1
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Zhou Y, Jiang Y, Chen SJ. SPRank─A Knowledge-Based Scoring Function for RNA-Ligand Pose Prediction and Virtual Screening. J Chem Theory Comput 2024. [PMID: 39150889 DOI: 10.1021/acs.jctc.4c00681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2024]
Abstract
The growing interest in RNA-targeted drugs underscores the need for computational modeling of interactions between RNA molecules and small compounds. Having a reliable scoring function for RNA-ligand interactions is essential for effective computational drug screening. An ideal scoring function should not only predict the native pose for ligand binding but also rank the affinity of the binding for different ligands. However, existing scoring functions are primarily designed to predict the native binding modes for a given RNA-ligand pair and have not been thoroughly assessed for virtual screening purposes. In this paper, we introduce SPRank, a combination of machine-learning and knowledge-based scoring functions developed through a weighted iterative approach, specifically designed to tackle both binding mode prediction and virtual screening challenges. Our approach incorporates third-party docking software, such as rDock and AutoDock Vina, to sample flexible ligands against an ensemble of RNA structures, capturing the conformational flexibility of both the RNA and the ligand. Through rigorous testing, SPRank demonstrates improved performance compared to the tested scoring functions across four test sets comprising 122, 42, 55, and 71 nucleic acid-ligand complexes. Furthermore, SPRank exhibits improved performance in virtual screening tests targeting the HIV-1 TAR ensemble, which highlights its advantage in drug discovery. These results underscore the advantages of SPRank as a potentially promising tool for the RNA-targeted drug design. The source code of SPRank and the data sets are freely accessible at https://github.com/Vfold-RNA/SPRank.
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Affiliation(s)
- Yuanzhe Zhou
- Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, Missouri 65211-7010, United States
| | - Yangwei Jiang
- Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, Missouri 65211-7010, United States
| | - Shi-Jie Chen
- Department of Physics and Astronomy, Department of Biochemistry, Institute of Data Sciences and Informatics, University of Missouri-Columbia, Columbia, Missouri 65211-7010, United States
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2
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Zhou Y, Chen SJ. Advances in machine-learning approaches to RNA-targeted drug design. ARTIFICIAL INTELLIGENCE CHEMISTRY 2024; 2:100053. [PMID: 38434217 PMCID: PMC10904028 DOI: 10.1016/j.aichem.2024.100053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
RNA molecules play multifaceted functional and regulatory roles within cells and have garnered significant attention in recent years as promising therapeutic targets. With remarkable successes achieved by artificial intelligence (AI) in different fields such as computer vision and natural language processing, there is a growing imperative to harness AI's potential in computer-aided drug design (CADD) to discover novel drug compounds that target RNA. Although machine-learning (ML) approaches have been widely adopted in the discovery of small molecules targeting proteins, the application of ML approaches to model interactions between RNA and small molecule is still in its infancy. Compared to protein-targeted drug discovery, the major challenges in ML-based RNA-targeted drug discovery stem from the scarcity of available data resources. With the growing interest and the development of curated databases focusing on interactions between RNA and small molecule, the field anticipates a rapid growth and the opening of a new avenue for disease treatment. In this review, we aim to provide an overview of recent advancements in computationally modeling RNA-small molecule interactions within the context of RNA-targeted drug discovery, with a particular emphasis on methodologies employing ML techniques.
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Affiliation(s)
- Yuanzhe Zhou
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211-7010, USA
| | - Shi-Jie Chen
- Department of Physics and Astronomy, Department of Biochemistry, Institute of Data Sciences and Informatics, University of Missouri, Columbia, MO 65211-7010, USA
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3
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Hertz LM, White EN, Kuznedelov K, Cheng L, Yu AM, Kakkaramadam R, Severinov K, Chen A, Lucks J. The effect of pseudoknot base pairing on cotranscriptional structural switching of the fluoride riboswitch. Nucleic Acids Res 2024; 52:4466-4482. [PMID: 38567721 PMCID: PMC11077080 DOI: 10.1093/nar/gkae231] [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: 12/04/2023] [Revised: 02/17/2024] [Accepted: 03/20/2024] [Indexed: 04/16/2024] Open
Abstract
A central question in biology is how RNA sequence changes influence dynamic conformational changes during cotranscriptional folding. Here we investigated this question through the study of transcriptional fluoride riboswitches, non-coding RNAs that sense the fluoride anion through the coordinated folding and rearrangement of a pseudoknotted aptamer domain and a downstream intrinsic terminator expression platform. Using a combination of Escherichia coli RNA polymerase in vitro transcription and cellular gene expression assays, we characterized the function of mesophilic and thermophilic fluoride riboswitch variants. We showed that only variants containing the mesophilic pseudoknot function at 37°C. We next systematically varied the pseudoknot sequence and found that a single wobble base pair is critical for function. Characterizing thermophilic variants at 65°C through Thermus aquaticus RNA polymerase in vitro transcription showed the importance of this wobble pair for function even at elevated temperatures. Finally, we performed all-atom molecular dynamics simulations which supported the experimental findings, visualized the RNA structure switching process, and provided insight into the important role of magnesium ions. Together these studies provide deeper insights into the role of riboswitch sequence in influencing folding and function that will be important for understanding of RNA-based gene regulation and for synthetic biology applications.
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Affiliation(s)
- Laura M Hertz
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA
| | - Elise N White
- Department of Chemistry and the RNA Institute, University at Albany, Albany, NY 12222, USA
| | | | - Luyi Cheng
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA
| | - Angela M Yu
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA 98195, USA
| | - Rivaan Kakkaramadam
- Department of Chemistry and the RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Konstantin Severinov
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ 08854, USA
| | - Alan Chen
- Department of Chemistry and the RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Julius B Lucks
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
- Center for Synthetic Biology, Northwestern University, Evanston, IL 60208, USA
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4
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Kaur J, Sharma A, Mundlia P, Sood V, Pandey A, Singh G, Barnwal RP. RNA-Small-Molecule Interaction: Challenging the "Undruggable" Tag. J Med Chem 2024. [PMID: 38498010 DOI: 10.1021/acs.jmedchem.3c01354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
RNA targeting, specifically with small molecules, is a relatively new and rapidly emerging avenue with the promise to expand the target space in the drug discovery field. From being "disregarded" as an "undruggable" messenger molecule to FDA approval of an RNA-targeting small-molecule drug Risdiplam, a radical change in perspective toward RNA has been observed in the past decade. RNAs serve important regulatory functions beyond canonical protein synthesis, and their dysregulation has been reported in many diseases. A deeper understanding of RNA biology reveals that RNA molecules can adopt a variety of structures, carrying defined binding pockets that can accommodate small-molecule drugs. Due to its functional diversity and structural complexity, RNA can be perceived as a prospective target for therapeutic intervention. This perspective highlights the proof of concept of RNA-small-molecule interactions, exemplified by targeting of various transcripts with functional modulators. The advent of RNA-oriented knowledge would help expedite drug discovery.
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Affiliation(s)
- Jaskirat Kaur
- Department of Biophysics, Panjab University, Chandigarh 160014, India
| | - Akanksha Sharma
- Department of Biophysics, Panjab University, Chandigarh 160014, India
- University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh 160014, India
| | - Poonam Mundlia
- Department of Biophysics, Panjab University, Chandigarh 160014, India
| | - Vikas Sood
- Department of Biochemistry, Jamia Hamdard, New Delhi 110062, India
| | - Ankur Pandey
- Department of Chemistry, Panjab University, Chandigarh 160014, India
| | - Gurpal Singh
- University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh 160014, India
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5
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Olenginski LT, Spradlin SF, Batey RT. Flipping the script: Understanding riboswitches from an alternative perspective. J Biol Chem 2024; 300:105730. [PMID: 38336293 PMCID: PMC10907184 DOI: 10.1016/j.jbc.2024.105730] [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: 09/30/2023] [Revised: 01/14/2024] [Accepted: 01/19/2024] [Indexed: 02/12/2024] Open
Abstract
Riboswitches are broadly distributed regulatory elements most frequently found in the 5'-leader sequence of bacterial mRNAs that regulate gene expression in response to the binding of a small molecule effector. The occupancy status of the ligand-binding aptamer domain manipulates downstream information in the message that instructs the expression machinery. Currently, there are over 55 validated riboswitch classes, where each class is defined based on the identity of the ligand it binds and/or sequence and structure conservation patterns within the aptamer domain. This classification reflects an "aptamer-centric" perspective that dominates our understanding of riboswitches. In this review, we propose a conceptual framework that groups riboswitches based on the mechanism by which RNA manipulates information directly instructing the expression machinery. This scheme does not replace the established aptamer domain-based classification of riboswitches but rather serves to facilitate hypothesis-driven investigation of riboswitch regulatory mechanisms. Based on current bioinformatic, structural, and biochemical studies of a broad spectrum of riboswitches, we propose three major mechanistic groups: (1) "direct occlusion", (2) "interdomain docking", and (3) "strand exchange". We discuss the defining features of each group, present representative examples of riboswitches from each group, and illustrate how these RNAs couple small molecule binding to gene regulation. While mechanistic studies of the occlusion and docking groups have yielded compelling models for how these riboswitches function, much less is known about strand exchange processes. To conclude, we outline the limitations of our mechanism-based conceptual framework and discuss how critical information within riboswitch expression platforms can inform gene regulation.
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Affiliation(s)
| | | | - Robert T Batey
- Department of Biochemistry, University of Colorado, Boulder, Colorado, USA.
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6
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Tidwell ED, Kilde IR, Leskaj S, Koutmos M. Fluorescent Ligand Equilibrium Displacement: A High-Throughput Method for Identification of FMN Riboswitch-Binding Small Molecules. Int J Mol Sci 2024; 25:735. [PMID: 38255809 PMCID: PMC11154562 DOI: 10.3390/ijms25020735] [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: 10/25/2023] [Revised: 12/27/2023] [Accepted: 12/28/2023] [Indexed: 01/24/2024] Open
Abstract
Antibiotic resistance remains a pressing global concern, with most antibiotics targeting the bacterial ribosome or a limited range of proteins. One class of underexplored antibiotic targets is bacterial riboswitches, structured RNA elements that regulate key biosynthetic pathways by binding a specific ligand. We developed a methodology termed Fluorescent Ligand Equilibrium Displacement (FLED) to rapidly discover small molecules that bind the flavin mononucleotide (FMN) riboswitch. FLED leverages intrinsically fluorescent FMN and the quenching effect on RNA binding to create a label-free, in vitro method to identify compounds that can bind the apo population of riboswitch in a system at equilibrium. The response difference between known riboswitch ligands and controls demonstrates the robustness of the method for high-throughput screening. An existing drug discovery library that was screened using FLED resulted in a final hit rate of 0.67%. The concentration response of each hit was determined and revealed a variety of approximate effective concentration values. Our preliminary screening data support the use of FLED to identify small molecules for medicinal chemistry development as FMN riboswitch-targeted antibiotic compounds. This robust, label-free, and cell-free method offers a strong alternative to other riboswitch screening methods and can be adapted to a variety of laboratory setups.
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Affiliation(s)
| | - Ingrid R. Kilde
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Suada Leskaj
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Markos Koutmos
- Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA;
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA;
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA;
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7
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Hertz LM, White EN, Kuznedelov K, Cheng L, Yu AM, Kakkaramadam R, Severinov K, Chen A, Lucks JB. The Effect of Pseudoknot Base Pairing on Cotranscriptional Structural Switching of the Fluoride Riboswitch. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.05.570056. [PMID: 38106011 PMCID: PMC10723315 DOI: 10.1101/2023.12.05.570056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
A central question in biology is how RNA sequence changes influence dynamic conformational changes during cotranscriptional folding. Here we investigated this question through the study of transcriptional fluoride riboswitches, non-coding RNAs that sense the fluoride anion through the coordinated folding and rearrangement of a pseudoknotted aptamer domain and a downstream intrinsic terminator expression platform. Using a combination of E. coli RNA polymerase in vitro transcription and cellular gene expression assays, we characterized the function of mesophilic and thermophilic fluoride riboswitch variants. We showed that only variants containing the mesophilic pseudoknot function at 37 °C. We next systematically varied the pseudoknot sequence and found that a single wobble base pair is critical for function. Characterizing thermophilic variants at 65 °C through Thermus aquaticus RNA polymerase in vitro transcription showed the importance of this wobble pair for function even at elevated temperatures. Finally, we performed all-atom molecular dynamics simulations which supported the experimental findings, visualized the RNA structure switching process, and provided insight into the important role of magnesium ions. Together these studies provide deeper insights into the role of riboswitch sequence in influencing folding and function that will be important for understanding of RNA-based gene regulation and for synthetic biology applications.
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Affiliation(s)
- Laura M Hertz
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA
| | - Elise N White
- Department of Chemistry and the RNA Institute, University at Albany, Albany, NY 12222, USA
| | | | - Luyi Cheng
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA
| | - Angela M Yu
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA 98195, USA
| | - Rivaan Kakkaramadam
- Department of Chemistry and the RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Konstantin Severinov
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ 08854, USA
| | - Alan Chen
- Department of Chemistry and the RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Julius B Lucks
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL 60208, USA
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
- Center for Synthetic Biology, Northwestern University, Evanston, IL 60208, USA
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8
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Gnanagobal H, Cao T, Hossain A, Vasquez I, Chakraborty S, Chukwu-Osazuwa J, Boyce D, Espinoza MJ, García-Angulo VA, Santander J. Role of riboflavin biosynthesis gene duplication and transporter in Aeromonas salmonicida virulence in marine teleost fish. Virulence 2023; 14:2187025. [PMID: 36895132 PMCID: PMC10012899 DOI: 10.1080/21505594.2023.2187025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023] Open
Abstract
Active flavins derived from riboflavin (vitamin B2) are essential for life. Bacteria biosynthesize riboflavin or scavenge it through uptake systems, and both mechanisms may be present. Because of riboflavin's critical importance, the redundancy of riboflavin biosynthetic pathway (RBP) genes might be present. Aeromonas salmonicida, the aetiological agent of furunculosis, is a pathogen of freshwater and marine fish, and its riboflavin pathways have not been studied. This study characterized the A. salmonicida riboflavin provision pathways. Homology search and transcriptional orchestration analysis showed that A. salmonicida has a main riboflavin biosynthetic operon that includes ribD, ribE1, ribBA, and ribH genes. Outside the main operon, putative duplicated genes ribA, ribB and ribE, and a ribN riboflavin importer encoding gene, were found. Monocistronic mRNA ribA, ribB and ribE2 encode for their corresponding functional riboflavin biosynthetic enzyme. While the product of ribBA conserved the RibB function, it lacked the RibA function. Likewise, ribN encodes a functional riboflavin importer. Transcriptomics analysis indicated that external riboflavin affected the expression of a relatively small number of genes, including a few involved in iron metabolism. ribB was downregulated in response to external riboflavin, suggesting negative feedback. Deletion of ribA, ribB and ribE1 showed that these genes are required for A. salmonicida riboflavin biosynthesis and virulence in Atlantic lumpfish (Cyclopterus lumpus). A. salmonicida riboflavin auxotrophic attenuated mutants conferred low protection to lumpfish against virulent A. salmonicida. Overall, A. salmonicida has multiple riboflavin endowment forms, and duplicated riboflavin provision genes are critical for A. salmonicida infection.
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Affiliation(s)
- Hajarooba Gnanagobal
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St John's, Canada
| | - Trung Cao
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St John's, Canada
| | - Ahmed Hossain
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St John's, Canada
| | - Ignacio Vasquez
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St John's, Canada
| | - Setu Chakraborty
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St John's, Canada
| | - Joy Chukwu-Osazuwa
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St John's, Canada
| | - Danny Boyce
- The Dr. Joe Brown Aquatic Research Building (JBARB), Ocean Sciences Centre, Memorial University of Newfoundland, St John's, Canada
| | - María Jesus Espinoza
- Microbiology and Mycology Program, Institute of Biomedical Sciences, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Víctor Antonio García-Angulo
- Microbiology and Mycology Program, Institute of Biomedical Sciences, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Javier Santander
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St John's, Canada
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9
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Pavlova N, Traykovska M, Penchovsky R. Targeting FMN, TPP, SAM-I, and glmS Riboswitches with Chimeric Antisense Oligonucleotides for Completely Rational Antibacterial Drug Development. Antibiotics (Basel) 2023; 12:1607. [PMID: 37998809 PMCID: PMC10668854 DOI: 10.3390/antibiotics12111607] [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: 10/17/2023] [Revised: 11/05/2023] [Accepted: 11/07/2023] [Indexed: 11/25/2023] Open
Abstract
Antimicrobial drug resistance has emerged as a significant challenge in contemporary medicine due to the proliferation of numerous bacterial strains resistant to all existing antibiotics. Meanwhile, riboswitches have emerged as promising targets for discovering antibacterial drugs. Riboswitches are regulatory elements in certain bacterial mRNAs that can bind to specific molecules and control gene expression via transcriptional termination, prevention of translation, or mRNA destabilization. By targeting riboswitches, we aim to develop innovative strategies to combat antibiotic-resistant bacteria and enhance the efficacy of antibacterial treatments. This convergence of challenges and opportunities underscores the ongoing quest to revolutionize medical approaches against evolving bacterial threats. For the first time, this innovative review describes the rational design and applications of chimeric antisense oligonucleotides as antibacterial agents targeting four riboswitches selected based on genome-wide bioinformatic analyses. The antisense oligonucleotides are coupled with the cell-penetrating oligopeptide pVEC, which penetrates Gram-positive and Gram-negative bacteria and specifically targets glmS, FMN, TPP, and SAM-I riboswitches in Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli. The average antibiotic dosage of antisense oligonucleotides that inhibits 80% of bacterial growth is around 700 nM (4.5 μg/mL). Antisense oligonucleotides do not exhibit toxicity in human cell lines at this concentration. The results demonstrate that these riboswitches are suitable targets for antibacterial drug development using antisense oligonucleotide technology. The approach is fully rational because selecting suitable riboswitch targets and designing ASOs that target them are based on predefined criteria. The approach can be used to develop narrow or broad-spectrum antibiotics against multidrug-resistant bacterial strains for a short time. The approach is easily adaptive to new resistance using targeting NGS technology.
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Affiliation(s)
| | | | - Robert Penchovsky
- Laboratory of Synthetic Biology and Bioinformatics, Faculty of Biology, Sofia University “St. Kliment Ohridski”, 8 Dragan Tzankov Blvd., 1164 Sofia, Bulgaria
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10
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Ding J, Deme J, Stagno JR, Yu P, Lea S, Wang YX. Capturing heterogeneous conformers of cobalamin riboswitch by cryo-EM. Nucleic Acids Res 2023; 51:9952-9960. [PMID: 37534568 PMCID: PMC10570017 DOI: 10.1093/nar/gkad651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 07/13/2023] [Accepted: 07/27/2023] [Indexed: 08/04/2023] Open
Abstract
RNA conformational heterogeneity often hampers its high-resolution structure determination, especially for large and flexible RNAs devoid of stabilizing proteins or ligands. The adenosylcobalamin riboswitch exhibits heterogeneous conformations under 1 mM Mg2+ concentration and ligand binding reduces conformational flexibility. Among all conformers, we determined one apo (5.3 Å) and four holo cryo-electron microscopy structures (overall 3.0-3.5 Å, binding pocket 2.9-3.2 Å). The holo dimers exhibit global motions of helical twisting and bending around the dimer interface. A backbone comparison of the apo and holo states reveals a large structural difference in the P6 extension position. The central strand of the binding pocket, junction 6/3, changes from an 'S'- to a 'U'-shaped conformation to accommodate ligand. Furthermore, the binding pocket can partially form under 1 mM Mg2+ and fully form under 10 mM Mg2+ within the bound-like structure in the absence of ligand. Our results not only demonstrate the stabilizing ligand-induced conformational changes in and around the binding pocket but may also provide further insight into the role of the P6 extension in ligand binding and selectivity.
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Affiliation(s)
- Jienyu Ding
- Protein–Nucleic Acid Interaction Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Justin C Deme
- Molecular Basis of Disease Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Jason R Stagno
- Protein–Nucleic Acid Interaction Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Ping Yu
- Protein–Nucleic Acid Interaction Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Susan M Lea
- Molecular Basis of Disease Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Yun-Xing Wang
- Protein–Nucleic Acid Interaction Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
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11
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Amadei F, Reichenbach M, Gallo S, Sigel RKO. The structural features of the ligand-free moaA riboswitch and its ion-dependent folding. J Inorg Biochem 2023; 242:112153. [PMID: 36774787 DOI: 10.1016/j.jinorgbio.2023.112153] [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: 10/10/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 02/02/2023]
Abstract
Riboswitches are structural elements of mRNA involved in the regulation of gene expression by responding to specific cellular metabolites. To fulfil their regulatory function, riboswitches prefold into an active state, the so-called binding competent form, that guarantees metabolite binding and allows a consecutive refolding of the RNA. Here, we describe the folding pathway to the binding competent form as well as the ligand free structure of the moaA riboswitch of E. coli. This RNA proposedly responds to the molybdenum cofactor (Moco), a highly oxygen-sensitive metabolite, essential in the carbon and sulfur cycles of eukaryotes. K+- and Mg2+-dependent footprinting assays and spectroscopic investigations show a high degree of structure formation of this RNA already at very low ion-concentrations. Mg2+ facilitates additionally a general compaction of the riboswitch towards its proposed active structure. We show that this fold agrees with the earlier suggested secondary structure which included also a long-range tetraloop/tetraloop-receptor like interaction. Metal ion cleavage assays revealed specific Mg2+-binding pockets within the moaA riboswitch. These Mg2+ binding pockets are good indicators for the potential Moco binding site, since in riboswitches, Mg2+ was shown to be necessary to bind phosphate-carrying metabolites. The importance of the phosphate and of other functional groups of Moco is highlighted by binding assays with tetrahydrobiopterin, the reduced and oxygen-sensitive core moiety of Moco. We demonstrate that the general molecular shape of pterin by its own is insufficient for the recognition by the riboswitch.
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Affiliation(s)
- Fabio Amadei
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - María Reichenbach
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Sofia Gallo
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
| | - Roland K O Sigel
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
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12
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Du Y, Zhang X, Zhang H, Zhu R, Zhao Z, Han J, Zhang D, Zhang X, Zhang X, Pan X, You J, Rao Z. Direct evolution of riboflavin kinase significantly enhance flavin mononucleotide synthesis by design and optimization of flavin mononucleotide riboswitch. BIORESOURCE TECHNOLOGY 2023; 381:128774. [PMID: 36822556 DOI: 10.1016/j.biortech.2023.128774] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/17/2023] [Accepted: 02/19/2023] [Indexed: 05/08/2023]
Abstract
Flavin mononucleotide (FMN) is the active form of riboflavin. It has a wide range of application scenarios in the pharmaceutical and food additives. However, there are limitations in selecting generic high-throughput screening platforms that improve the properties of enzymes. First, the biosensor in response to FMN concentration was constructed using the FMN riboswitch and confirmed the function of this sensor. Next, the FMN binding site of the sensor was saturated with a mutation that increased its fluorescence range by approximately 127%. Then, the biosensor and the base editing system based on T7RNAP were combined to construct a platform for rapid mutation and screening of riboflavin kinase gene ribC mutants. The mutants screened using this platform increased the yield of FMN by 8-fold. These results indicate that the high-throughput screening platform can rapidly and effectively improve the activity of target enzymes, and provide a new route for screening industrial enzymes.
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Affiliation(s)
- Yuxuan Du
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Xinyi Zhang
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Hengwei Zhang
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Rongshuai Zhu
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Zhenqiang Zhao
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Jin Han
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Di Zhang
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Xiaoling Zhang
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Xian Zhang
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Xuewei Pan
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Jiajia You
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Zhiming Rao
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, China.
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13
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Ali Z, Goyal A, Jhunjhunwala A, Mitra A, Trant JF, Sharma P. Structural and Energetic Features of Base-Base Stacking Contacts in RNA. J Chem Inf Model 2023; 63:655-669. [PMID: 36635230 DOI: 10.1021/acs.jcim.2c01116] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nucleobase π-π stacking is one of the crucial organizing interactions within three-dimensional (3D) RNA architectures. Characterizing the structural variability of these contacts in RNA crystal structures will help delineate their subtleties and their role in determining function. This analysis of different stacking geometries found in RNA X-ray crystal structures is the largest such survey to date; coupled with quantum-mechanical calculations on typical representatives of each possible stacking arrangement, we determined the distribution of stacking interaction energies. A total of 1,735,481 stacking contacts, spanning 359 of the 384 theoretically possible distinct stacking geometries, were identified. Our analysis reveals preferential occurrences of specific consecutive stacking arrangements in certain regions of RNA architectures. Quantum chemical calculations suggest that 88 of the 359 contacts possess intrinsically stable stacking geometries, whereas the remaining stacks require the RNA backbone or surrounding macromolecular environment to force their formation and maintain their stability. Our systematic analysis of π-π stacks in RNA highlights trends in the occurrence and localization of these noncovalent interactions and may help better understand the structural intricacies of functional RNA-based molecular architectures.
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Affiliation(s)
- Zakir Ali
- Computational Biochemistry Laboratory, Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University, Chandigarh160014, India
| | - Ambika Goyal
- Computational Biochemistry Laboratory, Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University, Chandigarh160014, India
| | - Ayush Jhunjhunwala
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, Gachibowli, Hyderabad, Telangana500032, India
| | - Abhijit Mitra
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, Gachibowli, Hyderabad, Telangana500032, India
| | - John F Trant
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, OntarioN9B 3P4, Canada
- Binary Star Research Services, LaSalle, OntarioN9J 3X8, Canada
| | - Purshotam Sharma
- Computational Biochemistry Laboratory, Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University, Chandigarh160014, India
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, OntarioN9B 3P4, Canada
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14
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Childs-Disney JL, Yang X, Gibaut QMR, Tong Y, Batey RT, Disney MD. Targeting RNA structures with small molecules. Nat Rev Drug Discov 2022; 21:736-762. [PMID: 35941229 PMCID: PMC9360655 DOI: 10.1038/s41573-022-00521-4] [Citation(s) in RCA: 159] [Impact Index Per Article: 79.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/17/2022] [Indexed: 01/07/2023]
Abstract
RNA adopts 3D structures that confer varied functional roles in human biology and dysfunction in disease. Approaches to therapeutically target RNA structures with small molecules are being actively pursued, aided by key advances in the field including the development of computational tools that predict evolutionarily conserved RNA structures, as well as strategies that expand mode of action and facilitate interactions with cellular machinery. Existing RNA-targeted small molecules use a range of mechanisms including directing splicing - by acting as molecular glues with cellular proteins (such as branaplam and the FDA-approved risdiplam), inhibition of translation of undruggable proteins and deactivation of functional structures in noncoding RNAs. Here, we describe strategies to identify, validate and optimize small molecules that target the functional transcriptome, laying out a roadmap to advance these agents into the next decade.
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Affiliation(s)
| | - Xueyi Yang
- Department of Chemistry, Scripps Research, Jupiter, FL, USA
| | | | - Yuquan Tong
- Department of Chemistry, Scripps Research, Jupiter, FL, USA
| | - Robert T Batey
- Department of Biochemistry, University of Colorado, Boulder, CO, USA.
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15
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Bizuayehu TT, Labun K, Jakubec M, Jefimov K, Niazi A, Valen E. Long-read single-molecule RNA structure sequencing using nanopore. Nucleic Acids Res 2022; 50:e120. [PMID: 36166000 PMCID: PMC9723614 DOI: 10.1093/nar/gkac775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 08/16/2022] [Accepted: 08/29/2022] [Indexed: 12/24/2022] Open
Abstract
RNA molecules can form secondary and tertiary structures that can regulate their localization and function. Using enzymatic or chemical probing together with high-throughput sequencing, secondary structure can be mapped across the entire transcriptome. However, a limiting factor is that only population averages can be obtained since each read is an independent measurement. Although long-read sequencing has recently been used to determine RNA structure, these methods still used aggregate signals across the strands to detect structure. Averaging across the population also means that only limited information about structural heterogeneity across molecules or dependencies within each molecule can be obtained. Here, we present Single-Molecule Structure sequencing (SMS-seq) that combines structural probing with native RNA sequencing to provide non-amplified, structural profiles of individual molecules with novel analysis methods. Our new approach using mutual information enabled single molecule structural interrogation. Each RNA is probed at numerous bases enabling the discovery of dependencies and heterogeneity of structural features. We also show that SMS-seq can capture tertiary interactions, dynamics of riboswitch ligand binding, and mRNA structural features.
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Affiliation(s)
- Teshome Tilahun Bizuayehu
- Computational Biology Unit, Department of Informatics, University of Bergen, Norway
- Sars International Center for Marine Molecular Biology, University of Bergen, Norway
| | - Kornel Labun
- Computational Biology Unit, Department of Informatics, University of Bergen, Norway
| | | | - Kirill Jefimov
- Computational Biology Unit, Department of Informatics, University of Bergen, Norway
| | - Adnan Muhammad Niazi
- Computational Biology Unit, Department of Informatics, University of Bergen, Norway
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16
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Yan S, Ilgu M, Nilsen-Hamilton M, Lamm MH. Computational Modeling of RNA Aptamers: Structure Prediction of the Apo State. J Phys Chem B 2022; 126:7114-7125. [PMID: 36097649 PMCID: PMC9512008 DOI: 10.1021/acs.jpcb.2c04649] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 08/23/2022] [Indexed: 11/28/2022]
Abstract
RNA aptamers are single-stranded oligonucleotides that bind to specific molecular targets with high affinity and specificity. To design aptamers for new applications, it is critical to understand the ligand binding mechanism in terms of the structure and dynamics of the ligand-bound and apo states. The problem is that most of the NMR or X-ray crystal structures available for RNA aptamers are for ligand-bound states. Available apo state structures, mostly characterized by crystallization under nonphysiological conditions or probed by low resolution techniques, might fail to represent the diverse structural variations of the apo state in solution. Here, we develop an approach to obtain a representative ensemble of apo structures that are based on in silico RNA 3D structure prediction and in vitro experiments that characterize base stacking. Using the neomycin-B aptamer as a case study, an ensemble of structures for the aptamer in the apo (unbound) state are validated and then used to investigate the ligand-binding mechanism for the aptamer in complex with neomycin-B.
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Affiliation(s)
- Shuting Yan
- Iowa
State University, Ames, Iowa 50011, United States
| | - Muslum Ilgu
- Iowa
State University, Ames, Iowa 50011, United States
- Ames
National Laboratory, Ames, Iowa 50011, United States
- Aptalogic
Inc., Ames, Iowa 50014, United States
| | - Marit Nilsen-Hamilton
- Iowa
State University, Ames, Iowa 50011, United States
- Ames
National Laboratory, Ames, Iowa 50011, United States
- Aptalogic
Inc., Ames, Iowa 50014, United States
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17
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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: 7] [Impact Index Per Article: 3.5] [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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18
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Kognole AA, Hazel A, MacKerell AD. SILCS-RNA: Toward a Structure-Based Drug Design Approach for Targeting RNAs with Small Molecules. J Chem Theory Comput 2022; 18:5672-5691. [PMID: 35913731 PMCID: PMC9474704 DOI: 10.1021/acs.jctc.2c00381] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RNA molecules can act as potential drug targets in different diseases, as their dysregulated expression or misfolding can alter various cellular processes. Noncoding RNAs account for ∼70% of the human genome, and these molecules can have complex tertiary structures that present a great opportunity for targeting by small molecules. In the present study, the site identification by ligand competitive saturation (SILCS) computational approach is extended to target RNA, termed SILCS-RNA. Extensions to the method include an enhanced oscillating excess chemical potential protocol for the grand canonical Monte Carlo calculations and individual simulations of the neutral and charged solutes from which the SILCS functional group affinity maps (FragMaps) are calculated for subsequent binding site identification and docking calculations. The method is developed and evaluated against seven RNA targets and their reported small molecule ligands. SILCS-RNA provides a detailed characterization of the functional group affinity pattern in the small molecule binding sites, recapitulating the types of functional groups present in the ligands. The developed method is also shown to be useful for identification of new potential binding sites and identifying ligand moieties that contribute to binding, granular information that can facilitate ligand design. However, limitations in the method are evident including the ability to map the regions of binding sites occupied by ligand phosphate moieties and to fully account for the wide range of conformational heterogeneity in RNA associated with binding of different small molecules, emphasizing inherent challenges associated with applying computer-aided drug design methods to RNA. While limitations are present, the current study indicates how the SILCS-RNA approach may enhance drug discovery efforts targeting RNAs with small molecules.
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Affiliation(s)
- Abhishek A Kognole
- Computer Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, Baltimore, Maryland 21201, United States
| | - Anthony Hazel
- Computer Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, Baltimore, Maryland 21201, United States
| | - Alexander D MacKerell
- Computer Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, Baltimore, Maryland 21201, United States
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19
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Crielaard S, Maassen R, Vosman T, Rempkens I, Velema WA. Affinity-Based Profiling of the Flavin Mononucleotide Riboswitch. J Am Chem Soc 2022; 144:10462-10470. [PMID: 35666649 PMCID: PMC9204756 DOI: 10.1021/jacs.2c02685] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Riboswitches are
structural RNA elements that control gene expression.
These naturally occurring RNA sensors are of continued interest as
antibiotic targets, molecular sensors, and functional elements of
synthetic circuits. Here, we describe affinity-based profiling of
the flavin mononucleotide (FMN) riboswitch to characterize ligand
binding and structural folding. We designed and synthesized photoreactive
ligands and used them for photoaffinity labeling. We showed selective
labeling of the FMN riboswitch and used this covalent interaction
to quantitatively measure ligand binding, which we demonstrate with
the naturally occurring antibiotic roseoflavin. We measured conditional
riboswitch folding as a function of temperature and cation concentration.
Furthermore, combining photoaffinity labeling with reverse transcription
revealed ligand binding sites within the aptamer domain with single-nucleotide
resolution. The photoaffinity probe was applied to cellular extracts
of Bacillus subtilis to demonstrate conditional folding
of the endogenous low-abundant ribD FMN riboswitch
in biologically derived samples using quantitative PCR. Lastly, binding
of the riboswitch-targeting antibiotic roseoflavin to the FMN riboswitch
was measured in live bacteria using the photoaffinity probe.
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Affiliation(s)
- Stefan Crielaard
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Rick Maassen
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Tess Vosman
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Ivy Rempkens
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Willem A Velema
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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20
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Abstract
Recent events have pushed RNA research into the spotlight. Continued discoveries of RNA with unexpected diverse functions in healthy and diseased cells, such as the role of RNA as both the source and countermeasure to a severe acute respiratory syndrome coronavirus 2 infection, are igniting a new passion for understanding this functionally and structurally versatile molecule. Although RNA structure is key to function, many foundational characteristics of RNA structure are misunderstood, and the default state of RNA is often thought of and depicted as a single floppy strand. The purpose of this perspective is to help adjust mental models, equipping the community to better use the fundamental aspects of RNA structural information in new mechanistic models, enhance experimental design to test these models, and refine data interpretation. We discuss six core observations focused on the inherent nature of RNA structure and how to incorporate these characteristics to better understand RNA structure. We also offer some ideas for future efforts to make validated RNA structural information available and readily used by all researchers.
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Affiliation(s)
- Quentin Vicens
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, School of Medicine, Aurora, CO 80045
- RNA BioScience Initiative, University of Colorado Denver School of Medicine, Aurora, CO 80045
| | - Jeffrey S. Kieft
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, School of Medicine, Aurora, CO 80045
- RNA BioScience Initiative, University of Colorado Denver School of Medicine, Aurora, CO 80045
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21
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Zeller MJ, Nuthanakanti A, Li K, Aubé J, Serganov A, Weeks KM. Subsite Ligand Recognition and Cooperativity in the TPP Riboswitch: Implications for Fragment-Linking in RNA Ligand Discovery. ACS Chem Biol 2022; 17:438-448. [PMID: 35060698 PMCID: PMC8938680 DOI: 10.1021/acschembio.1c00880] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RNA molecules can show high levels of cooperativity in their global folding and interactions with divalent ions. However, cooperativity at individual ligand-RNA interaction sites remains poorly understood. Here, we investigated the binding of thiamine and methylene diphosphonic acid (MDP, a soluble structural analogue of pyrophosphate) to the thiamine pyrophosphate riboswitch. These ligands each bind weakly at proximal subsites, with 10 μM and 1 mM affinities, respectively. The affinity of MDP moderately improves when thiamine or thiamine-like fragments are pre-bound to the RNA. Covalent linking of thiamine and MDP substantially increases riboswitch binding to a notable high affinity of 20 nM. Crystal structures and single-molecule correlated chemical probing revealed favorable induced fit effects upon binding of individual ligands and, unexpectedly, a substantial thermodynamically unfavorable RNA structural rearrangement upon binding of the linked thiamine-MDP ligand. Thus, linking of two ligands of modest affinity, accompanied by an unfavorable structural rearrangement, still yields a potent linked RNA-binding compound. Since complex ligands often bind riboswitches and other RNAs at proximal subsites, principles derived from this work inform and support fragment-linking strategies for identifying small molecules that interact with RNA specifically and with high affinity.
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Affiliation(s)
- Meredith J. Zeller
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290
| | - Ashok Nuthanakanti
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016
| | - Kelin Li
- Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7363
| | - Jeffrey Aubé
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290,Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7363
| | - Alexander Serganov
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016
| | - Kevin M. Weeks
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290,correspondence,
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22
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Wakchaure PD, Ganguly B. Deciphering the mechanism of action of 5FDQD and the design of new neutral analogues for the FMN riboswitch: a well-tempered metadynamics simulation study. Phys Chem Chem Phys 2022; 24:817-828. [PMID: 34928280 DOI: 10.1039/d1cp01348c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The FMN riboswitch is a novel drug target for the design of new antibiotics, and efforts have been made to design new charged and uncharged ligands. Uncharged ligands have shown advantages of not requiring any transporter for intracellular transport or proteins for their phosphorylation. 5FDQD (5-(3-(4-fluorophenyl)butyl)-7,8-dimethylpyrido(3,4-b)quinoxaline-1,3(2H,5H)-dione) is a recently reported neutral ligand for the FMN riboswitch active against Clostridium difficile infection in mice. However, the crystal structure of the 5FDQD bound FMN riboswitch is not available, and the mechanism of ligand binding and triggering the function of the riboswitch is not well understood. We have examined 5FDQD for its binding affinity with the FMN riboswitch using the well-tempered metadynamics (WT-MtD) simulation technique. The crystal structure of the FMN riboswitch shows that the FMN interacts with the J4/5 region through the phosphate group with G62; however, the uncharged ligands take advantage of π-π stacking interactions with the same residue of the riboswitch observed from the WT-MtD simulation results. The simulation results show that the presence of fluorine on the phenyl ring in 5FDQD is important to enhance the binding affinity of the neutral ligands with the FMN riboswitch. The WT-MtD results showed that the 1,2-difluoro substitution on the phenyl ring in 5FDQD (FMN-difluoro2) and the 1,3 positions in the phenyl ring (FMN-difluoro1) showed weaker binding energy with the FMN riboswitch compared to 5FDQD. The substitution of another fluorine atom at the 5-position of the phenyl ring (FMN-trifluoro) showed a comparable binding affinity (∼-31.4 kcal mol-1) to 5FDQD. Electron-donating substitution on the phenyl ring such as the amino group also lowered the binding affinity (-28.8 kcal mol-1) with the riboswitch compared to 5FDQD. The computed results suggest that the position and nature of substitution in the phenyl ring of the uncharged ligands affect the overall binding and such a delicate balance is important to achieve superior binding affinity with the FMN riboswitch.
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Affiliation(s)
- Padmaja D Wakchaure
- Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar-364002, Gujarat, India.,Academy of Scientific and Innovative Research, Ghaziabad, Uttar Pradesh-201 002, India.
| | - Bishwajit Ganguly
- Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar-364002, Gujarat, India.,Academy of Scientific and Innovative Research, Ghaziabad, Uttar Pradesh-201 002, India.
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23
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Jiang Y, Chen SJ. RLDOCK method for predicting RNA-small molecule binding modes. Methods 2022; 197:97-105. [PMID: 33549725 PMCID: PMC8333169 DOI: 10.1016/j.ymeth.2021.01.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 01/24/2021] [Accepted: 01/27/2021] [Indexed: 01/03/2023] Open
Abstract
RNA molecules play critical roles in cellular functions at the level of gene expression and regulation. The intricate 3D structures and the functional roles of RNAs make RNA molecules ideal targets for therapeutic drugs. The rational design of RNA-targeted drug requires accurate modeling of RNA-ligand interactions. Recently a new computational tool, RLDOCK, was developed to predict ligand binding sites and binding poses. Using an iterative multiscale sampling and search algorithm and a energy-based evaluation of ligand poses, the method enables efficient and accurate predictions for RNA-ligand interactions. Here we present a detailed illustration of the computational procedure for the practical implementation of the RLDOCK method. Using Flavin mononucleotide (FMN) docking to F. nucleatum FMN riboswitch as an example, we illustrate the computational protocol for RLDOCK-based prediction of RNA- ligand interactions. The RLDOCK software is freely accessible at http://https://github.com/Vfold-RNA/RLDOCK.
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Affiliation(s)
- Yangwei Jiang
- Department of Physics, MU Institute for Data Science and Informatics, Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - Shi-Jie Chen
- Department of Physics, MU Institute for Data Science and Informatics, Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA.
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24
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Wilson TJ, Lilley DMJ. The potential versatility of RNA catalysis. WILEY INTERDISCIPLINARY REVIEWS. RNA 2021; 12:e1651. [PMID: 33949113 DOI: 10.1002/wrna.1651] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 02/26/2021] [Accepted: 03/01/2021] [Indexed: 01/21/2023]
Abstract
It is commonly thought that in the early development of life on this planet RNA would have acted both as a store of genetic information and as a catalyst. While a number of RNA enzymes are known in contemporary cells, they are largely confined to phosphoryl transfer reactions, whereas an RNA based metabolism would have required a much greater chemical diversity of catalysis. Here we discuss how RNA might catalyze a wider variety of chemistries, and particularly how information gleaned from riboswitches could suggest how ribozymes might recruit coenzymes to expand their chemical range. We ask how we might seek such activities in modern biology. This article is categorized under: RNA-Based Catalysis > Miscellaneous RNA-Catalyzed Reactions Regulatory RNAs/RNAi/Riboswitches > Riboswitches RNA Structure and Dynamics > RNA Structure, Dynamics and Chemistry.
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Affiliation(s)
- Timothy J Wilson
- Cancer Research UK Nucleic Acid Structure Research Group, MSI/WTB Complex, The University of Dundee, Dundee, UK
| | - David M J Lilley
- Cancer Research UK Nucleic Acid Structure Research Group, MSI/WTB Complex, The University of Dundee, Dundee, UK
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25
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Deb I, Wong H, Tacubao C, Frank AT. Quantum Mechanics Helps Uncover Atypical Recognition Features in the Flavin Mononucleotide Riboswitch. J Phys Chem B 2021; 125:8342-8350. [PMID: 34310879 DOI: 10.1021/acs.jpcb.1c02702] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Estimating the binding energies of small molecules to RNA could help uncover their molecular recognition characteristics and be used to rationally design RNA-targeting chemical probes. Here, we leveraged the ability of the fragment molecular orbital (FMO) method to provide detailed pairwise energetic information to examine the interactions between the aptamer domain of the flavin mononucleotide (FMN)-responsive riboswitch and small-molecule ligands. After developing an efficient protocol for executing high-level FMO calculations on RNA-ligand complexes, we applied our protocol to nine FMN-aptamer-ligand complexes. We then used the results to identify "hot-spots" within the aptamer and decomposed pairwise interactions between the hot-spot residues and the ligands. Interestingly, we found that several of these hot-spot residues interact with the ligands via atypical CH···O hydrogen bonds and anion-π contacts, as well as (face-to-edge) T-shaped π-π interactions. We envision that our results should pave the way for the wider and more prominent use of FMO calculations to study structure-energy relationships in diverse RNA-ligand systems, which in turn may provide a basis for dissecting the molecular recognition characteristics of RNAs.
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Affiliation(s)
- Indrajit Deb
- Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Hazel Wong
- Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Colleen Tacubao
- Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Aaron T Frank
- Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109, United States.,Chemistry Department, University of Michigan, Ann Arbor, Michigan 48109, United States
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26
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Rekand IH, Brenk R. DrugPred_RNA-A Tool for Structure-Based Druggability Predictions for RNA Binding Sites. J Chem Inf Model 2021; 61:4068-4081. [PMID: 34286972 PMCID: PMC8389535 DOI: 10.1021/acs.jcim.1c00155] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
![]()
RNA is an emerging
target for drug discovery. However, like for
proteins, not all RNA binding sites are equally suited to be addressed
with conventional drug-like ligands. To this end, we have developed
the structure-based druggability predictor DrugPred_RNA to identify
druggable RNA binding sites. Due to the paucity of annotated RNA binding
sites, the predictor was trained on protein pockets, albeit using
only descriptors that can be calculated for both RNA and protein binding
sites. DrugPred_RNA performed well in discriminating druggable from
less druggable binding sites for the protein set and delivered predictions
for selected RNA binding sites that agreed with manual assignment.
In addition, most drug-like ligands contained in an RNA test set were
found in pockets predicted to be druggable, further adding confidence
to the performance of DrugPred_RNA. The method is robust against conformational
and sequence changes in the binding sites and can contribute to direct
drug discovery efforts for RNA targets.
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Affiliation(s)
- Illimar Hugo Rekand
- Department of Biomedicine, University of Bergen, Jonas Lies Vei, 5020 Bergen, Norway
| | - Ruth Brenk
- Department of Biomedicine, University of Bergen, Jonas Lies Vei, 5020 Bergen, Norway
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27
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Abdelsattar AS, Mansour Y, Aboul-Ela F. The Perturbed Free-Energy Landscape: Linking Ligand Binding to Biomolecular Folding. Chembiochem 2021; 22:1499-1516. [PMID: 33351206 DOI: 10.1002/cbic.202000695] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 12/19/2020] [Indexed: 12/24/2022]
Abstract
The effects of ligand binding on biomolecular conformation are crucial in drug design, enzyme mechanisms, the regulation of gene expression, and other biological processes. Descriptive models such as "lock and key", "induced fit", and "conformation selection" are common ways to interpret such interactions. Another historical model, linked equilibria, proposes that the free-energy landscape (FEL) is perturbed by the addition of ligand binding energy for the bound population of biomolecules. This principle leads to a unified, quantitative theory of ligand-induced conformation change, building upon the FEL concept. We call the map of binding free energy over biomolecular conformational space the "binding affinity landscape" (BAL). The perturbed FEL predicts/explains ligand-induced conformational changes conforming to all common descriptive models. We review recent experimental and computational studies that exemplify the perturbed FEL, with emphasis on RNA. This way of understanding ligand-induced conformation dynamics motivates new experimental and theoretical approaches to ligand design, structural biology and systems biology.
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Affiliation(s)
- Abdallah S Abdelsattar
- Center for X-Ray Determination of the Structure of Matter, Zewail City of Science and Technology, Ahmed Zewail Road, October Gardens, 12578, Giza, Egypt
| | - Youssef Mansour
- Center for X-Ray Determination of the Structure of Matter, Zewail City of Science and Technology, Ahmed Zewail Road, October Gardens, 12578, Giza, Egypt
| | - Fareed Aboul-Ela
- Center for X-Ray Determination of the Structure of Matter, Zewail City of Science and Technology, Ahmed Zewail Road, October Gardens, 12578, Giza, Egypt
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28
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Stefaniak F, Bujnicki JM. AnnapuRNA: A scoring function for predicting RNA-small molecule binding poses. PLoS Comput Biol 2021; 17:e1008309. [PMID: 33524009 PMCID: PMC7877745 DOI: 10.1371/journal.pcbi.1008309] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 02/11/2021] [Accepted: 12/16/2020] [Indexed: 11/22/2022] Open
Abstract
RNA is considered as an attractive target for new small molecule drugs. Designing active compounds can be facilitated by computational modeling. Most of the available tools developed for these prediction purposes, such as molecular docking or scoring functions, are parametrized for protein targets. The performance of these methods, when applied to RNA-ligand systems, is insufficient. To overcome these problems, we developed AnnapuRNA, a new knowledge-based scoring function designed to evaluate RNA-ligand complex structures, generated by any computational docking method. We also evaluated three main factors that may influence the structure prediction, i.e., the starting conformer of a ligand, the docking program, and the scoring function used. We applied the AnnapuRNA method for a post-hoc study of the recently published structures of the FMN riboswitch. Software is available at https://github.com/filipspl/AnnapuRNA. Drug development is a lengthy and complicated process, which requires costly experiments on a very large number of chemical compounds. The identification of chemical molecules with desired properties can be facilitated by computational methods. Several methods were developed for computer-aided design of drugs that target protein molecules. However, recently the ribonucleic acid (RNA) emerged as an attractive target for the development of new drugs. Unfortunately, the portfolio of the computer methods that can be applied to study RNA and its interactions with small chemical molecules is very limited. This situation motivated us to develop a new computational method, with which to predict RNA-small molecule interactions. To this end, we collected the information on the statistics of interactions in experimentally determined structures of complexes formed by RNA with small molecules. We then used the statistical data to train machine learning methods aiming to distinguish between RNA-ligand interactions observed experimentally and other interactions that can be observed in theoretical analyses, but are not observed in nature. The resulting method called AnnapuRNA is superior to other similar tools and can be used to predict preferred ligands of RNA molecules and how RNA and small molecules interact with each other.
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Affiliation(s)
- Filip Stefaniak
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Warsaw, Poland
- * E-mail: (FS); (JMB)
| | - Janusz M. Bujnicki
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Warsaw, Poland
- Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland
- * E-mail: (FS); (JMB)
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29
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Panchal V, Brenk R. Riboswitches as Drug Targets for Antibiotics. Antibiotics (Basel) 2021; 10:45. [PMID: 33466288 PMCID: PMC7824784 DOI: 10.3390/antibiotics10010045] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/21/2020] [Accepted: 12/29/2020] [Indexed: 12/13/2022] Open
Abstract
Riboswitches reside in the untranslated region of RNA and regulate genes involved in the biosynthesis of essential metabolites through binding of small molecules. Since their discovery at the beginning of this century, riboswitches have been regarded as potential antibacterial targets. Using fragment screening, high-throughput screening and rational ligand design guided by X-ray crystallography, lead compounds against various riboswitches have been identified. Here, we review the current status and suitability of the thiamine pyrophosphate (TPP), flavin mononucleotide (FMN), glmS, guanine, and other riboswitches as antibacterial targets and discuss them in a biological context. Further, we highlight challenges in riboswitch drug discovery and emphasis the need to develop riboswitch specific high-throughput screening methods.
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Affiliation(s)
- Vipul Panchal
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5020 Bergen, Norway
| | - Ruth Brenk
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5020 Bergen, Norway
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30
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Schroeder GM, Dutta D, Cavender CE, Jenkins J, Pritchett EM, Baker CD, Ashton JM, Mathews DH, Wedekind JE. Analysis of a preQ1-I riboswitch in effector-free and bound states reveals a metabolite-programmed nucleobase-stacking spine that controls gene regulation. Nucleic Acids Res 2020; 48:8146-8164. [PMID: 32597951 PMCID: PMC7641330 DOI: 10.1093/nar/gkaa546] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/13/2020] [Accepted: 06/16/2020] [Indexed: 01/20/2023] Open
Abstract
Riboswitches are structured RNA motifs that recognize metabolites to alter the conformations of downstream sequences, leading to gene regulation. To investigate this molecular framework, we determined crystal structures of a preQ1-I riboswitch in effector-free and bound states at 2.00 Å and 2.65 Å-resolution. Both pseudoknots exhibited the elusive L2 loop, which displayed distinct conformations. Conversely, the Shine-Dalgarno sequence (SDS) in the S2 helix of each structure remained unbroken. The expectation that the effector-free state should expose the SDS prompted us to conduct solution experiments to delineate environmental changes to specific nucleobases in response to preQ1. We then used nudged elastic band computational methods to derive conformational-change pathways linking the crystallographically-determined effector-free and bound-state structures. Pathways featured: (i) unstacking and unpairing of L2 and S2 nucleobases without preQ1-exposing the SDS for translation and (ii) stacking and pairing L2 and S2 nucleobases with preQ1-sequestering the SDS. Our results reveal how preQ1 binding reorganizes L2 into a nucleobase-stacking spine that sequesters the SDS, linking effector recognition to biological function. The generality of stacking spines as conduits for effector-dependent, interdomain communication is discussed in light of their existence in adenine riboswitches, as well as the turnip yellow mosaic virus ribosome sensor.
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Affiliation(s)
- Griffin M Schroeder
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Debapratim Dutta
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Chapin E Cavender
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Jermaine L Jenkins
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Elizabeth M Pritchett
- Genomics Research Center, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Cameron D Baker
- Genomics Research Center, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - John M Ashton
- Genomics Research Center, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - David H Mathews
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Joseph E Wedekind
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
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31
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Wilt HM, Yu P, Tan K, Wang YX, Stagno JR. FMN riboswitch aptamer symmetry facilitates conformational switching through mutually exclusive coaxial stacking configurations. JOURNAL OF STRUCTURAL BIOLOGY-X 2020; 4:100035. [PMID: 33103111 PMCID: PMC7573352 DOI: 10.1016/j.yjsbx.2020.100035] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 07/29/2020] [Accepted: 08/02/2020] [Indexed: 11/16/2022]
Abstract
Knowledge of both apo and holo states of riboswitches aid in elucidating the various mechanisms of ligand-induced conformational “switching” that underpin their gene-regulating capabilities. Previous structural studies on the flavin mononucleotide (FMN)-binding aptamer of the FMN riboswitch, however, have revealed minimal conformational changes associated with ligand binding that do not adequately explain the basis for the switching behavior. We have determined a 2.7-Å resolution crystal structure of the ligand-free FMN riboswitch aptamer that is distinct from previously reported structures, particularly in the conformation and orientation of the P1 and P4 helices. The nearly symmetrical tertiary structure provides a mechanism by which one of two pairs of adjacent helices (P3/P4 or P1/P6) undergo collinear stacking in a mutually exclusive manner, in the absence or presence of ligand, respectively. Comparison of these structures suggests the stem-loop that includes P4 and L4 is important for maintaining a global conformational state that, in the absence of ligand, disfavors formation of the P1 regulatory helix. Together, these results provide further insight to the structural basis for conformational switching of the FMN riboswitch.
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Affiliation(s)
- Haley M Wilt
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.,Washington College, Chestertown, Maryland 21620, USA
| | - Ping Yu
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Kemin Tan
- Structural Biology Center, X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, IL 60439, USA
| | - Yun-Xing Wang
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Jason R Stagno
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
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32
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Wakchaure PD, Jana K, Ganguly B. Structural insights into the interactions of flavin mononucleotide (FMN) and riboflavin with FMN riboswitch: a molecular dynamics simulation study. J Biomol Struct Dyn 2019; 38:3856-3866. [PMID: 31498025 DOI: 10.1080/07391102.2019.1665587] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Antibiotics resistance is becoming a serious problem associated with fatalities and suffering patients. New antibiotics that can target the broader spectrum of cellular processes are warranted. One of the recent approaches in this regard is to target the special type of RNA riboswitches in bacteria. In this report, we have explored the mechanistic pathways of ligand-dependent conformational changes of flavin mononucleotide (FMN) riboswitch using molecular dynamics (MD) simulation studies. Cognate ligands FMN and riboflavin (RBF) have shown very different behavior with FMN riboswitch in terms of their role in the gene regulation process. These two ligands have similar scaffold, except the terminal phosphate group in FMN ligand. The MD simulations reveal that the binding of FMN ligand with the riboswitch does not lead to global folding of structure, rather lead to local changes in riboswitch structure. The binding free energy calculated with molecular mechanics Poisson-Boltzmann surface area method suggests the stronger binding of FMN than RBF to the riboswitch and electrostatic energy contributes chiefly to stabilize the complex. Further, the hydrogen bonding analysis identified the key binding site residues G11, G32, G62 of the riboswitch with FMN and RBF. The critical role of the phosphate group in the FMN ligand for binding with the active site of a riboswitch is also borne out in this study. These results unravel the importance of functional groups in natural ligands on designing newer ligands for FMN riboswitch as new antibiotics in the future.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Padmaja D Wakchaure
- Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India.,Academy of Scientific and Innovative Research, CSIR-CSMCRI, Bhavnagar, Gujarat, India
| | - Kalyanashis Jana
- Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India.,Academy of Scientific and Innovative Research, CSIR-CSMCRI, Bhavnagar, Gujarat, India
| | - Bishwajit Ganguly
- Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India.,Academy of Scientific and Innovative Research, CSIR-CSMCRI, Bhavnagar, Gujarat, India
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33
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Habibian M, Velema WA, Kietrys AM, Onishi Y, Kool ET. Polyacetate and Polycarbonate RNA: Acylating Reagents and Properties. Org Lett 2019; 21:5413-5416. [PMID: 31268332 PMCID: PMC6775763 DOI: 10.1021/acs.orglett.9b01526] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Acylation of RNA at 2'-OH groups is widely applied in mapping RNA structure and recently for controlling RNA function. Reactions are described that install the smallest 2-carbon acyl groups on RNA-namely, 2'-O-acetyl and 2'-O-carbonate groups. Hybridization and thermal melting experiments are performed to assess the effects of the acyl groups on duplex formation. Both reagents can be employed at lower concentrations to map RNA secondary structure by reverse transcriptase primer extension (SHAPE) methods.
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Affiliation(s)
| | | | - Anna M. Kietrys
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Yoshiyuki Onishi
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Eric T. Kool
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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34
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Regulation of Bacterial Gene Expression by Transcription Attenuation. Microbiol Mol Biol Rev 2019; 83:83/3/e00019-19. [PMID: 31270135 DOI: 10.1128/mmbr.00019-19] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
A wide variety of mechanisms that control gene expression in bacteria are based on conditional transcription termination. Generally, in these mechanisms, a transcription terminator is located between a promoter and a downstream gene(s), and the efficiency of the terminator is controlled by a regulatory effector that can be a metabolite, protein, or RNA. The most common type of regulation involving conditional termination is transcription attenuation, in which the primary regulatory target is an essential element of a single terminator. The terminator can be either intrinsic or Rho dependent, with each presenting unique regulatory targets. Transcription attenuation mechanisms can be divided into five classes based primarily on the manner in which transcription termination is rendered conditional. This review summarizes each class of control mechanisms from a historical perspective, describes important examples in a physiological context and the current state of knowledge, highlights major advances, and discusses expectations of future discoveries.
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35
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Abstract
The three-dimensional structures of RNA molecules provide rich and often critical information for understanding their functions, including how they recognize small molecule and protein partners. Computational modeling of RNA 3D structure is becoming increasingly accurate, particularly with the availability of growing numbers of template structures already solved experimentally and the development of sequence alignment and 3D modeling tools to take advantage of this database. For several recent "RNA puzzle" blind modeling challenges, we have successfully identified useful template structures and achieved accurate structure predictions through homology modeling tools developed in the Rosetta software suite. We describe our semi-automated methodology here and walk through two illustrative examples: an adenine riboswitch aptamer, modeled from a template guanine riboswitch structure, and a SAM I/IV riboswitch aptamer, modeled from a template SAM I riboswitch structure.
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Affiliation(s)
- Andrew M Watkins
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States
| | - Ramya Rangan
- Biophysics Program, Stanford University, Stanford, CA, United States
| | - Rhiju Das
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, United States; Biophysics Program, Stanford University, Stanford, CA, United States.
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36
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Hewitt WM, Calabrese DR, Schneekloth JS. Evidence for ligandable sites in structured RNA throughout the Protein Data Bank. Bioorg Med Chem 2019; 27:2253-2260. [PMID: 30982658 PMCID: PMC8283815 DOI: 10.1016/j.bmc.2019.04.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 04/01/2019] [Accepted: 04/06/2019] [Indexed: 10/27/2022]
Abstract
RNA has attracted considerable attention as a target for small molecules. However, methods to identify, study, and characterize suitable RNA targets have lagged behind strategies for protein targets. One approach that has received considerable attention for protein targets has been to utilize computational analysis to investigate ligandable "pockets" on proteins that are amenable to small molecule binding. These studies have shown that selected physical properties of pockets are important parameters that govern the ability of a structure to bind to small molecules. This work describes a similar analysis to study pockets on all RNAs in the Protein Data Bank (PDB). Using parameters such as buriedness, hydrophobicity, volume, and other properties, the set of all RNAs is analyzed and compared to all proteins. Considerable overlap is observed between the properties of pockets on RNAs and proteins. Thus, many RNAs are capable of populating conformations with pockets that are likely suitable for small molecule binding. Further, principal moment of inertia (PMI) calculations reveal that liganded RNAs exist in diverse structural space, much of which overlaps with protein structural space. Taken together, these results suggest that complex folded RNAs adopt unique structures with pockets that may represent viable opportunities for small molecule targeting.
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Affiliation(s)
- William M Hewitt
- Chemical Biology Laboratory, National Cancer Institute, Frederick, MD 21702, United States
| | - David R Calabrese
- Chemical Biology Laboratory, National Cancer Institute, Frederick, MD 21702, United States
| | - John S Schneekloth
- Chemical Biology Laboratory, National Cancer Institute, Frederick, MD 21702, United States.
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37
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Abstract
Biological molecules are often highly dynamic, and this flexibility can be critical for function. The large range of sampled timescales and the fact that many of the conformers that are continually explored are only transiently formed and sparsely populated challenge current biophysical approaches. Solution nuclear magnetic resonance (NMR) spectroscopy has emerged as a powerful method for characterizing biomolecular dynamics in detail, even in cases where excursions involve short-lived states. Here, we briefly review a number of NMR experiments for studies of biomolecular dynamics on the microsecond-to-second timescale and focus on applications to protein and nucleic acid systems that clearly illustrate the functional relevance of motion in both health and disease.
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Affiliation(s)
- Ashok Sekhar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
| | - Lewis E. Kay
- Departments of Molecular Genetics, Biochemistry, and Chemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
- Program in Molecular Medicine, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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38
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Munzar JD, Ng A, Juncker D. Duplexed aptamers: history, design, theory, and application to biosensing. Chem Soc Rev 2019; 48:1390-1419. [PMID: 30707214 DOI: 10.1039/c8cs00880a] [Citation(s) in RCA: 121] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Nucleic acid aptamers are single stranded DNA or RNA sequences that specifically bind a cognate ligand. In addition to their widespread use as stand-alone affinity binding reagents in analytical chemistry, aptamers have been engineered into a variety of ligand-specific biosensors, termed aptasensors. One of the most common aptasensor formats is the duplexed aptamer (DA). As defined herein, DAs are aptasensors containing two nucleic acid elements coupled via Watson-Crick base pairing: (i) an aptamer sequence, which serves as a ligand-specific receptor, and (ii) an aptamer-complementary element (ACE), such as a short DNA oligonucleotide, which is designed to hybridize to the aptamer. The ACE competes with ligand binding, such that DAs generate a signal upon ligand-dependent ACE-aptamer dehybridization. DAs possess intrinsic advantages over other aptasensor designs. For example, DA biosensing designs generalize across DNA and RNA aptamers, DAs are compatible with many readout methods, and DAs are inherently tunable on the basis of nucleic acid hybridization. However, despite their utility and popularity, DAs have not been well defined in the literature, leading to confusion over the differences between DAs and other aptasensor formats. In this review, we introduce a framework for DAs based on ACEs, and use this framework to distinguish DAs from other aptasensor formats and to categorize cis- and trans-DA designs. We then explore the ligand binding dynamics and chemical properties that underpin DA systems, which fall under conformational selection and induced fit models, and which mirror classical SN1 and SN2 models of nucleophilic substitution reactions. We further review a variety of in vitro and in vivo applications of DAs in the chemical and biological sciences, including riboswitches and riboregulators. Finally, we present future directions of DAs as ligand-responsive nucleic acids. Owing to their tractability, versatility and ease of engineering, DA biosensors bear a great potential for the development of new applications and technologies in fields ranging from analytical chemistry and mechanistic modeling to medicine and synthetic biology.
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Affiliation(s)
- Jeffrey D Munzar
- McGill University and Genome Quebec Innovation Centre, Montreal, Quebec, Canada.
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39
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Abstract
RNA is a versatile biomolecule capable of transferring information, taking on distinct three-dimensional shapes, and reacting to ambient conditions. RNA molecules utilize a wide range of mechanisms to control gene expression. An example of such regulation is riboswitches. Consisting exclusively of RNA, they are able to control important metabolic processes, thus providing an elegant and efficient RNA-only regulation system. Existing across all domains of life, riboswitches appear to represent one of the most highly conserved mechanisms for the regulation of a broad range of biochemical pathways. Through binding of a wide range of small-molecule ligands to their so-called aptamer domain, riboswitches undergo a conformational change in their downstream "expression platform." In consequence, the pattern of gene expression changes, which in turn results in increased or decreased protein production. Riboswitches unite the sensing and transduction of a signal that can directly be coupled to the metabolism of the cell; thus they constitute a very potent regulatory mechanism for many organisms. Highly specific RNA-binding domains not only occur in vivo but can also be evolved by means of the SELEX (systematic evolution of ligands by exponential enrichment) method, which allows in vitro selection of aptamers against almost any ligand. Coupling of these aptamers with an expression platform has led to the development of synthetic riboswitches, a highly active research field of great relevance and immense potential. The aim of this review is to summarize developments in the riboswitch field over the last decade and address key questions of recent research.
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40
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Sinumvayo JP, Zhao C, Tuyishime P. Recent advances and future trends of riboswitches: attractive regulatory tools. World J Microbiol Biotechnol 2018; 34:171. [PMID: 30413889 DOI: 10.1007/s11274-018-2554-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 11/02/2018] [Indexed: 01/06/2023]
Abstract
Bacterial genomes contain a huge amount of different genes. These genes are spatiotemporally expressed to accomplish some required functions within the organism. Inside the cell, any step of gene expression may be modulated at four possible places such as transcription initiation, translation regulation, mRNA stability and protein stability. To achieve this, there is a necessity of strong regulators either natural or synthetic which can fine-tune gene expression regarding the required function. In recent years, riboswitches as metabolite responsive control elements residing in the untranslated regions of certain messenger RNAs, have been known to control gene expression at transcription or translation level. Importantly, these control elements do not prescribe the involvement of protein factors for metabolite binding. However, they own their particular properties to sense intramolecular metabolites (ligands). Herein, we highlighted current important bacterial riboswitches, their applications to support genetic control, ligand-binding domain mechanisms and current progress in synthetic riboswitches.
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Affiliation(s)
- Jean Paul Sinumvayo
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China. .,University of Chinese Academy of Sciences, Beijing, China.
| | - Chunhua Zhao
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Philibert Tuyishime
- University of Chinese Academy of Sciences, Beijing, China.,Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
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41
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Vicens Q, Mondragón E, Reyes FE, Coish P, Aristoff P, Berman J, Kaur H, Kells KW, Wickens P, Wilson J, Gadwood RC, Schostarez HJ, Suto RK, Blount KF, Batey RT. Structure-Activity Relationship of Flavin Analogues That Target the Flavin Mononucleotide Riboswitch. ACS Chem Biol 2018; 13:2908-2919. [PMID: 30107111 DOI: 10.1021/acschembio.8b00533] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The flavin mononucleotide (FMN) riboswitch is an emerging target for the development of novel RNA-targeting antibiotics. We previously discovered an FMN derivative, 5FDQD, that protects mice against diarrhea-causing Clostridium difficile bacteria. Here, we present the structure-based drug design strategy that led to the discovery of this fluoro-phenyl derivative with antibacterial properties. This approach involved the following stages: (1) structural analysis of all available free and bound FMN riboswitch structures; (2) design, synthesis, and purification of derivatives; (3) in vitro testing for productive binding using two chemical probing methods; (4) in vitro transcription termination assays; and (5) resolution of the crystal structures of the FMN riboswitch in complex with the most mature candidates. In the process, we delineated principles for productive binding to this riboswitch, thereby demonstrating the effectiveness of a coordinated structure-guided approach to designing drugs against RNA.
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Affiliation(s)
- Quentin Vicens
- Department of Chemistry and Biochemistry, University of Colorado, 596 UCB, Boulder, Colorado 80309, United States
| | - Estefanía Mondragón
- Department of Chemistry and Biochemistry, University of Colorado, 596 UCB, Boulder, Colorado 80309, United States
| | - Francis E. Reyes
- Department of Chemistry and Biochemistry, University of Colorado, 596 UCB, Boulder, Colorado 80309, United States
| | - Philip Coish
- BioRelix Inc., 124 Washington Street, Foxborough, Massachusetts 02035, United States
| | - Paul Aristoff
- Aristoff Consulting LLC, 3726 Green Spring Drive, Fort Collins, Colorado 80528, United States
| | - Judd Berman
- Dalton Pharma Services, 349 Wildcat Road, Toronto, ON M3J 2S3, Canada
| | - Harpreet Kaur
- Dalton Pharma Services, 349 Wildcat Road, Toronto, ON M3J 2S3, Canada
| | - Kevin W. Kells
- Dalton Pharma Services, 349 Wildcat Road, Toronto, ON M3J 2S3, Canada
| | - Phil Wickens
- Dalton Pharma Services, 349 Wildcat Road, Toronto, ON M3J 2S3, Canada
| | - Jeffery Wilson
- Dalton Pharma Services, 349 Wildcat Road, Toronto, ON M3J 2S3, Canada
| | - Robert C. Gadwood
- Kalexsyn, Inc., 4502 Campus Drive, Kalamazoo, Michigan 49008, United States
| | | | - Robert K. Suto
- Xtal BioStructures, Inc., 12 Michigan Drive, Natick, Massachusetts 01760, United States
| | - Kenneth F. Blount
- BioRelix Inc., 124 Washington Street, Foxborough, Massachusetts 02035, United States
| | - Robert T. Batey
- Department of Chemistry and Biochemistry, University of Colorado, 596 UCB, Boulder, Colorado 80309, United States
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42
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Peselis A, Serganov A. ykkC riboswitches employ an add-on helix to adjust specificity for polyanionic ligands. Nat Chem Biol 2018; 14:887-894. [PMID: 30120360 PMCID: PMC6263941 DOI: 10.1038/s41589-018-0114-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 07/02/2018] [Indexed: 12/20/2022]
Abstract
The ykkC family of bacterial riboswitches combines several widespread classes that have similar secondary structures and consensus motifs but control different genes in response to different cellular metabolites. Here we report the crystal structures of two distinct ykkC riboswitches specifically bound to their cognate ligands ppGpp, a second messenger involved in stress response, or PRPP, a precursor in purine biosynthesis. Both RNAs adopt similar structures and contain a conserved core previously observed in the guanidine-specific ykkC riboswitch. However, ppGpp and PRPP riboswitches uniquely employ an additional helical element that joins the ends of the ligand-sensing domains and creates a tunnel for direct and Mg2+-mediated binding of ligands. Mutational and footprinting experiments highlight the importance of conserved nucleotides forming the tunnel and long-distance contacts for ligand binding and genetic response. Our work provides new insights into the specificity of riboswitches and gives a unique opportunity for future studies of RNA evolution.
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Affiliation(s)
- Alla Peselis
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Alexander Serganov
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA.
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43
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Rode AB, Endoh T, Sugimoto N. Crowding Shifts the FMN Recognition Mechanism of Riboswitch Aptamer from Conformational Selection to Induced Fit. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201803052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ambadas B. Rode
- Frontier Institute for Biomolecular Engineering Research (FIBER); Japan
| | - Tamaki Endoh
- Frontier Institute for Biomolecular Engineering Research (FIBER); Japan
| | - Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER); Japan
- Graduate School of Frontiers of Innovative Research in Science and Technology (FIRST); Konan University; 7-1-20 Minatojima-minamimachi Chuo-ku Kobe 650-0047 Japan
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44
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Rode AB, Endoh T, Sugimoto N. Crowding Shifts the FMN Recognition Mechanism of Riboswitch Aptamer from Conformational Selection to Induced Fit. Angew Chem Int Ed Engl 2018; 57:6868-6872. [PMID: 29663603 DOI: 10.1002/anie.201803052] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 04/06/2018] [Indexed: 11/07/2022]
Abstract
In bacteria, the binding between the riboswitch aptamer domain and ligand is regulated by environmental cues, such as low Mg2+ in macrophages during pathogenesis to ensure spatiotemporal expression of virulence genes. Binding was investigated between the flavin mononucleotide (FMN) riboswitch aptamer and its anionic ligand in the presence of molecular crowding agent without Mg2+ ion, which mimics pathogenic conditions. Structural, kinetic, and thermodynamic analyses under the crowding revealed more dynamic conformational rearrangements of the FMN riboswitch aptamer compared to dilute Mg2+ -containing solution. It is hypothesized that under crowding conditions FMN binds through an induced fit mechanism in contrast to the conformational selection mechanism previously demonstrated in dilute Mg2+ solution. Since these two mechanisms involve different conformational intermediates and rate constants, these findings have practical significance in areas such as drug design and RNA engineering.
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Affiliation(s)
- Ambadas B Rode
- Frontier Institute for Biomolecular Engineering Research (FIBER), Japan
| | - Tamaki Endoh
- Frontier Institute for Biomolecular Engineering Research (FIBER), Japan
| | - Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER), Japan.,Graduate School of Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, 7-1-20 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
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45
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Rizvi NF, Howe JA, Nahvi A, Klein DJ, Fischmann TO, Kim HY, McCoy MA, Walker SS, Hruza A, Richards MP, Chamberlin C, Saradjian P, Butko MT, Mercado G, Burchard J, Strickland C, Dandliker PJ, Smith GF, Nickbarg EB. Discovery of Selective RNA-Binding Small Molecules by Affinity-Selection Mass Spectrometry. ACS Chem Biol 2018; 13:820-831. [PMID: 29412640 DOI: 10.1021/acschembio.7b01013] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Recent advances in understanding the relevance of noncoding RNA (ncRNA) to disease have increased interest in drugging ncRNA with small molecules. The recent discovery of ribocil, a structurally distinct synthetic mimic of the natural ligand of the flavin mononucleotide (FMN) riboswitch, has revealed the potential chemical diversity of small molecules that target ncRNA. Affinity-selection mass spectrometry (AS-MS) is theoretically applicable to high-throughput screening (HTS) of small molecules binding to ncRNA. Here, we report the first application of the Automated Ligand Detection System (ALIS), an indirect AS-MS technique, for the selective detection of small molecule-ncRNA interactions, high-throughput screening against large unbiased small-molecule libraries, and identification and characterization of novel compounds (structurally distinct from both FMN and ribocil) that target the FMN riboswitch. Crystal structures reveal that different compounds induce various conformations of the FMN riboswitch, leading to different activity profiles. Our findings validate the ALIS platform for HTS screening for RNA-binding small molecules and further demonstrate that ncRNA can be broadly targeted by chemically diverse yet selective small molecules as therapeutics.
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Affiliation(s)
- Noreen F. Rizvi
- Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | - John A. Howe
- Merck & Co., Inc., Kenilworth, New Jersey 07033, United States
| | - Ali Nahvi
- Merck & Co., Inc., West Point, Pennsylvania 19486, United States
| | - Daniel J. Klein
- Merck & Co., Inc., West Point, Pennsylvania 19486, United States
| | | | - Hai-Young Kim
- Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | - Mark A. McCoy
- Merck & Co., Inc., Kenilworth, New Jersey 07033, United States
| | - Scott S. Walker
- Merck & Co., Inc., Kenilworth, New Jersey 07033, United States
| | - Alan Hruza
- Merck & Co., Inc., Kenilworth, New Jersey 07033, United States
| | | | - Chad Chamberlin
- Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | - Peter Saradjian
- Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | | | - Gabriel Mercado
- Biodesy, Inc., South San Francisco, California 94080, United States
| | - Julja Burchard
- Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | | | | | - Graham F. Smith
- Merck & Co., Inc., Boston, Massachusetts 02115, United States
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46
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Gong S, Wang Y, Wang Z, Sun Y, Zhang W. Folding behaviors of purine riboswitch aptamers. ACTA ACUST UNITED AC 2018. [DOI: 10.1007/s11859-018-1292-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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47
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Uhm H, Hohng S. Ligand Recognition Mechanism of Thiamine Pyrophosphate Riboswitch Aptamer. B KOREAN CHEM SOC 2017. [DOI: 10.1002/bkcs.11328] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Heesoo Uhm
- Department of Physics and Astronomy; Seoul National University; Seoul 151-747 Korea
- National Center of Creative Research Initiatives; Seoul National University; Seoul 151-747 Korea
| | - Sungchul Hohng
- Department of Physics and Astronomy; Seoul National University; Seoul 151-747 Korea
- National Center of Creative Research Initiatives; Seoul National University; Seoul 151-747 Korea
- Department of Biophysics and Chemical Biology; Seoul National University; Seoul 151-747 Korea
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48
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Stagno JR, Bhandari YR, Conrad CE, Liu Y, Wang YX. Real-time crystallographic studies of the adenine riboswitch using an X-ray free-electron laser. FEBS J 2017; 284:3374-3380. [PMID: 28504865 DOI: 10.1111/febs.14110] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/27/2017] [Accepted: 05/12/2017] [Indexed: 11/26/2022]
Abstract
Structures of the four reaction states of the adenine riboswitch aptamer domain, including a transient intermediate state were solved by serial femtosecond crystallography. The structures not only demonstrate the use of X-ray free-electron lasers for RNA crystallography but have also proven that transient states can be determined in real time by mix-and-inject crystallography. These results illustrate the structural basis for the ligand-induced conformational changes associated with the molecular 'switch'.
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Affiliation(s)
- Jason R Stagno
- Structural Biophysics Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Yuba R Bhandari
- Structural Biophysics Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Chelsie E Conrad
- Structural Biophysics Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Yu Liu
- Structural Biophysics Laboratory, National Cancer Institute, Frederick, MD, USA
| | - Yun-Xing Wang
- Structural Biophysics Laboratory, National Cancer Institute, Frederick, MD, USA
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49
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An excited state underlies gene regulation of a transcriptional riboswitch. Nat Chem Biol 2017; 13:968-974. [PMID: 28719589 PMCID: PMC5562522 DOI: 10.1038/nchembio.2427] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 05/22/2017] [Indexed: 11/08/2022]
Abstract
Riboswitches control gene expression through ligand-dependent structural rearrangements of the sensing aptamer domain. However, we found that the Bacillus cereus fluoride riboswitch aptamer adopts identical tertiary structures in solution with and without ligand. Using chemical-exchange saturation transfer (CEST) NMR spectroscopy, we revealed that the structured ligand-free aptamer transiently accesses a low-populated (∼1%) and short-lived (∼3 ms) excited conformational state that unravels a conserved 'linchpin' base pair to signal transcription termination. Upon fluoride binding, this highly localized, fleeting process is allosterically suppressed, which activates transcription. We demonstrated that this mechanism confers effective fluoride-dependent gene activation over a wide range of transcription rates, which is essential for robust toxicity responses across diverse cellular conditions. These results unveil a novel switching mechanism that employs ligand-dependent suppression of an aptamer excited state to coordinate regulatory conformational transitions rather than adopting distinct aptamer ground-state tertiary architectures, exemplifying a new mode of ligand-dependent RNA regulation.
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50
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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: 53] [Impact Index Per Article: 7.6] [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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