1
|
Wang W, An X, Yan K, Li Q. Construction and Application of Orthogonal T7 Expression System in Eukaryote: An Overview. Adv Biol (Weinh) 2023; 7:e2200218. [PMID: 36464626 DOI: 10.1002/adbi.202200218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 10/17/2022] [Indexed: 12/12/2022]
Abstract
The T7 system is an orthogonal transcription-system, which is characterized by simplicity, higher efficiency, and higher processivity, and it is used for protein or mRNA synthesis in various biological-systems. In comparison with prokaryotes, the construction of the T7 expression system is still on-going in eukaryotes, but it shows greatly applicable prospects. In the present paper, development of T7 expression system construction in eukaryotes is reviewed, including its construction in animal (mammalian cells, trypanosomatid protozoa, Xenopus oocytes, zebrafish), plant, and microorganism and its application in vaccine production and gene therapy. In addition, the innate challenges of T7 expression system construction in eukaryote and its potential application in vaccine production and gene therapy are discussed.
Collapse
Affiliation(s)
- Wenya Wang
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Xiaoyan An
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Kun Yan
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Qiang Li
- Key Laboratory for Industrial Biocatalysis, Ministry of Education, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, P. R. China
| |
Collapse
|
2
|
Abstract
![]()
Optogenetic tools are widely used to control gene expression
dynamics
both in prokaryotic and eukaryotic cells. These tools are used in
a variety of biological applications from stem cell differentiation
to metabolic engineering. Despite some tools already available in
bacteria, no light-inducible system currently exists to control gene
expression independently from mammalian transcriptional and/or translational
machineries thus working orthogonally to endogenous regulatory mechanisms.
Such a tool would be particularly important in synthetic biology,
where orthogonality is advantageous to achieve robust activation of
synthetic networks. Here we implement, characterize, and optimize
a new optogenetic tool in mammalian cells based on a previously published
system in bacteria called Opto-T7RNAPs. The tool is orthogonal to
the cellular machinery for transcription and consists of a split T7
RNA polymerase coupled with the blue light-inducible magnets system
(mammalian OptoT7–mOptoT7). In our study we exploited the T7
polymerase’s viral origins to tune our system’s expression
level, reaching up to an almost 20-fold change activation over the
dark control. mOptoT7 is used here to generate mRNA for protein expression,
shRNA for protein inhibition, and Pepper aptamer for RNA visualization.
Moreover, we show that mOptoT7 can mitigate the gene expression burden
when compared to another optogenetic construct. These properties make
mOptoT7 a powerful new tool to use when orthogonality and viral RNA
species (that lack endogenous RNA modifications) are desired.
Collapse
Affiliation(s)
- Sara Dionisi
- Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Karol Piera
- Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Armin Baumschlager
- Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Mustafa Khammash
- Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| |
Collapse
|
3
|
Nacken W, Schreiber A, Masemann D, Ludwig S. The Effector Domain of the Influenza A Virus Nonstructural Protein NS1 Triggers Host Shutoff by Mediating Inhibition and Global Deregulation of Host Transcription When Associated with Specific Structures in the Nucleus. mBio 2021; 12:e0219621. [PMID: 34488451 DOI: 10.1128/mBio.02196-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Host shutoff in influenza A virus (IAV) infection is a key process contributing to viral takeover of the cellular machinery and resulting in the downregulation of host gene expression. Analysis of nascently transcribed RNA in a cellular model that allows the functional induction of NS1 demonstrates that NS1 suppresses host transcription. NS1 inhibits the expression of genes driven by RNA polymerase II as well as RNA polymerase I-driven promoters, but not by the noneukaryotic T7 polymerase. Additionally, transcriptional termination is deregulated in cells infected with wild-type IAV. The NS1 effector domain alone is able to mediate both effects, whereas NS1 mutant GLEWN184-188RFKRY (184-188) is not. Overexpression of CPSF30 counteracts NS1-mediated inhibition of RNA polymerase II-driven reporter gene expression, but knockdown of CPSF30 expression does not attenuate gene expression. Although NS1 is associated with nuclear chromatin, superresolution microscopy demonstrates that NS1 does not colocalize with genomic DNA. Moreover, NS1 mutants and NS1 fusion proteins, unable to associate with nuclear chromatin and displaying an altered subcellular distribution are still able to attenuate reporter gene expression. However, tethering NS1 artificially to the cytoskeleton results in the loss of reporter gene inhibition. A NS1 deficient in both native nuclear localization signals (NLS) is able to inhibit gene expression as effective as wild-type NS1 when a synthetic NLS relocates it to specific structures of the nucleus. Colocalization experiments and reporter gene cotransfection experiments with a NS1 fusion guiding it to nuclear speckles suggest that the presence of NS1 in nuclear speckles seems to be essential for host shutoff.
Collapse
|
4
|
Ghassemi F, Madadgar O, Roohvand F, Rasekhian M, Etemadzadeh MH, Boroujeni GRN, Langroudi AG, Azadmanesh K. Translational efficiency of BVDV IRES and EMCV IRES for T7 RNA polymerase driven cytoplasmic expression in mammalian cell lines. Mol Biol 2017. [DOI: 10.1134/s002689331702011x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
|
5
|
Biswas A, Treadaway J, Tellinghuisen TL. Interaction between Nonstructural Proteins NS4B and NS5A Is Essential for Proper NS5A Localization and Hepatitis C Virus RNA Replication. J Virol 2016; 90:7205-18. [PMID: 27252526 DOI: 10.1128/JVI.00037-16] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 05/23/2016] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED The hepatitis C virus NS5A protein is tethered to cellular membranes via an amphipathic amino-terminal helix that is inserted in-plane into the outer endoplasmic reticulum (ER)-derived membrane leaflet. The charged face of the helix faces the cytoplasm and may contribute to interactions involved in replicase assembly and function. Using an aggressive charge flip mutagenesis strategy, we identified a number of essential residues for replication on the charged face of the NS5A anchor and identified a double charge face mutant that is lethal for RNA replication but generates suppressor mutations in the carboxy-terminal helix of the NS4B protein. This suppressor restores RNA replication of the NS5A helix double flip mutant (D1979K/D1982K) and, interestingly, seems to function by restoring the proper localization of NS5A to the viral replicase. These data add to our understanding of the complex organization and assembly of the viral replicase via NS4B-NS5A interactions. IMPORTANCE Information about the functional role of the cytosolic face of the NS5A anchoring helix remains obscure. In this study, we show that while the hydrophobic face of the NS5A anchor helix mediates membrane association, the polar cytosolic face of the helix plays a key role during hepatitis C virus (HCV) replication by mediating the interaction of NS5A with other HCV nonstructural proteins via NS4B. Such an interaction determines the subcellular localization of NS5A by engaging NS5A in the HCV replication process during the formation of a functional HCV replication complex. Thus, collectively, it can be stated that the findings in the present study provide further information about the interactions between the HCV nonstructural proteins during HCV RNA replication and provide a platform to gain more insights about the molecular architecture of HCV replication complexes.
Collapse
|
6
|
Ghaderi M, Sabahi F, Sadeghi-Zadeh M, Khanlari Z, Jamaati A, Mousavi-Nasab D, Majidi-Gharenaz N, Ajorloo M, Fazeli M. Construction of an eGFP Expression Plasmid under Control of T7 Promoter and IRES Sequence for Assay of T7 RNA Polymerase Activity in Mammalian Cell Lines. Iran J Cancer Prev 2014; 7:137-41. [PMID: 25250164 PMCID: PMC4171830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 06/11/2014] [Indexed: 10/26/2022]
Abstract
BACKGROUND Recently, the use of T7 RNA polymerase instead of other viral and cellular promoters is increasing due to high efficacy of transcription in the cell cytoplasm by this polymerase. In order to translate the transcripts produced by T7 RNA polymerase in mammalian cell lines, it is necessary to include Internal Ribosome Entry Site (IRES) sequences. In addition, if sequence of poly A signal would be included after interested gene, the rate of expression could be increased in the cells. METHODS For expression of eGFP in HEK-293 and T7-BHK cells by T7 RNA polymerase, the sequence of eGFP as well as IRES sequences upstream of eGFP gene and poly A signal were inserted into a pUC57 plasmid. On the other hand, gene of T7 RNA polymerase was cloned into modified pIRES2-EGFP plasmid. Then, the constructed plasmids were transfected into HEK-293 cells. T7-BHK cell was used for control of T7 RNA polymerase activity. RESULTS Our results showed that using T7 RNA polymerase for expression of foreign genes in mammalian cell lines is highly efficient. CONCLUSION Highly efficient eGFP expression in HEK-293 cells showed that T7 RNA polymerase could be used for cytoplasmic RNA transcription such as production of anti-cancer proteins and oncolytic viral genomic RNA by reverse genetics.
Collapse
Affiliation(s)
- Mostafa Ghaderi
- Dept. of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Farzaneh Sabahi
- Dept. of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran,Corresponding Author:
Farzaneh Sabahi, PhD;
Professor of Virology
Tel: (+98) 21 44829122
| | - Majid Sadeghi-Zadeh
- Dept. of Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Zahra Khanlari
- Dept. of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Azam Jamaati
- Dept. of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Dawood Mousavi-Nasab
- Dept. of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | | | - Mehdi Ajorloo
- Dept. of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Maryam Fazeli
- Dept. of Virology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| |
Collapse
|
7
|
Chou C, Young DD, Deiters A. Photocaged t7 RNA polymerase for the light activation of transcription and gene function in pro- and eukaryotic cells. Chembiochem 2010; 11:972-7. [PMID: 20301166 DOI: 10.1002/cbic.201000041] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A light-activatable bacteriophage T7 RNA polymerase (T7RNAP) has been generated through the site-specific introduction of a photocaged tyrosine residue at the crucial position Tyr639 within the active site of the enzyme. The photocaged tyrosine disrupts polymerase activity by blocking the incoming nucleotide from reaching the active site of the enzyme. However, a brief irradiation with nonphototoxic UV light of 365 nm removes the ortho-nitrobenzyl caging group from Tyr639 and restores the RNA polymerase activity of T7RNAP. The complete orthogonality of T7RNAP to all endogenous RNA polymerases in pro- and eukaryotic systems allowed for the photochemical activation of gene expression in bacterial and mammalian cells. Specifically, E. coli cells were engineered to produce photocaged T7RNAP in the presence of a GFP reporter gene under the control of a T7 promoter. UV irradiation of these cells led to the spatiotemporal activation of GFP expression. In an analogous fashion, caged T7RNAP was transfected into human embryonic kidney (HEK293T) cells. Irradiation with UV light led to the activation of T7RNAP, thereby inducing RNA polymerization and expression of a luciferase reporter gene in tissue culture. The ability to achieve spatiotemporal regulation of orthogonal RNA synthesis enables the precise dissection and manipulation of a wide range of cellular events, including gene function.
Collapse
Affiliation(s)
- Chungjung Chou
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
| | | | | |
Collapse
|
8
|
Qureshi A, Zheng R, Parlett T, Shi X, Balaraman P, Cheloufi S, Murphy B, Guntermann C, Eagles P. Gene silencing of HIV chemokine receptors using ribozymes and single-stranded antisense RNA. Biochem J 2006; 394:511-8. [PMID: 16293105 PMCID: PMC1408682 DOI: 10.1042/bj20051268] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The chemokine receptors CXCR4 and CCR5 are required for HIV-1 to enter cells, and the progression of HIV-1 infection to AIDS involves a switch in the co-receptor usage of the virus from CCR5 to CXCR4. These receptors therefore make attractive candidates for therapeutic intervention, and we have investigated the silencing of their genes by using ribozymes and single-stranded antisense RNAs. In the present study, we demonstrate using ribozymes that a depletion of CXCR4 and CCR5 mRNAs can be achieved simultaneously in human PBMCs (peripheral blood mononuclear cells), cells commonly used by the virus for infection and replication. Ribozyme activity leads to an inhibition of the cell-surface expression of both CCR5 and CXCR4, resulting in a significant inhibition of HIV-1 replication when PBMCs are challenged with the virus. In addition, we show that small single-stranded antisense RNAs can also be used to silence CCR5 and CXCR4 genes when delivered to PBMCs. This silencing is caused by selective degradation of receptor mRNAs.
Collapse
MESH Headings
- Cells, Cultured
- DNA-Directed RNA Polymerases/metabolism
- Flow Cytometry
- Gene Expression
- Gene Silencing
- HIV-1/physiology
- Humans
- Leukocytes, Mononuclear/metabolism
- Leukocytes, Mononuclear/virology
- RNA, Antisense/biosynthesis
- RNA, Antisense/genetics
- RNA, Antisense/metabolism
- RNA, Catalytic/biosynthesis
- RNA, Catalytic/genetics
- RNA, Catalytic/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, CCR5/analysis
- Receptors, CCR5/genetics
- Receptors, CCR5/metabolism
- Receptors, CXCR4/analysis
- Receptors, CXCR4/genetics
- Receptors, CXCR4/metabolism
- Viral Proteins/metabolism
- Virus Replication
Collapse
Affiliation(s)
- Amer Qureshi
- *Randall Division of Cell and Molecular Biophysics, King's College London, University of London, Guy's Campus, London Bridge, London SE1 1UL, U.K
- †Department of Immunology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary College, University of London, London EC1A 7BE, U.K
| | - Richard Zheng
- †Department of Immunology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary College, University of London, London EC1A 7BE, U.K
| | - Terry Parlett
- *Randall Division of Cell and Molecular Biophysics, King's College London, University of London, Guy's Campus, London Bridge, London SE1 1UL, U.K
| | - Xiaoju Shi
- *Randall Division of Cell and Molecular Biophysics, King's College London, University of London, Guy's Campus, London Bridge, London SE1 1UL, U.K
- †Department of Immunology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary College, University of London, London EC1A 7BE, U.K
| | - Priyadhashini Balaraman
- *Randall Division of Cell and Molecular Biophysics, King's College London, University of London, Guy's Campus, London Bridge, London SE1 1UL, U.K
- †Department of Immunology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary College, University of London, London EC1A 7BE, U.K
| | - Sihem Cheloufi
- *Randall Division of Cell and Molecular Biophysics, King's College London, University of London, Guy's Campus, London Bridge, London SE1 1UL, U.K
| | - Brendan Murphy
- †Department of Immunology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary College, University of London, London EC1A 7BE, U.K
| | - Christine Guntermann
- †Department of Immunology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary College, University of London, London EC1A 7BE, U.K
| | - Peter Eagles
- *Randall Division of Cell and Molecular Biophysics, King's College London, University of London, Guy's Campus, London Bridge, London SE1 1UL, U.K
- To whom correspondence should be addressed (email )
| |
Collapse
|
9
|
Abstract
Until recently, the attention of most researchers has focused on the first and last steps of gene transfer, namely delivery to the cell and transcription, in order to optimise transfection and gene therapy. However, over the past few years, researchers have realised that the intracellular trafficking of plasmids is more than just a "black box" and is actually one of the major barriers to effective gene delivery. After entering the cytoplasm, following direct delivery or endocytosis, plasmids or other vectors must travel relatively long distances through the mesh of cytoskeletal networks before reaching the nuclear envelope. Once at the nuclear envelope, the DNA must either wait until cell division, or be specifically transported through the nuclear pore complex, in order to reach the nucleoplasm where it can be transcribed. This review focuses on recent developments in the understanding of these intracellular trafficking events as they relate to gene delivery. Hopefully, by continuing to unravel the mechanisms by which plasmids and other gene delivery vectors move throughout the cell, and by understanding the cell biology of gene transfer, superior methods of transfection and gene therapy can be developed.
Collapse
Affiliation(s)
- Rui Zhou
- Division of Pulmonary and Critical Care Medicine, Northwestern University, 240 E. Huron Avenue, McGaw 2336, Chicago IL 60611, USA
| | - R Christopher Geiger
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, 240 E. Huron Avenue, McGaw 2336, Chicago IL 60611, USA
| | - David A Dean
- Division of Pulmonary and Critical Care Medicine, Northwestern University, 240 E. Huron Avenue, McGaw 2336, Chicago IL 60611, USA
- Author for correspondence. Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, 240 E. Huron Avenue, McGaw 2336, Chicago, IL 60611, USA, Tel: +1 312 503 3121; Fax: +1 312 908 4650;
| |
Collapse
|
10
|
Tokmakov AA, Matsumoto E, Shirouzu M, Yokoyama S. Coupled cytoplasmic transcription-and-translation--a method of choice for heterologous gene expression in Xenopus oocytes. J Biotechnol 2005; 122:5-15. [PMID: 16202467 DOI: 10.1016/j.jbiotec.2005.08.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2005] [Revised: 08/17/2005] [Accepted: 08/24/2005] [Indexed: 11/21/2022]
Abstract
We demonstrate here that the intracellular environment of Xenopus oocytes is quite compatible with the requirements of T7 RNA polymerase (T7 RNAP)-mediated transcription. This reaction runs robustly in the oocyte cytoplasm for many hours. The coinjection of a T7 promoter-driven luciferase-encoding plasmid DNA and purified T7 RNAP into oocytes results in the prolonged production of luciferase protein. Thus, the efficient coupling of T7 RNAP-mediated transcription with the intrinsic oocyte translation machinery occurs in the oocyte cytoplasm. The coupled protein synthesis generates high expression yield, displays little variation in the expression level between individual oocytes, requires very limited amounts of DNA template and T7 RNAP, and does not affect the oocyte viability and functional status. Our detailed, quantitative comparison of the existing expression methods in Xenopus oocytes highlights the advantages of the technique based on the cytoplasmic coinjection of T7 RNAP and T7 promoter-driven plasmid DNA and demonstrates that it is greatly superior to the alternative methods of heterologous gene expression.
Collapse
|
11
|
Engleka KA, Lewis EW, Howard BH. Mechanisms of replication-deficient vaccinia virus/T7 RNA polymerase hybrid expression: effect of T7 RNA polymerase levels and alpha-amanitin. Virology 1998; 243:331-9. [PMID: 9568032 DOI: 10.1006/viro.1998.9070] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Components of the eukaryotic vaccinia virus/T7 RNA polymerase hybrid expression system were assessed using recombinant and nonrecombinant forms of modified vaccinia Ankara (MVA), a replication-deficient vaccinia virus strain. Recombinant MVA virus expressing T7 RNA polymerase (Wyatt, L. S., Moss, B., and Rozenblatt, S. (1995). Virology 210, 202-205) stimulated high levels of expression from a T7 promoter-chloramphenicol acetyltransferase (CAT) reporter. Most, but not all, of the virally induced expression was T7 RNA polymerase and T7 promoter dependent, with no viral enhancement of translation of T7 transcripts. The efficacy of supplying T7 RNA polymerase expression from nonviral sources was evaluated using a self-amplifying T7 RNA polymerase autogene or an inducible T7 RNA polymerase expression vector. The latter modes yielded CAT activity dependent on T7 RNA polymerase expression; however, expression required viral factors independent of T7 RNA polymerase and did not reach that attained using the recombinant virus. In further experiments, MVA-induced T7 RNA polymerase expression was upregulated by alpha-amanitin, an inhibitor of eukaryotic polymerases. This indicates that MVA/T7 RNA polymerase hybrid expression may be rendered still more efficient by ameliorating transcriptional interference due to an alpha-amanitin-sensitive eukaryotic factor(s).
Collapse
Affiliation(s)
- K A Engleka
- Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-2753, USA.
| | | | | |
Collapse
|
12
|
Abstract
A series of compounds containing a bile acid core and a polyamine side chain have been synthesized to evaluate their ability to promote the uptake of DNA into cells. These compounds differ from conventional cationic lipids because they contain a positively charged chain attached to a facial amphiphile rather than to a hydrophobic moiety. Formulations of several of the designed compounds were found to dramatically increase the cellular uptake of both plasmid and oligonucleotide DNA. Moreover, initial experiments have shown that some of the compounds promote plasmid gene expression in various tissues after introduction into animals. These results have provided interesting information about structure-activity relationships as well as clues to the mechanism of action that may lead to further improvements in the design.
Collapse
|
13
|
Abstract
The zebrafish system offers many unique opportunities for the study of molecular biology. To date, only random mutagenesis, and not directed gene knockouts, have been demonstrated in this system. To more fully develop the potential of the zebrafish system, an approach to effectively inhibit the expression of any targeted gene in the developing zebrafish embryo has been developed. This approach uses a transient, cytoplasmic, T7 expression system, injected into the fertilized zebrafish egg to rapidly produce high levels of a ribozyme directed against the mRNA encoded by the targeted gene to inhibit its expression. In a demonstration of this strategy, expression of the recessive dominant zebrafish no tail gene was effectively inhibited by using this strategy to yield a phenotype identical to that resulting from a known defective mutation in this same gene. This, ribozyme-mediated, message deletion strategy may have use in determining the function of genetic coding sequences of unknown function.
Collapse
Affiliation(s)
- Y Xie
- The Edison Institute, Graduate Program in Molecular and Cellular Biology, and the Department of Clinical Research, College of Medicine, Ohio University, Athens, OH 45701, USA
| | | | | |
Collapse
|
14
|
Sturtz FG, Waddell K, Shulok J, Chen X, Caruso M, Sanson M, Snodgrass HR, Platika D. Variable efficiency of the thymidine kinase/ganciclovir system in human glioblastoma cell lines: implications for gene therapy. Hum Gene Ther 1997; 8:1945-53. [PMID: 9382960 DOI: 10.1089/hum.1997.8.16-1945] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The gene therapy strategy using the hsvl-thymidine kinase gene (TK) and ganciclovir (GCV) injections that has been used for treating human glioblastomas has not been as effective as expected after the first animal experiments. A better understanding of the different steps involved in this treatment, like gene transfer, gene expression, and sensitivity of the recipient cells, is needed. After proposing sensitivity criteria for the TK/GCV system and for the bystander effect, based on the levels of GCV that can be reached in vivo, we studied seven human glioblastoma cell lines (U87, U118, U251, SNB19, SNB75, SF295, SF539) for their sensitivity to the TK/GCV system. We also studied their in vitro bystander effect and their in vitro transfectability using LipofectAMINE as a transfection enhancer. Among six human glioblastoma cell lines stably transfected with the TK gene, five were sensitive to TK/GCV, and two had a good in vitro bystander effect. The in vitro transfectability of the cell lines tested was low (< or = 1%) compared to that of an established animal cell line, C6 rat glioma, in which 20-30% of the cells can be transfected routinely. According to this in vitro analysis, most of the glioblastoma cell lines should be sensitive to the TK/GCV system, but there is an urgent need for agents to increase transfection efficiency.
Collapse
Affiliation(s)
- F G Sturtz
- Progenitor Inc., Menlo Park, CA 94025, USA
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Selby MJ, Doe B, Walker CM. Virus-specific cytotoxic T-lymphocyte activity elicited by coimmunization with human immunodeficiency virus type 1 genes regulated by the bacteriophage T7 promoter and T7 RNA polymerase protein. J Virol 1997; 71:7827-31. [PMID: 9311870 PMCID: PMC192137 DOI: 10.1128/jvi.71.10.7827-7831.1997] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Cytotoxic T lymphocyte (CTL) activity was assessed in mice immunized with DNA plasmids containing the human immunodeficiency virus type 1 (HIV-1) gp120 envelope (pTMIgp120) or p55gag (pTMIgag) gene regulated by the bacteriophage T7 promoter. Immunization with either plasmid resulted in CTL activity against class I major histocompatibility complex-restricted viral epitopes when coadministered with a recombinant vaccinia virus expressing the T7 RNA polymerase protein (T7 RNAP) but not a control vaccinia virus. Recombinant vaccinia-T7 RNAP virus (VTF7-3) could be replaced with a noninfectious source of T7 RNAP. A three-component vaccine consisting of pTMIgag, a recombinant subunit T7 RNAP protein, and a plasmid (pT7T7) encoding T7 RNAP under the control of its own promoter induced gag-specific CTL activity. Intramuscular immunization with the pTMIgag plasmid delivered with either the T7 RNAP protein or pT7T7 plasmid alone also induced HIV-1-specific CTL. Thus, there is adventitious expression of the pT7T7 plasmid in vivo, and enough T7 RNAP is produced to result in production of p24gag protein from the pTMIgag plasmid. The results demonstrate that regulated expression of genes in vivo is possible with this T7-based expression system, and may be useful in vaccine settings where short-term cytoplasmic expression of protein in antigen presenting cells is desired.
Collapse
Affiliation(s)
- M J Selby
- Chiron Corporation, Emeryville, California 94608, USA
| | | | | |
Collapse
|
16
|
Abstract
Current methods of gene transfer have a rather low efficiency, especially in vivo. Therefore, one tries to achieve the highest possible levels of expression in the few cells that do take up foreign DNA. One approach is to use self-amplifying expression vectors. These vectors are based on the (+)-strand RNA viruses (alphaviruses) Sindbis virus and Semliki Forest virus. In these vectors, the viral capsid protein coding sequences are replaced with the gene of interest. After introduction into the target cells, the viral replication proteins will replicate the recombinant genome. The increased levels of mRNA generate very high transgene expression levels. Furthermore, spread throughout large cells (muscle, neurons) is much better compared to conventional expression cassettes. Self-amplifying vectors can be introduced into target cells as RNA, DNA or virions.
Collapse
|
17
|
Abstract
An autoregulated gene expression system in Escherichia coli was designed such that the cloned genes on the vector were not expressed until biotin was depleted during cell growth. The expression vectors were constructed by assembling the DNA fragments containing the regulatory region of the E. coli biotin operon (bio operon), the universal ribosome-binding site (RBS) and the strong transcription terminator rrnBT1T2. The promoter region was further modified by site-directed mutagenesis to create promoters of varied strength. The feasibility of this system was examined in E. coli strain R901 (with bio operon deleted) using various marker genes, including the E. coli birA gene, T7 RNA polymerase gene and yellowfin-porgy growth-hormone gene. The results demonstrated that the induction of marker-gene expression can be triggered as the biotin concentration drops to a threshold value of approximately 2 ng/mL by metabolic utilization.
Collapse
Affiliation(s)
- Y S Chang
- Department of Biology, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC
| | | |
Collapse
|
18
|
Abstract
We had earlier overproduced the transcription activator protein C of bacteriophage Mu in a phage-T7 expression system. Although we achieved a high level of overproduction, the expression was not consistent. This could be due to the leaky expression of T7 RNA polymerase in the uninduced state. Introduction of pLysS, a plasmid encoding T7 lysozyme, a natural inhibitor of T7 RNA polymerase, resulted in consistent, but extremely low production of the C protein. To overcome this problem, we have devised an artificial regulatory circuit to obtain stabilised, consistent overproduction of C protein. The C-binding site was cloned downstream from the transcription start point of T7 lys. Upon induction, the C protein produced binds to its site with a very high affinity, possibly acting as a transcriptional roadblock for lys. This would overcome the inhibitory effect of T7 lysozyme on T7 RNA polymerase.
Collapse
Affiliation(s)
- B D Paul
- Centre for Genetic Engineering, Indian Institute of Science, Bangalore
| | | | | |
Collapse
|
19
|
Abstract
We have developed expression vectors that direct the synthesis of proteins from a common set of signals in both prokaryotic and eukaryotic cells. To allow transcription from a common promoter the vectors rely upon a phage RNA polymerase (RNAP). To direct initiation of translation to the same start codon the vectors utilize an internal ribosome entry site (IRES) from encephalomyocarditis virus (EMCV) that has been modified to include a prokaryotic ribosome-binding site (RBS) at an appropriate distance upstream from the desired start codon. These vectors provide levels of expression in eukaryotic cells that exceed those of a conventional RNAP-II-based system by 7-fold, and expression in bacterial cells at levels comparable to other phage RNAP-based systems. Inclusion of a lac repressor and a phage promoter/lac operator fusion element allows tight regulation. Cotransfection of eukaryotic cells with the expression vector and a vector that encodes the phage RNAP provides high-level transient expression without the need to construct specialized stable cell lines.
Collapse
Affiliation(s)
- B He
- Morse Institute for Molecular Genetics, Department of Microbiology and Immunology, SUNY Health Science Center at Brooklyn 11203-2098, USA
| | | | | |
Collapse
|