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Shabestary K, Klemm C, Carling B, Marshall J, Savigny J, Storch M, Ledesma-Amaro R. Phenotypic heterogeneity follows a growth-viability tradeoff in response to amino acid identity. Nat Commun 2024; 15:6515. [PMID: 39095345 PMCID: PMC11297284 DOI: 10.1038/s41467-024-50602-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 07/16/2024] [Indexed: 08/04/2024] Open
Abstract
In their natural environments, microorganisms mainly operate at suboptimal growth conditions with fluctuations in nutrient abundance. The resulting cellular adaptation is subject to conflicting tasks: growth or survival maximisation. Here, we study this adaptation by systematically measuring the impact of a nitrogen downshift to 24 nitrogen sources on cellular metabolism at the single-cell level. Saccharomyces lineages grown in rich media and exposed to a nitrogen downshift gradually differentiate to form two subpopulations of different cell sizes where one favours growth while the other favours viability with an extended chronological lifespan. This differentiation is asymmetrical with daughter cells representing the new differentiated state with increased viability. We characterise the metabolic response of the subpopulations using RNA sequencing, metabolic biosensors and a transcription factor-tagged GFP library coupled to high-throughput microscopy, imaging more than 800,000 cells. We find that the subpopulation with increased viability is associated with a dormant quiescent state displaying differences in MAPK signalling. Depending on the identity of the nitrogen source present, differentiation into the quiescent state can be actively maintained, attenuated, or aborted. These results establish amino acids as important signalling molecules for the formation of genetically identical subpopulations, involved in chronological lifespan and growth rate determination.
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Affiliation(s)
- Kiyan Shabestary
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW7 2AZ, UK.
| | - Cinzia Klemm
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW7 2AZ, UK
| | - Benedict Carling
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW7 2AZ, UK
- London Biofoundry, Imperial College Translation & Innovation Hub, London, UK
| | - James Marshall
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW7 2AZ, UK
- London Biofoundry, Imperial College Translation & Innovation Hub, London, UK
| | - Juline Savigny
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW7 2AZ, UK
| | - Marko Storch
- London Biofoundry, Imperial College Translation & Innovation Hub, London, UK
- Department of Infectious Disease, Imperial College London, London, SW7 2AZ, UK
| | - Rodrigo Ledesma-Amaro
- Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW7 2AZ, UK.
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2
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Pietruschka G, Ranzani AT, Weber A, Patwari T, Pilsl S, Renzl C, Otte DM, Pyka D, Möglich A, Mayer G. An RNA Motif That Enables Optozyme Control and Light-Dependent Gene Expression in Bacteria and Mammalian Cells. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2304519. [PMID: 38227373 DOI: 10.1002/advs.202304519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 12/19/2023] [Indexed: 01/17/2024]
Abstract
The regulation of gene expression by light enables the versatile, spatiotemporal manipulation of biological function in bacterial and mammalian cells. Optoribogenetics extends this principle by molecular RNA devices acting on the RNA level whose functions are controlled by the photoinduced interaction of a light-oxygen-voltage photoreceptor with cognate RNA aptamers. Here light-responsive ribozymes, denoted optozymes, which undergo light-dependent self-cleavage and thereby control gene expression are described. This approach transcends existing aptamer-ribozyme chimera strategies that predominantly rely on aptamers binding to small molecules. The optozyme method thus stands to enable the graded, non-invasive, and spatiotemporally resolved control of gene expression. Optozymes are found efficient in bacteria and mammalian cells and usher in hitherto inaccessible optoribogenetic modalities with broad applicability in synthetic and systems biology.
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Affiliation(s)
- Georg Pietruschka
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
| | - Américo T Ranzani
- Lehrstuhl für Biochemie, Photobiochemie, University of Bayreuth, Universitätsstraße 30, 95440, Bayreuth, Germany
| | - Anna Weber
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
- Center of Aptamer Research & Development, University of Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany
| | - Tejal Patwari
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
| | - Sebastian Pilsl
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
| | - Christian Renzl
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
- Center of Aptamer Research & Development, University of Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany
| | - David M Otte
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
| | - Daniel Pyka
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
| | - Andreas Möglich
- Lehrstuhl für Biochemie, Photobiochemie, University of Bayreuth, Universitätsstraße 30, 95440, Bayreuth, Germany
| | - Günter Mayer
- Life and Medical Sciences (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121, Bonn, Germany
- Center of Aptamer Research & Development, University of Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany
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3
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Cui W, Lin Q, Wu Y, Wang X, Zhang Y, Lin X, Zhang L, Liu X, Han L, Zhou Z. Creation of Architecturally Minimal Transcriptionally Activating Riboswitches Responsive to Theophylline Reveals an Unconventional Design Strategy. ACS Synth Biol 2023; 12:3716-3729. [PMID: 38052004 DOI: 10.1021/acssynbio.3c00519] [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] [Indexed: 12/07/2023]
Abstract
Riboswitches are noncoding RNA switches that are largely utilized in bacteria and play a significant role in synthetic biology. Nonetheless, their natural counterparts possess lengthy sequences and intricate structures, posing challenges for their modular integration into complex gene circuits. Consequently, it is imperative to develop simplified synthetic riboswitches that can be effortlessly incorporated into gene circuits. The conventional approach to generate synthetic riboswitches entails tedious library construction and extensive screening, which frequently yields suboptimal performance. To overcome this obstacle, alternative methods are urgently needed. In this study, we created a novel approach to designing a diverse set of transcription-activating riboswitches that exhibit high performance and broad compatibility. The strategy involved starting with a synthetic theophylline RNA aptamer and designing an expression platform that forms a transcriptional terminator in its inactive state but switches to an antiterminator when it is activated. Several sequences were designed, constructed, and subjected to virtual screening, resulting in the identification of two transcription-activating riboswitches. These riboswitches were then engineered to reduce the basal leakage and increase the activation level through extending the hairpin region using a screened random sequence. These architecturally minimal synthetic riboswitches were highly adapted to different constitutive promoters in a modular manner, generating a differentially responsive output to theophylline. As a proof-of-principle, the synthetic riboswitches were applied to rewire a synthetic quorum-sensing circuit (QSC). The reprogrammed QSC successfully modulated the temporal responsive profile against the activation. This strategy is expected to expand the variety of high-performance riboswitches that are responsive to different ligands, thereby further facilitating the design of complex genetic circuits.
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Affiliation(s)
- Wenjing Cui
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
- Key Laboratory of Industrial Biotechnology, MOE, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Qiao Lin
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Yi Wu
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Xinran Wang
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Yuqing Zhang
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Xinyu Lin
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Linpei Zhang
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
- Key Laboratory of Industrial Biotechnology, MOE, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Xu Liu
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Laichuang Han
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
- Key Laboratory of Industrial Biotechnology, MOE, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Zhemin Zhou
- School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
- Key Laboratory of Industrial Biotechnology, MOE, Jiangnan University, Wuxi, Jiangsu 214122, China
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4
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Torello Pianale L, Olsson L. ScEnSor Kit for Saccharomyces cerevisiae Engineering and Biosensor-Driven Investigation of the Intracellular Environment. ACS Synth Biol 2023; 12:2493-2497. [PMID: 37552581 PMCID: PMC10443032 DOI: 10.1021/acssynbio.3c00124] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Indexed: 08/10/2023]
Abstract
In this study, the three-step build-transform-assess toolbox for real-time monitoring of the yeast intracellular environment has been expanded and upgraded to the two-module ScEnSor (S. cerevisiae Engineering + Biosensor) Kit. The Biosensor Module includes eight fluorescent reporters for the intracellular environment; three of them (unfolded protein response, pyruvate metabolism, and ethanol consumption) were newly implemented to complement the original five. The Genome-Integration Module comprises a set of backbone plasmids for the assembly of 1-6 transcriptional units (each consisting of promoter, coding sequence, and terminator) for efficient marker-free single-locus genome integration (in HO and/or X2 loci). Altogether, the ScEnSor Kit enables rapid and easy construction of strains with new transcriptional units as well as high-throughput investigation of the yeast intracellular environment.
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Affiliation(s)
- Luca Torello Pianale
- Industrial
Biotechnology Division, Department of Life Sciences, Chalmers University of Technology, 412 96, Gothenburg, Sweden
| | - Lisbeth Olsson
- Industrial
Biotechnology Division, Department of Life Sciences, Chalmers University of Technology, 412 96, Gothenburg, Sweden
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5
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Ortega AD. Real-Time Assessment of Intracellular Metabolites in Single Cells through RNA-Based Sensors. Biomolecules 2023; 13:biom13050765. [PMID: 37238635 DOI: 10.3390/biom13050765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/24/2023] [Accepted: 04/26/2023] [Indexed: 05/28/2023] Open
Abstract
Quantification of the concentration of particular cellular metabolites reports on the actual utilization of metabolic pathways in physiological and pathological conditions. Metabolite concentration also constitutes the readout for screening cell factories in metabolic engineering. However, there are no direct approaches that allow for real-time assessment of the levels of intracellular metabolites in single cells. In recent years, the modular architecture of natural bacterial RNA riboswitches has inspired the design of genetically encoded synthetic RNA devices that convert the intracellular concentration of a metabolite into a quantitative fluorescent signal. These so-called RNA-based sensors are composed of a metabolite-binding RNA aptamer as the sensor domain, connected through an actuator segment to a signal-generating reporter domain. However, at present, the variety of available RNA-based sensors for intracellular metabolites is still very limited. Here, we go through natural mechanisms for metabolite sensing and regulation in cells across all kingdoms, focusing on those mediated by riboswitches. We review the design principles underlying currently developed RNA-based sensors and discuss the challenges that hindered the development of novel sensors and recent strategies to address them. We finish by introducing the current and potential applicability of synthetic RNA-based sensors for intracellular metabolites.
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Affiliation(s)
- Alvaro Darío Ortega
- Department of Cell Biology, Faculty of Biological Sciences, Complutense University of Madrid, 28040 Madrid, Spain
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6
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Mormino M, Lenitz I, Siewers V, Nygård Y. Identification of acetic acid sensitive strains through biosensor-based screening of a Saccharomyces cerevisiae CRISPRi library. Microb Cell Fact 2022; 21:214. [PMID: 36243715 PMCID: PMC9571444 DOI: 10.1186/s12934-022-01938-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 10/02/2022] [Indexed: 11/10/2022] Open
Abstract
Background Acetic acid tolerance is crucial for the development of robust cell factories for conversion of lignocellulosic hydrolysates that typically contain high levels of acetic acid. Screening mutants for growth in medium with acetic acid is an attractive way to identify sensitive variants and can provide novel insights into the complex mechanisms regulating the acetic acid stress response. Results An acetic acid biosensor based on the Saccharomyces cerevisiae transcription factor Haa1, was used to screen a CRISPRi yeast strain library where dCas9-Mxi was set to individually repress each essential or respiratory growth essential gene. Fluorescence-activated cell sorting led to the enrichment of a population of cells with higher acetic acid retention. These cells with higher biosensor signal were demonstrated to be more sensitive to acetic acid. Biosensor-based screening of the CRISPRi library strains enabled identification of strains with increased acetic acid sensitivity: strains with gRNAs targeting TIF34, MSN5, PAP1, COX10 or TRA1. Conclusions This study demonstrated that biosensors are valuable tools for screening and monitoring acetic acid tolerance in yeast. Fine-tuning the expression of essential genes can lead to altered acetic acid tolerance. Supplementary Information The online version contains supplementary material available at 10.1186/s12934-022-01938-7.
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Affiliation(s)
- Maurizio Mormino
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Ibai Lenitz
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Verena Siewers
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Yvonne Nygård
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
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7
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Jain A, Zoncu R. Organelle transporters and inter-organelle communication as drivers of metabolic regulation and cellular homeostasis. Mol Metab 2022; 60:101481. [PMID: 35342037 PMCID: PMC9043965 DOI: 10.1016/j.molmet.2022.101481] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/14/2022] [Accepted: 03/21/2022] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Spatial compartmentalization of metabolic pathways within membrane-separated organelles is key to the ability of eukaryotic cells to precisely regulate their biochemical functions. Membrane-bound organelles such as mitochondria, endoplasmic reticulum (ER) and lysosomes enable the concentration of metabolic precursors within optimized chemical environments, greatly accelerating the efficiency of both anabolic and catabolic reactions, enabling division of labor and optimal utilization of resources. However, metabolic compartmentalization also poses a challenge to cells because it creates spatial discontinuities that must be bridged for reaction cascades to be connected and completed. To do so, cells employ different methods to coordinate metabolic fluxes occurring in different organelles, such as membrane-localized transporters to facilitate regulated metabolite exchange between mitochondria and lysosomes, non-vesicular transport pathways via physical contact sites connecting the ER with both mitochondria and lysosomes, as well as localized regulatory signaling processes that coordinately regulate the activity of all these organelles. SCOPE OF REVIEW This review covers how cells use membrane transporters, membrane contact sites, and localized signaling pathways to mediate inter-organelle communication and coordinate metabolism. We also describe how disruption of inter-organelle communication is an emerging driver in a multitude of diseases, from cancer to neurodegeneration. MAJOR CONCLUSIONS Effective communication among organelles is essential to cellular health and function. Identifying the major molecular players involved in mediating metabolic coordination between organelles will further our understanding of cellular metabolism in health and lead us to design better therapeutics against dysregulated metabolism in disease.
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Affiliation(s)
- Aakriti Jain
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Roberto Zoncu
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
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8
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Integrative metabolic flux analysis reveals an indispensable dimension of phenotypes. Curr Opin Biotechnol 2022; 75:102701. [DOI: 10.1016/j.copbio.2022.102701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 01/26/2022] [Accepted: 02/04/2022] [Indexed: 02/06/2023]
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9
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Geraci I, Autour A, Pietruschka G, Shiian A, Borisova M, Mayer C, Ryckelynck M, Mayer G. Fluorogenic RNA-Based Biosensor to Sense the Glycolytic Flux in Mammalian Cells. ACS Chem Biol 2022; 17:1164-1173. [PMID: 35427113 DOI: 10.1021/acschembio.2c00100] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The visualization of metabolic flux in real time requires sensor molecules that transduce variations of metabolite concentrations into an appropriate output signal. In this regard, fluorogenic RNA-based biosensors are promising molecular tools as they fluoresce only upon binding to another molecule. However, to date no such sensor is available that enables the direct observation of key metabolites in mammalian cells. Toward this direction, we selected and characterized an RNA light-up sensor designed to respond to fructose 1,6-bisphosphate and applied it to probe glycolytic flux variation in mammal cells.
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Affiliation(s)
- Ignazio Geraci
- Life and Medical Sciences Institute (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121 Bonn, Germany
| | - Alexis Autour
- Université de Strasbourg, CNRS, Architecture et Réactivité de l’ARN, UPR 9002, 67084 Strasbourg, France
| | - Georg Pietruschka
- Life and Medical Sciences Institute (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121 Bonn, Germany
| | - Aleksandra Shiian
- Life and Medical Sciences Institute (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121 Bonn, Germany
| | - Marina Borisova
- Interfaculty Institute of Microbiology and Infection Medicine, Organismic Interactions/Glycobiology, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany
| | - Christoph Mayer
- Interfaculty Institute of Microbiology and Infection Medicine, Organismic Interactions/Glycobiology, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany
| | - Michael Ryckelynck
- Université de Strasbourg, CNRS, Architecture et Réactivité de l’ARN, UPR 9002, 67084 Strasbourg, France
| | - Günter Mayer
- Life and Medical Sciences Institute (LIMES), University of Bonn, Gerhard-Domagk-Str.1, 53121 Bonn, Germany
- Center of Aptamer Research & Development, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
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10
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Dey SK, Filonov GS, Olarerin-George AO, Jackson BT, Finley LWS, Jaffrey SR. Repurposing an adenine riboswitch into a fluorogenic imaging and sensing tag. Nat Chem Biol 2022; 18:180-190. [PMID: 34937909 PMCID: PMC8967656 DOI: 10.1038/s41589-021-00925-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 10/18/2021] [Indexed: 02/02/2023]
Abstract
Fluorogenic RNA aptamers are used to genetically encode fluorescent RNA and to construct RNA-based metabolite sensors. Unlike naturally occurring aptamers that efficiently fold and undergo metabolite-induced conformational changes, fluorogenic aptamers can exhibit poor folding, which limits their cellular fluorescence. To overcome this, we evolved a naturally occurring well-folded adenine riboswitch into a fluorogenic aptamer. We generated a library of roughly 1015 adenine aptamer-like RNAs in which the adenine-binding pocket was randomized for both size and sequence, and selected Squash, which binds and activates the fluorescence of green fluorescent protein-like fluorophores. Squash exhibits markedly improved in-cell folding and highly efficient metabolite-dependent folding when fused to a S-adenosylmethionine (SAM)-binding aptamer. A Squash-based ratiometric sensor achieved quantitative SAM measurements, revealed cell-to-cell heterogeneity in SAM levels and revealed metabolic origins of SAM. These studies show that the efficient folding of naturally occurring aptamers can be exploited to engineer well-folded cell-compatible fluorogenic aptamers and devices.
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Affiliation(s)
- Sourav Kumar Dey
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY, USA
| | - Grigory S Filonov
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY, USA
- Sartorius, Ann Arbor, MI, USA
| | | | - Benjamin T Jackson
- Cell Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Lydia W S Finley
- Cell Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY, USA.
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11
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Robustness: linking strain design to viable bioprocesses. Trends Biotechnol 2022; 40:918-931. [PMID: 35120750 DOI: 10.1016/j.tibtech.2022.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 01/05/2022] [Accepted: 01/05/2022] [Indexed: 12/18/2022]
Abstract
Microbial cell factories are becoming increasingly popular for the sustainable production of various chemicals. Metabolic engineering has led to the design of advanced cell factories; however, their long-term yield, titer, and productivity falter when scaled up and subjected to industrial conditions. This limitation arises from a lack of robustness - the ability to maintain a constant phenotype despite the perturbations of such processes. This review describes predictable and stochastic industrial perturbations as well as state-of-the-art technologies to counter process variability. Moreover, we distinguish robustness from tolerance and discuss the potential of single-cell studies for improving system robustness. Finally, we highlight ways of achieving consistent and comparable quantification of robustness that can guide the selection of strains for industrial bioprocesses.
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12
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Euler C, Mahadevan R. On the design principles of metabolic flux sensing. Biophys J 2022; 121:237-247. [PMID: 34951981 PMCID: PMC8790210 DOI: 10.1016/j.bpj.2021.12.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 10/01/2021] [Accepted: 12/16/2021] [Indexed: 01/21/2023] Open
Abstract
Metabolism is precisely coordinated, with the goal of balancing fluxes to maintain robust growth. However, coordinating fluxes requires information about rates, which can only be inferred through concentrations. While flux-sensitive metabolites have been reported, the design principles underlying such sensing have not been clearly elucidated. Here we use kinetic modeling to show that substrate concentrations of thermodynamically constrained reactions reflect upstream flux and therefore carry information about rates. Then we use untargeted multi-omic data from Escherichia coli and Saccharomyces cerevisiae to show that the concentrations of some metabolites in central carbon metabolism reflect fluxes as a result of thermodynamic constraints. We then establish, using 37 real concentration-flux relationships across both organisms, that in vivo ΔG∘≥-4 kJ/mol is the threshold above which substrates are likely to be sensitive to upstream flux(es).
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Affiliation(s)
- Christian Euler
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Radhakrishnan Mahadevan
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada; Institute for Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
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13
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Torello Pianale L, Rugbjerg P, Olsson L. Real-Time Monitoring of the Yeast Intracellular State During Bioprocesses With a Toolbox of Biosensors. Front Microbiol 2022; 12:802169. [PMID: 35069506 PMCID: PMC8776715 DOI: 10.3389/fmicb.2021.802169] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 12/16/2021] [Indexed: 12/19/2022] Open
Abstract
Industrial fermentation processes strive for high robustness to ensure optimal and consistent performance. Medium components, fermentation products, and physical perturbations may cause stress and lower performance. Cellular stress elicits a range of responses, whose extracellular manifestations have been extensively studied; whereas intracellular aspects remain poorly known due to lack of tools for real-time monitoring. Genetically encoded biosensors have emerged as promising tools and have been used to improve microbial productivity and tolerance toward industrially relevant stresses. Here, fluorescent biosensors able to sense the yeast intracellular environment (pH, ATP levels, oxidative stress, glycolytic flux, and ribosome production) were implemented into a versatile and easy-to-use toolbox. Marker-free and efficient genome integration at a conserved site on chromosome X of Saccharomyces cerevisiae strains and a commercial Saccharomyces boulardii strain was developed. Moreover, multiple biosensors were used to simultaneously monitor different intracellular parameters in a single cell. Even when combined together, the biosensors did not significantly affect key physiological parameters, such as specific growth rate and product yields. Activation and response of each biosensor and their interconnection were assessed using an advanced micro-cultivation system. Finally, the toolbox was used to screen cell behavior in a synthetic lignocellulosic hydrolysate that mimicked harsh industrial substrates, revealing differences in the oxidative stress response between laboratory (CEN.PK113-7D) and industrial (Ethanol Red) S. cerevisiae strains. In summary, the toolbox will allow both the exploration of yeast diversity and physiological responses in natural and complex industrial conditions, as well as the possibility to monitor production processes.
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Affiliation(s)
- Luca Torello Pianale
- Industrial Biotechnology Division, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Peter Rugbjerg
- Industrial Biotechnology Division, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
- Enduro Genetics ApS, Copenhagen, Denmark
| | - Lisbeth Olsson
- Industrial Biotechnology Division, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
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14
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Karloff DB, Heemstra JM. Sweet sensation: Developing a single-cell fluorescent reporter of glycolytic heterogeneity. Cell Chem Biol 2021; 28:1539-1541. [PMID: 34798034 DOI: 10.1016/j.chembiol.2021.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Conversion of in vitro selected aptamers into functional metabolic sensors is hampered by reduced in vivo aptamer binding and limited tunability of cellular metabolite levels. In this issue of Cell Chemical Biology, Ortega et al. (2021) construct RNA sensors of fructose-6-bisphosphate (FBP) that report on metabolite levels within single yeast cells.
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Affiliation(s)
- Diane B Karloff
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Jennifer M Heemstra
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA; Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332, USA.
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Sanford AA, Rangel AE, Feagin TA, Lowery RG, Argueta-Gonzalez HS, Heemstra JM. RE-SELEX: restriction enzyme-based evolution of structure-switching aptamer biosensors. Chem Sci 2021; 12:11692-11702. [PMID: 34659704 PMCID: PMC8442683 DOI: 10.1039/d1sc02715h] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 07/23/2021] [Indexed: 11/21/2022] Open
Abstract
Aptamers are widely employed as recognition elements in small molecule biosensors due to their ability to recognize small molecule targets with high affinity and selectivity. Structure-switching aptamers are particularly promising for biosensing applications because target-induced conformational change can be directly linked to a functional output. However, traditional evolution methods do not select for the significant conformational change needed to create structure-switching biosensors. Modified selection methods have been described to select for structure-switching architectures, but these remain limited by the need for immobilization. Herein we describe the first homogenous, structure-switching aptamer selection that directly reports on biosensor capacity for the target. We exploit the activity of restriction enzymes to isolate aptamer candidates that undergo target-induced displacement of a short complementary strand. As an initial demonstration of the utility of this approach, we performed selection against kanamycin A. Four enriched candidate sequences were successfully characterized as structure-switching biosensors for detection of kanamycin A. Optimization of biosensor conditions afforded facile detection of kanamycin A (90 μM to 10 mM) with high selectivity over three other aminoglycosides. This research demonstrates a general method to directly select for structure-switching biosensors and can be applied to a broad range of small-molecule targets.
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Affiliation(s)
- Aimee A Sanford
- Department of Chemistry, Emory University Atlanta Georgia 30322 USA
| | - Alexandra E Rangel
- Department of Chemistry, Center for Cell and Genome Science, University of Utah Salt Lake City Utah 84112 USA
| | - Trevor A Feagin
- Department of Chemistry, Center for Cell and Genome Science, University of Utah Salt Lake City Utah 84112 USA
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