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Kirillov A, Morozova N, Kozlova S, Polinovskaya V, Smirnov S, Khodorkovskii M, Zeng L, Ispolatov Y, Severinov K. Cells with stochastically increased methyltransferase to restriction endonuclease ratio provide an entry for bacteriophage into protected cell population. Nucleic Acids Res 2022; 50:12355-12368. [PMID: 36477901 PMCID: PMC9757035 DOI: 10.1093/nar/gkac1124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 10/29/2022] [Accepted: 11/14/2022] [Indexed: 12/13/2022] Open
Abstract
The action of Type II restriction-modification (RM) systems depends on restriction endonuclease (REase), which cleaves foreign DNA at specific sites, and methyltransferase (MTase), which protects host genome from restriction by methylating the same sites. We here show that protection from phage infection increases as the copy number of plasmids carrying the Type II RM Esp1396I system is increased. However, since increased plasmid copy number leads to both increased absolute intracellular RM enzyme levels and to a decreased MTase/REase ratio, it is impossible to determine which factor determines resistance/susceptibility to infection. By controlled expression of individual Esp1396I MTase or REase genes in cells carrying the Esp1396I system, we show that a shift in the MTase to REase ratio caused by overproduction of MTase or REase leads, respectively, to decreased or increased protection from infection. Consistently, due to stochastic variation of MTase and REase amount in individual cells, bacterial cells that are productively infected by bacteriophage have significantly higher MTase to REase ratios than cells that ward off the infection. Our results suggest that cells with transiently increased MTase to REase ratio at the time of infection serve as entry points for unmodified phage DNA into protected bacterial populations.
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Affiliation(s)
- Alexander Kirillov
- Skolkovo Institute of Science and Technology, Center for Molecular and Cellular Biology, Moscow 121205, Russia,Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251, Russia
| | - Natalia Morozova
- Skolkovo Institute of Science and Technology, Center for Molecular and Cellular Biology, Moscow 121205, Russia,Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251, Russia
| | - Svetlana Kozlova
- Skolkovo Institute of Science and Technology, Center for Molecular and Cellular Biology, Moscow 121205, Russia
| | - Vasilisa Polinovskaya
- Skolkovo Institute of Science and Technology, Center for Molecular and Cellular Biology, Moscow 121205, Russia
| | - Sergey Smirnov
- Skolkovo Institute of Science and Technology, Center for Molecular and Cellular Biology, Moscow 121205, Russia
| | - Mikhail Khodorkovskii
- Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251, Russia
| | - Lanying Zeng
- Texas A&M University, Department of Biochemistry and Biophysics, Center for Phage Technology, College Station, TX 77843, USA
| | - Yaroslav Ispolatov
- University of Santiago of Chile (USACH), Physics Department, Av. Víctor Jara 3493, Santiago, Chile
| | - Konstantin Severinov
- To whom correspondence should be addressed. Tel: +7 9854570284; Fax: +1 848 445 5735;
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Chen ZP, Zhang HM, Yang P, Yuan R, Li Y, Liang WB. No-nonspecific recognition-based amplification strategy for endonuclease activity screening with dual-color DNA nano-clew. Biosens Bioelectron 2021; 190:113446. [PMID: 34166945 DOI: 10.1016/j.bios.2021.113446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 06/09/2021] [Accepted: 06/15/2021] [Indexed: 10/21/2022]
Abstract
The inevitable nonspecific recognition severely restricted widely used nucleic acid amplification strategies, which has become an urgent problem in current scientific research. Herein, we developed a novel no-nonspecific recognition-based amplification strategy to construct dual-color dye loaded nano-clew as ultrabright illuminant for screening endonuclease activity with Escherichia coliRY13 I (EcoR I) as a model, which overcame some major drawbacks such as nonspecific recognition and photobleaching. Typically, the target endonuclease induces cleavage of the customized dumbbell-shape substrate (DSS) to generate two same triggers that can initiate the rolling circle amplification (RCA) to prepare long single-strand DNA (lssDNA), which could self-assemble into irregular DNA nano-clew based on the electrostatic interactions with Mg2+ to furtherly capture the donor and accepter fluorophore proximately, constructing the dye loaded nano-clew with dual-color fluorescence (FL) emission to resist photobleaching. Importantly, in absence of EcoR I, even if the DSS could combine with circular template a little, the reaction system performed hardly RCA reaction due to no cohesive terminus, resulting an extremely low background fluorescence signal because of the prevention of nonspecific RCA reaction. As expected, the proposed sensing platform with a low limit of detection (LOD) of 3.4 × 10-7 U/μL was demonstrated to work well for endonuclease inhibitors screening also. Furthermore, the proposed no-nonspecific recognition strategy could be readily extended to various DNA or RNA enzymes such as DNA methyltransferase, DNA repair-related enzymes and polynucleotide kinase just by simply changing the recognition sequence in the DNA substrate, performing great potential of endonucleases-related clinical diagnosis and drugs discovery.
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Affiliation(s)
- Zhao-Peng Chen
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China
| | - Hao-Min Zhang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China
| | - Peng Yang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China
| | - Ruo Yuan
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China
| | - Yan Li
- Department of Clinical and Military Laboratory Medicine, College of Medical Laboratory Science, Army Medical University, Chongqing, 400038, China.
| | - Wen-Bin Liang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China.
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Wilkowska K, Mruk I, Furmanek-Blaszk B, Sektas M. Low-level expression of the Type II restriction-modification system confers potent bacteriophage resistance in Escherichia coli. DNA Res 2021; 27:5804985. [PMID: 32167561 PMCID: PMC7315355 DOI: 10.1093/dnares/dsaa003] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 03/09/2020] [Indexed: 01/21/2023] Open
Abstract
Restriction–modification systems (R–M) are one of the antiviral defense tools used by bacteria, and those of the Type II family are composed of a restriction endonuclease (REase) and a DNA methyltransferase (MTase). Most entering DNA molecules are usually cleaved by the REase before they can be methylated by MTase, although the observed level of fragmented DNA may vary significantly. Using a model EcoRI R–M system, we report that the balance between DNA methylation and cleavage may be severely affected by transcriptional signals coming from outside the R–M operon. By modulating the activity of the promoter, we obtained a broad range of restriction phenotypes for the EcoRI R–M system that differed by up to 4 orders of magnitude in our biological assays. Surprisingly, we found that high expression levels of the R–M proteins were associated with reduced restriction of invading bacteriophage DNA. Our results suggested that the regulatory balance of cleavage and methylation was highly sensitive to fluctuations in transcriptional signals both up- and downstream of the R–M operon. Our data provided further insights into Type II R–M system maintenance and the potential conflict within the host bacterium.
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Affiliation(s)
- Karolina Wilkowska
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
| | - Iwona Mruk
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
| | - Beata Furmanek-Blaszk
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
| | - Marian Sektas
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
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Rezulak M, Borsuk I, Mruk I. Natural C-independent expression of restriction endonuclease in a C protein-associated restriction-modification system. Nucleic Acids Res 2015; 44:2646-60. [PMID: 26656489 PMCID: PMC4824078 DOI: 10.1093/nar/gkv1331] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 11/13/2015] [Indexed: 12/24/2022] Open
Abstract
Restriction-modification (R-M) systems are highly prevalent among bacteria and archaea, and appear to play crucial roles in modulating horizontal gene transfer and protection against phage. There is much to learn about these diverse enzymes systems, especially their regulation. Type II R-M systems specify two independent enzymes: a restriction endonuclease (REase) and protective DNA methyltransferase (MTase). Their activities need to be finely balanced in vivo Some R-M systems rely on specialized transcription factors called C (controller) proteins. These proteins play a vital role in the temporal regulation of R-M gene expression, and function to indirectly modulate the horizontal transfer of their genes across the species. We report novel regulation of a C-responsive R-M system that involves a C protein of a poorly-studied structural class - C.Csp231I. Here, the C and REase genes share a bicistronic transcript, and some of the transcriptional auto-control features seen in other C-regulated R-M systems are conserved. However, separate tandem promoters drive most transcription of the REase gene, a distinctive property not seen in other tested C-linked R-M systems. Further, C protein only partially controls REase expression, yet plays a role in system stability and propagation. Consequently, high REase activity was observed after deletion of the entire C gene, and cells bearing the ΔC R-M system were outcompeted in mixed culture assays by those with the WT R-M system. Overall, our data reveal unexpected regulatory variation among R-M systems.
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Affiliation(s)
- Monika Rezulak
- Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
| | - Izabela Borsuk
- Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
| | - Iwona Mruk
- Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
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Loenen WAM, Dryden DTF, Raleigh EA, Wilson GG, Murray NE. Highlights of the DNA cutters: a short history of the restriction enzymes. Nucleic Acids Res 2014; 42:3-19. [PMID: 24141096 PMCID: PMC3874209 DOI: 10.1093/nar/gkt990] [Citation(s) in RCA: 195] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/24/2013] [Accepted: 10/02/2013] [Indexed: 11/16/2022] Open
Abstract
In the early 1950's, 'host-controlled variation in bacterial viruses' was reported as a non-hereditary phenomenon: one cycle of viral growth on certain bacterial hosts affected the ability of progeny virus to grow on other hosts by either restricting or enlarging their host range. Unlike mutation, this change was reversible, and one cycle of growth in the previous host returned the virus to its original form. These simple observations heralded the discovery of the endonuclease and methyltransferase activities of what are now termed Type I, II, III and IV DNA restriction-modification systems. The Type II restriction enzymes (e.g. EcoRI) gave rise to recombinant DNA technology that has transformed molecular biology and medicine. This review traces the discovery of restriction enzymes and their continuing impact on molecular biology and medicine.
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Affiliation(s)
- Wil A. M. Loenen
- Leiden University Medical Center, Leiden, the Netherlands, EaStChemSchool of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland, UK and New England Biolabs, Inc., 240 County Road, Ipswich, MA 01938, USA
| | - David T. F. Dryden
- Leiden University Medical Center, Leiden, the Netherlands, EaStChemSchool of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland, UK and New England Biolabs, Inc., 240 County Road, Ipswich, MA 01938, USA
| | - Elisabeth A. Raleigh
- Leiden University Medical Center, Leiden, the Netherlands, EaStChemSchool of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland, UK and New England Biolabs, Inc., 240 County Road, Ipswich, MA 01938, USA
| | - Geoffrey G. Wilson
- Leiden University Medical Center, Leiden, the Netherlands, EaStChemSchool of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, Scotland, UK and New England Biolabs, Inc., 240 County Road, Ipswich, MA 01938, USA
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Mruk I, Kobayashi I. To be or not to be: regulation of restriction-modification systems and other toxin-antitoxin systems. Nucleic Acids Res 2013; 42:70-86. [PMID: 23945938 PMCID: PMC3874152 DOI: 10.1093/nar/gkt711] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
One of the simplest classes of genes involved in programmed death is that containing the toxin–antitoxin (TA) systems of prokaryotes. These systems are composed of an intracellular toxin and an antitoxin that neutralizes its effect. These systems, now classified into five types, were initially discovered because some of them allow the stable maintenance of mobile genetic elements in a microbial population through postsegregational killing or the death of cells that have lost these systems. Here, we demonstrate parallels between some TA systems and restriction–modification systems (RM systems). RM systems are composed of a restriction enzyme (toxin) and a modification enzyme (antitoxin) and limit the genetic flux between lineages with different epigenetic identities, as defined by sequence-specific DNA methylation. The similarities between these systems include their postsegregational killing and their effects on global gene expression. Both require the finely regulated expression of a toxin and antitoxin. The antitoxin (modification enzyme) or linked protein may act as a transcriptional regulator. A regulatory antisense RNA recently identified in an RM system can be compared with those RNAs in TA systems. This review is intended to generalize the concept of TA systems in studies of stress responses, programmed death, genetic conflict and epigenetics.
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Affiliation(s)
- Iwona Mruk
- Department of Microbiology, University of Gdansk, Wita Stwosza 59, Gdansk, 80-308, Poland, Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo 108-8639, Japan and Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
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Mruk I, Liu Y, Ge L, Kobayashi I. Antisense RNA associated with biological regulation of a restriction-modification system. Nucleic Acids Res 2011; 39:5622-32. [PMID: 21459843 PMCID: PMC3141266 DOI: 10.1093/nar/gkr166] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Restriction–modification systems consist of a modification enzyme that methylates a specific DNA sequence and a restriction endonuclease that cleaves DNA lacking this epigenetic signature. Their gene expression should be finely regulated because their potential to attack the host bacterial genome needs to be controlled. In the EcoRI system, where the restriction gene is located upstream of the modification gene in the same orientation, we previously identified intragenic reverse promoters affecting gene expression. In the present work, we identified a small (88 nt) antisense RNA (Rna0) transcribed from a reverse promoter (PREV0) at the 3′ end of the restriction gene. Its antisense transcription, as measured by transcriptional gene fusion, appeared to be terminated by the PM1,M2 promoter. PM1,M2 promoter-initiated transcription, in turn, appeared to be inhibited by PREV0. Mutational inactivation of PREV0 increased expression of the restriction gene. The biological significance of this antisense transcription is 2-fold. First, a mutation in PREV0 increased restriction of incoming DNA. Second, the presence of the antisense RNA gene (ecoRIA) in trans alleviated cell killing after loss of the EcoRI plasmid (post-segregational killing). Taken together, these results strongly suggested the involvement of an antisense RNA in the biological regulation of this restriction–modification system.
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Affiliation(s)
- Iwona Mruk
- Department of Microbiology, University of Gdansk, Kladki 24, Gdansk, 80-822, Poland
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Nagornykh M, Zakharova M, Protsenko A, Bogdanova E, Solonin AS, Severinov K. Regulation of gene expression in restriction-modification system Eco29kI. Nucleic Acids Res 2011; 39:4653-63. [PMID: 21310712 PMCID: PMC3113576 DOI: 10.1093/nar/gkr055] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Eco29kI restriction-modification (R-M) system consists of two partially overlapping genes, eco29kIR, encoding a restriction endonuclease and eco29kIM, encoding methyltransferase. The two genes are thought to form an operon with the eco29kIR gene preceding the eco29kIM gene. Such an organization is expected to complicate establishment of plasmids containing this R-M system in naive hosts, since common logic dictates that methyltransferase should be synthesized first to protect the DNA from cleavage by the endonuclease. Here, we characterize the Eco29kI gene transcription. We show that a separate promoter located within the eco29kIR gene is sufficient to synthesize enough methyltransferase to completely modify host DNA. We further show that transcription from two intragenic antisense promoters strongly decreases the levels of eco29kIR gene transcripts. The antisense transcripts act by preventing translation initiation from the bicistronic eco29kIR–eco29kIM mRNA and causing its degradation. Both eco29kIM and antisense promoters are necessary for Eco29kI genes establishment and/or stable maintenance, indicating that they jointly contribute to coordinated expression of Eco29kI genes.
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Affiliation(s)
- Maxim Nagornykh
- Waksman Institute of Microbiology, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA
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Gholizadeh A, Faizi MH, Baghban Kohnehrouz B. Induced expression of EcoRI endonuclease as an active maltose-binding fusion protein in Escherichia coli. Microbiology (Reading) 2010. [DOI: 10.1134/s0026261710020062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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10
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Mruk I, Blumenthal RM. Tuning the relative affinities for activating and repressing operators of a temporally regulated restriction-modification system. Nucleic Acids Res 2009; 37:983-98. [PMID: 19126580 PMCID: PMC2647307 DOI: 10.1093/nar/gkn1010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Most type II restriction-modification (R-M) systems produce separate endonuclease (REase) and methyltransferase (MTase) proteins. After R-M genes enter a new cell, MTase activity must appear before REase or the host chromosome will be cleaved. Temporal control of these genes thus has life-or-death consequences. PvuII and some other R-M systems delay endonuclease expression by cotranscribing the REase gene with the upstream gene for an autogenous activator/repressor (C protein). C.PvuII was previously shown to have low levels early, but positive feedback later boosts transcription of the C and REase genes. The MTase is expressed without delay, and protects the host DNA. C.PvuII binds to two sites upstream of its gene: OL, associated with activation, and OR, associated with repression. Even when symmetry elements of each operator are made identical, C.PvuII binds preferentially to OL. In this study, the intra-operator spacers are shown to modulate relative C.PvuII affinity. In light of a recently reported C.Esp1396I-DNA co-crystal structure, in vitro and in vivo effects of altering OL and OR spacers were determined. The results suggest that the GACTnnnAGTC consensus is the primary determinant of C.PvuII binding affinity, with intra-operator spacers playing a fine-tuning role that affects mobility of this R-M system.
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Affiliation(s)
- Iwona Mruk
- Department of Medical Microbiology and Immunology, University of Toledo Health Sciences Campus, Toledo, OH 43614-2598, USA
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Mruk I, Blumenthal RM. Real-time kinetics of restriction-modification gene expression after entry into a new host cell. Nucleic Acids Res 2008; 36:2581-93. [PMID: 18334533 PMCID: PMC2377437 DOI: 10.1093/nar/gkn097] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Most type II restriction-modification (R-M) systems produce separate restriction endonuclease (REase) and methyltransferase (MTase) proteins. After R-M system genes enter a new cell, protective MTase must appear before REase to avoid host chromosome cleavage. The basis for this apparent temporal regulation is not well understood. PvuII and some other R-M systems appear to achieve this delay by cotranscribing the REase gene with the gene for an autogenous transcription activator/repressor (the 'C' protein C.PvuII). To test this model, bacteriophage M13 was used to introduce the PvuII genes into a bacterial population in a relatively synchronous manner. REase mRNA and activity appeared approximately 10 min after those of the MTase, but never rose if there was an inactivating pvuIIC mutation. Infection with recombinant M13pvuII phage had little effect on cell growth, relative to infection with parental M13. However, infection of cells pre-expressing C.PvuII led to cessation of growth. This study presents the first direct demonstration of delayed REase expression, relative to MTase, when type II R-M genes enter a new host cell. Surprisingly, though the C and REase genes are cotranscribed, the pvuIIC portion of the mRNA was more abundant than the pvuIIR portion after stable establishment of the R-M system.
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Affiliation(s)
- Iwona Mruk
- Department of Medical Microbiology and Immunology, University of Toledo Health Sciences Campus, Toledo, OH 43614-2598, USA.
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Ohno S, Handa N, Watanabe-Matsui M, Takahashi N, Kobayashi I. Maintenance forced by a restriction-modification system can be modulated by a region in its modification enzyme not essential for methyltransferase activity. J Bacteriol 2008; 190:2039-49. [PMID: 18192396 PMCID: PMC2258900 DOI: 10.1128/jb.01319-07] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Accepted: 01/02/2008] [Indexed: 11/20/2022] Open
Abstract
Several type II restriction-modification gene complexes can force their maintenance on their host bacteria by killing cells that have lost them in a process called postsegregational killing or genetic addiction. It is likely to proceed by dilution of the modification enzyme molecule during rounds of cell division following the gene loss, which exposes unmethylated recognition sites on the newly replicated chromosomes to lethal attack by the remaining restriction enzyme molecules. This process is in apparent contrast to the process of the classical types of postsegregational killing systems, in which built-in metabolic instability of the antitoxin allows release of the toxin for lethal action after the gene loss. In the present study, we characterize a mutant form of the EcoRII gene complex that shows stronger capacity in such maintenance. This phenotype is conferred by an L80P amino acid substitution (T239C nucleotide substitution) mutation in the modification enzyme. This mutant enzyme showed decreased DNA methyltransferase activity at a higher temperature in vivo and in vitro than the nonmutated enzyme, although a deletion mutant lacking the N-terminal 83 amino acids did not lose activity at either of the temperatures tested. Under a condition of inhibited protein synthesis, the activity of the L80P mutant was completely lost at a high temperature. In parallel, the L80P mutant protein disappeared more rapidly than the wild-type protein. These results demonstrate that the capability of a restriction-modification system in forcing maintenance on its host can be modulated by a region of its antitoxin, the modification enzyme, as in the classical postsegregational killing systems.
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Affiliation(s)
- Satona Ohno
- Department of Medical Genome Sciences, Graduate School of Frontier Science and Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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Mruk I, Rajesh P, Blumenthal RM. Regulatory circuit based on autogenous activation-repression: roles of C-boxes and spacer sequences in control of the PvuII restriction-modification system. Nucleic Acids Res 2007; 35:6935-52. [PMID: 17933763 PMCID: PMC2175313 DOI: 10.1093/nar/gkm837] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Type II restriction-modification (R-M) systems comprise a restriction endonuclease (REase) and a protective methyltransferase (MTase). After R-M genes enter a new cell, MTase must appear before REase or the chromosome will be cleaved. PvuII and some other R-M systems achieve this delay by cotranscribing the REase gene with the gene for an autogenous transcription activator (the controlling or 'C' protein C.PvuII). This study reveals, through in vivo titration, that C.PvuII is not only an activator but also a repressor for its own gene. In other systems, this type of circuit can result in oscillatory behavior. Despite the use of identical, symmetrical C protein-binding sequences (C-boxes) in the left and right operators, C.PvuII showed higher in vitro affinity for O(L) than for O(R), implicating the spacer sequences in this difference. Mutational analysis associated the repression with O(R), which overlaps the promoter -35 hexamer but is otherwise dispensable for activation. A nonrepressing mutant exhibited poor establishment in new cells. Comparing promoter-operator regions from PvuII and 29 R-M systems controlled by C proteins revealed that the most-highly conserved sequence is the tetranucleotide spacer separating O(L) from O(R). Any changes in that spacer reduced the stability of C.PvuII-operator complexes and abolished activation.
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Affiliation(s)
- Iwona Mruk
- Department of Medical Microbiology and Immunology, University of Toledo Health Sciences Campus, Toledo, OH 43614-2598, USA
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