1
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Fogg JM, Judge AK, Stricker E, Chan HL, Zechiedrich L. Supercoiling and looping promote DNA base accessibility and coordination among distant sites. Nat Commun 2021; 12:5683. [PMID: 34584096 PMCID: PMC8478907 DOI: 10.1038/s41467-021-25936-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 08/30/2021] [Indexed: 11/29/2022] Open
Abstract
DNA in cells is supercoiled and constrained into loops and this supercoiling and looping influence every aspect of DNA activity. We show here that negative supercoiling transmits mechanical stress along the DNA backbone to disrupt base pairing at specific distant sites. Cooperativity among distant sites localizes certain sequences to superhelical apices. Base pair disruption allows sharp bending at superhelical apices, which facilitates DNA writhing to relieve torsional strain. The coupling of these processes may help prevent extensive denaturation associated with genomic instability. Our results provide a model for how DNA can form short loops, which are required for many essential processes, and how cells may use DNA loops to position nicks to facilitate repair. Furthermore, our results reveal a complex interplay between site-specific disruptions to base pairing and the 3-D conformation of DNA, which influences how genomes are stored, replicated, transcribed, repaired, and many other aspects of DNA activity.
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Affiliation(s)
- Jonathan M Fogg
- Department of Molecular Virology and Microbiology, Houston, TX, USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX, USA
- Department of Pharmacology and Chemical Biology, Houston, TX, USA
| | - Allison K Judge
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX, USA
| | - Erik Stricker
- Department of Molecular Virology and Microbiology, Houston, TX, USA
| | - Hilda L Chan
- Graduate Program in Immunology and Microbiology, Houston, TX, USA
- Medical Scientist Training Program, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - Lynn Zechiedrich
- Department of Molecular Virology and Microbiology, Houston, TX, USA.
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX, USA.
- Department of Pharmacology and Chemical Biology, Houston, TX, USA.
- Graduate Program in Immunology and Microbiology, Houston, TX, USA.
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2
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Arévalo-Soliz LM, Hardee CL, Fogg JM, Corman NR, Noorbakhsh C, Zechiedrich L. Improving therapeutic potential of non-viral minimized DNA vectors. CELL & GENE THERAPY INSIGHTS 2020; 6:1489-1505. [PMID: 33953961 PMCID: PMC8095377 DOI: 10.18609/cgti.2020.163] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The tragic deaths of three patients in a recent AAV-based X-linked myotubular myopathy clinical trial highlight once again the pressing need for safe and reliable gene delivery vectors. Non-viral minimized DNA vectors offer one possible way to meet this need. Recent pre-clinical results with minimized DNA vectors have yielded promising outcomes in cancer therapy, stem cell therapy, stem cell reprograming, and other uses. Broad clinical use of these vectors, however, remains to be realized. Further advances in vector design and production are ongoing. An intriguing and promising potential development results from manipulation of the specific shape of non-viral minimized DNA vectors. By improving cellular uptake and biodistribution specificity, this approach could impact gene therapy, DNA nanotechnology, and personalized medicine.
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Affiliation(s)
- Lirio M Arévalo-Soliz
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Cinnamon L Hardee
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jonathan M Fogg
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Nathan R Corman
- Rural Medical Education Program, University of Illinois College of Medicine, Rockford, IL 61107, USA
| | - Cameron Noorbakhsh
- Weiss School of Natural Sciences, Rice University, Houston, TX 77005, USA
| | - Lynn Zechiedrich
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
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3
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Sperlea T, Muth L, Martin R, Weigel C, Waldminghaus T, Heider D. gammaBOriS: Identification and Taxonomic Classification of Origins of Replication in Gammaproteobacteria using Motif-based Machine Learning. Sci Rep 2020; 10:6727. [PMID: 32317695 PMCID: PMC7174414 DOI: 10.1038/s41598-020-63424-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 03/31/2020] [Indexed: 01/23/2023] Open
Abstract
The biology of bacterial cells is, in general, based on information encoded on circular chromosomes. Regulation of chromosome replication is an essential process that mostly takes place at the origin of replication (oriC), a locus unique per chromosome. Identification of high numbers of oriC is a prerequisite for systematic studies that could lead to insights into oriC functioning as well as the identification of novel drug targets for antibiotic development. Current methods for identifying oriC sequences rely on chromosome-wide nucleotide disparities and are therefore limited to fully sequenced genomes, leaving a large number of genomic fragments unstudied. Here, we present gammaBOriS (Gammaproteobacterial oriC Searcher), which identifies oriC sequences on gammaproteobacterial chromosomal fragments. It does so by employing motif-based machine learning methods. Using gammaBOriS, we created BOriS DB, which currently contains 25,827 gammaproteobacterial oriC sequences from 1,217 species, thus making it the largest available database for oriC sequences to date. Furthermore, we present gammaBOriTax, a machine-learning based approach for taxonomic classification of oriC sequences, which was trained on the sequences in BOriS DB. Finally, we extracted the motifs relevant for identification and classification decisions of the models. Our results suggest that machine learning sequence classification approaches can offer great support in functional motif identification.
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Affiliation(s)
- Theodor Sperlea
- Faculty of Mathematics and Computer Science, University of Marburg, Hans-Meerwein-Str. 6, D-35032, Marburg, Lahn, Germany
| | - Lea Muth
- Faculty of Mathematics and Computer Science, University of Marburg, Hans-Meerwein-Str. 6, D-35032, Marburg, Lahn, Germany
| | - Roman Martin
- Faculty of Mathematics and Computer Science, University of Marburg, Hans-Meerwein-Str. 6, D-35032, Marburg, Lahn, Germany
| | - Christoph Weigel
- Institute of Biotechnology, Faculty III, Technische Universität Berlin (TUB), Straße des 17. Juni 135, D-10623, Berlin, Germany
| | - Torsten Waldminghaus
- Chromosome Biology Group, LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, D-35043, Marburg, Lahn, Germany
| | - Dominik Heider
- Faculty of Mathematics and Computer Science, University of Marburg, Hans-Meerwein-Str. 6, D-35032, Marburg, Lahn, Germany.
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4
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Płachetka M, Żyła-Uklejewicz D, Weigel C, Donczew R, Donczew M, Jakimowicz D, Zawilak-Pawlik A, Zakrzewska-Czerwinska J. Streptomycete origin of chromosomal replication with two putative unwinding elements. MICROBIOLOGY-SGM 2019; 165:1365-1375. [PMID: 31592764 DOI: 10.1099/mic.0.000859] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
DNA replication is controlled mostly at the initiation step. In bacteria, replication of the chromosome starts at a single origin of replication called oriC. The initiator protein, DnaA, binds to specific sequences (DnaA boxes) within oriC and assembles into a filament that promotes DNA double helix opening within the DNA unwinding element (DUE). This process has been thoroughly examined in model bacteria, including Escherichia coli and Bacillus subtilis, but we have a relatively limited understanding of chromosomal replication initiation in other species. Here, we reveal new details of DNA replication initiation in Streptomyces, a group of Gram-positive soil bacteria that possesses a long linear (8-10 Mbps) and GC-rich chromosome with a centrally positioned oriC. We used comprehensive in silico, in vitro and in vivo analyses to better characterize the structure of Streptomyces oriC. We identified 14 DnaA-binding motifs and determined the consensus sequence of the DnaA box. Unexpectedly, our in silico analysis using the WebSIDD algorithm revealed the presence of two putative Streptomyces DUEs (DUE1 and DUE2) located very near one another toward the 5' end of the oriC region. In vitro P1 nuclease assay revealed that DNA unwinding occurs at both of the proposed sites, but using an in vivo replication initiation point mapping, we were able to confirm only one of them (DUE2). The previously observed transcriptional activity of the Streptomyces oriC region may help explain the current results. We speculate that transcription itself could modulate oriC activity in Streptomyces by determining whether DNA unwinding occurs at DUE1 or DUE2.
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Affiliation(s)
- Małgorzata Płachetka
- Department of Molecular Microbiology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Dorota Żyła-Uklejewicz
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Christoph Weigel
- Institute of Biotechnology, Faculty III, Technical University Berlin (TUB), Berlin, Germany
| | - Rafał Donczew
- Present address: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.,Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Magdalena Donczew
- Present address: Center for Infectious Disease, Seattle, WA, USA.,Department of Molecular Microbiology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Dagmara Jakimowicz
- Department of Molecular Microbiology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Anna Zawilak-Pawlik
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
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5
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Silva-Santos AR, Alves CP, Monteiro G, Azevedo AM, Prazeres DMF. Multimodal chromatography of supercoiled minicircles: A closer look into DNA-ligand interactions. Sep Purif Technol 2019. [DOI: 10.1016/j.seppur.2018.11.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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6
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Orlov MA, Ryasik AA, Sorokin AA. Destabilization of the DNA Duplex of Actively Replicating Promoters of T7-Like Bacteriophages. Mol Biol 2018. [DOI: 10.1134/s0026893318050114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Hagedorn C, Gogol-Döring A, Schreiber S, Epplen JT, Lipps HJ. Genome-wide profiling of S/MAR-based replicon contact sites. Nucleic Acids Res 2017; 45:7841-7854. [PMID: 28609784 PMCID: PMC5570033 DOI: 10.1093/nar/gkx522] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 06/05/2017] [Indexed: 11/14/2022] Open
Abstract
Autonomously replicating vectors represent a simple and versatile model system for genetic modifications, but their localization in the nucleus and effect on endogenous gene expression is largely unknown. Using circular chromosome conformation capture we mapped genomic contact sites of S/MAR-based replicons in HeLa cells. The influence of cis-active sequences on genomic localization was assessed using replicons containing either an insulator sequence or an intron. While the original and the insulator-containing replicons displayed distinct contact sites, the intron-containing replicon showed a rather broad genomic contact pattern. Our results indicate a preference for certain chromatin structures and a rather non-dynamic behaviour during mitosis. Independent of inserted cis-active elements established vector molecules reside preferentially within actively transcribed regions, especially within promoter sequences and transcription start sites. However, transcriptome analyses revealed that established S/MAR-based replicons do not alter gene expression profiles of host genome. Knowledge of preferred contact sites of exogenous DNA, e.g. viral or non-viral episomes, contribute to our understanding of episome behaviour in the nucleus and can be used for vector improvement and guiding of DNA sequences to specific subnuclear sites.
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Affiliation(s)
- Claudia Hagedorn
- University of Witten/Herdecke, ZBAF, Institute of Cell Biology, Stockumer Strasse 10, 58453 Witten, Germany
| | - Andreas Gogol-Döring
- Technische Hochschule Mittelhessen (University of Applied Sciences), Department of Bioinformatics, Wiesenstrasse 14, 35390 Gießen, Germany
| | - Sabrina Schreiber
- Department of Human Genetics, Ruhr-University, Universitätsstraße 150, 44801 Bochum, Germany
| | - Jörg T Epplen
- University of Witten/Herdecke, ZBAF, Institute of Cell Biology, Stockumer Strasse 10, 58453 Witten, Germany.,Department of Human Genetics, Ruhr-University, Universitätsstraße 150, 44801 Bochum, Germany
| | - Hans J Lipps
- University of Witten/Herdecke, ZBAF, Institute of Cell Biology, Stockumer Strasse 10, 58453 Witten, Germany
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8
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Zhang Z, Kukita C, Humayun MZ, Saier MH. Environment-directed activation of the Escherichia coliflhDC operon by transposons. MICROBIOLOGY-SGM 2017; 163:554-569. [PMID: 28100305 DOI: 10.1099/mic.0.000426] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The flagellar system in Escherichia coli K12 is expressed under the control of the flhDC-encoded master regulator FlhDC. Transposition of insertion sequence (IS) elements to the upstream flhDC promoter region up-regulates transcription of this operon, resulting in a more rapid motility. Wang and Wood (ISME J 2011;5:1517-1525) provided evidence that insertion of IS5 into upstream activating sites occurs at higher rates in semi-solid agar media in which swarming behaviour is allowed as compared with liquid or solid media where swarming cannot occur. We confirm this conclusion and show that three IS elements, IS1, IS3 and IS5, transpose to multiple upstream sites within a 370 bp region of the flhDC operon control region. Hot spots for IS insertion correlate with positions of stress-induced DNA duplex destabilization (SIDD). We show that IS insertion occurs at maximal rates in 0.24 % agar, with rates decreasing dramatically with increasing or decreasing agar concentrations. In mixed cultures, we show that these mutations preferentially arise from the wild-type parent at frequencies of up to 3×10-3 cell-1 day-1 when the inoculated parental and co-existing IS-activated mutant cells are entering the stationary growth phase. We rigorously show that the apparent increased mutation frequencies cannot be accounted for by increased swimming or by increased growth under the selective conditions used. Thus, our data are consistent with the possibility that appropriate environmental conditions, namely those that permit but hinder flagellar rotation, result in the activation of a mutational pathway that involves IS element insertion upstream of the flhDC operon.
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Affiliation(s)
- Zhongge Zhang
- Department of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - Chika Kukita
- Department of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - M Zafri Humayun
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ 07101-1709, USA
| | - Milton H Saier
- Department of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
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9
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Stavrou EF, Lazaris VM, Giannakopoulos A, Papapetrou E, Spyridonidis A, Zoumbos NC, Gkountis A, Athanassiadou A. The β-globin Replicator greatly enhances the potential of S/MAR based episomal vectors for gene transfer into human haematopoietic progenitor cells. Sci Rep 2017; 7:40673. [PMID: 28106085 PMCID: PMC5247744 DOI: 10.1038/srep40673] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 12/09/2016] [Indexed: 11/08/2022] Open
Abstract
Specific human chromosomal elements enhance the performance of episomal gene-transfer vectors. S/MAR-based episomal vector pEPI-eGFP transfects CD34+ haematopoietic cells, but only transiently. To address this issue we reinforced (1) transgene transcription by replacing the CMV promoter driving eGFP with the EF1/HTLV or SFFV promoters to produce vectors pEPI-EF1/HTLV and pEPI-SFFV, respectively; and (2) plasmid replication by inserting the replication-Initiation Region (IR) from the β-globin locus into vector pEPI-SFFV to produce vector pEP-IR. All vectors supported stable transfections in K562 cells. Transfections of CD34+ cells from peripheral blood of healthy donors reached 30% efficiency. Upon evaluation of CD34+/eGFP+ cells in colony-forming cell (CFC) assays, vector pEP-IR showed superior performance after 14 days, by fluorescent microscopy: 100% eGFP+-colonies against 0% for pEPI-eGFP, 56.9% for pEPI-SFFV and 49.8% for pEPI-EF1/HTLV; 50% more plasmid copies per cell and 3-fold eGFP expression compared to the latter two constructs, by quantitative (q)PCR and RT-qPCR, respectively. Importantly, the establishment rate in CFC assays was 15% for pEP-IR against 5.5% for pEPI-SFFV and 5% for pEPI-EF1/HTLV. Vector pEP-IR shows extremely low delivery rate but supports eGFP expression in thalassaemic mouse haematopoietic progenitor cells. The IR is a novel human control element for improved episomal gene transfer into progenitor cells.
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Affiliation(s)
- Eleana F. Stavrou
- Department of General Biology, School of Medicine, University of Patras, Greece
| | | | | | - Eirini Papapetrou
- Department of General Biology, School of Medicine, University of Patras, Greece
| | - Alexandros Spyridonidis
- Haematology Unit Department of Internal Medicine, School of Medicine, University of Patras, Greece
| | - Nikolas C. Zoumbos
- Haematology Unit Department of Internal Medicine, School of Medicine, University of Patras, Greece
| | - Antonis Gkountis
- Gene and Cell Therapy Center, Haematology Department-BMT Unit, George Papanicolaou Hospital, Thessaloniki, Greece
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Daga A, Ansari A, Pandya M, Shah K, Patel S, Rawal R, Umrania V. Significant Role of Segmental Duplications and SIDD Sites in Chromosomal Translocations of Hematological Malignancies: A Multi-parametric Bioinformatic Analysis. Interdiscip Sci 2016; 10:467-475. [PMID: 27896663 DOI: 10.1007/s12539-016-0203-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 11/12/2016] [Accepted: 11/14/2016] [Indexed: 10/20/2022]
Abstract
Recurrent non-random chromosomal translocations are hallmark characteristics of leukemogenesis, and however, molecular mechanisms underlying these rearrangements are less explored. The fundamental question is, why and how chromosomes break and reunite so precisely in the genome. Meticulous understanding of mechanism leading to chromosomal rearrangement can be achieved by characterizing breakpoints. To address this hypothesis, a novel multi-parametric computational approach for characterization of major leukemic translocations within and around breakpoint region was performed. To best of our knowledge, this bioinformatic analysis is unique in finding the presence of segmental duplications (SDs) flanking breakpoints of all major leukemic translocation. Breakpoint islands (BpIs) were analyzed for stress-induced duplex destabilization (SIDD) sites along with other complex genomic architecture and physicochemical properties. Our study distinctly emphasizes on the probable correlative role of SDs, SIDD sites and various genomic features in the occurrence of breakpoints. Further, it also highlights potential features which may be playing a crucial role in causing double-strand breaks, leading to translocation.
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Affiliation(s)
- Aditi Daga
- Department of Microbiology, MVM Science College, Saurashtra University, Near Under Bridge, Kalawad Road, Rajkot, Gujarat, 360007, India
| | - Afzal Ansari
- BIT Virtual Institute of Bioinformatics (GCRI Node), GSBTM, Gandhinagar, Gujarat, India
- BIT Virtual Institute of Bioinformatics (GCRI Node), Division of Medicinal Chemistry and Pharmacogenomics, The Gujarat Cancer and Research Institute, NCH Campus, Asarwa, Ahmedabad, Gujarat, 380016, India
| | - Medha Pandya
- Department of Bioinformatics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar, Gujarat, 364022, India
- Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar, Gujarat, 364022, India
| | - Krupa Shah
- Division of Medicinal Chemistry and Pharmacogenomics, Department of Cancer Biology, The Gujarat Cancer and Research Institute, NCH Campus, Asarwa, Ahmedabad, Gujarat, 380016, India
| | - Shanaya Patel
- Division of Medicinal Chemistry and Pharmacogenomics, Department of Cancer Biology, The Gujarat Cancer and Research Institute, NCH Campus, Asarwa, Ahmedabad, Gujarat, 380016, India
| | - Rakesh Rawal
- Division of Medicinal Chemistry and Pharmacogenomics, Department of Cancer Biology, The Gujarat Cancer and Research Institute, NCH Campus, Asarwa, Ahmedabad, Gujarat, 380016, India.
| | - Valentina Umrania
- Department of Microbiology, MVM Science College, Saurashtra University, Near Under Bridge, Kalawad Road, Rajkot, Gujarat, 360007, India
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Makowski Ł, Donczew R, Weigel C, Zawilak-Pawlik A, Zakrzewska-Czerwińska J. Initiation of Chromosomal Replication in Predatory Bacterium Bdellovibrio bacteriovorus. Front Microbiol 2016; 7:1898. [PMID: 27965633 PMCID: PMC5124646 DOI: 10.3389/fmicb.2016.01898] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 11/11/2016] [Indexed: 11/18/2022] Open
Abstract
Bdellovibrio bacteriovorus is a small Gram-negative predatory bacterium that attacks other Gram-negative bacteria, including many animal, human, and plant pathogens. This bacterium exhibits a peculiar biphasic life cycle during which two different types of cells are produced: non-replicating highly motile cells (the free-living phase) and replicating cells (the intracellular-growth phase). The process of chromosomal replication in B. bacteriovorus must therefore be temporally and spatially regulated to ensure that it is coordinated with cell differentiation and cell cycle progression. Recently, B. bacteriovorus has received considerable research interest due to its intriguing life cycle and great potential as a prospective antimicrobial agent. Although, we know that chromosomal replication in bacteria is mainly regulated at the initiation step, no data exists about this process in B. bacteriovorus. We report the first characterization of key elements of initiation of chromosomal replication – DnaA protein and oriC region from the predatory bacterium, B. bacteriovorus. In vitro studies using different approaches demonstrate that the B. bacteriovorus oriC (BdoriC) is specifically bound and unwound by the DnaA protein. Sequence comparison of the DnaA-binding sites enabled us to propose a consensus sequence for the B. bacteriovorus DnaA box [5′-NN(A/T)TCCACA-3′]. Surprisingly, in vitro analysis revealed that BdoriC is also bound and unwound by the host DnaA proteins (relatively distantly related from B. bacteriovorus). We compared the architecture of the DnaA–oriC complexes (orisomes) in homologous (oriC and DnaA from B. bacteriovorus) and heterologous (BdoriC and DnaA from prey, Escherichia coli or Pseudomonas aeruginosa) systems. This work provides important new entry points toward improving our understanding of the initiation of chromosomal replication in this predatory bacterium.
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Affiliation(s)
- Łukasz Makowski
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy - Polish Academy of Sciences Wrocław, Poland
| | - Rafał Donczew
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy - Polish Academy of Sciences Wrocław, Poland
| | | | - Anna Zawilak-Pawlik
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy - Polish Academy of Sciences Wrocław, Poland
| | - Jolanta Zakrzewska-Czerwińska
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy - Polish Academy of SciencesWrocław, Poland; Department of Molecular Microbiology, Faculty of Biotechnology, University of WrocławWrocław, Poland
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12
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Controlling gene expression by DNA mechanics: emerging insights and challenges. Biophys Rev 2016; 8:23-32. [PMID: 28510218 DOI: 10.1007/s12551-016-0243-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 07/11/2016] [Indexed: 12/22/2022] Open
Abstract
Transcription initiation is a major control point for the precise regulation of gene expression. Our knowledge of this process has been mainly derived from protein-centric studies wherein cis-regulatory DNA sequences play a passive role, mainly in arranging the protein machinery to coalesce at the transcription start sites of genes in a spatial and temporal-specific manner. However, this is a highly dynamic process in which molecular motors such as RNA polymerase II (RNAPII), helicases, and other transcription factors, alter the level of mechanical force in DNA, rather than simply a set of static DNA-protein interactions. The double helix is a fiber that responds to flexural and torsional stress, which if accumulated, can affect promoter output as well as change DNA and chromatin structure. The relationship between DNA mechanics and the control of early transcription initiation events has been under-investigated. Genomic techniques to display topological stress and conformational variation in DNA across the mammalian genome provide an exciting new insight on the role of DNA mechanics in the early stages of the transcription cycle. Without understanding how torsional and flexural stresses are generated, transmitted, and dissipated, no model of transcription will be complete and accurate.
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Dormiani K, Mir Mohammad Sadeghi H, Sadeghi-Aliabadi H, Forouzanfar M, Baharvand H, Ghaedi K, Nasr-Esfahani MH. Rational Development of A Polycistronic Plasmid with A CpG-Free Bacterial Backbone as A Potential Tool for Direct Reprogramming. CELL JOURNAL 2016; 18:565-581. [PMID: 28042541 PMCID: PMC5086335 DOI: 10.22074/cellj.2016.4723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 05/04/2016] [Indexed: 12/04/2022]
Abstract
Objective Induced pluripotent stem cells are generated from somatic cells by direct reprogramming. These reprogrammed pluripotent cells have different applications in biomedical fields such as regenerative medicine. Although viral vectors are widely used for
efficient reprogramming, they have limited applications in the clinic due to the risk for
immunogenicity and insertional mutagenesis. Accordingly, we designed and developed a
small, non-integrating plasmid named pLENSO/Zeo as a 2A-mediated polycistronic expression vector.
Materials and Methods In this experimental study, we developed a single plasmid which
includes a single expression cassette containing open reading frames of human LIN28,
NANOG, SOX2 and OCT4 along with an EGFP reporter gene. Each reprogramming factor is separated by an intervening sequence that encodes a 2A self-processing peptide.
The reprogramming cassette is located downstream of a CMV promoter. The vector is
easily propagated in the E. coli GT115 strain through a CpG-depleted vector backbone.
We evaluated the stability of the constructed vector bioinformatically, and its ability to stoichiometric expression of the reprogramming factors using quantitative molecular methods
analysis after transient transfection into HEK293 cells.
Results In the present study, we developed a nonviral episomal vector named pLENSO/
Zeo. Our results demonstrated the general structural stability of the plasmid DNA. This
relatively small vector showed concomitant, high-level expression of the four reprogramming factors with similar titers, which are considered as the critical parameters for efficient
and consistent reprogramming.
Conclusion According to our experimental results, this stable extrachromosomal plasmid expresses reliable amounts of four reprogramming factors simultaneously. Consequently, these promising results encouraged us to evaluate the capability of pLENSO/Zeo
as a simple and feasible tool for generation of induced pluripotent stem cells from primary
cells in the future.
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Affiliation(s)
- Kianoush Dormiani
- Department of Pharmaceutical Biotechnology and Isfahan Pharmaceutical Sciences Research Center, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran; Department of Molecular Biotechnology, Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Hamid Mir Mohammad Sadeghi
- Department of Pharmaceutical Biotechnology and Isfahan Pharmaceutical Sciences Research Center, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Hojjat Sadeghi-Aliabadi
- Department of Pharmaceutical Biotechnology and Isfahan Pharmaceutical Sciences Research Center, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Mahboobeh Forouzanfar
- Department of Molecular Biotechnology, Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Hossein Baharvand
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran; Department of Developmental Biology, University of Science and Culture, ACECR, Tehran, Iran
| | - Kamran Ghaedi
- Department of Molecular Biotechnology, Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran; Department of Biology, School of Sciences, University of Isfahan, Isfahan, Iran
| | - Mohammad Hossein Nasr-Esfahani
- Department of Molecular Biotechnology, Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
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Levens D, Baranello L, Kouzine F. Controlling gene expression by DNA mechanics: emerging insights and challenges. Biophys Rev 2016; 8:259-268. [PMID: 28510225 DOI: 10.1007/s12551-016-0216-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 07/11/2016] [Indexed: 12/11/2022] Open
Abstract
Transcription initiation is a major control point for the precise regulation of gene expression. Our knowledge of this process has been mainly derived from protein-centric studies wherein cis-regulatory DNA sequences play a passive role, mainly in arranging the protein machinery to coalesce at the transcription start sites of genes in a spatial and temporal-specific manner. However, this is a highly dynamic process in which molecular motors such as RNA polymerase II (RNAPII), helicases, and other transcription factors, alter the level of mechanical force in DNA, rather than simply a set of static DNA-protein interactions. The double helix is a fiber that responds to flexural and torsional stress, which if accumulated, can affect promoter output as well as change DNA and chromatin structure. The relationship between DNA mechanics and the control of early transcription initiation events has been under-investigated. Genomic techniques to display topological stress and conformational variation in DNA across the mammalian genome provide an exciting new insight on the role of DNA mechanics in the early stages of the transcription cycle. Without understanding how torsional and flexural stresses are generated, transmitted, and dissipated, no model of transcription will be complete and accurate.
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Affiliation(s)
- David Levens
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Laura Baranello
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Fedor Kouzine
- Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
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15
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Fukuma M, Ganmyo Y, Miura O, Ohyama T, Shimizu N. Cloning and Characterization of a Human Genomic Sequence that Alleviates Repeat-Induced Gene Silencing. PLoS One 2016; 11:e0153338. [PMID: 27078685 PMCID: PMC4831671 DOI: 10.1371/journal.pone.0153338] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/28/2016] [Indexed: 01/06/2023] Open
Abstract
Plasmids bearing a mammalian replication initiation region (IR) and a nuclear matrix attachment region (MAR) are spontaneously amplified in transfected mammalian cells, and such amplification generates chromosomal homogeneously staining regions (HSRs) or extrachromosomal double minutes (DMs). This method provides a novel, efficient, and rapid way to establish cells that stably produce high levels of recombinant proteins. However, because IR/MAR plasmids are amplified as repeats, they are frequently targeted by repeat-induced gene silencing (RIGS), which silences a variety of repeated sequences in transgenes and the genome. To address this problem, we developed a novel screening system using the IR/MAR plasmid to isolate human genome sequences that alleviate RIGS. The screen identified a 3,271 bp sequence (B-3-31) that elevated transgene expression without affecting the amplification process. Neither non-B structure (i.e., the inverted repeats or bending) nor known epigenetic modifier elements such as MARs, insulators, UCOEs, or STARs could explain the anti-silencing activity of B-3-31. Instead, the activity was distributed throughout the entire B-3-31 sequence, which was extremely A/T-rich and CpG-poor. Because B-3-31 effectively and reproducibly alleviated RIGS of repeated genes, it could be used to increase recombinant protein production.
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Affiliation(s)
- Miki Fukuma
- Graduate School of Biosphere Science, Hiroshima University, Higashi-hiroshima, Hiroshima, Japan
| | - Yuto Ganmyo
- Graduate School of Biosphere Science, Hiroshima University, Higashi-hiroshima, Hiroshima, Japan
| | - Osamu Miura
- Graduate School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan
| | - Takashi Ohyama
- Graduate School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan
| | - Noriaki Shimizu
- Graduate School of Biosphere Science, Hiroshima University, Higashi-hiroshima, Hiroshima, Japan
- * E-mail:
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16
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Pratihar AS, Tripathi VP, Yadav MP, Dubey DD. Chromosomal context and replication properties of ARS plasmids in Schizosaccharomyces pombe. J Biosci 2015; 40:845-53. [PMID: 26648030 DOI: 10.1007/s12038-015-9572-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Short, specific DNA sequences called as Autonomously Replicating Sequence (ARS) elements function as plasmid as well as chromosomal replication origins in yeasts. As compared to ARSs, different chromosomal origins vary greatly in their efficiency and timing of replication probably due to their wider chromosomal context. The two Schizosaccharomyces pombe ARS elements, ars727 and ars2004, represent two extremities in their chromosomal origin activity - ars727 is inactive and late replicating, while ars2004 is a highly active, early-firing origin. To determine the effect of chromosomal context on the activity of these ARS elements, we have cloned them with their extended chromosomal context as well as in the context of each other in both orientations and analysed their replication efficiency by ARS and plasmid stability assays. We found that these ARS elements retain their origin activity in their extended/altered context. However, deletion of a 133-bp region of the previously reported ars727- associated late replication enforcing element (LRE) caused advancement in replication timing of the resulting plasmid. These results confirm the role of LRE in directing plasmid replication timing and suggest that the plasmid origin efficiency of ars2004 or ars727 remains unaltered by the extended chromosomal context.
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Affiliation(s)
- Aditya S Pratihar
- Department of Biotechnology, Dayanand Academy of Management Studies, Govind Nagar, Kanpur, U.P. 208006, India
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17
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Abstract
By regulating access to the genetic code, DNA supercoiling strongly affects DNA metabolism. Despite its importance, however, much about supercoiled DNA (positively supercoiled DNA, in particular) remains unknown. Here we use electron cryo-tomography together with biochemical analyses to investigate structures of individual purified DNA minicircle topoisomers with defined degrees of supercoiling. Our results reveal that each topoisomer, negative or positive, adopts a unique and surprisingly wide distribution of three-dimensional conformations. Moreover, we uncover striking differences in how the topoisomers handle torsional stress. As negative supercoiling increases, bases are increasingly exposed. Beyond a sharp supercoiling threshold, we also detect exposed bases in positively supercoiled DNA. Molecular dynamics simulations independently confirm the conformational heterogeneity and provide atomistic insight into the flexibility of supercoiled DNA. Our integrated approach reveals the three-dimensional structures of DNA that are essential for its function. DNA supercoiling strongly affects its metabolism. By electron cryo-tomography, biochemical assays and molecular dynamics simulations, here the authors show that supercoiled DNA minicircles adopt unique and wide distributions of three-dimensional conformations, many with disrupted base pairs.
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18
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Daga A, Ansari A, Rawal R, Umrania V. Characterization of chromosomal translocation breakpoint sequences in solid tumours: "an in silico analysis". Open Med Inform J 2015; 9:1-8. [PMID: 25972994 PMCID: PMC4421838 DOI: 10.2174/1874431101509010001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 02/19/2015] [Accepted: 02/28/2015] [Indexed: 01/07/2023] Open
Abstract
Chromosomal translocations that results in formation and activation of fusion oncogenes are observed in numerous solid malignancies since years back. Expression of fusion kinases in these cancers drives the initiation & progression that ultimately leads to tumour development and thus comes out to be clinically imperative in terms of diagnosis and treatment of cancer. Nonetheless, molecular mechanisms beneath these translocations remained unexplored consequently limiting our knowledge of carcinogenesis and hence is the current field where further research is required. The issue of prime focus is the precision with which the chromosomes breaks and reunites within genome. Characterization of Genomic sequences located at Breakpoint region may direct us towards the thorough understanding of mechanism leading to chromosomal rearrangement. A unique computational multi-parametric analysis was performed for characterization of genomic sequence within and around breakpoint region. This study turns out to be novel as it reveals the occurrence of Segmental Duplications flanking the breakpoints of all translocation. Breakpoint Islands were also investigated for the presence of other intricate genomic architecture and various physico-chemical parameters. Our study particularly highlights the probable role of SDs and specific genomic features in precise chromosomal breakage. Additionally, it pinpoints the potential features that may be significant for double-strand breaks leading to chromosomal rearrangements.
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Affiliation(s)
- Aditi Daga
- Department of Microbiology, MVM Science College, Saurashtra University, Rajkot, Gujarat, India
| | - Afzal Ansari
- BIT Virtual Institute of Bioinformatics (GCRI Node), GSBTM, Gandhinagar, Gujarat, India
| | - Rakesh Rawal
- Department of Cancer Biology, The Gujarat Cancer & Research Institute, Ahmedabad, Gujarat, India
| | - Valentina Umrania
- Department of Microbiology, MVM Science College, Saurashtra University, Rajkot, Gujarat, India
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19
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20
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21
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Turan S, Qiao J, Madden S, Benham C, Kotz M, Schambach A, Bode J. Expanding Flp-RMCE options: the potential of Recombinase Mediated Twin-Site Targeting (RMTT). Gene 2014; 546:135-44. [DOI: 10.1016/j.gene.2014.06.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 06/02/2014] [Indexed: 01/02/2023]
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22
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Kymäläinen H, Appelt JU, Giordano FA, Davies AF, Ogilvie CM, Ahmed SG, Laufs S, Schmidt M, Bode J, Yáñez-Muñoz RJ, Dickson G. Long-term episomal transgene expression from mitotically stable integration-deficient lentiviral vectors. Hum Gene Ther 2014; 25:428-42. [PMID: 24483952 DOI: 10.1089/hum.2013.172] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nonintegrating gene delivery vectors have an improved safety profile compared with integrating vectors, but transgene retention is problematic as nonreplicating episomes are progressively and rapidly diluted out through cell division. We have developed an integration-deficient lentiviral vector (IDLV) system generating mitotically stable episomes capable of long-term transgene expression. We found that a transient cell cycle arrest at the time of transduction with IDLVs resulted in 13-45% of Chinese hamster ovary (CHO) cells expressing the transgene for over 100 cell generations in the absence of selection. The use of a scaffold/matrix attachment region did not result in improved episomal retention in this system, and episomes did not form after transduction with adeno-associated viral or minicircle vectors under the same conditions. Investigations into the episomal status of the vector genome using (1) linear amplification-mediated polymerase chain reaction followed by deep sequencing of vector-genome junctions, (2) Southern blotting, and (3) fluorescent in situ hybridization strongly suggest that the vector is not integrated in the vast majority of cells. In conclusion, we have developed an IDLV procedure generating mitotically stable episomes capable of long-term transgene expression. The application of this approach to stem cell populations could significantly improve the safety profile of a range of stem and progenitor cell gene therapies.
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Affiliation(s)
- Hanna Kymäläinen
- 1 School of Biological Sciences, Royal Holloway-University of London , Egham, Surrey TW20 0EX, United Kingdom
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23
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Luke JM, Carnes AE, Williams JA. Development of antibiotic-free selection system for safer DNA vaccination. Methods Mol Biol 2014; 1143:91-111. [PMID: 24715283 DOI: 10.1007/978-1-4939-0410-5_6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The use of antibiotic-resistance markers in DNA vaccines is discouraged by regulatory agencies due to various theoretical safety concerns. This chapter presents methodologies for the design and cloning of synthetic antigen genes into RNA-OUT encoding antibiotic-free DNA vaccine vectors that are additionally optimized to improve protein expression, and immunogenicity, compared to alternative kanamycin-resistant vectors. First, antigen targeting considerations are discussed in the context of immune response customization through MHC class I or class II directed antigen presentation; the example NTC868 series RNA-OUT vector system allows simultaneous cloning into multiple vectors that feature various transgene intracellular targeting destinations. Then a detailed flowchart for codon optimization and synthetic transgene design is presented. Finally in-depth methodologies for cloning transgenes into the NTC868 series RNA-OUT vector system are presented. The resultant antibiotic-free DNA vaccine vectors are a more potent, safer alternative to existing kanamycin resistance marker encoding vectors.
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Affiliation(s)
- Jeremy M Luke
- Nature Technology Corporation, 4701 Innovation Drive, Lincoln, NE, 68521, USA
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24
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Cameron ADS, Kröger C, Quinn HJ, Scally IK, Daly AJ, Kary SC, Dorman CJ. Transmission of an oxygen availability signal at the Salmonella enterica serovar Typhimurium fis promoter. PLoS One 2013; 8:e84382. [PMID: 24358360 PMCID: PMC3865300 DOI: 10.1371/journal.pone.0084382] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 11/14/2013] [Indexed: 11/19/2022] Open
Abstract
The nucleoid-associated protein FIS is a global regulator of gene expression and chromosome structure in Escherichia coli and Salmonella enterica. Despite the importance of FIS for infection and intracellular invasion, very little is known about the regulation of S. enterica fis expression. Under standard laboratory growth conditions, fis is highly expressed during rapid growth but is then silenced as growth slows. However, if cells are cultured in non-aerated conditions, fis expression is sustained during stationary phase. This led us to test whether the redox-sensing transcription factors ArcA and FNR regulate S. enterica fis. Deletion of FNR had no detectable effect, whereas deletion of ArcA had the unexpected effect of further elevating fis expression in stationary phase. ArcA required RpoS for induction of fis expression, suggesting that ArcA indirectly affects fis expression. Other putative regulators were found to play diverse roles: FIS acted directly as an auto-repressor (as expected), whereas CRP had little direct effect on fis expression. Deleting regions of the fis promoter led to the discovery of a novel anaerobically-induced transcription start site (Pfis-2) upstream of the primary transcription start site (Pfis-1). Promoter truncation also revealed that the shortest functional fis promoter was incapable of sustained expression. Moreover, fis expression was observed to correlate directly with DNA supercoiling in non-aerated conditions. Thus, the full-length S. enterica fis promoter region may act as a topological switch that is sensitive to stress-induced duplex destabilisation and up-regulates expression in non-aerated conditions.
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Affiliation(s)
- Andrew D. S. Cameron
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
- Department of Biology, University of Regina, Regina, SK, Canada
| | - Carsten Kröger
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Heather J. Quinn
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Isobel K. Scally
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Anne J. Daly
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Stefani C. Kary
- Department of Biology, University of Regina, Regina, SK, Canada
| | - Charles J. Dorman
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
- * E-mail:
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25
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Burger G, Gray MW, Forget L, Lang BF. Strikingly bacteria-like and gene-rich mitochondrial genomes throughout jakobid protists. Genome Biol Evol 2013; 5:418-38. [PMID: 23335123 PMCID: PMC3590771 DOI: 10.1093/gbe/evt008] [Citation(s) in RCA: 162] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The most bacteria-like mitochondrial genome known is that of the jakobid flagellate Reclinomonas americana NZ. This genome also encodes the largest known gene set among mitochondrial DNAs (mtDNAs), including the RNA subunit of RNase P (transfer RNA processing), a reduced form of transfer-messenger RNA (translational control), and a four-subunit bacteria-like RNA polymerase, which in other eukaryotes is substituted by a nucleus-encoded, single-subunit, phage-like enzyme. Further, protein-coding genes are preceded by potential Shine-Dalgarno translation initiation motifs. Whether similarly ancestral mitochondrial characters also exist in relatives of R. americana NZ is unknown. Here, we report a comparative analysis of nine mtDNAs from five distant jakobid genera: Andalucia, Histiona, Jakoba, Reclinomonas, and Seculamonas. We find that Andalucia godoyi has an even larger mtDNA gene complement than R. americana NZ. The extra genes are rpl35 (a large subunit mitoribosomal protein) and cox15 (involved in cytochrome oxidase assembly), which are nucleus encoded throughout other eukaryotes. Andalucia cox15 is strikingly similar to its homolog in the free-living α-proteobacterium Tistrella mobilis. Similarly, a long, highly conserved gene cluster in jakobid mtDNAs, which is a clear vestige of prokaryotic operons, displays a gene order more closely resembling that in free-living α-proteobacteria than in Rickettsiales species. Although jakobid mtDNAs, overall, are characterized by bacteria-like features, they also display a few remarkably divergent characters, such as 3'-tRNA editing in Seculamonas ecuadoriensis and genome linearization in Jakoba libera. Phylogenetic analysis with mtDNA-encoded proteins strongly supports monophyly of jakobids with Andalucia as the deepest divergence. However, it remains unclear which α-proteobacterial group is the closest mitochondrial relative.
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Affiliation(s)
- Gertraud Burger
- Department of Biochemistry, Robert-Cedergren Center in Bioinformatics and Genomics, Université de Montréal, Montreal, Quebec, Canada.
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26
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Jost D. Twist-DNA: computing base-pair and bubble opening probabilities in genomic superhelical DNA. ACTA ACUST UNITED AC 2013; 29:2479-81. [PMID: 23864732 DOI: 10.1093/bioinformatics/btt415] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
SUMMARY Local opening of the DNA double helix is required in many fundamental biological processes and is, in part, controlled by the degree of superhelicity imposed in vivo by the protein machinery. In particular, positions of superhelically destabilized regions correlate with regulatory sites along the genome. Based on a self-consistent linearization of a thermodynamic model of superhelical DNA introduced by Benham, we have developed a program that predicts the locations of these regions by efficiently computing base-pair and bubble opening probabilities in genomic DNA. The program allows visualization of results in standard genome browsers to compare DNA opening properties with other available datasets. AVAILABILITY AND IMPLEMENTATION Source codes freely available for download at http://www.cbp.ens-lyon.fr/doku.php?id=developpement:productions:logiciels:twistdna, implemented in Fortran90 and supported on any Unix-based operating system (Linux, Mac OS X).
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Affiliation(s)
- Daniel Jost
- Laboratoire de Physique, Ecole Normale Supérieure de Lyon, CNRS UMR 5672, 69007 Lyon, France
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27
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Preferential binding of hot spot mutant p53 proteins to supercoiled DNA in vitro and in cells. PLoS One 2013; 8:e59567. [PMID: 23555710 PMCID: PMC3608670 DOI: 10.1371/journal.pone.0059567] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 02/19/2013] [Indexed: 11/21/2022] Open
Abstract
Hot spot mutant p53 (mutp53) proteins exert oncogenic gain-of-function activities. Binding of mutp53 to DNA is assumed to be involved in mutp53-mediated repression or activation of several mutp53 target genes. To investigate the importance of DNA topology on mutp53-DNA recognition in vitro and in cells, we analyzed the interaction of seven hot spot mutp53 proteins with topologically different DNA substrates (supercoiled, linear and relaxed) containing and/or lacking mutp53 binding sites (mutp53BS) using a variety of electrophoresis and immunoprecipitation based techniques. All seven hot spot mutp53 proteins (R175H, G245S, R248W, R249S, R273C, R273H and R282W) were found to have retained the ability of wild-type p53 to preferentially bind circular DNA at native negative superhelix density, while linear or relaxed circular DNA was a poor substrate. The preference of mutp53 proteins for supercoiled DNA (supercoil-selective binding) was further substantiated by competition experiments with linear DNA or relaxed DNA in vitro and ex vivo. Using chromatin immunoprecipitation, the preferential binding of mutp53 to a sc mutp53BS was detected also in cells. Furthermore, we have shown by luciferase reporter assay that the DNA topology influences p53 regulation of BAX and MSP/MST1 promoters. Possible modes of mutp53 binding to topologically constrained DNA substrates and their biological consequences are discussed.
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28
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Mlc is a transcriptional activator with a key role in integrating cyclic AMP receptor protein and integration host factor regulation of leukotoxin RNA synthesis in Aggregatibacter actinomycetemcomitans. J Bacteriol 2013; 195:2284-97. [PMID: 23475968 DOI: 10.1128/jb.02144-12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aggregatibacter actinomycetemcomitans, a periodontal pathogen, synthesizes leukotoxin (LtxA), a protein that helps the bacterium evade the host immune response. Transcription of the ltxA operon is induced during anaerobic growth. The cyclic AMP (cAMP) receptor protein (CRP) indirectly increases ltxA expression, but the intermediary regulator is unknown. Integration host factor (IHF) binds to and represses the leukotoxin promoter, but neither CRP nor IHF is responsible for the anaerobic induction of ltxA RNA synthesis. Thus, we have undertaken studies to identify other regulators of leukotoxin transcription and to demonstrate how these proteins work together to modulate leukotoxin synthesis. First, analyses of ltxA RNA expression from defined leukotoxin promoter mutations in the chromosome identify positions -69 to -35 as the key control region and indicate that an activator protein modulates leukotoxin transcription. We show that Mlc, which is a repressor in Escherichia coli, functions as a direct transcriptional activator in A. actinomycetemcomitans; an mlc deletion mutant reduces leukotoxin RNA synthesis, and recombinant Mlc protein binds specifically at the -68 to -40 region of the leukotoxin promoter. Furthermore, we show that CRP activates ltxA expression indirectly by increasing the levels of Mlc. Analyses of Δmlc, Δihf, and Δihf Δmlc strains demonstrate that Mlc can increase RNA polymerase (RNAP) activity directly and that IHF represses ltxA RNA synthesis mainly by blocking Mlc binding. Finally, a Δihf Δmlc mutant still induces ltxA during anaerobic growth, indicating that there are additional factors involved in leukotoxin transcriptional regulation. A model for the coordinated regulation of leukotoxin transcription is presented.
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29
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Yadav MP, Padmanabhan S, Tripathi VP, Mishra RK, Dubey DD. Analysis of stress-induced duplex destabilization (SIDD) properties of replication origins, genes and intergenes in the fission yeast, Schizosaccharomyces pombe. BMC Res Notes 2012; 5:643. [PMID: 23163955 PMCID: PMC3533806 DOI: 10.1186/1756-0500-5-643] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 11/12/2012] [Indexed: 11/24/2022] Open
Abstract
Background Replication and transcription, the two key functions of DNA, require unwinding of the DNA double helix. It has been shown that replication origins in the budding yeast, Saccharomyces cerevisiae contain an easily unwound stretch of DNA. We have used a recently developed method for determining the locations and degrees of stress-induced duplex destabilization (SIDD) for all the reported replication origins in the genome of the fission yeast, Schizosaccharomyces pombe. Results We have found that the origins are more susceptible to SIDD as compared to the non-origin intergenic regions (NOIRs) and genes. SIDD analysis of many known origins in other eukaryotes suggests that SIDD is a common property of replication origins. Interestingly, the previously shown deletion-dependent changes in the activities of the origins of the ura4 origin region on chromosome 3 are paralleled by changes in SIDD properties, suggesting SIDD’s role in origin activity. SIDD profiling following in silico deletions of some origins suggests that many of the closely spaced S. pombe origins could be clusters of two or three weak origins, similar to the ura4 origin region. Conclusion SIDD appears to be a highly conserved, functionally important property of replication origins in S. pombe and other organisms. The distinctly low SIDD scores of origins and the long range effects of genetic alterations on SIDD properties provide a unique predictive potential to the SIDD analysis. This could be used in exploring different aspects of structural and functional organization of origins including interactions between closely spaced origins.
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Affiliation(s)
- Mukesh P Yadav
- Department of Biotechnology, Veer Bahadur Singh Purvanchal University, Jaunpur, Uttar Pradesh 222001, India
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30
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Vogt J, Mussotter T, Bengesser K, Claes K, Högel J, Chuzhanova N, Fu C, van den Ende J, Mautner VF, Cooper DN, Messiaen L, Kehrer-Sawatzki H. Identification of recurrent type-2 NF1 microdeletions reveals a mitotic nonallelic homologous recombination hotspot underlying a human genomic disorder. Hum Mutat 2012; 33:1599-609. [PMID: 22837079 DOI: 10.1002/humu.22171] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 07/11/2012] [Indexed: 01/08/2023]
Abstract
Nonallelic homologous recombination (NAHR) is one of the major mechanisms underlying copy number variation in the human genome. Although several disease-associated meiotic NAHR breakpoints have been analyzed in great detail, hotspots for mitotic NAHR are not well characterized. Type-2 NF1 microdeletions, which are predominantly of postzygotic origin, constitute a highly informative model with which to investigate the features of mitotic NAHR. Here, a custom-designed MLPA- and PCR-based approach was used to identify 23 novel NAHR-mediated type-2 NF1 deletions. Breakpoint analysis of these 23 type-2 deletions, together with 17 NAHR-mediated type-2 deletions identified previously, revealed that the breakpoints are nonuniformly distributed within the paralogous SUZ12 and SUZ12P sequences. Further, the analysis of this large group of type-2 deletions revealed breakpoint recurrence within short segments (ranging in size from 57 to 253-bp) as well as the existence of a novel NAHR hotspot of 1.9-kb (termed PRS4). This hotspot harbored 20% (8/40) of the type-2 deletion breakpoints and contains the 253-bp recurrent breakpoint region BR6 in which four independent type-2 deletion breakpoints were identified. Our findings indicate that a combination of an open chromatin conformation and short non-B DNA-forming repeats may predispose to recurrent mitotic NAHR events between SUZ12 and its pseudogene.
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Affiliation(s)
- Julia Vogt
- Institute of Human Genetics, University of Ulm, Ulm, Germany
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Donczew R, Weigel C, Lurz R, Zakrzewska-Czerwinska J, Zawilak-Pawlik A. Helicobacter pylori oriC--the first bipartite origin of chromosome replication in Gram-negative bacteria. Nucleic Acids Res 2012; 40:9647-60. [PMID: 22904070 PMCID: PMC3479198 DOI: 10.1093/nar/gks742] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Binding of the DnaA protein to oriC leads to DNA melting within the DNA unwinding element (DUE) and initiates replication of the bacterial chromosome. Helicobacter pylori oriC was previously identified as a region localized upstream of dnaA and containing a cluster of DnaA boxes bound by DnaA protein with a high affinity. However, no unwinding within the oriC sequence has been detected. Comprehensive in silico analysis presented in this work allowed us to identify an additional region (oriC2), separated from the original one (oriC1) by the dnaA gene. DnaA specifically binds both regions, but DnaA-dependent DNA unwinding occurs only within oriC2. Surprisingly, oriC2 is bound exclusively as supercoiled DNA, which directly shows the importance of the DNA topology in DnaA-oriC interactions, similarly as previously presented only for initiator-origin interactions in Archaea and some Eukaryota. We conclude that H. pylori oriC exhibits bipartite structure, being the first such origin discovered in a Gram-negative bacterium. The H. pylori mode of initiator-oriC interactions, with the loop formation between the subcomplexes of the discontinuous origin, resembles those discovered in Bacillus subtilis chromosome and in many plasmids, which might suggest a similar way of controlling initiation of replication.
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Affiliation(s)
- Rafał Donczew
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Department of Microbiology, Weigla 12, 53-114 Wrocław, Poland
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Acosta-Cruz E, Wisniewski-Dyé F, Rouy Z, Barbe V, Valdés M, Mavingui P. Insights into the 1.59-Mbp largest plasmid of Azospirillum brasilense CBG497. Arch Microbiol 2012; 194:725-36. [PMID: 22481309 DOI: 10.1007/s00203-012-0805-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/31/2012] [Accepted: 03/07/2012] [Indexed: 11/25/2022]
Abstract
The plant growth-promoting proteobacterium Azospirillum brasilense enhances growth of many economically important crops, such as wheat, maize, and rice. The sequencing and annotation of the 1.59-Mbp replicon of A. brasilense CBG497, a strain isolated from a maize rhizosphere grown on an alkaline soil in the northeast of Mexico, revealed a GC content of 68.7 % and the presence of 1,430 potential protein-encoding genes, 1,147 of them classified into clusters of orthologous groups categories, and 16 tRNA genes representing 11 tRNA species. The presence of sixty-two genes representatives of the minimal gene set and chromid core genes suggests its importance in bacterial survival. The phaAB → G operon, reported as involved in the bacterial adaptation to alkaline pH in the presence of K(+), was also found on this replicon and detected in several Azospirillum strains. Phylogenetic analysis suggests that it was laterally acquired. We were not able to show its inference on the adaptation to basic pH, giving a hint about the presence of an alternative system for adaptation to alkaline pH.
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Affiliation(s)
- Erika Acosta-Cruz
- Laboratorio de Microbiología Agrícola, Escuela Nacional de Ciencias Biológicas, IPN, México DF, Mexico
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A fundamental regulatory mechanism operating through OmpR and DNA topology controls expression of Salmonella pathogenicity islands SPI-1 and SPI-2. PLoS Genet 2012; 8:e1002615. [PMID: 22457642 PMCID: PMC3310775 DOI: 10.1371/journal.pgen.1002615] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 02/07/2012] [Indexed: 01/28/2023] Open
Abstract
DNA topology has fundamental control over the ability of transcription factors to access their target DNA sites at gene promoters. However, the influence of DNA topology on protein–DNA and protein–protein interactions is poorly understood. For example, relaxation of DNA supercoiling strongly induces the well-studied pathogenicity gene ssrA (also called spiR) in Salmonella enterica, but neither the mechanism nor the proteins involved are known. We have found that relaxation of DNA supercoiling induces expression of the Salmonella pathogenicity island (SPI)-2 regulator ssrA as well as the SPI-1 regulator hilC through a mechanism that requires the two-component regulator OmpR-EnvZ. Additionally, the ompR promoter is autoregulated in the same fashion. Conversely, the SPI-1 regulator hilD is induced by DNA relaxation but is repressed by OmpR. Relaxation of DNA supercoiling caused an increase in OmpR binding to DNA and a concomitant decrease in binding by the nucleoid-associated protein FIS. The reciprocal occupancy of DNA by OmpR and FIS was not due to antagonism between these transcription factors, but was instead a more intrinsic response to altered DNA topology. Surprisingly, DNA relaxation had no detectable effect on the binding of the global repressor H-NS. These results reveal the underlying molecular mechanism that primes SPI genes for rapid induction at the onset of host invasion. Additionally, our results reveal novel features of the archetypal two-component regulator OmpR. OmpR binding to relaxed DNA appears to generate a locally supercoiled state, which may assist promoter activation by relocating supercoiling stress-induced destabilization of DNA strands. Much has been made of the mechanisms that have evolved to regulate horizontally-acquired genes such as SPIs, but parallels among the ssrA, hilC, and ompR promoters illustrate that a fundamental form of regulation based on DNA topology coordinates the expression of these genes regardless of their origins. DNA is often considered to be a passive carrier of genetic information, but in fact DNA is an active participant in coordinating the expression of the genes it carries. This is because DNA is a dynamic molecule that can assume a wide range of topologies, and this has a direct impact on the formation of the protein–DNA complexes that drive gene expression. In a bacterium, the chromosome is supercoiled to variable levels according to environmental conditions, and supercoiling in turn governs the topology of gene promoters. Thus DNA supercoiling is able to transduce environmental signals to regulate promoter output. A previous study found that the intestinal pathogen Salmonella enterica may use changes in DNA supercoiling to detect when it has entered host immune cells, allowing the bacterium to induce the pathogenicity genes it requires to evade killing by macrophage. In dissecting the underlying molecular mechanisms, we have found that changes in DNA supercoiling also upregulate other key pathogenicity genes, and we have identified the proteins involved in this gene regulatory process. These findings indicate that a fundamental level of gene control arising from the interplay between protein transcription factors and DNA topology regulates Salmonella pathogenicity.
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Identification of a new gene required for the biosynthesis of rhodoquinone in Rhodospirillum rubrum. J Bacteriol 2011; 194:965-71. [PMID: 22194448 DOI: 10.1128/jb.06319-11] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rhodoquinone (RQ) is a required cofactor for anaerobic respiration in Rhodospirillum rubrum, and it is also found in several helminth parasites that utilize a fumarate reductase pathway. RQ is an aminoquinone that is structurally similar to ubiquinone (Q), a polyprenylated benzoquinone used in the aerobic respiratory chain. RQ is not found in humans or other mammals, and therefore, the inhibition of its biosynthesis may provide a novel antiparasitic drug target. To identify a gene specifically required for RQ biosynthesis, we determined the complete genome sequence of a mutant strain of R. rubrum (F11), which cannot grow anaerobically and does not synthesize RQ, and compared it with that of a spontaneous revertant (RF111). RF111 can grow anaerobically and has recovered the ability to synthesize RQ. The two strains differ by a single base pair, which causes a nonsense mutation in the putative methyltransferase gene rquA. To test whether this mutation is important for the F11 phenotype, the wild-type rquA gene was cloned into the pRK404E1 vector and conjugated into F11. Complementation of the anaerobic growth defect in F11 was observed, and liquid chromatography-time of flight mass spectrometry (LC-TOF-MS) analysis of lipid extracts confirmed that plasmid-complemented F11 was able to synthesize RQ. To further validate the requirement of rquA for RQ biosynthesis, we generated a deletion mutant from wild-type R. rubrum by the targeted replacement of rquA with a gentamicin resistance cassette. The ΔrquA mutant exhibited the same phenotype as that of F11. These results are significant because rquA is the first gene to be discovered that is required for RQ biosynthesis.
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Schneider B, Nagel S, Ehrentraut S, Kaufmann M, Meyer C, Geffers R, Drexler HG, MacLeod RAF. Neoplastic MiR-17∼92 deregulation at a dna fragility motif (SIDD). Genes Chromosomes Cancer 2011; 51:219-28. [DOI: 10.1002/gcc.20946] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 09/29/2011] [Accepted: 09/30/2011] [Indexed: 12/19/2022] Open
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Jost D, Zubair A, Everaers R. Bubble statistics and positioning in superhelically stressed DNA. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:031912. [PMID: 22060408 DOI: 10.1103/physreve.84.031912] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 08/02/2011] [Indexed: 05/31/2023]
Abstract
We present a general framework to study the thermodynamic denaturation of double-stranded DNA under superhelical stress. We report calculations of position- and size-dependent opening probabilities for bubbles along the sequence. Our results are obtained from transfer-matrix solutions of the Zimm-Bragg model for unconstrained DNA and of a self-consistent linearization of the Benham model for superhelical DNA. The numerical efficiency of our method allows for the analysis of entire genomes and of random sequences of corresponding length (10(6)-10(9) base pairs). We show that, at physiological conditions, opening in superhelical DNA is strongly cooperative with average bubble sizes of 10(2)-10(3) base pairs (bp), and orders of magnitude higher than in unconstrained DNA. In heterogeneous sequences, the mean degree of base-pair opening is self-averaging, while bubble localization and statistics are dominated by sequence disorder. Compared to random sequences with identical GC-content, genomic DNA has a significantly increased probability to open large bubbles under superhelical stress. These bubbles are frequently located directly upstream of transcription start sites.
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Affiliation(s)
- Daniel Jost
- Laboratoire de Physique and Centre Blaise Pascal of the École Normale Supérieure de Lyon, Université de Lyon, CNRS UMR 5672, Lyon, France
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Sershen CL, Mell JC, Madden SM, Benham CJ. Superhelical duplex destabilization and the recombination position effect. PLoS One 2011; 6:e20798. [PMID: 21695263 PMCID: PMC3111454 DOI: 10.1371/journal.pone.0020798] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Accepted: 05/12/2011] [Indexed: 11/19/2022] Open
Abstract
The susceptibility to recombination of a plasmid inserted into a chromosome varies with its genomic position. This recombination position effect is known to correlate with the average G+C content of the flanking sequences. Here we propose that this effect could be mediated by changes in the susceptibility to superhelical duplex destabilization that would occur. We use standard nonparametric statistical tests, regression analysis and principal component analysis to identify statistically significant differences in the destabilization profiles calculated for the plasmid in different contexts, and correlate the results with their measured recombination rates. We show that the flanking sequences significantly affect the free energy of denaturation at specific sites interior to the plasmid. These changes correlate well with experimentally measured variations of the recombination rates within the plasmid. This correlation of recombination rate with superhelical destabilization properties of the inserted plasmid DNA is stronger than that with average G+C content of the flanking sequences. This model suggests a possible mechanism by which flanking sequence base composition, which is not itself a context-dependent attribute, can affect recombination rates at positions within the plasmid.
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Affiliation(s)
- Cheryl L Sershen
- Baylor College of Medicine, Houston, Texas, United States of America.
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Kantorovitz MR, Rapti Z, Gelev V, Usheva A. Computing DNA duplex instability profiles efficiently with a two-state model: trends of promoters and binding sites. BMC Bioinformatics 2010; 11:604. [PMID: 21172036 PMCID: PMC3018474 DOI: 10.1186/1471-2105-11-604] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Accepted: 12/21/2010] [Indexed: 11/30/2022] Open
Abstract
Background DNA instability profiles have been used recently for predicting the transcriptional start site and the location of core promoters, and to gain insight into promoter action. It was also shown that the use of these profiles can significantly improve the performance of motif finding programs. Results In this work we introduce a new method for computing DNA instability profiles. The model that we use is a modified Ising-type model and it is implemented via statistical mechanics. Our linear time algorithm computes the profile of a 10,000 base-pair long sequence in less than one second. The method we use also allows the computation of the probability that several consecutive bases are unpaired simultaneously. This is a feature that is not available in other linear-time algorithms. We use the model to compare the thermodynamic trends of promoter sequences of several genomes. In addition, we report results that associate the location of local extrema in the instability profiles with the presence of core promoter elements at these locations and with the location of the transcription start sites (TSS). We also analyzed the instability scores of binding sites of several human core promoter elements. We show that the instability scores of functional binding sites of a given core promoter element are significantly different than the scores of sites with the same motif occurring outside the functional range (relative to the TSS). Conclusions The time efficiency of the algorithm and its genome-wide applications makes this work of broad interest to scientists interested in transcriptional regulation, motif discovery, and comparative genomics.
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Affiliation(s)
- Miriam R Kantorovitz
- Department of Mathematics, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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Broll S, Oumard A, Hahn K, Schambach A, Bode J. Minicircle performance depending on S/MAR-nuclear matrix interactions. J Mol Biol 2009; 395:950-65. [PMID: 20004666 DOI: 10.1016/j.jmb.2009.11.066] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 11/14/2009] [Accepted: 11/30/2009] [Indexed: 12/12/2022]
Abstract
The ideal vector for cell and tissue modification does not depend on integration but rather behaves as an independent functional unit that replicates as an episome. Based on a scaffold/matrix attachment region (S/MAR), we have introduced, in 2006, an approximately 4-kb replicating nonviral minicircle able to exploit the cellular replication machinery in a way reminiscent of ARS vectors. Consisting of only one active transcription unit and the S/MAR, it resists silencing as it is free of prokaryotic vector parts and drug selection markers. The rate of final establishment in the nuclear architecture is moderate but comparable to Epstein-Barr virus-based episomes (<5%). Here, we demonstrate that this parameter can be improved if the host cell chromatin is opened by histone hyperacetylation prior to transfection. It remains unaffected, however, by cell cycle position. Still, this class of episomes revealed intrinsic instability and integration after 5 months of continuous culture. In vivo evolution enabled the effective reduction of S/MAR size from 2 kb to 733 bp (resulting in a minicircle of approximately 3 kb) with largely improved stability and cloning capacity. Investigation of individual clones served to prove persistent and homogenous expression, which is ascribed to stable association with nuclear attachment sites. Optimum expression levels were shown to depend on the authentic usage of a polyadenylation site 3' from the S/MAR as anticipated by the stress-induced duplex destabilization algorithm, which finds increasing use to predict the functional parameters of these systems.
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Affiliation(s)
- Sandra Broll
- Department Molecular Biotechnology/Epigenetic Regulation, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
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Adding to Yersinia enterocolitica gene pool diversity: two cryptic plasmids from a biotype 1A isolate. J Biomed Biotechnol 2009; 2009:398434. [PMID: 19834620 PMCID: PMC2760160 DOI: 10.1155/2009/398434] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 06/21/2009] [Accepted: 07/13/2009] [Indexed: 01/15/2023] Open
Abstract
We report the nucleotide sequence of two novel cryptic plasmids (4357 and 14 662 base pairs) carried by a Yersinia enterocolitica biotype 1A strain isolated from pork. As distinguished from most biotype 1A strains, this isolate, designated 07-04449, exhibited adherence to eukaryotic cells. The smaller plasmid pYe4449-1 carries five attributable open reading frames (ORFs) encoding the first CcdA/CcdB-like antitoxin/toxin system described for a Yersinia plasmid, a RepA-like replication initiation protein, and mobilizing factors MobA and MobC. The deduced amino acid sequences showed highest similarity to proteins described in Salmonella (CcdA/B), Klebsiella (RepA), and Plesiomonas (MobA/C) indicating genomic fluidity among members of the Enterobacteriaceae. One additional ORF with unknown function, termed ORF5, was identified with an ancestry distinct from the rest of the plasmid. While the C+G content of ORF5 is 38.3%, the rest of pYe4449-1 shows a C+G content of 55.7%. The C+G content of the larger plasmid pYe4449-2 (54.9%) was similar to that of pYe4449-1 (53.7%) and differed from that of the Y. enterocolitica genome (47.3%). Of the 14 ORFs identified on pYe4449-2, only six ORFs showed significant similarity to database entries. For three of these ORFs likely functions could be ascribed: a TnpR-like resolvase and a phage replication protein, localized each on a low C+G island, and DNA primase TraC. Two ORFs of pYe4449-2, ORF3 and ORF7, seem to encode secretable proteins. Epitope-tagging of ORF3 revealed protein expression at 4 degrees C but not at or above 27 degrees C suggesting adaptation to a habitat outside swine. The hypothetical protein encoded by ORF7 is the member of a novel repeat protein family sharing the DxxGN(x)(n)DxxGN motif. Our findings illustrate the exceptional gene pool diversity within the species Y. enterocolitica driven by horizontal gene transfer events.
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An interactive regulatory network controls stress response in Bifidobacterium breve UCC2003. J Bacteriol 2009; 191:7039-49. [PMID: 19734308 DOI: 10.1128/jb.00897-09] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Members of the genus Bifidobacterium are gram-positive bacteria that commonly are found in the gastrointestinal tract (GIT) of mammals, including humans. Because of their perceived probiotic properties, they frequently are incorporated as functional ingredients in food products. From probiotic production to storage and GIT delivery, bifidobacteria encounter a plethora of stresses. To cope with these environmental challenges, they need to protect themselves through stress-induced adaptive responses. We have determined the response of B. breve UCC2003 to various stresses (heat, osmotic, and solvent) using transcriptome analysis, DNA-protein interactions, and GusA reporter fusions, and we combined these with results from an in silico analysis. The integration of these results allowed the formulation of a model for an interacting regulatory network for stress response in B. breve UCC2003 where HspR controls the SOS response and the ClgR regulon, which in turn regulates and is regulated by HrcA. This model of an interacting regulatory network is believed to represent the paradigm for stress adaptation in bifidobacteria.
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Mallios RR, Ojcius DM, Ardell DH. An iterative strategy combining biophysical criteria and duration hidden Markov models for structural predictions of Chlamydia trachomatis sigma66 promoters. BMC Bioinformatics 2009; 10:271. [PMID: 19715597 PMCID: PMC2743672 DOI: 10.1186/1471-2105-10-271] [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] [Received: 02/11/2009] [Accepted: 08/28/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Promoter identification is a first step in the quest to explain gene regulation in bacteria. It has been demonstrated that the initiation of bacterial transcription depends upon the stability and topology of DNA in the promoter region as well as the binding affinity between the RNA polymerase sigma-factor and promoter. However, promoter prediction algorithms to date have not explicitly used an ensemble of these factors as predictors. In addition, most promoter models have been trained on data from Escherichia coli. Although it has been shown that transcriptional mechanisms are similar among various bacteria, it is quite possible that the differences between Escherichia coli and Chlamydia trachomatis are large enough to recommend an organism-specific modeling effort. RESULTS Here we present an iterative stochastic model building procedure that combines such biophysical metrics as DNA stability, curvature, twist and stress-induced DNA duplex destabilization along with duration hidden Markov model parameters to model Chlamydia trachomatis sigma66 promoters from 29 experimentally verified sequences. Initially, iterative duration hidden Markov modeling of the training set sequences provides a scoring algorithm for Chlamydia trachomatis RNA polymerase sigma66/DNA binding. Subsequently, an iterative application of Stepwise Binary Logistic Regression selects multiple promoter predictors and deletes/replaces training set sequences to determine an optimal training set. The resulting model predicts the final training set with a high degree of accuracy and provides insights into the structure of the promoter region. Model based genome-wide predictions are provided so that optimal promoter candidates can be experimentally evaluated, and refined models developed. Co-predictions with three other algorithms are also supplied to enhance reliability. CONCLUSION This strategy and resulting model support the conjecture that DNA biophysical properties, along with RNA polymerase sigma-factor/DNA binding collaboratively, contribute to a sequence's ability to promote transcription. This work provides a baseline model that can evolve as new Chlamydia trachomatis sigma66 promoters are identified with assistance from the provided genome-wide predictions. The proposed methodology is ideal for organisms with few identified promoters and relatively small genomes.
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Affiliation(s)
- Ronna R Mallios
- School of Natural Sciences, University of California, Merced, CA 95344, USA.
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EGG MARGIT, HÖCKNER MARTINA, BRANDSTÄTTER ANITA, SCHULER DIETMAR, DALLINGER REINHARD. Structural and bioinformatic analysis of the Roman snail Cd-Metallothionein gene uncovers molecular adaptation towards plasticity in coping with multifarious environmental stress. Mol Ecol 2009; 18:2426-43. [DOI: 10.1111/j.1365-294x.2009.04191.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Cruickshank MN, Fenwick E, Karimi M, Abraham LJ, Ulgiati D. Cell- and stage-specific chromatin structure across the Complement receptor 2 (CR2/CD21) promoter coincide with CBF1 and C/EBP-beta binding in B cells. Mol Immunol 2009; 46:2613-22. [PMID: 19487031 DOI: 10.1016/j.molimm.2009.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Revised: 05/01/2009] [Accepted: 05/02/2009] [Indexed: 01/19/2023]
Abstract
Stringent developmental transcription requires multiple transcription factor (TF) binding sites, cell-specific expression of signaling molecules, TFs and co-regulators and appropriate chromatin structure. During B-lymphopoiesis, human Complement receptor 2 (CR2/CD21) is detected on immature and mature B cells but not on B cell precursors and plasma cells. We examined cell- and stage-specific human CR2 gene regulation using cell lines modeling B-lymphopoiesis. Chromatin accessibility assays revealed a region between -409 and -262 with enhanced accessibility in mature B cells and pre-B cells, compared to either non-lymphoid or plasma cell-types, however, accessibility near the transcription start site (TSS) was elevated only in CR2-expressing B cells. A correlation between histone acetylation and CR2 expression was observed, while histone H3K4 dimethylation was enriched near the TSS in both CR2-expressing B cells and non-expressing pre-B cells. Candidate sites within the CR2 promoter were identified which could regulate chromatin, including a matrix attachment region associated with CDP, SATB1/BRIGHT and CEBP-beta sites as well as two CBF1 sites. ChIP assays verified that both CBF1 and C/EBP-beta bind the CR2 promoter in B cells raising the possibility that these factors facilitate or respond to alterations in chromatin structure to control the timing and/or level of CR2 transcription.
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Douillard FP, Ryan KA, Hinds J, O'Toole PW. Effect of FliK mutation on the transcriptional activity of the {sigma}54 sigma factor RpoN in Helicobacter pylori. MICROBIOLOGY-SGM 2009; 155:1901-1911. [PMID: 19383688 DOI: 10.1099/mic.0.026062-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Helicobacter pylori is a motile Gram-negative bacterium that colonizes and persists in the human gastric mucosa. The flagellum gene regulatory circuitry of H. pylori is unique in many aspects compared with the Salmonella/Escherichia coli paradigms, and some regulatory checkpoints remain unclear. FliK controls the hook length during flagellar assembly. Microarray analysis of a fliK-null mutant revealed increased transcription of genes under the control of the sigma(54) sigma factor RpoN. This sigma factor has been shown to be responsible for transcription of the class II flagellar genes, including flgE and flaB. No genes higher in the flagellar hierarchy had altered expression, suggesting specific and localized FliK-dependent feedback on the RpoN regulon. FliK thus appears to be involved in three processes: hook-length control, export substrate specificity and control of RpoN transcriptional activity.
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Affiliation(s)
- Francois P Douillard
- Department of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Western Road, Cork, Ireland
| | - Kieran A Ryan
- Department of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Western Road, Cork, Ireland
| | - Jason Hinds
- Bacterial Microarray Group, Division of Cellular and Molecular Medicine, St George's University of London, Cranmer Terrace, London SW17 0RE, UK
| | - Paul W O'Toole
- Department of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Western Road, Cork, Ireland
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Giannakopoulos A, Stavrou EF, Zarkadis I, Zoumbos N, Thrasher AJ, Athanassiadou A. The functional role of S/MARs in episomal vectors as defined by the stress-induced destabilization profile of the vector sequences. J Mol Biol 2009; 387:1239-49. [PMID: 19248788 DOI: 10.1016/j.jmb.2009.02.043] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 02/06/2009] [Accepted: 02/12/2009] [Indexed: 11/28/2022]
Abstract
The scaffold/matrix attachment regions (S/MARs) are chromosomal elements that participate in the formation of chromatin domains and have origin of replication support functions. Because of all these functions, in recent years, they have been used as part of episomal vectors for gene transfer. The S/MAR of the human beta-interferon gene has been shown to support efficient episome retention and transgene expression in various mammalian cells. In Jurkat and other cells, DNA plasmid vectors containing Epstein-Barr virus origin of replication (EBV OriP) and the EBV nuclear antigen-1 gene mediate prolonged episome retention in the host cell nucleus, which, however, diminishes over time. In order to enhance retention, we combined this system with an S/MAR element. Unexpectedly, this completely eliminated the capacity of episomes to replicate. Calculation of the stress-induced DNA duplex destabilization profile of the vectors suggested that the S/MAR element had created an increase in molecular stability at the OriP site that may have disturbed replicative potential. In contrast, introduction of an alternative initiation of replication region from the beta-globin gene locus, instead of EBV OriP and the EBV nuclear antigen-1 gene, restored replicative capacity and enhanced episome retention mediated by the S/MAR. These effects were associated with a destabilization profile at the initiation of replication region. These data demonstrate a correlation between S/MAR-mediated vector retention and the presence of an unstable duplex at a replication origin, in this particular setting. We consider that the calculation of stress-induced duplex destabilization may be an informative first step in the design of units that replicate extrachromosomally, particularly as the latter present a safer and, therefore, attractive alternative to integrating viral vectors for gene therapy applications.
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Williams JA, Carnes AE, Hodgson CP. Plasmid DNA vaccine vector design: impact on efficacy, safety and upstream production. Biotechnol Adv 2009; 27:353-70. [PMID: 19233255 DOI: 10.1016/j.biotechadv.2009.02.003] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 02/02/2009] [Accepted: 02/07/2009] [Indexed: 10/21/2022]
Abstract
Critical molecular and cellular biological factors impacting design of licensable DNA vaccine vectors that combine high yield and integrity during bacterial production with increased expression in mammalian cells are reviewed. Food and Drug Administration (FDA), World Health Organization (WHO) and European Medical Agencies (EMEA) regulatory guidance's are discussed, as they relate to vector design and plasmid fermentation. While all new vectors will require extensive preclinical testing to validate safety and performance prior to clinical use, regulatory testing burden for follow-on products can be reduced by combining carefully designed synthetic genes with existing validated vector backbones. A flowchart for creation of new synthetic genes, combining rationale design with bioinformatics, is presented. The biology of plasmid replication is reviewed, and process engineering strategies that reduce metabolic burden discussed. Utilizing recently developed low metabolic burden seed stock and fermentation strategies, optimized vectors can now be manufactured in high yields exceeding 2 g/L, with specific plasmid yields of 5% total dry cell weight.
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Hierarchical mechanisms build the DNA-binding specificity of FUSE binding protein. Proc Natl Acad Sci U S A 2008; 105:18296-301. [PMID: 19015535 DOI: 10.1073/pnas.0803279105] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The far upstream element (FUSE) binding protein (FBP), a single-stranded nucleic acid binding protein, is recruited to the c-myc promoter after melting of FUSE by transcriptionally generated dynamic supercoils. Via interactions with TFIIH and FBP-interacting repressor (FIR), FBP modulates c-myc transcription. Here, we investigate the contributions of FBP's 4 K Homology (KH) domains to sequence selectivity. EMSA and missing contact point analysis revealed that FBP contacts 4 separate patches spanning a large segment of FUSE. A SELEX procedure using paired KH-domains defined the preferred subsequences for each KH domain. Unexpectedly, there was also a strong selection for the noncontacted residues between these subsequences, showing that the contact points must be optimally presented in a backbone that minimizes secondary structure. Strategic mutation of contact points defined in this study disabled FUSE activity in vivo. Because the biological specificity of FBP is tuned at several layers: (i) accessibility of the site; (ii) supercoil-driven melting; (iii) presentation of unhindered bases for recognition; and (iv) modular interaction of KH-domains with cognate bases, the FBP-FIR system and sequence-specific, single-strand DNA binding proteins in general are likely to prove versatile tools for adjusting gene expression.
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Wang H, Benham CJ. Superhelical destabilization in regulatory regions of stress response genes. PLoS Comput Biol 2008; 4:e17. [PMID: 18208321 PMCID: PMC2211533 DOI: 10.1371/journal.pcbi.0040017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Accepted: 12/03/2007] [Indexed: 11/18/2022] Open
Abstract
Stress-induced DNA duplex destabilization (SIDD) analysis exploits the known structural and energetic properties of DNA to predict sites that are susceptible to strand separation under negative superhelical stress. When this approach was used to calculate the SIDD profile of the entire Escherichia coli K12 genome, it was found that strongly destabilized sites occur preferentially in intergenic regions that are either known or inferred to contain promoters, but rarely occur in coding regions. Here, we investigate whether the genes grouped in different functional categories have characteristic SIDD properties in their upstream flanks. We report that strong SIDD sites in the E. coli K12 genome are statistically significantly overrepresented in the upstream regions of genes encoding transcriptional regulators. In particular, the upstream regions of genes that directly respond to physiological and environmental stimuli are more destabilized than are those regions of genes that are not involved in these responses. Moreover, if a pathway is controlled by a transcriptional regulator whose gene has a destabilized 5′ flank, then the genes (operons) in that pathway also usually contain strongly destabilized SIDD sites in their 5′ flanks. We observe this statistically significant association of SIDD sites with upstream regions of genes functioning in transcription in 38 of 43 genomes of free-living bacteria, but in only four of 18 genomes of endosymbionts or obligate parasitic bacteria. These results suggest that strong SIDD sites 5′ to participating genes may be involved in transcriptional responses to environmental changes, which are known to transiently alter superhelicity. We propose that these SIDD sites are active and necessary participants in superhelically mediated regulatory mechanisms governing changes in the global pattern of gene expression in prokaryotes in response to physiological or environmental changes. DNA in vivo experiences regulated amounts of untwisting stress. If sufficiently large, these stresses can destabilize the double helix at specific locations. These sites then become favored locations for strand separations. Gene expression and DNA replication, the two major jobs of DNA, both require the strands of the duplex to be separated. Thus, events that affect the ease of strand separation can regulate the initiation of these processes. Stress-induced DNA duplex destabilization (SIDD) has been implicated in mechanisms regulating several biological processes, including the initiation of gene expression and replication. We have developed computational methods that accurately predict the locations and extents of destabilization within genomic DNA sequences that occur in response to specified stress levels. Here, we report that the easily destabilized sites we find in the Escherichia coli K12 genome are statistically significantly overrepresented in the upstream regions of genes encoding proteins that regulate transcription. In particular, the regions upstream of genes that directly respond to physiological and environmental stimuli are more destabilized than are those regions of genes that are not involved in these responses. These results suggest that strong SIDD sites upstream of participating genes may be involved in transcriptional responses to environmental changes.
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Affiliation(s)
- Huiquan Wang
- UC Davis Genome Center, University of California Davis, Davis, California, United States of America
| | - Craig J Benham
- UC Davis Genome Center, University of California Davis, Davis, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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The functional response of upstream DNA to dynamic supercoiling in vivo. Nat Struct Mol Biol 2008; 15:146-54. [PMID: 18193062 DOI: 10.1038/nsmb.1372] [Citation(s) in RCA: 226] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Accepted: 11/09/2007] [Indexed: 11/08/2022]
Abstract
Because RNA polymerase is a powerful motor, transmission of transcription-generated forces might directly alter DNA structure, chromatin or gene activity in mammalian cells. Here we show that transcription-generated supercoils streaming dynamically from active promoters have considerable consequences for DNA structure and function in cells. Using a tamoxifen-activatable Cre recombinase to excise a test segment of chromatin positioned between divergently transcribed metallothionein-IIa promoters, we found the degree of dynamic supercoiling to increase as transcription intensified, and it was very sensitive to the specific arrangement of promoters and cis elements. Using psoralen as an in vivo probe confirmed that, during transcription, sufficient supercoiling is produced to enable transitions to conformations other than B-DNA in elements such as the human MYC far upstream element (FUSE), which in turn recruit structure-sensitive regulatory proteins, such as FUSE Binding Protein (FBP) and FBP-Interacting Repressor (FIR). These results indicate that mechanical stresses, constrained by architectural features of DNA and chromatin, may broadly contribute to gene regulation.
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