1
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Niu X, Xu Z, Zhang Y, Zuo X, Chen C, Fang X. Structural and dynamic mechanisms for coupled folding and tRNA recognition of a translational T-box riboswitch. Nat Commun 2023; 14:7394. [PMID: 37968328 PMCID: PMC10651847 DOI: 10.1038/s41467-023-43232-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 11/03/2023] [Indexed: 11/17/2023] Open
Abstract
T-box riboswitches are unique riboregulators where gene regulation is mediated through interactions between two highly structured RNAs. Despite extensive structural insights, how RNA-RNA interactions drive the folding and structural transitions of T-box to achieve functional conformations remains unclear. Here, by combining SAXS, single-molecule FRET and computational modeling, we elaborate the folding energy landscape of a translational T-box aptamer consisting of stems I, II and IIA/B, which Mg2+-induced global folding and tRNA binding are cooperatively coupled. smFRET measurements reveal that high Mg2+ stabilizes IIA/B and its stacking on II, which drives the pre-docking of I and II into a competent conformation, subsequent tRNA binding promotes docking of I and II to form a high-affinity tRNA binding groove, of which the essentiality of IIA/B and S-turn in II is substantiated with mutational analysis. We highlight a delicate balance among Mg2+, the intra- and intermolecular RNA-RNA interactions in modulating RNA folding and function.
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Affiliation(s)
- Xiaolin Niu
- Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Zhonghe Xu
- Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Yufan Zhang
- Key Laboratory of RNA Science and Engineering, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Xiaobing Zuo
- X-ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Chunlai Chen
- Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China.
| | - Xianyang Fang
- Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- Key Laboratory of RNA Science and Engineering, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
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2
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Liang Y, Qie Y, Yang J, Wu R, Cui S, Zhao Y, Anderson GJ, Nie G, Li S, Zhang C. Programming conformational cooperativity to regulate allosteric protein-oligonucleotide signal transduction. Nat Commun 2023; 14:4898. [PMID: 37580346 PMCID: PMC10425332 DOI: 10.1038/s41467-023-40589-z] [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: 03/13/2023] [Accepted: 08/03/2023] [Indexed: 08/16/2023] Open
Abstract
Conformational cooperativity is a universal molecular effect mechanism and plays a critical role in signaling pathways. However, it remains a challenge to develop artificial molecular networks regulated by conformational cooperativity, due to the difficulties in programming and controlling multiple structural interactions. Herein, we develop a cooperative strategy by programming multiple conformational signals, rather than chemical signals, to regulate protein-oligonucleotide signal transduction, taking advantage of the programmability of allosteric DNA constructs. We generate a cooperative regulation mechanism, by which increasing the loop lengths at two different structural modules induced the opposite effects manifesting as down- and up-regulation. We implement allosteric logic operations by using two different proteins. Further, in cell culture we demonstrate the feasibility of this strategy to cooperatively regulate gene expression of PLK1 to inhibit tumor cell proliferation, responding to orthogonal protein-signal stimulation. This programmable conformational cooperativity paradigm has potential applications in the related fields.
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Affiliation(s)
- Yuan Liang
- School of Computer Science, Key Lab of High Confidence Software Technologies, Peking University, 100871, Beijing, China
- School of Control and Computer Engineering, North China Electric Power University, 102206, Beijing, China
| | - Yunkai Qie
- CAS Key Laboratory for Biomedical Effects of Nanomaterials & Nanosafety, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
- GBA Research Innovation Institute for Nanotechnology, Guangzhou, 510530, China
- Department of Urology, Tianjin Institute of Urology, The Second Hospital of Tianjin Medical University, Tianjin, 300211, China
| | - Jing Yang
- School of Control and Computer Engineering, North China Electric Power University, 102206, Beijing, China
| | - Ranfeng Wu
- School of Computer Science, Key Lab of High Confidence Software Technologies, Peking University, 100871, Beijing, China
| | - Shuang Cui
- School of Computer Science, Key Lab of High Confidence Software Technologies, Peking University, 100871, Beijing, China
| | - Yuliang Zhao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials & Nanosafety, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
- GBA Research Innovation Institute for Nanotechnology, Guangzhou, 510530, China
| | - Greg J Anderson
- QIMR Berghofer Medical Research Institute, Royal Brisbane Hospital, Herston, Queensland, 4029, Australia
| | - Guangjun Nie
- CAS Key Laboratory for Biomedical Effects of Nanomaterials & Nanosafety, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
- GBA Research Innovation Institute for Nanotechnology, Guangzhou, 510530, China
| | - Suping Li
- CAS Key Laboratory for Biomedical Effects of Nanomaterials & Nanosafety, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190, Beijing, China.
- University of Chinese Academy of Sciences, 100049, Beijing, China.
- GBA Research Innovation Institute for Nanotechnology, Guangzhou, 510530, China.
| | - Cheng Zhang
- School of Computer Science, Key Lab of High Confidence Software Technologies, Peking University, 100871, Beijing, China.
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3
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Nuthanakanti A, Ariza-Mateos A, Serganov A. X-Ray Crystallography to Study Conformational Changes in a TPP Riboswitch. Methods Mol Biol 2023; 2568:213-232. [PMID: 36227571 DOI: 10.1007/978-1-0716-2687-0_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Conformational rearrangements are key to the function of riboswitches. These regulatory mRNA regions specifically bind to cellular metabolites using evolutionarily conserved sensing domains and modulate gene expression via adjacent downstream expression platforms, which carry gene expression signals. The regulation is achieved through the ligand-dependent formation of two alternative and mutually exclusive conformations involving the same RNA region. While X-ray crystallography cannot visualize dynamics of such dramatic conformational rearrangements, this method is pivotal to understand RNA-ligand interaction that stabilize the sensing domain and drive folding of the expression platform. X-ray crystallography can reveal local changes in RNA necessary for discriminating cognate and noncognate ligands. This chapter describes preparation of thiamine pyrophosphate riboswitch RNAs and its crystallization with different ligands, resulting in structures with local conformational changes in RNA. These structures can help to derive information on the dynamics of the RNA essential for specific binding to small molecules, with potential for using this information for developing designer riboswitch-ligand systems.
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Affiliation(s)
- Ashok Nuthanakanti
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Ascensión Ariza-Mateos
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Alexander Serganov
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.
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4
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Sapkota KP, Li S, Zhang J. Cotranscriptional Assembly and Native Purification of Large RNA-RNA Complexes for Structural Analyses. Methods Mol Biol 2023; 2568:1-12. [PMID: 36227558 DOI: 10.1007/978-1-0716-2687-0_1] [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] [Indexed: 06/16/2023]
Abstract
Recent technological developments such as cryogenic electron microscopy (Cryo-EM) and X-ray free electron lasers (XFEL) have significantly expanded the available toolkit to visualize large, complex noncoding RNAs and their complexes. Consequently, the quality of the RNA sample, as measured by its chemical monodispersity and conformational homogeneity, has become the bottleneck that frequently precludes effective structural analyses. Here we describe a general RNA sample preparation protocol that combines cotranscriptional RNA folding and RNA-RNA complex assembly, followed by native purification of stoichiometric complexes. We illustrate and discuss the utility of this versatile method in overcoming RNA misfolding and enabling the structural and mechanistic elucidations of the T-box riboswitch-tRNA complexes.
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Affiliation(s)
- Krishna P Sapkota
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA
| | - Shuang Li
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA
- Structural Biochemistry Unit, National Institute of Dental and Craniofacial Research, Bethesda, MD, USA
| | - Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA.
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5
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Gorbea C, Elhakiem A, Cazalla D. Allosteric regulation of noncoding RNA function by microRNAs. Nucleic Acids Res 2022; 50:6511-6520. [PMID: 35648438 PMCID: PMC9226524 DOI: 10.1093/nar/gkac443] [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] [Received: 03/10/2022] [Revised: 04/17/2022] [Accepted: 05/10/2022] [Indexed: 12/12/2022] Open
Abstract
HSUR1 and HSUR2, two noncoding RNAs expressed by the oncogenic Herpesvirus saimiri, bind host microRNAs miR-142-3p, miR-16, and miR-27 with different purposes. While binding of miR-27 to HSUR1 triggers the degradation of the microRNA, miR-16 is tethered by HSUR2 to target host mRNAs to repress their expression. Here we show that the interaction with miR-142-3p is required for the activity of both HSURs. Coimmunoprecipitation experiments revealed that miR-142-3p allosterically regulates the binding of miR-27 and miR-16 to HSUR1 and HSUR2, respectively. The binding of two different miRNAs to each HSUR is not cooperative. HSURs can be engineered to be regulated by other miRNAs, indicating that the identity of the binding miRNA is not important for HSUR regulation. Our results uncover a mechanism for allosteric regulation of noncoding RNA function and a previously unappreciated way in which microRNAs can regulate gene expression.
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Affiliation(s)
- Carlos Gorbea
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Abdalla Elhakiem
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Demián Cazalla
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
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6
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Abstract
In-cell structural biology aims at extracting structural information about proteins or nucleic acids in their native, cellular environment. This emerging field holds great promise and is already providing new facts and outlooks of interest at both fundamental and applied levels. NMR spectroscopy has important contributions on this stage: It brings information on a broad variety of nuclei at the atomic scale, which ensures its great versatility and uniqueness. Here, we detail the methods, the fundamental knowledge, and the applications in biomedical engineering related to in-cell structural biology by NMR. We finally propose a brief overview of the main other techniques in the field (EPR, smFRET, cryo-ET, etc.) to draw some advisable developments for in-cell NMR. In the era of large-scale screenings and deep learning, both accurate and qualitative experimental evidence are as essential as ever to understand the interior life of cells. In-cell structural biology by NMR spectroscopy can generate such a knowledge, and it does so at the atomic scale. This review is meant to deliver comprehensive but accessible information, with advanced technical details and reflections on the methods, the nature of the results, and the future of the field.
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Affiliation(s)
- Francois-Xavier Theillet
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
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7
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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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8
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Pseudoknot length modulates the folding, conformational dynamics, and robustness of Xrn1 resistance of flaviviral xrRNAs. Nat Commun 2021; 12:6417. [PMID: 34741027 PMCID: PMC8571300 DOI: 10.1038/s41467-021-26616-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 10/04/2021] [Indexed: 01/15/2023] Open
Abstract
To understand how RNA dynamics is regulated and connected to its function, we investigate the folding, conformational dynamics and robustness of Xrn1 resistance of a set of flaviviral xrRNAs using SAXS, smFRET and in vitro enzymatic assays. Flaviviral xrRNAs form discrete ring-like 3D structures, in which the length of a conserved long-range pseudoknot (PK2) ranges from 2 bp to 7 bp. We find that xrRNAs' folding, conformational dynamics and Xrn1 resistance are strongly correlated and highly Mg2+-dependent, furthermore, the Mg2+-dependence is modulated by PK2 length variations. xrRNAs with long PK2 require less Mg2+ to stabilize their folding, exhibit reduced conformational dynamics and strong Xrn1 resistance even at low Mg2+, and tolerate mutations at key tertiary motifs at high Mg2+, which generally are destructive to xrRNAs with short PK2. These results demonstrate an unusual regulatory mechanism of RNA dynamics providing insights into the functions and future biomedical applications of xrRNAs.
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9
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Chen H, Egger M, Xu X, Flemmich L, Krasheninina O, Sun A, Micura R, Ren A. Structural distinctions between NAD+ riboswitch domains 1 and 2 determine differential folding and ligand binding. Nucleic Acids Res 2020; 48:12394-12406. [PMID: 33170270 PMCID: PMC7708056 DOI: 10.1093/nar/gkaa1029] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/12/2020] [Accepted: 10/16/2020] [Indexed: 11/13/2022] Open
Abstract
Riboswitches are important gene regulatory elements frequently encountered in bacterial mRNAs. The recently discovered nadA riboswitch contains two similar, tandemly arrayed aptamer domains, with the first domain possessing high affinity for nicotinamide adenine dinucleotide (NAD+). The second domain which comprises the ribosomal binding site in a putative regulatory helix, however, has withdrawn from detection of ligand-induced structural modulation thus far, and therefore, the identity of the cognate ligand and the regulation mechanism have remained unclear. Here, we report crystal structures of both riboswitch domains, each bound to NAD+. Furthermore, we demonstrate that ligand binding to domain 2 requires significantly higher concentrations of NAD+ (or ADP retaining analogs) compared to domain 1. Using a fluorescence spectroscopic approach, we further shed light on the structural features which are responsible for the different ligand affinities, and describe the Mg2+-dependent, distinct folding and pre-organization of their binding pockets. Finally, we speculate about possible scenarios for nadA RNA gene regulation as a putative two-concentration sensor module for a time-controlled signal that is primed and stalled by the gene regulation machinery at low ligand concentrations (domain 1), and finally triggers repression of translation as soon as high ligand concentrations are reached in the cell (domain 2).
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Affiliation(s)
- Hao Chen
- Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Michaela Egger
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, 6020, Austria
| | - Xiaochen Xu
- Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Laurin Flemmich
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, 6020, Austria
| | - Olga Krasheninina
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, 6020, Austria
| | - Aiai Sun
- School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-lane Xiangshan, Hangzhou 310024, China
| | - Ronald Micura
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, 6020, Austria
| | - Aiming Ren
- Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
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10
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Cooperativity and Allostery in RNA Systems. Methods Mol Biol 2020; 2253:255-271. [PMID: 33315228 DOI: 10.1007/978-1-0716-1154-8_15] [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: 03/15/2023]
Abstract
Allostery is among the most basic biological principles employed by biological macromolecules to achieve a biologically active state in response to chemical cues. Although initially used to describe the impact of small molecules on the conformation and activity of protein enzymes, the definition of this term has been significantly broadened to describe long-range conformational change of macromolecules in response to small or large effectors. Such a broad definition could be applied to RNA molecules, which do not typically serve as protein-free cellular enzymes but fold and form macromolecular assemblies with the help of various ligand molecules, including ions and proteins. Ligand-induced allosteric changes in RNA molecules are often accompanied by cooperative interactions between RNA and its ligand, thus streamlining the folding and assembly pathways. This chapter provides an overview of the interplay between cooperativity and allostery in RNA systems and outlines methods to study these two biological principles.
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11
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Giampà M, Sgobba E. Insight to Functional Conformation and Noncovalent Interactions of Protein-Protein Assembly Using MALDI Mass Spectrometry. Molecules 2020; 25:E4979. [PMID: 33126406 PMCID: PMC7662314 DOI: 10.3390/molecules25214979] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 10/22/2020] [Accepted: 10/24/2020] [Indexed: 11/16/2022] Open
Abstract
Noncovalent interactions are the keys to the structural organization of biomolecule e.g., proteins, glycans, lipids in the process of molecular recognition processes e.g., enzyme-substrate, antigen-antibody. Protein interactions lead to conformational changes, which dictate the functionality of that protein-protein complex. Besides biophysics techniques, noncovalent interaction and conformational dynamics, can be studied via mass spectrometry (MS), which represents a powerful tool, due to its low sample consumption, high sensitivity, and label-free sample. In this review, the focus will be placed on Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS) and its role in the analysis of protein-protein noncovalent assemblies exploring the relationship within noncovalent interaction, conformation, and biological function.
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Affiliation(s)
- Marco Giampà
- MR Cancer Group, Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Olav Kyrres Gate 9, 7030 Trondheim, Norway
| | - Elvira Sgobba
- Genetics and Plant Physiology, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden;
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12
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Pandey S, Li Y, Young MD, Mandal S, Lu L, Shelley JT, Mao H. Cooperative Heteroligand Interaction with G-Quadruplexes Shows Evidence of Allosteric Binding. Biochemistry 2020; 59:3438-3446. [PMID: 32833433 PMCID: PMC7511437 DOI: 10.1021/acs.biochem.0c00351] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although allosteric binding of small molecules is commonplace in protein structures, it is rather rare in DNA species such as G-quadruplexes. By using CD melting, here, we found binding of the small-molecule ligands PDS and L2H2-6OTD to the telomeric DNA G-quadruplex was cooperative. Mass spectrometry indicated a 1:1:1 ratio in the ternary binding complex of the telomeric G-quadruplex, PDS, and L2H2-6OTD. Compared to the binding of each individual ligand to the G-quadruplex, single-molecule mechanical unfolding assays revealed a significantly decreased dissociation constant when one ligand is evaluated in the presence of another. This demonstrates that cooperative binding of PDS and L2H2-6OTD to the G-quadruplex is allosteric, which is also supported by the mass spectra data that indicated the ejection of coordinated sodium ions upon binding of the heteroligands to the G-quadruplex. The unprecedented observation of the allosteric ligand binding to higher-ordered structures of DNA may help to design more effective ligands to target non-B DNA species involved in many critical cellular processes.
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Affiliation(s)
- Shankar Pandey
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio, 44242, USA
| | - Yuanyuan Li
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio, 44242, USA
- Department of Pharmacy, Daping Hospital, Army Medical University, Chongqing, 400042, China
| | - Montwaun D. Young
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Shankar Mandal
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio, 44242, USA
| | - Laichun Lu
- National Institute for Drug Clinical Trial, Beijing Tongren Hospital, Capital Medical University, 1 Dongjiaominxiang Road, Beijing, 100730, China
| | - Jacob T. Shelley
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Hanbin Mao
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio, 44242, USA
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13
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Micura R, Höbartner C. Fundamental studies of functional nucleic acids: aptamers, riboswitches, ribozymes and DNAzymes. Chem Soc Rev 2020; 49:7331-7353. [PMID: 32944725 DOI: 10.1039/d0cs00617c] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
This review aims at juxtaposing common versus distinct structural and functional strategies that are applied by aptamers, riboswitches, and ribozymes/DNAzymes. Focusing on recently discovered systems, we begin our analysis with small-molecule binding aptamers, with emphasis on in vitro-selected fluorogenic RNA aptamers and their different modes of ligand binding and fluorescence activation. Fundamental insights are much needed to advance RNA imaging probes for detection of exo- and endogenous RNA and for RNA process tracking. Secondly, we discuss the latest gene expression-regulating mRNA riboswitches that respond to the alarmone ppGpp, to PRPP, to NAD+, to adenosine and cytidine diphosphates, and to precursors of thiamine biosynthesis (HMP-PP), and we outline new subclasses of SAM and tetrahydrofolate-binding RNA regulators. Many riboswitches bind protein enzyme cofactors that, in principle, can catalyse a chemical reaction. For RNA, however, only one system (glmS ribozyme) has been identified in Nature thus far that utilizes a small molecule - glucosamine-6-phosphate - to participate directly in reaction catalysis (phosphodiester cleavage). We wonder why that is the case and what is to be done to reveal such likely existing cellular activities that could be more diverse than currently imagined. Thirdly, this brings us to the four latest small nucleolytic ribozymes termed twister, twister-sister, pistol, and hatchet as well as to in vitro selected DNA and RNA enzymes that promote new chemistry, mainly by exploiting their ability for RNA labelling and nucleoside modification recognition. Enormous progress in understanding the strategies of nucleic acids catalysts has been made by providing thorough structural fundaments (e.g. first structure of a DNAzyme, structures of ribozyme transition state mimics) in combination with functional assays and atomic mutagenesis.
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Affiliation(s)
- Ronald Micura
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck CMBI, Leopold-Franzens University Innsbruck, Innsbruck, Austria.
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14
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Rational design to control the trade-off between receptor affinity and cooperativity. Proc Natl Acad Sci U S A 2020; 117:19136-19140. [PMID: 32727893 DOI: 10.1073/pnas.2006254117] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cooperativity enhances the responsiveness of biomolecular receptors to small changes in the concentration of their target ligand, albeit with a concomitant reduction in affinity. The binding midpoint of a two-site receptor with a Hill coefficient of 1.9, for example, must be at least 19 times higher than the dissociation constant of the higher affinity of its two binding sites. This trade-off can be overcome, however, by the extra binding energy provided by the addition of more binding sites, which can be used to achieve highly cooperative receptors that still retain high affinity. Exploring this experimentally, we have employed an "intrinsic disorder" mechanism to design two cooperative, three-binding-site receptors starting from a single-site-and thus noncooperative-doxorubicin-binding aptamer. The first receptor follows a binding energy landscape that partitions the energy provided by the additional binding event to favor affinity, achieving a Hill coefficient of 1.9 but affinity within a factor of 2 of the parent aptamer. The binding energy landscape of the second receptor, in contrast, partitions more of this energy toward cooperativity, achieving a Hill coefficient of 2.3, but at the cost of 4-fold poorer affinity than that of the parent aptamer. The switch between these two behaviors is driven primarily by the affinity of the receptors' second binding event, which serves as an allosteric "gatekeeper" defining the extent to which the system is weighted toward higher cooperativity or higher affinity.
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15
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Structural Insights into RNA Dimerization: Motifs, Interfaces and Functions. Molecules 2020; 25:molecules25122881. [PMID: 32585844 PMCID: PMC7357161 DOI: 10.3390/molecules25122881] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 12/26/2022] Open
Abstract
In comparison with the pervasive use of protein dimers and multimers in all domains of life, functional RNA oligomers have so far rarely been observed in nature. Their diminished occurrence contrasts starkly with the robust intrinsic potential of RNA to multimerize through long-range base-pairing ("kissing") interactions, self-annealing of palindromic or complementary sequences, and stable tertiary contact motifs, such as the GNRA tetraloop-receptors. To explore the general mechanics of RNA dimerization, we performed a meta-analysis of a collection of exemplary RNA homodimer structures consisting of viral genomic elements, ribozymes, riboswitches, etc., encompassing both functional and fortuitous dimers. Globally, we found that domain-swapped dimers and antiparallel, head-to-tail arrangements are predominant architectural themes. Locally, we observed that the same structural motifs, interfaces and forces that enable tertiary RNA folding also drive their higher-order assemblies. These feature prominently long-range kissing loops, pseudoknots, reciprocal base intercalations and A-minor interactions. We postulate that the scarcity of functional RNA multimers and limited diversity in multimerization motifs may reflect evolutionary constraints imposed by host antiviral immune surveillance and stress sensing. A deepening mechanistic understanding of RNA multimerization is expected to facilitate investigations into RNA and RNP assemblies, condensates, and granules and enable their potential therapeutical targeting.
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Ding J, Swain M, Yu P, Stagno JR, Wang YX. Conformational flexibility of adenine riboswitch aptamer in apo and bound states using NMR and an X-ray free electron laser. JOURNAL OF BIOMOLECULAR NMR 2019; 73:509-518. [PMID: 31606878 PMCID: PMC6817744 DOI: 10.1007/s10858-019-00278-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 09/12/2019] [Indexed: 06/10/2023]
Abstract
Riboswitches are structured cis-regulators mainly found in the untranslated regions of messenger RNA. The aptamer domain of a riboswitch serves as a sensor for its ligand, the binding of which triggers conformational changes that regulate the behavior of its expression platform. As a model system for understanding riboswitch structures and functions, the add adenine riboswitch has been studied extensively. However, there is a need for further investigation of the conformational dynamics of the aptamer in light of the recent real-time crystallographic study at room temperature (RT) using an X-ray free electron laser (XFEL) and femtosecond X-ray crystallography (SFX). Herein, we investigate the conformational motions of the add adenine riboswitch aptamer domain, in the presence or absence of adenine, using nuclear magnetic resonance relaxation measurements and analysis of RT atomic displacement factors (B-factors). In the absence of ligand, the P1 duplex undergoes a fast exchange where the overall molecule exhibits a motion at kex ~ 319 s-1, based on imino signals. In the presence of ligand, the P1 duplex adopts a highly ordered conformation, with kex~ 83 s-1, similar to the global motion of the molecule, excluding the loops and binding pocket, at 84 s-1. The µs-ms motions in both the apo and bound states are consistent with RT B-factors. Reduced spatial atomic fluctuation, ~ 50%, in P1 upon ligand binding coincides with significantly attenuated temporal dynamic exchanges. The binding pocket is structured in the absence or presence of ligand, as evidenced by relatively low and similar RT B-factors. Therefore, despite the dramatic rearrangement of the binding pocket, those residues exhibit similar spatial thermal fluctuation before and after binding.
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Affiliation(s)
- Jienv Ding
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, National Institute of Health, Frederick, MD, 21702, USA.
| | - Monalisa Swain
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, National Institute of Health, Frederick, MD, 21702, USA
| | - Ping Yu
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, National Institute of Health, Frederick, MD, 21702, USA
| | - Jason R Stagno
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, National Institute of Health, Frederick, MD, 21702, USA
| | - Yun-Xing Wang
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, National Institute of Health, Frederick, MD, 21702, USA.
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Sung HL, Nesbitt DJ. Single-Molecule FRET Kinetics of the Mn 2+ Riboswitch: Evidence for Allosteric Mg 2+ Control of "Induced-Fit" vs "Conformational Selection" Folding Pathways. J Phys Chem B 2019; 123:2005-2015. [PMID: 30739441 DOI: 10.1021/acs.jpcb.8b11841] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Gene expression in bacteria is often regulated dynamically by conformational changes in a riboswitch upon ligand binding, a detailed understanding of which is very much in its infancy. For example, the manganese riboswitch is a widespread RNA motif that conformationally responds in regulating bacterial gene expression to micromolar levels of its eponymous ligand, Mn2+, but the mechanistic pathways are poorly understood. In this work, we quantitatively explore the dynamic folding behavior of the manganese riboswitch by single-molecule fluorescence resonance energy transfer spectroscopy as a function of cation/ligand conditions. From the detailed analysis of the kinetics, the Mn2+ is shown to fold the riboswitch by a "bind-then-fold" (i.e., "induced-fit", IF) mechanism, whereby the ligand binds first and then promotes folding. On the other hand, the data also clearly reveal the presence of a folded yet ligand-free structure predominating due to the addition of physiological Mg2+ to a nonselective metal ion binding site. Of particular kinetic interest, such a Mg2+ "prefolded" conformation of the riboswitch is shown to exhibit a significantly increased affinity for Mn2+ and further stabilization by subsequent binding of the ligand, thereby promoting efficient riboswitch folding by a "fold-then-bind" (i.e., "conformational selection", CS) mechanism. Our results not only demonstrate Mg2+-controlled switching between IF and CS riboswitch folding pathways but also suggest a novel heterotropic allosteric control in the manganese riboswitch activity co-regulated by Mg2+ binding.
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Noro E, Mori M, Makino G, Takai Y, Ohnuma S, Sato A, Tomita M, Nakahigashi K, Kanai A. Systematic characterization of artificial small RNA-mediated inhibition of Escherichia coli growth. RNA Biol 2016; 14:206-218. [PMID: 27981881 PMCID: PMC5324740 DOI: 10.1080/15476286.2016.1270001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A new screening system for artificial small RNAs (sRNAs) that inhibit the growth of Escherichia coli was constructed. In this system, we used a plasmid library to express RNAs of ∼120 nucleotides, each with a random 30-nucleotide sequence that can recognize its target mRNA(s). After approximately 60,000 independent colonies were screened, several plasmids that inhibited bacterial growth were isolated. To understand the inhibitory mechanism, we focused on one sRNA, S-20, that exerted a strong inhibitory effect. A time-course analysis of the proteome of S-20-expressing E. coli and a bioinformatic analysis were used to identify potential S-20 target mRNAs, and suggested that S-20 binds the translation initiation sites of several mRNAs encoding enzymes such as peroxiredoxin (osmC), glycyl-tRNA synthetase α subunit (glyQ), uncharacterized protein ygiM, and tryptophan synthase β chain (trpB). An in vitro translation analysis of chimeric luciferase-encoding mRNAs, each containing a potential S-20 target sequence, indicated that the translation of these mRNAs was inhibited in the presence of S-20. A gel shift analysis combined with the analysis of a series of S-20 mutants suggested that S-20 targets multiple mRNAs that are responsible for inhibiting E. coli growth. These data also suggest that S-20 acts like an endogenous sRNA and that E. coli can utilize artificial sRNAs.
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Affiliation(s)
- Emiko Noro
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan
| | - Masaru Mori
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan.,b Systems Biology Program, Graduate School of Media and Governance, Keio University , Fujisawa , Japan
| | - Gakuto Makino
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan.,c Faculty of Environment and Information Studies, Keio University , Fujisawa , Japan
| | - Yuki Takai
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan
| | - Sumiko Ohnuma
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan
| | - Asako Sato
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan
| | - Masaru Tomita
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan.,b Systems Biology Program, Graduate School of Media and Governance, Keio University , Fujisawa , Japan.,c Faculty of Environment and Information Studies, Keio University , Fujisawa , Japan
| | - Kenji Nakahigashi
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan.,b Systems Biology Program, Graduate School of Media and Governance, Keio University , Fujisawa , Japan
| | - Akio Kanai
- a Institute for Advanced Biosciences, Keio University , Tsuruoka , Japan.,b Systems Biology Program, Graduate School of Media and Governance, Keio University , Fujisawa , Japan.,c Faculty of Environment and Information Studies, Keio University , Fujisawa , Japan
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Ruff KM, Muhammad A, McCown PJ, Breaker RR, Strobel SA. Singlet glycine riboswitches bind ligand as well as tandem riboswitches. RNA (NEW YORK, N.Y.) 2016; 22:1728-1738. [PMID: 27659053 PMCID: PMC5066625 DOI: 10.1261/rna.057935.116] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 08/23/2016] [Indexed: 05/21/2023]
Abstract
The glycine riboswitch often occurs in a tandem architecture, with two ligand-binding domains (aptamers) followed by a single expression platform. Based on previous observations, we hypothesized that "singlet" versions of the glycine riboswitch, which contain only one aptamer domain, are able to bind glycine if appropriate structural contacts are maintained. An initial alignment of 17 putative singlet riboswitches indicated that the single consensus aptamer domain is flanked by a conserved peripheral stem-loop structure. These singlets were sorted into two subtypes based on whether the active aptamer domain precedes or follows the peripheral stem-loop, and an example of each subtype of singlet riboswitch was characterized biochemically. The singlets possess glycine-binding affinities comparable to those of previously published tandem examples, and the conserved peripheral domains form A-minor interactions with the single aptamer domain that are necessary for ligand-binding activity. Analysis of sequenced genomes identified a significant number of singlet glycine riboswitches. Based on these observations, we propose an expanded model for glycine riboswitch gene control that includes singlet and tandem architectures.
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Affiliation(s)
- Karen M Ruff
- Department of Molecular Biophysics and Biochemistry
| | | | - Phillip J McCown
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8114, USA
| | - Ronald R Breaker
- Department of Molecular Biophysics and Biochemistry
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8114, USA
- Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06520-8114, USA
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Saunders AM, DeRose VJ. Beyond Mg 2+: functional interactions between RNA and transition metals. Curr Opin Chem Biol 2016; 34:152-158. [PMID: 27616014 DOI: 10.1016/j.cbpa.2016.07.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
It is well-known that RNA structure and function depend heavily on cations, and the ability of Mg2+ to stabilize RNA structures has been emphasized. Recent studies, however, highlight the importance of transition metals in RNA function. Riboswitches that selectively bind Ni2+, Co2+, and Mn2+ have been discovered with specific RNA-metal sites that influence metal-related gene expression. Exogenous metals such as Pt(II) from therapeutics also bind and may inhibit cellular RNA function. Novel reports that RNA can host Fe(II) in catalytic sites are relevant to early life in pre-oxygenic atmospheres. These new observations emphasize the importance of transition metals in the field of RNA metallobiochemistry.
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Affiliation(s)
- Adam M Saunders
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon Eugene, OR 97403, United States
| | - Victoria J DeRose
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon Eugene, OR 97403, United States.
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21
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Ketterer S, Gladis L, Kozica A, Meier M. Engineering and characterization of fluorogenic glycine riboswitches. Nucleic Acids Res 2016; 44:5983-92. [PMID: 27220466 PMCID: PMC4937332 DOI: 10.1093/nar/gkw465] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 05/15/2016] [Indexed: 11/20/2022] Open
Abstract
A set of 12 fluorogenic glycine riboswitches with different thermodynamic and kinetic response properties was engineered. For the design of functional riboswitches, a three-part RNA approach was applied based on the idea of linking a RNA sensor, transmitter and actuator part together. For the RNA sensor and actuator part, we used the tandem glycine aptamer structure from Bacillus subtillis, and fluorogenic aptamer Spinach, respectively. To achieve optimal signal transduction from the sensor to the actuator, a riboswitch library with variable transmitter was screened with a microfluidic large-scale integration chip. This allowed us to establish the complete thermodynamic binding profiles of the riboswitch library. Glycine dissociation constants of the 12 strong fluorescence response riboswitches varied between 99.7 and 570 μM. Furthermore, the kinetic glycine binding (kon), and dissociation (koff) rates, and corresponding energy barriers of the 10 strongest fluorescence response riboswitches were determined with the same chip platform. kon and koff were in the order of 10−3s−1 and 10−2s−1, respectively. Conclusively, we demonstrate that systematic screening of synthetic and natural linked RNA parts with microfluidic chip technology is an effective approach to rapidly generate fluorogenic metabolite riboswitches with a broad range of biophysical response properties.
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Affiliation(s)
- Simon Ketterer
- Microfluidic and Biological Engineering, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany Centre for Biological Signalling Studies-BIOSS, University of Freiburg, Schänzlestrasse 18, 79104 Freiburg, Germany
| | - Lukas Gladis
- Microfluidic and Biological Engineering, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany Centre for Biological Signalling Studies-BIOSS, University of Freiburg, Schänzlestrasse 18, 79104 Freiburg, Germany
| | - Adnan Kozica
- Microfluidic and Biological Engineering, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany Centre for Biological Signalling Studies-BIOSS, University of Freiburg, Schänzlestrasse 18, 79104 Freiburg, Germany
| | - Matthias Meier
- Microfluidic and Biological Engineering, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany Centre for Biological Signalling Studies-BIOSS, University of Freiburg, Schänzlestrasse 18, 79104 Freiburg, Germany
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22
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Saunders AM, DeRose VJ. Beyond Mg(2+): functional interactions between RNA and transition metals. Curr Opin Chem Biol 2016; 31:153-9. [PMID: 27031926 DOI: 10.1016/j.cbpa.2016.02.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/25/2016] [Indexed: 12/19/2022]
Abstract
It is well-known that RNA structure and function depend heavily on cations, and the ability of Mg(2+) to stabilize RNA structures has been emphasized. Recent studies, however, highlight the importance of transition metals in RNA function. Riboswitches that selectively bind Ni(2+), Co(2+), and Mn(2+) have been discovered with specific RNA-metal sites that influence metal-related gene expression. Exogenous metals such as Pt(II) from therapeutics also bind and may inhibit cellular RNA. Novel reports that RNA can host Fe(II) in catalytic sites are relevant to early life in pre-oxygenic atmospheres. These new observations emphasize the importance of transition metals in the field of RNA metallobiochemistry.
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Affiliation(s)
- Adam M Saunders
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon Eugene, OR 97403, United States
| | - Victoria J DeRose
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon Eugene, OR 97403, United States.
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Halbmair K, Seikowski J, Tkach I, Höbartner C, Sezer D, Bennati M. High-resolution measurement of long-range distances in RNA: pulse EPR spectroscopy with TEMPO-labeled nucleotides. Chem Sci 2016; 7:3172-3180. [PMID: 29997809 PMCID: PMC6005265 DOI: 10.1039/c5sc04631a] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/01/2016] [Indexed: 01/02/2023] Open
Abstract
Distance measurements in RNAs by pulse EPR with TEMPO-labeled nucleotides allow for model free conversion of distances into base-pair separation.
Structural information at atomic resolution of biomolecular assemblies, such as RNA and RNA protein complexes, is fundamental to comprehend biological function. Modern spectroscopic methods offer exceptional opportunities in this direction. Here we present the capability of pulse EPR to report high-resolution long-range distances in RNAs by means of a recently developed spin labeled nucleotide, which carries the TEMPO group directly attached to the nucleobase and preserves Watson–Crick base-pairing. In a representative RNA duplex with spin-label separations up to 28 base pairs (≈8 nm) we demonstrate that the label allows for a model-free conversion of inter-spin distances into base-pair separation (Δbp) if broad-band pulse excitation at Q band frequencies (34 GHz) is applied. The observed distance distribution increases from ±0.2 nm for Δbp = 10 to only ±0.5 nm for Δbp = 28, consistent with only small deviations from the “ideal” A-form RNA structure. Molecular dynamics (MD) simulations conducted at 20 °C show restricted conformational freedom of the label. MD-generated structural deviations from an “ideal” A-RNA geometry help disentangle the contributions of local flexibility of the label and its neighboring nucleobases and global deformations of the RNA double helix to the experimental distance distributions. The study demonstrates that our simple but strategic spin labeling procedure can access detailed structural information on RNAs at atomic resolution over distances that match the size of macromolecular RNA complexes.
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Affiliation(s)
- Karin Halbmair
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany .
| | - Jan Seikowski
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany .
| | - Igor Tkach
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany .
| | - Claudia Höbartner
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany . .,Department of Organic and Biomolecular Chemistry , University of Göttingen , 37077 Göttingen , Germany
| | - Deniz Sezer
- Faculty of Engineering and Natural Sciences , Sabanci University , 34956 Istanbul , Turkey .
| | - Marina Bennati
- Max Planck Institute for Biophysical Chemistry , 37077 Göttingen , Germany . .,Department of Organic and Biomolecular Chemistry , University of Göttingen , 37077 Göttingen , Germany
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