1
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Karimi A, Wang K, Basran K, Copp W, Luedtke NW. A Bright and Ionizable Cytosine Mimic for i-Motif Structures. Bioconjug Chem 2023. [PMID: 37196003 DOI: 10.1021/acs.bioconjchem.3c00055] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
A new fluorescent cytosine analog "tsC" containing a trans-stilbene moiety was synthesized and incorporated into hemiprotonated base pairs that comprise i-motif structures. Unlike previously reported fluorescent base analogs, tsC mimics the acid-base properties of cytosine (pKa ≈ 4.3) while exhibiting bright (ε × Φ ≈ 1000 cm-1 M-1) and red-shifted fluorescence (λem = 440 → 490 nm) upon its protonation in the water-excluded interface of tsC+:C base pairs. Ratiometric analyses of tsC emission wavelengths facilitate real-time tracking of reversible conversions between single-stranded, double-stranded, and i-motif structures derived from the human telomeric repeat sequence. Comparisons between local changes in tsC protonation with global structure changes according to circular dichroism suggest partial formation of hemiprotonated base pairs in the absence of global i-motif structures at pH = 6.0. In addition to providing a highly fluorescent and ionizable cytosine analog, these results suggest that hemiprotonated C+:C base pairs can form in partially folded single-stranded DNA in the absence of global i-motif structures.
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Affiliation(s)
- Ashkan Karimi
- Department of Chemistry, McGill University, Montreal, Quebec H3A-0B8, Canada
- Centre de recherche en biologie structural, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Kaixiang Wang
- Department of Chemistry, McGill University, Montreal, Quebec H3A-0B8, Canada
| | - Kaleena Basran
- Department of Chemistry, McGill University, Montreal, Quebec H3A-0B8, Canada
| | - William Copp
- Department of Chemistry, McGill University, Montreal, Quebec H3A-0B8, Canada
| | - Nathan W Luedtke
- Department of Chemistry, McGill University, Montreal, Quebec H3A-0B8, Canada
- Centre de recherche en biologie structural, McGill University, Montreal, Quebec H3G 0B1, Canada
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3A-1A3, Canada
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2
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Zhang J. Probing RNA Structures and Interactions Using Fluorescence Lifetime Analyses. Methods Mol Biol 2023; 2568:13-23. [PMID: 36227559 PMCID: PMC11268537 DOI: 10.1007/978-1-0716-2687-0_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Structural analyses of large, complex noncoding RNAs continue to lag behind their rapid discovery and functional descriptions. Site-specifically incorporated, minimally invasive fluorescent probes such as 2-aminopurine (2AP) and pyrrolo-cytosine (PyC) have provided essential complementary information about local RNA structure, conformational dynamics, and interactions. Here I describe a protocol that benchmarks and correlates local RNA conformations with their respective fluorescence lifetimes, as a general technique that confers key advantages over fluorescence intensity-based methods. The observation that fluorescence lifetimes are more sensitive to local structures than sequence contexts suggests broad utility across diverse RNA and ribonucleoprotein systems.
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Affiliation(s)
- Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA.
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3
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Budow-Busse S, Jana SK, Kondhare D, Daniliuc C, Seela F. 8-Furylimidazolo-2'-deoxycytidine: crystal structure, packing, atropisomerism and fluorescence. Acta Crystallogr C Struct Chem 2022; 78:141-147. [PMID: 35245210 PMCID: PMC8896525 DOI: 10.1107/s2053229622001000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 01/28/2022] [Indexed: 11/10/2022] Open
Abstract
8-Furylimidazolo-2'-deoxycytidine (furImidC), C14H14N4O5, is a fluorescent analogue of 2'-deoxycytidine, also displaying the same recognition face. As a constituent of DNA, furImidC forms extraordinarily strong silver-mediated self-pairs. Crystal structure determination revealed that furImidC adopts two types of disordered residues: the sugar unit and the furyl moiety. The disorder of the sugar residue amounts to an 87:13 split. The disorder of the furyl ring results from axial chirality at the C8-C2'' bond connecting the nucleobase to the heterocycle. The two atropisomers are present in unequal proportions [occupancies of 0.69 (2) and 0.31 (2)], and the nucleobase and the furyl moiety are coplanar. Considering the atomic sites with predominant occupancy, an anti conformation with χ = - 147.2 (7)° was found at the glycosylic bond and the 2'-deoxyribosyl moiety shows a C2'-endo (S, 2T1) conformation, with P = 160.0°. A 1H NMR-based conformational analysis of the furanose puckering revealed that the S conformation predominates also in solution. In the solid state, two neighbouring furImidC molecules are arranged in a head-to-tail fashion, but with a notable tilt of the molecules with respect to each other. Consequently, one N-H...N hydrogen bond is found for neighbouring molecules within one layer, while a second N-H...N hydrogen bond is formed to a molecule of an adjacent layer. In addition, hydrogen bonding is observed between the nucleobase and the sugar residue. A Hirshfeld surface analysis was performed to visualize the intermolecular interactions observed in the X-ray study. In addition, the fluorescence spectra of furImidC were measured in solvents of different polarity and viscosity. furImidC responds to microenvironmental changes (polarity and viscosity), which is explained by a hindered rotation of the furyl residue in solvents of high viscosity.
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Affiliation(s)
- Simone Budow-Busse
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Heisenbergstrasse 11, 48149 Münster, Germany
| | - Sunit K. Jana
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Heisenbergstrasse 11, 48149 Münster, Germany
| | - Dasharath Kondhare
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Heisenbergstrasse 11, 48149 Münster, Germany
| | - Constantin Daniliuc
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Frank Seela
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Heisenbergstrasse 11, 48149 Münster, Germany
- Laboratorium für Organische und Bioorganische Chemie, Institut für Chemie, Universität Osnabrück, Barbarastrasse 7, 49069 Osnabrück, Germany
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4
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Yaeger LN, Coles VE, Chan DCK, Burrows LL. How to kill Pseudomonas-emerging therapies for a challenging pathogen. Ann N Y Acad Sci 2021; 1496:59-81. [PMID: 33830543 DOI: 10.1111/nyas.14596] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 03/08/2021] [Accepted: 03/11/2021] [Indexed: 12/16/2022]
Abstract
As the number of effective antibiotics dwindled, antibiotic resistance (AR) became a pressing concern. Some Pseudomonas aeruginosa isolates are resistant to all available antibiotics. In this review, we identify the mechanisms that P. aeruginosa uses to evade antibiotics, including intrinsic, acquired, and adaptive resistance. Our review summarizes many different approaches to overcome resistance. Antimicrobial peptides have potential as therapeutics with low levels of resistance evolution. Rationally designed bacteriophage therapy can circumvent and direct evolution of AR and virulence. Vaccines and monoclonal antibodies are highlighted as immune-based treatments targeting specific P. aeruginosa antigens. This review also identifies promising drug combinations, antivirulence therapies, and considerations for new antipseudomonal discovery. Finally, we provide an update on the clinical pipeline for antipseudomonal therapies and recommend future avenues for research.
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Affiliation(s)
- Luke N Yaeger
- Department of Biochemistry and Biomedical Sciences and M.G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Victoria E Coles
- Department of Biochemistry and Biomedical Sciences and M.G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Derek C K Chan
- Department of Biochemistry and Biomedical Sciences and M.G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Lori L Burrows
- Department of Biochemistry and Biomedical Sciences and M.G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
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5
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Mariam J, Krishnamoorthy G, Anand R. Use of 6‐Methylisoxanthopterin, a Fluorescent Guanine Analog, to Probe Fob1‐Mediated Dynamics at the Stalling Fork Barrier DNA Sequences. Chem Asian J 2019; 14:4760-4766. [DOI: 10.1002/asia.201901061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 09/19/2019] [Indexed: 12/19/2022]
Affiliation(s)
- Jessy Mariam
- Department of ChemistryIndian Institute of Technology Bombay Powai Mumbai 400076 Maharashtra India
| | | | - Ruchi Anand
- Department of ChemistryIndian Institute of Technology Bombay Powai Mumbai 400076 Maharashtra India
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6
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McGovern-Gooch KR, Baird NJ. Fluorescence-based investigations of RNA-small molecule interactions. Methods 2019; 167:54-65. [PMID: 31129289 DOI: 10.1016/j.ymeth.2019.05.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 05/08/2019] [Accepted: 05/20/2019] [Indexed: 12/17/2022] Open
Abstract
Interrogating non-coding RNA structures and functions with small molecules is an area of rapidly increasing interest among biochemists and chemical biologists. However, many biochemical approaches to monitoring RNA structures are time-consuming and low-throughput, and thereby are only of limited utility for RNA-small molecule studies. Fluorescence-based techniques are powerful tools for rapid investigation of RNA conformations, dynamics, and interactions with small molecules. Many fluorescence methods are amenable to high-throughput analysis, enabling library screening for small molecule binders. In this review, we summarize numerous fluorescence-based approaches for identifying and characterizing RNA-small molecule interactions. We describe in detail a high-information content dual-reporter FRET assay we developed to characterize small molecule-induced conformational and stability changes. Our assay is uniquely suited as a platform for both small molecule discovery and thorough characterization of RNA-small molecule binding mechanisms. Given the growing recognition of non-coding RNAs as attractive targets for therapeutic intervention, we anticipate our FRET assay and other fluorescence-based techniques will be indispensable for the development of potent and specific small molecule inhibitors targeting RNA.
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Affiliation(s)
- Kayleigh R McGovern-Gooch
- Department of Chemistry & Biochemistry, University of the Sciences, Philadelphia, PA 19104 United States
| | - Nathan J Baird
- Department of Chemistry & Biochemistry, University of the Sciences, Philadelphia, PA 19104 United States.
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7
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Bull GD, Thompson KC. Proton Transfer and Tautomerism in 2-Aminopurine-Thymine and Pyrrolocytosine-Guanine Base Pairs. Biochemistry 2018; 57:4547-4561. [PMID: 30024730 DOI: 10.1021/acs.biochem.8b00521] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Pyrrolocytosine (PC) and 2-aminopurine (2AP) are fluorescent nucleobase analogues of the DNA nucleobases cytosine and adenine, respectively, and form base pairs with guanine and thymine. Both fluorescent nucleobases are used extensively as probes for local structure in nucleic acids as the fluorescence properties of PC and 2AP are very sensitive to changes such as helix formation, although the reasons for this sensitivity are not clear. To address this question, ab initio calculations have been used to calculate energies, at the MP2 and CIS level, of three different tautomer pairings of PC-G, and two of 2AP-T, which can potentially be interconverted by double proton transfer between the bases. Potential energy curves linking the different tautomer pairs have been calculated. For both PC-G and 2AP-T, the most stable tautomer pair in the electronic ground state is that analogous to the natural C-G and A-T base pair. In the case of 2AP-T, an alternative, stable, tautomer base pair was located in the first electronically excited state; however, it lies higher in energy than the tautomer pair analogous to A-T, making conversion to the alternative form unlikely. In contrast, in the case of PC-G, an alternative tautomer base pair is found to be the most stable form in the first electronically excited state, and this form is accessible following initial excitation from the ground state tautomer pair, thus suggesting an alternative deactivation route via double proton transfer may be possible when PC is involved in hydrogen bonding, such as occurs in helical conformations.
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Affiliation(s)
- Graham D Bull
- Department of Biological Sciences and Institute of Structural and Molecular Biology, Birkbeck , University of London , Malet Street , Bloomsbury, London WC1E 7HX , U.K
| | - Katherine C Thompson
- Department of Biological Sciences and Institute of Structural and Molecular Biology, Birkbeck , University of London , Malet Street , Bloomsbury, London WC1E 7HX , U.K
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8
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Monovalent ions modulate the flux through multiple folding pathways of an RNA pseudoknot. Proc Natl Acad Sci U S A 2018; 115:E7313-E7322. [PMID: 30012621 PMCID: PMC6077692 DOI: 10.1073/pnas.1717582115] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The assembly mechanism of RNA, vital to describing its functions, depends on both the sequence and the metal ion concentration. How the latter influences the folding trajectories remains an important unsolved problem. Here, we examine the folding pathways of an RNA pseudoknot (PK) with key functional roles in transcription and translation, using a combination of experiments and simulations. We demonstrate that the PK, consisting of two hairpins with differing stabilities, folds by parallel pathways. Surprisingly, the flux between them is modulated by monovalent salt concentration. Our work shows that the order of assembly of PKs is determined by the relative stability of the hairpins, implying that the folding landscape can be controlled by sequence and ion concentration. The functions of RNA pseudoknots (PKs), which are minimal tertiary structural motifs and an integral part of several ribozymes and ribonucleoprotein complexes, are determined by their structure, stability, and dynamics. Therefore, it is important to elucidate the general principles governing their thermodynamics/folding mechanisms. Here, we combine laser temperature-jump experiments and coarse-grained simulations to determine the folding/unfolding pathways of VPK, a variant of the mouse mammary tumor virus (MMTV) PK involved in ribosomal frameshifting. Fluorescent nucleotide analogs (2-aminopurine and pyrrolocytidine) placed at different stem/loop positions in the PK serve as local probes allowing us to monitor the order of assembly of VPK that has two constituent hairpins with different intrinsic stabilities. We show that at 50 mM KCl, the dominant folding pathway populates only the more stable hairpin intermediate; as the salt concentration is increased, a parallel folding pathway emerges involving the less stable hairpin as an alternate intermediate. Notably, the flux between the pathways is modulated by the ionic strength. Our findings support the principle that the order of PK structure formation is determined by the relative stabilities of the hairpins, which can be altered by sequence variations or salt concentrations. The experimental results of salt effects on the partitioning between the two folding pathways are in remarkable agreement with simulations that were performed with no adjustable parameters. Our study not only unambiguously demonstrates that VPK folds by parallel pathways but also showcases the power of combining experiments and simulations for a more enriched description of RNA self-assembly.
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9
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Nguyen QL, Spata VA, Matsika S. Photophysical properties of pyrrolocytosine, a cytosine fluorescent base analogue. Phys Chem Chem Phys 2018; 18:20189-98. [PMID: 27251599 DOI: 10.1039/c6cp01559j] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The photophysical behavior of pyrrolocytosine (PC), a fluorescent base analogue of cytosine, has been investigated using theoretical approaches. The similarities between the PC and cytosine structures allow PC to maintain the pseudo-Watson-Crick base-pairing arrangement with guanine. Cytosine, similar to the other natural nucleobases, is practically non-fluorescent, because of ultrafast radiationless decay occurring through conical intersections. PC displays a much higher fluorescence quantum yield than cytosine, making it an effective fluorescent marker to study the structure, function, and dynamics of DNA/RNA complexes. Similar to 2-aminopurine, a constitutional isomer of adenine that base-pairs with thymine, PC's fluorescence is quenched when it is incorporated into a dinucleotide or a trinucleotide. In this work we examine the photophysical properties of isolated PC, microhydrated PC, as well as, complexes where PC is either base-stacked or hydrogen-bonded with guanine. Our results indicate that hydration affects the radiationless decay pathways in PC by destabilizing conical intersections. The calculations of dimers and trimers show that the radiative decay is affected by π stacking, while the presence of charge transfer states between PC and guanine may contribute to radiationless decay.
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10
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Wang W, Sheng X, Zhang S, Huang F, Sun C, Liu J, Chen D. Theoretical insights into the structural and fluorescence properties of DNA containing fluorescent nucleobases. Phys Chem Chem Phys 2018; 20:16641-16649. [DOI: 10.1039/c8cp02295j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The structural and fluorescence properties of DNA containing fluorescent nucleobases are explored in detail. In particular, the effect of stacking with different neighboring bases on fluorescence properties is elucidated.
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Affiliation(s)
- Wenjuan Wang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Xiehuang Sheng
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Shaolong Zhang
- College of Physics and Electronics
- Shandong Normal University
- Jinan 250014
- P. R. China
| | - Fang Huang
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Chuanzhi Sun
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Jianbiao Liu
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
| | - Dezhan Chen
- College of Chemistry
- Chemical Engineering and Materials Science
- Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong
- Key Laboratory of Molecular and Nano Probes
- Ministry of Education
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11
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Ro JJ, Go GH, Wilhelmsson LM, Kim BH. Fluorescence properties of 6-aryl-2'-deoxy-furanouridine and -pyrrolocytidine and their derivatives. Methods Appl Fluoresc 2017; 6:015004. [PMID: 28933349 DOI: 10.1088/2050-6120/aa8e19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
2'-deoxyfuranouridine derivatives presenting various aryl groups have been synthesized through Cu(I)-catalyzed intramolecular cyclizations. Moreover, corresponding pyrrolo-dC derivatives have been synthesized and both families of compounds thoroughly characterized using UV/vis and fluorescence spectroscopy as well as time-dependent density functional theory calculations. The photophysical characterization, show that our newly synthesized derivatives of the important pyrrolo-dC family have high fluorescence quantum yields (QYs) and brightness values. Pyrrolo-dC derivative, 3a, shows an environment sensitive QY of up to >60% and brightness of almost 3000, in low polarity solvents and excitation and emission maxima between 365-381 nm and 479-510 nm, respectively, in solvents of different polarities. Two other derivatives, 3b and 3c, show high QYs and brightness values of up to 3300 that are fairly insensitive to their microenvironment. These promising photophysical features suggest future applicability as fluorescent nucleobase analogs.
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Affiliation(s)
- Jong Jin Ro
- Department of Chemistry, Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
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12
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McAninch DS, Heinaman AM, Lang CN, Moss KR, Bassell GJ, Rita Mihailescu M, Evans TL. Fragile X mental retardation protein recognizes a G quadruplex structure within the survival motor neuron domain containing 1 mRNA 5'-UTR. MOLECULAR BIOSYSTEMS 2017; 13:1448-1457. [PMID: 28612854 PMCID: PMC5544254 DOI: 10.1039/c7mb00070g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
G quadruplex structures have been predicted by bioinformatics to form in the 5'- and 3'-untranslated regions (UTRs) of several thousand mature mRNAs and are believed to play a role in translation regulation. Elucidation of these roles has primarily been focused on the 3'-UTR, with limited focus on characterizing the G quadruplex structures and functions in the 5'-UTR. Investigation of the affinity and specificity of RNA binding proteins for 5'-UTR G quadruplexes and the resulting regulatory effects have also been limited. Among the mRNAs predicted to form a G quadruplex structure within the 5'-UTR is the survival motor neuron domain containing 1 (SMNDC1) mRNA, encoding a protein that is critical to the spliceosome. Additionally, this mRNA has been identified as a potential target of the fragile X mental retardation protein (FMRP), whose loss of expression leads to fragile X syndrome. FMRP is an RNA binding protein involved in translation regulation that has been shown to bind mRNA targets that form G quadruplex structures. In this study we have used biophysical methods to investigate G quadruplex formation in the 5'-UTR of SMNDC1 mRNA and analyzed its interactions with FMRP. Our results show that SMNDC1 mRNA 5'-UTR forms an intramolecular, parallel G quadruplex structure comprised of three G quartet planes, which is bound specifically by FMRP both in vitro and in mouse brain lysates. These findings suggest a model by which FMRP might regulate the translation of a subset of its mRNA targets by recognizing the G quadruplex structure present in their 5'-UTR, and affecting their accessibility by the protein synthesis machinery.
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Affiliation(s)
- Damian S McAninch
- Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, USA.
| | - Ashley M Heinaman
- Department of Chemistry, University of Pittsburgh at Johnstown, Johnstown, Pennsylvania 15904, USA
| | - Cara N Lang
- Department of Chemistry, University of Pittsburgh at Johnstown, Johnstown, Pennsylvania 15904, USA
| | - Kathryn R Moss
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - Mihaela Rita Mihailescu
- Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, USA.
| | - Timothy L Evans
- Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, USA. and Department of Chemistry, University of Pittsburgh at Johnstown, Johnstown, Pennsylvania 15904, USA
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13
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Aro-Heinilä A, Lönnberg T. Fluorescent Oligonucleotide Probes for Screening High-Affinity Nucleobase Surrogates. Chemistry 2016; 23:1028-1031. [PMID: 27911048 DOI: 10.1002/chem.201605300] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Indexed: 12/16/2022]
Abstract
Double-helical oligonucleotide probes featuring a single-nucleotide gap opposed by one of the canonical nucleobases and flanked by the fluorescent nucleobase analogue pyrrolocytosine have been synthesized and titrated with PdII chelates of dipicolinamide and its N2 ,N6 -dialkylated derivatives. The fluorometric titrations revealed greatly increased affinity of the PdII chelates for the nucleobases opposing the gap compared to the respective free nucleotides in solution. Owing to the constrained environment of the single-nucleotide gap, the relative stabilities of the various PdII -mediated base pairs were also significantly different from those previously reported at monomer level.
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Affiliation(s)
- Asmo Aro-Heinilä
- Department of Chemistry, University of Turku, Vatselankatu 2, 20014, Turku, Finland
| | - Tuomas Lönnberg
- Department of Chemistry, University of Turku, Vatselankatu 2, 20014, Turku, Finland
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14
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Nguyen JC, Dzowo YK, Wolfbrandt C, Townsend J, Kukatin S, Wang H, Resendiz MJE. Synthesis, Thermal Stability, Biophysical Properties, and Molecular Modeling of Oligonucleotides of RNA Containing 2'-O-2-Thiophenylmethyl Groups. J Org Chem 2016; 81:8947-8958. [PMID: 27584708 DOI: 10.1021/acs.joc.6b01615] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Dodecamers of RNA [CUACGGAAUCAU] were functionalized with C2'-O-2-thiophenylmethyl groups to obtain oligonucleotides 10-14 and 17. The modified nucleotides were incorporated into RNA strands via solid-phase synthesis. The biophysical properties of these ONs were used to quantify the effects of this modification on RNA:RNA and RNA:DNA duplexes. A combination of UV-vis and circular dichroism were used to determine thermal stabilities of all strands, which hybridized into A-form geometries. Destabilization of the double stranded RNA was measured as a function of number of consecutive modifications, reflected in decreased thermal denaturation values (ΔTm, ca. 2.5-11.5 °C). Van't Hoff plots on a duplex containing one modification (10:15) displayed a ca. ΔΔG° of +4 kcal/mol with respect to its canonical analogue. Interestingly, hybridization of two modified strands (13:17, containing a total of eight modifications) resulted in increased stability and a distinct secondary structure, reflected in its CD spectrum. Molecular modeling based on DFT calculations shed light on the nature of this stability, with induced changes in the torsional angle δ (C5'-C4'-C3'-O3) and phosphate-phosphate distances that are in agreement with a compacted structure. The described synthetic methodology and structural information will be useful in the design of thermodynamically stable structures containing chemically reactive modifications.
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Affiliation(s)
- Joseph C Nguyen
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Yannick Kokouvi Dzowo
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Carly Wolfbrandt
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Justin Townsend
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Stanislav Kukatin
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Haobin Wang
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
| | - Marino J E Resendiz
- Department of Chemistry, University of Colorado Denver , Science Building 1151 Arapahoe Street, Denver, Colorado 80204, United States
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15
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Freeman NS, Moore CE, Wilhelmsson LM, Tor Y. Chromophoric Nucleoside Analogues: Synthesis and Characterization of 6-Aminouracil-Based Nucleodyes. J Org Chem 2016; 81:4530-9. [PMID: 27128151 PMCID: PMC5493935 DOI: 10.1021/acs.joc.6b00310] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Nucleodyes, visibly colored chromophoric nucleoside analogues, are reported. Design criteria are outlined and the syntheses of cytidine and uridine azo dye analogues derived from 6-aminouracil are described. Structural analysis shows that the nucleodyes are sound structural analogues of their native nucleoside counterparts, and photophysical studies demonstrate that the nucleodyes are sensitive to microenvironmental changes. Quantum chemical calculations are presented as a valuable complementary tool for the design of strongly absorbing nucleodyes, which overlap with the emission of known fluorophores. Förster critical distance (R0) calculations determine that the nucleodyes make good FRET pairs with both 2-aminopurine (2AP) and pyrrolocytosine (PyC). Additionally, unique tautomerization features exhibited by 5-(4-nitrophenylazo)-6-oxocytidine (8) are visualized by an extraordinary crystal structure.
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Affiliation(s)
- Noam S. Freeman
- Department of Chemistry and Biochemistry, University of
California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, United
States
| | - Curtis E. Moore
- Department of Chemistry and Biochemistry, University of
California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, United
States
| | - L. Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering/Chemistry
and Biochemistry, Chalmers University of Technology, Gothenburg 41296, Sweden
| | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of
California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, United
States
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16
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Johnson NP, Ji H, Steinberg TH, von Hippel PH, Marcus AH. Sequence-Dependent Conformational Heterogeneity and Proton-Transfer Reactivity of the Fluorescent Guanine Analogue 6-Methyl Isoxanthopterin (6-MI) in DNA. J Phys Chem B 2015; 119:12798-807. [PMID: 26368400 DOI: 10.1021/acs.jpcb.5b06361] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The local conformations of individual nucleic acid bases in DNA are important components in processes fundamental to gene regulation. Fluorescent nucleic acid base analogues, which can be substituted for natural bases in DNA, can serve as useful spectroscopic probes of average local base conformation and conformational heterogeneity. Here we report excitation-emission peak shift (EES) measurements of the fluorescent guanine (G) analogue 6-methyl isoxanthoptherin (6-MI), both as a ribonucleotide monophosphate (NMP) in solution and as a site-specific substituent for G in various DNA constructs. Changes in the peak positions of the fluorescence spectra as a function of excitation energy indicate that distinct subpopulations of conformational states exist in these samples on time scales longer than the fluorescence lifetime. Our pH-dependent measurements of the 6-MI NMP in solution show that these states can be identified as protonated and deprotonated forms of the 6-MI fluorescent probe. We implement a simple two-state model, which includes four vibrationally coupled electronic levels to estimate the free energy change, the free energy of activation, and the equilibrium constant for the proton transfer reaction. These parameters vary in single-stranded and duplex DNA constructs, and also depend on the sequence context of flanking bases. Our results suggest that proton transfer in 6-MI-substituted DNA constructs is coupled to conformational heterogeneity of the probe base, and can be interpreted to suggest that Watson-Crick base pairing between 6-MI and its complementary cytosine in duplex DNA involves a "low-barrier-hydrogen-bond". These findings may be important in using the 6-MI probe to understand local base conformational fluctuations, which likely play a central role in protein-DNA and ligand-DNA interactions.
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Affiliation(s)
- Neil P Johnson
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States.,Oregon Center for Optics and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States
| | - Huiying Ji
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States.,Oregon Center for Optics and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States
| | - Thomas H Steinberg
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States
| | - Peter H von Hippel
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States
| | - Andrew H Marcus
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States.,Oregon Center for Optics and Department of Chemistry and Biochemistry, University of Oregon , Eugene, Oregon 97403, United States
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17
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Edwards SK, Ono T, Wang S, Jiang W, Franzini RM, Jung JW, Chan KM, Kool ET. In Vitro Fluorogenic Real-Time Assay of the Repair of Oxidative DNA Damage. Chembiochem 2015; 16:1637-46. [PMID: 26073452 PMCID: PMC4586133 DOI: 10.1002/cbic.201500184] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Indexed: 01/09/2023]
Abstract
The repair of oxidative damage to DNA is essential to avoid mutations that lead to cancer. Oxidized DNA bases, such as 8-oxoguanine, are a main source of these mutations, and the enzyme 8-oxoguanine glycosylase 1 (OGG1) is the chief human enzyme that excises 8-oxoguanine from DNA. The activity of OGG1 has been linked to human inflammation responses and to cancer, and researchers are beginning to search for inhibitors of the enzyme. However, measuring the activity of the enzyme typically requires laborious gel-based measurements of radiolabeled DNAs. Here we report the design and properties of fluorogenic probes that directly report on the activity of OGG1 (and its bacterial homologue Fpg) in real time as the oxidized base is excised. The probes are short, modified DNA oligomers containing fluorescent DNA bases and are designed to utilize 8-oxoguanine itself as a fluorescence quencher. Screening of combinations of fluorophores and 8-oxoguanine revealed two fluorophores, pyrene and tCo, that are strongly quenched by the damaged base. We tested 42 potential probes containing these fluorophores: the optimum probe, OGR1, yields a 60-fold light-up signal in vitro with OGG1 and Fpg. It can report on oxidative repair activity in mammalian cell lysate and with bacterial cells overexpressing a repair enzyme. Such probes might prove useful in quantifying enzyme activity and performing competitive inhibition assays.
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Affiliation(s)
- Sarah K Edwards
- Department of Chemistry, Stanford University, Stanford, CA 94305 (USA)
| | - Toshikazu Ono
- Department of Chemistry, Stanford University, Stanford, CA 94305 (USA)
- Present Address: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 (Japan)
| | - Shenliang Wang
- Department of Chemistry, Stanford University, Stanford, CA 94305 (USA)
| | - Wei Jiang
- Department of Chemistry, Stanford University, Stanford, CA 94305 (USA)
| | | | - Jong Wha Jung
- Department of Chemistry, Stanford University, Stanford, CA 94305 (USA)
- Present Address: College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University, Daegu, 702-701 (Republic of Korea)
| | - Ke Min Chan
- Department of Chemistry, Stanford University, Stanford, CA 94305 (USA)
| | - Eric T Kool
- Department of Chemistry, Stanford University, Stanford, CA 94305 (USA).
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18
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Taherpour S, Lönnberg T. Fluorescence probing of metal-ion-mediated hybridization of oligonucleotides. RSC Adv 2015. [DOI: 10.1039/c4ra15136d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The structure-dependent fluorescence of pyrrolocytosine has been harnessed to quantify the affinity of metal-ion-chelating oligonucleotides for their native counterparts.
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19
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Hein PP, Kolb KE, Windgassen T, Bellecourt MJ, Darst SA, Mooney RA, Landick R. RNA polymerase pausing and nascent-RNA structure formation are linked through clamp-domain movement. Nat Struct Mol Biol 2014; 21:794-802. [PMID: 25108353 PMCID: PMC4156911 DOI: 10.1038/nsmb.2867] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 07/03/2014] [Indexed: 12/11/2022]
Abstract
The rates of RNA synthesis and the folding of nascent RNA into biologically active structures are linked via pausing by RNA polymerase (RNAP). Structures that form within the RNA-exit channel can either increase pausing by interacting with RNAP or decrease pausing by preventing backtracking. Conversely, pausing is required for proper folding of some RNAs. Opening of the RNAP clamp domain has been proposed to mediate some effects of nascent-RNA structures. However, the connections among RNA structure formation and RNAP clamp movement and catalytic activity remain uncertain. Here, we assayed exit-channel structure formation in Escherichia coli RNAP with disulfide cross-links that favor closed- or open-clamp conformations and found that clamp position directly influences RNA structure formation and RNAP catalytic activity. We report that exit-channel RNA structures slow pause escape by favoring clamp opening through interactions with the flap that slow translocation.
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Affiliation(s)
- Pyae P. Hein
- Department of Biochemistry, University of Wisconsin – Madison, Madison, WI 53706, USA
| | - Kellie E. Kolb
- Department of Biochemistry, University of Wisconsin – Madison, Madison, WI 53706, USA
| | - Tricia Windgassen
- Department of Biochemistry, University of Wisconsin – Madison, Madison, WI 53706, USA
| | - Michael J. Bellecourt
- Department of Biochemistry, University of Wisconsin – Madison, Madison, WI 53706, USA
| | - Seth A. Darst
- Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Rachel A. Mooney
- Department of Biochemistry, University of Wisconsin – Madison, Madison, WI 53706, USA
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin – Madison, Madison, WI 53706, USA
- Department of Bacteriology, University of Wisconsin – Madison, Madison, WI 53706, USA
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20
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Kovaliov M, Weitman M, Major DT, Fischer B. Phenyl-imidazolo-cytidine Analogues: Structure–Photophysical Activity Relationship and Ability To Detect Single DNA Mismatch. J Org Chem 2014; 79:7051-62. [DOI: 10.1021/jo5011944] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Marina Kovaliov
- Department of Chemistry,
Gonda-Goldschmied Medical Research Center and the Lise-Meitner-Minerva
Center of Computational Quantum Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Michal Weitman
- Department of Chemistry,
Gonda-Goldschmied Medical Research Center and the Lise-Meitner-Minerva
Center of Computational Quantum Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Dan Thomas Major
- Department of Chemistry,
Gonda-Goldschmied Medical Research Center and the Lise-Meitner-Minerva
Center of Computational Quantum Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Bilha Fischer
- Department of Chemistry,
Gonda-Goldschmied Medical Research Center and the Lise-Meitner-Minerva
Center of Computational Quantum Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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21
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Zhang J, Ferré-D'Amaré AR. Direct evaluation of tRNA aminoacylation status by the T-box riboswitch using tRNA-mRNA stacking and steric readout. Mol Cell 2014; 55:148-55. [PMID: 24954903 DOI: 10.1016/j.molcel.2014.05.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 03/28/2014] [Accepted: 04/08/2014] [Indexed: 01/01/2023]
Abstract
T-boxes are gene-regulatory mRNA elements with which Gram-positive bacteria sense amino acid availability. T-boxes have two functional domains. Stem I recognizes the overall shape and anticodon of tRNA, while a 3' domain evaluates its aminoacylation status, overcoming an otherwise stable transcriptional terminator if the bound tRNA is uncharged. Although T-boxes are believed to evaluate tRNA charge status without using any proteins, this has not been demonstrated experimentally because of the instability of aminoacyl-tRNA. Using a simple method to prepare homogeneous aminoacyl-tRNA, we show that the Bacillus subtilis glyQS T-box functions independently of any tRNA-binding protein. Comparison of aminoacyl-tRNA analogs demonstrates that the T-box detects the molecular volume of tRNA 3'-substituents. Calorimetry and fluorescence lifetime analysis of labeled RNAs shows that the tRNA acceptor end coaxially stacks on a helix in the T-box 3' domain. This intimate intermolecular association, selective for uncharged tRNA, stabilizes the antiterminator conformation of the T-box.
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Affiliation(s)
- Jinwei Zhang
- National Heart, Lung and Blood Institute, 50 South Drive, MSC 8012, Bethesda, MD 20892-8012, USA
| | - Adrian R Ferré-D'Amaré
- National Heart, Lung and Blood Institute, 50 South Drive, MSC 8012, Bethesda, MD 20892-8012, USA.
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22
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Alemán E, de Silva C, Patrick EM, Musier-Forsyth K, Rueda D. Single-Molecule Fluorescence Using Nucleotide Analogs: A Proof-of-Principle. J Phys Chem Lett 2014; 5:777-781. [PMID: 24803990 PMCID: PMC3985717 DOI: 10.1021/jz4025832] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 02/06/2014] [Indexed: 05/25/2023]
Abstract
Fluorescent nucleotide analogues, such as 2-aminopurine (2AP) and pyrrolo-C (PyC), have been extensively used to study nucleic acid local conformational dynamics in bulk experiments. Here we present a proof-of-principle approach using 2AP and PyC fluorescence at the single-molecule level. Our data show that ssDNA, dsDNA, or RNA containing both 2AP and PyC can be monitored using single-molecule fluorescence and a click chemistry immobilization method. We demonstrate that this approach can be used to monitor DNA and RNA in real time. This is the first reported assay using fluorescent nucleotide analogs at the single-molecule level. We anticipate that single 2AP or PyC fluorescence will have numerous applications in studies of DNA and RNA, including protein-induced base-flipping dynamics in protein-nucleic acid complexes.
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Affiliation(s)
- Elvin
A. Alemán
- Department
of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
| | - Chamaree de Silva
- Department
of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Eric M. Patrick
- Department
of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
| | - Karin Musier-Forsyth
- Department
of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - David Rueda
- Department
of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
- Department of Medicine, Section of
Virology and Single Molecule Imaging Group,
MRC Clinical Sciences Center, Imperial College, Du Cane Road, London W12 0NN, United
Kingdom
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23
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Dziuba D, Karpenko IA, Barthes NPF, Michel BY, Klymchenko AS, Benhida R, Demchenko AP, Mély Y, Burger A. Rational Design of a Solvatochromic Fluorescent Uracil Analogue with a Dual-Band Ratiometric Response Based on 3-Hydroxychromone. Chemistry 2014; 20:1998-2009. [DOI: 10.1002/chem.201303399] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Indexed: 12/24/2022]
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24
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Tanpure AA, Pawar MG, Srivatsan SG. Fluorescent Nucleoside Analogs: Probes for Investigating Nucleic Acid Structure and Function. Isr J Chem 2013. [DOI: 10.1002/ijch.201300010] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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25
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Seio K, Kanamori T, Tokugawa M, Ohzeki H, Masaki Y, Tsunoda H, Ohkubo A, Sekine M. Fluorescent properties of oligonucleotides doubly modified with an indole-fused cytosine analog and 2-aminopurine. Bioorg Med Chem 2013; 21:3197-201. [PMID: 23628471 DOI: 10.1016/j.bmc.2013.03.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 03/14/2013] [Accepted: 03/15/2013] [Indexed: 11/16/2022]
Abstract
Single- and double-stranded oligodeoxynucleotides (ODNs) incorporating both 2-aminopurine (2AP) and an indole-fused cytosine analog (PPI) were prepared and studied for their fluorescence properties. PPI and 2AP can be excited simultaneously by irradiation at 300 nm, with emission observed at 500 nm for PPI and 370 nm for 2AP. We demonstrated the utility of these properties in the dual fluorescence labeling of ODNs giving well-separated emission peaks. In addition, both of the fluorescence signals of a doubly modified ODN changed independently, reflecting the local duplex formation at the regions containing 2AP or PPI. Potential applications of this strategy for the dual fluorescence labeling of oligonucleotides with 2AP and PPI include monitoring local structure alterations of functional nucleic acids and the multiplex detection of biologically important nucleic acids.
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Affiliation(s)
- Kohji Seio
- Department of Life Science, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
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26
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Tanpure AA, Srivatsan SG. Synthesis and photophysical characterisation of a fluorescent nucleoside analogue that signals the presence of an abasic site in RNA. Chembiochem 2012; 13:2392-9. [PMID: 23070860 DOI: 10.1002/cbic.201200408] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Indexed: 11/07/2022]
Abstract
The synthesis and site-specific incorporation of an environment-sensitive fluorescent nucleoside analogue (2), based on a 5-(benzofuran-2-yl)pyrimidine core, into DNA oligonucleotides (ONs), and its photophysical properties within these ONs are described. Interestingly and unlike 2-aminopurine (a widely used nucleoside analogue probe), when incorporated into an ON and hybridised with a complementary ON, the emissive nucleoside 2 displays significantly higher emission intensity than the free nucleoside. Furthermore, photophysical characterisation shows that the fluorescence properties of the nucleoside analogue within ONs are significantly influenced by flanking bases, especially by guanosine. By utilising the responsiveness of the nucleoside to changes in base environment, a DNA ON reporter labelled with the emissive nucleoside 2 was constructed; this signalled the presence of an abasic site in a model depurinated sarcin/ricin RNA motif of a eukaryotic 28S rRNA.
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Affiliation(s)
- Arun A Tanpure
- Department of Chemistry, Indian Institute of Science Education and Research, 900, NCL Innovation Park, Dr. Homi Bhabha Road, Pune 411008, India
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27
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Noé MS, Ríos AC, Tor Y. Design, synthesis, and spectroscopic properties of extended and fused pyrrolo-dC and pyrrolo-C analogs. Org Lett 2012; 14:3150-3. [PMID: 22646728 PMCID: PMC3426657 DOI: 10.1021/ol3012327] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The syntheses of four fluorescent nucleoside analogs, related to pyrrolo-C (PyC) and pyrrolo-dC (PydC) through the conjugation or fusion of a thiophene moiety, are described. A thorough photophysical analysis of the nucleosides, in comparison to PyC, is reported.
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Affiliation(s)
- Mary S Noé
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA
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28
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Kuznetsov NA, Vorobjev YN, Krasnoperov LN, Fedorova OS. Thermodynamics of the multi-stage DNA lesion recognition and repair by formamidopyrimidine-DNA glycosylase using pyrrolocytosine fluorescence--stopped-flow pre-steady-state kinetics. Nucleic Acids Res 2012; 40:7384-92. [PMID: 22584623 PMCID: PMC3424566 DOI: 10.1093/nar/gks423] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Formamidopyrimidine-DNA glycosylase, Fpg protein from Escherichia coli, initiates base excision repair in DNA by removing a wide variety of oxidized lesions. In this study, we perform thermodynamic analysis of the multi-stage interaction of Fpg with specific DNA-substrates containing 7,8-dihydro-8-oxoguanosine (oxoG), or tetrahydrofuran (THF, an uncleavable abasic site analog) and non-specific (G) DNA-ligand based on stopped-flow kinetic data. Pyrrolocytosine, highly fluorescent analog of the natural nucleobase cytosine, is used to record multi-stage DNA lesion recognition and repair kinetics over a temperature range (10–30°C). The kinetic data were used to obtain the standard Gibbs energy, enthalpy and entropy of the specific stages using van’t Hoff approach. The data suggest that not only enthalpy-driven exothermic oxoG recognition, but also the desolvation-accompanied entropy-driven enzyme-substrate complex adjustment into the catalytically active state play equally important roles in the overall process.
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Affiliation(s)
- Nikita A Kuznetsov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia
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29
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Sukackaite R, Grazulis S, Tamulaitis G, Siksnys V. The recognition domain of the methyl-specific endonuclease McrBC flips out 5-methylcytosine. Nucleic Acids Res 2012; 40:7552-62. [PMID: 22570415 PMCID: PMC3424535 DOI: 10.1093/nar/gks332] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
DNA cytosine methylation is a widespread epigenetic mark. Biological effects of DNA methylation are mediated by the proteins that preferentially bind to 5-methylcytosine (5mC) in different sequence contexts. Until now two different structural mechanisms have been established for 5mC recognition in eukaryotes; however, it is still unknown how discrimination of the 5mC modification is achieved in prokaryotes. Here we report the crystal structure of the N-terminal DNA-binding domain (McrB-N) of the methyl-specific endonuclease McrBC from Escherichia coli. The McrB-N protein shows a novel DNA-binding fold adapted for 5mC-recognition. In the McrB-N structure in complex with methylated DNA, the 5mC base is flipped out from the DNA duplex and positioned within a binding pocket. Base flipping elegantly explains why McrBC system restricts only T4-even phages impaired in glycosylation [Luria, S.E. and Human, M.L. (1952) A nonhereditary, host-induced variation of bacterial viruses. J. Bacteriol., 64, 557–569]: flipped out 5-hydroxymethylcytosine is accommodated in the binding pocket but there is no room for the glycosylated base. The mechanism for 5mC recognition employed by McrB-N is highly reminiscent of that for eukaryotic SRA domains, despite the differences in their protein folds.
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Affiliation(s)
- Rasa Sukackaite
- Department of Protein-DNA Interactions, Institute of Biotechnology, Vilnius University, Graiciuno 8, 02241 Vilnius, Lithuania
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30
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Coppock MB, Williams ME. Nucleic Acid Mimetics. Supramol Chem 2012. [DOI: 10.1002/9780470661345.smc169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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31
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Huang W, Kim J, Jha S, Aboul-Ela F. Conformational heterogeneity of the SAM-I riboswitch transcriptional ON state: a chaperone-like role for S-adenosyl methionine. J Mol Biol 2012; 418:331-49. [PMID: 22425639 DOI: 10.1016/j.jmb.2012.02.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 02/09/2012] [Accepted: 02/15/2012] [Indexed: 10/28/2022]
Abstract
Riboswitches are promising targets for the design of novel antibiotics and engineering of portable genetic regulatory elements. There is evidence that variability in riboswitch properties allows tuning of expression for genes involved in different stages of biosynthetic pathways by mechanisms that are not currently understood. Here, we explore the mechanism for tuning of S-adenosyl methionine (SAM)-I riboswitch folding. Most SAM-I riboswitches function at the transcriptional level by sensing the cognate ligand SAM. SAM-I riboswitches orchestrate the biosynthetic pathways of cysteine, methionine, SAM, and so forth. We use base-pair probability predictions to examine the secondary-structure folding landscape of several SAM-I riboswitch sequences. We predict different folding behaviors for different SAM-I riboswitch sequences. We identify several "decoy" base-pairing interactions involving 5' riboswitch residues that can compete with the formation of a P1 helix, a component of the ligand-bound "transcription OFF" state, in the absence of SAM. We hypothesize that blockage of these interactions through SAM contacts contributes to stabilization of the OFF state in the presence of ligand. We also probe folding patterns for a SAM-I riboswitch RNA using constructs with different 3' truncation points experimentally. Folding was monitored through fluorescence, susceptibility to base-catalyzed cleavage, nuclear magnetic resonance, and indirectly through SAM binding. We identify key decision windows at which SAM can affect the folding pathway towards the OFF state. The presence of decoy conformations and differential sensitivities to SAM at different transcript lengths is crucial for SAM-I riboswitches to modulate gene expression in the context of global cellular metabolism.
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Affiliation(s)
- Wei Huang
- Department of Biological Science, Louisiana State University, Baton Rouge, LA 70803, USA
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32
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Buskiewicz IA, Burke JM. Folding of the hammerhead ribozyme: pyrrolo-cytosine fluorescence separates core folding from global folding and reveals a pH-dependent conformational change. RNA (NEW YORK, N.Y.) 2012; 18:434-448. [PMID: 22274955 PMCID: PMC3285932 DOI: 10.1261/rna.030999.111] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 11/09/2011] [Indexed: 05/30/2023]
Abstract
The catalytic activity of the hammerhead ribozyme is limited by its ability to fold into the native tertiary structure. Analysis of folding has been hampered by a lack of assays that can independently monitor the environment of nucleobases throughout the ribozyme-substrate complex in real time. Here, we report the development and application of a new folding assay in which we use pyrrolo-cytosine (pyC) fluorescence to (1) probe active-site formation, (2) examine the ability of peripheral ribozyme domains to support native folding, (3) identify a pH-dependent conformational change within the ribozyme, and (4) explore its influence on the equilibrium between the folded and unfolded core of the hammerhead ribozyme. We conclude that the natural ribozyme folds in two distinct noncooperative steps and the pH-dependent correlation between core folding and activity is linked to formation of the G8-C3 base pair.
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Affiliation(s)
- Iwona A Buskiewicz
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA.
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33
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Tanpure AA, Srivatsan SG. A microenvironment-sensitive fluorescent pyrimidine ribonucleoside analogue: synthesis, enzymatic incorporation, and fluorescence detection of a DNA abasic site. Chemistry 2011; 17:12820-7. [PMID: 21956450 DOI: 10.1002/chem.201101194] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 07/18/2011] [Indexed: 11/10/2022]
Abstract
Base-modified fluorescent ribonucleoside-analogue probes are valuable tools in monitoring RNA structure and function because they closely resemble the structure of natural nucleobases. Especially, 2-aminopurine, a highly environment-sensitive adenosine analogue, is the most extensively utilized fluorescent nucleoside analogue. However, only a few isosteric pyrimidine ribonucleoside analogues that are suitable for probing the structure and recognition properties of RNA molecules are available. Herein, we describe the synthesis and photophysical characterization of a small series of base-modified pyrimidine ribonucleoside analogues derived from tagging indole, N-methylindole, and benzofuran onto the 5-position of uracil. One of the analogues, based on a 5-(benzofuran-2-yl)pyrimidine core, shows emission in the visible region with a reasonable quantum yield and, importantly, displays excellent solvatochromism. The corresponding triphosphate substrate is effectively incorporated into oligoribonucleotides by T7 RNA polymerase to produce fluorescent oligoribonucleotide constructs. Steady-state and time-resolved spectroscopic studies with fluorescent oligoribonucleotide constructs demonstrate that the fluorescent ribonucleoside photophysically responds to subtle changes in its environment brought about by the interaction of the chromophore with neighboring bases. In particular, the emissive ribonucleoside, if incorporated into an oligoribonucleotide, positively reports the presence of a DNA abasic site with an appreciable enhancement in fluorescence intensity. The straightforward synthesis, amicability to enzymatic incorporation, and sensitivity to changes in the microenvironment highlight the potential of the benzofuran-conjugated pyrimidine ribonucleoside as an efficient fluorescent probe to investigate nucleic acid structure, dynamics, and recognition events.
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Affiliation(s)
- Arun A Tanpure
- Department of Chemistry, Indian Institute of Science Education and Research, Pashan, Pune, India
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Pawar MG, Srivatsan SG. Synthesis, photophysical characterization, and enzymatic incorporation of a microenvironment-sensitive fluorescent uridine analog. Org Lett 2011; 13:1114-7. [PMID: 21275418 DOI: 10.1021/ol103147t] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The synthesis of a microenvironment-sensitive base-modified fluorescent ribonucleoside analog based on a 5-(benzo[b]thiophen-2-yl)pyrimidine core, enzymatic incorporation of its corresponding triphosphate into RNA oligonucleotides, and photophysical characterization of fluorescently modified oligoribonucleotides are described.
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Affiliation(s)
- Maroti G Pawar
- Indian Institute of Science Education and Research, Pashan, Pune, India
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Greco NJ, Sinkeldam RW, Tor Y. An emissive C analog distinguishes between G, 8-oxoG, and T. Org Lett 2010; 11:1115-8. [PMID: 19196162 DOI: 10.1021/ol802656n] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A minimally disruptive fluorescent dC analog provides a rapid and non-destructive method for in vitro detection of G, 8-oxoG, and T, the downstream transverse mutation product.
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Affiliation(s)
- Nicholas J Greco
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA
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Narayanan M, Kodali G, Singh V, Xing Y, Hawkins ME, Stanley RJ. Differential fluorescence quenching of fluorescent nucleic acid base analogues by native nucleic acid monophosphates. J Phys Chem B 2010; 114:5953-63. [PMID: 20387838 DOI: 10.1021/jp1011507] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fluorescent nucleic acid base analogues (FBAs) are used widely as probes of DNA and RNA structure and dynamics. Of increasing utility are the pteridone adenosine analogues (6MAP, DMAP) and pteridine guanosine analogues (3MI, 6MI). These FBAs (collectively referred to as PTERs) are useful, in part, because their fluorescence quantum yields, Phi(f), are modulated by base stacking with native bases (NBs), making them sensitive reporters of DNA structure. The quenching mechanism has been hypothesized to be photoinduced electron transfer following selective excitation of the FBA, but hard evidence for this has been lacking. The degree of quenching shows some dependence on the neighboring bases, but there has been no real determination as to whether FBA*:NB complexes satisfy the basic thermodynamic requirement for spontaneous PET: a negative free energy for the electron transfer reaction. Indeed, quenching may result from entirely different mechanisms. To address these questions, Stern-Volmer (S-V) experiments were performed using the native-base monophosphate nucleotides (NMPs) GMP, AMP, CMP, and dTMP in aqueous solutions as quenchers to obtain quenching rate constants, k(q). Cyclic voltammetry (CV) and optical absorption and emission data of the PTERS were obtained in aprotic organic solvents. These data were used to obtain excited-state redox potentials from which electron transfer free energies were derived using the Rehm-Weller equation. The reorganization energies for PET were obtained using the Scandola-Balzani equation, taking into account the free energy contribution due to water. 6MAP*, DMAP*, and 3MI* gave negative free energies between -0.1 and -0.2 eV and reorganization energies of about 0.13 eV. They all displayed ET activation energies below the accessible thermal energy (0.038 eV = 3/2k(B)T, where k(B) is Boltzmann's constant) for all NMPs with the exception of CMP, whose activation barrier was only about 35% higher (approximately 0.05 eV). Thus, we conclude that these PTERs act as electron acceptors and promote NMP oxidation. However, 6MI* had positive ET free energies for all NMPs with the exception of GMP (and then only for nucleobase oxidation). The magnitudes of these free energies (> or = 0.45 eV for AMP, CMP, and dTMP) suggest that 6MI* may not quenched by PET.
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Affiliation(s)
- Madhavan Narayanan
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
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Ohkubo A, Sakaue T, Tsunoda H, Seio K, Sekine M. Synthesis and Hybridization Properties of Oligonucleotides Incorporating Bi- and Tricyclic Cytosine Derivatives. CHEM LETT 2010. [DOI: 10.1246/cl.2010.726] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Wachowius F, Höbartner C. Chemical RNA modifications for studies of RNA structure and dynamics. Chembiochem 2010; 11:469-80. [PMID: 20135663 DOI: 10.1002/cbic.200900697] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Falk Wachowius
- Research Group Nucleic Acid Chemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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Abstract
The use of fluorescent nucleic acid base analogues is becoming increasingly important in the fields of biology, biochemistry and biophysical chemistry as well as in the field of DNA nanotechnology. The advantage of being able to incorporate a fluorescent probe molecule close to the site of examination in the nucleic acid-containing system of interest with merely a minimal perturbation to the natural structure makes fluorescent base analogues highly attractive. In recent years, there has been a growing interest in developing novel candidates in this group of fluorophores for utilization in various investigations. This review describes the different classes of fluorophores that can be used for studying nucleic acid-containing systems, with an emphasis on choosing the right kind of probe for the system under investigation. It describes the characteristics of the large group of base analogues that has an emission that is sensitive to the surrounding microenvironment and gives examples of investigations in which this group of molecules has been used so far. Furthermore, the characterization and use of fluorescent base analogues that are virtually insensitive to changes in their microenvironment are described in detail. This group of base analogues can be used in several fluorescence investigations of nucleic acids, especially in fluorescence anisotropy and fluorescence resonance energy transfer (FRET) measurements. Finally, the development and characterization of the first nucleic base analogue FRET pair, tC(O)-tC(nitro), and its possible future uses are discussed.
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Sinkeldam RW, Greco NJ, Tor Y. Fluorescent analogs of biomolecular building blocks: design, properties, and applications. Chem Rev 2010; 110:2579-619. [PMID: 20205430 PMCID: PMC2868948 DOI: 10.1021/cr900301e] [Citation(s) in RCA: 665] [Impact Index Per Article: 47.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Renatus W. Sinkeldam
- Department of Chemistry and Biochemistry, University of California, San Diego 9500 Gilman Drive, La Jolla, California 92093-0358
| | | | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of California, San Diego 9500 Gilman Drive, La Jolla, California 92093-0358
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Li T, Fu R, Park HG. Pyrrolo-dC based fluorescent aptasensors for the molecular recognition of targets. Chem Commun (Camb) 2010; 46:3271-3. [PMID: 20442883 DOI: 10.1039/b923462d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Novel signal-on fluorescent aptasensors based on unlabeled aptamers and pyrrolo-dC have been developed for the detection of several targets with great specificity and sensitivity.
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Affiliation(s)
- Taihua Li
- Department of Chemical and Biomolecular Engineering, KAIST, 335 Gwahak-ro, Yuseong-gu, Daejeon, 305-701, Republic of Korea
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Wahba AS, Esmaeili A, Damha MJ, Hudson RHE. A single-label phenylpyrrolocytidine provides a molecular beacon-like response reporting HIV-1 RT RNase H activity. Nucleic Acids Res 2010; 38:1048-56. [PMID: 19933258 PMCID: PMC2817455 DOI: 10.1093/nar/gkp1022] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2009] [Revised: 10/19/2009] [Accepted: 10/19/2009] [Indexed: 12/12/2022] Open
Abstract
6-Phenylpyrrolocytidine (PhpC), a structurally conservative and highly fluorescent cytidine analog, was incorporated into oligoribonucleotides. The PhpC-containing RNA formed native-like duplex structures with complementary DNA or RNA. The PhpC-modification was found to act as a sensitive reporter group being non-disruptive to structure and the enzymatic activity of RNase H. A RNA/DNA hybrid possessing a single PhpC insert was an excellent substrate for HIV-1 RT Ribonuclease H and rapidly reported cleavage of the RNA strand with a 14-fold increase in fluorescence intensity. The PhpC-based assay for RNase H was superior to the traditional molecular beacon approach in terms of responsiveness, rapidity and ease (single label versus dual). Furthermore, the PhpC-based assay is amenable to high-throughput microplate assay format and may form the basis for a new screen for inhibitors of HIV-RT RNase H.
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Affiliation(s)
- Alexander S. Wahba
- Department of Chemistry, McGill University, Montreal, QC, H3A 2K6 Canada, Department of Chemistry, University of Birjand, Birjand, Iran and Department of Chemistry, University of Western Ontario, London, ON, N6A 5B7 Canada
| | - Abbasali Esmaeili
- Department of Chemistry, McGill University, Montreal, QC, H3A 2K6 Canada, Department of Chemistry, University of Birjand, Birjand, Iran and Department of Chemistry, University of Western Ontario, London, ON, N6A 5B7 Canada
| | - Masad J. Damha
- Department of Chemistry, McGill University, Montreal, QC, H3A 2K6 Canada, Department of Chemistry, University of Birjand, Birjand, Iran and Department of Chemistry, University of Western Ontario, London, ON, N6A 5B7 Canada
| | - Robert H. E. Hudson
- Department of Chemistry, McGill University, Montreal, QC, H3A 2K6 Canada, Department of Chemistry, University of Birjand, Birjand, Iran and Department of Chemistry, University of Western Ontario, London, ON, N6A 5B7 Canada
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Kodali G, Kistler KA, Narayanan M, Matsika S, Stanley RJ. Change in Electronic Structure upon Optical Excitation of 8-Vinyladenosine: An Experimental and Theoretical Study. J Phys Chem A 2009; 114:256-67. [DOI: 10.1021/jp908055h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Goutham Kodali
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Kurt A. Kistler
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Madhavan Narayanan
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Spiridoula Matsika
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Robert J. Stanley
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
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Mizuta M, Seio K, Ohkubo A, Sekine M. Fluorescence properties of pyrimidopyrimidoindole nucleoside dC(PPI) incorporated into oligodeoxynucleotides. J Phys Chem B 2009; 113:9562-9. [PMID: 19537698 DOI: 10.1021/jp807562c] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of oligodeoxynucleotides labeled by a pyrimidopyrimidoindole deoxynucleoside (1a: dC(PPI)) and its derivatives 2a and 3a substituted with electron-donating and -withdrawing groups, respectively, were synthesized according to the phosphoramidite approach. The photophysical properties and quenching efficiencies of oligonucleotides incorporating dC(PPI) derivatives were studied in detail. The thermal denaturation experiments and molecular dynamics simulation of DNA duplexes incorporating dC(PPI) suggested that a modified base of dC(PPI) could form base pairs with guanine and adenine in canonical Watson-Crick and reverse-wobble geometries, respectively. The fluorescence of oligonucleotides incorporating dC(PPI) derivatives increased upon binding to the counter strands, except when dC(PPI) and guanine formed a base pair. It was revealed that dGMP quenched the fluorescence of the cyano derivative 3a most effectively, whereas it affected that of the methoxy derivative 2a least effectively. The involvement of the electron transfer from guanine to the dC(PPI) derivatives in the fluorescence quenching was supported by energy considerations.
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Affiliation(s)
- Masahiro Mizuta
- Department of Life Science, Tokyo Institute of Technology, Nagatsuta, Midoriku, Yokohama 226-8501, Japan
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Lee HW, Briggs KT, Marino JP. Dissecting structural transitions in the HIV-1 dimerization initiation site RNA using 2-aminopurine fluorescence. Methods 2009; 49:118-27. [PMID: 19460437 DOI: 10.1016/j.ymeth.2009.05.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Revised: 05/08/2009] [Accepted: 05/12/2009] [Indexed: 10/20/2022] Open
Abstract
A highly conserved 35 nucleotide RNA stem-loop, the dimerization initiation site (DIS), in the 5' untranslated region (UTR) of the human immunodeficiency virus type I (HIV-1) genome has been identified as the sequence primarily responsible for initiation of viral genome dimerization. The DIS initiates viral genome dimerization through a loop-loop 'kissing' interaction and is converted from an intermediate 'kissing' to a more thermodynamically stable extended duplex dimer in a conformational rearrangement that is chaperoned by the HIV-1 nucleocapsid protein (NCp7). Here we describe fluorescence methods designed to probe local RNA dynamics and structural transitions associated with the DIS dimer formation and its NCp7 chaperoned structural conversion. These methods take advantage of the exquisite sensitivity of the quantum yield of the fluorescent nucleotide base analog, 2-aminopurine (2-AP), to its immediate structural and dynamic environment. The 2-AP fluorescence methods described allow a detailed kinetic and thermodynamic examination of this type of RNA-RNA interaction, as well as an analysis of the molecular mechanism of NCp7 chaperone activity.
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Affiliation(s)
- Hui-Wen Lee
- Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, The National Institute of Standards and Technology, Rockville, MD 20850, USA
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Abstract
Transfer RNA (tRNA) molecules mediate translation of the nucleic acid genetic code into the amino acid building blocks of proteins, thus ensuring the survivability of cells. The dynamic properties of tRNA molecules are crucial to their functions in both activity and specificity. This chapter summarizes two methods that have been recently developed or improved upon previous protocols to introduce fluorophores to site-specific positions in tRNA. One method enables incorporation of fluorophores carrying a primary amine (such as proflavin or rhodamine) to dihydrouridine (D) residues in the tRNA tertiary core, and a second method enables incorporation of pyrroloC and 2-aminopurine to positions 75 and 76, respectively, of the CCA sequence at the 3' end. These site-specific fluorophore labeling methods utilize tRNA transcripts as the substrates to provide the versatility with both wild-type and mutant sequences for examining their motions in space and time during the process of decoding genetic information.
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Affiliation(s)
- Cuiping Liu
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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Zhao Y, Knee JL, Baranger AM. Characterization of two adenosine analogs as fluorescence probes in RNA. Bioorg Chem 2008; 36:271-7. [PMID: 18707751 PMCID: PMC2661016 DOI: 10.1016/j.bioorg.2008.06.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 06/10/2008] [Accepted: 06/12/2008] [Indexed: 11/22/2022]
Abstract
The fluorescence properties of two adenosine analogs, 2-(3-phenylpropyl)adenosine [A-3CPh] and 2-(4-phenylbutyl)adenosine [A-4CPh], are reported. As monomers, the quantum yields and the mean lifetimes are 0.011 and 6.22 ns for A-3CPh and 0.007 and 7.13 ns for A-4CPh, respectively. Surprisingly, the quantum yields of the two probes are enhanced 11- to 82-fold upon incorporation into RNA, while the mean lifetimes decrease 23-40%. The data suggest that a subpopulation of molecules is responsible for the fluorescence characteristics and that the distribution of emitting and non-emitting structures is altered upon incorporation of the probes into RNA. Thus, although both adenosine analogs have low quantum yields as monomers, their fluorescence signals are significantly enhanced in RNA. Thermodenaturation experiments and CD spectroscopy indicate that incorporation of the adenosine analogs into three different RNAs does not alter their global structure or stability. Therefore, these probes should be useful for probing events occurring close to the site of modification.
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Affiliation(s)
- Ying Zhao
- Department of Chemistry, Wesleyan University, Middletown, CT 06459
| | - Joseph L. Knee
- Department of Chemistry, Wesleyan University, Middletown, CT 06459
| | - Anne M. Baranger
- Department of Chemistry, Wesleyan University, Middletown, CT 06459
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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Zhang CM, Liu C, Christian T, Gamper H, Rozenski J, Pan D, Randolph JB, Wickstrom E, Cooperman BS, Hou YM. Pyrrolo-C as a molecular probe for monitoring conformations of the tRNA 3' end. RNA (NEW YORK, N.Y.) 2008; 14:2245-2253. [PMID: 18755841 PMCID: PMC2553749 DOI: 10.1261/rna.1158508] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 07/15/2008] [Indexed: 05/26/2023]
Abstract
All mature tRNA molecules have the conserved CCA sequence at the 3' end with a range of dynamic conformations that are important for tRNA functions. We present here the details of a general approach to fluorescent labeling of the CCA sequence with the fluorescent base analog pyrrolo-C (PyC) at position 75 as a molecular probe for monitoring the dynamics of the tRNA 3' end. Using Escherichia coli tRNA(Cys) as an example, we achieve such labeling by first synthesizing the tRNA as a transcript up to C74 and then employing the tRNA CCA-adding enzyme to incorporate PyC75 and A76, using pyrrolo-CTP (PyCTP) and ATP as the respective substrates. PyC-labeled full-length tRNA(Cys), separated from the unlabeled precursor tRNA by reverse phase high-pressure liquid chromatography, is an efficient substrate for aminoacylation by E. coli cysteinyl-tRNA synthetase (CysRS). Fluorescence binding measurement of the PyC-labeled tRNA(Cys) with E. coli CysRS reveals an equilibrium K(d) closely similar to the value determined from the fluorescence of intrinsic enzyme tryptophans. Kinetic measurements of translocation of the PyC-labeled tRNA from the ribosomal A to P sites identify a kinetic intermediate with a rate of formation and decay similar to the values reported for tRNAs labeled with the fluorescent proflavin at the tertiary core. These results highlight the potential of PyC to probe the dynamics of the tRNA CCA end in reactions ranging from aminoacylation to those on the ribosome.
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Affiliation(s)
- Chun-Mei Zhang
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Cekan P, Smith AL, Barhate N, Robinson BH, Sigurdsson ST. Rigid spin-labeled nucleoside C: a nonperturbing EPR probe of nucleic acid conformation. Nucleic Acids Res 2008; 36:5946-54. [PMID: 18805908 PMCID: PMC2566876 DOI: 10.1093/nar/gkn562] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Rigid spin-labeled nucleoside C, an analog of deoxycytidine that base-pairs with deoxyguanosine, was incorporated into DNA oligomers by chemical synthesis. Thermal denaturation experiments and circular dichroism (CD) measurements showed that C has a negligible effect on DNA duplex stability and conformation. Nucleoside C was incorporated into several positions within single-stranded DNA oligomers that can adopt two hairpin conformations of similar energy, each of which contains a four-base loop. The relative mobility of nucleotides in the alternating C/G hairpin loops, 5'-d(GCGC) and 5'-d(CGCG), was determined by electron paramagnetic resonance (EPR) spectroscopy. The most mobile nucleotide in the loop is the second one from the 5'-end, followed by the third, first and fourth nucleotides, consistent with previous NMR studies of DNA hairpin loops of different sequences. The EPR hairpin data were also corroborated by fluorescence spectroscopy using oligomers containing reduced C (C(f)), which is fluorescent. Furthermore, EPR spectra of duplex DNAs that contained C at the end of the helix showed features that indicated dipolar coupling between two spins. These data are consistent with end-to-end duplex stacking in solution, which was only observed when G was paired to C, but not when C was paired with A, C or T.
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Affiliation(s)
- Pavol Cekan
- University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
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Wojciechowski F, Hudson RHE. Fluorescence and hybridization properties of peptide nucleic acid containing a substituted phenylpyrrolocytosine designed to engage Guanine with an additional H-bond. J Am Chem Soc 2008; 130:12574-5. [PMID: 18761442 DOI: 10.1021/ja804233g] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new pyrrolocytosine derivative has been designed to selectively interact with guanine and has been evaluated in peptide nucleic acid where it imparts increased selective binding affinity for complementary oligonucleotides. The modified nucleobase also possesses an exceptionally high fluorescence quantum yield that is responsive to hybridization.
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Affiliation(s)
- Filip Wojciechowski
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada, N6A 5B7
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