1
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Barth KM, Hiller DA, Strobel SA. The Impact of Second-Shell Nucleotides on Ligand Specificity in Cyclic Dinucleotide Riboswitches. Biochemistry 2024. [PMID: 38329042 DOI: 10.1021/acs.biochem.3c00586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Ligand specificity is an essential requirement for all riboswitches. Some variant riboswitches utilize a common structural motif, yet through subtle sequence differences, they are able to selectively respond to different small molecule ligands and regulate downstream gene expression. These variants discriminate between structurally and chemically similar ligands. Crystal structures provide insight into how specificity is achieved. However, ligand specificity cannot always be explained solely by nucleotides in direct contact with the ligand. The cyclic dinucleotide variant family contains two classes, cyclic-di-GMP and cyclic-AMP-GMP riboswitches, that were distinguished based on the identity of a single nucleotide in contact with the ligand. Here we report a variant riboswitch with a mutation at a second ligand-contacting position that is promiscuous for both cyclic-di-GMP and cyclic-AMP-GMP despite a predicted preference for cyclic-AMP-GMP. A high-throughput mutational analysis, SMARTT, was used to quantitatively assess thousands of sites in the first- and second-shells of ligand contact for impacts on ligand specificity and promiscuity. In addition to nucleotides in direct ligand contact, nucleotides more distal from the binding site, within the J1/2 linker and the terminator helix, were identified that impact ligand specificity. These findings provide an example of how nucleotides outside the ligand binding pocket influence the riboswitch specificity. Moreover, these distal nucleotides could be used to predict promiscuous sequences.
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Affiliation(s)
- Kathryn M Barth
- Institute of Biomolecular Design and Discovery, Yale University, West Haven, Connecticut 06516, United States
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06510, United States
| | - David A Hiller
- Institute of Biomolecular Design and Discovery, Yale University, West Haven, Connecticut 06516, United States
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06510, United States
| | - Scott A Strobel
- Institute of Biomolecular Design and Discovery, Yale University, West Haven, Connecticut 06516, United States
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06510, United States
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2
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Ding Y, Gu L, Wang X, Zhang Z, Zhang H, Liu J. Affinity-Guided Coevolution of Aptamers for Guanine, Xanthine, Hypoxanthine, and Adenine. ACS Chem Biol 2024; 19:208-216. [PMID: 38194356 DOI: 10.1021/acschembio.3c00660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
The simultaneous evolution of multiple aptamers can drastically increase the speed of aptamer discovery. Most previous studies used the same concentration for different targets, leading to the dominance of the libraries by one or a few aptamers and a low success rate. To foster the best aptamers to grow independently in the sequence space, it is important to (1) use low target concentrations close to their dissociation constants and (2) stop at an early round before any sequence starts to dominate. In this study, we demonstrate this affinity-guided selection concept using the capture-SELEX method to isolate aptamers for four important purines: guanine (5 μM), xanthine (50 μM), hypoxanthine (10 μM), and adenine (10 μM). The round 9 library was split, and in round 10, the four targets were individually used to elute the binding sequences. Using thioflavin T fluorescence spectroscopy and isothermal titration calorimetry, we confirmed highly selective aptamers for xanthine, guanine, and adenine. These aptamers have Kd values below 1 μM and around 100-fold selectivity against most competing analytes, and they compare favorably with existing RNA aptamers and riboswitches. A separate selection was performed using hypoxanthine alone, and no selective aptamer was achieved, even with negative selection, explaining the lack of its aptamer in our mixed selection. This affinity-guided multiplex SELEX study offers fundamental insights into aptamer selection and provides high-quality aptamers for three important purines.
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Affiliation(s)
- Yuzhe Ding
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Lide Gu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Xiaoqin Wang
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Ziyu Zhang
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Hanxiao Zhang
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Juewen Liu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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3
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Bu F, Lin X, Liao W, Lu Z, He Y, Luo Y, Peng X, Li M, Huang Y, Chen X, Xiao B, Jiang J, Deng J, Huang J, Lin T, Miao Z, Huang L. Ribocentre-switch: a database of riboswitches. Nucleic Acids Res 2024; 52:D265-D272. [PMID: 37855663 PMCID: PMC10767811 DOI: 10.1093/nar/gkad891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 09/19/2023] [Accepted: 10/04/2023] [Indexed: 10/20/2023] Open
Abstract
Riboswitches are regulatory elements found in the untranslated regions (UTRs) of certain mRNA molecules. They typically comprise two distinct domains: an aptamer domain that can bind to specific small molecules, and an expression platform that controls gene expression. Riboswitches work by undergoing a conformational change upon binding to their specific ligand, thus activating or repressing the genes downstream. This mechanism allows gene expression regulation in response to metabolites or small molecules. To systematically summarise riboswitch structures and their related ligand binding functions, we present Ribocentre-switch, a comprehensive database of riboswitches, including the information as follows: sequences, structures, functions, ligand binding pockets and biological applications. It encompasses 56 riboswitches and 26 orphan riboswitches from over 430 references, with a total of 89 591 sequences. It serves as a good resource for comparing different riboswitches and facilitating the identification of potential riboswitch candidates. Therefore, it may facilitate the understanding of RNA structural conformational changes in response to ligand signaling. The database is publicly available at https://riboswitch.ribocentre.org.
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Affiliation(s)
- Fan Bu
- Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
- GMU-GIBH Joint School of Life Sciences, The Guangdong-Hong Kong-Macau Joint Laboratory for Cell Fate Regulation and Diseases,Guangzhou National Laboratory, Medical University, Guangzhou 510180, China
| | - Xiaowei Lin
- Department of Urology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Wenjian Liao
- Department of Urology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Zhizhong Lu
- School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, China
| | - Yuanlin He
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Yuhang Luo
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Xuemei Peng
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Mengxiao Li
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Yuanyin Huang
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Xiaoxue Chen
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Bowen Xiao
- GMU-GIBH Joint School of Life Sciences, The Guangdong-Hong Kong-Macau Joint Laboratory for Cell Fate Regulation and Diseases,Guangzhou National Laboratory, Medical University, Guangzhou 510180, China
| | - Jiuhong Jiang
- GMU-GIBH Joint School of Life Sciences, The Guangdong-Hong Kong-Macau Joint Laboratory for Cell Fate Regulation and Diseases,Guangzhou National Laboratory, Medical University, Guangzhou 510180, China
| | - Jie Deng
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Jian Huang
- Department of Urology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Tianxin Lin
- Department of Urology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
| | - Zhichao Miao
- Shanghai Key Laboratory of Anesthesiology and Brain Functional Modulation, Clinical Research Center for Anesthesiology and Perioperative Medicine, Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai 200434, China
- GMU-GIBH Joint School of Life Sciences, The Guangdong-Hong Kong-Macau Joint Laboratory for Cell Fate Regulation and Diseases,Guangzhou National Laboratory, Medical University, Guangzhou 510180, China
| | - Lin Huang
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, China
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Wu Y, Zhu L, Zhang Y, Xu W. Multidimensional Applications and Challenges of Riboswitches in Biosensing and Biotherapy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2304852. [PMID: 37658499 DOI: 10.1002/smll.202304852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 08/15/2023] [Indexed: 09/03/2023]
Abstract
Riboswitches have received significant attention over the last two decades for their multiple functionalities and great potential for applications in various fields. This article highlights and reviews the recent advances in biosensing and biotherapy. These fields involve a wide range of applications, such as food safety detection, environmental monitoring, metabolic engineering, live cell imaging, wearable biosensors, antibacterial drug targets, and gene therapy. The discovery, origin, and optimization of riboswitches are summarized to help readers better understand their multidimensional applications. Finally, this review discusses the multidimensional challenges and development of riboswitches in order to further expand their potential for novel applications.
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Affiliation(s)
- Yifan Wu
- Key Laboratory of Precision Nutrition and Food Quality, Beijing Laboratory for Food Quality and Safety, Department of Nutrition and Health, China Agricultural University, Beijing, 100191, China
| | - Longjiao Zhu
- Key Laboratory of Precision Nutrition and Food Quality, Beijing Laboratory for Food Quality and Safety, Department of Nutrition and Health, China Agricultural University, Beijing, 100191, China
| | - Yangzi Zhang
- Key Laboratory of Precision Nutrition and Food Quality, Beijing Laboratory for Food Quality and Safety, Department of Nutrition and Health, China Agricultural University, Beijing, 100191, China
| | - Wentao Xu
- Key Laboratory of Precision Nutrition and Food Quality, Beijing Laboratory for Food Quality and Safety, Department of Nutrition and Health, China Agricultural University, Beijing, 100191, China
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5
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Salvail H, Balaji A, Roth A, Breaker RR. A spermidine riboswitch class in bacteria exploits a close variant of an aptamer for the enzyme cofactor S-adenosylmethionine. Cell Rep 2023; 42:113571. [PMID: 38096053 PMCID: PMC10853860 DOI: 10.1016/j.celrep.2023.113571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 10/16/2023] [Accepted: 11/22/2023] [Indexed: 12/30/2023] Open
Abstract
Natural polyamines such as spermidine and spermine cations have characteristics that make them highly likely to be sensed by riboswitches, such as their general affinity to polyanionic RNA and their broad contributions to cell physiology. Despite previous claims that polyamine riboswitches exist, evidence of their biological functions has remained unconvincing. Here, we report that rare variants of bacterial S-adenosylmethionine-I (SAM-I) riboswitches reject SAM and have adapted to selectively sense spermidine. These spermidine-sensing riboswitch variants are associated with genes whose protein products are directly involved in the production of spermidine and other polyamines. Biochemical and genetic assays demonstrate that representatives of this riboswitch class robustly function as genetic "off" switches, wherein spermidine binding causes premature transcription termination to suppress the expression of polyamine biosynthetic genes. These findings confirm the existence of natural spermidine-sensing riboswitches in bacteria and expand the list of variant riboswitch classes that have adapted to bind different ligands.
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Affiliation(s)
- Hubert Salvail
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA
| | - Aparaajita Balaji
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA
| | - Adam Roth
- Howard Hughes Medical Institute, Yale University, New Haven, CT 06520-8103, USA
| | - Ronald R Breaker
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA; Howard Hughes Medical Institute, Yale University, New Haven, CT 06520-8103, USA; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103, USA.
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6
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Hamal Dhakal S, Kavita K, Panchapakesan SSS, Roth A, Breaker RR. 8-oxoguanine riboswitches in bacteria detect and respond to oxidative DNA damage. Proc Natl Acad Sci U S A 2023; 120:e2307854120. [PMID: 37748066 PMCID: PMC10556655 DOI: 10.1073/pnas.2307854120] [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: 05/10/2023] [Accepted: 08/25/2023] [Indexed: 09/27/2023] Open
Abstract
Riboswitches rely on structured aptamer domains to selectively sense their target ligands and regulate gene expression. However, some riboswitch aptamers in bacteria carry mutations in their otherwise strictly conserved binding pockets that change ligand specificities. The aptamer domain of a riboswitch class originally found to selectively sense guanine forms a three-stem junction that has since been observed to exploit numerous alterations in its ligand-binding pocket. These rare variants have modified their ligand specificities to sense other purines or purine derivatives, including adenine, 2'-deoxyguanosine (three classes), and xanthine. Herein, we report the characteristics of a rare variant that is narrowly distributed in the Paenibacillaceae family of bacteria. Known representatives are always associated with genes encoding 8-oxoguanine deaminase. As predicted from this gene association, these variant riboswitches tightly bind 8-oxoguanine (8-oxoG), strongly discriminate against other purine derivatives, and function as genetic "ON" switches. Following exposure of cells to certain oxidative stresses, a representative 8-oxoG riboswitch activates gene expression, likely caused by the accumulation of 8-oxoG due to oxidative damage to G nucleobases in DNA, RNA, and the nucleotide pool. Furthermore, an engineered version of the variant aptamer was prepared that exhibits specificity for 8-oxoadenine, further demonstrating that RNA aptamers can acquire mutations that expand their ability to detect and respond to oxidative damage.
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Affiliation(s)
- Siddhartha Hamal Dhakal
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT06511-8103
| | - Kumari Kavita
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT06511-8103
| | | | - Adam Roth
- HHMI, Yale University, New Haven, CT06511-8103
| | - Ronald R. Breaker
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT06511-8103
- HHMI, Yale University, New Haven, CT06511-8103
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT06511-8103
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7
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Abstract
Oxidative stress is an important and pervasive physical stress encountered by all kingdoms of life, including bacteria. In this review, we briefly describe the nature of oxidative stress, highlight well-characterized protein-based sensors (transcription factors) of reactive oxygen species that serve as standards for molecular sensors in oxidative stress, and describe molecular studies that have explored the potential of direct RNA sensitivity to oxidative stress. Finally, we describe the gaps in knowledge of RNA sensors-particularly regarding the chemical modification of RNA nucleobases. RNA sensors are poised to emerge as an essential layer of understanding and regulating dynamic biological pathways in oxidative stress responses in bacteria and, thus, also represent an important frontier of synthetic biology.
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Affiliation(s)
- Ryan Buchser
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas, USA;
| | - Phillip Sweet
- Integrative Life Sciences Program, University of Texas at Austin, Austin, Texas, USA
| | - Aparna Anantharaman
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas, USA;
| | - Lydia Contreras
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas, USA;
- Integrative Life Sciences Program, University of Texas at Austin, Austin, Texas, USA
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8
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Kavita K, Breaker RR. Discovering riboswitches: the past and the future. Trends Biochem Sci 2023; 48:119-141. [PMID: 36150954 PMCID: PMC10043782 DOI: 10.1016/j.tibs.2022.08.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 08/18/2022] [Accepted: 08/26/2022] [Indexed: 01/25/2023]
Abstract
Riboswitches are structured noncoding RNA domains used by many bacteria to monitor the concentrations of target ligands and regulate gene expression accordingly. In the past 20 years over 55 distinct classes of natural riboswitches have been discovered that selectively sense small molecules or elemental ions, and thousands more are predicted to exist. Evidence suggests that some riboswitches might be direct descendants of the RNA-based sensors and switches that were likely present in ancient organisms before the evolutionary emergence of proteins. We provide an overview of the current state of riboswitch research, focusing primarily on the discovery of riboswitches, and speculate on the major challenges facing researchers in the field.
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Affiliation(s)
- Kumari Kavita
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA
| | - Ronald R Breaker
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA; Howard Hughes Medical Institute, Yale University, New Haven, CT 06520-8103, USA; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103, USA.
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9
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Mohsen MG, Midy MK, Balaji A, Breaker R. Exploiting natural riboswitches for aptamer engineering and validation. Nucleic Acids Res 2023; 51:966-981. [PMID: 36617976 PMCID: PMC9881172 DOI: 10.1093/nar/gkac1218] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 11/04/2022] [Accepted: 12/09/2022] [Indexed: 01/10/2023] Open
Abstract
Over the past three decades, researchers have found that some engineered aptamers can be made to work well in test tubes but that these same aptamers might fail to function in cells. To help address this problem, we developed the 'Graftamer' approach, an experimental platform that exploits the architecture of a natural riboswitch to enhance in vitro aptamer selection and accelerate in vivo testing. Starting with combinatorial RNA pools that contain structural features of a guanine riboswitch aptamer interspersed with regions of random sequence, we performed multiplexed in vitro selection with a collection of small molecules. This effort yielded aptamers for quinine, guanine, and caffeine that appear to maintain structural features of the natural guanine riboswitch aptamer. Quinine and caffeine aptamers were each grafted onto a natural guanine riboswitch expression platform and reporter gene expression was monitored to determine that these aptamers function in cells. Additionally, we determined the secondary structure features and survival mechanism of a class of RNA sequences that evade the intended selection strategy, providing insight into improving this approach for future efforts. These results demonstrate that the Graftamer strategy described herein represents a convenient and straightforward approach to develop aptamers and validate their in vivo function.
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Affiliation(s)
- Michael G Mohsen
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA,Howard Hughes Medical Institute, Yale University, New Haven, CT 06511, USA
| | - Matthew K Midy
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Aparaajita Balaji
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA
| | - Ronald R Breaker
- To whom correspondence should be addressed. Tel: +1 203 432 9389; Fax: +1 203 432 6161;
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10
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Lenkeit F, Eckert I, Sinn M, Hauth F, Hartig JS, Weinberg Z. A variant of guanidine-IV riboswitches exhibits evidence of a distinct ligand specificity. RNA Biol 2023; 20:10-19. [PMID: 36548032 PMCID: PMC9788692 DOI: 10.1080/15476286.2022.2160562] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Riboswitches are regulatory RNAs that specifically bind a small molecule or ion. Like metabolite-binding proteins, riboswitches can evolve new ligand specificities, and some examples of this phenomenon have been validated. As part of work based on comparative genomics to discover novel riboswitches, we encountered a candidate riboswitch with striking similarities to the recently identified guanidine-IV riboswitch. This candidate riboswitch, the Gd4v motif, is predicted in four distinct bacterial phyla, thus almost as widespread as the guanidine-IV riboswitch. Bioinformatic and experimental analysis suggest that the Gd4v motif is a riboswitch that binds a ligand other than guanidine. It is found associated with gene classes that differ from genes regulated by confirmed guanidine riboswitches. In inline-probing assays, we showed that free guanidine binds only weakly to one of the tested sequences of the variant. Further tested compounds did not show binding, attenuation of transcription termination, or activation of a genetic reporter construct. We characterized an N-acetyltransferase frequently associated with the Gd4v motif and compared its substrate preference to an N-acetyltransferase that occurs under control of guanidine-IV riboswitches. The substrates of this Gd4v-motif-associated enzyme did not show activity for Gd4v RNA binding or transcription termination. Hence, the ligand of the candidate riboswitch motif remains unidentified. The variant RNA motif is predominantly found in gut metagenome sequences, hinting at a ligand that is highly relevant in this environment. This finding is a first step to determining the identity of this unknown ligand, and understanding how guanidine-IV-riboswitch-like structures can evolve to bind different ligands.
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Affiliation(s)
- Felina Lenkeit
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany
| | - Iris Eckert
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107Leipzig, Germany
| | - Malte Sinn
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany
| | - Franziskus Hauth
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany
| | - Jörg S. Hartig
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany,CONTACT Jörg S. Hartig
| | - Zasha Weinberg
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107Leipzig, Germany,Zasha Weinberg Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107Leipzig, Germany
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11
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Giarimoglou N, Kouvela A, Maniatis A, Papakyriakou A, Zhang J, Stamatopoulou V, Stathopoulos C. A Riboswitch-Driven Era of New Antibacterials. Antibiotics (Basel) 2022; 11:antibiotics11091243. [PMID: 36140022 PMCID: PMC9495366 DOI: 10.3390/antibiotics11091243] [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: 08/11/2022] [Revised: 09/01/2022] [Accepted: 09/08/2022] [Indexed: 11/26/2022] Open
Abstract
Riboswitches are structured non-coding RNAs found in the 5′ UTR of important genes for bacterial metabolism, virulence and survival. Upon the binding of specific ligands that can vary from simple ions to complex molecules such as nucleotides and tRNAs, riboswitches change their local and global mRNA conformations to affect downstream transcription or translation. Due to their dynamic nature and central regulatory role in bacterial metabolism, riboswitches have been exploited as novel RNA-based targets for the development of new generation antibacterials that can overcome drug-resistance problems. During recent years, several important riboswitch structures from many bacterial representatives, including several prominent human pathogens, have shown that riboswitches are ideal RNA targets for new compounds that can interfere with their structure and function, exhibiting much reduced resistance over time. Most interestingly, mainstream antibiotics that target the ribosome have been shown to effectively modulate the regulatory behavior and capacity of several riboswitches, both in vivo and in vitro, emphasizing the need for more in-depth studies and biological evaluation of new antibiotics. Herein, we summarize the currently known compounds that target several main riboswitches and discuss the role of mainstream antibiotics as modulators of T-box riboswitches, in the dawn of an era of novel inhibitors that target important bacterial regulatory RNAs.
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Affiliation(s)
- Nikoleta Giarimoglou
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Adamantia Kouvela
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Alexandros Maniatis
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Athanasios Papakyriakou
- Institute of Biosciences & Applications, National Centre for Scientific Research “Demokritos”, Ag. Paraskevi, 15341 Athens, Greece
| | - Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | | | - Constantinos Stathopoulos
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
- Correspondence: ; Tel.: +30-2610-997932
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