1
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Hwang HG, Ye DY, Jung GY. Biosensor-guided discovery and engineering of metabolic enzymes. Biotechnol Adv 2023; 69:108251. [PMID: 37690614 DOI: 10.1016/j.biotechadv.2023.108251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 09/04/2023] [Accepted: 09/05/2023] [Indexed: 09/12/2023]
Abstract
A variety of chemicals have been produced through metabolic engineering approaches, and enhancing biosynthesis performance can be achieved by using enzymes with high catalytic efficiency. Accordingly, a number of efforts have been made to discover enzymes in nature for various applications. In addition, enzyme engineering approaches have been attempted to suit specific industrial purposes. However, a significant challenge in enzyme discovery and engineering is the efficient screening of enzymes with the desired phenotype from extensive enzyme libraries. To overcome this bottleneck, genetically encoded biosensors have been developed to specifically detect target molecules produced by enzyme activity at the intracellular level. Especially, the biosensors facilitate high-throughput screening (HTS) of targeted enzymes, expanding enzyme discovery and engineering strategies with advances in systems and synthetic biology. This review examines biosensor-guided HTS systems and highlights studies that have utilized these tools to discover enzymes in diverse areas and engineer enzymes to enhance their properties, such as catalytic efficiency, specificity, and stability.
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Affiliation(s)
- Hyun Gyu Hwang
- Institute of Environmental and Energy Technology, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Dae-Yeol Ye
- Department of Chemical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Gyoo Yeol Jung
- Department of Chemical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, Republic of Korea; School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, Republic of Korea.
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2
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Wu Y, Zhu L, Li S, Chu H, Wang X, Xu W. High content design of riboswitch biosensors: All-around rational module-by-module design. Biosens Bioelectron 2022; 220:114887. [DOI: 10.1016/j.bios.2022.114887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/27/2022] [Accepted: 11/03/2022] [Indexed: 11/11/2022]
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3
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Mukkayyan N, Poon R, Sander PN, Lai LY, Zubair-Nizami Z, Hammond MC, Chatterjee SS. In Vivo Detection of Cyclic-di-AMP in Staphylococcus aureus. ACS OMEGA 2022; 7:32749-32753. [PMID: 36120079 PMCID: PMC9476191 DOI: 10.1021/acsomega.2c04538] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/18/2022] [Indexed: 06/15/2023]
Abstract
Cyclic-di-AMP (CDA) is a signaling molecule that controls various cellular functions including antibiotic tolerance and osmoregulation in Staphylococcus aureus (S. aureus). In this study, we developed a novel biosensor (bsuO P6-4) for in vivo detection of CDA in S. aureus. The fluorescent biosensor is based on a natural CDA riboswitch from Bacillus subtilis connected at its P6 stem to the dye-binding aptamer Spinach. Our study showed that bsuO P6-4 could detect a wide concentration range of CDA in both laboratory and clinical strains, making it suitable for use in both basic and clinical research applications.
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Affiliation(s)
- Nagaraja Mukkayyan
- Department
of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland 21202, United States
- Institute
of Marine and Environmental Technology, Baltimore, Maryland 21202, United States
| | - Raymond Poon
- Department
of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland 21202, United States
- Institute
of Marine and Environmental Technology, Baltimore, Maryland 21202, United States
| | - Philipp N. Sander
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Li-Yin Lai
- Department
of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland 21202, United States
- Institute
of Marine and Environmental Technology, Baltimore, Maryland 21202, United States
| | - Zahra Zubair-Nizami
- Department
of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland 21202, United States
- Institute
of Marine and Environmental Technology, Baltimore, Maryland 21202, United States
| | - Ming C. Hammond
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Department
of Chemistry and Henry Eyring Center for Cell and Genome Sciences, University of Utah, Salt Lake City, Utah 84112, United States
| | - Som S. Chatterjee
- Department
of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, Maryland 21202, United States
- Institute
of Marine and Environmental Technology, Baltimore, Maryland 21202, United States
- University
of Maryland Center for Environmental Science, Baltimore, Maryland 21202, United States
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4
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Citartan M. The dynamicity of light-up aptamers in one-pot in vitro diagnostic assays. Analyst 2021; 147:10-21. [PMID: 34860215 DOI: 10.1039/d1an01690c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Light-up aptamers are aptamers that ignite the fluorescence emission of certain dyes upon binding. Widely harnessed in in vivo imaging, the binding capacity of the light-up aptamers can also be deployed in in vitro diagnostic assays, engendering a mix-and-read format. Intrigued by this, I intend to provide an overview of the various formats of diagnostic assays developed using light-up aptamers from the direct modulation of the light-up aptamers, split aptamer-based configuration, strand displacement, in vitro transcription-based one-pot diagnostic assay, CRISPR-Cas system to the measurement of the ion reliance. The incorporation of the light-up aptamers into each configuration is expounded and further supported by describing the exemplary assays developed thus far. It is anticipated that the present study can be enlightening to any researchers who aspire to embark on the development of one-pot in vitro diagnostic assays based on light-up aptamers.
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Affiliation(s)
- Marimuthu Citartan
- Advanced Medical & Dental Institute (AMDI), Universiti Sains Malaysia, Bertam, 13200, Kepala Batas, Penang, Malaysia.
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5
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Kolpashchikov DM, Spelkov AA. Binary (Split) Light‐up Aptameric Sensors. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.201914919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Dmitry M. Kolpashchikov
- Chemistry Department University of Central Florida Orlando FL 32816-2366 USA
- Burnett School of Biomedical Sciences University of Central Florida Orlando FL 32816 USA
| | - Alexander A. Spelkov
- Laboratory of Solution Chemistry of Advanced Materials and Technologies ITMO University 9 Lomonosova Str. St. Petersburg 191002 Russian Federation
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6
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Kitto RZ, Christiansen KE, Hammond MC. RNA-based fluorescent biosensors for live cell detection of bacterial sRNA. Biopolymers 2021; 112:e23394. [PMID: 32786000 PMCID: PMC7856060 DOI: 10.1002/bip.23394] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/11/2020] [Accepted: 07/13/2020] [Indexed: 01/21/2023]
Abstract
Bacteria contain a diverse set of RNAs to provide tight regulation of gene expression in response to environmental stimuli. Bacterial small RNAs (sRNAs) work in conjunction with protein cofactors to bind complementary mRNA sequences in the cell, leading to up- or downregulation of protein synthesis. In vivo imaging of sRNAs can aid in understanding their spatiotemporal dynamics in real time, which inspires new ways to manipulate these systems for a variety of applications including synthetic biology and therapeutics. Current methods for sRNA imaging are quite limited in vivo and do not provide real-time information about fluctuations in sRNA levels. Herein, we describe our efforts toward the development of an RNA-based fluorescent biosensor for bacterial sRNA both in vitro and in vivo. We validated these sensors for three different bacterial sRNAs in Escherichia coli and demonstrated that the designs provide a bright, sequence-specific signal output in response to exogenous and endogenous RNA targets.
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Affiliation(s)
- Rebekah Z Kitto
- Department of Chemistry, University of California, Berkeley, California, USA
- Department of Chemistry and Henry Eyring Center for Cell and Genome Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Kylee E Christiansen
- Department of Chemistry and Henry Eyring Center for Cell and Genome Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Ming C Hammond
- Department of Chemistry, University of California, Berkeley, California, USA
- Department of Chemistry and Henry Eyring Center for Cell and Genome Sciences, University of Utah, Salt Lake City, Utah, USA
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7
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Kolpashchikov DM, Spelkov AA. Binary (Split) Light-up Aptameric Sensors. Angew Chem Int Ed Engl 2020; 60:4988-4999. [PMID: 32208549 DOI: 10.1002/anie.201914919] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Indexed: 12/12/2022]
Abstract
This Minireview discusses the design and applications of binary (also known as split) light-up aptameric sensors (BLAS). BLAS consist of two RNA or DNA strands and a fluorogenic organic dye added as a buffer component. When associated, the two strands form a dye-binding site, followed by an increase in fluorescence of the aptamer-bound dye. The design is cost-efficient because it uses short oligonucleotides and does not require conjugation of organic dyes with nucleic acids. In some applications, BLAS design is preferable over monolithic sensors because of simpler assay optimization and improved selectivity. RNA-based BLAS can be expressed in cells and used for the intracellular monitoring of biological molecules. BLAS have been used as reporters of nucleic acid association events in RNA nanotechnology and nucleic-acid-based molecular computation. Other applications of BLAS include the detection of nucleic acids, proteins, and cancer cells, and potentially they can be tailored to report a broad range of biological analytes.
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Affiliation(s)
- Dmitry M Kolpashchikov
- Chemistry Department, University of Central Florida, Orlando, FL, 32816-2366, USA.,Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL, 32816, USA
| | - Alexander A Spelkov
- Laboratory of Solution Chemistry of Advanced Materials and Technologies, ITMO University, 9 Lomonosova Str., St. Petersburg, 191002, Russian Federation
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8
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Li X, Mo L, Litke JL, Dey SK, Suter SR, Jaffrey SR. Imaging Intracellular S-Adenosyl Methionine Dynamics in Live Mammalian Cells with a Genetically Encoded Red Fluorescent RNA-Based Sensor. J Am Chem Soc 2020; 142:14117-14124. [PMID: 32698574 PMCID: PMC8158784 DOI: 10.1021/jacs.0c02931] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
To understand the role of intracellular metabolites in cellular processes, it is important to measure the dynamics and fluxes of small molecules in living cells. Although conventional metabolite sensors composed of fluorescent proteins have been made to detect some metabolites, an emerging approach is to use genetically encoded sensors composed of RNA. Because of the ability to rapidly generate metabolite-binding RNA aptamers, RNA-based sensors have the potential to be designed more readily than protein-based sensors. Numerous strategies have been developed to convert the green-fluorescent Spinach or Broccoli fluorogenic RNA aptamers into metabolite-regulated sensors. Nevertheless, red fluorescence is particularly desirable because of the low level of red background fluorescence in cells. However, the red fluorescent variant of the Broccoli aptamer, Red Broccoli, does not exhibit red fluorescence in cells when imaged with its cognate fluorophore. It is not known why Red Broccoli is fluorescent in vitro but not in live mammalian cells. Here, we develop a new fluorophore, OBI (3,5-difluoro-4-hydroxybenzylidene-imidazolinone-2-oxime-1-benzoimidazole), which binds Red Broccoli with high affinity and makes Red Broccoli resistant to thermal unfolding. We show that OBI enables Red Broccoli to be readily detected in live mammalian cells. Furthermore, we show that Red Broccoli can be fused to a S-adenosyl methionine (SAM)-binding aptamer to generate a red fluorescent RNA-based sensor that enables imaging of SAM in live mammalian cells. These results reveal a red fluorescent fluorogenic aptamer that functions in mammalian cells and that can be readily developed into red fluorescent RNA-based sensors.
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Affiliation(s)
- Xing Li
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Liuting Mo
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Jacob L Litke
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Sourav Kumar Dey
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Scott R Suter
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
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9
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Deng H, Yan S, Huang Y, Lei C, Nie Z. Design strategies for fluorescent proteins/mimics and their applications in biosensing and bioimaging. Trends Analyt Chem 2020. [DOI: 10.1016/j.trac.2019.115757] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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10
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Weiss CA, Hoberg JA, Liu K, Tu BP, Winkler WC. Single-Cell Microscopy Reveals That Levels of Cyclic di-GMP Vary among Bacillus subtilis Subpopulations. J Bacteriol 2019; 201:e00247-19. [PMID: 31138629 PMCID: PMC6657594 DOI: 10.1128/jb.00247-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 05/21/2019] [Indexed: 11/20/2022] Open
Abstract
The synthesis of signaling molecules is one strategy bacteria employ to sense alterations in their environment and rapidly adjust to those changes. In Gram-negative bacteria, bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) regulates the transition from a unicellular motile state to a multicellular sessile state. However, c-di-GMP signaling has been less intensively studied in Gram-positive organisms. To that end, we constructed a fluorescent yfp reporter based on a c-di-GMP-responsive riboswitch to visualize the relative abundance of c-di-GMP for single cells of the Gram-positive model organism Bacillus subtilis Coupled with cell-type-specific fluorescent reporters, this riboswitch reporter revealed that c-di-GMP levels are markedly different among B. subtilis cellular subpopulations. For example, cells that have made the decision to become matrix producers maintain higher intracellular c-di-GMP concentrations than motile cells. Similarly, we find that c-di-GMP levels differ between sporulating and competent cell types. These results suggest that biochemical measurements of c-di-GMP abundance are likely to be inaccurate for a bulk ensemble of B. subtilis cells, as such measurements will average c-di-GMP levels across the population. Moreover, the significant variation in c-di-GMP levels between cell types hints that c-di-GMP might play an important role during B. subtilis biofilm formation. This study therefore emphasizes the importance of using single-cell approaches for analyzing metabolic trends within ensemble bacterial populations.IMPORTANCE Many bacteria have been shown to differentiate into genetically identical yet morphologically distinct cell types. Such population heterogeneity is especially prevalent among biofilms, where multicellular communities are primed for unexpected environmental conditions and can efficiently distribute metabolic responsibilities. Bacillus subtilis is a model system for studying population heterogeneity; however, a role for c-di-GMP in these processes has not been thoroughly investigated. Herein, we introduce a fluorescent reporter, based on a c-di-GMP-responsive riboswitch, to visualize the relative abundance of c-di-GMP for single B. subtilis cells. Our analysis shows that c-di-GMP levels are conspicuously different among B. subtilis cellular subtypes, suggesting a role for c-di-GMP during biofilm formation. These data highlight the utility of riboswitches as tools for imaging metabolic changes within individual bacterial cells. Analyses such as these offer new insight into c-di-GMP-regulated phenotypes, especially given that other biofilms also consist of multicellular communities.
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Affiliation(s)
- Cordelia A Weiss
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Jakob A Hoberg
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Kuanqing Liu
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Benjamin P Tu
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Wade C Winkler
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
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11
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Intracellular Imaging with Genetically Encoded RNA-based Molecular Sensors. NANOMATERIALS 2019; 9:nano9020233. [PMID: 30744040 PMCID: PMC6410142 DOI: 10.3390/nano9020233] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 02/05/2019] [Accepted: 02/05/2019] [Indexed: 01/10/2023]
Abstract
Genetically encodable sensors have been widely used in the detection of intracellular molecules ranging from metal ions and metabolites to nucleic acids and proteins. These biosensors are capable of monitoring in real-time the cellular levels, locations, and cell-to-cell variations of the target compounds in living systems. Traditionally, the majority of these sensors have been developed based on fluorescent proteins. As an exciting alternative, genetically encoded RNA-based molecular sensors (GERMS) have emerged over the past few years for the intracellular imaging and detection of various biological targets. In view of their ability for the general detection of a wide range of target analytes, and the modular and simple design principle, GERMS are becoming a popular choice for intracellular analysis. In this review, we summarize different design principles of GERMS based on various RNA recognition modules, transducer modules, and reporting systems. Some recent advances in the application of GERMS for intracellular imaging are also discussed. With further improvement in biostability, sensitivity, and robustness, GERMS can potentially be widely used in cell biology and biotechnology.
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12
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Enabling tools for high-throughput detection of metabolites: Metabolic engineering and directed evolution applications. Biotechnol Adv 2017; 35:950-970. [PMID: 28723577 DOI: 10.1016/j.biotechadv.2017.07.005] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 06/07/2017] [Accepted: 07/11/2017] [Indexed: 12/21/2022]
Abstract
Within the Design-Build-Test Cycle for strain engineering, rapid product detection and selection strategies remain challenging and limit overall throughput. Here we summarize a wide variety of modalities that transduce chemical concentrations into easily measured absorbance, luminescence, and fluorescence signals. Specifically, we cover protein-based biosensors (including transcription factors), nucleic acid-based biosensors, coupled enzyme reactions, bioorthogonal chemistry, and fluorescent and chromogenic dyes and substrates as modalities for detection. We focus on the use of these methods for strain engineering and enzyme discovery and conclude with remarks on the current and future state of biosensor development for application in the metabolic engineering field.
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13
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Chakraborty K, Veetil AT, Jaffrey SR, Krishnan Y. Nucleic Acid-Based Nanodevices in Biological Imaging. Annu Rev Biochem 2017; 85:349-73. [PMID: 27294440 DOI: 10.1146/annurev-biochem-060815-014244] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The nanoscale engineering of nucleic acids has led to exciting molecular technologies for high-end biological imaging. The predictable base pairing, high programmability, and superior new chemical and biological methods used to access nucleic acids with diverse lengths and in high purity, coupled with computational tools for their design, have allowed the creation of a stunning diversity of nucleic acid-based nanodevices. Given their biological origin, such synthetic devices have a tremendous capacity to interface with the biological world, and this capacity lies at the heart of several nucleic acid-based technologies that are finding applications in biological systems. We discuss these diverse applications and emphasize the advantage, in terms of physicochemical properties, that the nucleic acid scaffold brings to these contexts. As our ability to engineer this versatile scaffold increases, its applications in structural, cellular, and organismal biology are clearly poised to massively expand.
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Affiliation(s)
- Kasturi Chakraborty
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637; , ,
| | - Aneesh T Veetil
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637; , ,
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Medical College of Cornell University, New York, New York 10065;
| | - Yamuna Krishnan
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637; , , .,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, University of Chicago, Chicago, Illinois 60637
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14
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Kirchner M, Schneider S. Gene expression control by Bacillus anthracis purine riboswitches. RNA (NEW YORK, N.Y.) 2017; 23:762-769. [PMID: 28209633 PMCID: PMC5393184 DOI: 10.1261/rna.058792.116] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 02/12/2017] [Indexed: 06/06/2023]
Abstract
In all kingdoms of life, cellular replication relies on the presence of nucleosides and nucleotides, the building blocks of nucleic acids and the main source of energy. In bacteria, the availability of metabolites sometimes directly regulates the expression of enzymes and proteins involved in purine salvage, biosynthesis, and uptake through riboswitches. Riboswitches are located in bacterial mRNAs and can control gene expression by conformational changes in response to ligand binding. We have established an inverse reporter gene system in Bacillus subtilis that allows us to monitor riboswitch-controlled gene expression. We used it to investigate the activity of five potential purine riboswitches from Bacillus anthracis in response to different purines and pyrimidines. Furthermore, in vitro studies on the aptamer domains of the riboswitches reveal their variation in guanine binding affinity ranging from namomolar to micromolar. These data do not only provide insight into metabolite sensing but can also aid in engineering artificial cell regulatory systems.
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Affiliation(s)
- Marion Kirchner
- Center for Integrated Protein Science at the Department of Chemistry, Technische Universität München, 85748 Garching, Germany
| | - Sabine Schneider
- Center for Integrated Protein Science at the Department of Chemistry, Technische Universität München, 85748 Garching, Germany
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15
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Jones CP, Ferré-D'Amaré AR. Long-Range Interactions in Riboswitch Control of Gene Expression. Annu Rev Biophys 2017; 46:455-481. [PMID: 28375729 DOI: 10.1146/annurev-biophys-070816-034042] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Riboswitches are widespread RNA motifs that regulate gene expression in response to fluctuating metabolite concentrations. Known primarily from bacteria, riboswitches couple specific ligand binding and changes in RNA structure to mRNA expression in cis. Crystal structures of the ligand binding domains of most of the phylogenetically widespread classes of riboswitches, each specific to a particular metabolite or ion, are now available. Thus, the bound states-one end point-have been thoroughly characterized, but the unbound states have been more elusive. Consequently, it is less clear how the unbound, sensing riboswitch refolds into the ligand binding-induced output state. The ligand recognition mechanisms of riboswitches are diverse, but we find that they share a common structural strategy in positioning their binding sites at the point of the RNA three-dimensional fold where the residues farthest from one another in sequence meet. We review how riboswitch folds adhere to this fundamental strategy and propose future research directions for understanding and harnessing their ability to specifically control gene expression.
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Affiliation(s)
- Christopher P Jones
- Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20824;
| | - Adrian R Ferré-D'Amaré
- Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20824;
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16
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Genetic biosensors for small-molecule products: Design and applications in high-throughput screening. Front Chem Sci Eng 2017. [DOI: 10.1007/s11705-017-1629-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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17
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Abstract
Second-generation RNA-based fluorescent biosensors have been developed that enable flow cytometry experiments to monitor the population dynamics of c-di-GMP signaling in live bacteria. These experiments are high-throughput, provide information at the single-cell level, and can be performed on cells grown in complex media and/or under anaerobic conditions. Here, we describe flow cytometry methods for three applications: (1) high-throughput screening for diguanylate cyclase activity, (2) analyzing c-di-GMP levels under anaerobic conditions, and (3) monitoring cell population dynamics of c-di-GMP levels upon environmental changes. These methods showcase RNA-based fluorescent biosensors as versatile tools for studying c-di-GMP signaling in bacteria.
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Affiliation(s)
- Jongchan Yeo
- Department of Chemistry, University of California, Berkeley, 94720, USA
| | - Xin C Wang
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA
| | - Ming C Hammond
- Department of Chemistry, University of California, Berkeley, 94720, USA.
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA.
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18
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Bose D, Su Y, Marcus A, Raulet DH, Hammond MC. An RNA-Based Fluorescent Biosensor for High-Throughput Analysis of the cGAS-cGAMP-STING Pathway. Cell Chem Biol 2016; 23:1539-1549. [PMID: 27889408 DOI: 10.1016/j.chembiol.2016.10.014] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/02/2016] [Accepted: 10/25/2016] [Indexed: 12/15/2022]
Abstract
In mammalian cells, the second messenger (2'-5',3'-5') cyclic guanosine monophosphate-adenosine monophosphate (2',3'-cGAMP), is produced by the cytosolic DNA sensor cGAMP synthase (cGAS), and subsequently bound by the stimulator of interferon genes (STING) to trigger interferon response. Thus, the cGAS-cGAMP-STING pathway plays a critical role in pathogen detection, as well as pathophysiological conditions including cancer and autoimmune disorders. However, studying and targeting this immune signaling pathway has been challenging due to the absence of tools for high-throughput analysis. We have engineered an RNA-based fluorescent biosensor that responds to 2',3'-cGAMP. The resulting "mix-and-go" cGAS activity assay shows excellent statistical reliability as a high-throughput screening (HTS) assay and distinguishes between direct and indirect cGAS inhibitors. Furthermore, the biosensor enables quantitation of 2',3'-cGAMP in mammalian cell lysates. We envision this biosensor-based assay as a resource to study the cGAS-cGAMP-STING pathway in the context of infectious diseases, cancer immunotherapy, and autoimmune diseases.
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Affiliation(s)
- Debojit Bose
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Yichi Su
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Assaf Marcus
- Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA
| | - David H Raulet
- Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Ming C Hammond
- Department of Chemistry, University of California, Berkeley, CA 94720, USA; Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA.
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Mehdizadeh Aghdam E, Hejazi MS, Barzegar A. Riboswitches: From living biosensors to novel targets of antibiotics. Gene 2016; 592:244-59. [PMID: 27432066 DOI: 10.1016/j.gene.2016.07.035] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Revised: 07/11/2016] [Accepted: 07/14/2016] [Indexed: 12/24/2022]
Abstract
Riboswitches are generally located in 5'-UTR region of mRNAs and specifically bind small ligands. Following ligand binding, gene expression is controlled mostly by transcription termination, translation inhibition or mRNA degradation processes. More than 30 classes of known riboswitches have been identified by now. Most riboswitches consist of an aptamer domain and an expression platform. The aptamer domain of each class of riboswitch is a conserved structure and stabilizes specific structures of the expression platforms through binding to specific compounds. In this review, we are highlighting most aspects of riboswitch research including the novel riboswitch discoveries, routine methods for discovering and investigating riboswitches along with newly discovered classes and mechanistic principles of riboswitch-mediated gene expression control. Moreover, we will give an overview about the potential of riboswitches as therapeutic targets for antibiotic design and also their utilization as biosensors for molecular detection.
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Affiliation(s)
- Elnaz Mehdizadeh Aghdam
- Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran; Molecular Medicine Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
| | - Mohammad Saeid Hejazi
- Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran; Molecular Medicine Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Abolfazl Barzegar
- Research Institute for Fundamental Sciences (RIFS), University of Tabriz, Tabriz, Iran; The School of Advanced Biomedical Sciences (SABS), Tabriz University of Medical Sciences, Tabriz, Iran
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Wang XC, Wilson SC, Hammond MC. Next-generation RNA-based fluorescent biosensors enable anaerobic detection of cyclic di-GMP. Nucleic Acids Res 2016; 44:e139. [PMID: 27382070 PMCID: PMC5041473 DOI: 10.1093/nar/gkw580] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 06/16/2016] [Indexed: 12/14/2022] Open
Abstract
Bacteria occupy a diverse set of environmental niches with differing oxygen availability. Anaerobic environments such as mammalian digestive tracts and industrial reactors harbor an abundance of both obligate and facultative anaerobes, many of which play significant roles in human health and biomanufacturing. Studying bacterial function under partial or fully anaerobic conditions, however, is challenging given the paucity of suitable live-cell imaging tools. Here, we introduce a series of RNA-based fluorescent biosensors that respond selectively to cyclic di-GMP, an intracellular bacterial second messenger that controls cellular motility and biofilm formation. We demonstrate the utility of these biosensors in vivo under both aerobic and anaerobic conditions, and we show that biosensor expression does not interfere with the native motility phenotype. Together, our results attest to the effectiveness and versatility of RNA-based fluorescent biosensors, priming further development and application of these and other analogous sensors to study host–microbial and microbial–microbial interactions through small molecule signals.
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Affiliation(s)
- Xin C Wang
- Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Stephen C Wilson
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Ming C Hammond
- Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA Department of Chemistry, University of California, Berkeley, CA 94720, USA
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Ilgu M, Ray J, Bendickson L, Wang T, Geraskin IM, Kraus GA, Nilsen-Hamilton M. Light-up and FRET aptamer reporters; evaluating their applications for imaging transcription in eukaryotic cells. Methods 2015; 98:26-33. [PMID: 26707205 DOI: 10.1016/j.ymeth.2015.12.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/11/2015] [Accepted: 12/15/2015] [Indexed: 11/19/2022] Open
Abstract
The regulation of RNA transcription is central to cellular function. Changes in gene expression drive differentiation and cellular responses to events such as injury. RNA trafficking can also have a large impact on protein expression and its localization. Thus, the ability to image RNA transcription and trafficking in real time and in living cells is a worthwhile goal that has been difficult to achieve. The availability of "light-up" aptamers that cause an increase in fluorescence of their ligands when bound by the aptamer have shown promise for reporting on RNA production and localization in vivo. Here we have investigated two light-up aptamers (the malachite green aptamer and the Spinach aptamers) for their suitabilities as reporters of RNA expression in vivo using two eukaryotic cell types, yeast and mammalian. Our analysis focused on the aptamer ligands, their contributions to background noise, and the impact of tandem aptamer strings on signal strength and ligand affinity. Whereas the background fluorescence is very low in vitro, this is not always true for cell imaging. Our results suggest the need for caution in using light-up aptamers as reporters for imaging RNA. In particular, images should be collected and analyzed by operators blinded to the sample identities. The appropriate control condition of ligand with the cells in the absence of aptamer expression must be included in each experiment. This control condition establishes that the specific interaction of ligand with aptamer, rather than nonspecific interactions with unknown cell elements, is responsible for the observed fluorescent signals. High background signals due to nonspecific interactions of aptamer ligands with cell components can be minimized by using IMAGEtags (Intracellular Multiaptamer GEnetic tags), which signal by FRET and are promising RNA reporters for imaging transcription.
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Affiliation(s)
- Muslum Ilgu
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, United States
| | - Judhajeet Ray
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, United States
| | - Lee Bendickson
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, United States; Ames Laboratory, US DOE, United States
| | | | | | - George A Kraus
- Department of Chemistry, Ames, IA, United States; Ames Laboratory, US DOE, United States
| | - Marit Nilsen-Hamilton
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, United States; Ames Laboratory, US DOE, United States.
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Imaging metabolite dynamics in living cells using a Spinach-based riboswitch. Proc Natl Acad Sci U S A 2015; 112:E2756-65. [PMID: 25964329 DOI: 10.1073/pnas.1504354112] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Riboswitches are natural ligand-sensing RNAs typically that are found in the 5' UTRs of mRNA. Numerous classes of riboswitches have been discovered, enabling mRNA to be regulated by diverse and physiologically important cellular metabolites and small molecules. Here we describe Spinach riboswitches, a new class of genetically encoded metabolite sensor derived from naturally occurring riboswitches. Drawing upon the structural switching mechanism of natural riboswitches, we show that Spinach can be swapped for the expression platform of various riboswitches, allowing metabolite binding to induce Spinach fluorescence directly. In the case of the thiamine 5'-pyrophosphate (TPP) riboswitch from the Escherichia coli thiM gene encoding hydroxyethylthiazole kinase, we show that insertion of Spinach results in an RNA sensor that exhibits fluorescence upon binding TPP. This TPP Spinach riboswitch binds TPP with affinity and selectivity similar to that of the endogenous riboswitch and enables the discovery of agonists and antagonists of the TPP riboswitch using simple fluorescence readouts. Furthermore, expression of the TPP Spinach riboswitch in Escherichia coli enables live imaging of dynamic changes in intracellular TPP concentrations in individual cells. Additionally, we show that other riboswitches that use a structural mechanism similar to that of the TPP riboswitch, including the guanine and adenine riboswitches from the Bacillus subtilis xpt gene encoding xanthine phosphoribosyltransferase, and the S-adenosyl-methionine-I riboswitch from the B. subtilis yitJ gene encoding methionine synthase, can be converted into Spinach riboswitches. Thus, Spinach riboswitches constitute a novel class of RNA-based fluorescent metabolite sensors that exploit the diversity of naturally occurring ligand-binding riboswitches.
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