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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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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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Hu G, Zhou HX. Magnesium ions mediate ligand binding and conformational transition of the SAM/SAH riboswitch. Commun Biol 2023; 6:791. [PMID: 37524918 PMCID: PMC10390503 DOI: 10.1038/s42003-023-05175-5] [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: 03/24/2023] [Accepted: 07/24/2023] [Indexed: 08/02/2023] Open
Abstract
The SAM/SAH riboswitch binds S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) with similar affinities. Mg2+ is generally known to stabilize RNA structures by neutralizing phosphates, but how it contributes to ligand binding and conformational transition is understudied. Here, extensive molecular dynamics simulations (totaling 120 μs) predicted over 10 inner-shell Mg2+ ions in the SAM/SAH riboswitch. Six of them line the two sides of a groove to widen it and thereby pre-organize the riboswitch for ligand entry. They also form outer-shell coordination with the ligands and stabilize an RNA-ligand hydrogen bond, which effectively diminishes the selectivity between SAM and SAH. One Mg2+ ion unique to the apo form maintains the Shine-Dalgarno sequence in an autonomous mode and thereby facilitates its release for ribosome binding. Mg2+ thus plays vital roles in SAM/SAH riboswitch function.
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Affiliation(s)
- Guodong Hu
- Shandong Key Laboratory of Biophysics, Dezhou University, Dezhou, 253023, China
- Department of Chemistry, University of Illinois Chicago, Chicago, IL, 60607, USA
| | - Huan-Xiang Zhou
- Department of Chemistry, University of Illinois Chicago, Chicago, IL, 60607, USA.
- Department of Physics, University of Illinois Chicago, Chicago, IL, 60607, USA.
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Hu G, Zhou HX. Magnesium ions mediate ligand binding and conformational transition of the SAM/SAH riboswitch. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.12.532287. [PMID: 36945415 PMCID: PMC10029009 DOI: 10.1101/2023.03.12.532287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
Abstract
The SAM/SAH riboswitch binds S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) with similar affinities. Mg 2+ is generally known to stabilize RNA structures by neutralizing phosphates, but how it contributes to ligand binding and conformational transition is understudied. Here, extensive molecular dynamics simulations (totaling 120 μs) identified over 10 inner-shell Mg 2+ ions in the SAM/SAH riboswitch. Six of them line the two sides of a groove to widen it and thereby pre-organize the riboswitch for ligand entry. They also form outer-shell coordination with the ligands and stabilize an RNA-ligand hydrogen bond, which effectively diminish the selectivity between SAM and SAH. One Mg 2+ ion unique to the apo form maintains the Shine-Dalgarno sequence in an autonomous mode and thereby facilitates its release for ribosome binding. Mg 2+ thus plays vital roles in SAM/SAH riboswitch function.
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Affiliation(s)
- Guodong Hu
- Shandong Key Laboratory of Biophysics, Dezhou University, Dezhou 253023, China
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607
| | - Huan-Xiang Zhou
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607
- Department of Physics, University of Illinois Chicago, Chicago, IL 60607
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