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Articles de revues sur le sujet "Transposase(SB)"
1
Ikeda, Ryuji, Chikara Kokubu, Kosuke Yusa, Vincent W. Keng, Kyoji Horie et Junji Takeda. « Sleeping Beauty Transposase Has an Affinity for Heterochromatin Conformation ». Molecular and Cellular Biology 27, no 5 (18 décembre 2006) : 1665–76. http://dx.doi.org/10.1128/mcb.01500-06.
Texte intégralRésumé :
ABSTRACT The Sleeping Beauty (SB) transposase reconstructed from salmonid fish has high transposition activity in mammals and has been a useful tool for insertional mutagenesis and gene delivery. However, the transposition efficiency has varied significantly among studies. Our previous study demonstrated that the introduction of methylation into the SB transposon enhanced transposition, suggesting that transposition efficiency is influenced by the epigenetic status of the transposon region. Here, we examined the influence of the chromatin status on SB transposition in mouse embryonic stem cells. Heterochromatin conformation was introduced into the SB transposon by using a tetracycline-controlled transrepressor (tTR) protein, consisting of a tetracycline repressor (TetR) fused to the Kruppel-associated box (KRAB) domain of human KOX1 through tetracycline operator (tetO) sequences. The excision frequency of the SB transposon, which is the first step of the transposition event, was enhanced by approximately 100-fold. SB transposase was found to be colocalized with intense DAPI (4′,6′-diamidino-2-phenylindole) staining and with the HP1 family by biochemical fractionation analyses. Furthermore, chromatin immunoprecipitation analysis revealed that SB transposase was recruited to tTR-induced heterochromatic regions. These data suggest that the high affinity of SB transposase for heterochromatin conformation leads to enhancement of SB transposition efficiency.
2
Fili, A. E., A. P. Alessio, W. Garrels, D. O. Forcato, M. F. Olmos Nicotra, A. C. Liaudat, R. J. Bevacqua et al. « 242 HIGHLY EFFICIENT SLEEPING BEAUTY TRANSPOSON-MEDIATED TRANSGENESIS IN BOVINE FETAL FIBROBLASTS ». Reproduction, Fertility and Development 28, no 2 (2016) : 253. http://dx.doi.org/10.1071/rdv28n2ab242.
Texte intégralRésumé :
Active transposon-mediated transgenesis is an emerging tool for basic and applied research in livestock. We have demonstrated the effectiveness of a helper-independent piggyBac transposon (pGENIE-3) for gene transfer into the genome of bovine cells (Alessio et al. 2014 Reprod. Domest. Anim. 49, 8). Here, we extend our previous research by examining the suitability of a Sleeping Beauty (SB) transposon-based methodology to deliver transgenes into the genome of bovine fetal fibroblasts (BFF), and the ability of these cells to support in vitro embryo development upon somatic cell nuclear transfer (SCNT). In a first experiment, BFF were chemically cotransfected (JetPRIME®, Polyplus-transfection, Illkirch, France) with a helper plasmid (pCMV-SB100X), which carries an expression cassette for the SB transposase, and the donor vector (pT2/Venus/RMCE) harboring an expression cassette for a fluorescent protein (Venus) flanked by the SB inverted terminal repeats (ITR). Three different ratios of helper and donor plasmids were studied: 1 : 2, 1 : 1 and 2 : 1. After 15 days of culture, the number of fluorescent colonies was counted on an inverted microscope. When vectors were used at ratios of 1 : 1 and 2 : 1, a 78-fold and 88-fold increase (P ≤ 0.05) in the number of fluorescent colonies compared with that in the no-transposase control were calculated. In a second experiment, BFF were chemically cotransfected with the helper vector pCMV-SB100X, and 2 donor transposons: pT2/Venus/RMCE and pT2/SV40-Neo. The former harbors a neo resistance cassette framed by SB ITRs. Different ratios of helper:donors (1 : 1 : 1, 2 : 1 : 1 and 2 : 0.5 : 0.5) were studied, and each ratio compared with a no-transposase control. After 15 days of antibiotic selection, the number of G418-resistant colonies was determined. Every time a functional SB transposase vector was included, the number of fluorescent and G418-resistant colonies was markedly higher compared with that in the respective control without transposase (P ≤ 0.001). Interestingly, all G418-resistant colonies expressed Venus. Molecular characterisation of genomic insertions in 6 monoclonal cell lines was performed by PCR and splinkerette PCR. PCR analysis confirmed presence of the Venus transgene in all cell lines. Splinkerette PCR results revealed at least 15 transposase-catalyzed genomic insertions of the transgene. Individual cells from a polyclonal SB transgenic fibroblast culture were used as nuclear donors to produce zona-free SCNT embryos. Of the reconstructed embryos, 33% reached blastocyst stage and about half of them expressed Venus. In conclusion, SB transposase is able to actively transpose monomeric copies of transgenes into the genome of bovine cells, which can be reprogrammed upon nuclear transfer to generate morphologically normal embryos expressing the transgene of interest.
3
Yant, Stephen R., Julie Park, Yong Huang, Jacob Giehm Mikkelsen et Mark A. Kay. « Mutational Analysis of the N-Terminal DNA-Binding Domain of Sleeping Beauty Transposase : Critical Residues for DNA Binding and Hyperactivity in Mammalian Cells ». Molecular and Cellular Biology 24, no 20 (15 octobre 2004) : 9239–47. http://dx.doi.org/10.1128/mcb.24.20.9239-9247.2004.
Texte intégralRésumé :
ABSTRACT The N-terminal domain of the Sleeping Beauty (SB) transposase mediates transposon DNA binding, subunit multimerization, and nuclear translocation in vertebrate cells. For this report, we studied the relative contributions of 95 different residues within this multifunctional domain by large-scale mutational analysis. We found that each of four amino acids (leucine 25, arginine 36, isoleucine 42, and glycine 59) contributes to DNA binding in the context of the N-terminal 123 amino acids of SB transposase, as indicated by electrophoretic mobility shift analysis, and to functional activity of the full-length transposase, as determined by a quantitative HeLa cell-based transposition assay. Moreover, we show that amino acid substitutions within either the putative oligomerization domain (L11A, L18A, L25A, and L32A) or the nuclear localization signal (K104A and R105A) severely impair its ability to mediate DNA transposition in mammalian cells. In contrast, each of 10 single amino acid changes within the bipartite DNA-binding domain is shown to greatly enhance SB's transpositional activity in mammalian cells. These hyperactive mutations functioned synergistically when combined and are shown to significantly improve transposase affinity for transposon end sequences. Finally, we show that enhanced DNA-binding activity results in improved cleavage kinetics, increased SB element mobilization from host cell chromosomes, and dramatically improved gene transfer capabilities of SB in vivo in mice. These studies provide important insights into vertebrate transposon biology and indicate that Sleeping Beauty can be readily improved for enhanced genetic research applications in mammals.
4
Converse, Andrea D., Lalitha R. Belur, Jennifer L. Gori, Geyi Liu, Felipe Amaya, Estuardo Aguilar-Cordova, Perry B. Hackett et R. Scott McIvor. « Counterselection and Co-Delivery of Transposon and Transposase Functions for Sleeping Beauty-Mediated Transposition in Cultured Mammalian Cells ». Bioscience Reports 24, no 6 (1 décembre 2004) : 577–94. http://dx.doi.org/10.1007/s10540-005-2793-9.
Texte intégralRésumé :
Sleeping Beauty (SB) is a gene-insertion system reconstructed from transposon sequences found in teleost fish and is capable of mediating the transposition of DNA sequences from transfected plasmids into the chromosomes of vertebrate cell populations. The SB system consists of a transposon, made up of a gene of interest flanked by transposon inverted repeats, and a source of transposase. Here we carried out a series of studies to further characterize SB-mediated transposition as a tool for gene transfer to chromosomes and ultimately for human gene therapy. Transfection of mouse 3T3 cells, HeLa cells, and human A549 lung carcinoma cells with a transposon containing the neomycin phosphotransferase (NEO) gene resulted in a several-fold increase in drug-resistant colony formation when co-transfected with a plasmid expressing the SB transposase. A transposon containing a methotrexate-resistant dihydrofolate reductase gene was also found to confer an increased frequency of methotrexate-resistant colony formation when co-transfected with SB transposase-encoding plasmid. A plasmid containing a herpes simplex virus thymidine kinase gene as well as a transposon containing a NEO gene was used for counterselection against random recombinants (NEO+TK+) in medium containing G418 plus ganciclovir. Effective counterselection required a recovery period of 5 days after transfection before shifting into medium containing ganciclovir to allow time for transiently expressed thymidine kinase activity to subside in cells not stably transfected. Southern analysis of clonal isolates indicated a shift from random recombination events toward transposition events when clones were isolated in medium containing ganciclovir as well as G418. We found that including both transposon and transposase functions on the same plasmid substantially increased the stable gene transfer frequency in Huh7 human hepatoma cells. The results from these experiments contribute technical and conceptual insight into the process of transposition in mammalian cells, and into the optimal provision of transposon and transposase functions that may be applicable to gene therapy studies.
5
Huang, Xin, Andrew C. Wilber, Lei Bao, Dong Tuong, Jakub Tolar, Paul J. Orchard, Bruce L. Levine et al. « Stable gene transfer and expression in human primary T cells by the Sleeping Beauty transposon system ». Blood 107, no 2 (15 janvier 2006) : 483–91. http://dx.doi.org/10.1182/blood-2005-05-2133.
Texte intégralRésumé :
AbstractThe Sleeping Beauty (SB) transposon system is a nonviral DNA delivery system in which a transposase directs integration of an SB transposon into TA-dinucleotide sites in the genome. To determine whether the SB transposon system can mediate stable gene expression in human T cells, primary peripheral blood lymphocytes (PBLs) were nucleofected with SB vectors carrying a DsRed reporter gene. Plasmids containing the SB transposase on the same molecule as (cis) or on a molecule separate from (trans) the SB transposon mediated long-term and stable reporter gene expression in human primary T cells. Sequencing of transposon:chromosome junctions confirmed that stable gene expression was due to SB-mediated transposition. In other studies, PBLs were successfully transfected using the SB transposon system and shown to stably express a fusion protein consisting of (1) a surface receptor useful for positive T-cell selection and (2) a “suicide” gene useful for elimination of transfected T cells after chemotherapy. This study is the first report demonstrating that the SB transposon system can mediate stable gene transfer in human primary PBLs, which may be advantageous for T-cell–based gene therapies.
6
Zhou, Xianzheng, Xin Huang, Andrew C. Wilber, Lei Bao, Dong Tuong, Jakub Tolar, Paul J. Orchard et al. « Stable Gene Transfer and Expression in Human Primary T-Cells by the Sleeping Beauty Transposon System. » Blood 106, no 11 (16 novembre 2005) : 5539. http://dx.doi.org/10.1182/blood.v106.11.5539.5539.
Texte intégralRésumé :
Abstract The Sleeping Beauty (SB) transposon system is a non-viral DNA delivery system in which a transposase directs integration of an SB transposon into TA-dinucleotide sites in the genome. To determine whether the SB transposon system can mediate integration and long-term transgene expression in human primary T-cells, freshly isolated peripheral blood lymphocytes (PBLs) without prior activation were nucleofected with SB vectors carrying a DsRed reporter gene. Plasmids containing the SB transposase on the same (cis) (n=10) or separate molecule (trans) (n=8) as the SB transposon mediated long-term and stable reporter gene expression in human primary T-cells. We observed that delivery of SB transposase-encoding plasmid in trans effectively mediated stable gene expression in primary T-cells, exhibiting about a 3-fold increase (11% vs. 3% with 10 microgram plasmid on day 21) in potency in comparison with the cis vector (p<0.0001). In addition, a transposase mutant construct was incapable of mediating stable gene expression in human PBLs (n=6, p<0.0001), confirming that catalytic DDE domain is necessary for transposition in human primary T-cells. Immunophenotyping analysis in transposed T-cells showed that both CD4 and CD8 T-cells were transgene positive. SB-mediated high level of transgene expression in human T-cells was maintained in culture for at least 4 months without losing observable expression. Southern hybridization analysis showed a variety of transposon integrants among the 6 DsRed positive T-cell clones and no transposon sequences identifiable in the 2 DsRed negative clones. Sequencing of transposon:chromosome junctions in 5 out of 6 transposed T-cell clones confirmed that stable gene expression was due to SB-mediated transposition. In other studies, PBLs were successfully transfected using the SB transposon system and shown to stably and functionally express a fusion protein consisting of a surface receptor useful for positive T-cell selection and a “suicide” gene useful for elimination of transfected T-cells after chemotherapy. This study is the first report demonstrating that the SB transposon system can mediate stable gene transfer in human primary PBLs, which may be more advantageous for T-cell based gene therapies over widely used virus-based or conventional mammalian DNA vectors in terms of simplicity, stability, efficiency and safety.
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Miskey, Csaba, Lisa Kesselring, Irma Querques, György Abrusán, Orsolya Barabas et Zoltán Ivics. « Engineered Sleeping Beauty transposase redirects transposon integration away from genes ». Nucleic Acids Research 50, no 5 (21 février 2022) : 2807–25. http://dx.doi.org/10.1093/nar/gkac092.
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Abstract The Sleeping Beauty (SB) transposon system is a popular tool for genome engineering, but random integration into the genome carries a certain genotoxic risk in therapeutic applications. Here we investigate the role of amino acids H187, P247 and K248 in target site selection of the SB transposase. Structural modeling implicates these three amino acids located in positions analogous to amino acids with established functions in target site selection in retroviral integrases and transposases. Saturation mutagenesis of these residues in the SB transposase yielded variants with altered target site selection properties. Transposon integration profiling of several mutants reveals increased specificity of integrations into palindromic AT repeat target sequences in genomic regions characterized by high DNA bendability. The H187V and K248R mutants redirect integrations away from exons, transcriptional regulatory elements and nucleosomal DNA in the human genome, suggesting enhanced safety and thus utility of these SB variants in gene therapy applications.
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Kesselring, Lisa, Csaba Miskey, Cecilia Zuliani, Irma Querques, Vladimir Kapitonov, Andrea Laukó, Anita Fehér et al. « A single amino acid switch converts the Sleeping Beauty transposase into an efficient unidirectional excisionase with utility in stem cell reprogramming ». Nucleic Acids Research 48, no 1 (28 novembre 2019) : 316–31. http://dx.doi.org/10.1093/nar/gkz1119.
Texte intégralRésumé :
Abstract The Sleeping Beauty (SB) transposon is an advanced tool for genetic engineering and a useful model to investigate cut-and-paste DNA transposition in vertebrate cells. Here, we identify novel SB transposase mutants that display efficient and canonical excision but practically unmeasurable genomic re-integration. Based on phylogenetic analyses, we establish compensating amino acid replacements that fully rescue the integration defect of these mutants, suggesting epistasis between these amino acid residues. We further show that the transposons excised by the exc+/int− transposase mutants form extrachromosomal circles that cannot undergo a further round of transposition, thereby representing dead-end products of the excision reaction. Finally, we demonstrate the utility of the exc+/int− transposase in cassette removal for the generation of reprogramming factor-free induced pluripotent stem cells. Lack of genomic integration and formation of transposon circles following excision is reminiscent of signal sequence removal during V(D)J recombination, and implies that cut-and-paste DNA transposition can be converted to a unidirectional process by a single amino acid change.
9
Yusa, Kosuke, Junji Takeda et Kyoji Horie. « Enhancement of Sleeping Beauty Transposition by CpG Methylation : Possible Role of Heterochromatin Formation ». Molecular and Cellular Biology 24, no 9 (1 mai 2004) : 4004–18. http://dx.doi.org/10.1128/mcb.24.9.4004-4018.2004.
Texte intégralRésumé :
ABSTRACT The Sleeping Beauty (SB) transposase is the most active transposase in vertebrate cells, and the SB transposon system has been used as a tool for insertional mutagenesis and gene delivery. Previous studies have indicated that the frequency of chromosomal transposition is considerably higher in mouse germ cells than in mouse embryonic stem cells, suggesting the existence of unknown mechanisms that regulate SB transposition. Here, we demonstrated that CpG methylation of the transposon region enhances SB transposition. The transposition efficiencies of a methylated transposon and an unmethylated transposon which had been targeted in the same genomic loci by recombination-mediated cassette exchange in mouse erythroleukemia cells were compared, and at least a 100-fold increase was observed in the methylated transposon. CpG methylation also enhanced transposition from plasmids into the genome. Chromatin immunoprecipitation assays revealed that histone H3 methylated at lysine-9, a hallmark of condensed heterochromatin, was enriched at the methylated transposon, whereas the unmethylated transposon formed a relaxed euchromatin structure, as evidenced by enrichment of acetylated histone H3 and reporter gene expression. Possible roles of heterochromatin formation in the transposition reaction are discussed. Our findings indicate a novel relationship between CpG methylation and transposon mobilization.
10
Yant, Stephen R., et Mark A. Kay. « Nonhomologous-End-Joining Factors Regulate DNA Repair Fidelity during Sleeping Beauty Element Transposition in Mammalian Cells ». Molecular and Cellular Biology 23, no 23 (1 décembre 2003) : 8505–18. http://dx.doi.org/10.1128/mcb.23.23.8505-8518.2003.
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ABSTRACT Herein, we report that the DNA-dependent protein kinase (DNA-PK) regulates the DNA damage introduced during Sleeping Beauty (SB) element excision and reinsertion in mammalian cells. Using both plasmid- and chromosome-based mobility assays, we analyzed the repair of transposase-induced double-stranded DNA breaks in cells deficient in either the DNA-binding subunit of DNA-PK (Ku) or its catalytic subunit (DNA-PKcs). We found that the free 3′ overhangs left after SB element excision were efficiently and accurately processed by the major Ku-dependent nonhomologous-end-joining pathway. Rejoining of broken DNA molecules in the absence of Ku resulted in extensive end degradation at the donor site and greatly increased the frequency of recombination with ectopic templates. Therefore, the major DNA-PK-dependent DNA damage response predominates over more-error-prone repair pathways and thereby facilitates high-fidelity DNA repair during transposon mobilization in mammalian cells. Although transposable elements were not found to be efficiently circularized after transposase-mediated excision, DNA-PK deficiency supported more-frequent transposase-mediated element insertion than was found in wild-type controls. We conclude that, based on its ability to regulate excision site junctional diversity and transposon insertion frequency, DNA-PK serves an important protective role during transpositional recombination in mammals.