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Kopkowski PW, Zhang Z, Saier MH. The effect of DNA-binding proteins on insertion sequence element transposition upstream of the bgl operon in Escherichia coli. Front Microbiol 2024; 15:1388522. [PMID: 38666260 PMCID: PMC11043490 DOI: 10.3389/fmicb.2024.1388522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 03/22/2024] [Indexed: 04/28/2024] Open
Abstract
The bglGFB operon in Escherichia coli K-12 strain BW25113, encoding the proteins necessary for the uptake and metabolism of β-glucosides, is normally not expressed. Insertion of either IS1 or IS5 upstream of the bgl promoter activates expression of the operon only when the cell is starving in the presence of a β-glucoside, drastically increasing transcription and allowing the cell to survive and grow using this carbon source. Details surrounding the exact mechanism and regulation of the IS insertional event remain unclear. In this work, the role of several DNA-binding proteins in how they affect the rate of insertion upstream of bgl are examined via mutation assays and protocols measuring transcription. Both Crp and IHF exert a positive effect on insertional Bgl+ mutations when present, active, and functional in the cell. Our results characterize IHF's effect in conjunction with other mutations, show that IHF's effect on IS insertion into bgl also affects other operons, and indicate that it may exert its effect by binding to and altering the DNA conformation of IS1 and IS5 in their native locations, rather than by directly influencing transposase gene expression. In contrast, the cAMP-CRP complex acts directly upon the bgl operon by binding upstream of the promoter, presumably altering local DNA into a conformation that enhances IS insertion.
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Affiliation(s)
| | - Zhongge Zhang
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Milton H. Saier
- Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
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2
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Targeted Conservative Cointegrate Formation Mediated by IS 26 Family Members Requires Sequence Identity at the Reacting End. mSphere 2021; 6:6/1/e01321-20. [PMID: 33504667 PMCID: PMC7885326 DOI: 10.1128/msphere.01321-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
IS26 forms cointegrates using two distinct routes, a copy-in mechanism involving one insertion sequence (IS) and a target and a targeted conservative mechanism involving two ISs in different DNA molecules. In this study, the ability of IS26 and some close relatives, IS1006, IS1008, and a natural hybrid, IS1006/IS1008, which are found predominantly in Acinetobacter spp., to interact was examined. IS1006/1008 consists of 175 bp from IS1006 at the left end, with the remainder from IS1008. These ISs all have the same 14-bp terminal inverted repeats, and the Tnp26, Tnp1006, and Tnp1008 transposases, with pairwise identities of 83.7% to 93.1%, should be able to recognize each other's ends. In a recA-negative Escherichia coli strain, IS1006, IS1008, and IS1006/1008 each formed cointegrates via the copy-in route and via the targeted conservative route, albeit at frequencies for the targeted reaction at least 10-fold lower than for IS26 However, using mixed pairs, targeted cointegration was detected only when IS1008 was paired with the IS1006/1008 hybrid, which also encodes Tnp1008, and the targeted cointegrates formed all arose from a reaction occurring at the end where the DNA sequences are identical. The reaction also occurred at the end with extended DNA identity using IS26 paired with IS26::catA1, an artificially constructed IS26 derivative that includes the catA1 gene. Thus, both identical transposases and identical DNA sequences at the reacting end were required. These features indicate that the targeted conservative pathway proceeds via a single transposase-catalyzed strand transfer, followed by migration and resolution of the Holliday junction formed.IMPORTANCE The IS26 family includes the ISs that are commonly found associated with antibiotic resistance genes in multiply resistant Gram-negative and Gram-positive bacteria. IS26 is most prevalent in Gram-negative species and can generate the clusters of antibiotic resistance genes interspersed with directly oriented IS26 seen in multiply resistant pathogens. This ability relies on the novel dual mechanistic capabilities of IS26 family members. However, the mechanism underlying the recently discovered targeted conservative mode of cointegrate formation mediated by IS26, IS257/IS431, and IS1216, which is unlike any previously studied IS movement mechanism, is not well understood. An important question is what features of the IS and the transposase are key to allowing IS26 family members to undertake targeted conservative reaction. In this study, this question was addressed using mixed-partner crosses involving IS26 and naturally occurring close relatives of IS26 that are found near resistance genes in Acinetobacter baumannii and are widespread in Acinetobacter species.
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3
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Faure G, Shmakov SA, Yan WX, Cheng DR, Scott DA, Peters JE, Makarova KS, Koonin EV. CRISPR-Cas in mobile genetic elements: counter-defence and beyond. Nat Rev Microbiol 2019; 17:513-525. [PMID: 31165781 PMCID: PMC11165670 DOI: 10.1038/s41579-019-0204-7] [Citation(s) in RCA: 167] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The principal function of CRISPR-Cas systems in archaea and bacteria is defence against mobile genetic elements (MGEs), including viruses, plasmids and transposons. However, the relationships between CRISPR-Cas and MGEs are far more complex. Several classes of MGE contributed to the origin and evolution of CRISPR-Cas, and, conversely, CRISPR-Cas systems and their components were recruited by various MGEs for functions that remain largely uncharacterized. In this Analysis article, we investigate and substantially expand the range of CRISPR-Cas components carried by MGEs. Three groups of Tn7-like transposable elements encode 'minimal' type I CRISPR-Cas derivatives capable of target recognition but not cleavage, and another group encodes an inactivated type V variant. These partially inactivated CRISPR-Cas variants might mediate guide RNA-dependent integration of the respective transposons. Numerous plasmids and some prophages encode type IV systems, with similar predicted properties, that appear to contribute to competition among plasmids and between plasmids and viruses. Many prokaryotic viruses also carry CRISPR mini-arrays, some of which recognize other viruses and are implicated in inter-virus conflicts, and solitary repeat units, which could inhibit host CRISPR-Cas systems.
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Affiliation(s)
- Guilhem Faure
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Sergey A Shmakov
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
- Skolkovo Institute of Science and Technology, Skolkovo, Russia
| | | | | | | | - Joseph E Peters
- Department of Microbiology, Cornell University, Ithaca, NY, USA
| | - Kira S Makarova
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA.
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4
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Abstract
The immune system evolved to distinguish non-self from self to protect the organism. As cancer is derived from our own cells, immune responses to dysregulated cell growth present a unique challenge. This is compounded by mechanisms of immune evasion and immunosuppression that develop in the tumour microenvironment. The modern genetic toolbox enables the adoptive transfer of engineered T cells to create enhanced anticancer immune functions where natural cancer-specific immune responses have failed. Genetically engineered T cells, so-called 'living drugs', represent a new paradigm in anticancer therapy. Recent clinical trials using T cells engineered to express chimeric antigen receptors (CARs) or engineered T cell receptors (TCRs) have produced stunning results in patients with relapsed or refractory haematological malignancies. In this Review we describe some of the most recent and promising advances in engineered T cell therapy with a particular emphasis on what the next generation of T cell therapy is likely to entail.
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MESH Headings
- Antigen Presentation
- Antigens, CD19/immunology
- Antigens, Neoplasm/immunology
- Clinical Trials as Topic
- Costimulatory and Inhibitory T-Cell Receptors/genetics
- Costimulatory and Inhibitory T-Cell Receptors/immunology
- Cytokines/metabolism
- Forecasting
- Gene Editing
- Gene Transfer Techniques
- Genetic Engineering
- HLA Antigens/immunology
- Hematologic Neoplasms/immunology
- Hematologic Neoplasms/therapy
- Humans
- Immunotherapy, Adoptive/adverse effects
- Immunotherapy, Adoptive/methods
- Immunotherapy, Adoptive/trends
- Models, Immunological
- Neoplasms/immunology
- Neoplasms/therapy
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/immunology
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/immunology
- Syndrome
- T-Cell Antigen Receptor Specificity
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/transplantation
- Tumor Escape
- Tumor Microenvironment/immunology
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Affiliation(s)
- Andrew D Fesnak
- Department of Pathology and Laboratory Medicine and Center for Cellular Immunotherapies, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-5156, USA
| | - Carl H June
- Department of Pathology and Laboratory Medicine and Center for Cellular Immunotherapies, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-5156, USA
| | - Bruce L Levine
- Department of Pathology and Laboratory Medicine and Center for Cellular Immunotherapies, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-5156, USA
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5
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Abstract
IS911 has provided a powerful model for studying the transposition of members of a large class of transposable element: the IS3 family of bacterial Insertion Sequences (IS). These transpose by a Copy-out-Paste-in mechanism in which a double-strand IS circle transposition intermediate is generated from the donor site by replication and proceeds to integrate into a suitable double strand DNA target. This is perhaps one of the most common transposition mechanisms known to date. Copy-out-Paste-in transposition has been adopted by members of at least eight large IS families. This chapter details the different steps of the Copy-out-Paste-in mechanism involved in IS911 transposition. At a more biological level it also describes various aspects of regulation of the transposition process. These include transposase production by programmed translational frameshifting, transposase expression from the circular intermediate using a specialized promoter assembled at the circle junction and binding of the nascent transposase while it remains attached to the ribosome during translation (co-translational binding). This co-translational binding of the transposase to neighboring IS ends provides an explanation for the longstanding observation that transposases show a cis-preference for their activities.
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Abstract
ABSTRACT
The bacterial transposon Tn7 is distinguished by the levels of control it displays over transposition and its capacity to utilize different kinds of target sites. Transposition is carried out using five transposon-encoded proteins, TnsA, TnsB, TnsC, TnsD, and TnsE, which facilitate transfer of the element while minimizing the chances of inactivating host genes by using two pathways of transposition. One of these pathways utilizes TnsD, which targets transposition into a single site found in bacteria (
attTn7
), and a second utilizes TnsE, which preferentially directs transposition into plasmids capable of moving between bacteria. Control of transposition involves a heteromeric transposase that consists of two proteins, TnsA and TnsB, and a regulator protein TnsC. Tn7 also has the ability to inhibit transposition into a region already occupied by the element in a process called target immunity. Considerable information is available about the functional interactions of the Tn7 proteins and many of the protein–DNA complexes involved in transposition. Tn7-like elements that encode homologs of all five of the proteins found in Tn7 are common in diverse bacteria, but a newly appreciated larger family of elements appears to use the same core TnsA, TnsB, and TnsC proteins with other putative target site selector proteins allowing different targeting pathways.
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7
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The Tn7 transposition regulator TnsC interacts with the transposase subunit TnsB and target selector TnsD. Proc Natl Acad Sci U S A 2014; 111:E2858-65. [PMID: 24982178 DOI: 10.1073/pnas.1409869111] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The excision of transposon Tn7 from a donor site and its insertion into its preferred target site, attachment site attTn7, is mediated by four Tn7-encoded transposition proteins: TnsA, TnsB, TnsC, and TnsD. Transposition requires the assembly of a nucleoprotein complex containing all four Tns proteins and the DNA substrates, the donor site containing Tn7, and the preferred target site attTn7. TnsA and TnsB together form the heteromeric Tn7 transposase, and TnsD is a target-selecting protein that binds specifically to attTn7. TnsC is the key regulator of transposition, interacting with both the TnsAB transposase and TnsD-attTn7. We show here that TnsC interacts directly with TnsB, and identify the specific region of TnsC involved in the TnsB-TnsC interaction during transposition. We also show that a TnsC mutant defective in interaction with TnsB is defective for Tn7 transposition both in vitro and in vivo. Tn7 displays cis-acting target immunity, which blocks Tn7 insertion into a target DNA that already contains Tn7. We provide evidence that the direct TnsB-TnsC interaction that we have identified also mediates cis-acting Tn7 target immunity. We also show that TnsC interacts directly with the target selector protein TnsD.
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8
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Suicidal autointegration of sleeping beauty and piggyBac transposons in eukaryotic cells. PLoS Genet 2014; 10:e1004103. [PMID: 24625543 PMCID: PMC3952818 DOI: 10.1371/journal.pgen.1004103] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 11/23/2013] [Indexed: 01/04/2023] Open
Abstract
Transposons are discrete segments of DNA that have the distinctive ability to move and replicate within genomes across the tree of life. 'Cut and paste' DNA transposition involves excision from a donor locus and reintegration into a new locus in the genome. We studied molecular events following the excision steps of two eukaryotic DNA transposons, Sleeping Beauty (SB) and piggyBac (PB) that are widely used for genome manipulation in vertebrate species. SB originates from fish and PB from insects; thus, by introducing these transposons to human cells we aimed to monitor the process of establishing a transposon-host relationship in a naïve cellular environment. Similarly to retroviruses, neither SB nor PB is capable of self-avoidance because a significant portion of the excised transposons integrated back into its own genome in a suicidal process called autointegration. Barrier-to-autointegration factor (BANF1), a cellular co-factor of certain retroviruses, inhibited transposon autointegration, and was detected in higher-order protein complexes containing the SB transposase. Increasing size sensitized transposition for autointegration, consistent with elevated vulnerability of larger transposons. Both SB and PB were affected similarly by the size of the transposon in three different assays: excision, autointegration and productive transposition. Prior to reintegration, SB is completely separated from the donor molecule and followed an unbiased autointegration pattern, not associated with local hopping. Self-disruptive autointegration occurred at similar frequency for both transposons, while aberrant, pseudo-transposition events were more frequently observed for PB.
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Mancilla M, Marín CM, Blasco JM, Zárraga AM, López-Goñi I, Moriyón I. Spontaneous excision of the O-polysaccharide wbkA glycosyltranferase gene is a cause of dissociation of smooth to rough Brucella colonies. J Bacteriol 2012; 194:1860-7. [PMID: 22328663 PMCID: PMC3318470 DOI: 10.1128/jb.06561-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 01/27/2012] [Indexed: 01/07/2023] Open
Abstract
The brucellae are Gram-negative pathogens that cause brucellosis, a zoonosis of worldwide importance. The genus Brucella includes smooth and rough species that differ in that they carry smooth and rough lipopolysaccharides, respectively. Brucella abortus, B. melitensis, and B. suis are typical smooth species. However, these smooth brucellae dissociate into rough mutants devoid of the lipopolysaccharide O-polysaccharide, a major antigen and a virulence determinant encoded in regions wbo (included in genomic island-2) and wbk. We demonstrate here the occurrence of spontaneous recombination events in those three Brucella species leading to the deletion of a 5.5-kb fragment carrying the wbkA glycosyltranferase gene and to the appearance of rough mutants. Analysis of the recombination intermediates suggested homologous recombination between the ISBm1 insertion sequences flanking wbkA as the mechanism generating the deletion. Excision of wbkA was reduced but not abrogated in a recA-deficient mutant, showing the existence of both RecA-dependent and -independent processes. Although the involvement of the ISBm1 copies flanking wbkA suggested a transpositional event, the predicted transpositional joint could not be detected. This absence of detectable transposition was consistent with the presence of polymorphism in the inverted repeats of one of the ISBm1 copies. The spontaneous excision of wbkA represents a novel dissociation mechanism of smooth brucellae that adds to the previously described excision of genomic island-2. This ISBm1-mediated wbkA excision and the different %GC levels of the excised fragment and of other wbk genes suggest that the Brucella wbk locus is the result of at least two horizontal acquisition events.
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Affiliation(s)
- Marcos Mancilla
- Instituto de Salud Tropical y Departamento de Microbiología y Parasitología, Universidad de Navarra, Pamplona, Spain
| | - Clara M. Marín
- Centro de Investigación y Tecnología Agroalimentaria, Unidad de Sanidad Animal, Gobierno de Aragón, Zaragoza, Spain
| | - José M. Blasco
- Centro de Investigación y Tecnología Agroalimentaria, Unidad de Sanidad Animal, Gobierno de Aragón, Zaragoza, Spain
| | - Ana María Zárraga
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Ignacio López-Goñi
- Instituto de Salud Tropical y Departamento de Microbiología y Parasitología, Universidad de Navarra, Pamplona, Spain
| | - Ignacio Moriyón
- Instituto de Salud Tropical y Departamento de Microbiología y Parasitología, Universidad de Navarra, Pamplona, Spain
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10
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Lewis LA, Astatke M, Umekubo PT, Alvi S, Saby R, Afrose J, Oliveira PH, Monteiro GA, Prazeres DM. Protein-DNA interactions define the mechanistic aspects of circle formation and insertion reactions in IS2 transposition. Mob DNA 2012; 3:1. [PMID: 22277150 PMCID: PMC3299598 DOI: 10.1186/1759-8753-3-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Accepted: 01/26/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Transposition in IS3, IS30, IS21 and IS256 insertion sequence (IS) families utilizes an unconventional two-step pathway. A figure-of-eight intermediate in Step I, from asymmetric single-strand cleavage and joining reactions, is converted into a double-stranded minicircle whose junction (the abutted left and right ends) is the substrate for symmetrical transesterification attacks on target DNA in Step II, suggesting intrinsically different synaptic complexes (SC) for each step. Transposases of these ISs bind poorly to cognate DNA and comparative biophysical analyses of SC I and SC II have proven elusive. We have prepared a native, soluble, active, GFP-tagged fusion derivative of the IS2 transposase that creates fully formed complexes with single-end and minicircle junction (MCJ) substrates and used these successfully in hydroxyl radical footprinting experiments. RESULTS In IS2, Step I reactions are physically and chemically asymmetric; the left imperfect, inverted repeat (IRL), the exclusive recipient end, lacks donor function. In SC I, different protection patterns of the cleavage domains (CDs) of the right imperfect inverted repeat (IRR; extensive in cis) and IRL (selective in trans) at the single active cognate IRR catalytic center (CC) are related to their donor and recipient functions. In SC II, extensive binding of the IRL CD in trans and of the abutted IRR CD in cis at this CC represents the first phase of the complex. An MCJ substrate precleaved at the 3' end of IRR revealed a temporary transition state with the IRL CD disengaged from the protein. We propose that in SC II, sequential 3' cleavages at the bound abutted CDs trigger a conformational change, allowing the IRL CD to complex to its cognate CC, producing the second phase. Corroborating data from enhanced residues and curvature propensity plots suggest that CD to CD interactions in SC I and SC II require IRL to assume a bent structure, to facilitate binding in trans. CONCLUSIONS Different transpososomes are assembled in each step of the IS2 transposition pathway. Recipient versus donor end functions of the IRL CD in SC I and SC II and the conformational change in SC II that produces the phase needed for symmetrical IRL and IRR donor attacks on target DNA highlight the differences.
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Affiliation(s)
- Leslie A Lewis
- Department of Biology, York College of the City University of New York, Jamaica, New York 11451, USA.
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11
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He S, Hickman AB, Dyda F, Johnson NP, Chandler M, Ton-Hoang B. Reconstitution of a functional IS608 single-strand transpososome: role of non-canonical base pairing. Nucleic Acids Res 2011; 39:8503-12. [PMID: 21745812 PMCID: PMC3201880 DOI: 10.1093/nar/gkr566] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Single-stranded (ss) transposition, a recently identified mechanism adopted by members of the widespread IS200/IS605 family of insertion sequences (IS), is catalysed by the transposase, TnpA. The transposase of IS608, recognizes subterminal imperfect palindromes (IP) at both IS ends and cleaves at sites located at some distance. The cleavage sites, C, are not recognized directly by the protein but by short sequences 5′ to the foot of each IP, guide (G) sequences, using a network of canonical (‘Watson–Crick’) base interactions. In addition a set of non-canonical base interactions similar to those found in RNA structures are also involved. We have reconstituted a biologically relevant complex, the transpososome, including both left and right ends and TnpA, which catalyses excision of a ss DNA circle intermediate. We provide a detailed picture of the way in which the IS608 transpososome is assembled and demonstrate that both C and G sequences are essential for forming a robust transpososome detectable by EMSA. We also address several questions central to the organization and function of the ss transpososome and demonstrate the essential role of non-canonical base interactions in the IS608 ends for its stability by using point mutations which destroy individual non-canonical base interactions.
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Affiliation(s)
- Susu He
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de Recherche Scientifique, Unité Mixte de Recherche 5100, 118 Rte de Narbonne, F31062 Toulouse Cedex, France
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12
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Application of the bacteriophage Mu-driven system for the integration/amplification of target genes in the chromosomes of engineered Gram-negative bacteria--mini review. Appl Microbiol Biotechnol 2011; 91:857-71. [PMID: 21698377 PMCID: PMC3145075 DOI: 10.1007/s00253-011-3416-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 05/24/2011] [Accepted: 05/24/2011] [Indexed: 11/04/2022]
Abstract
The advantages of phage Mu transposition-based systems for the chromosomal editing of plasmid-less strains are reviewed. The cis and trans requirements for Mu phage-mediated transposition, which include the L/R ends of the Mu DNA, the transposition factors MuA and MuB, and the cis/trans functioning of the E element as an enhancer, are presented. Mini-Mu(LR)/(LER) units are Mu derivatives that lack most of the Mu genes but contain the L/R ends or a properly arranged E element in cis to the L/R ends. The dual-component system, which consists of an integrative plasmid with a mini-Mu and an easily eliminated helper plasmid encoding inducible transposition factors, is described in detail as a tool for the integration/amplification of recombinant DNAs. This chromosomal editing method is based on replicative transposition through the formation of a cointegrate that can be resolved in a recombination-dependent manner. (E-plus)- or (E-minus)-helpers that differ in the presence of the trans-acting E element are used to achieve the proper mini-Mu transposition intensity. The systems that have been developed for the construction of stably maintained mini-Mu multi-integrant strains of Escherichia coli and Methylophilus methylotrophus are described. A novel integration/amplification/fixation strategy is proposed for consecutive independent replicative transpositions of different mini-Mu(LER) units with “excisable” E elements in methylotrophic cells.
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13
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Montaño SP, Rice PA. Moving DNA around: DNA transposition and retroviral integration. Curr Opin Struct Biol 2011; 21:370-8. [PMID: 21439812 DOI: 10.1016/j.sbi.2011.03.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 03/08/2011] [Accepted: 03/08/2011] [Indexed: 11/16/2022]
Abstract
Mobile DNA elements are found in all kingdoms of life, and they employ numerous mechanisms to move within and between genomes. Here we review recent structural advances in understanding two very different families of DNA transposases and retroviral integrases: the DDE and Y1 groups. Even within the DDE family which shares a conserved catalytic domain, there is great diversity in the architecture of the synaptic complexes formed by the intact enzymes with their cognate element-end DNAs. However, recurring themes arise from comparing these complexes, such as stabilization by an intertwined network of protein-DNA and protein-protein contacts, and catalysis in trans, where each active subunit catalyzes the chemical steps on one DNA segment but also binds specific sequences on the other.
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Affiliation(s)
- Sherwin P Montaño
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th St., Chicago, IL 60637, United States
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Folded DNA in action: hairpin formation and biological functions in prokaryotes. Microbiol Mol Biol Rev 2011; 74:570-88. [PMID: 21119018 DOI: 10.1128/mmbr.00026-10] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Structured forms of DNA with intrastrand pairing are generated in several cellular processes and are involved in biological functions. These structures may arise on single-stranded DNA (ssDNA) produced during replication, bacterial conjugation, natural transformation, or viral infections. Furthermore, negatively supercoiled DNA can extrude inverted repeats as hairpins in structures called cruciforms. Whether they are on ssDNA or as cruciforms, hairpins can modify the access of proteins to DNA, and in some cases, they can be directly recognized by proteins. Folded DNAs have been found to play an important role in replication, transcription regulation, and recognition of the origins of transfer in conjugative elements. More recently, they were shown to be used as recombination sites. Many of these functions are found on mobile genetic elements likely to be single stranded, including viruses, plasmids, transposons, and integrons, thus giving some clues as to the manner in which they might have evolved. We review here, with special focus on prokaryotes, the functions in which DNA secondary structures play a role and the cellular processes giving rise to them. Finally, we attempt to shed light on the selective pressures leading to the acquisition of functions for DNA secondary structures.
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15
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Rousseau P, Tardin C, Tolou N, Salomé L, Chandler M. A model for the molecular organisation of the IS911 transpososome. Mob DNA 2010; 1:16. [PMID: 20553579 PMCID: PMC2909936 DOI: 10.1186/1759-8753-1-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Accepted: 06/16/2010] [Indexed: 11/10/2022] Open
Abstract
Tight regulation of transposition activity is essential to limit damage transposons may cause by generating potentially lethal DNA rearrangements. Assembly of a bona fide protein-DNA complex, the transpososome, within which transposition is catalysed, is a crucial checkpoint in this regulation. In the case of IS911, a member of the large IS3 bacterial insertion sequence family, the transpososome (synaptic complex A; SCA) is composed of the right and left inverted repeated DNA sequences (IRR and IRL) bridged by the transposase, OrfAB (the IS911-encoded enzyme that catalyses transposition). To characterise further this important protein-DNA complex in vitro, we used different tagged and/or truncated transposase forms and analysed their interaction with IS911 ends using gel electrophoresis. Our results allow us to propose a model in which SCA is assembled with a dimeric form of the transposase. Furthermore, we present atomic force microscopy results showing that the terminal inverted repeat sequences are probably assembled in a parallel configuration within the SCA. These results represent the first step in the structural description of the IS911 transpososome, and are discussed in comparison with the very few other transpososome examples described in the literature.
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Affiliation(s)
- Philippe Rousseau
- Centre National de la Recherche Scientifique, LMGM, F-31000 Toulouse, France.
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16
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Architecture of the Tn7 posttransposition complex: an elaborate nucleoprotein structure. J Mol Biol 2010; 401:167-81. [PMID: 20538004 DOI: 10.1016/j.jmb.2010.06.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 05/30/2010] [Accepted: 06/02/2010] [Indexed: 11/20/2022]
Abstract
Four transposition proteins encoded by the bacterial transposon Tn7, TnsA, TnsB, TnsC, and TnsD, mediate its site- and orientation-specific insertion into the chromosomal site attTn7. To establish which Tns proteins are actually present in the transpososome that executes DNA breakage and joining, we have determined the proteins present in the nucleoprotein product of transposition, the posttransposition complex (PTC), using fluorescently labeled Tns proteins. All four required Tns proteins are present in the PTC in which we also find that the Tn7 ends are paired by protein-protein contacts between Tns proteins bound to the ends. Quantification of the relative amounts of the fluorescent Tns proteins in the PTC indicates that oligomers of TnsA, TnsB, and TnsC mediate Tn7 transposition. High-resolution DNA footprinting of the DNA product of transposition attTn7Colon, two colonsTn7 revealed that about 350 bp of DNA on the transposon ends and on attTn7 contact the Tns proteins. All seven binding sites for TnsB, the component of the transposase that specifically binds the ends and mediates 3' end breakage and joining, are occupied in the PTC. However, the protection pattern of the sites closest to the Tn7 ends in the PTC are different from that observed with TnsB alone, likely reflecting the pairing of the ends and their interaction with the target nucleoprotein complex necessary for activation of the breakage and joining steps. We also observe extensive protection of the attTn7 sequences in the PTC and that alternative DNA structures in substrate attTn7 that are imposed by TnsD are maintained in the PTC.
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17
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Carpes MP, Nunes JF, Sampaio TL, Castro MEB, Zanotto PMA, Ribeiro BM. Molecular analysis of a mutant Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) shows an interruption of an inhibitor of apoptosis gene (iap-3) by a new class-II piggyBac-related insect transposon. INSECT MOLECULAR BIOLOGY 2009; 18:747-757. [PMID: 19788700 DOI: 10.1111/j.1365-2583.2009.00917.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A new piggyBac-related transposable element (TE) was found in the genome of a mutant Anticarsia gemmatalis multiple nucleopolyhedrovirus interrupting an inhibitor of apoptosis gene. This mutant virus induces apoptosis upon infection of an Anticarsia gemmatalis cell line, but not in a Trichoplusia ni cell line. The sequence of the new TE (which was named IDT for iap disruptor transposon) has 2531 bp with two DNA sequences flanking a putative Transposase (Tpase) ORF of 1719 bp coding for a protein with 572 amino acids. These structural features are similar to the piggyBac TE, also reported for the first time in the genome of a baculovirus. We have also isolated variants of this new TE from different lepidopteran insect cells and compared their Tpase sequences.
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Affiliation(s)
- M P Carpes
- Laboratório de Microscopia Eletrônica, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brazil
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18
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Claeys Bouuaert C, Chalmers RM. Gene therapy vectors: the prospects and potentials of the cut-and-paste transposons. Genetica 2009; 138:473-84. [PMID: 19649713 DOI: 10.1007/s10709-009-9391-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Accepted: 07/14/2009] [Indexed: 11/28/2022]
Abstract
Gene therapy applications require efficient tools for the stable delivery of genetic information into eukaryotic genomes. Most current gene delivery strategies are based on viral vectors. However, a number of drawbacks, such as the limited cargo capacity, host immune response and mutational risks, highlight the need for alternative gene delivery tools. A comprehensive gene therapy tool kit should contain a range of vectors and techniques that can be adapted to different targets and purposes. Transposons provide a potentially powerful approach. However, transposons encompass a large number of different molecular mechanisms, some of which are better suited to gene delivery applications than others. Here, we consider the range and potentials of the various mechanisms, focusing on the cut-and-paste transposons as one of the more promising avenues towards gene therapy applications. Several cut-and-paste transposition systems are currently under development. We will first consider the mechanisms of piggyBac and the hAT family elements Tol1 and Tol2, before focusing on the mariner family elements including Mos1, Himar1 and Hsmar1.
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Affiliation(s)
- Corentin Claeys Bouuaert
- School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
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19
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Treangen TJ, Abraham AL, Touchon M, Rocha EPC. Genesis, effects and fates of repeats in prokaryotic genomes. FEMS Microbiol Rev 2009; 33:539-71. [PMID: 19396957 DOI: 10.1111/j.1574-6976.2009.00169.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
DNA repeats are causes and consequences of genome plasticity. Repeats are created by intrachromosomal recombination or horizontal transfer. They are targeted by recombination processes leading to amplifications, deletions and rearrangements of genetic material. The identification and analysis of repeats in nearly 700 genomes of bacteria and archaea is facilitated by the existence of sequence data and adequate bioinformatic tools. These have revealed the immense diversity of repeats in genomes, from those created by selfish elements to the ones used for protection against selfish elements, from those arising from transient gene amplifications to the ones leading to stable duplications. Experimental works have shown that some repeats do not carry any adaptive value, while others allow functional diversification and increased expression. All repeats carry some potential to disorganize and destabilize genomes. Because recombination and selection for repeats vary between genomes, the number and types of repeats are also quite diverse and in line with ecological variables, such as host-dependent associations or population sizes, and with genetic variables, such as the recombination machinery. From an evolutionary point of view, repeats represent both opportunities and problems. We describe how repeats are created and how they can be found in genomes. We then focus on the functional and genomic consequences of repeats that dictate their fate.
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20
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Abalakina EG, Tokmakova IL, Gorshkova NV, Gak ER, Akhverdyan VZ, Mashko SV, Yomantas YAV. Phage Mu-driven two-plasmid system for integration of recombinant DNA in the Methylophilus methylotrophus genome. Appl Microbiol Biotechnol 2008; 81:191-200. [PMID: 18820908 PMCID: PMC7419445 DOI: 10.1007/s00253-008-1696-7] [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] [Received: 07/10/2008] [Revised: 08/27/2008] [Accepted: 09/01/2008] [Indexed: 11/18/2022]
Abstract
A phage Mu-driven two-plasmid system for DNA integration in Escherichia coli genome has been adjusted for Methylophilus methylotrophus. Constructed helper plasmids with broad-host-range replicons carry thermo-inducible genes for transposition factors MuA and MuB. Integrative plasmids that are only replicated in E. coli could be mobilized to M. methylotrophus and contained mini-Mu unit with a short terminus of Mu DNA, Mu-attL/R. Mini-Mu unit was integrated in the M. methylotrophus genome via mobilization of the integrative plasmid to the cells carrying the helper in conditions of thermo-induced expression of MuA and MuB. In this system, mini-Mu unit was mainly integrated due to replicative transposition, and the integrated copy could be amplified in the M. methylotrophus chromosome in the presence of helper plasmid. A kan-gene flanked by FRT sites was inserted in one of the mini-Mu units, and it could be readily excised by yeast FLP recombinase that is encoded by the designed plasmid. The multiple Mu-driven gene insertion was carried out by integration of the Bacillus amyloliquefaciens α-amylase gene followed by curing the KmR marker before integration of the second mini-Mu unit with Pseudomonas putida xylE gene encoding catechol 2,3-dioxygenase (C23O).
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Affiliation(s)
- Elena G Abalakina
- Ajinomoto-Genetika Research Institute, 117545, Moscow, Russian Federation
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21
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Zerillo MM, Van Sluys MA, Camargo LEA, Monteiro-Vitorello CB. Characterization of new IS elements and studies of their dispersion in two subspecies of Leifsonia xyli. BMC Microbiol 2008; 8:127. [PMID: 18655699 PMCID: PMC2516522 DOI: 10.1186/1471-2180-8-127] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Accepted: 07/25/2008] [Indexed: 12/05/2022] Open
Abstract
Background Leifsonia xyli is a xylem-inhabiting bacterial species comprised of two subspecies: L. xyli subsp. xyli (Lxx) and L. xyli subsp. cynodontis (Lxc). Lxx is the causal agent of ratoon stunting disease in sugarcane commercial fields and Lxc colonizes the xylem of several grasses causing either mild or no symptoms of disease. The completely sequenced genome of Lxx provided insights into its biology and pathogenicity. Since IS elements are largely reported as an important source of bacterial genome diversification and nothing is known about their role in chromosome architecture of L. xyli, a comparative analysis of Lxc and Lxx elements was performed. Results Sample sequencing of Lxc genome and comparative analysis with Lxx complete DNA sequence revealed a variable number of IS transposable elements acting upon genomic diversity. A detailed characterization of Lxc IS elements and a comparative review with IS elements of Lxx are presented. Each genome showed a unique set of elements although related to same IS families when considering features such as similarity among transposases, inverted and direct repeats, and element size. Most of the Lxc and Lxx IS families assigned were reported to maintain transposition at low levels using translation regulatory mechanisms, consistent with our in silico analysis. Some of the IS elements were found associated with rearrangements and specific regions of each genome. Differences were also found in the effect of IS elements upon insertion, although none of the elements were preferentially associated with gene disruption. A survey of transposases among genomes of Actinobacteria showed no correlation between phylogenetic relatedness and distribution of IS families. By using Southern hybridization, we suggested that diversification of Lxc isolates is also mediated by insertion sequences in probably recent events. Conclusion Collectively our data indicate that transposable elements are involved in genome diversification of Lxc and Lxx. The IS elements were probably acquired after the divergence of the two subspecies and are associated with genome organization and gene contents. In addition to enhancing understanding of IS element dynamics in general, these data will contribute to our ongoing comparative analyses aimed at understanding the biological differences of the Lxc and Lxx.
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Affiliation(s)
- Marcelo M Zerillo
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, 05508-900, São Paulo, SP, Brazil.
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22
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Elhai J, Kato M, Cousins S, Lindblad P, Costa JL. Very small mobile repeated elements in cyanobacterial genomes. Genome Res 2008; 18:1484-99. [PMID: 18599681 DOI: 10.1101/gr.074336.107] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Mobile DNA elements play a major role in genome plasticity and other evolutionary processes, an insight gained primarily through the study of transposons and retrotransposons (generally approximately 1000 nt or longer). These elements spawn smaller parasitic versions (generally >100 nt) that propagate through proteins encoded by the full elements. Highly repeated sequences smaller than 100 nt have been described, but they are either nonmobile or their origins are not known. We have surveyed the genome of the multicellular cyanobacterium, Nostoc punctiforme, and its relatives for small dispersed repeat (SDR) sequences and have identified eight families in the range of from 21 to 27 nucleotides. Three of the families (SDR4, SDR5, and SDR6), despite little sequence similarity, share a common predicted secondary structure, a conclusion supported by patterns of compensatory mutations. The SDR elements are found in a diverse set of contexts, often embedded within tandemly repeated heptameric sequences or within minitransposons. One element (SDR5) is found exclusively within instances of an octamer, HIP1, that is highly over-represented in the genomes of many cyanobacteria. Two elements (SDR1 and SDR4) often are found within copies of themselves, producing complex nested insertions. An analysis of SDR elements within cyanobacterial genomes indicate that they are essentially confined to a coherent subgroup. The evidence indicates that some of the SDR elements, probably working through RNA intermediates, have been mobile in recent evolutionary time, making them perhaps the smallest known mobile elements.
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Affiliation(s)
- Jeff Elhai
- Center for the Study of Biological Complexity and the Department of Biology, Virginia Commonwealth University, Richmond, Virginia 23284, USA.
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23
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Bias between the left and right inverted repeats during IS911 targeted insertion. J Bacteriol 2008; 190:6111-8. [PMID: 18586933 DOI: 10.1128/jb.00452-08] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
IS911 is a bacterial insertion sequence composed of two consecutive overlapping open reading frames (ORFs [orfA and orfB]) encoding the transposase (OrfAB) as well as a regulatory protein (OrfA). These ORFs are bordered by terminal left and right inverted repeats (IRL and IRR, respectively) with several differences in nucleotide sequence. IS911 transposition is asymmetric: each end is cleaved on one strand to generate a free 3'-OH, which is then used as the nucleophile in attacking the opposite insertion sequence (IS) end to generate a free IS circle. This will be inserted into a new target site. We show here that the ends exhibit functional differences which, in vivo, may favor the use of one compared to the other during transposition. Electromobility shift assays showed that a truncated form of the transposase [OrfAB(1-149)] exhibits higher affinity for IRR than for IRL. While there was no detectable difference in IR activities during the early steps of transposition, IRR was more efficient during the final insertion steps. We show here that the differential activities between the two IRs correlate with the different affinities of OrfAB(1-149) for the IRs during assembly of the nucleoprotein complexes leading to transposition. We conclude that the two inverted repeats are not equivalent during IS911 transposition and that this asymmetry may intervene to determine the ordered assembly of the different protein-DNA complexes involved in the reaction.
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24
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Buck D, Flapan E. Predicting knot or catenane type of site-specific recombination products. J Mol Biol 2007; 374:1186-99. [PMID: 17996894 DOI: 10.1016/j.jmb.2007.10.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 10/03/2007] [Accepted: 10/05/2007] [Indexed: 11/27/2022]
Abstract
Site-specific recombination on supercoiled circular DNA yields a variety of knotted or catenated products. Here, we present a topological model of this process and characterize all possible products of the most common substrates: unknots, unlinks, and torus knots and catenanes. This model tightly prescribes the knot or catenane type of previously uncharacterized data. We also discuss how the model helps to distinguish products of distributive recombination and, in some cases, determine the order of processive recombination products.
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Affiliation(s)
- Dorothy Buck
- Department of Mathematics and Center for Bioinformatics, Imperial College London, London, England SW7 2AZ, UK.
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25
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The dynamic Mu transpososome: MuB activation prevents disintegration. J Mol Biol 2007; 374:1158-71. [PMID: 17988683 DOI: 10.1016/j.jmb.2007.09.079] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Revised: 09/25/2007] [Accepted: 09/26/2007] [Indexed: 11/20/2022]
Abstract
DNA transposases use a single active center to sequentially cleave the transposable element DNA and join this DNA to a target site. Recombination requires controlled conformational changes within the transposase to ensure that these chemically distinct steps occur at the right time and place, and that the reaction proceeds in the net forward direction. Mu transposition is catalyzed by a stable complex of MuA transposase bound to paired Mu DNA ends (a transpososome). We find that Mu transpososomes efficiently catalyze disintegration when recombination on one end of the Mu DNA is blocked. The MuB activator protein controls the integration versus disintegration equilibrium. When MuB is present, disintegration occurs slowly and transpososomes that have disintegrated catalyze subsequent rounds of recombination. In the absence of MuB, disintegration goes to completion. These results together with experiments mapping the MuA-MuB contacts during DNA joining suggest that MuB controls progression of recombination by specifically stabilizing a concerted transition to the "joining" configuration of MuA. Thus, we propose that MuB's interaction with the transpososome actively promotes coupled joining of both ends of the element DNA into the same target site and may provide a mechanism to antagonize formation of single-end transposition products.
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26
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Tang M, Cecconi C, Bustamante C, Rio DC. Analysis of P element transposase protein-DNA interactions during the early stages of transposition. J Biol Chem 2007; 282:29002-29012. [PMID: 17644523 DOI: 10.1074/jbc.m704106200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P elements are a family of transposable elements found in Drosophila that move by using a cut-and-paste mechanism and that encode a transposase protein that uses GTP as a cofactor for transposition. Here we used atomic force microscopy to visualize the initial interaction of transposase protein with P element DNA. The transposase first binds to one of the two P element ends, in the presence or absence of GTP, prior to synapsis. In the absence of GTP, these complexes remain stable but do not proceed to synapsis. In the presence of GTP or nonhydrolyzable GTP analogs, synapsis happens rapidly, whereas DNA cleavage is slow. Both atomic force microscopy and standard biochemical methods have been used to show that the P element transposase exists as a pre-formed tetramer that initially binds to either one of the two P element ends in the absence of GTP prior to synapsis. This initial single end binding may explain some of the aberrant P element-induced rearrangements observed in vivo, such as hybrid end insertion. The allosteric effect of GTP in promoting synapsis by P element transposase may be to orient a second site-specific DNA binding domain in the tetramer allowing recognition of a second high affinity transposase-binding site at the other transposon end.
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Affiliation(s)
- Mei Tang
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development and Division of Biochemistry and Molecular Biology, Center for Integrative Genomics, University of California, Berkeley, California 94720
| | - Ciro Cecconi
- CNR-INFM-S3 University of Modena e Reggio Emilia, 41100 Modena, Italy
| | - Carlos Bustamante
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development and Division of Biochemistry and Molecular Biology, Center for Integrative Genomics, University of California, Berkeley, California 94720; Department of Physics, University of California, Berkeley, California 94720; Howard Hughes Medical Institute, Berkeley, California 94720; Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Donald C Rio
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development and Division of Biochemistry and Molecular Biology, Center for Integrative Genomics, University of California, Berkeley, California 94720.
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27
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Gueguen E, Rousseau P, Duval-Valentin G, Chandler M. Truncated forms of IS911 transposase downregulate transposition. Mol Microbiol 2007; 62:1102-16. [PMID: 17078817 DOI: 10.1111/j.1365-2958.2006.05424.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
IS911 naturally produces transposase (OrfAB) derivatives truncated at the C-terminal end (OrfAB-CTF) and devoid of the catalytic domain. A majority species, OrfAB*, was produced at higher levels at 42 degrees C than at 30 degrees C suggesting that it is at least partly responsible for the innate reduction in IS911 transposition activity at higher temperatures. An engineered equivalent of similar length, OrfAB[1-149], inhibited transposition activity in vivo or in vitro when produced along with full-length transposase. We isolated several point mutants showing higher activity than the wild-type IS911 at 42 degrees C. These fall into two regions of the transposase. One, located in the N-terminal segment of OrfAB, lies between or within two regions involved in protein multimerization. The other is located within the C-terminal catalytic domain. The N-terminal mutations resulted in reduced levels of OrfAB* while the C-terminal mutation alone appeared not to affect OrfAB* levels. Combination of N- and C-terminal mutations greatly reduced OrfAB* levels and transposition was concomitantly high even at 42 degrees C. The mechanism by which truncated transposase species are generated and how they intervene to reduce transposition activity is discussed. While transposition activity of these multiply mutated derivatives in vivo was resistant to temperature, the purified OrfAB derivatives retained an inherent temperature-sensitive phenotype in vitro. This clearly demonstrates that temperature sensitivity of IS911 transposition is a complex phenomenon with several mechanistic components. These results have important implications for the several other transposons and insertion sequences whose transposition has also been shown to be temperature-sensitive.
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Affiliation(s)
- Erwan Gueguen
- Laboratoire de Microbiologie et de Génétique Moléculaire, UMR 5100 CNRS (Campus Paul Sabatier), 118 route de Narbonne, 31062 Toulouse Cedex 09, France
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28
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Abstract
Phage Mu is the most efficient transposable element known, its high efficiency being conferred by an enhancer DNA element. Transposition is the end result of a series of well choreographed steps that juxtapose the enhancer and the two Mu ends within a nucleoprotein complex called the 'transpososome.' The particular arrangement of DNA and protein components lends extraordinary stability to the transpososome and regulates the frequency, precision, directionality, and mechanism of transposition. The structure of the transpososome, therefore, holds the key to understanding all of these attributes, and ultimately to explaining the runaway genetic success of transposable elements throughout the biological world. This review focuses on the path of the DNA within the Mu transpososome, as uncovered by recent topological analyses. It discusses why Mu topology cannot be analyzed by standard methods, and how knowledge of the geometry of site alignment during Flp and Cre site-specific recombination was harnessed to design a new methodology called 'difference topology.' This methodology has also revealed the order and dynamics of association of the three interacting DNA sites, as well as the role of the enhancer in assembly of the Mu transpososome.
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Affiliation(s)
- Rasika M Harshey
- Section of Molecular Genetics and Microbiology & Institute of Cellular and Molecular Biology, University of Texas at Austin, TX, USA.
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29
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Loot C, Santiago N, Sanz A, Casacuberta JM. The proteins encoded by the pogo-like Lemi1 element bind the TIRs and subterminal repeated motifs of the Arabidopsis Emigrant MITE: consequences for the transposition mechanism of MITEs. Nucleic Acids Res 2006; 34:5238-46. [PMID: 17003053 PMCID: PMC1636448 DOI: 10.1093/nar/gkl688] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
MITEs (miniature inverted-repeated transposable elements) are a particular class of defective DNA transposons usually present within genomes as high copy number populations of highly homogeneous elements. Although an active MITE, the mPing element, has recently been characterized in rice, the transposition mechanism of MITEs remains unknown. It has been proposed that transposases of related transposons could mobilize MITEs in trans. Moreover, it has also been proposed that the presence of conserved terminal inverted-repeated (TIR) sequences could be the only requirement of MITEs for mobilization, allowing divergent or unrelated elements to be mobilized by a particular transposase. We present here evidence for a recent mobility of the Arabidopsis Emigrant MITE and we report on the capacity of the proteins encoded by the related Lemi1 transposon, a pogo-related element, to specifically bind Emigrant elements. This suggests that Lemi1 could mobilize Emigrant elements and makes the Lemi1/Emigrant couple an ideal system to study the transposition mechanism of MITEs. Our results show that Lemi1 proteins bind Emigrant TIRs but also bind cooperatively to subterminal repeated motifs. The requirement of internal sequences for the formation of proper DNA/protein structure could affect the capacity of divergent MITEs to be mobilized by distantly related transposases.
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Affiliation(s)
| | | | | | - Josep M. Casacuberta
- To whom correspondence should be addressed. Tel: +34 93 4006142; Fax: +34 93 2045904;
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30
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Brillet B, Benjamin B, Bigot Y, Yves B, Augé-Gouillou C, Corinne AG. Assembly of the Tc1 and mariner transposition initiation complexes depends on the origins of their transposase DNA binding domains. Genetica 2006; 130:105-20. [PMID: 16912840 DOI: 10.1007/s10709-006-0025-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Accepted: 06/02/2006] [Indexed: 01/20/2023]
Abstract
In this review, we focus on the assembly of DNA/protein complexes that trigger transposition in eukaryotic members of the IS630-Tc1-mariner (ITm) super-family, the Tc1- and mariner-like elements (TLEs and MLEs). Elements belonging to this super-family encode transposases with DNA binding domains of different origins, and recent data indicate that the chimerization of functional domains has been an important evolutionary aspect in the generation of new transposons within the ITm super-family. These data also reveal that the inverted terminal repeats (ITRs) at the ends of transposons contain three kinds of motif within their sequences. The first two are well known and correspond to the cleavage site on the outer ITR extremities, and the transposase DNA binding site. The organization of ITRs and of the transposase DNA binding domains implies that differing pathways are used by MLEs and TLEs to regulate transposition initiation. These differences imply that the ways ITRs are recognized also differ leading to the formation of differently organized synaptic complexes. The third kind of motif is the transposition enhancers, which have been found in almost all the functional MLEs and TLEs analyzed to date. Finally, in vitro and in vivo assays of various elements all suggest that the transposition initiation complex is not formed randomly, but involves a mechanism of oriented transposon scanning.
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Affiliation(s)
- Benjamin Brillet
- Laboratoire d'Etudes des Parasites Génétiques, Université François Rabelais, FRE CNRS 2969, UFR Sciences & Techniques, Parc Grandmont, 37200, Tours, France
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31
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Prosseda G, Latella MC, Casalino M, Nicoletti M, Michienzi S, Colonna B. Plasticity of the P junc promoter of ISEc11, a new insertion sequence of the IS1111 family. J Bacteriol 2006; 188:4681-9. [PMID: 16788177 PMCID: PMC1483014 DOI: 10.1128/jb.00332-06] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We describe identification and functional characterization of ISEc11, a new insertion sequence that is widespread in enteroinvasive E. coli (EIEC), in which it is always present on the virulence plasmid (pINV) and very frequently also present on the chromosome. ISEc11 is flanked by subterminal 13-bp inverted repeats (IRs) and is bounded by 3-bp terminal sequences, and it transposes with target specificity without generating duplication of the target site. ISEc11 is characterized by an atypical transposase containing the DEDD motif of the Piv/MooV family of DNA recombinases, and it is closely related to the IS1111 family. Transposition occurs by formation of minicircles through joining of the abutted ends and results in assembly of a junction promoter (P juncC) containing a -10 box in the interstitial sequence and a -35 box upstream of the right IR. A natural variant of ISEc11 (ISEc11p), found on EIEC pINV plasmids, contains a perfect duplication of the outermost 39 bp of the right end. Upon circularization, ISEc11p forms a junction promoter (P juncP) which, despite carrying -10 and -35 boxes identical to those of P juncC, exhibits 30-fold-greater strength in vivo. The discovery of only one starting point in primer extension experiments rules out the possibility that there are alternative promoter sites within the 39-bp duplication. Analysis of in vitro-generated transcripts confirmed that at limiting RNA polymerase concentrations, the activity of P juncP is 20-fold higher than the activity of P juncC. These observations suggest that the 39-bp duplication might host cis-acting elements that facilitate the binding of RNA polymerase to the promoter.
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Affiliation(s)
- Gianni Prosseda
- Dipartimento di Biologia Cellulare e dello Sviluppo, Università La Sapienza, Via dei Sardi 70, 00185 Roma, Italy
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Saariaho AH, Savilahti H. Characteristics of MuA transposase-catalyzed processing of model transposon end DNA hairpin substrates. Nucleic Acids Res 2006; 34:3139-49. [PMID: 16757579 PMCID: PMC1475752 DOI: 10.1093/nar/gkl405] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Bacteriophage Mu uses non-replicative transposition for integration into the host's chromosome and replicative transposition for phage propagation. Biochemical and structural comparisons together with evolutionary considerations suggest that the Mu transposition machinery might share functional similarities with machineries of the systems that are known to employ a hairpin intermediate during the catalytic steps of transposition. Model transposon end DNA hairpin substrates were used in a minimal-component in vitro system to study their proficiency to promote Mu transpososome assembly and subsequent MuA-catalyzed chemical reactions leading to the strand transfer product. MuA indeed was able to assemble hairpin substrates into a catalytically competent transpososome, open the hairpin ends and accurately join the opened ends to the target DNA. The hairpin opening and transposon end cleavage reactions had identical metal ion preferences, indicating similar conformations within the catalytic center for these reactions. Hairpin length influenced transpososome assembly as well as catalysis: longer loops were more efficient in these respects. In general, MuA's proficiency to utilize different types of hairpin substrates indicates a certain degree of flexibility within the transposition machinery core. Overall, the results suggest that non-replicative and replicative transposition systems may structurally and evolutionarily be more closely linked than anticipated previously.
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Affiliation(s)
| | - Harri Savilahti
- To whom correspondence should be addressed. Tel: +358 9 19159516; Fax: +358 9 19159366;
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