1
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Lange B, Gil RG, Anderson GS, Yesselman JD. High-throughput determination of RNA tertiary contact thermodynamics by quantitative DMS chemical mapping. Nucleic Acids Res 2024; 52:9953-9965. [PMID: 39082277 PMCID: PMC11381326 DOI: 10.1093/nar/gkae633] [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: 04/01/2024] [Revised: 06/25/2024] [Accepted: 07/05/2024] [Indexed: 09/10/2024] Open
Abstract
Structured RNAs often contain long-range tertiary contacts that are critical to their function. Despite the importance of tertiary contacts, methods to measure their thermodynamics are low throughput or require specialized instruments. Here, we introduce a new quantitative chemical mapping method (qMaPseq) to measure Mg2+-induced formation of tertiary contact thermodynamics in a high-throughput manner using standard biochemistry equipment. With qMaPseq, we measured the ΔG of 98 unique tetraloop/tetraloop receptor (TL/TLR) variants in a one-pot reaction. These results agree well with measurements from specialized instruments (R2= 0.64). Furthermore, the DMS reactivity of the TL directly correlates to the stability of the contact (R2= 0.68), the first direct evidence that a single DMS reactivity measurement reports on thermodynamics. Combined with structure prediction, DMS reactivity allowed the development of experimentally accurate 3D models of TLR mutants. These results demonstrate that qMaPseq is broadly accessible, high-throughput and directly links DMS reactivity to thermodynamics.
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Affiliation(s)
- Bret Lange
- Department of Chemistry, University of Nebraska, 639 North 12th St, Lincoln, NE 68588, USA
| | - Ricardo G Gil
- Department of Chemistry, University of Nebraska, 639 North 12th St, Lincoln, NE 68588, USA
| | - Gavin S Anderson
- Department of Chemistry, University of Nebraska, 639 North 12th St, Lincoln, NE 68588, USA
| | - Joseph D Yesselman
- Department of Chemistry, University of Nebraska, 639 North 12th St, Lincoln, NE 68588, USA
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2
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Xiao L, Fang L, Kool ET. Acylation probing of "generic" RNA libraries reveals critical influence of loop constraints on reactivity. Cell Chem Biol 2022; 29:1341-1352.e8. [PMID: 35662395 PMCID: PMC9391288 DOI: 10.1016/j.chembiol.2022.05.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/16/2022] [Accepted: 05/12/2022] [Indexed: 01/08/2023]
Abstract
The reactivity of RNA 2'-OH acylation is broadly useful both in probing structure and in preparing conjugates. To date, this reactivity has been analyzed in limited sets of biological RNA sequences, leaving open questions of how reactivity varies inherently without regard to sequence in structured contexts. We constructed and probed "generic" structured RNA libraries using homogeneous loop sequences, employing deep sequencing to carry out a systematic survey of reactivity. We find a wide range of RNA reactivities among single-stranded sequences, with nearest neighbors playing substantial roles. Remarkably, certain small loops are found to be far more reactive on average (up to 4,000-fold) than single-stranded RNAs, due to conformational constraints that enhance reactivity. Among loops, we observe large variations in reactivity based on size, type, and position. The results lend insights into RNA designs for achieving high-efficiency local conjugation and provide new opportunities to refine structure analysis.
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Affiliation(s)
- Lu Xiao
- Department of Chemistry and ChEM-H Institute, Stanford University, Stanford, CA 94305, USA
| | - Linglan Fang
- Department of Chemistry and ChEM-H Institute, Stanford University, Stanford, CA 94305, USA
| | - Eric T Kool
- Department of Chemistry and ChEM-H Institute, Stanford University, Stanford, CA 94305, USA.
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3
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Halder A, Kumar S, Valsson O, Reddy G. Mg 2+ Sensing by an RNA Fragment: Role of Mg 2+-Coordinated Water Molecules. J Chem Theory Comput 2020; 16:6702-6715. [PMID: 32941038 DOI: 10.1021/acs.jctc.0c00589] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RNA molecules selectively bind to specific metal ions to populate their functional active states, making it important to understand their source of ion selectivity. In large RNA systems, metal ions interact with the RNA at multiple locations, making it difficult to decipher the precise role of ions in folding. To overcome this complexity, we studied the role of different metal ions (Mg2+, Ca2+, and K+) in the folding of a small RNA hairpin motif (5'-ucCAAAga-3') using unbiased all-atom molecular dynamics simulations. The advantage of studying this system is that it requires specific binding of a single metal ion to fold to its native state. We find that even for this small RNA, the folding free energy surface (FES) is multidimensional as different metal ions present in the solution can simultaneously facilitate folding. The FES shows that specific binding of a metal ion is indispensable for its folding. We further show that in addition to the negatively charged phosphate groups, the spatial organization of electronegative nucleobase atoms drives the site-specific binding of the metal ions. Even though the binding site cannot discriminate between different metal ions, RNA folds efficiently only in a Mg2+ solution. We show that the rigid network of Mg2+-coordinated water molecules facilitates the formation of important interactions in the transition state. The other metal ions such as K+ and Ca2+ cannot facilitate the formation of such interactions. These results allow us to hypothesize possible metal-sensing mechanisms in large metalloriboswitches and also provide useful insights into the design of appropriate collective variables for studying large RNA molecules using enhanced sampling methods.
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Affiliation(s)
- Antarip Halder
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, Karnataka, India
| | - Sunil Kumar
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, Karnataka, India
| | - Omar Valsson
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, Karnataka, India
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4
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Mitchell C, Polanco JA, DeWald L, Kress D, Jaeger L, Grabow WW. Responsive self-assembly of tectoRNAs with loop-receptor interactions from the tetrahydrofolate (THF) riboswitch. Nucleic Acids Res 2020; 47:6439-6451. [PMID: 31045210 PMCID: PMC6614920 DOI: 10.1093/nar/gkz304] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 03/22/2019] [Accepted: 04/16/2019] [Indexed: 12/17/2022] Open
Abstract
Naturally occurring RNAs are known to exhibit a high degree of modularity, whereby specific structural modules (or motifs) can be mixed and matched to create new molecular architectures. The modular nature of RNA also affords researchers the ability to characterize individual structural elements in controlled synthetic contexts in order to gain new and critical insights into their particular structural features and overall performance. Here, we characterized the binding affinity of a unique loop–receptor interaction found in the tetrahydrofolate (THF) riboswitch using rationally designed self-assembling tectoRNAs. Our work suggests that the THF loop–receptor interaction has been fine-tuned for its particular role as a riboswitch component. We also demonstrate that the thermodynamic stability of this interaction can be modulated by the presence of folinic acid, which induces a local structural change at the level of the loop–receptor. This corroborates the existence of a THF binding site within this tertiary module and paves the way for its potential use as a THF responsive module for RNA nanotechnology and synthetic biology.
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Affiliation(s)
- Charles Mitchell
- Department of Chemistry and Biochemistry, Seattle Pacific University, Seattle, WA 918119-1997, USA
| | - Julio A Polanco
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
| | - Laura DeWald
- Department of Chemistry and Biochemistry, Seattle Pacific University, Seattle, WA 918119-1997, USA
| | - Dustin Kress
- Department of Chemistry and Biochemistry, Seattle Pacific University, Seattle, WA 918119-1997, USA
| | - Luc Jaeger
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
| | - Wade W Grabow
- Department of Chemistry and Biochemistry, Seattle Pacific University, Seattle, WA 918119-1997, USA
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5
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Calkins ER, Zakrevsky P, Keleshian VL, Aguilar EG, Geary C, Jaeger L. Deducing putative ancestral forms of GNRA/receptor interactions from the ribosome. Nucleic Acids Res 2019; 47:480-494. [PMID: 30418638 PMCID: PMC6326782 DOI: 10.1093/nar/gky1111] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/22/2018] [Indexed: 01/02/2023] Open
Abstract
Stable RNAs rely on a vast repertoire of long-range interactions to assist in the folding of complex cellular machineries such as the ribosome. The universally conserved L39/H89 interaction is a long-range GNRA-like/receptor interaction localized in proximity to the peptidyl transferase center of the large subunit of the ribosome. Because of its central location, L39/H89 likely originated at an early evolutionary stage of the ribosome and played a significant role in its early function. However, L39/H89 self-assembly is impaired outside the ribosomal context. Herein, we demonstrate that structural modularity principles can be used to re-engineer L39/H89 to self-assemble in vitro. The new versions of L39/H89 improve affinity and loop selectivity by several orders of magnitude and retain the structural and functional features of their natural counterparts. These versions of L39/H89 are proposed to be ancestral forms of L39/H89 that were capable of assembling and folding independently from proteins and post-transcriptional modifications. This work demonstrates that novel RNA modules can be rationally designed by taking advantage of the modular syntax of RNA. It offers the prospect of creating new biochemical models of the ancestral ribosome and increases the tool kit for RNA nanotechnology and synthetic biology.
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Affiliation(s)
- Erin R Calkins
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
| | - Paul Zakrevsky
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
| | - Vasken L Keleshian
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
| | - Eduardo G Aguilar
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
| | - Cody Geary
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
| | - Luc Jaeger
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106-9510, USA
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6
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Abstract
The past decades have witnessed tremendous developments in our understanding of RNA biology. At the core of these advances have been studies aimed at discerning RNA structure and at understanding the forces that influence the RNA folding process. It is easy to take the present state of understanding for granted, but there is much to be learned by considering the path to our current understanding, which has been tortuous, with the birth and death of models, the adaptation of experimental tools originally developed for characterization of protein structure and catalysis, and the development of novel tools for probing RNA. In this review we tour the stages of RNA folding studies, considering them as "epochs" that can be generalized across scientific disciplines. These epochs span from the discovery of catalytic RNA, through biophysical insights into the putative primordial RNA World, to characterization of structured RNAs, the building and testing of models, and, finally, to the development of models with the potential to yield generalizable predictive and quantitative models for RNA conformational, thermodynamic, and kinetic behavior. We hope that this accounting will aid others as they navigate the many fascinating questions about RNA and its roles in biology, in the past, present, and future.
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Affiliation(s)
- Daniel Herschlag
- Department of Biochemistry, Stanford University, Stanford, California 94305
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
- Department of Chemistry, Stanford University, Stanford, California 94305
- Stanford ChEM-H (Chemistry, Engineering, and Medicine for Human Health), Stanford, California 94305
| | - Steve Bonilla
- Department of Biochemistry, Stanford University, Stanford, California 94305
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
| | - Namita Bisaria
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
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7
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Bonilla S, Limouse C, Bisaria N, Gebala M, Mabuchi H, Herschlag D. Single-Molecule Fluorescence Reveals Commonalities and Distinctions among Natural and in Vitro-Selected RNA Tertiary Motifs in a Multistep Folding Pathway. J Am Chem Soc 2017; 139:18576-18589. [PMID: 29185740 PMCID: PMC5748328 DOI: 10.1021/jacs.7b08870] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
![]()
Decades
of study of the RNA folding problem have revealed that
diverse and complex structured RNAs are built from a common set of
recurring structural motifs, leading to the perspective that a generalizable
model of RNA folding may be developed from understanding of the folding
properties of individual structural motifs. We used single-molecule
fluorescence to dissect the kinetic and thermodynamic properties of
a set of variants of a common tertiary structural motif, the tetraloop/tetraloop-receptor
(TL/TLR). Our results revealed a multistep TL/TLR folding pathway
in which preorganization of the ubiquitous AA-platform submotif precedes
the formation of the docking transition state and tertiary A-minor
hydrogen bond interactions form after the docking transition state.
Differences in ion dependences between TL/TLR variants indicated the
occurrence of sequence-dependent conformational rearrangements prior
to and after the formation of the docking transition state. Nevertheless,
varying the junction connecting the TL/TLR produced a common kinetic
and ionic effect for all variants, suggesting that the global conformational
search and compaction electrostatics are energetically independent
from the formation of the tertiary motif contacts. We also found that in vitro-selected variants, despite their similar stability
at high Mg2+ concentrations, are considerably less stable
than natural variants under near-physiological ionic conditions, and
the occurrence of the TL/TLR sequence variants in Nature correlates
with their thermodynamic stability in isolation. Overall, our findings
are consistent with modular but complex energetic properties of RNA
structural motifs and will aid in the eventual quantitative description
of RNA folding from its secondary and tertiary structural elements.
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Affiliation(s)
- Steve Bonilla
- Department of Chemical Engineering, ‡Department of Applied Physics, §Department of Biochemistry, ∥Department of Chemistry, ⊥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States
| | - Charles Limouse
- Department of Chemical Engineering, ‡Department of Applied Physics, §Department of Biochemistry, ∥Department of Chemistry, ⊥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States
| | - Namita Bisaria
- Department of Chemical Engineering, ‡Department of Applied Physics, §Department of Biochemistry, ∥Department of Chemistry, ⊥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States
| | - Magdalena Gebala
- Department of Chemical Engineering, ‡Department of Applied Physics, §Department of Biochemistry, ∥Department of Chemistry, ⊥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States
| | - Hideo Mabuchi
- Department of Chemical Engineering, ‡Department of Applied Physics, §Department of Biochemistry, ∥Department of Chemistry, ⊥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States
| | - Daniel Herschlag
- Department of Chemical Engineering, ‡Department of Applied Physics, §Department of Biochemistry, ∥Department of Chemistry, ⊥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States
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8
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LeBlanc RM, Longhini AP, Le Grice SF, Johnson BA, Dayie TK. Combining asymmetric 13C-labeling and isotopic filter/edit NOESY: a novel strategy for rapid and logical RNA resonance assignment. Nucleic Acids Res 2017; 45:e146. [PMID: 28934505 PMCID: PMC5766159 DOI: 10.1093/nar/gkx591] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2015] [Revised: 06/22/2017] [Accepted: 08/04/2017] [Indexed: 01/08/2023] Open
Abstract
Although ∼98% of the human genomic output is transcribed as non-protein coding RNA, <2% of the protein data bank structures comprise RNA. This huge structural disparity stems from combined difficulties of crystallizing RNA for X-ray crystallography along with extensive chemical shift overlap and broadened linewidths associated with NMR of RNA. While half of the deposited RNA structures in the PDB were solved by NMR methods, the usefulness of NMR is still limited by the high cost of sample preparation and challenges of resonance assignment. Here we propose a novel strategy for resonance assignment that combines new strategic 13C labeling technologies with filter/edit type NOESY experiments to greatly reduce spectral complexity and crowding. This new strategy allowed us to assign important non-exchangeable resonances of proton and carbon (1', 2', 2, 5, 6 and 8) nuclei using only one sample and <24 h of NMR instrument time for a 27 nt model RNA. The method was further extended to assigning a 6 nt bulge from a 61 nt viral RNA element justifying its use for a wide range RNA chemical shift resonance assignment problems.
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Affiliation(s)
- Regan M. LeBlanc
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
- Basic Research Laboratory, National Cancer Institute, Frederick, MD 21702, USA
| | - Andrew P. Longhini
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | | | - Bruce A. Johnson
- One Moon Scientific, Inc., Westfield, NJ 07090, USA
- Structural Biology Initiative, Advanced Science Research Center at the Graduate Center of the City University of New York, New York, NY 10031, USA
| | - Theodore K. Dayie
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
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9
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Quantitative tests of a reconstitution model for RNA folding thermodynamics and kinetics. Proc Natl Acad Sci U S A 2017; 114:E7688-E7696. [PMID: 28839094 DOI: 10.1073/pnas.1703507114] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Decades of study of the architecture and function of structured RNAs have led to the perspective that RNA tertiary structure is modular, made of locally stable domains that retain their structure across RNAs. We formalize a hypothesis inspired by this modularity-that RNA folding thermodynamics and kinetics can be quantitatively predicted from separable energetic contributions of the individual components of a complex RNA. This reconstitution hypothesis considers RNA tertiary folding in terms of ΔGalign, the probability of aligning tertiary contact partners, and ΔGtert, the favorable energetic contribution from the formation of tertiary contacts in an aligned state. This hypothesis predicts that changes in the alignment of tertiary contacts from different connecting helices and junctions (ΔGHJH) or from changes in the electrostatic environment (ΔG+/-) will not affect the energetic perturbation from a mutation in a tertiary contact (ΔΔGtert). Consistent with these predictions, single-molecule FRET measurements of folding of model RNAs revealed constant ΔΔGtert values for mutations in a tertiary contact embedded in different structural contexts and under different electrostatic conditions. The kinetic effects of these mutations provide further support for modular behavior of RNA elements and suggest that tertiary mutations may be used to identify rate-limiting steps and dissect folding and assembly pathways for complex RNAs. Overall, our model and results are foundational for a predictive understanding of RNA folding that will allow manipulation of RNA folding thermodynamics and kinetics. Conversely, the approaches herein can identify cases where an independent, additive model cannot be applied and so require additional investigation.
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10
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Aytenfisu A, Spasic A, Grossfield A, Stern HA, Mathews DH. Revised RNA Dihedral Parameters for the Amber Force Field Improve RNA Molecular Dynamics. J Chem Theory Comput 2017; 13:900-915. [PMID: 28048939 PMCID: PMC5312698 DOI: 10.1021/acs.jctc.6b00870] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Indexed: 12/27/2022]
Abstract
The backbone dihedral parameters of the Amber RNA force field were improved by fitting using multiple linear regression to potential energies determined by quantum chemistry calculations. Five backbone and four glycosidic dihedral parameters were fit simultaneously to reproduce the potential energies determined by a high-level density functional theory calculation (B97D3 functional with the AUG-CC-PVTZ basis set). Umbrella sampling was used to determine conformational free energies along the dihedral angles, and these better agree with the population of conformations observed in the protein data bank for the new parameters than for the conventional parameters. Molecular dynamics simulations performed on a set of hairpin loops, duplexes and tetramers with the new parameter set show improved modeling for the structures of tetramers CCCC, CAAU, and GACC, and an RNA internal loop of noncanonical pairs, as compared to the conventional parameters. For the tetramers, the new parameters largely avoid the incorrect intercalated structures that dominate the conformational samples from the conventional parameters. For the internal loop, the major conformation solved by NMR is stable with the new parameters, but not with the conventional parameters. The new force field performs similarly to the conventional parameters for the UUCG and GCAA hairpin loops and the [U(UA)6A]2 duplex.
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Affiliation(s)
- Asaminew
H. Aytenfisu
- Department
of Biochemistry & Biophysics, University
of Rochester Medical Center, Rochester, New York 14642, United States
- Center
for RNA Biology, University of Rochester
Medical Center, Rochester, New York 14642, United States
| | - Aleksandar Spasic
- Department
of Biochemistry & Biophysics, University
of Rochester Medical Center, Rochester, New York 14642, United States
- Center
for RNA Biology, University of Rochester
Medical Center, Rochester, New York 14642, United States
| | - Alan Grossfield
- Department
of Biochemistry & Biophysics, University
of Rochester Medical Center, Rochester, New York 14642, United States
| | - Harry A. Stern
- Center
for Integrated Research Computing, University
of Rochester, Rochester, New York 14642, United
States
| | - David H. Mathews
- Department
of Biochemistry & Biophysics, University
of Rochester Medical Center, Rochester, New York 14642, United States
- Center
for RNA Biology, University of Rochester
Medical Center, Rochester, New York 14642, United States
- Department
of Biostatistics & Computational Biology, University of Rochester Medical Center, Rochester, New York 14642, United States
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11
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Sengupta A, Sung HL, Nesbitt DJ. Amino Acid Specific Effects on RNA Tertiary Interactions: Single-Molecule Kinetic and Thermodynamic Studies. J Phys Chem B 2016; 120:10615-10627. [PMID: 27718572 DOI: 10.1021/acs.jpcb.6b05840] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In light of the current models for an early RNA-based universe, the potential influence of simple amino acids on tertiary folding of ribozymal RNA into biochemically competent structures is speculated to be of significant evolutionary importance. In the present work, the folding-unfolding kinetics of a ubiquitous tertiary interaction motif, the GAAA tetraloop-tetraloop receptor (TL-TLR), is investigated by single-molecule fluorescence resonance energy transfer spectroscopy in the presence of natural amino acids both with (e.g., lysine, arginine) and without (e.g., glycine) protonated side chain residues. By way of control, we also investigate the effects of a special amino acid (e.g., proline) and amino acid mimetic (e.g., betaine) that contain secondary or quaternary amine groups rather than a primary amine group. This combination permits systematic study of amino acid induced (or amino acid like) RNA folding dynamics as a function of side chain complexity, pKa, charge state, and amine group content. Most importantly, each of the naturally occurring amino acids is found to destabilize the TL-TLR tertiary folding equilibrium, the kinetic origin of which is dominated by a decrease in the folding rate constant (kdock), also affected by a strongly amino acid selective increase in the unfolding rate constant (kundock). To further elucidate the underlying thermodynamics, single-molecule equilibrium constants (Keq) for TL-TLR folding have been probed as a function of temperature, which reveal an amino acid dependent decrease in both overall exothermicity (ΔΔH° > 0) and entropic cost (-TΔΔS° < 0) for the overall folding process. Temperature-dependent studies on the folding/unfolding kinetic rate constants reveal analogous amino acid specific changes in both enthalpy (ΔΔH⧧) and entropy (ΔΔS⧧) for accessing the transition state barrier. The maximum destabilization of the TL-TLR tertiary interaction is observed for arginine, which is consistent with early studies of arginine and guanidine ion-inhibited self-splicing kinetics for the full Tetrahymena ribozyme [ Yarus , M. ; Christian , E. L. Nature 1989 , 342 , 349 - 350 ; Yarus , M. Science 1988 , 240 , 1751 - 1758 ].
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Affiliation(s)
- Abhigyan Sengupta
- JILA, National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Hsuan-Lei Sung
- JILA, National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - David J Nesbitt
- JILA, National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
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12
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Bartova S, Alberti E, Sigel RK, Donghi D. Metal ion binding to an RNA internal loop. Inorganica Chim Acta 2016. [DOI: 10.1016/j.ica.2016.02.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Kinetic and thermodynamic framework for P4-P6 RNA reveals tertiary motif modularity and modulation of the folding preferred pathway. Proc Natl Acad Sci U S A 2016; 113:E4956-65. [PMID: 27493222 DOI: 10.1073/pnas.1525082113] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The past decade has seen a wealth of 3D structural information about complex structured RNAs and identification of functional intermediates. Nevertheless, developing a complete and predictive understanding of the folding and function of these RNAs in biology will require connection of individual rate and equilibrium constants to structural changes that occur in individual folding steps and further relating these steps to the properties and behavior of isolated, simplified systems. To accomplish these goals we used the considerable structural knowledge of the folded, unfolded, and intermediate states of P4-P6 RNA. We enumerated structural states and possible folding transitions and determined rate and equilibrium constants for the transitions between these states using single-molecule FRET with a series of mutant P4-P6 variants. Comparisons with simplified constructs containing an isolated tertiary contact suggest that a given tertiary interaction has a stereotyped rate for breaking that may help identify structural transitions within complex RNAs and simplify the prediction of folding kinetics and thermodynamics for structured RNAs from their parts. The preferred folding pathway involves initial formation of the proximal tertiary contact. However, this preference was only ∼10 fold and could be reversed by a single point mutation, indicating that a model akin to a protein-folding contact order model will not suffice to describe RNA folding. Instead, our results suggest a strong analogy with a modified RNA diffusion-collision model in which tertiary elements within preformed secondary structures collide, with the success of these collisions dependent on whether the tertiary elements are in their rare binding-competent conformations.
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14
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Parlea LG, Sweeney BA, Hosseini-Asanjan M, Zirbel CL, Leontis NB. The RNA 3D Motif Atlas: Computational methods for extraction, organization and evaluation of RNA motifs. Methods 2016; 103:99-119. [PMID: 27125735 DOI: 10.1016/j.ymeth.2016.04.025] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 04/21/2016] [Accepted: 04/22/2016] [Indexed: 11/30/2022] Open
Abstract
RNA 3D motifs occupy places in structured RNA molecules that correspond to the hairpin, internal and multi-helix junction "loops" of their secondary structure representations. As many as 40% of the nucleotides of an RNA molecule can belong to these structural elements, which are distinct from the regular double helical regions formed by contiguous AU, GC, and GU Watson-Crick basepairs. With the large number of atomic- or near atomic-resolution 3D structures appearing in a steady stream in the PDB/NDB structure databases, the automated identification, extraction, comparison, clustering and visualization of these structural elements presents an opportunity to enhance RNA science. Three broad applications are: (1) identification of modular, autonomous structural units for RNA nanotechnology, nanobiology and synthetic biology applications; (2) bioinformatic analysis to improve RNA 3D structure prediction from sequence; and (3) creation of searchable databases for exploring the binding specificities, structural flexibility, and dynamics of these RNA elements. In this contribution, we review methods developed for computational extraction of hairpin and internal loop motifs from a non-redundant set of high-quality RNA 3D structures. We provide a statistical summary of the extracted hairpin and internal loop motifs in the most recent version of the RNA 3D Motif Atlas. We also explore the reliability and accuracy of the extraction process by examining its performance in clustering recurrent motifs from homologous ribosomal RNA (rRNA) structures. We conclude with a summary of remaining challenges, especially with regard to extraction of multi-helix junction motifs.
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Affiliation(s)
- Lorena G Parlea
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
| | - Blake A Sweeney
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
| | | | - Craig L Zirbel
- Department of Mathematics and Statistics, Bowling Green State University, Bowling Green, OH 43403, USA.
| | - Neocles B Leontis
- Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA.
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15
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Herschlag D, Allred BE, Gowrishankar S. From static to dynamic: the need for structural ensembles and a predictive model of RNA folding and function. Curr Opin Struct Biol 2015; 30:125-133. [PMID: 25744941 DOI: 10.1016/j.sbi.2015.02.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 02/11/2015] [Accepted: 02/11/2015] [Indexed: 12/18/2022]
Abstract
To understand RNA, it is necessary to move beyond a descriptive categorization towards quantitative predictions of its molecular conformations and functional behavior. An incisive approach to understanding the function and folding of biological RNA systems involves characterizing small, simple components that are largely responsible for the behavior of complex systems including helix-junction-helix elements and tertiary motifs. State-of-the-art methods have permitted unprecedented insight into the conformational ensembles of these elements revealing, for example, that conformations of helix-junction-helix elements are confined to a small region of the ensemble, that this region is highly dependent on the junction's topology, and that the correct alignment of tertiary motifs may be a rare conformation on the overall folding landscape. Further characterization of RNA components and continued development of experimental and computational methods with the goal of quantitatively predicting RNA folding and functional behavior will be critical to understanding biological RNA systems.
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Affiliation(s)
- Daniel Herschlag
- Department of Biochemistry, Beckman Center, B400, 279 W. Campus Dr. MC: 5307, Stanford University, Stanford, CA 94305, USA; Department of Chemistry, 333 Campus Drive, Mudd Building, Room 121, Stanford University, Stanford, CA 94305, USA; Department of Chemical Engineering, 443 Via Ortega, Room 129, Stanford University, Stanford, CA 94305, USA.
| | - Benjamin E Allred
- Department of Biochemistry, Beckman Center, B400, 279 W. Campus Dr. MC: 5307, Stanford University, Stanford, CA 94305, USA
| | - Seshadri Gowrishankar
- Department of Chemical Engineering, 443 Via Ortega, Room 129, Stanford University, Stanford, CA 94305, USA
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16
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Chirayil S, Wu Q, Amezcua C, Luebke KJ. NMR characterization of an oligonucleotide model of the miR-21 pre-element. PLoS One 2014; 9:e108231. [PMID: 25250627 PMCID: PMC4177108 DOI: 10.1371/journal.pone.0108231] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 08/25/2014] [Indexed: 01/04/2023] Open
Abstract
We have used NMR spectroscopy to characterize an oligonucleotide stem loop structure based on the pre-element of an oncogenic microRNA, miR-21. This predicted stem-loop structure is cleaved from the precursor of miR-21 (pre-miR-21) by the nuclease Dicer. It is also a critical feature recognized by the protein complex that converts the primary transcript (pri-miR-21) into the pre-miRNA. The secondary structure of the native sequence is poorly defined by NMR due to rapid exchange of imino protons with solvent; however, replacement of two adjacent putative G•U base pairs with G•C base pairs retains the conformation of the hairpin observed by chemical probing and stabilizes it sufficiently to observe most of the imino proton resonances of the molecule. The observed resonances are consistent with the predicted secondary structure. In addition, a peak due to a loop uridine suggests an interaction between it and a bulged uridine in the stem. Assignment of non-exchangeable proton resonances and characterization of NOEs and coupling constants allows inference of the following features of the structure: extrahelicity of a bulged adenosine, deviation from A-form geometry in a base-paired stem, and consecutive stacking of the adenosines in the 5′ side of the loop, the guanosine of the closing base pair, and a cross-strand adenosine. Modeling of the structure by restrained molecular dynamics suggests a basis for the interaction between the loop uridine, the bulged uridine in the stem, and an A•U base pair in the stem.
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Affiliation(s)
- Sara Chirayil
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Qiong Wu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Carlos Amezcua
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Structural Elucidation Group, Medical Products Division, Baxter Healthcare, Round Lake, Illinois, United States of America
| | - Kevin J. Luebke
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
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17
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Abstract
RNA dynamics play a fundamental role in many cellular functions. However, there is no general framework to describe these complex processes, which typically consist of many structural maneuvers that occur over timescales ranging from picoseconds to seconds. Here, we classify RNA dynamics into distinct modes representing transitions between basins on a hierarchical free-energy landscape. These transitions include large-scale secondary-structural transitions at >0.1-s timescales, base-pair/tertiary dynamics at microsecond-to-millisecond timescales, stacking dynamics at timescales ranging from nanoseconds to microseconds, and other "jittering" motions at timescales ranging from picoseconds to nanoseconds. We review various modes within these three different tiers, the different mechanisms by which they are used to regulate function, and how they can be coupled together to achieve greater functional complexity.
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18
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He Z, Zhu Y, Chen SJ. Exploring the electrostatic energy landscape for tetraloop-receptor docking. Phys Chem Chem Phys 2013; 16:6367-75. [PMID: 24322001 DOI: 10.1039/c3cp53655f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
It has long been appreciated that Mg(2+) is essential for the stabilization of RNA tertiary structure. However, the problem of quantitative prediction for the ion effect in tertiary structure folding remains. By using the virtual bond RNA folding model (Vfold) to generate RNA conformations and the newly improved tightly bound ion model (TBI) to treat ion-RNA interactions, we investigate Mg(2+)-facilitated tetraloop-receptor docking. For the specific construct of the tetraloop-receptor system, the theoretical analysis shows that the Mg(2+)-induced stabilizing force for the docked state is predominantly entropic and the major contribution comes from the entropy of the diffusive ions. Furthermore, our results show that Mg(2+) ions promote tetraloop-receptor docking mainly through the entropy of the diffusive ions. The theoretical prediction agrees with experimental analysis. The method developed in this paper, which combines the theory for the (Mg(2+)) ion effects in RNA folding and RNA conformational sampling, may provide a useful framework for studying the ion effect in the folding of more complex RNA structures.
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Affiliation(s)
- Zhaojian He
- Department of Physics and Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA.
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19
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Abstract
Nearly two decades after Westhof and Michel first proposed that RNA tetraloops may interact with distal helices, tetraloop–receptor interactions have been recognized as ubiquitous elements of RNA tertiary structure. The unique architecture of GNRA tetraloops (N=any nucleotide, R=purine) enables interaction with a variety of receptors, e.g., helical minor grooves and asymmetric internal loops. The most common example of the latter is the GAAA tetraloop–11 nt tetraloop receptor motif. Biophysical characterization of this motif provided evidence for the modularity of RNA structure, with applications spanning improved crystallization methods to RNA tectonics. In this review, we identify and compare types of GNRA tetraloop–receptor interactions. Then we explore the abundance of structural, kinetic, and thermodynamic information on the frequently occurring and most widely studied GAAA tetraloop–11 nt receptor motif. Studies of this interaction have revealed powerful paradigms for structural assembly of RNA, as well as providing new insights into the roles of cations, transition states and protein chaperones in RNA folding pathways. However, further research will clearly be necessary to characterize other tetraloop–receptor and long-range tertiary binding interactions in detail – an important milestone in the quantitative prediction of free energy landscapes for RNA folding.
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20
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Ishikawa J, Furuta H, Ikawa Y. An in vitro-selected RNA receptor for the GAAC loop: modular receptor for non-GNRA-type tetraloop. Nucleic Acids Res 2013; 41:3748-59. [PMID: 23382175 PMCID: PMC3616724 DOI: 10.1093/nar/gkt040] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Although artificial RNA motifs that can functionally replace the GNRA/receptor interaction, a class of RNA-RNA interacting motifs, were isolated from RNA libraries and used to generate designer RNA structures, receptors for non-GNRA tetraloops have not been found in nature or selected from RNA libraries. In this study, we report successful isolation of a receptor motif interacting with GAAC, a non-GNRA tetraloop, from randomized sequences embedded in a catalytic RNA. Biochemical characterization of the GAAC/receptor interacting motif within three structural contexts showed its binding affinity, selectivity and structural autonomy. The motif has binding affinity comparable with that of a GNRA/receptor, selectivity orthogonal to GNRA/receptors and structural autonomy even in a large RNA context. These features would be advantageous for usage of the motif as a building block for designer RNAs. The isolated motif can also be used as a query sequence to search for unidentified naturally occurring GANC receptor motifs.
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Affiliation(s)
- Junya Ishikawa
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka 819-0395, Japan
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21
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Hsiao C, Lenz TK, Peters JK, Fang PY, Schneider DM, Anderson EJ, Preeprem T, Bowman JC, O'Neill EB, Lie L, Athavale SS, Gossett JJ, Trippe C, Murray J, Petrov AS, Wartell RM, Harvey SC, Hud NV, Williams LD. Molecular paleontology: a biochemical model of the ancestral ribosome. Nucleic Acids Res 2013; 41:3373-85. [PMID: 23355613 PMCID: PMC3597689 DOI: 10.1093/nar/gkt023] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ancient components of the ribosome, inferred from a consensus of previous work, were constructed in silico, in vitro and in vivo. The resulting model of the ancestral ribosome presented here incorporates ∼20% of the extant 23S rRNA and fragments of five ribosomal proteins. We test hypotheses that ancestral rRNA can: (i) assume canonical 23S rRNA-like secondary structure, (ii) assume canonical tertiary structure and (iii) form native complexes with ribosomal protein fragments. Footprinting experiments support formation of predicted secondary and tertiary structure. Gel shift, spectroscopic and yeast three-hybrid assays show specific interactions between ancestral rRNA and ribosomal protein fragments, independent of other, more recent, components of the ribosome. This robustness suggests that the catalytic core of the ribosome is an ancient construct that has survived billions of years of evolution without major changes in structure. Collectively, the data here support a model in which ancestors of the large and small subunits originated and evolved independently of each other, with autonomous functionalities.
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Affiliation(s)
- Chiaolong Hsiao
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA
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22
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Donghi D, Pechlaner M, Finazzo C, Knobloch B, Sigel RKO. The structural stabilization of the κ three-way junction by Mg(II) represents the first step in the folding of a group II intron. Nucleic Acids Res 2012; 41:2489-504. [PMID: 23275550 PMCID: PMC3575829 DOI: 10.1093/nar/gks1179] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Folding of group II introns is characterized by a first slow compaction of domain 1 (D1) followed by the rapid docking of other domains to this scaffold. D1 compaction initiates in a small subregion encompassing the κ and ζ elements. These two tertiary elements are also the major interaction sites with domain 5 to form the catalytic core. Here, we provide the first characterization of the structure adopted at an early folding step and show that the folding control element can be narrowed down to the three-way junction with the κ motif. In our nuclear magnetic resonance studies of this substructure derived from the yeast mitochondrial group II intron Sc.ai5γ, we show that a high affinity Mg(II) ion stabilizes the κ element and enables coaxial stacking between helices d′ and d′′, favoring a rigid duplex across the three-way junction. The κ-element folds into a stable GAAA-tetraloop motif and engages in A-minor interactions with helix d′. The addition of cobalt(III)hexammine reveals three distinct binding sites. The Mg(II)-promoted structural rearrangement and rigidification of the D1 core can be identified as the first micro-step of D1 folding.
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Affiliation(s)
- Daniela Donghi
- Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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23
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Lambert D, Draper DE. Denaturation of RNA secondary and tertiary structure by urea: simple unfolded state models and free energy parameters account for measured m-values. Biochemistry 2012; 51:9014-26. [PMID: 23088364 PMCID: PMC3505219 DOI: 10.1021/bi301103j] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
To investigate the mechanism by which urea destabilizes RNA structure, urea-induced unfolding of four different RNA secondary and tertiary structures was quantified in terms of an m-value, the rate at which the free energy of unfolding changes with urea molality. From literature data and our osmometric study of a backbone analogue, we derived average interaction potentials (per square angstrom of solvent accessible surface) between urea and three kinds of RNA surfaces: phosphate, ribose, and base. Estimates of the increases in solvent accessible surface areas upon RNA denaturation were based on a simple model of unfolded RNA as a combination of helical and single-strand segments. These estimates, combined with the three interaction potentials and a term to account for interactions of urea with released ions, yield calculated m-values that are in good agreement with experimental values (200 mm monovalent salt). Agreement was obtained only if single-stranded RNAs were modeled in a highly stacked, A-form conformation. The primary driving force for urea-induced denaturation is the strong interaction of urea with the large surface areas of bases that become exposed upon denaturation of either RNA secondary or tertiary structure, though interactions of urea with backbone and released ions may account for up to a third of the m-value. Urea m-values for all four RNAs are salt-dependent, which we attribute to an increased extension (or decreased charge density) of unfolded RNAs with an increased urea concentration. The sensitivity of the urea m-value to base surface exposure makes it a potentially useful probe of the conformations of RNA unfolded states.
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Affiliation(s)
| | - David E. Draper
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218
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24
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The role of counterion valence and size in GAAA tetraloop-receptor docking/undocking kinetics. J Mol Biol 2012; 423:198-216. [PMID: 22796627 DOI: 10.1016/j.jmb.2012.07.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 07/02/2012] [Accepted: 07/03/2012] [Indexed: 01/29/2023]
Abstract
For RNA to fold into compact, ordered structures, it must overcome electrostatic repulsion between negatively charged phosphate groups by counterion recruitment. A physical understanding of the counterion-assisted folding process requires addressing how cations kinetically and thermodynamically control the folding equilibrium for each tertiary interaction in a full-length RNA. In this work, single-molecule FRET (fluorescence resonance energy transfer) techniques are exploited to isolate and explore the cation-concentration-dependent kinetics for formation of a ubiquitous RNA tertiary interaction, that is, the docking/undocking of a GAAA tetraloop with its 11-nt receptor. Rate constants for docking (k(dock)) and undocking (k(undock)) are obtained as a function of cation concentration, size, and valence, specifically for the series Na(+), K(+), Mg(2+), Ca(2+), Co(NH(3))(6)(3+), and spermidine(3+). Increasing cation concentration acceleratesk(dock)dramatically but achieves only a slight decrease in k(undock). These results can be kinetically modeled using parallel cation-dependent and cation-independent docking pathways, which allows for isolation of the folding kinetics from the interaction energetics of the cations with the undocked and docked states, respectively. This analysis reveals a preferential interaction of the cations with the transition state and docked state as compared to the undocked RNA, with the ion-RNA interaction strength growing with cation valence. However, the corresponding number of cations that are taken up by the RNA upon folding decreases with charge density of the cation. The only exception to these behaviors is spermidine(3+), whose weaker influence on the docking equilibria with respect to Co(NH(3))(6)(3+) can be ascribed to steric effects preventing complete neutralization of the RNA phosphate groups.
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25
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Koculi E, Cho SS, Desai R, Thirumalai D, Woodson SA. Folding path of P5abc RNA involves direct coupling of secondary and tertiary structures. Nucleic Acids Res 2012; 40:8011-20. [PMID: 22641849 PMCID: PMC3439887 DOI: 10.1093/nar/gks468] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Folding mechanisms in which secondary structures are stabilized through the formation of tertiary interactions are well documented in protein folding but challenge the folding hierarchy normally assumed for RNA. However, it is increasingly clear that RNA could fold by a similar mechanism. P5abc, a small independently folding tertiary domain of the Tetrahymena thermophila group I ribozyme, is known to fold by a secondary structure rearrangement involving helix P5c. However, the extent of this rearrangement and the precise stage of folding that triggers it are unknown. We use experiments and simulations to show that the P5c helix switches to the native secondary structure late in the folding pathway and is directly coupled to the formation of tertiary interactions in the A-rich bulge. P5c mutations show that the switch in P5c is not rate-determining and suggest that non-native interactions in P5c aid folding rather than impede it. Our study illustrates that despite significant differences in the building blocks of proteins and RNA, there may be common ways in which they self-assemble.
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Affiliation(s)
- Eda Koculi
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
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26
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Holmstrom ED, Fiore JL, Nesbitt DJ. Thermodynamic origins of monovalent facilitated RNA folding. Biochemistry 2012; 51:3732-43. [PMID: 22448852 DOI: 10.1021/bi201420a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cations have long been associated with formation of native RNA structure and are commonly thought to stabilize the formation of tertiary contacts by favorably interacting with the electrostatic potential of the RNA, giving rise to an "ion atmosphere". A significant amount of information regarding the thermodynamics of structural transitions in the presence of an ion atmosphere has accumulated and suggests stabilization is dominated by entropic terms. This work provides an analysis of how RNA-cation interactions affect the entropy and enthalpy associated with an RNA tertiary transition. Specifically, temperature-dependent single-molecule fluorescence resonance energy transfer studies have been exploited to determine the free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) of folding for an isolated tetraloop-receptor tertiary interaction as a function of Na(+) concentration. Somewhat unexpectedly, increasing the Na(+) concentration changes the folding enthalpy from a strongly exothermic process [e.g., ΔH° = -26(2) kcal/mol at 180 mM] to a weakly exothermic process [e.g., ΔH° = -4(1) kcal/mol at 630 mM]. As a direct corollary, it is the strong increase in folding entropy [Δ(ΔS°) > 0] that compensates for this loss of exothermicity for the achievement of more favorable folding [Δ(ΔG°) < 0] at higher Na(+) concentrations. In conjunction with corresponding measurements of the thermodynamics of the transition state barrier, these data provide a detailed description of the folding pathway associated with the GAAA tetraloop-receptor interaction as a function of Na(+) concentration. The results support a potentially universal mechanism for monovalent facilitated RNA folding, whereby an increasing monovalent concentration stabilizes tertiary structure by reducing the entropic penalty for folding.
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Affiliation(s)
- Erik D Holmstrom
- JILA, University of Colorado and National Institute of Standards and Technology, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0440, USA
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27
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Abstract
Mg(2+) is essential for the proper folding and function of RNA, though the effect of Mg(2+) concentration on the free energy, enthalpy, and entropy landscapes of RNA folding is unknown. This work exploits temperature-controlled single-molecule FRET methods to address the thermodynamics of RNA folding pathways by probing the intramolecular docking/undocking kinetics of the ubiquitous GAAA tetraloop-receptor tertiary interaction as a function of [Mg(2+)]. These measurements yield the barrier and standard state enthalpies, entropies, and free energies for an RNA tertiary transition, in particular, revealing the thermodynamic origin of [Mg(2+)]-facilitated folding. Surprisingly, these studies reveal that increasing [Mg(2+)] promotes tetraloop-receptor interaction by reducing the entropic barrier (-TΔS(++)(dock)) and the overall entropic penalty (-TΔS(+) (dock)) for docking, with essentially negligible effects on both the activation enthalpy (ΔH(++)(dock)) and overall exothermicity (ΔH(+)(dock)). These observations contrast with the conventional notion that increasing [Mg(2+)] facilitates folding by minimizing electrostatic repulsion of opposing RNA helices, which would incorrectly predict a decrease in ΔH(++)(dock)) and ΔH(+)(dock)) with [Mg(2+)]. Instead we propose that higher [Mg(2+)] can aid RNA folding by decreasing the entropic penalty of counterion uptake and by reducing disorder of the unfolded conformational ensemble.
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28
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Fujita Y, Tanaka T, Furuta H, Ikawa Y. Functional roles of a tetraloop/receptor interacting module in a cyclic di-GMP riboswitch. J Biosci Bioeng 2011; 113:141-5. [PMID: 22074990 DOI: 10.1016/j.jbiosc.2011.10.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 09/26/2011] [Accepted: 10/07/2011] [Indexed: 12/27/2022]
Abstract
Riboswitches are a class of structural RNAs that regulate transcription and translation through specific recognition of small molecules. Riboswitches are attractive not only as drug targets for novel antibiotics but also as modular tools for controlling gene expression. Sequence comparison of a class of riboswitches that sense cyclic di-GMP (type-I c-di-GMP riboswitches) revealed that this type of riboswitch frequently shows a GAAA loop/receptor interaction between P1 and P3 elements. In the crystal structures of a type-I c-di-GMP riboswitch from Vibrio cholerae (the Vc2 riboswitch), the GNRA loop/receptor interaction assembled P2 and P3 stems to organize a ligand-binding pocket. In this study, the functional importance of the GAAA loop-receptor interaction in the Vc2 riboswitch was examined. A series of variant Vc2 riboswitches with mutations in the GAAA loop/receptor interaction were assayed for their switching abilities. In mutants with mutations in the P2 GAAA loop, expression of the reporter gene was reduced to approximately 40% - 60% of that in the wild-type. However, mutants in which the P3 receptor motif was substituted with base pairs were as active as the wild-type. These results suggested that the GAAA loop/receptor interaction does not simply establish the RNA 3D structure but docking of P2 GAAA loop reduces the flexibility of the GAAA receptor motif in the P3 element. This mechanism was supported by a variant riboswitch bearing a theophylline aptamer module in P3 the structural rigidity of which could be modulated by the small molecule theophylline.
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Affiliation(s)
- Yuki Fujita
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395, Japan
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29
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Mustoe AM, Bailor MH, Teixeira RM, Brooks CL, Al-Hashimi HM. New insights into the fundamental role of topological constraints as a determinant of two-way junction conformation. Nucleic Acids Res 2011; 40:892-904. [PMID: 21937512 PMCID: PMC3258142 DOI: 10.1093/nar/gkr751] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Recent studies have shown that topological constraints encoded at the RNA secondary structure level involving basic steric and stereochemical forces can significantly restrict the orientations sampled by helices across two-way RNA junctions. Here, we formulate these topological constraints in greater quantitative detail and use this topological framework to rationalize long-standing but poorly understood observations regarding the basic behavior of RNA two-way junctions. Notably, we show that the asymmetric nature of the A-form helix and the finite length of a bulge provide a physical basis for the experimentally observed directionality and bulge-length amplitude dependence of bulge induced inter-helical bends. We also find that the topologically allowed space can be modulated by variations in sequence, particularly with the addition of non-canonical GU base pairs at the junction, and, surprisingly, by the length of the 5′ and 3′ helices. A survey of two-way RNA junctions in the protein data bank confirms that junction residues have a strong preference to adopt looped-in, non-canonically base-paired conformations, providing a route for extending our bulge-directed framework to internal loop motifs and implying a simplified link between secondary and tertiary structure. Finally, our results uncover a new simple mechanism for coupling junction-induced topological constraints with tertiary interactions.
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Affiliation(s)
- Anthony M Mustoe
- Departments of Chemistry & Biophysics, The University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109-1055, USA
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30
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Ishikawa J, Fujita Y, Maeda Y, Furuta H, Ikawa Y. GNRA/receptor interacting modules: Versatile modular units for natural and artificial RNA architectures. Methods 2011; 54:226-38. [DOI: 10.1016/j.ymeth.2010.12.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 12/08/2010] [Accepted: 12/08/2010] [Indexed: 12/25/2022] Open
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31
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Schellenberg MJ, Dul EL, MacMillan AM. Structural model of the p14/SF3b155 · branch duplex complex. RNA (NEW YORK, N.Y.) 2011; 17:155-65. [PMID: 21062891 PMCID: PMC3004057 DOI: 10.1261/rna.2224411] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 10/01/2010] [Indexed: 05/30/2023]
Abstract
Human p14 (SF3b14), a component of the spliceosomal U2 snRNP, interacts directly with the pre-mRNA branch adenosine within the context of the bulged duplex formed between the pre-mRNA branch region and U2 snRNA. This association occurs early in spliceosome assembly and persists within the fully assembled spliceosome. Analysis of the crystal structure of a complex containing p14 and a peptide derived from p14-associated SF3b155 combined with the results of cross-linking studies has suggested that the branch nucleotide interacts with a pocket on a non-canonical RNA binding surface formed by the complex. Here we report a structural model of the p14 · bulged duplex interaction based on a combination of X-ray crystallography of an adenine p14/SF3b155 peptide complex, biochemical comparison of a panel of disulfide cross-linked protein-RNA complexes, and small-angle X-ray scattering (SAXS). These studies reveal specific recognition of the branch adenosine within the p14 pocket and establish the orientation of the bulged duplex RNA bound on the protein surface. The intimate association of one surface of the bulged duplex with the p14/SF3b155 peptide complex described by this model buries the branch nucleotide at the interface and suggests that p14 · duplex interaction must be disrupted before the first step of splicing.
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Affiliation(s)
- Matthew J Schellenberg
- Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta, Canada
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32
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Fiore JL, Kraemer B, Koberling F, Edmann R, Nesbitt DJ. Enthalpy-driven RNA folding: single-molecule thermodynamics of tetraloop-receptor tertiary interaction. Biochemistry 2010; 48:2550-8. [PMID: 19186984 DOI: 10.1021/bi8019788] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
RNA folding thermodynamics are crucial for structure prediction, which requires characterization of both enthalpic and entropic contributions of tertiary motifs to conformational stability. We explore the temperature dependence of RNA folding due to the ubiquitous GAAA tetraloop-receptor docking interaction, exploiting immobilized and freely diffusing single-molecule fluorescence resonance energy transfer (smFRET) methods. The equilibrium constant for intramolecular docking is obtained as a function of temperature (T = 21-47 degrees C), from which a van't Hoff analysis yields the enthalpy (DeltaH degrees) and entropy (DeltaS degrees) of docking. Tetraloop-receptor docking is significantly exothermic and entropically unfavorable in 1 mM MgCl(2) and 100 mM NaCl, with excellent agreement between immobilized (DeltaH degrees = -17.4 +/- 1.6 kcal/mol, and DeltaS degrees = -56.2 +/- 5.4 cal mol(-1) K(-1)) and freely diffusing (DeltaH degrees = -17.2 +/- 1.6 kcal/mol, and DeltaS degrees = -55.9 +/- 5.2 cal mol(-1) K(-1)) species. Kinetic heterogeneity in the tetraloop-receptor construct is unaffected over the temperature range investigated, indicating a large energy barrier for interconversion between the actively docking and nondocking subpopulations. Formation of the tetraloop-receptor interaction can account for approximately 60% of the DeltaH degrees and DeltaS degrees of P4-P6 domain folding in the Tetrahymena ribozyme, suggesting that it may act as a thermodynamic clamp for the domain. Comparison of the isolated tetraloop-receptor and other tertiary folding thermodynamics supports a theme that enthalpy- versus entropy-driven folding is determined by the number of hydrogen bonding and base stacking interactions.
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Affiliation(s)
- Julie L Fiore
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440, USA
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33
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Zuo X, Wang J, Yu P, Eyler D, Xu H, Starich MR, Tiede DM, Simon AE, Kasprzak W, Schwieters CD, Shapiro BA, Wang YX. Solution structure of the cap-independent translational enhancer and ribosome-binding element in the 3' UTR of turnip crinkle virus. Proc Natl Acad Sci U S A 2010; 107:1385-90. [PMID: 20080629 PMCID: PMC2803139 DOI: 10.1073/pnas.0908140107] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The 3(') untranslated region (3(') UTR) of turnip crinkle virus (TCV) genomic RNA contains a cap-independent translation element (CITE), which includes a ribosome-binding structural element (RBSE) that participates in recruitment of the large ribosomal subunit. In addition, a large symmetric loop in the RBSE plays a key role in coordinating the incompatible processes of viral translation and replication, which require enzyme progression in opposite directions on the viral template. To understand the structural basis for the large ribosomal subunit recruitment and the intricate interplay among different parts of the molecule, we determined the global structure of the 102-nt RBSE RNA using solution NMR and small-angle x-ray scattering. This RNA has many structural features that resemble those of a tRNA in solution. The hairpins H1 and H2, linked by a 7-nucleotide linker, form the upper part of RBSE and hairpin H3 is relatively independent from the rest of the structure and is accessible to interactions. This global structure provides insights into the three-dimensional layout for ribosome binding, which may serve as a structural basis for its involvement in recruitment of the large ribosomal subunit and the switch between viral translation and replication. The experimentally determined three-dimensional structure of a functional element in the 3(') UTR of an RNA from any organism has not been previously reported. The RBSE structure represents a prototype structure of a new class of RNA structural elements involved in viral translation/replication processes.
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Affiliation(s)
- Xiaobing Zuo
- Protein Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702
| | - Jinbu Wang
- Protein Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702
| | - Ping Yu
- Protein Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702
- Basic Science Program, SAIC-Frederick, Inc., National Cancer Institute at Frederick, Frederick, MD 21702
| | - Dan Eyler
- Department of Molecular Biology and Genetics, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Huan Xu
- Protein Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702
| | - Mary R. Starich
- Office of Chief, Structural Biophysics Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702
| | - David M. Tiede
- The Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439
| | - Anne E. Simon
- Department of Cell Biology and Molecular Genetics, University of Maryland College Park, College Park, MD 20742
| | - Wojciech Kasprzak
- Basic Science Program, SAIC-Frederick, Inc., National Cancer Institute at Frederick, Frederick, MD 21702
| | - Charles D. Schwieters
- Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892
| | - Bruce A. Shapiro
- Center for Cancer Research, Nanobiology Program, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702
| | - Yun-Xing Wang
- Protein Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702
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34
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Frederiksen JK, Piccirilli JA. Identification of catalytic metal ion ligands in ribozymes. Methods 2009; 49:148-66. [PMID: 19651216 DOI: 10.1016/j.ymeth.2009.07.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2009] [Revised: 07/20/2009] [Accepted: 07/29/2009] [Indexed: 01/05/2023] Open
Abstract
Site-bound metal ions participate in the catalytic mechanisms of many ribozymes. Understanding these mechanisms therefore requires knowledge of the specific ligands on both substrate and ribozyme that coordinate these catalytic metal ions. A number of different structural and biochemical strategies have been developed and refined for identifying metal ion binding sites within ribozymes, and for assessing the catalytic contributions of the metal ions bound at those sites. We review these approaches and provide examples of their application, focusing in particular on metal ion rescue experiments and their roles in the construction of the transition state models for the Tetrahymena group I and RNase P ribozymes.
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Affiliation(s)
- John K Frederiksen
- The Pritzker School of Medicine, The University of Chicago, Chicago, IL 60637, USA
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35
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Lambert D, Leipply D, Shiman R, Draper DE. The influence of monovalent cation size on the stability of RNA tertiary structures. J Mol Biol 2009; 390:791-804. [PMID: 19427322 PMCID: PMC2712228 DOI: 10.1016/j.jmb.2009.04.083] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2009] [Revised: 04/29/2009] [Accepted: 04/30/2009] [Indexed: 01/03/2023]
Abstract
Many RNA tertiary structures are stable in the presence of monovalent ions alone. To evaluate the degree to which ions at or near the surfaces of such RNAs contribute to stability, the salt-dependent stability of a variety of RNA structures was measured with each of the five group I cations. The stability of hairpin secondary structures and a pseudoknot tertiary structure are insensitive to the ion identity, but the tertiary structures of two other RNAs, an adenine riboswitch and a kissing loop complex, become more stable by 2-3 kcal/mol as ion size decreases. This "default" trend is attributed to the ability of smaller ions to approach the RNA surface more closely. The degree of cation accumulation around the kissing loop complex was also inversely proportional to ion radius, perhaps because of the presence of sterically restricted pockets that can be accessed only by smaller ions. An RNA containing the tetraloop-receptor motif shows a strong (up to approximately 3 kcal/mol) preference for Na(+) or K(+) over other group I ions, consistent with the chelation of K(+) by this motif in some crystal structures. This RNA reverts to the default dependence on ion size when a base forming part of the chelation site is mutated. Lastly, an RNA aptamer for cobinamide, which was originally selected in the presence of high concentrations of LiCl, binds ligand more strongly in the presence of Li(+) than other monovalent ions. On the basis of these trends in RNA stability with group I ion size, it is argued that two features of RNA tertiary structures may promote strong interactions with ions at or near the RNA surface: negative charge densities that are higher than that in secondary structures, and the occasional presence of chelation sites, which are electronegative pockets that selectively bind ions of an optimum size.
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Affiliation(s)
- Dominic Lambert
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
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36
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Zhang Y, Zhao X, Mu Y. Conformational Transition Map of an RNA GCAA Tetraloop Explored by Replica-Exchange Molecular Dynamics Simulation. J Chem Theory Comput 2009; 5:1146-54. [DOI: 10.1021/ct8004276] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yufen Zhang
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, and State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, P.R. China
| | - Xian Zhao
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, and State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, P.R. China
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, and State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, P.R. China
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37
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Xia T. Taking femtosecond snapshots of RNA conformational dynamics and complexity. Curr Opin Chem Biol 2008; 12:604-11. [DOI: 10.1016/j.cbpa.2008.08.033] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Revised: 08/12/2008] [Accepted: 08/23/2008] [Indexed: 12/25/2022]
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38
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Reifur L, Koslowsky DJ. Trypanosoma brucei ATPase subunit 6 mRNA bound to gA6-14 forms a conserved three-helical structure. RNA (NEW YORK, N.Y.) 2008; 14:2195-211. [PMID: 18772247 PMCID: PMC2553734 DOI: 10.1261/rna.1144508] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Accepted: 07/17/2008] [Indexed: 05/26/2023]
Abstract
T. brucei survival relies on the expression of mitochondrial genes, most of which require RNA editing to become translatable. In trypanosomes, RNA editing involves the insertion and deletion of uridylates, a developmentally regulated process directed by guide RNAs (gRNAs) and catalyzed by the editosome, a complex of proteins. The pathway for mRNA/gRNA complex formation and assembly with the editosome is still unknown. Work from our laboratory has suggested that distinct mRNA/gRNA complexes anneal to form a conserved core structure that may be important for editosome assembly. The secondary structure for the apocytochrome b (CYb) pair has been previously determined and is consistent with our model of a three-helical structure. Here, we used cross-linking and solution structure probing experiments to determine the structure of the ATPase subunit 6 (A6) mRNA hybridized to its cognate gA6-14 gRNA in different stages of editing. Our results indicate that both unedited and partially edited A6/gA6-14 pairs fold into a three-helical structure similar to the previously characterized CYb/gCYb-558 pair. These results lead us to conclude that at least two mRNA/gRNA pairs with distinct editing sites and distinct primary sequences fold to a three-helical secondary configuration that persists through the first few editing events.
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Affiliation(s)
- Larissa Reifur
- Comparative Medicine and Integrative Biology, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824, USA
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39
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Vander Meulen KA, Davis JH, Foster TR, Record MT, Butcher SE. Thermodynamics and folding pathway of tetraloop receptor-mediated RNA helical packing. J Mol Biol 2008; 384:702-17. [PMID: 18845162 DOI: 10.1016/j.jmb.2008.09.049] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 09/11/2008] [Accepted: 09/16/2008] [Indexed: 11/30/2022]
Abstract
Little is known about the thermodynamic forces that drive the folding pathways of higher-order RNA structure. In this study, we employ calorimetric [isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC)] and spectroscopic (NMR and UV) methods to characterize the thermodynamics of the GAAA tetraloop-receptor interaction, utilizing a previously described bivalent construct. ITC studies indicate that the bivalent interaction is enthalpy driven and highly stable, with a binding constant (K(obs)) of 5.5x10(6) M(-1) and enthalpy (DeltaH(obs)(o)) of -33.8 kcal/mol at 45 degrees C in 20 mM KCl and 2 mM MgCl(2). Thus, we derive the DeltaH(obs)(o) for a single tetraloop-receptor interaction to be -16.9 kcal/mol at these conditions. UV absorbance data indicate that an increase in base stacking quality contributes to the enthalpy of complex formation. These highly favorable thermodynamics are consistent with the known critical role for the tetraloop-receptor motif in the folding of large RNAs. Additionally, a significant heat capacity change (DeltaC(p,obs)(o)) of -0.24 kcal mol(-1) K(-1) was determined by ITC. DSC and UV-monitored thermal denaturation experiments indicate that the bivalent tetraloop-receptor construct follows a minimally five-state unfolding pathway and suggest the observed DeltaC(p,obs)(o) for the interaction results from a temperature-dependent unbound receptor RNA structure.
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Affiliation(s)
- Kirk A Vander Meulen
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Dr., Madison, WI 53706, USA
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40
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Monovalent and divalent promoted GAAA tetraloop-receptor tertiary interactions from freely diffusing single-molecule studies. Biophys J 2008; 95:3892-905. [PMID: 18621836 DOI: 10.1529/biophysj.108.134346] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proper assembly of RNA into catalytically active three-dimensional structures requires multiple tertiary binding interactions, individual characterization of which is crucial to a detailed understanding of global RNA folding. This work focuses on single-molecule fluorescence studies of freely diffusing RNA constructs that isolate the GAAA tetraloop-receptor tertiary interaction. Freely diffusing conformational dynamics are explored as a function of Mg(2+) and Na(+) concentration, both of which promote facile docking, but with 500-fold different affinities. Systematic shifts in mean fluorescence resonance energy transfer efficiency values and line widths with increasing [Na(+)] are observed for the undocked species and can be interpreted with a Debye model in terms of electrostatic relaxation and increased flexibility in the RNA. Furthermore, we identify a 34 +/- 2% fraction of freely diffusing RNA constructs remaining undocked even at saturating [Mg(2+)] levels, which agrees quantitatively with the 32 +/- 1% fraction previously reported for immobilized constructs. This verifies that the kinetic heterogeneity observed in the docking rates is not the result of surface tethering. Finally, the K(D) value and Hill coefficient for [Mg(2+)]-dependent docking decrease significantly for [Na(+)] = 25 mM vs. 125 mM, indicating Mg(2+) and Na(+) synergy in the RNA folding process.
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Abstract
This overview unit provides a thorough overview of biophysical methods used for structure analysis, including X-ray diffraction, nuclear magnetic resonance, optical spectroscopy, theoretical and computational methods, and single-molecule methods. Advantages and disadvantages of the methods are compared.
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Affiliation(s)
- I Tinoco
- University of California, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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42
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Sowa GZ, Qin PZ. Site-directed spin labeling studies on nucleic acid structure and dynamics. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2008; 82:147-97. [PMID: 18929141 DOI: 10.1016/s0079-6603(08)00005-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Site-directed spin labeling (SDSL) uses electron paramagnetic resonance (EPR) spectroscopy to monitor the behavior of a stable nitroxide radical attached at specific locations within a macromolecule such as protein, DNA, or RNA. Parameters obtained from EPR measurements, such as internitroxide distances and descriptions of the rotational motion of a nitroxide, provide unique information on features near the labeling site. With recent advances in solid-phase synthesis of nucleic acids and developments in EPR methodologies, particularly pulsed EPR technologies, SDSL has been increasingly used to study the structure and dynamics of DNA and RNA at the level of the individual nucleotides. This chapter summarizes the current SDSL studies on nucleic acids, with discussions focusing on literature from the last decade.
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Affiliation(s)
- Glenna Z Sowa
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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43
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Geary C, Baudrey S, Jaeger L. Comprehensive features of natural and in vitro selected GNRA tetraloop-binding receptors. Nucleic Acids Res 2007; 36:1138-52. [PMID: 18158305 PMCID: PMC2275092 DOI: 10.1093/nar/gkm1048] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Specific recognitions of GNRA tetraloops by small helical receptors are among the most widespread long-range packing interactions in large ribozymes. However, in contrast to GYRA and GAAA tetraloops, very few GNRA/receptor interactions have yet been identified to involve GGAA tetraloops in nature. A novel in vitro selection scheme based on a rigid self-assembling tectoRNA scaffold designed for isolation of intermolecular interactions with A-minor motifs has yielded new GGAA tetraloop-binding receptors with affinity in the nanomolar range. One of the selected receptors is a novel 12 nt RNA motif, (CCUGUG … AUCUGG), that recognizes GGAA tetraloop hairpin with a remarkable specificity and affinity. Its physical and chemical characteristics are comparable to those of the well-studied ‘11nt’ GAAA tetraloop receptor motif. A second less specific motif (CCCAGCCC … GAUAGGG) binds GGRA tetraloops and appears to be related to group IC3 tetraloop receptors. Mutational, thermodynamic and comparative structural analysis suggests that natural and in vitro selected GNRA receptors can essentially be grouped in two major classes of GNRA binders. New insights about the evolution, recognition and structural modularity of GNRA and A-minor RNA–RNA interactions are proposed.
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Affiliation(s)
- Cody Geary
- Department of Chemistry and Biochemistry, Biomolecular Science and Engineering Program, University of California at Santa Barbara, Santa Barbara, CA 93106-9510, USA
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44
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Tolbert BS, Kennedy SD, Schroeder SJ, Krugh TR, Turner DH. NMR structures of (rGCUGAGGCU)2 and (rGCGGAUGCU)2: probing the structural features that shape the thermodynamic stability of GA pairs. Biochemistry 2007; 46:1511-22. [PMID: 17279616 PMCID: PMC4032317 DOI: 10.1021/bi061350m] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The NMR structures of [see text] and [see text] are reported. The internal loop, [see text], is about 2 kcal/mol more stable than [see text] at 37 degrees C. The duplexes assemble into similar global folds characterized by the formation of tandem sheared GA pairs. The different stabilities of the loops are accompanied by differences in the local structure of the closing GU pairs. In the [see text] internal loop, the GU pairs form canonical wobble configurations with two hydrogen bonds, whereas in [see text], the GU pairs form a single hydrogen bond involving the amino group, GH22, and the carbonyl group, UO4. This pairing is similar to the GU closing pair of the 690 hairpin loop found in E. coli 16S rRNA. The [see text] and [see text] structures reveal how the subtle interplay between stacking and hydrogen bonding determines sequence dependent conformation and thermodynamic stability. Thus, this work provides structural and thermodynamic benchmarks for theoreticians in the ongoing effort to understand the sequence dependence of RNA physicochemical properties.
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Affiliation(s)
- Blanton S. Tolbert
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642
| | - Scott D. Kennedy
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642
| | - Susan J. Schroeder
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019-3051
| | - Thomas R. Krugh
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216
| | - Douglas H. Turner
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216
- Center for Pediatric Biomedical Research and Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642
- To whom correspondence should be addressed to: , (Phone) 585-275-3207, (Fax) 585-276-0205
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45
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Waldsich C, Pyle AM. A folding control element for tertiary collapse of a group II intron ribozyme. Nat Struct Mol Biol 2006; 14:37-44. [PMID: 17143279 DOI: 10.1038/nsmb1181] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2006] [Accepted: 11/13/2006] [Indexed: 11/09/2022]
Abstract
Ribozymes derived from the group II intron ai5gamma collapse to a compact intermediate, folding to the native state through a slow, direct pathway that is unperturbed by kinetic traps. Molecular collapse of ribozyme D135 requires high magnesium concentrations and is thought to involve a structural element in domain 1 (D1). We used nucleotide analog interference mapping, in combination with nondenaturing gel electrophoresis, to identify RNA substructures and functional groups that are essential for D135 tertiary collapse. This revealed that the most crucial atoms for compaction are located within a small section of D1 that includes the kappa and zeta elements. This small substructure controls specific collapse of the molecule and, in later steps of the folding pathway, it forms the docking site for catalytic D5. In this way, the stage is set for proper active site formation during the earliest steps of ribozyme folding.
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Affiliation(s)
- Christina Waldsich
- Department of Molecular Biophysics and Biochemistry, Yale University New Haven, Connecticut 06520, USA
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46
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Chen G, Kennedy SD, Qiao J, Krugh TR, Turner DH. An alternating sheared AA pair and elements of stability for a single sheared purine-purine pair flanked by sheared GA pairs in RNA. Biochemistry 2006; 45:6889-903. [PMID: 16734425 PMCID: PMC4121271 DOI: 10.1021/bi0524464] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A previous NMR structure of the duplex 5'GGU GGA GGCU/PCCG AAG CCG5' revealed an unusually stable RNA internal loop with three consecutive sheared GA pairs. Here, we report NMR studies of two duplexes, 5'GGU GGA GGCU/PCCA AAG CCG5' (replacing the UG pair with a UA closing pair) and 5'GGU GAA GGCU/PCCG AAG CCG5' (replacing the middle GA pair with an AA pair). An unusually stable loop with three consecutive sheared GA pairs forms in the duplex 5'GGU GGA GGCU/PCCA AAG CCG5'. The structure contrasts with that reported for this loop in the crystal structure of the large ribosomal subunit of Deinococcus radiodurans [Harms, J., Schluenzen, F., Zarivach, R., Bashan, A., Gat, S., Agmon, I., Bartels, H., Franceschi, F., and Yonath, A. (2001) Cell 107, 679-688]. The middle AA pair in the duplex 5'GGU GAA GGCU/PCCG AAG CCG5' rapidly exchanges orientations, resulting in alternative base stacking and pseudosymmetry with exclusively sheared pairs. The U GAA G/G AAG C internal loop is 2.1 kcal/mol less stable than the U GGA G/G AAG C internal loop at 37 degrees C. Structural, energetic, and dynamic consequences upon functional group substitutions within related 3 x 3 and 3 x 6 internal loops are also reported.
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Affiliation(s)
- Gang Chen
- Department of Chemistry, University of Rochester, RC Box 270216, Rochester, NY 14627
| | - Scott D. Kennedy
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, NY 14642
| | - Jing Qiao
- Department of Chemistry, University of Rochester, RC Box 270216, Rochester, NY 14627
| | - Thomas R. Krugh
- Department of Chemistry, University of Rochester, RC Box 270216, Rochester, NY 14627
| | - Douglas H. Turner
- Department of Chemistry, University of Rochester, RC Box 270216, Rochester, NY 14627
- Center for Pediatric Biomedical Research and Department of Pediatrics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642
- To whom correspondence should be addressed. Phone: (585) 275-3207. Fax: (585) 276-0205.
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47
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Downey CD, Fiore JL, Stoddard CD, Hodak JH, Nesbitt DJ, Pardi A. Metal ion dependence, thermodynamics, and kinetics for intramolecular docking of a GAAA tetraloop and receptor connected by a flexible linker. Biochemistry 2006; 45:3664-73. [PMID: 16533049 PMCID: PMC2735227 DOI: 10.1021/bi0520941] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The GAAA tetraloop-receptor motif is a commonly occurring tertiary interaction in RNA. This motif usually occurs in combination with other tertiary interactions in complex RNA structures. Thus, it is difficult to measure directly the contribution that a single GAAA tetraloop-receptor interaction makes to the folding properties of a RNA. To investigate the kinetics and thermodynamics for the isolated interaction, a GAAA tetraloop domain and receptor domain were connected by a single-stranded A(7) linker. Fluorescence resonance energy transfer (FRET) experiments were used to probe intramolecular docking of the GAAA tetraloop and receptor. Docking was induced using a variety of metal ions, where the charge of the ion was the most important factor in determining the concentration of the ion required to promote docking {[Co(NH(3))(6)(3+)] << [Ca(2+)], [Mg(2+)], [Mn(2+)] << [Na(+)], [K(+)]}. Analysis of metal ion cooperativity yielded Hill coefficients of approximately 2 for Na(+)- or K(+)-dependent docking versus approximately 1 for the divalent ions and Co(NH(3))(6)(3+). Ensemble stopped-flow FRET kinetic measurements yielded an apparent activation energy of 12.7 kcal/mol for GAAA tetraloop-receptor docking. RNA constructs with U(7) and A(14) single-stranded linkers were investigated by single-molecule and ensemble FRET techniques to determine how linker length and composition affect docking. These studies showed that the single-stranded region functions primarily as a flexible tether. Inhibition of docking by oligonucleotides complementary to the linker was also investigated. The influence of flexible versus rigid linkers on GAAA tetraloop-receptor docking is discussed.
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Affiliation(s)
| | | | | | | | | | - Arthur Pardi
- To whom correspondence should be addressed. E-mail: , Department of Chemistry and Biochemistry, 215 UCB, University of Colorado, Boulder, CO 80309. Phone (303) 492-6263. Fax (303) 492-2439
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48
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Abstract
New structural analysis methods, and a tree formalism re-define and expand the RNA motif concept, unifying what previously appeared to be disparate groups of structures. We find RNA tetraloops at high frequencies, in new contexts, with unexpected lengths, and in novel topologies. The results, with broad implications for RNA structure in general, show that even at this most elementary level of organization, RNA tolerates astounding variation in conformation, length, sequence and context. However the variation is not random; it is well-described by four distinct modes, which are 3-2 switches (backbone topology variations), insertions, deletions and strand clips.
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Affiliation(s)
| | | | - Eli Hershkovitz
- Departments of Electrical and Computer Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
- Department of Biomedical Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
| | - Allen Tannenbaum
- Departments of Electrical and Computer Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
- Department of Biomedical Engineering, Georgia Institute of TechnologyAtlanta, GA 30332-0400, USA
| | - Loren Dean Williams
- To whom correspondence should be addressed. Tel: +1 404 894 9752; Fax: +1 404 894 7452;
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Hershkovitz E, Sapiro G, Tannenbaum A, Williams LD. Statistical analysis of RNA backbone. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2006; 3:33-46. [PMID: 17048391 PMCID: PMC2811324 DOI: 10.1109/tcbb.2006.13] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Local conformation is an important determinant of RNA catalysis and binding. The analysis of RNA conformation is particularly difficult due to the large number of degrees of freedom (torsion angles) per residue. Proteins, by comparison, have many fewer degrees of freedom per residue. In this work, we use and extend classical tools from statistics and signal processing to search for clusters in RNA conformational space. Results are reported both for scalar analysis, where each torsion angle is separately studied, and for vectorial analysis, where several angles are simultaneously clustered. Adapting techniques from vector quantization and clustering to the RNA structure, we find torsion angle clusters and RNA conformational motifs. We validate the technique using well-known conformational motifs, showing that the simultaneous study of the total torsion angle space leads to results consistent with known motifs reported in the literature and also to the finding of new ones.
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Affiliation(s)
- Eli Hershkovitz
- The Schools of Electrical and Computer Engineering and Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250.
| | - Guillermo Sapiro
- The Electrical and Computer Engineering and Digital Technology Center, University of Minnesota, Minneapolis, MN 55455.
| | - Allen Tannenbaum
- The Schools of Electrical and Computer Engineering and Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250.
| | - Loren Dean Williams
- The School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332.
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Koplin J, Mu Y, Richter C, Schwalbe H, Stock G. Structure and dynamics of an RNA tetraloop: a joint molecular dynamics and NMR study. Structure 2005; 13:1255-67. [PMID: 16154083 DOI: 10.1016/j.str.2005.05.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2005] [Revised: 03/31/2005] [Accepted: 05/13/2005] [Indexed: 10/25/2022]
Abstract
Molecular dynamics simulations of the RNA tetraloop 5'-CGCUUUUGCG-3' with high melting temperature and significant conformational heterogeneity in explicit water solvent are presented and compared to NMR studies. The NMR data allow for a detailed test of the theoretical model, including the quality of the force field and the conformational sampling. Due to the conformational heterogeneity of the tetraloop, high temperature (350 K) and locally enhanced sampling simulations need to be invoked. The Amber98 force field leads to a good overall agreement with experimental data. Based on NMR data and a principal component analysis of the 350 K trajectory, the dynamic structure of the tetraloop is revealed. The principal component free energy surface exhibits four minima, which correspond to well-defined conformational structures that differ mainly by their base stacking in the loop region. No correlation between the motion of the sugar rings and the stacking dynamics of the loop bases is found.
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Affiliation(s)
- Jessica Koplin
- Institute of Physical and Theoretical Chemistry, Center for Biomolecular Magnetic Resonance, Johann Wolfgang Goethe-University, Frankfurt, Marie-Curie-Str 11, D-60439 Frankfurt/Main, Germany
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