulmbach, Germany
| | - Jun-Ha Kim
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea; Department of Chemical Engineering, Kumoh National Institute of Technology, 61, Daehak-ro, Gumi, Gyeongbuk 39177, Republic of Korea
| | - Seung-A Hwangbo
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea; Department of Life Sciences and Institute of Membrane Proteins, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Jun-Hong Kim
- Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Ji-Won Kim
- Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Thi Yen Ly Huynh
- Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Hyon E Choy
- Department of Microbiology, Basic Medical Research Building, Chonnam National University Medical College, Hwasun, Jeonnam 58128, Republic of Korea
| | - Soo-Jung Kim
- Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Jimin Lee
- Department of Life Sciences and Institute of Membrane Proteins, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Jie-Oh Lee
- Department of Life Sciences and Institute of Membrane Proteins, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Kyeong Sik Jin
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea.
| | - Suk-Youl Park
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea.
| | - Jeong-Sun Kim
- Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea.
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The plasmid-encoded transcription factor ArdK contributes to the repression of the IMP-6 metallo-β-lactamase gene blaIMP-6, leading to a carbapenem-susceptible phenotype in the blaIMP-6-positive Escherichia coli strain A56-1S. PLoS One 2018; 13:e0208976. [PMID: 30533034 PMCID: PMC6289460 DOI: 10.1371/journal.pone.0208976] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 11/28/2018] [Indexed: 01/04/2023] Open
Abstract
Carbapenemase-producing Enterobacteriaceae (CPE) are a global concern because these bacteria are resistant to almost all β-lactams. Horizontal interspecies gene transfer via plasmid conjugation has increased the global dissemination of CPE. Recently, an Enterobacteriaceae strain positive for carbapenemase gene but showing a carbapenem-susceptible phenotype was identified, suggesting that these susceptible strains may be challenging to detect solely via antimicrobial susceptibility tests without molecular analysis. Here, we isolated a blaIMP-6 carbapenemase-gene positive but imipenem- and meropenem-susceptible Escherichia coli (ISMS-E) strain A56-1S (imipenem and meropenem minimum inhibitory concentration, ≤ 0.125 mg/L), from a human urine specimen in Japan. A56-1S was carbapenemase negative by the Carba NP test, suggesting that IMP-6 production was low or undetectable. Thus, to characterize the mechanism of this phenotype, a meropenem-resistant E. coli A56-1R strain was obtained using meropenem-selection. A56-1R was positive for carbapenemase production by the Carba NP test, and blaIMP-6 transcription in A56-1R was 53-fold higher than in A56-1S, indicating that blaIMP-6 in A56-1S is negatively regulated at the transcriptional level. Comparative genomic analysis between the two strains revealed that the alleviation of restriction of DNA (ardK) gene encoding a putative transcription factor is disrupted by the IS26 insertion in A56-1R. A cotransformation assay of ardK and the regulatory element upstream of blaIMP-6 showed repression of blaIMP-6 transcription, indicating that ArdK negatively modulates blaIMP-6 transcription. ArdK binding and affinity assays demonstrated that ArdK directly binds to the regulatory element upstream of blaIMP-6 with dissociation constant values comparable to those of general transcription factors. The IMP-6 carbapenemase showed low hydrolytic activity against imipenem, resulting in an imipenem-susceptible and meropenem-resistant (ISMR) phenotype (previously reported as a stealth phenotype). However, the low expression of IMP-6 in the A56-1S strain could be a typical characteristic of ISMS-E due to gene repression, indicating that conventional antimicrobial susceptibility tests might be unable to detect such strains even when using both imipenem and meropenem. Bacteria that exhibit the ISMS phenotype could play a potential role as undetectable reservoirs and might facilitate gene transfer to other organisms while avoiding detection.
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6
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Novel R-plasmid conjugal transfer inhibitory and antibacterial activities of phenolic compounds from Mallotus philippensis (Lam.) Mull. Arg. J Glob Antimicrob Resist 2016; 5:15-21. [DOI: 10.1016/j.jgar.2016.01.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 12/17/2015] [Accepted: 01/22/2016] [Indexed: 11/22/2022] Open
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7
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Shah S, Heddle JG. Squaring up to DNA: pentapeptide repeat proteins and DNA mimicry. Appl Microbiol Biotechnol 2014; 98:9545-60. [PMID: 25343976 DOI: 10.1007/s00253-014-6151-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 10/08/2014] [Accepted: 10/09/2014] [Indexed: 02/01/2023]
Abstract
Pentapeptide repeats are a class of proteins characterized by the presence of multiple repeating sequences five amino acids in length. The sequences fold into a right-handed β-helix with a roughly square-shaped cross section. Pentapeptide repeat proteins include a number of examples which are thought to function as structural mimics of DNA and act to competitively bind to the type II topoisomerase DNA gyrase, an important antibacterial target. DNA gyrase-targeting pentapeptide repeat proteins can both inhibit DNA gyrase-a potentially useful therapeutic property-and contribute to resistance to quinolone antibacterials (by acting to prevent them forming a lethal complex with the DNA and enzyme). Pentapeptide repeat proteins are therefore of wide interest not only because of their unusual structure, function, and potential as an antibacterial target, but also because knowledge of their mechanism of action may lead to both a greater understanding of the details of DNA gyrase function as well as being a useful template for the design of new DNA gyrase inhibitors. However, many puzzling aspects as to how these DNA mimics function and indeed even their ability to act as DNA mimics itself remains open to question. This review summarizes the current state of knowledge regarding pentapeptide repeat proteins, focusing on those that are thought to mimic DNA, and speculates on potential structure-function relationships which may account for their differing specificities.
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Affiliation(s)
- Shama Shah
- Heddle Initiative Research Unit, RIKEN, 2-1, Hirosawa, Wako, Saitama, 351-0198, Japan
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8
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Dolejska M, Villa L, Hasman H, Hansen L, Carattoli A. Characterization of IncN plasmids carrying blaCTX-M-1 and qnr genes in Escherichia coli and Salmonella from animals, the environment and humans. J Antimicrob Chemother 2012; 68:333-9. [DOI: 10.1093/jac/dks387] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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9
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Moya A, Gil R, Latorre A, Peretó J, Pilar Garcillán-Barcia M, de la Cruz F. Toward minimal bacterial cells: evolution vs. design. FEMS Microbiol Rev 2009; 33:225-35. [PMID: 19067748 PMCID: PMC7189813 DOI: 10.1111/j.1574-6976.2008.00151.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Revised: 09/29/2008] [Accepted: 10/24/2008] [Indexed: 02/05/2023] Open
Abstract
Recent technical and conceptual advances in the biological sciences opened the possibility of the construction of newly designed cells. In this paper we review the state of the art of cell engineering in the context of genome research, paying particular attention to what we can learn on naturally reduced genomes from either symbiotic or free living bacteria. Different minimal hypothetically viable cells can be defined on the basis of several computational and experimental approaches. Projects aiming at simplifying living cells converge with efforts to make synthetic genomes for minimal cells. The panorama of this particular view of synthetic biology lead us to consider the use of defined minimal cells to be applied in biomedical, bioremediation, or bioenergy application by taking advantage of existing naturally minimized cells.
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Affiliation(s)
- Andrés Moya
- Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, València, Spain.
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Nekrasov SV, Agafonova OV, Belogurova NG, Delver EP, Belogurov AA. Plasmid-encoded antirestriction protein ArdA can discriminate between type I methyltransferase and complete restriction-modification system. J Mol Biol 2006; 365:284-97. [PMID: 17069852 DOI: 10.1016/j.jmb.2006.09.087] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 09/25/2006] [Accepted: 09/27/2006] [Indexed: 10/24/2022]
Abstract
Many promiscuous plasmids encode the antirestriction proteins ArdA (alleviation of restriction of DNA) that specifically affect the restriction activity of heterooligomeric type I restriction-modification (R-M) systems in Escherichia coli cells. In addition, a lot of the putative ardA genes encoded by plasmids and bacterial chromosomes are found as a result of sequencing of complete genomic sequences, suggesting that ArdA proteins and type I R-M systems that seem to be widespread among bacteria may be involved in the regulation of gene transfer among bacterial genomes. Here, the mechanism of antirestriction action of ArdA encoded by IncI plasmid ColIb-P9 has been investigated in comparison with that of well-studied T7 phage-encoded antirestriction protein Ocr using the mutational analysis, retardation assay and His-tag affinity chromatography. Like Ocr, ArdA protein was shown to be able to efficiently interact with EcoKI R-M complex and affect its in vivo and in vitro restriction activity by preventing its interaction with specific DNA. However, unlike Ocr, ArdA protein has a low binding affinity to EcoKI Mtase and the additional C-terminal tail region (VF-motif) is needed for ArdA to efficiently interact with the type I R-M enzymes. It seems likely that this ArdA feature is a basis for its ability to discriminate between activities of EcoKI Mtase (modification) and complete R-M system (restriction) which may interact with unmodified DNA in the cells independently. These findings suggest that ArdA may provide a very effective and delicate control for the restriction and modification activities of type I systems and its ability to discriminate against DNA restriction in favour of the specific modification of DNA may give some advantage for efficient transmission of the ardA-encoding promiscuous plasmids among different bacterial populations.
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Affiliation(s)
- Sergei V Nekrasov
- Department of Genetic Engineering, National Cardiology Research and Development Center, Moscow 121552, Russia
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11
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Thomas CM, Nielsen KM. Mechanisms of, and barriers to, horizontal gene transfer between bacteria. Nat Rev Microbiol 2005; 3:711-21. [PMID: 16138099 DOI: 10.1038/nrmicro1234] [Citation(s) in RCA: 1221] [Impact Index Per Article: 64.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bacteria evolve rapidly not only by mutation and rapid multiplication, but also by transfer of DNA, which can result in strains with beneficial mutations from more than one parent. Transformation involves the release of naked DNA followed by uptake and recombination. Homologous recombination and DNA-repair processes normally limit this to DNA from similar bacteria. However, if a gene moves onto a broad-host-range plasmid it might be able to spread without the need for recombination. There are barriers to both these processes but they reduce, rather than prevent, gene acquisition.
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Affiliation(s)
- Christopher M Thomas
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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12
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Thomas AT, Brammar WJ, Wilkins BM. Plasmid R16 ArdA protein preferentially targets restriction activity of the type I restriction-modification system EcoKI. J Bacteriol 2003; 185:2022-5. [PMID: 12618468 PMCID: PMC150139 DOI: 10.1128/jb.185.6.2022-2025.2003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ArdA antirestriction protein of the IncB plasmid R16 selectively inhibited the restriction activity of EcoKI, leaving significant levels of modification activity under conditions in which restriction was almost completely prevented. The results are consistent with the hypothesis that ArdA functions in bacterial conjugation to allow an unmodified plasmid to evade restriction in the recipient bacterium and yet acquire cognate modification.
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Affiliation(s)
- Angela T Thomas
- Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom
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13
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Affiliation(s)
- Brian M Wilkins
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK.
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14
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15
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Meima R, Lidstrom ME. Characterization of the minimal replicon of a cryptic Deinococcus radiodurans SARK plasmid and development of versatile Escherichia coli-D. radiodurans shuttle vectors. Appl Environ Microbiol 2000; 66:3856-67. [PMID: 10966401 PMCID: PMC92231 DOI: 10.1128/aem.66.9.3856-3867.2000] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nucleotide sequence of a 12-kb fragment of the cryptic Deinococcus radiodurans SARK plasmid pUE10 was determined, in order to direct the development of small, versatile cloning systems for Deinococcus. Annotation of the sequence revealed 12 possible open reading frames. Among these are the repU and resU genes, the predicted products of which share similarity with replication proteins and site-specific resolvases, respectively. The products of both genes were demonstrated using an overexpression system in Escherichia coli. RepU was found to be required for replication, and ResU was found to be required for stable maintenance of pUE10 derivatives. Gel shift analysis using purified His-tagged RepU identified putative binding sites and suggested that RepU may be involved in both replication initiation and autoregulation of repU expression. In addition, a gene encoding a possible antirestriction protein was found, which was shown to be required for high transformation frequencies. The arrangement of the replication region and putative replication genes for this plasmid from D. radiodurans strain SARK is similar to that for plasmids found in Thermus but not to that for the 45.7-kb plasmid found in D. radiodurans strain R1. The minimal region required for autonomous replication in D. radiodurans was determined by sequential deletion of segments from the 12-kb fragment. The resulting minimal replicon, which consists of approximately 2.6 kb, was used for the construction of a shuttle vector for E. coli and D. radiodurans. This vector, pRAD1, is a convenient general-purpose cloning vector. In addition, pRAD1 was used to generate a promoter probe vector, and a plasmid containing lacZ and a Deinococcus promoter was shown to efficiently express LacZ.
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Affiliation(s)
- R Meima
- Departments of Chemical Engineering, University of Washington, Seattle, Washington 98195-1750, USA
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16
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Murray NE. Type I restriction systems: sophisticated molecular machines (a legacy of Bertani and Weigle). Microbiol Mol Biol Rev 2000; 64:412-34. [PMID: 10839821 PMCID: PMC98998 DOI: 10.1128/mmbr.64.2.412-434.2000] [Citation(s) in RCA: 323] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Restriction enzymes are well known as reagents widely used by molecular biologists for genetic manipulation and analysis, but these reagents represent only one class (type II) of a wider range of enzymes that recognize specific nucleotide sequences in DNA molecules and detect the provenance of the DNA on the basis of specific modifications to their target sequence. Type I restriction and modification (R-M) systems are complex; a single multifunctional enzyme can respond to the modification state of its target sequence with the alternative activities of modification or restriction. In the absence of DNA modification, a type I R-M enzyme behaves like a molecular motor, translocating vast stretches of DNA towards itself before eventually breaking the DNA molecule. These sophisticated enzymes are the focus of this review, which will emphasize those aspects that give insights into more general problems of molecular and microbial biology. Current molecular experiments explore target recognition, intramolecular communication, and enzyme activities, including DNA translocation. Type I R-M systems are notable for their ability to evolve new specificities, even in laboratory cultures. This observation raises the important question of how bacteria protect their chromosomes from destruction by newly acquired restriction specifities. Recent experiments demonstrate proteolytic mechanisms by which cells avoid DNA breakage by a type I R-M system whenever their chromosomal DNA acquires unmodified target sequences. Finally, the review will reflect the present impact of genomic sequences on a field that has previously derived information almost exclusively from the analysis of bacteria commonly studied in the laboratory.
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Affiliation(s)
- N E Murray
- Institute of Cell and Molecular Biology, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom.
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Belogurov AA, Delver EP, Agafonova OV, Belogurova NG, Lee LY, Kado CI. Antirestriction protein Ard (Type C) encoded by IncW plasmid pSa has a high similarity to the "protein transport" domain of TraC1 primase of promiscuous plasmid RP4. J Mol Biol 2000; 296:969-77. [PMID: 10686096 DOI: 10.1006/jmbi.1999.3493] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The IncW plasmid pSa contains the gene ard encoding an antirestriction function that is specific for type I restriction and modification systems. The nucleotide sequence of ard was determined and an appropriate polypeptide of about 33 kDa was identified in Escherichia coli T7 expression system. Analysis of deduced amino acid sequence of Ard encoded by pSa revealed that this protein has no significant similarities with the known Ard proteins (ArdA and ArdB types) except the "antirestriction" motif (14 amino acid residues in length) conserved for all known Ard proteins. This finding suggests that pSa Ard may be classified as a new type of Ard proteins which we designated ArdC. The remarkable feature of ArdC is that it has a high degree of similarity (about 38 % identity) to the N-terminal region of RP4 TraC1 primase which includes about 300 amino acid residues and seems to be essential for binding to the single-stranded DNA and TraC1 protein transport to the recipient cells during the conjugal transfer of plasmid DNA. ArdC also binds to single-stranded DNA. In addition, this protein is able in vitro to protect the single-stranded but not double-stranded plasmid DNA against the activity of type II restriction endonuclease HhaI that cleaves both single and double-stranded DNA. We suggest that like TraC1, ArdC would be transported as a result of their interaction with the single-stranded DNA of transferred plasmid strand during conjugative passage through the cell envelope to the recipient bacterium. Such properties of ArdC protein might be useful to protect immediately the incoming single-stranded DNA from the host endonucleases.
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Affiliation(s)
- A A Belogurov
- Department of Genetic Engineering, National Cardiological Research and Development Center, Moscow, 121552, Russia.
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18
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19
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García LR, Molineux IJ. Translocation and specific cleavage of bacteriophage T7 DNA in vivo by EcoKI. Proc Natl Acad Sci U S A 1999; 96:12430-5. [PMID: 10535939 PMCID: PMC22939 DOI: 10.1073/pnas.96.22.12430] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Infection of Escherichia coli containing the type I restriction enzyme EcoKI by bacteriophage T7 0.3 mutants leads to restriction during the late stages of genome entry and during DNA replication. Patterns of cleavage in vivo suggest that some cutting occurs near the midpoint of two recognition sites, consistent with the idea that EcoKI translocates DNA bidirectionally through itself and cuts when two enzyme molecules collide. Rapid ejection of a 0.3(+) T7 genome from a bacteriophage lambda particle results in degradation of the infecting DNA by EcoKI, showing that the normal T7 DNA translocation process delays restriction. A unique recognition site inserted at the genomic left end allows EcoKI to function as a molecular motor and to translocate the remaining 39 kilobases of T7 DNA into the cell.
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Affiliation(s)
- L R García
- Department of Microbiology, Institute for Cell and Molecular Biology, University of Texas, Austin, TX 78712-1095, USA
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20
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Venderbure C, Chastanet A, Boudsocq F, Sommer S, Bailone A. Inhibition of homologous recombination by the plasmid MucA'B complex. J Bacteriol 1999; 181:1249-55. [PMID: 9973352 PMCID: PMC93503 DOI: 10.1128/jb.181.4.1249-1255.1999] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
By its functional interaction with a RecA polymer, the mutagenic UmuD'C complex possesses an antirecombination activity. We show here that MucA'B, a functional homolog of the UmuD'C complex, inhibits homologous recombination as well. In F- recipients expressing MucA'B from a Ptac promoter, Hfr x F- recombination decreased with increasing MucA'B concentrations down to 50-fold. In damage-induced pKM101-containing cells expressing MucA'B from the native promoter, recombination between a UV-damaged F lac plasmid and homologous chromosomal DNA decreased 10-fold. Overexpression of MucA'B together with UmuD'C resulted in a synergistic inhibition of recombination. RecA[UmuR] proteins, which are resistant to UmuD'C inhibition of recombination, are inhibited by MucA'B while promoting MucA'B-promoted mutagenesis efficiently. The data suggest that MucA'B and UmuD'C contact a RecA polymer at distinct sites. The MucA'B complex was more active than UmuD'C in promoting UV mutagenesis, yet it did not inhibit recombination more than UmuD'C does. The enhanced mutagenic potential of MucA'B may result from its inherent superior capacity to assist DNA polymerase in trans-lesion synthesis. In the course of this work, we found that the natural plasmid pKM101 expresses around 45,000 MucA and 13,000 MucB molecules per lexA(Def) cell devoid of LexA. These molecular Muc concentrations are far above those of the chromosomally encoded Umu counterparts. Plasmid pKM101 belongs to a family of broad-host-range conjugative plasmids. The elevated levels of the Muc proteins might be required for successful installation of pKM101-like plasmids into a variety of host cells.
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Affiliation(s)
- C Venderbure
- Institut Curie, Centre Universitaire, F-91405 Orsay, France
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21
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Backert S, Kunnimalaiyaan M, Börner T, Nielsen BL. In vitro replication of mitochondrial plasmid mp1 from the higher plant Chenopodium album (L.): a remnant of bacterial rolling circle and conjugative plasmids? J Mol Biol 1998; 284:1005-15. [PMID: 9837722 DOI: 10.1006/jmbi.1998.2254] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
According to the endosymbiotic theory, mitochondrial genomes evolved from the chromosome of an alpha-proteobacterium-like ancestor and developed during evolution an extraordinary variation in size, structure and replication. We studied in vitro DNA replication of the mitochondrial circular plasmid mp1 (1309 bp) from the higher plant Chenopodium album (L.) as a model system that replicates in a manner reminiscent of bacterial rolling circle plasmids. Several mp1 subclones were tested for their ability to support DNA replication using a newly developed in vitro system. Neutral/neutral two-dimensional gel electrophoresis of the in vitro products revealed typical simple Y patterns of intermediates consistent with a rolling circle type of replication. Replication activity was very high for a BamHI-restricted total plasmid DNA clone, a 464 bp BamHI/KpnI fragment and a 363 bp BamHI/SmaI fragment. Further subcloning of a 148 bp BamHI/EcoRI fragment resulted in the strongest in vitro DNA replication activity, while a 1161 bp-template outside of this region resulted in a substantial loss of activity. Electron microscopic studies of in vitro DNA replication products from the highly active clones also revealed sigma-shaped molecules. These results support our in vivo data for the presence of a predominant replication origin between positions 628 and 776 on the plasmid map. This sequence shares homology with double-stranded rolling circle origin (dso) or transfer origin (oriT) nicking motifs from bacterial plasmids. mp1 is the first described rolling circle plasmid in eukaryotes.
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MESH Headings
- Base Sequence
- Chenopodiaceae/genetics
- Chenopodiaceae/metabolism
- Conjugation, Genetic
- DNA Replication
- DNA, Bacterial/biosynthesis
- DNA, Circular/biosynthesis
- DNA, Mitochondrial/biosynthesis
- DNA, Mitochondrial/genetics
- DNA, Mitochondrial/ultrastructure
- DNA, Plant/biosynthesis
- DNA, Plant/genetics
- DNA, Plant/ultrastructure
- Microscopy, Electron
- Plasmids/biosynthesis
- Plasmids/genetics
- Plasmids/ultrastructure
- Replication Origin
- Restriction Mapping
- Sequence Homology, Nucleic Acid
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Affiliation(s)
- S Backert
- Department of Botany and Microbiology, Auburn University, 101 Life Sciences Building, Auburn, AL, 36849, USA.
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22
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Rastorguev SM, Zavilgelsky GB, Tchurikov NA. IncI1 plasmid R64 encodes the ArsR protein that alleviates type I restriction. FEBS Lett 1998; 426:21-3. [PMID: 9598970 DOI: 10.1016/s0014-5793(98)00285-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The host-controlled EcoK restriction of unmodified phage lambda was five-fold alleviated in the wild-type Escherichia coli strain K12 carrying the R64 plasmid of the incompatibility group I1. The relevant gene was mapped between the origin of vegetative replication (rep, oriV) and the tet(r) gene about 60 kbp downstream from the origin of transfer, oriT. We cloned this gene inside the 613 bp long EcoRI-PstI fragment and sequenced it. Only one 351 bp long open reading frame (ORF) starting at 124 bp from the beginning of the insert was found in the sequence. Computer search in the current databases revealed that the putative protein is identical to the ArsR protein specified by the IncFI plasmid R773. ArsR is a repressor of the arsenical resistance (ars) operon, arsRDABC. There are no arsABC genes in the R64 plasmid since plasmid R64- (or pSR8)-mediated resistance of E. coli K12 cells to the arsenicals arsenate and arsenite was not detected. The gene arsR and the antirestriction genes ard (ardA and ardB) are non-homologous. However, comparison of the deduced amino acid sequence of ArsR with the ArdA and ArdB sequences revealed only one small region of similarity, a 9 amino acid motif found in different antirestriction proteins that is hypothesized to be an interaction site for antirestriction proteins with restriction endonucleases.
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Affiliation(s)
- S M Rastorguev
- State Scientific Centre of Russian Federation GNIIGENETIKA, Moscow
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23
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Delver EP, Belogurov AA. Organization of the leading region of IncN plasmid pKM101 (R46): a regulation controlled by CUP sequence elements. J Mol Biol 1997; 271:13-30. [PMID: 9300052 DOI: 10.1006/jmbi.1997.1124] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Analysis of the nucleotide sequence of the 13.8 kb leading region of the IncN plasmid pKM101 (a deletion derivative of R46) revealed eight copies of highly conserved repetitive elements, CUP (Conserved UPstream), and at least nine novel open reading frames (ORFs). Appropriate protein products were identified for eight ORFs and the analysis of their deduced amino acid sequences revealed similarities with some well-known proteins (KorA of RK2/RP4, RecX and PsiB) that may play a role in the adaptation of promiscuous plasmids to the new host. Comparison of CUP elements revealed that the CUP core is 417 nucleotides long and consists of two portions that markedly differ in GC content. The larger portion (307 nucleotides) of the core is about 74% GC and contains at least one NotI site, while the other (110 nucleotides) is only about 40% GC. The remarkable features of CUP elements is that five of them are oriented in the same direction and fused in a similar mode to the open reading frames (ORFs) that are able to encode unrelated proteins. The spacings between the right boundary of the CUP core and the potential ATG start codons of these ORFs are slightly different in length (16 to 18 bp), highly divergent in sequence but in all cases contain the conserved hexamer 5'-AGGAGT-3' at the position that is typical for the ribosome binding site of Escherichia coli. The A+T-rich portion of the CUP sequences contains the strong negatively regulated promoter and appears to function as a genetic switch that coordinately controls the expression of CUP-fused genes during the conjugal transfer. These findings suggest that seven plasmid genes fused to the CUP elements including repA and two ard genes encoding positively acting replication protein and antirestriction proteins, respectively, may be members of one regulatory network based on the CUP elements and two plasmid-encoded regulatory proteins ArdK and ArdR. At least, the ArdK protein may act as a typical repressor by binding to the promoter region of the CUP sequence. Most of the structural and functional features of organization of the CUP-controlled regulatory network are associated with the idea that the CUP elements may be involved in the natural genetic engineering process of organizing various functionally related genes in one regulon.
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Affiliation(s)
- E P Delver
- Department of Genetic Engineering, Cardiology Research Center, Moscow, Russia
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24
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Clewell DB, Flannagan SE, Jaworski DD. Unconstrained bacterial promiscuity: the Tn916-Tn1545 family of conjugative transposons. Trends Microbiol 1995; 3:229-36. [PMID: 7648031 DOI: 10.1016/s0966-842x(00)88930-1] [Citation(s) in RCA: 266] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Conjugative transposons are highly ubiquitous elements found throughout the bacterial world. Members of the Tn916-Tn1545 family carry the widely disseminated tetracycline-resistance determinant Tet M, as well as additional resistance genes. They have been found naturally in, or been introduced into, over 50 different species and 24 genera of bacteria. Recent investigations have led to insights into the molecular basis of movement of these interesting mobile elements.
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Affiliation(s)
- D B Clewell
- Dept of Biologic and Materials Sciences, School of Dentistry, School of Medicine, University of Michigan, Ann Arbor 48109, USA
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25
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Belogurov AA, Delver EP. A motif conserved among the type I restriction-modification enzymes and antirestriction proteins: a possible basis for mechanism of action of plasmid-encoded antirestriction functions. Nucleic Acids Res 1995; 23:785-7. [PMID: 7708494 PMCID: PMC306760 DOI: 10.1093/nar/23.5.785] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Antirestriction proteins Ard encoded by some self-transmissible plasmids specifically inhibit restriction by members of all three families of type I restriction-modification (R-M) systems in E.coli. Recently, we have identified the amino acid region, 'antirestriction' domain, that is conserved within different plasmid and phage T7-encoded antirestriction proteins and may be involved in interaction with the type I R-M systems. In this paper we demonstrate that this amino acid sequence shares considerable similarity with a well-known conserved sequence (the Argos repeat) found in the DNA sequence specificity (S) polypeptides of type I systems. We suggest that the presence of these similar motifs in restriction and antirestriction proteins may give a structural basis for their interaction and that the antirestriction action of Ard proteins may be a result of the competition between the 'antirestriction' domains of Ard proteins and the similar conserved domains of the S subunits that are believed to play a role in the subunit assembly of type I R-M systems.
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Affiliation(s)
- A A Belogurov
- Department of Genetic Engineering, Cardiology Research Center, Moscow, Russia
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26
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Larsen MH, Figurski DH. Structure, expression, and regulation of the kilC operon of promiscuous IncP alpha plasmids. J Bacteriol 1994; 176:5022-32. [PMID: 7519596 PMCID: PMC196341 DOI: 10.1128/jb.176.16.5022-5032.1994] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The kil-kor regulon was first identified on the broad-host-range IncP alpha plasmid RK2 by the presence of multiple kil loci (kilA, kilB, kilC, and recently kilE) that are lethal to Escherichia coli host cells in the absence of regulation by kor functions in various combinations. Whereas the kilB operon is required for mating-pair formation during conjugation, the functions encoded by the other kil loci are not known. They are not essential for replication or conjugal transfer, but their coregulation with replication and transfer genes indicates that they are likely to be important for RK2. In this report, we describe molecular and genetic studies on kilC. We determined the nucleotide sequence of the kilC region, which is located between the origin of vegetative replication (oriV) and transposon Tn1 on RK2. Primer extension analysis identified the transcriptional start site and showed that a sequence corresponding to a strong sigma 70 promoter is functional. The abundance of RNA initiated from the kilC promoter is reduced in the presence of korA and korC, as predicted from genetic analysis of kilC regulation. The first gene of the kilC operon (klcA) is sufficient to express the host-lethal phenotype of the kilC determinant in the absence of korA and korC. By comparing RK2 to the related IncP alpha plasmids pUZ8 and R995, we determined that the Tn1 transposon in RK2 interrupts a gene (klcB) immediately downstream of klcA. Thus, the kilC determinant is normally part of an autoregulated operon of three genes: klcA, klcB, and korC. klcA is predicted to encode a 15,856-Da polypeptide that is related to the ArdB antirestriction protein of the IncN plasmid pKM101, suggesting a role for klcA in the broad host ranges of IncP alpha plasmids. The predicted product of the uninterrupted klcB gene is a polypeptide of 51,133 Da that contains a segment with significant similarity to the RK2 regulatory proteins KorA and TrbA. Located 145 bp upstream of the kilC promoter is a 10th copy of the 17-bp oriV iteron sequence in inverted orientation relative to that of the other nine iterons of oriV. Iteron 10 is identical to the "orphan" iteron 1, and both have identical 6-bp flanking sequences that make them likely to be strong binding sites for the TrfA replication initiator protein. The locations and relative orientation of orphan iterons 10 and 1 raise the possibility that these iterons promote the formation of a DNA loop via protein-protein interactions by bound TrfA and lead us to propose that they demarcate the functional origin of replication. This analysis of the kilC region and our previous studies on the other kil loci of RK2 have revealed that the region between oriV and the korABF operon in wild-type IncP alpha plasmids is saturated by the kilC, kilE, and kilA loci arranged in four kor-regulated operons encoding a total of 12 genes.
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Affiliation(s)
- M H Larsen
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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27
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Belogurov AA, Delver EP, Rodzevich OV. Plasmid pKM101 encodes two nonhomologous antirestriction proteins (ArdA and ArdB) whose expression is controlled by homologous regulatory sequences. J Bacteriol 1993; 175:4843-50. [PMID: 8393008 PMCID: PMC204937 DOI: 10.1128/jb.175.15.4843-4850.1993] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The IncN plasmid pKM101 (a derivative of R46) encodes the antirestriction protein ArdB (alleviation of restriction of DNA) in addition to another antirestriction protein, ArdA, described previously. The relevant gene, ardB, was located in the leading region of pKM101, about 7 kb from oriT. The nucleotide sequence of ardB was determined, and an appropriate polypeptide was identified in maxicells of Escherichia coli. Like ArdA, ArdB efficiently inhibits restriction by members of the three known families of type I systems of E. coli and only slightly affects the type II enzyme, EcoRI. However, in contrast to ArdA, ArdB is ineffective against the modification activity of the type I (EcoK) system. Comparison of deduced amino acid sequences of ArdA and ArdB revealed only one small region of similarity (nine residues), suggesting that this region may be somehow involved in the interaction with the type I restriction systems. We also found that the expression of both ardA and ardB genes is controlled jointly by two pKM101-encoded proteins, ArdK and ArdR, with molecular weights of about 15,000 and 20,000, respectively. The finding that the sequences immediately upstream of ardA and ardB share about 94% identity over 218 bp suggests that their expression may be controlled by ArdK and ArdR at the transcriptional level. Deletion studies and promoter probe analysis of these sequences revealed the regions responsible for the action of ArdK and ArdR as regulatory proteins. We propose that both types of antirestriction proteins may play a pivotal role in overcoming the host restriction barrier by self-transmissible broad-host-range plasmids. It seems likely that the ardKR-dependent regulatory system serves in this case as a genetic switch that controls the expression of plasmid-encoded antirestriction functions during mating.
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Affiliation(s)
- A A Belogurov
- Department of Genetic Engineering, National Cardiology Research Center, Moscow, Russia
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28
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Abstract
Our understanding of the evolution of DNA restriction and modification systems, the control of the expression of the structural genes for the enzymes, and the importance of DNA restriction in the cellular economy has advanced by leaps and bounds in recent years. This review documents these advances for the three major classes of classical restriction and modification systems, describes the discovery of a new class of restriction systems that specifically cut DNA carrying the modification signature of foreign cells, and deals with the mechanisms developed by phages to avoid the restriction systems of their hosts.
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Affiliation(s)
- T A Bickle
- Department of Microbiology, Biozentrum, Basel University, Switzerland
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Heitman J. On the origins, structures and functions of restriction-modification enzymes. GENETIC ENGINEERING 1993; 15:57-108. [PMID: 7764063 DOI: 10.1007/978-1-4899-1666-2_4] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J Heitman
- Section of Genetics, Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710
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30
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New nucleotide sequence data on the EMBL File Server. Nucleic Acids Res 1992; 20:6119-40. [PMID: 1461752 PMCID: PMC334492 DOI: 10.1093/nar/20.22.6119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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