1
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Hoeher JE, Sande NE, Widom JR. Probing and perturbing riboswitch folding using a fluorescent base analogue. Photochem Photobiol 2024; 100:419-433. [PMID: 38098287 PMCID: PMC10950518 DOI: 10.1111/php.13896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 03/20/2024]
Abstract
Riboswitches are mRNA segments that regulate gene expression in response to ligand binding. The Class I preQ1 riboswitch consists of a stem-loop and an adenine-rich single-stranded tail ("L3"), which adopt a pseudoknot structure upon binding of the ligand preQ1 . We inserted 2-aminopurine (2-AP), a fluorescent analogue of adenine (A), into the riboswitch at six different positions within L3. Here, 2-AP functions both as a spectroscopic probe and as a "mutation" that reveals how alteration of specific A residues impacts the riboswitch. Using fluorescence and circular dichroism spectroscopy, we found that 2-AP decreases the affinity of the riboswitch for preQ1 at all labeling positions tested, although modified and unmodified variants undergo the same global conformational changes at sufficiently high preQ1 concentration. 2-AP substitution is most detrimental to ligand binding at sites proximal to the ligand-binding pocket, while distal labeling sites exhibit the largest impacts on the stability of the L3 domain in the absence of ligand. Insertion of multiple 2-AP residues does not induce significant additional disruptions. Our results show that interactions involving the A residues in L3 play a critical role in ligand recognition by the preQ1 riboswitch and that 2-AP substitution exerts complex and varied impacts on this riboswitch.
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Affiliation(s)
- Janson E. Hoeher
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR
| | - Natalie E. Sande
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR
| | - Julia R. Widom
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR
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2
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Ngo HTT, Nguyen DH, You SH, Van Nguyen K, Kim SY, Hong Y, Min JJ. Reprogramming a Doxycycline-Inducible Gene Switch System for Bacteria-Mediated Cancer Therapy. Mol Imaging Biol 2024; 26:148-161. [PMID: 38017353 DOI: 10.1007/s11307-023-01879-6] [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: 09/08/2023] [Revised: 11/12/2023] [Accepted: 11/13/2023] [Indexed: 11/30/2023]
Abstract
PURPOSE Attenuated Salmonella typhimurium is a potential biotherapeutic antitumor agent because it can colonize tumors and inhibit their growth. The present study aimed to develop a doxycycline (Doxy)-inducible gene switch system in attenuated S. typhimurium and assess its therapeutic efficacy in various tumor-bearing mice models. PROCEDURES A Doxy-inducible gene switch system comprising two plasmids was engineered to trigger the expression of cargo genes (Rluc8 and clyA). Attenuated S. typhimurium carrying Rluc8 were injected intravenously into BALB/c mice bearing CT26 tumors, and bioluminescence images were captured at specified intervals post-administration of doxycycline. The tumor-suppressive effects of bacteria carrying clyA were evaluated in BALB/c mice bearing CT26 tumors and in C57BL/6 mice bearing MC38 tumors. RESULTS Expression of the fimE gene, induced only in the presence of Doxy, triggered a unidirectional switch of the POXB20 promoter to induce expression of the cargo genes. The switch event was maintained over a long period of bacterial culture. After intravenous injection of transformed Salmonella into mice bearing CT26 tumors, the bacteria transformed with the Doxy-inducible gene switch system for Rluc8 targeted only tumor tissues and expressed the payloads 2 days after Doxy treatment. Notably, bacteria carrying the Doxy-inducible gene switch system for clyA effectively suppressed tumor growth and prolonged survival, even after just one Doxy induction. CONCLUSIONS These results suggest that attenuated S. typhimurium carrying this novel gene switch system elicited significant therapeutic effects through a single induction triggering and were a potential biotherapeutic agent for tumor therapy.
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Affiliation(s)
- Hien Thi-Thu Ngo
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
- Department of Biochemistry, Hanoi Medical University, No 1, Ton That Tung St., Dong Da, Hanoi, 100000, Vietnam
| | - Dinh-Huy Nguyen
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
| | - Sung-Hwan You
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- CNCure Biotech, Hwasun, 58128, Republic of Korea
| | - Khuynh Van Nguyen
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea
| | - So-Young Kim
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
- CNCure Biotech, Hwasun, 58128, Republic of Korea
| | - Yeongjin Hong
- CNCure Biotech, Hwasun, 58128, Republic of Korea.
- Department of Microbiology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea.
| | - Jung-Joon Min
- Institute for Molecular Imaging and Theranostics, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea.
- Department of Molecular Medicine (BrainKorea21 Plus), Chonnam National University Graduate School, Gwangju, 61469, Republic of Korea.
- CNCure Biotech, Hwasun, 58128, Republic of Korea.
- Department of Nuclear Medicine, Chonnam National University Medical School and Hwasun Hospital, Gwangju, 61469, Republic of Korea.
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3
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Arcidiacono S, Spangler JR, Litteral V, Doherty LA, Stamps B, Walper S, Goodson M, Soares JW. In Vitro Fermentation Evaluation of Engineered Sense and Respond Probiotics in Polymicrobial Communities. ACS Biomater Sci Eng 2023; 9:5176-5185. [PMID: 37642529 DOI: 10.1021/acsbiomaterials.3c00630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Synthetic biology provides a means of engineering tailored functions into probiotic bacteria. Of particular interest is introducing microbial sense and response functions; however, techniques for testing in physiologically relevant environments, such as those for the intended use, are still lacking. Typically, engineered probiotics are developed and tested in monoculture or in simplified cocultures still within ideal environments. In vitro fermentation models using simplified microbial communities now allow us to simulate engineered organism behavior, specifically organism persistence and intended functionality, within more physiologically relevant, tailored microbial communities. Here, probiotic bacteria Escherichia coli Nissle and Lactobacillus plantarum engineered with sense and response functionalities were evaluated for the ability to persist and function without adverse impact on commensal bacteria within simplified polymicrobial communities with increasing metabolic competition that simulate gut microbe community dynamics. Probiotic abundance and plasmid stability, measured by viability qPCR, decreased for engineered E. coli Nissle relative to monocultures as metabolic competition increased; functional output was not affected. For engineered L. plantarum, abundance and plasmid stability were not adversely impacted; however, functional output was decreased universally as metabolic competition was introduced. For both organisms, adverse effects on select commensals were not evident. Testing engineered probiotics in more physiologically relevant in vitro test beds can provide critical knowledge for circuit design feedback and functional validation prior to the transition to more costly and time-consuming higher-fidelity testing in animal or human studies.
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Affiliation(s)
- Steven Arcidiacono
- Soldier Effectiveness Directorate, US Army DEVCOM Soldier Center, Natick, Massachusetts 01760, United States
| | - Joseph R Spangler
- Center for Bio/Molecular Science & Engineering, US Naval Research Laboratory, Washington, D.C.20375, United States
| | - Vaughn Litteral
- UES Inc, US Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, United States
| | - Laurel A Doherty
- Soldier Effectiveness Directorate, US Army DEVCOM Soldier Center, Natick, Massachusetts 01760, United States
| | - Blake Stamps
- 711th Human Performance Wing, US Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, United States
| | - Scott Walper
- Center for Bio/Molecular Science & Engineering, US Naval Research Laboratory, Washington, D.C.20375, United States
| | - Michael Goodson
- 711th Human Performance Wing, US Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, United States
| | - Jason W Soares
- Soldier Effectiveness Directorate, US Army DEVCOM Soldier Center, Natick, Massachusetts 01760, United States
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4
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Qin Y, You SH, Zhang Y, Venu A, Hong Y, Min JJ. Genetic Programming by Nitric Oxide-Sensing Gene Switch System in Tumor-Targeting Bacteria. BIOSENSORS 2023; 13:266. [PMID: 36832032 PMCID: PMC9954711 DOI: 10.3390/bios13020266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 02/01/2023] [Accepted: 02/10/2023] [Indexed: 06/18/2023]
Abstract
Recent progress in synthetic biology has enabled bacteria to respond to specific disease signals to perform diagnostic and/or therapeutic tasks. Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) colonization of tumors results in increases in nitric oxide (NO) levels, suggesting that NO may act as a candidate inducer of tumor-specific gene expression. The present study describes a NO-sensing gene switch system for triggering tumor-specific gene expression in an attenuated strain of S. Typhimurium. The genetic circuit was designed to sense NO via NorR, thus initiating the expression of FimE DNA recombinase. This was found to lead sequentially to the unidirectional inversion of a promoter region (fimS), which induced the expression of target genes. Target gene expression in bacteria transformed with the NO-sensing switch system was triggered in the presence of a chemical source of NO, diethylenetriamine/nitric oxide (DETA/NO) in vitro. In vivo results revealed that the gene expression is tumor-targeted, and specific to NO generated by inducible nitric oxide synthase (iNOS) after S. Typhimurium colonization. These results showed that NO was a promising inducer to finely tune the expression of target genes carried by tumor-targeting bacteria.
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Affiliation(s)
- Yeshan Qin
- Department of Molecular Medicine, Chonnam National University Graduate School, Gwangju 61469, Republic of Korea
- Institute for Molecular Imaging and Theranostics, Hwasun Hospital, Chonnam National University Medical School, Gwangju 58128, Republic of Korea
| | - Sung-Hwan You
- Institute for Molecular Imaging and Theranostics, Hwasun Hospital, Chonnam National University Medical School, Gwangju 58128, Republic of Korea
| | - Ying Zhang
- Department of Molecular Medicine, Chonnam National University Graduate School, Gwangju 61469, Republic of Korea
- Institute for Molecular Imaging and Theranostics, Hwasun Hospital, Chonnam National University Medical School, Gwangju 58128, Republic of Korea
| | - Akhil Venu
- Institute for Molecular Imaging and Theranostics, Hwasun Hospital, Chonnam National University Medical School, Gwangju 58128, Republic of Korea
| | - Yeongjin Hong
- Department of Microbiology, Chonnam National University Medical School, Gwangju 58128, Republic of Korea
| | - Jung-Joon Min
- Department of Molecular Medicine, Chonnam National University Graduate School, Gwangju 61469, Republic of Korea
- Institute for Molecular Imaging and Theranostics, Hwasun Hospital, Chonnam National University Medical School, Gwangju 58128, Republic of Korea
- Department of Nuclear Medicine, Chonnam National University Medical School, Gwangju 61469, Republic of Korea
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5
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Li R, Chen S, Li Y, Chen X, Ye BC. Development of a "Turn off-on" whole-cell biosensor for sulforaphane detection based on the ultrasensitive activator HrpRS. Biotechnol Appl Biochem 2022; 70:798-810. [PMID: 36070874 DOI: 10.1002/bab.2400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 08/13/2022] [Indexed: 11/09/2022]
Abstract
Sulforaphane (SFN), a defense secondary metabolite, can be used to predict the health status of plants and also has pharmacological effects, including anticancer, antioxidant, and anti-inflammatory properties. The detection of SFN is therefore of great significance for the prevention and treatment of diseases. In this study, a "Turn off" whole-cell biosensor that can rapidly and robustly respond to the presence of SFN was constructed based on the orthogonal genetic components (hrpR, hrpS, and PhrpL ) of Pseudomonas syringae (PS). The final optimized biosensor, p114(30R-30S), was able to inhibit 91.7% of the fluorescence intensity in the presence of 100-μM SFN. Subsequently, a HrpRS-regulated OFF-ON genetic switch was designed by reconstituting a reverse σ70 promoter on the σ54 -PhrpL promoter sequence; this was coupled with dual-color reporter genes to construct a "Turn off-on" whole-cell SFN biosensor. The PhrpLB variant increased the expression of green fluorescence a factor of 11.9 and reduced the expression of red fluorescence by 85.8% compared with the system in the absence of SFN. Thus, a robust switching of signal output from "turn off" to "turn on" was realized. In addition, the biosensor showed good linearity in the SFN concentration ranges of 0.1-10 μM (R2 = 0.99429) and 10-100 μM (R2 = 0.99465) and a detection limit of ⁓0.1 μM. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Renjie Li
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Shengyan Chen
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Yangguang Li
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Xuan Chen
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Bang-Ce Ye
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China.,Institute of Engineering Biology and Health, Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, China.,Lab of Biosystem and Microanalysis, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
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6
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Synthetic biology-powered microbial co-culture strategy and application of bacterial cellulose-based composite materials. Carbohydr Polym 2022; 283:119171. [DOI: 10.1016/j.carbpol.2022.119171] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 11/18/2022]
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7
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Arcidiacono S, Breedon AME, Goodson MS, Doherty LA, Lyon W, Jimenez G, Pantoja-Feliciano IG, Soares JW. In vitro fermentation test bed for evaluation of engineered probiotics in polymicrobial communities. J Biol Methods 2021; 8:e147. [PMID: 34104665 PMCID: PMC8175340 DOI: 10.14440/jbm.2021.347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 03/12/2021] [Accepted: 03/12/2021] [Indexed: 12/25/2022] Open
Abstract
In vitro fermentation systems offer significant opportunity for deconvoluting complex metabolic dynamics within polymicrobial communities, particularly those associated with the human gut microbiome. In vitro gut models have broad experimental capacity allowing rapid evaluation of multiple parameters, generating knowledge to inform design of subsequent in vivo studies. Here, our method describes an in vitro fermentation test bed to provide a physiologically-relevant assessment of engineered probiotics circuit design functions. Typically, engineered probiotics are evaluated under pristine, mono- or co-culture conditions and transitioned directly into animal or human studies, commonly resulting in a loss of desired function when introduced to complex gut communities. Our method encompasses a systematic workflow entailing fermentation, molecular and functional characterization, and statistical analyses to validate an engineered probiotic’s persistence, plasmid stability and reporter response. To demonstrate the workflow, simplified polymicrobial communities of human gut microbial commensals were utilized to investigate the probiotic Escherichia coli Nissle 1917 engineered to produce a fluorescent reporter protein. Commensals were assembled with increasing complexity to produce a mock community based on nutrient utilization. The method assesses engineered probiotic persistence in a competitive growth environment, reporter production and function, effect of engineering on organism growth and influence on commensal composition. The in vitro test bed represents a new element within the Design-Build-Test-Learn paradigm, providing physiologically-relevant feedback for circuit re-design and experimental validation for transition of engineered probiotics to higher fidelity animal or human studies.
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Affiliation(s)
- Steven Arcidiacono
- Soldier Effectiveness Directorate, DEVCOM Soldier Center, Natick, MA 01760, USA
| | - Amy M Ehrenworth Breedon
- 711 th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA.,UES, Inc., Dayton, OH 45432, USA
| | - Michael S Goodson
- 711 th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA
| | - Laurel A Doherty
- Soldier Effectiveness Directorate, DEVCOM Soldier Center, Natick, MA 01760, USA
| | - Wanda Lyon
- 711 th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA
| | - Grace Jimenez
- 711 th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA.,UES, Inc., Dayton, OH 45432, USA
| | | | - Jason W Soares
- Soldier Effectiveness Directorate, DEVCOM Soldier Center, Natick, MA 01760, USA
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8
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Recent advances in tuning the expression and regulation of genes for constructing microbial cell factories. Biotechnol Adv 2021; 50:107767. [PMID: 33974979 DOI: 10.1016/j.biotechadv.2021.107767] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 04/29/2021] [Accepted: 05/05/2021] [Indexed: 12/14/2022]
Abstract
To overcome environmental problems caused by the use of fossil resources, microbial cell factories have become a promising technique for the sustainable and eco-friendly development of valuable products from renewable resources. Constructing microbial cell factories with high titers, yields, and productivity requires a balance between growth and production; to this end, tuning gene expression and regulation is necessary to optimise and precisely control complicated metabolic fluxes. In this article, we review the current trends and advances in tuning gene expression and regulation and consider their engineering at each of the three stages of gene regulation: genomic, mRNA, and protein. In particular, the technological approaches utilised in a diverse range of genetic-engineering-based tools for the construction of microbial cell factories are reviewed and representative applications of these strategies are presented. Finally, the prospects for strategies and systems for tuning gene expression and regulation are discussed.
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9
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Manna S, Truong J, Hammond MC. Guanidine Biosensors Enable Comparison of Cellular Turn-on Kinetics of Riboswitch-Based Biosensor and Reporter. ACS Synth Biol 2021; 10:566-578. [PMID: 33646758 PMCID: PMC7985839 DOI: 10.1021/acssynbio.0c00583] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Indexed: 12/30/2022]
Abstract
Cell-based sensors are useful for many synthetic biology applications, including regulatory circuits, metabolic engineering, and diagnostics. While considerable research efforts have been made toward recognizing new target ligands and increasing sensitivity, the analysis and optimization of turn-on kinetics is often neglected. For example, to our knowledge there has been no systematic study that compared the performance of a riboswitch-based biosensor versus reporter for the same ligand. In this study, we show the development of RNA-based fluorescent (RBF) biosensors for guanidine, a common chaotropic agent that is a precursor to both fertilizer and explosive compounds. Guanidine is cell permeable and nontoxic to E. coli at millimolar concentrations, which in contrast to prior studies enabled direct activation of the riboswitch-based biosensor and corresponding reporter with ligand addition to cells. Our results reveal that the biosensors activate fluorescence in the cell within 4 min of guanidine treatment, which is at least 15 times faster than a reporter derived from the same riboswitch, and this rapid sensing activity is maintained for up to 1.6 weeks. Together, this study describes the design of two new biosensor topologies and showcases the advantages of RBF biosensors for monitoring dynamic processes in cell biology, biotechnology, and synthetic biology.
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Affiliation(s)
- Sudeshna Manna
- Department
of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
- Henry
Eyring Center for Cell & Genome Science, University of Utah, Salt Lake
City, Utah 84112, United States
| | - Johnny Truong
- Department
of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
- Henry
Eyring Center for Cell & Genome Science, University of Utah, Salt Lake
City, Utah 84112, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Ming C. Hammond
- Department
of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
- Henry
Eyring Center for Cell & Genome Science, University of Utah, Salt Lake
City, Utah 84112, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
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10
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Chushak Y, Harbaugh S, Zimlich K, Alfred B, Chávez J, Kelley-Loughnane N. Characterization of synthetic riboswitch in cell-free protein expression systems. RNA Biol 2021; 18:1727-1738. [PMID: 33427029 DOI: 10.1080/15476286.2020.1868149] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Riboswitches are RNA-based regulatory elements that utilize ligand-induced structural changes in the 5'-untranslated region of mRNA to regulate the expression of associated genes. The majority of synthetic riboswitches have been selected and tested in cell-based systems. Cell-free protein expression systems (CFPS) have several advantages for the development and testing of synthetic riboswitches, including eliminating interactions with complex cellular networks, and the decoupling of transcription and translation processes. To gain a better understanding of the riboswitch regulatory mechanism, to allow for more efficient riboswitch optimization and use for biosensing applications, we studied the performance of a theophylline-responsive synthetic riboswitch coupled with the superfolder green fluorescent protein (sfGFP) reporter gene in E. coli cellular extract and PURE cell-free systems. To monitor the mRNA dynamics, a malachite green aptamer sequence was added to the 3'-untranslated region of sfGFP mRNA. Performance of the theophylline riboswitch was compared with a constitutively expressed sfGFP (control). Transcription dynamics of the riboswitch mRNA was very similar to the transcription of the control mRNA for all theophylline concentrations tested in both E. coli extract and PURE CFPS. However, sfGFP expression in the riboswitch construct was one order of magnitude lower, even at the highest concentration of theophylline. A mathematical model of riboswitch activation governed by the kinetic trapping mechanism was developed. Two factors - a reduced fraction of mRNA in the 'ON' state and a considerably lower translation initiation rate in the riboswitch - contribute to the much lower level of protein expression in the theophylline riboswitch compared to the control construct.
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Affiliation(s)
- Yaroslav Chushak
- Air Force Research Laboratory, Henry M Jackson Foundation, Dayton, USA.,711 Human Performance Wing, Air Force Research Laboratory, Dayton, OH, USA
| | - Svetlana Harbaugh
- 711 Human Performance Wing, Air Force Research Laboratory, Dayton, OH, USA
| | - Kathryn Zimlich
- Air Force Research Laboratory, Henry M Jackson Foundation, Dayton, USA.,711 Human Performance Wing, Air Force Research Laboratory, Dayton, OH, USA
| | - Bryan Alfred
- 711 Human Performance Wing, Air Force Research Laboratory, Dayton, OH, USA
| | - Jorge Chávez
- 711 Human Performance Wing, Air Force Research Laboratory, Dayton, OH, USA
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11
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Drachuk I, Harbaugh S, Chávez JL, Kelley-Loughnane N. Improving the Activity of DNA-Encoded Sensing Elements through Confinement in Silk Microcapsules. ACS APPLIED MATERIALS & INTERFACES 2020; 12:48329-48339. [PMID: 33064462 DOI: 10.1021/acsami.0c13713] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Assembling synthetic bioparts into simplified artificial cells holds tremendous promise for advancing studies into the synthesis, biosensing, and delivery of biomolecules. Currently, the most successful techniques for encapsulation of the transcription-translation machinery exploit compartmentalization in liposomal vesicles. However, improvements to these methods may increase permeability to polar molecules, functionalization of the membrane with biologically active elements, and encapsulation efficiency. Microcapsules prepared via templated layer-by-layer (LbL) assembly using natural polymers have the potential to resolve some of the hurdles associated with liposomes. Here, we introduce a design for immobilizing DNA templates encoding translationally activated riboswitches and RNA aptamers into microcapsules prepared from regenerated silk fibroin protein. Adjusting several key parameters such as the presence of a polymer primer, concentration of silk protein, and DNA loadings during LbL assembly resulted in biocompatible, semipermeable, DNA-laden microcapsules. To preserve bioactivity, DNA was immobilized inside of the capsule membrane, which not only promoted stability during long-term storage at ambient conditions but also improved output response from spatially confined DNA-encoded sensing elements (SEs). Multiple copies of mRNA and GFPa1 protein were synthesized upon activation with specific analytes during in vitro transcription/translation reactions, demonstrating that selective permeability of silk microcapsules was essential for the diffusion of components of the cell-free system inside of the capsules. Further functionalization of capsule shells with gold nanoparticles (AuNPs) and antibodies (IgG) demonstrated the applicability of microcompartmentalized colloidal objects carrying SEs for remote sensing and/or targeted delivery. In the future, multifunctional, biocompatible silk-based microcapsules loaded with different RNA sensors can help advance the design of multiplexed biosensors tracking multiple biomarkers in complex media.
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Affiliation(s)
- Irina Drachuk
- UES Inc., Dayton, Ohio 45432, United States
- 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, Ohio 45433, United States
| | - Svetlana Harbaugh
- 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, Ohio 45433, United States
| | - Jorge L Chávez
- 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, Ohio 45433, United States
| | - Nancy Kelley-Loughnane
- 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, Ohio 45433, United States
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Dayton, Ohio 45433, United States
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12
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Naseri G, Koffas MAG. Application of combinatorial optimization strategies in synthetic biology. Nat Commun 2020; 11:2446. [PMID: 32415065 PMCID: PMC7229011 DOI: 10.1038/s41467-020-16175-y] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Accepted: 04/15/2020] [Indexed: 12/26/2022] Open
Abstract
In the first wave of synthetic biology, genetic elements, combined into simple circuits, are used to control individual cellular functions. In the second wave of synthetic biology, the simple circuits, combined into complex circuits, form systems-level functions. However, efforts to construct complex circuits are often impeded by our limited knowledge of the optimal combination of individual circuits. For example, a fundamental question in most metabolic engineering projects is the optimal level of enzymes for maximizing the output. To address this point, combinatorial optimization approaches have been established, allowing automatic optimization without prior knowledge of the best combination of expression levels of individual genes. This review focuses on current combinatorial optimization methods and emerging technologies facilitating their applications.
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Affiliation(s)
- Gita Naseri
- Institut für Chemie, Humboldt Universität zu Berlin, 12489, Berlin, Germany.
| | - Mattheos A G Koffas
- Center for Biotechnology, Rensselaer Polytechnic Institute, Troy, NY, USA.
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, USA.
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13
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Wrist A, Sun W, Summers RM. The Theophylline Aptamer: 25 Years as an Important Tool in Cellular Engineering Research. ACS Synth Biol 2020; 9:682-697. [PMID: 32142605 DOI: 10.1021/acssynbio.9b00475] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The theophylline aptamer was isolated from an oligonucleotide library in 1994. Since that time, the aptamer has found wide utility, particularly in synthetic biology, cellular engineering, and diagnostic applications. The primary application of the theophylline aptamer is in the construction and characterization of synthetic riboswitches for regulation of gene expression. These riboswitches have been used to control cellular motility, regulate carbon metabolism, construct logic gates, screen for mutant enzymes, and control apoptosis. Other applications of the theophylline aptamer in cellular engineering include regulation of RNA interference and genome editing through CRISPR systems. Here we describe the uses of the theophylline aptamer for cellular engineering over the past 25 years. In so doing, we also highlight important synthetic biology applications to control gene expression in a ligand-dependent manner.
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Affiliation(s)
- Alexandra Wrist
- Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Wanqi Sun
- Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Ryan M. Summers
- Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, United States
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14
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Guo KH, Lu KH, Yeh YC. Cell-Based Biosensor with Dual Signal Outputs for Simultaneous Quantification of Phenylacetic Acid and Phenylethylamine. ACS Synth Biol 2018; 7:2790-2795. [PMID: 30418753 DOI: 10.1021/acssynbio.8b00416] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Despite the importance of 2-phenylacetic acid, a plant hormone in the endogenous auxin family, its biosynthesis pathway has yet to be elucidated. In this study, we developed a novel whole-cell biosensor for the simultaneous quantification of 2-phenylacetic acid (PA) and 2-phenylethylamine (PEA) through the regulation of bacterial catabolism of aromatic compounds. We used the PA regulon to enable the recognition of PA and PEA. Differentiation of PEA from PA involves the incorporation of the FeaR regulon within the same whole-cell biosensor to report the presence of aromatic amines. The proposed system is highly sensitive to PA as well as PEA.
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Affiliation(s)
- Kai-Hong Guo
- Department of Chemistry, National Taiwan Normal University, 88, Section 4, Tingzhou Road, Taipei 11677, Taiwan
| | - Kun-Hua Lu
- Department of Chemistry, National Taiwan Normal University, 88, Section 4, Tingzhou Road, Taipei 11677, Taiwan
| | - Yi-Chun Yeh
- Department of Chemistry, National Taiwan Normal University, 88, Section 4, Tingzhou Road, Taipei 11677, Taiwan
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15
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Harbaugh SV, Martin JA, Weinstein J, Ingram G, Kelley-Loughnane N. Screening and selection of artificial riboswitches. Methods 2018; 143:77-89. [PMID: 29778645 DOI: 10.1016/j.ymeth.2018.05.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 05/14/2018] [Accepted: 05/15/2018] [Indexed: 01/04/2023] Open
Abstract
Synthetic riboswitches are engineered to regulate gene expression in response to a variety of non-endogenous small molecules, and a challenge to select this engineered response requires robust screening tools. A new synthetic riboswitch can be created by linking an in vitro-selected aptamer library with a randomized expression platform followed by in vivo selection and screening. In order to determine response to analyte, we developed a dual-color reporter comprising elements of the E. coli fimbriae phase variation system: recombinase FimE controlled by a synthetic riboswitch and an invertible DNA segment (fimS) containing a constitutively active promoter placed between two fluorescent protein genes. Without an analyte, the fluorescent reporter constitutively expressed green fluorescent protein (GFPa1). Addition of the analyte initiated translation of fimE causing unidirectional inversion of the fimS segment and constitutive expression of red fluorescent protein (mKate2). The dual color reporter system can be used to select and to optimize artificial riboswitches in E. coli cells. In this work, the enriched library of aptamers incorporated into the riboswitch architecture reduces the sequence search space by offering a higher percentage of potential ligand binders. The study was designed to produce structure switching aptamers, a necessary feature for riboswitch function and efficiently quantify this function using the dual color reporter system.
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Affiliation(s)
- Svetlana V Harbaugh
- Airman Systems Directorate, 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, United States
| | - Jennifer A Martin
- Airman Systems Directorate, 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, United States
| | - Jenna Weinstein
- Airman Systems Directorate, 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, United States
| | - Grant Ingram
- Airman Systems Directorate, 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, United States
| | - Nancy Kelley-Loughnane
- Airman Systems Directorate, 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, United States.
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Drachuk I, Harbaugh S, Geryak R, Kaplan DL, Tsukruk VV, Kelley-Loughnane N. Immobilization of Recombinant E. coli Cells in a Bacterial Cellulose–Silk Composite Matrix To Preserve Biological Function. ACS Biomater Sci Eng 2017; 3:2278-2292. [DOI: 10.1021/acsbiomaterials.7b00367] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Irina Drachuk
- UES Inc., 4401 Dayton-Xenia
Road, Dayton, Ohio 45432, United States
- Air Force Research Laboratory, 711th Human Performance Wing, Airmen Systems Directorate, 2510 Fifth Street, Wright-Patterson AFB, Dayton, Ohio 45433, United States
| | - Svetlana Harbaugh
- The Henry M. Jackson Foundation, 6720A Rockledge Drive, Bethesda, Maryland 20817, United States
- Air Force Research Laboratory, 711th Human Performance Wing, Airmen Systems Directorate, 2510 Fifth Street, Wright-Patterson AFB, Dayton, Ohio 45433, United States
| | - Ren Geryak
- School
of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive NW, Atlanta, Georgia 30332, United States
| | - David L. Kaplan
- Department
of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, Massachusetts 02155, United States
| | - Vladimir V. Tsukruk
- School
of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive NW, Atlanta, Georgia 30332, United States
| | - Nancy Kelley-Loughnane
- Air Force Research Laboratory, 711th Human Performance Wing, Airmen Systems Directorate, 2510 Fifth Street, Wright-Patterson AFB, Dayton, Ohio 45433, United States
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17
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Villa JK, Amador P, Janovsky J, Bhuyan A, Saldanha R, Lamkin TJ, Contreras LM. A Genome-Wide Search for Ionizing-Radiation-Responsive Elements in Deinococcus radiodurans Reveals a Regulatory Role for the DNA Gyrase Subunit A Gene's 5' Untranslated Region in the Radiation and Desiccation Response. Appl Environ Microbiol 2017; 83:e00039-17. [PMID: 28411225 PMCID: PMC5452802 DOI: 10.1128/aem.00039-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 04/07/2017] [Indexed: 12/19/2022] Open
Abstract
Tight regulation of gene expression is important for the survival of Deinococcus radiodurans, a model bacterium of extreme stress resistance. Few studies have examined the use of regulatory RNAs as a possible contributing mechanism to ionizing radiation (IR) resistance, despite their proffered efficient and dynamic gene expression regulation under IR stress. This work presents a transcriptome-based approach for the identification of stress-responsive regulatory 5' untranslated region (5'-UTR) elements in D. radiodurans R1 that can be broadly applied to other bacteria. Using this platform and an in vivo fluorescence screen, we uncovered the presence of a radiation-responsive regulatory motif in the 5' UTR of the DNA gyrase subunit A gene. Additional screens under H2O2-induced oxidative stress revealed the specificity of the response of this element to IR stress. Further examination of the sequence revealed a regulatory motif of the radiation and desiccation response (RDR) in the 5' UTR that is necessary for the recovery of D. radiodurans from high doses of IR. Furthermore, we suggest that it is the preservation of predicted RNA structure, in addition to DNA sequence consensus of the motif, that permits this important regulatory ability.IMPORTANCEDeinococcus radiodurans is an extremely stress-resistant bacterium capable of tolerating up to 3,000 times more ionizing radiation than human cells. As an integral part of the stress response mechanism of this organism, we suspect that it maintains stringent control of gene expression. However, understanding of its regulatory pathways remains incomplete to date. Untranslated RNA elements have been demonstrated to play crucial roles in gene regulation throughout bacteria. In this work, we focus on searching for and characterizing responsive RNA elements under radiation stress and propose that multiple levels of gene regulation work simultaneously to enable this organism to efficiently recover from exposure to ionizing radiation. The model we propose serves as a generic template to investigate similar mechanisms of gene regulation under stress that have likely evolved in other bacterial species.
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Affiliation(s)
- Jordan K Villa
- Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, USA
| | - Paul Amador
- Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, USA
| | - Justin Janovsky
- Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, USA
| | - Arijit Bhuyan
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas,USA
| | | | - Thomas J Lamkin
- Air Force Research Laboratory/XPRA Wright-Patterson AFB, Ohio, USA
| | - Lydia M Contreras
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas,USA
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