1
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Kabarkouhi Z, Arjmand S, Ranaei Siadat SO, Shokri B. Cold atmospheric plasma treatment enhances recombinant model protein production in yeast Pichia pastoris. Sci Rep 2023; 13:6797. [PMID: 37100818 PMCID: PMC10133276 DOI: 10.1038/s41598-023-34078-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 04/24/2023] [Indexed: 04/28/2023] Open
Abstract
Cold atmospheric pressure plasma (CAP) has been described as a novel technology with expanding applications in biomedicine and biotechnology. In the present study, we provide a mildly stressful condition using non-lethal doses of CAP (120, 180, and 240 s) and evaluate its potential benefits on the recombinant production of a model protein (enhanced green fluorescent protein (eGFP)) in yeast Pichia pastoris. The measured eGFP fluorescence augmented proportional to CAP exposure time. After 240 s treatment with CAP, the measured fluorescent intensity of culture supernatant (after 72 h) and results of real-time PCR (after 24 h) indicated an 84% and 76% increase in activity and related RNA concentration, respectively. Real-time analysis of a list of genes involved in oxidative stress response revealed a significant and durable improvement in their expression at five h and 24 h following CAP exposure. The improvement of the recombinant model protein production may be partly explained by the impact of the RONS on cellular constituents and altering the expression of specific stress genes. In conclusion, using CAP strategy may be considered a valuable strategy to improve recombinant protein production, and deciphering the molecular background mechanism could be inspiring in the reverse metabolic engineering of host cells.
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Affiliation(s)
- Zeinab Kabarkouhi
- Laser and Plasma Research Institute, Shahid Beheshti University, P.O. Box: 1983969411, Tehran, Iran
| | - Sareh Arjmand
- Protein Research Center, Shahid Beheshti University, P.O. Box: 1983969411, Tehran, Iran
| | | | - Babak Shokri
- Laser and Plasma Research Institute, Shahid Beheshti University, P.O. Box: 1983969411, Tehran, Iran.
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2
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Santos SP, Garcés LFS, Silva FS, Santiago LF, Pinheiro CS, Alcantara-Neves NM, Pacheco LG. Engineering an optimized expression operating unit for improved recombinant protein production in Escherichia coli. Protein Expr Purif 2022; 199:106150. [DOI: 10.1016/j.pep.2022.106150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 10/31/2022]
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3
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Zhao R, Li Z, Sun Y, Ge W, Wang M, Liu H, Xun L, Xia Y. Engineered Escherichia coli Nissle 1917 with urate oxidase and an oxygen-recycling system for hyperuricemia treatment. Gut Microbes 2022; 14:2070391. [PMID: 35491895 PMCID: PMC9067508 DOI: 10.1080/19490976.2022.2070391] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Hyperuricemia is the second most prevalent metabolic disease to human health after diabetes. Only a few clinical drugs are available, and most of them have serious side effects. The human body does not have urate oxidase, and uric acid is secreted via the kidney or the intestine. Reduction through kidney secretion is often the cause of hyperuricemia. We hypothesized that the intestine secretion could be enhanced when a recombinant urate-degrading bacterium was introduced into the gut. We engineered an Escherichia coli Nissle 1917 strain with a plasmid containing a gene cassette that encoded two proteins PucL and PucM for urate metabolism from Bacillus subtilis, the urate importer YgfU and catalase KatG from E. coli, and the bacterial hemoglobin Vhb from Vitreoscilla sp. The recombinant E. coli strain effectively degraded uric acid under hypoxic conditions. A new method to induce hyperuricemia in mice was developed by intravenously injecting uric acid. The engineered Escherichia coli strain significantly lowered the serum uric acid when introduced into the gut or directly injected into the blood vessel. The results support the use of urate-degrading bacteria in the gut to treat hyperuricemia. Direct injecting bacteria into blood vessels to treat metabolic diseases is proof of concept, and it has been tried to treat solid tumors.
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Affiliation(s)
- Rui Zhao
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province, China
| | - Zimai Li
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province, China
| | - Yuqing Sun
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province, China
| | - Wei Ge
- Clinical Laboratory, Qingdao Fuwai Cardiovascular Hospital, Qingdao, Shandong Province, China
| | - Mingyu Wang
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province, China
| | - Huaiwei Liu
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province, China
| | - Luying Xun
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province, China,School of Molecular Biosciences, Washington State University, Pullman, WA, USA
| | - Yongzhen Xia
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province, China,CONTACT Yongzhen Xia State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong Province266237, People’s Republic of China
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4
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MacDonald IC, Seamons TR, Emmons JC, Javdan SB, Deans TL. Enhanced regulation of prokaryotic gene expression by a eukaryotic transcriptional activator. Nat Commun 2021; 12:4109. [PMID: 34226549 PMCID: PMC8257575 DOI: 10.1038/s41467-021-24434-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 06/17/2021] [Indexed: 11/23/2022] Open
Abstract
Expanding the genetic toolbox for prokaryotic synthetic biology is a promising strategy for enhancing the dynamic range of gene expression and enabling new engineered applications for research and biomedicine. Here, we reverse the current trend of moving genetic parts from prokaryotes to eukaryotes and demonstrate that the activating eukaryotic transcription factor QF and its corresponding DNA-binding sequence can be moved to E. coli to introduce transcriptional activation, in addition to tight off states. We further demonstrate that the QF transcription factor can be used in genetic devices that respond to low input levels with robust and sustained output signals. Collectively, we show that eukaryotic gene regulator elements are functional in prokaryotes and establish a versatile and broadly applicable approach for constructing genetic circuits with complex functions. These genetic tools hold the potential to improve biotechnology applications for medical science and research. Expanded toolkits for prokaryotic synthetic biology can enhance the dynamic range of gene expression. Here the authors move the eukaryotic transcription factor QF into E. coli and integrate it into genetic devices.
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Affiliation(s)
- I Cody MacDonald
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Travis R Seamons
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Jonathan C Emmons
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Shwan B Javdan
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Tara L Deans
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA.
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5
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Sánchez-Osorio I, Hernández-Martínez CA, Martínez-Antonio A. Quantitative modeling of the interplay between synthetic gene circuits and host physiology: experiments, results, and prospects. Curr Opin Microbiol 2020; 55:48-56. [DOI: 10.1016/j.mib.2020.02.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 02/06/2020] [Accepted: 02/14/2020] [Indexed: 12/20/2022]
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6
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Kent R, Dixon N. Contemporary Tools for Regulating Gene Expression in Bacteria. Trends Biotechnol 2019; 38:316-333. [PMID: 31679824 DOI: 10.1016/j.tibtech.2019.09.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 09/16/2019] [Accepted: 09/17/2019] [Indexed: 12/14/2022]
Abstract
Insights from novel mechanistic paradigms in gene expression control have led to the development of new gene expression systems for bioproduction, control, and sensing applications. Coupled with a greater understanding of synthetic burden and modern creative biodesign approaches, contemporary bacterial gene expression tools and systems are emerging that permit fine-tuning of expression, enabling greater predictability and maximisation of specific productivity, while minimising deleterious effects upon cell viability. These advances have been achieved by using a plethora of regulatory tools, operating at all levels of the so-called 'central dogma' of molecular biology. In this review, we discuss these gene regulation tools in the context of their design, prototyping, integration into expression systems, and biotechnological application.
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Affiliation(s)
- Ross Kent
- Manchester Institute of Biotechnology and School of Chemistry, University of Manchester, Manchester, UK
| | - Neil Dixon
- Manchester Institute of Biotechnology and School of Chemistry, University of Manchester, Manchester, UK.
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7
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Sadeghian-Rizi T, Ebrahimi A, Moazzen F, Yousefian H, Jahanian-Najafabadi A. Improvement of solubility and yield of recombinant protein expression in E. coli using a two-step system. Res Pharm Sci 2019; 14:400-407. [PMID: 31798656 PMCID: PMC6827196 DOI: 10.4103/1735-5362.268200] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Overexpression of recombinant proteins in Escherichia coli results in inclusion body formation, and consequently decreased production yield and increased production cost. Co-expression of chaperon systems accompanied by recombinant protein is a general method to increase the production yield. However, it has not been successful enough due to imposed intense stress to the host cells. The aim of this study was to balance the rate of protein production and the imposed cellular stresses using a two-step expression system. For this purpose, in the first step, green fluorescent protein (GFP) was expressed as a recombinant protein model under control of the T7-TetO artificial promoter-operator, accompanied by Dnak/J/GrpE chaperon system. Then, in the next step, TetR repressor was activated automatically under the control of the stress promoter ibpAB and suppressed the GFP production after accumulation of inclusion bodies. Thus in this step incorrect folded proteins and inclusion bodies are refolded causing increased yield and solubility of the recombinant protein and restarting GFP expression again. Total GFP, soluble and insoluble GFP fractions, were measured by Synergy H1 multiple reader. Results showed that expression yield and soluble/insoluble ratio of GFP have been increased 5 and 2.5 times using this system in comparison with the single step process, respectively. The efficiency of this system in increasing solubility and production yield of recombinant proteins was confirmed. The two-step system must be evaluated for expression of various proteins to further confirm its applicability in the field of recombinant protein production.
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Affiliation(s)
- Tahereh Sadeghian-Rizi
- Department of Pharmaceutical Biotechnology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran.,Student Research Committee, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
| | - Azade Ebrahimi
- Department of Pharmaceutical Biotechnology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran.,Student Research Committee, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
| | - Fatemeh Moazzen
- Department of Pharmaceutical Biotechnology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
| | - Hesam Yousefian
- Student Research Committee, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
| | - Ali Jahanian-Najafabadi
- Department of Pharmaceutical Biotechnology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, I.R. Iran
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8
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Kelly CL, Harris AWK, Steel H, Hancock EJ, Heap JT, Papachristodoulou A. Synthetic negative feedback circuits using engineered small RNAs. Nucleic Acids Res 2019; 46:9875-9889. [PMID: 30212900 PMCID: PMC6182179 DOI: 10.1093/nar/gky828] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 09/06/2018] [Indexed: 12/13/2022] Open
Abstract
Negative feedback is known to enable biological and man-made systems to perform reliably in the face of uncertainties and disturbances. To date, synthetic biological feedback circuits have primarily relied upon protein-based, transcriptional regulation to control circuit output. Small RNAs (sRNAs) are non-coding RNA molecules that can inhibit translation of target messenger RNAs (mRNAs). In this work, we modelled, built and validated two synthetic negative feedback circuits that use rationally-designed sRNAs for the first time. The first circuit builds upon the well characterised tet-based autorepressor, incorporating an externally-inducible sRNA to tune the effective feedback strength. This allows more precise fine-tuning of the circuit output in contrast to the sigmoidal, steep input–output response of the autorepressor alone. In the second circuit, the output is a transcription factor that induces expression of an sRNA, which inhibits translation of the mRNA encoding the output, creating direct, closed-loop, negative feedback. Analysis of the noise profiles of both circuits showed that the use of sRNAs did not result in large increases in noise. Stochastic and deterministic modelling of both circuits agreed well with experimental data. Finally, simulations using fitted parameters allowed dynamic attributes of each circuit such as response time and disturbance rejection to be investigated.
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Affiliation(s)
- Ciarán L Kelly
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK.,Imperial College Centre for Synthetic Biology, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Andreas W K Harris
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
| | - Harrison Steel
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
| | - Edward J Hancock
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
| | - John T Heap
- Imperial College Centre for Synthetic Biology, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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9
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Bui LM, Geraldi A, Nguyen TT, Lee JH, Lee JY, Cho BK, Kim SC. mRNA Engineering for the Efficient Chaperone-Mediated Co-Translational Folding of Recombinant Proteins in Escherichia coli. Int J Mol Sci 2019; 20:ijms20133163. [PMID: 31261687 PMCID: PMC6651523 DOI: 10.3390/ijms20133163] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 06/18/2019] [Accepted: 06/21/2019] [Indexed: 12/22/2022] Open
Abstract
The production of soluble, functional recombinant proteins by engineered bacterial hosts is challenging. Natural molecular chaperone systems have been used to solubilize various recombinant proteins with limited success. Here, we attempted to facilitate chaperone-mediated folding by directing the molecular chaperones to their protein substrates before the co-translational folding process completed. To achieve this, we either anchored the bacterial chaperone DnaJ to the 3ʹ untranslated region of a target mRNA by fusing with an RNA-binding domain in the chaperone-recruiting mRNA scaffold (CRAS) system, or coupled the expression of DnaJ and a target recombinant protein using the overlapping stop-start codons 5ʹ-TAATG-3ʹ between the two genes in a chaperone-substrate co-localized expression (CLEX) system. By engineering the untranslated and intergenic sequences of the mRNA transcript, bacterial molecular chaperones are spatially constrained to the location of protein translation, expressing selected aggregation-prone proteins in their functionally active, soluble form. Our mRNA engineering methods surpassed the in-vivo solubilization efficiency of the simple DnaJ chaperone co-overexpression method, thus providing more effective tools for producing soluble therapeutic proteins and enzymes.
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Affiliation(s)
- Le Minh Bui
- KAIST Institute for BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- NTT Hi-Tech Institute, Nguyen Tat Thanh University (NTTU), Ho Chi Minh City 700000, Vietnam
| | - Almando Geraldi
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Biology Department, Science and Technology Faculty, Universitas Airlangga Mulyorejo, Surabaya 60115, Indonesia
| | - Thi Thuy Nguyen
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Jun Hyoung Lee
- KAIST Institute for BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Ju Young Lee
- Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Korea
| | - Byung-Kwan Cho
- KAIST Institute for BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
- Intelligent Synthetic Biology Center, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
| | - Sun Chang Kim
- KAIST Institute for BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
- Intelligent Synthetic Biology Center, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
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10
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Mechanistic Models of Inducible Synthetic Circuits for Joint Description of DNA Copy Number, Regulatory Protein Level, and Cell Load. Processes (Basel) 2019. [DOI: 10.3390/pr7030119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Accurate predictive mathematical models are urgently needed in synthetic biology to support the bottom-up design of complex biological systems, minimizing trial-and-error approaches. The majority of models used so far adopt empirical Hill functions to describe activation and repression in exogenously-controlled inducible promoter systems. However, such equations may be poorly predictive in practical situations that are typical in bottom-up design, including changes in promoter copy number, regulatory protein level, and cell load. In this work, we derived novel mechanistic steady-state models of the lux inducible system, used as case study, relying on different assumptions on regulatory protein (LuxR) and cognate promoter (Plux) concentrations, inducer-protein complex formation, and resource usage limitation. We demonstrated that a change in the considered model assumptions can significantly affect circuit output, and preliminary experimental data are in accordance with the simulated activation curves. We finally showed that the models are identifiable a priori (in the analytically tractable cases) and a posteriori, and we determined the specific experiments needed to parametrize them. Although a larger-scale experimental validation is required, in the future the reported models may support synthetic circuits output prediction in practical situations with unprecedented details.
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11
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Pasotti L, Bellato M, Politi N, Casanova M, Zucca S, Cusella De Angelis MG, Magni P. A Synthetic Close-Loop Controller Circuit for the Regulation of an Extracellular Molecule by Engineered Bacteria. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2019; 13:248-258. [PMID: 30489274 DOI: 10.1109/tbcas.2018.2883350] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Feedback control is ubiquitous in biological systems. It can also play a crucial role in the design of synthetic circuits implementing novel functions in living systems, to achieve self-regulation of gene expression, noise reduction, rise time decrease, or adaptive pathway control. Despite in vitro, in vivo, and ex vivo implementations have been successfully reported, the design of biological close-loop systems with quantitatively predictable behavior is still a major challenge. In this work, we tested a model-based bottom-up design of a synthetic close-loop controller in engineered Escherichia coli, aimed to automatically regulate the concentration of an extracellular molecule, N-(3-oxohexanoyl)-L-homoserine lactone (HSL), by rewiring the elements of heterologous quorum sensing/quenching networks. The synthetic controller was successfully constructed and experimentally validated. Relying on mathematical model and experimental characterization of individual regulatory parts and enzymes, we evaluated the predictability of the interconnected system behavior in vivo. The culture was able to reach an HSL steady-state level of 72 nM, accurately predicted by the model, and showed superior capabilities in terms of robustness against cell density variation and disturbance rejection, compared with a corresponding open-loop circuit. This engineering-inspired design approach may be adopted for the implementation of other close-loop circuits for different applications and contribute to decreasing trial-and-error steps.
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12
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Atitey K, Loskot P, Rees P. Inferring distributions from observed mRNA and protein copy counts in genetic circuits. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aaef5c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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13
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Eetemadi A, Tagkopoulos I. Genetic Neural Networks: an artificial neural network architecture for capturing gene expression relationships. Bioinformatics 2018; 35:2226-2234. [DOI: 10.1093/bioinformatics/bty945] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 10/27/2018] [Accepted: 11/16/2018] [Indexed: 01/16/2023] Open
Abstract
Abstract
Motivation
Gene expression prediction is one of the grand challenges in computational biology. The availability of transcriptomics data combined with recent advances in artificial neural networks provide an unprecedented opportunity to create predictive models of gene expression with far reaching applications.
Results
We present the Genetic Neural Network (GNN), an artificial neural network for predicting genome-wide gene expression given gene knockouts and master regulator perturbations. In its core, the GNN maps existing gene regulatory information in its architecture and it uses cell nodes that have been specifically designed to capture the dependencies and non-linear dynamics that exist in gene networks. These two key features make the GNN architecture capable to capture complex relationships without the need of large training datasets. As a result, GNNs were 40% more accurate on average than competing architectures (MLP, RNN, BiRNN) when compared on hundreds of curated and inferred transcription modules. Our results argue that GNNs can become the architecture of choice when building predictors of gene expression from exponentially growing corpus of genome-wide transcriptomics data.
Availability and implementation
https://github.com/IBPA/GNN
Supplementary information
Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Ameen Eetemadi
- Department of Computer Science, University of California, Davis, CA, USA
- Genome Center, University of California, Davis, CA, USA
| | - Ilias Tagkopoulos
- Department of Computer Science, University of California, Davis, CA, USA
- Genome Center, University of California, Davis, CA, USA
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14
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Brown AJ, Gibson SJ, Hatton D, Arnall CL, James DC. Whole synthetic pathway engineering of recombinant protein production. Biotechnol Bioeng 2018; 116:375-387. [DOI: 10.1002/bit.26855] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 09/14/2018] [Accepted: 10/18/2018] [Indexed: 12/13/2022]
Affiliation(s)
- Adam J. Brown
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffield UK
| | | | - Diane Hatton
- Biopharmaceutical Development, MedImmuneCambridge UK
| | - Claire L. Arnall
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffield UK
| | - David C. James
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffield UK
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15
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Ceroni F, Boo A, Furini S, Gorochowski TE, Borkowski O, Ladak YN, Awan AR, Gilbert C, Stan GB, Ellis T. Burden-driven feedback control of gene expression. Nat Methods 2018; 15:387-393. [PMID: 29578536 DOI: 10.1038/nmeth.4635] [Citation(s) in RCA: 205] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 02/01/2018] [Indexed: 12/21/2022]
Abstract
Cells use feedback regulation to ensure robust growth despite fluctuating demands for resources and differing environmental conditions. However, the expression of foreign proteins from engineered constructs is an unnatural burden that cells are not adapted for. Here we combined RNA-seq with an in vivo assay to identify the major transcriptional changes that occur in Escherichia coli when inducible synthetic constructs are expressed. We observed that native promoters related to the heat-shock response activated expression rapidly in response to synthetic expression, regardless of the construct. Using these promoters, we built a dCas9-based feedback-regulation system that automatically adjusts the expression of a synthetic construct in response to burden. Cells equipped with this general-use controller maintained their capacity for native gene expression to ensure robust growth and thus outperformed unregulated cells in terms of protein yield in batch production. This engineered feedback is to our knowledge the first example of a universal, burden-based biomolecular control system and is modular, tunable and portable.
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Affiliation(s)
- Francesca Ceroni
- Department of Chemical Engineering, Imperial College London, London, UK.,Imperial College Centre for Synthetic Biology, Imperial College London, London, UK
| | - Alice Boo
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK.,Department of Bioengineering, Imperial College London, London, UK
| | - Simone Furini
- Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | | | - Olivier Borkowski
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK.,Department of Bioengineering, Imperial College London, London, UK
| | - Yaseen N Ladak
- ITMAT Data Science Group, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, UK
| | - Ali R Awan
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK.,Department of Bioengineering, Imperial College London, London, UK
| | - Charlie Gilbert
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK.,Department of Bioengineering, Imperial College London, London, UK
| | - Guy-Bart Stan
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK.,Department of Bioengineering, Imperial College London, London, UK
| | - Tom Ellis
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK.,Department of Bioengineering, Imperial College London, London, UK
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16
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Potential Applications of the Escherichia coli Heat Shock Response in Synthetic Biology. Trends Biotechnol 2018; 36:186-198. [DOI: 10.1016/j.tibtech.2017.10.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 10/20/2017] [Accepted: 10/20/2017] [Indexed: 01/06/2023]
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17
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Pasotti L, Bellato M, Casanova M, Zucca S, Cusella De Angelis MG, Magni P. Re-using biological devices: a model-aided analysis of interconnected transcriptional cascades designed from the bottom-up. J Biol Eng 2017; 11:50. [PMID: 29255481 PMCID: PMC5729246 DOI: 10.1186/s13036-017-0090-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 11/21/2017] [Indexed: 01/09/2023] Open
Abstract
Background The study of simplified, ad-hoc constructed model systems can help to elucidate if quantitatively characterized biological parts can be effectively re-used in composite circuits to yield predictable functions. Synthetic systems designed from the bottom-up can enable the building of complex interconnected devices via rational approach, supported by mathematical modelling. However, such process is affected by different, usually non-modelled, unpredictability sources, like cell burden. Methods Here, we analyzed a set of synthetic transcriptional cascades in Escherichia coli. We aimed to test the predictive power of a simple Hill function activation/repression model (no-burden model, NBM) and of a recently proposed model, including Hill functions and the modulation of proteins expression by cell load (burden model, BM). To test the bottom-up approach, the circuit collection was divided into training and test sets, used to learn individual component functions and test the predicted output of interconnected circuits, respectively. Results Among the constructed configurations, two test set circuits showed unexpected logic behaviour. Both NBM and BM were able to predict the quantitative output of interconnected devices with expected behaviour, but only the BM was also able to predict the output of one circuit with unexpected behaviour. Moreover, considering training and test set data together, the BM captures circuits output with higher accuracy than the NBM, which is unable to capture the experimental output exhibited by some of the circuits even qualitatively. Finally, resource usage parameters, estimated via BM, guided the successful construction of new corrected variants of the two circuits showing unexpected behaviour. Conclusions Superior descriptive and predictive capabilities were achieved considering resource limitation modelling, but further efforts are needed to improve the accuracy of models for biological engineering. Electronic supplementary material The online version of this article (10.1186/s13036-017-0090-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lorenzo Pasotti
- Laboratory of Bioinformatics, Mathematical Modelling and Synthetic Biology, Department of Electrical, Computer and Biomedical Engineering, University of Pavia, 27100 Pavia, Italy.,Centre for Health Technologies, University of Pavia, 27100 Pavia, Italy
| | - Massimo Bellato
- Laboratory of Bioinformatics, Mathematical Modelling and Synthetic Biology, Department of Electrical, Computer and Biomedical Engineering, University of Pavia, 27100 Pavia, Italy.,Centre for Health Technologies, University of Pavia, 27100 Pavia, Italy
| | - Michela Casanova
- Laboratory of Bioinformatics, Mathematical Modelling and Synthetic Biology, Department of Electrical, Computer and Biomedical Engineering, University of Pavia, 27100 Pavia, Italy.,Centre for Health Technologies, University of Pavia, 27100 Pavia, Italy
| | - Susanna Zucca
- Laboratory of Bioinformatics, Mathematical Modelling and Synthetic Biology, Department of Electrical, Computer and Biomedical Engineering, University of Pavia, 27100 Pavia, Italy.,Centre for Health Technologies, University of Pavia, 27100 Pavia, Italy
| | | | - Paolo Magni
- Laboratory of Bioinformatics, Mathematical Modelling and Synthetic Biology, Department of Electrical, Computer and Biomedical Engineering, University of Pavia, 27100 Pavia, Italy.,Centre for Health Technologies, University of Pavia, 27100 Pavia, Italy
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18
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Improving Fab' fragment retention in an autonucleolytic Escherichia coli strain by swapping periplasmic nuclease translocation signal from OmpA to DsbA. Biotechnol Lett 2017; 39:1865-1873. [PMID: 28875244 PMCID: PMC5674116 DOI: 10.1007/s10529-017-2425-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 08/22/2017] [Indexed: 12/27/2022]
Abstract
Objectives To reduce unwanted Fab’ leakage from an autonucleolytic Escherichia coli strain, which co-expresses OmpA-signalled Staphylococcal nuclease and Fab’ fragment in the periplasm, by substituting in Serratial nuclease and the DsbA periplasm translocation signal as alternatives. Results We attempted to genetically fuse a nuclease from Serratia marcescens to the OmpA signal peptide but plasmid construction failed, possibly due to toxicity of the resultant nuclease. Combining Serratial nuclease to the DsbA signal peptide was successful. The strain co-expressing this nuclease and periplasmic Fab’ grew in complex media and exhibited nuclease activity detectable by DNAse agar plate but its growth in defined medium was retarded. Fab’ coexpression with Staphylococcal nuclease fused to the DsbA signal peptide resulted in cells exhibiting nuclease activity and growth in defined medium. In cultivation to high cell density in a 5 l bioreactor, DsbA-fused Staphylococcal nuclease co-expression coincided with reduced Fab’ leakage relative to the original autonucleolytic Fab’ strain with OmpA-fused staphylococcal nuclease. Conclusions We successfully rescued Fab’ leakage back to acceptable levels and established a basis for future investigation of the linkage between periplasmic nuclease expression and leakage of co-expressed periplasmic Fab’ fragment to the surrounding growth media.
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19
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Lara AR, Jaén KE, Sigala JC, Mühlmann M, Regestein L, Büchs J. Characterization of Endogenous and Reduced Promoters for Oxygen-Limited Processes Using Escherichia coli. ACS Synth Biol 2017; 6:344-356. [PMID: 27715021 DOI: 10.1021/acssynbio.6b00233] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Oxygen limitation can be used as a simple environmental inducer for the expression of target genes. However, there is scarce information on the characteristics of microaerobic promoters potentially useful for cell engineering and synthetic biology applications. Here, we characterized the Vitreoscilla hemoglobin promoter (Pvgb) and a set of microaerobic endogenous promoters in Escherichia coli. Oxygen-limited cultures at different maximum oxygen transfer rates were carried out. The FMN-binding fluorescent protein (FbFP), which is a nonoxygen dependent marker protein, was used as a reporter. Fluorescence and fluorescence emission rates under oxygen-limited conditions were the highest when FbFP was under transcriptional control of PadhE, Ppfl and Pvgb. The lengths of the E. coli endogenous promoters were shortened by 60%, maintaining their key regulatory elements. This resulted in improved promoter activity in most cases, particularly for PadhE, Ppfl and PnarK. Selected promoters were also evaluated using an engineered E. coli strain expressing Vitreoscilla hemoglobin (VHb). The presence of the VHb resulted in a better repression using these promoters under aerobic conditions, and increased the specific growth and fluorescence emission rates under oxygen-limited conditions. These results are useful for the selection of promoters for specific applications and for the design of modified artificial promoters.
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Affiliation(s)
- Alvaro R. Lara
- Departamento
de Procesos y Tecnología, Universidad Autónoma Metropolitana-Cuajimalpa. Av. Vasco de Quiroga 4871, Santa
Fe, C.P. 05348, Mexico City, México
| | - Karim E. Jaén
- Departamento
de Procesos y Tecnología, Universidad Autónoma Metropolitana-Cuajimalpa. Av. Vasco de Quiroga 4871, Santa
Fe, C.P. 05348, Mexico City, México
| | - Juan-Carlos Sigala
- Departamento
de Procesos y Tecnología, Universidad Autónoma Metropolitana-Cuajimalpa. Av. Vasco de Quiroga 4871, Santa
Fe, C.P. 05348, Mexico City, México
| | - Martina Mühlmann
- RWTH Aachen University, AVT - Biochemical Engineering, Worringer Weg 1, 52074 Aachen, Germany
| | - Lars Regestein
- RWTH Aachen University, AVT - Biochemical Engineering, Worringer Weg 1, 52074 Aachen, Germany
| | - Jochen Büchs
- RWTH Aachen University, AVT - Biochemical Engineering, Worringer Weg 1, 52074 Aachen, Germany
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20
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Borkowski O, Ceroni F, Stan GB, Ellis T. Overloaded and stressed: whole-cell considerations for bacterial synthetic biology. Curr Opin Microbiol 2016; 33:123-130. [PMID: 27494248 DOI: 10.1016/j.mib.2016.07.009] [Citation(s) in RCA: 134] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 07/04/2016] [Accepted: 07/06/2016] [Indexed: 12/27/2022]
Abstract
The predictability and robustness of engineered bacteria depend on the many interactions between synthetic constructs and their host cells. Expression from synthetic constructs is an unnatural load for the host that typically reduces growth, triggers stresses and leads to decrease in performance or failure of engineered cells. Work in systems and synthetic biology has now begun to address this through new tools, methods and strategies that characterise and exploit host-construct interactions in bacteria. Focusing on work in E. coli, we review here a selection of the recent developments in this area, highlighting the emerging issues and describing the new solutions that are now making the synthetic biology community consider the cell just as much as they consider the construct.
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Affiliation(s)
- Olivier Borkowski
- Centre for Synthetic Biology and Innovation, Imperial College London, London, UK; Department of Bioengineering, Imperial College London, London, UK
| | - Francesca Ceroni
- Centre for Synthetic Biology and Innovation, Imperial College London, London, UK; Department of Bioengineering, Imperial College London, London, UK
| | - Guy-Bart Stan
- Centre for Synthetic Biology and Innovation, Imperial College London, London, UK; Department of Bioengineering, Imperial College London, London, UK.
| | - Tom Ellis
- Centre for Synthetic Biology and Innovation, Imperial College London, London, UK; Department of Bioengineering, Imperial College London, London, UK.
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21
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Liu X, Hu W, An Z, Bai Z, Dai X, Yang Y. Exploration of cell lysis in a bioreactor using Escherichia coli expressing single-chain variable-domain antibody fragments. ANN MICROBIOL 2016. [DOI: 10.1007/s13213-016-1202-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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22
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Liu H, Lu T. Autonomous production of 1,4-butanediol via a de novo biosynthesis pathway in engineered Escherichia coli. Metab Eng 2015; 29:135-141. [DOI: 10.1016/j.ymben.2015.03.009] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 02/23/2015] [Accepted: 03/10/2015] [Indexed: 10/23/2022]
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23
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Mahalik S, Sharma AK, Mukherjee KJ. Genome engineering for improved recombinant protein expression in Escherichia coli. Microb Cell Fact 2014; 13:177. [PMID: 25523647 PMCID: PMC4300154 DOI: 10.1186/s12934-014-0177-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/05/2014] [Indexed: 01/09/2023] Open
Abstract
A metabolic engineering perspective which views recombinant protein
expression as a multistep pathway allows us to move beyond vector design and
identify the downstream rate limiting steps in expression. In E.coli these are typically at the translational level
and the supply of precursors in the form of energy, amino acids and nucleotides.
Further recombinant protein production triggers a global cellular stress response
which feedback inhibits both growth and product formation. Countering this requires
a system level analysis followed by a rational host cell engineering to sustain
expression for longer time periods. Another strategy to increase protein yields
could be to divert the metabolic flux away from biomass formation and towards
recombinant protein production. This would require a growth stoppage mechanism which
does not affect the metabolic activity of the cell or the transcriptional or
translational efficiencies. Finally cells have to be designed for efficient export
to prevent buildup of proteins inside the cytoplasm and also simplify downstream
processing. The rational and the high throughput strategies that can be used for the
construction of such improved host cell platforms for recombinant protein expression
is the focus of this review.
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Affiliation(s)
- Shubhashree Mahalik
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India.
| | - Ashish K Sharma
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India.
| | - Krishna J Mukherjee
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India.
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24
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Huynh L, Tagkopoulos I. Optimal part and module selection for synthetic gene circuit design automation. ACS Synth Biol 2014; 3:556-64. [PMID: 24933033 DOI: 10.1021/sb400139h] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
An integral challenge in synthetic circuit design is the selection of optimal parts to populate a given circuit topology, so that the resulting circuit behavior best approximates the desired one. In some cases, it is also possible to reuse multipart constructs or modules that have been already built and experimentally characterized. Efficient part and module selection algorithms are essential to systematically search the solution space, and their significance will only increase in the following years due to the projected explosion in part libraries and circuit complexity. Here, we address this problem by introducing a structured abstraction methodology and a dynamic programming-based algorithm that guaranties optimal part selection. In addition, we provide three extensions that are based on symmetry check, information look-ahead and branch-and-bound techniques, to reduce the running time and space requirements. We have evaluated the proposed methodology with a benchmark of 11 circuits, a database of 73 parts and 304 experimentally constructed modules with encouraging results. This work represents a fundamental departure from traditional heuristic-based methods for part and module selection and is a step toward maximizing efficiency in synthetic circuit design and construction.
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Affiliation(s)
- Linh Huynh
- Department of Computer Science
and UC Davis Genome Center University of California Davis, California 95616 United States
| | - Ilias Tagkopoulos
- Department of Computer Science
and UC Davis Genome Center University of California Davis, California 95616 United States
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25
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EcoliOverExpressionDB: A database of recombinant protein overexpression in E. coli. Protein Expr Purif 2014; 95:92-5. [DOI: 10.1016/j.pep.2013.11.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 11/14/2013] [Accepted: 11/25/2013] [Indexed: 11/30/2022]
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26
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Singh AB, Mukherjee KJ. Supplementation of substrate uptake gene enhances the expression of rhIFN-β in high cell density fed-batch cultures of Escherichia coli. Mol Biotechnol 2013. [PMID: 23180218 DOI: 10.1007/s12033-012-9611-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Over-expression of recombinant proteins in Escherichia coli triggers a metabolic stress response which causes a sharp decline in both growth and product formation rates post induction. We identified a key down-regulated substrate utilization gene, glycerol kinase (glpK), whose up-regulation could help alleviate this stress response. In a proof of principal study conducted in shake flask cultures, the glpK gene under the "ara" promoter in a pPROLar.A122 vector was co-transformed along with the recombinant interferon-β (rhIFN-β) gene in a pET22b vector into E. coli BL-21(DE3) cells. Co-expression of glpK improved the expression levels of rhIFN-β in glycerol containing medium, while no such gain was observed in medium without glycerol. This study was extended to high cell density fed-batch cultures where exponential feeding of complex substrates was done to increase biomass and hence product titers. For this we first constructed a modified E. coli strain BL-21(glpK (+)) where the glpK gene was inserted downstream of the ibpA promoter in the host chromosome. There was a significant improvement in growth as well as expression levels of rhIFN-β in this modified strain when the feed medium contained high glycerol. A final product concentration of 4.8 g/l of rhIFN-β was obtained with the modified strain which was 35 % higher than the control.
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Affiliation(s)
- Anuradha B Singh
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.
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27
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Iyer S, Karig DK, Norred SE, Simpson ML, Doktycz MJ. Multi-input regulation and logic with T7 promoters in cells and cell-free systems. PLoS One 2013; 8:e78442. [PMID: 24194933 PMCID: PMC3806817 DOI: 10.1371/journal.pone.0078442] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 09/10/2013] [Indexed: 11/21/2022] Open
Abstract
Engineered gene circuits offer an opportunity to harness biological systems for biotechnological and biomedical applications. However, reliance on native host promoters for the construction of circuit elements, such as logic gates, can make the implementation of predictable, independently functioning circuits difficult. In contrast, T7 promoters offer a simple orthogonal expression system for use in a variety of cellular backgrounds and even in cell-free systems. Here we develop a T7 promoter system that can be regulated by two different transcriptional repressors for the construction of a logic gate that functions in cells and in cell-free systems. We first present LacI repressible T7lacO promoters that are regulated from a distal lac operator site for repression. We next explore the positioning of a tet operator site within the T7lacO framework to create T7 promoters that respond to tet and lac repressors and realize an IMPLIES gate. Finally, we demonstrate that these dual input sensitive promoters function in an E. coli cell-free protein expression system. Our results expand the utility of T7 promoters in cell based as well as cell-free synthetic biology applications.
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Affiliation(s)
- Sukanya Iyer
- Graduate Program in Genome Science and Technology, University of Tennessee, Knoxville, Knoxville, Tennessee, United States of America
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - David K. Karig
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - S. Elizabeth Norred
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Knoxville, Tennessee, United States of America
| | - Michael L. Simpson
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Knoxville, Tennessee, United States of America
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Knoxville, Tennessee, United States of America
| | - Mitchel J. Doktycz
- Graduate Program in Genome Science and Technology, University of Tennessee, Knoxville, Knoxville, Tennessee, United States of America
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- * E-mail:
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28
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Gatti-Lafranconi P, Dijkman WP, Devenish SRA, Hollfelder F. A single mutation in the core domain of the lac repressor reduces leakiness. Microb Cell Fact 2013; 12:67. [PMID: 23834731 PMCID: PMC3722110 DOI: 10.1186/1475-2859-12-67] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 06/29/2013] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND The lac operon provides cells with the ability to switch from glucose to lactose metabolism precisely when necessary. This metabolic switch is mediated by the lac repressor (LacI), which in the absence of lactose binds to the operator DNA sequence to inhibit transcription. Allosteric rearrangements triggered by binding of the lactose isomer allolactose to the core domain of the repressor impede DNA binding and lift repression. In Nature, the ability to detect and respond to environmental conditions comes at the cost of the encoded enzymes being constitutively expressed at low levels. The readily-switched regulation provided by LacI has resulted in its widespread use for protein overexpression, and its applications in molecular biology represent early examples of synthetic biology. However, the leakiness of LacI that is essential for the natural function of the lac operon leads to an increased energetic burden, and potentially toxicity, in heterologous protein production. RESULTS Analysis of the features that confer promiscuity to the inducer-binding site of LacI identified tryptophan 220 as a target for saturation mutagenesis. We found that phenylalanine (similarly to tryptophan) affords a functional repressor that is still responsive to IPTG. Characterisation of the W220F mutant, LacIWF, by measuring the time dependence of GFP production at different IPTG concentrations and at various incubation temperatures showed a 10-fold reduction in leakiness and no decrease in GFP production. Cells harbouring a cytotoxic protein under regulatory control of LacIWF showed no decrease in viability in the early phases of cell growth. Changes in responsiveness to IPTG observed in vivo are supported by the thermal shift assay behaviour of purified LacIWF with IPTG and operator DNA. CONCLUSIONS In LacI, long-range communications are responsible for the transmission of the signal from the inducer binding site to the DNA binding domain and our results are consistent with the involvement of position 220 in modulating these. The mutation of this single tryptophan residue to phenylalanine generated an enhanced repressor with a 10-fold decrease in leakiness. By minimising the energetic burden and cytotoxicity caused by leakiness, LacIWF constitutes a useful switch for protein overproduction and synthetic biology.
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Affiliation(s)
| | - Willem P Dijkman
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Sean RA Devenish
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Florian Hollfelder
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
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29
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Yao AI, Fenton TA, Owsley K, Seitzer P, Larsen DJ, Sit H, Lau J, Nair A, Tantiongloc J, Tagkopoulos I, Facciotti MT. Promoter element arising from the fusion of standard BioBrick parts. ACS Synth Biol 2013; 2:111-20. [PMID: 23656374 DOI: 10.1021/sb300114d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
We characterize the appearance of a constitutive promoter element in the commonly used cI repressor-encoding BioBrick BBa_C0051. We have termed this promoter element pKAT. Full pKAT activity is created by the ordered assembly of sequences in BBa_C0051 downstream of the cI gene encoding the 11 amino acid LVA proteolytic degradation tag, a BioBrick standard double-TAA stop codon, a genetic barcode, and part of the RFC10 SpeI-XbaI BioBrick scar. Placing BBa_C0051 or other pKAT containing parts upstream of other functional RNA coding elements in a polycistronic context may therefore lead to the unintended transcription of the downstream elements. The frequent reuse of pKAT or pKAT-like containing basic parts in the Registry of Biological Parts has resulted in approximately 5% of registry parts encoding at least one instance of a predicted pKAT promoter located directly upstream of a ribosome binding site and ATG start codon. This example highlights that even seemingly simple modifications of a part's sequence (in this case addition of degradation tags and barcodes) may be sufficient to unexpectedly change the contextual behavior of a part and reaffirms the inherent challenge in carefully characterizing the behavior of standardized biological parts across a broad range of reasonable use scenarios.
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Affiliation(s)
| | | | | | | | - David J. Larsen
- Cellular and Molecular Biology
Program, University of Michigan, 1011 North
University Avenue, Ann Arbor, Michigan 48109, United States
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30
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Kiel C, Serrano L. Structural Data in Synthetic Biology Approaches for Studying General Design Principles of Cellular Signaling Networks. Structure 2012; 20:1806-13. [DOI: 10.1016/j.str.2012.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 10/09/2012] [Accepted: 10/10/2012] [Indexed: 12/13/2022]
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31
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Tagkopoulos I. Microbial factories under control: auto-regulatory control through engineered stress-induced feedback. Bioengineered 2012; 4:5-8. [PMID: 22922761 DOI: 10.4161/bioe.21935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Severely stressed, with their resources depleted, and their cellular machinery working beyond capacity, the host cells that are used for heterologous protein production have no option but to activate their stress response pathways in order to mitigate the accumulating effects of expressing a foreign, possibly toxic, protein at vast quantities. The result is lower protein yield and quality, with many products being misfolded or part of inclusion bodies that need further processing. Recently, new techniques aim to shift the control of protein production from humans to cells and empower the latter to regulate the production process, thus leading to increased protein quality. Herein we provide a perspective on how integrative synthetic biology can be applied to traditional biotechnological applications with potentially transformative results.
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Affiliation(s)
- Ilias Tagkopoulos
- University of California, Davis, Computer Science and UC Davis Genome Cente, Davis, CA USA.
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