1
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Petushkov I, Feklistov A, Kulbachinskiy A. Highly specific aptamer trap for extremophilic RNA polymerases. Biochimie 2024; 225:99-105. [PMID: 38759834 DOI: 10.1016/j.biochi.2024.05.014] [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: 02/29/2024] [Revised: 05/03/2024] [Accepted: 05/15/2024] [Indexed: 05/19/2024]
Abstract
During transcription initiation, the holoenzyme of bacterial RNA polymerase (RNAP) specifically recognizes promoters using a dedicated σ factor. During transcription elongation, the core enzyme of RNAP interacts with nucleic acids mainly nonspecifically, by stably locking the DNA template and RNA transcript inside the main cleft. Here, we present a synthetic DNA aptamer that is specifically recognized by both core and holoenzyme RNAPs from extremophilic bacteria of the Deinococcus-Thermus phylum. The aptamer binds RNAP with subnanomolar affinities, forming extremely stable complexes even at high ionic strength conditions, blocks RNAP interactions with the DNA template and inhibits RNAP activity during transcription elongation. We propose that the aptamer binds at a conserved site within the downstream DNA-binding cleft of RNAP and traps it in an inactive conformation. The aptamer can potentially be used for structural studies to reveal RNAP conformational states, affinity binding of RNAP and associated factors, and screening of transcriptional inhibitors.
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Affiliation(s)
- Ivan Petushkov
- National Research Center "Kurchatov Institute", Moscow, 123182, Kurchatov Sq. 2, Russia; Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia
| | - Andrey Feklistov
- Department of Structural Biology, Stanford School of Medicine, Stanford, CA, 94305, USA
| | - Andrey Kulbachinskiy
- National Research Center "Kurchatov Institute", Moscow, 123182, Kurchatov Sq. 2, Russia; Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
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2
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Plasmids for Controlled and Tunable High-Level Expression in E. coli. Appl Environ Microbiol 2022; 88:e0093922. [PMID: 36342148 PMCID: PMC9680613 DOI: 10.1128/aem.00939-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Genetic systems for protein overexpression are required tools in microbiological and biochemical research. Ideally, these systems include standardized genetic parts with predictable behavior, enabling the construction of stable expression systems in the host organism.
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3
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Li Z, Wang J, Willner I. Autoinhibited transient, gated, and cascaded dynamic transcription of RNAs. SCIENCE ADVANCES 2022; 8:eabq5947. [PMID: 35977022 PMCID: PMC9385147 DOI: 10.1126/sciadv.abq5947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/05/2022] [Indexed: 06/15/2023]
Abstract
Following transient spatiotemporal misregulation of gene expression programs by native transcription machineries, we introduce a versatile biomimetic concept to design transient dynamic transcription machineries, revealing gated and cascaded temporal transcription of RNAs. The concept is based on the engineering of the reaction module consisting of malachite green (MG) and/or DFHBI {(5Z)-5-[(3,5-difluoro-4-hydroxyphenyl)methylene]-3,5-dihydro-2,3-dimethyl-4H-imidazol-4-one} DNA scaffolds, T7 RNA polymerase (RNAP) aptamer transcription scaffold, and the inhibited T7 RNAP-aptamer complex. In the presence of the counter RNAP aptamer strand and ribonucleoside triphosphates, the triggered activation of the three transcription scaffolds are activated, leading to the transcription of the MG and/or DFHBI RNA aptamer and to the transcription of the RNAP aptamer acting as an autoinhibitor that leads to the transient temporal, dissipative, and blockage of all transcription. By appropriate design of the transcription scaffolds and the inhibitors/coupler, transient gated and cascaded transcription processes are demonstrated, and a bimodal transcription module synthesizing a transient operating ribozyme is introduced.
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4
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Yoo H, Lee JY, Park KS, Oh SS. Lead-start isothermal polymerase amplification controlled by DNAzymatic switches. NANOSCALE 2022; 14:7828-7836. [PMID: 35583083 DOI: 10.1039/d1nr07894a] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
As DNA polymerases are even active at ambient temperature, there is inevitable non-specific amplification; to avoid the undesired amplification of analytes, a heat activation-based polymerase chain reaction (PCR), called hot-start PCR, is widely used to be highly precise and quantitative in detection. Unlike thermocycling amplification, isothermal amplification, compatible for point-of-care (PoC) tests, cannot be benefited by the heat-activation technique, making the method qualitative rather than quantitative. In this work, we newly developed a lead ion (Pb2+) activation technique, called lead-start isothermal amplification, allowing on-demand activation or deactivation of DNA polymerases at room temperature. We systematically correlated the DNA polymerase inhibition by the TQ30 aptamer with Pb2+-responsive strand cleavage by the GR5 DNAzyme, and relying on the type of interconnectors, Pb2+ successfully served as an initiator or a terminator of isothermal DNA amplification. Our lead-start isothermal amplification was exceptionally Pb2+-specific, dramatically increasing the enzymatic activity of DNA polymerase (>25 times) only by Pb2+ introduction. Despite one-by-one sample preparation, a number of reactions can begin and end at the same time, sharing the identical amplification conditions, and thereby allowing their quantitative analysis and comparison. Using a portable UV lamp and a smartphone camera, we also succeeded in quantifying the amounts of clinically important and human papillomavirus type 16 genes in human serum and SARS-CoV-2's nucleocapsid genes in human serum and saliva, and the limit of detection was as low as 0.1 nM, highly applicable for actual PoC tests in the field with no purification process.
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Affiliation(s)
- Hyebin Yoo
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, South Korea.
| | - Ju Young Lee
- Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan, 44429, South Korea
| | - Ki Soo Park
- Department of Biological Engineering, Konkuk University, Seoul, 05029, South Korea.
| | - Seung Soo Oh
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, South Korea.
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5
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Climent-Catala A, Ouldridge TE, Stan GBV, Bae W. Building an RNA-Based Toggle Switch Using Inhibitory RNA Aptamers. ACS Synth Biol 2022; 11:562-569. [PMID: 35133150 PMCID: PMC9007568 DOI: 10.1021/acssynbio.1c00580] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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Synthetic
RNA systems offer unique advantages such as faster response,
increased specificity, and programmability compared to conventional
protein-based networks. Here, we demonstrate an in vitro RNA-based toggle switch using RNA aptamers capable of inhibiting
the transcriptional activity of T7 or SP6 RNA polymerases. The activities
of both polymerases are monitored simultaneously by using Broccoli
and malachite green light-up aptamer systems. In our toggle switch,
a T7 promoter drives the expression of SP6 inhibitory aptamers, and
an SP6 promoter expresses T7 inhibitory aptamers. We show that the
two distinct states originating from the mutual inhibition of aptamers
can be toggled by adding DNA sequences to sequester the RNA inhibitory
aptamers. Finally, we assessed our RNA-based toggle switch in degrading
conditions by introducing controlled degradation of RNAs using a mix
of RNases. Our results demonstrate that the RNA-based toggle switch
could be used as a control element for nucleic acid networks in synthetic
biology applications.
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Affiliation(s)
- Alicia Climent-Catala
- Imperial College Centre for Synthetic Biology, London, SW7 2AZ, U.K
- Department of Chemistry, Imperial College London, London, SW7 2AZ, U.K
| | - Thomas E. Ouldridge
- Imperial College Centre for Synthetic Biology, London, SW7 2AZ, U.K
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, U.K
| | - Guy-Bart V. Stan
- Imperial College Centre for Synthetic Biology, London, SW7 2AZ, U.K
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, U.K
| | - Wooli Bae
- Imperial College Centre for Synthetic Biology, London, SW7 2AZ, U.K
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, U.K
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6
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Kim J, Quijano JF, Kim J, Yeung E, Murray RM. Synthetic logic circuits using RNA aptamer against T7 RNA polymerase. Biotechnol J 2021; 17:e2000449. [PMID: 33813787 DOI: 10.1002/biot.202000449] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 03/05/2021] [Accepted: 03/30/2021] [Indexed: 12/23/2022]
Abstract
Recent advances in nucleic acids engineering introduced several RNA-based regulatory components for synthetic gene circuits, expanding the toolsets to engineer organisms. In this work, we designed genetic circuits implementing an RNA aptamer previously described to have the capability of binding to the T7 RNA polymerase and inhibiting its activity in vitro. We first demonstrated the utility of the RNA aptamer in combination with programmable synthetic transcription networks in vitro. As a step to quickly assess the feasibility of aptamer functions in vivo, we tested the aptamer and its sequence variants in the cell-free expression system, verifying the aptamer functionality in the cell-free testbed. The expression of aptamer in E. coli demonstrated control over GFP expression driven by T7 RNA polymerase, indicating its ability to serve as building blocks for logic circuits and transcriptional cascades. This work elucidates the potential of T7 RNA polymerase aptamer as regulators for synthetic biological circuits and metabolic engineering.
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Affiliation(s)
- Jongmin Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Republic of Korea.,Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - Juan F Quijano
- Department of Biological Sciences, Columbia University, New York, New York, USA
| | - Jeongwon Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, Republic of Korea
| | - Enoch Yeung
- Department of Control and Dynamical Systems, California Institute of Technology, Pasadena, California, USA.,Department of Mechanical Engineering, University of California, Santa Barbara, California, USA
| | - Richard M Murray
- Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA.,Department of Control and Dynamical Systems, California Institute of Technology, Pasadena, California, USA
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7
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Cuba Samaniego C, Franco E. Ultrasensitive molecular controllers for quasi-integral feedback. Cell Syst 2021; 12:272-288.e3. [PMID: 33539724 DOI: 10.1016/j.cels.2021.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 09/22/2020] [Accepted: 01/11/2021] [Indexed: 12/24/2022]
Abstract
Feedback control has enabled the success of automated technologies by mitigating the effects of variability, unknown disturbances, and noise. While it is known that biological feedback loops reduce the impact of noise and help shape kinetic responses, many questions remain about how to design molecular integral controllers. Here, we propose a modular strategy to build molecular quasi-integral feedback controllers, which involves following two design principles. The first principle is to utilize an ultrasensitive response, which determines the gain of the controller and influences the steady-state error. The second is to use a tunable threshold of the ultrasensitive response, which determines the equilibrium point of the system. We describe a reaction network, named brink controller, that satisfies these conditions by combining molecular sequestration and an activation/deactivation cycle. With computational models, we examine potential biological implementations of brink controllers, and we illustrate different example applications.
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Affiliation(s)
- Christian Cuba Samaniego
- Mechanical and Aerospace Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Elisa Franco
- Mechanical and Aerospace Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California at Los Angeles, Los Angeles, CA 90095, USA; Bioengineering, University of California at Los Angeles, Los Angeles, CA 90095, USA; Mechanical Engineering, University of California at Riverside, Riverside, CA 92521, USA.
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8
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Ospina-Villa JD, Cisneros-Sarabia A, Sánchez-Jiménez MM, Marchat LA. Current Advances in the Development of Diagnostic Tests based on Aptamers in Parasitology: A Systematic Review. Pharmaceutics 2020; 12:pharmaceutics12111046. [PMID: 33142793 PMCID: PMC7693570 DOI: 10.3390/pharmaceutics12111046] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/25/2020] [Accepted: 10/27/2020] [Indexed: 02/07/2023] Open
Abstract
Aptamers are single-stranded DNA or RNA sequences of 20–80 nucleotides that interact with different targets such as: proteins, ions, viruses, or toxins, through non-covalent interactions and their unique three-dimensional conformation. They are obtained in vitro by the systematic evolution of ligands by exponential enrichment (SELEX). Because of their ability of target recognition with high specificity and affinity, aptamers are usually compared to antibodies. However, they present many advantages that make them promising molecules for the development of new methods for the diagnosis and treatment of human diseases. In medical parasitology, aptamers also represent an attractive alternative for the implementation of new parasite detection methods, easy to apply in endemic regions. The aim of this study was to describe the current advances in the development of diagnostic tests based on aptamers in parasitology. For this, articles were selected following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, with specific inclusion and exclusion criteria. The 26 resulting articles deal with the use of aptamers for the detection of six important protozoa that affect human health. This systematic review clearly demonstrates the specificity, sensitivity and selectivity of aptamers and aptasensors, that certainly will soon become standard methods in medical parasitology.
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Affiliation(s)
- Juan David Ospina-Villa
- Instituto Colombiano de Medicina Tropical, Universidad CES, Sabaneta CP 055450, Antioquia, Colombia; (J.D.O.-V.); (M.M.S.-J.)
| | - Alondra Cisneros-Sarabia
- ENMH, Instituto Politécnico Nacional, Guillermo Massieu Helguera 239, Fracc. La Escalera, Ticomán, Del. Gustavo A. Madero, Mexico City CP 07320, Mexico;
| | - Miryan Margot Sánchez-Jiménez
- Instituto Colombiano de Medicina Tropical, Universidad CES, Sabaneta CP 055450, Antioquia, Colombia; (J.D.O.-V.); (M.M.S.-J.)
| | - Laurence A. Marchat
- ENMH, Instituto Politécnico Nacional, Guillermo Massieu Helguera 239, Fracc. La Escalera, Ticomán, Del. Gustavo A. Madero, Mexico City CP 07320, Mexico;
- Correspondence: ; Tel.: +52-55-5729-6300 (ext. 55543)
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9
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Hu Y, Wang Z, Chen Z, Pan L. Switching the activity of Taq polymerase using clamp-like triplex aptamer structure. Nucleic Acids Res 2020; 48:8591-8600. [PMID: 32644133 PMCID: PMC7470972 DOI: 10.1093/nar/gkaa581] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/31/2020] [Accepted: 06/27/2020] [Indexed: 01/22/2023] Open
Abstract
In nature, allostery is the principal approach for regulating cellular processes and pathways. Inspired by nature, structure-switching aptamer-based nanodevices are widely used in artificial biotechnologies. However, the canonical aptamer structures in the nanodevices usually adopt a duplex form, which limits the flexibility and controllability. Here, a new regulating strategy based on a clamp-like triplex aptamer structure (CLTAS) was proposed for switching DNA polymerase activity via conformational changes. It was demonstrated that the polymerase activity could be regulated by either adjusting structure parameters or dynamic reactions including strand displacement or enzymatic digestion. Compared with the duplex aptamer structure, the CLTAS possesses programmability, excellent affinity and high discrimination efficiency. The CLTAS was successfully applied to distinguish single-base mismatches. The strategy expands the application scope of triplex structures and shows potential in biosensing and programmable nanomachines.
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Affiliation(s)
- Yingxin Hu
- Key Laboratory of Image Information Processing and Intelligent Control of Education Ministry of China, School of Artificial Intelligence and Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
- College of Information Science and Technology, Shijiazhuang Tiedao University, Shijiazhuang, Hebei 050043, China
| | - Zhiyu Wang
- Key Laboratory of Image Information Processing and Intelligent Control of Education Ministry of China, School of Artificial Intelligence and Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Zhekun Chen
- Key Laboratory of Image Information Processing and Intelligent Control of Education Ministry of China, School of Artificial Intelligence and Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Linqiang Pan
- To whom correspondence should be addressed. Tel: +86 27 87556070; Fax: +86 27 87543130;
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10
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Agarwal S, Franco E. Enzyme-Driven Assembly and Disassembly of Hybrid DNA-RNA Nanotubes. J Am Chem Soc 2019; 141:7831-7841. [PMID: 31042366 DOI: 10.1021/jacs.9b01550] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Living cells have the ability to control the dynamics of responsive assemblies such as the cytoskeleton by temporally activating and deactivating inert precursors. While DNA nanotechnology has demonstrated many synthetic supramolecular assemblies that rival biological ones in size and complexity, dynamic control of their formation is still challenging. Taking inspiration from nature, we developed a DNA-RNA nanotube system whose assembly and disassembly can be temporally controlled at physiological temperature using transcriptional programs. Nanotubes assemble when inert DNA monomers are directly and selectively activated by RNA molecules that become embedded in the structure, producing hybrid DNA-RNA assemblies. The reactions and molecular programs controlling nanotube formation are fueled by enzymes that produce or degrade RNA. We show that the speed of assembly and disassembly of the nanotubes can be controlled by tuning various reaction parameters in the transcriptional programs. We anticipate that these hybrid structures are a starting point to build integrated biological circuits and functional scaffolds inside natural and artificial cells, where RNA produced by gene networks could fuel the assembly of nucleic acid components on demand.
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Affiliation(s)
- Siddharth Agarwal
- Department of Mechanical Engineering , University of California at Riverside , Riverside , California 90095 , United States
| | - Elisa Franco
- Department of Mechanical Engineering , University of California at Riverside , Riverside , California 90095 , United States
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11
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Promoter RNA sequencing (PRSeq) for the massive and quantitative promoter analysis in vitro. Sci Rep 2019; 9:3118. [PMID: 30816266 PMCID: PMC6395800 DOI: 10.1038/s41598-019-39892-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 02/01/2019] [Indexed: 11/08/2022] Open
Abstract
Analysis of promoter strength and specificity is important for understanding and engineering gene regulation. Here, we report an in vitro promoter analysis method that can achieve both massiveness and quantitativeness. In this approach, a pool of single-stranded DNA with a partially randomized promoter sequence to be analyzed is chemically synthesized. Through enzymatic reactions, the randomized sequence will be copied to the downstream region, resulting in a template DNA pool that carries its own promoter information on its transcribed region. After in vitro transcription of the DNA pool with an RNA polymerase of interest, the sequences of the resulting transcripts will be analyzed. Since the promoter strength linearly correlates to the copy number of transcript, the strength of each promoter sequence can be evaluated. A model experiment of T7 promoter variants demonstrated the quantitativeness of the method, and the method was applied for the analysis of the promoter of cyanophage Syn5 RNA polymerase. This method provides a powerful approach for analyzing the complexity of promoter specificity and discrimination for highly abundant and often redundant alternative sigma factors such as the extracellular function (ECF) sigma factors.
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12
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Wang W, Li Y, Wang Y, Shi C, Li C, Li Q, Linhardt RJ. Bacteriophage T7 transcription system: an enabling tool in synthetic biology. Biotechnol Adv 2018; 36:2129-2137. [DOI: 10.1016/j.biotechadv.2018.10.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/30/2018] [Accepted: 10/01/2018] [Indexed: 10/28/2022]
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13
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Ohuchi S, Suess B. Altered stoichiometry of an evolved RNA aptamer. RNA (NEW YORK, N.Y.) 2018; 24:480-485. [PMID: 29284756 PMCID: PMC5855949 DOI: 10.1261/rna.063610.117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 12/21/2017] [Indexed: 06/07/2023]
Abstract
Inhibitory aptamers against a protein are promising as antagonistic reagents and repressive genetic components. Typically, improvement of such aptamers is achieved by acquiring higher binding affinity. Here, we report an alternative mechanism for the improvement of aptamer activity. Recently, we reported a transcriptional activator based on an inhibitory RNA aptamer against lambda cI repressor. We improved the aptamer through in vitro selection (SELEX) from a randomly mutagenized aptamer pool, followed by in vivo screening and truncation. Biochemical analyses indicated that the activity improvement was achieved by alteration of the complex formation stoichiometry, rather than by higher affinity or expression. Our results suggest an alternative strategy for improving aptamer activity.
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Affiliation(s)
- Shoji Ohuchi
- Department of Biology, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Beatrix Suess
- Department of Biology, Technische Universität Darmstadt, 64287 Darmstadt, Germany
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14
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Abstract
Life is sustained by a variety of cyclic processes such as cell division, muscle contraction, and neuron firing. The periodic signals powering these processes often direct a variety of other downstream systems, which operate at different time scales and must have the capacity to divide or multiply the period of the master clock. Period modulation is also an important challenge in synthetic molecular systems, where slow and fast components may have to be coordinated simultaneously by a single oscillator whose frequency is often difficult to tune. Circuits that can multiply the period of a clock signal (frequency dividers), such as binary counters and flip-flops, are commonly encountered in electronic systems, but design principles to obtain similar devices in biological systems are still unclear. We take inspiration from the architecture of electronic flip-flops, and we propose to build biomolecular period-doubling networks by combining a bistable switch with negative feedback modules that preprocess the circuit inputs. We identify a network motif and we show it can be "realized" using different biomolecular components; two of the realizations we propose rely on transcriptional gene networks and one on nucleic acid strand displacement systems. We examine the capacity of each realization to perform period-doubling by studying how bistability of the motif is affected by the presence of the input; for this purpose, we employ mathematical tools from algebraic geometry that provide us with valuable insights on the input/output behavior as a function of the realization parameters. We show that transcriptional network realizations operate correctly also in a stochastic regime when processing oscillations from the repressilator, a canonical synthetic in vivo oscillator. Finally, we compare the performance of different realizations in a range of realistic parameters via numerical sensitivity analysis of the period-doubling region, computed with respect to the input period and amplitude. Our mathematical and computational analysis suggests that the motif we propose is generally robust with respect to specific implementation details: functionally equivalent circuits can be built as long as the species-interaction topology is respected. This indicates that experimental construction of the circuit is possible with a variety of components within the rapidly expanding libraries available in synthetic biology.
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Affiliation(s)
- Christian Cuba Samaniego
- Mechanical Engineering, University of California at Riverside , Riverside, California 92521, United States
| | - Elisa Franco
- Mechanical Engineering, University of California at Riverside , Riverside, California 92521, United States
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15
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Lloyd J, Tran CH, Wadhwani K, Cuba Samaniego C, Subramanian HKK, Franco E. Dynamic Control of Aptamer-Ligand Activity Using Strand Displacement Reactions. ACS Synth Biol 2018; 7:30-37. [PMID: 29028334 DOI: 10.1021/acssynbio.7b00277] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nucleic acid aptamers are an expandable toolkit of sensors and regulators. To employ aptamer regulators within nonequilibrium molecular networks, the aptamer-ligand interactions should be tunable over time, so that functions within a given system can be activated or suppressed on demand. This is accomplished through complementary sequences to aptamers, which achieve programmable aptamer-ligand dissociation by displacing the aptamer from the ligand. We demonstrate the effectiveness of our simple approach on light-up aptamers as well as on aptamers inhibiting viral RNA polymerases, dynamically controlling the functionality of the aptamer-ligand complex. Mathematical models allow us to obtain estimates for the aptamer displacement kinetics. Our results suggest that aptamers, paired with their complement, could be used to build dynamic nucleic acid networks with direct control over a variety of aptamer-controllable enzymes and their downstream pathways.
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Affiliation(s)
- Jonathan Lloyd
- Bioengineering, University of California at Riverside, Riverside, California 92521, United States
| | - Claire H. Tran
- Bioengineering, University of California at Riverside, Riverside, California 92521, United States
| | - Krishen Wadhwani
- Bioengineering, University of California at Riverside, Riverside, California 92521, United States
| | - Christian Cuba Samaniego
- Mechanical
Engineering, University of California at Riverside, Riverside, California 92521, United States
| | - Hari K. K. Subramanian
- Mechanical
Engineering, University of California at Riverside, Riverside, California 92521, United States
| | - Elisa Franco
- Mechanical
Engineering, University of California at Riverside, Riverside, California 92521, United States
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16
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An aptamer-based biosensor for detection of doxorubicin by electrochemical impedance spectroscopy. Anal Bioanal Chem 2017; 410:1453-1462. [PMID: 29199352 DOI: 10.1007/s00216-017-0786-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/31/2017] [Accepted: 11/24/2017] [Indexed: 12/18/2022]
Abstract
An aptamer-based biosensor was developed for the detection of doxorubicin using electrochemical impedance spectroscopy. Doxorubicin and its 14-dehydroxylated version daunorubicin are anthracyclines often used in cancer treatment. Due to their mutagenic and cardiotoxic effects, detection in groundwater is desirable. We developed a biosensor using the daunorubicin-binding aptamer as biological recognition element. The aptamer was successfully co-immobilized with mercaptohexanol on gold and a density of 1.3*1013 ± 2.4*1012 aptamer molecules per cm2 was achieved. The binding of doxorubicin to the immobilized aptamer was detected by electrochemical impedance spectroscopy. The principle is based on the inhibition of electron transfer between electrode and ferro-/ferricyanide in solution caused by the binding of doxorubicin to the immobilized aptamer. A linear relationship between the charge transfer resistance (R ct ) and the doxorubicin concentration was obtained over the range of 31 nM to 125 nM doxorubicin, with an apparent binding constant of 64 nM and a detection limit of 28 nM. With the advantages of high sensitivity, selectivity, and simple sensor construction, this method shows a high potential of impedimetric aptasensors in environmental monitoring. Graphical abstract Measurement chamber and immobilization principle for the detection of doxorubicin by electrochemical impedance spectroscopy.
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17
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Identification of RNA aptamers against recombinant proteins with a hexa-histidine tag. Methods Mol Biol 2014; 1111:41-56. [PMID: 24549611 DOI: 10.1007/978-1-62703-755-6_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Artificial riboswitches that respond to the concentrations of intracellular proteins are a promising tool with a variety of applications. They can be designed and engineered using existing RNA aptamers that target proteins. Aptamers are generated via an iterative selection-amplification process, known as systematic evolution of ligands by exponential enrichment (SELEX). This chapter describes a SELEX procedure for the identification of RNA aptamers against hexa-histidine-tagged proteins. For the efficient enrichment of higher affinity aptamers, the selection stringency should be gradually increased. Undesired RNA species that bind to affinity resins can be eliminated from the pool by using a negative selection step and alternating different types of resins.
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