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Das G, Harikrishna S, Gore KR. Influence of Sugar Modifications on the Nucleoside Conformation and Oligonucleotide Stability: A Critical Review. CHEM REC 2022; 22:e202200174. [PMID: 36048010 DOI: 10.1002/tcr.202200174] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/16/2022] [Indexed: 12/15/2022]
Abstract
Ribofuranose sugar conformation plays an important role in the structure and dynamics of functional nucleic acids such as siRNAs, AONs, aptamers, miRNAs, etc. To improve their therapeutic potential, several chemical modifications have been introduced into the sugar moiety over the years. The stability of the oligonucleotide duplexes as well as the formation of stable and functional protein-oligonucleotide complexes are dictated by the conformation and dynamics of the sugar moiety. In this review, we systematically categorise various ribofuranose sugar modifications employed in DNAs and RNAs so far. We discuss different stereoelectronic effects imparted by different substituents on the sugar ring and how these effects control sugar puckering. Using this data, it would be possible to predict the precise use of chemical modifications and design novel sugar-modified nucleosides for therapeutic oligonucleotides that can improve their physicochemical properties.
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Affiliation(s)
- Gourav Das
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal-721302, India
| | - S Harikrishna
- Department of Chemistry and Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Kiran R Gore
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal-721302, India
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2
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Hardwick JS, Haugland MM, El-Sagheer AH, Ptchelkine D, Beierlein FR, Lane AN, Brown T, Lovett JE, Anderson EA. 2'-Alkynyl spin-labelling is a minimally perturbing tool for DNA structural analysis. Nucleic Acids Res 2020; 48:2830-2840. [PMID: 32052020 PMCID: PMC7102949 DOI: 10.1093/nar/gkaa086] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 01/28/2020] [Accepted: 02/10/2020] [Indexed: 02/06/2023] Open
Abstract
The determination of distances between specific points in nucleic acids is essential to understanding their behaviour at the molecular level. The ability to measure distances of 2-10 nm is particularly important: deformations arising from protein binding commonly fall within this range, but the reliable measurement of such distances for a conformational ensemble remains a significant challenge. Using several techniques, we show that electron paramagnetic resonance (EPR) spectroscopy of oligonucleotides spin-labelled with triazole-appended nitroxides at the 2' position offers a robust and minimally perturbing tool for obtaining such measurements. For two nitroxides, we present results from EPR spectroscopy, X-ray crystal structures of B-form spin-labelled DNA duplexes, molecular dynamics simulations and nuclear magnetic resonance spectroscopy. These four methods are mutually supportive, and pinpoint the locations of the spin labels on the duplexes. In doing so, this work establishes 2'-alkynyl nitroxide spin-labelling as a minimally perturbing method for probing DNA conformation.
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Affiliation(s)
- Jack S Hardwick
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Marius M Haugland
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Afaf H El-Sagheer
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
- Chemistry Branch, Department of Science and Mathematics, Faculty of Petroleum and Mining Engineering, Suez University, Suez 43721, Egypt
| | - Denis Ptchelkine
- Weatherall Institute of Molecular Medicine, Department of Oncology, University of Oxford, John Radcliffe Hospital, Headley Way, Oxford OX3 9DS, UK
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, OX11 0FA, UK
| | - Frank R Beierlein
- Computer-Chemistry-Center and Interdisciplinary Center for Molecular Materials, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstrasse 25, 91052 Erlangen, Germany
| | - Andrew N Lane
- Center for Environmental and Systems Biochemistry and Department of Toxicology & Cancer Biology, The University of Kentucky, 789 S. Limestone St., Lexington, KY 40536, USA
| | - Tom Brown
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Janet E Lovett
- SUPA School of Physics and Astronomy and BSRC, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
| | - Edward A Anderson
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
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3
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Conlon PF, Eguaogie O, Wilson JJ, Sweet JST, Steinhoegl J, Englert K, Hancox OGA, Law CJ, Allman SA, Tucker JHR, Hall JP, Vyle JS. Solid-phase synthesis and structural characterisation of phosphoroselenolate-modified DNA: a backbone analogue which does not impose conformational bias and facilitates SAD X-ray crystallography. Chem Sci 2019; 10:10948-10957. [PMID: 32190252 PMCID: PMC7066676 DOI: 10.1039/c9sc04098f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 10/11/2019] [Indexed: 01/20/2023] Open
Abstract
Oligodeoxynucleotides incorporating internucleotide phosphoroselenolate linkages have been prepared under solid-phase synthesis conditions using dimer phosphoramidites. These dimers were constructed following the high yielding Michaelis-Arbuzov (M-A) reaction of nucleoside H-phosphonate derivatives with 5'-deoxythymidine-5'-selenocyanate and subsequent phosphitylation. Efficient coupling of the dimer phosphoramidites to solid-supported substrates was observed under both manual and automated conditions and required only minor modifications to the standard DNA synthesis cycle. In a further demonstration of the utility of M-A chemistry, the support-bound selenonucleoside was reacted with an H-phosphonate and then chain extended using phosphoramidite chemistry. Following initial unmasking of methyl-protected phosphoroselenolate diesters, pure oligodeoxynucleotides were isolated using standard deprotection and purification procedures and subsequently characterised by mass spectrometry and circular dichroism. The CD spectra of both modified and native duplexes derived from self-complementary sequences with A-form, B-form or mixed conformational preferences were essentially superimposable. These sequences were also used to study the effect of the modification upon duplex stability which showed context-dependent destabilisation (-0.4 to -3.1 °C per phosphoroselenolate) when introduced at the 5'-termini of A-form or mixed duplexes or at juxtaposed central loci within a B-form duplex (-1.0 °C per modification). As found with other nucleic acids incorporating selenium, expeditious crystallisation of a modified decanucleotide A-form duplex was observed and the structure solved to a resolution of 1.45 Å. The DNA structure adjacent to the modification was not significantly perturbed. The phosphoroselenolate linkage was found to impart resistance to nuclease activity.
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Affiliation(s)
- Patrick F Conlon
- School of Chemistry and Chemical Engineering , Queen's University Belfast , David Keir Building, Stranmillis Road , Belfast , BT9 5AG , UK .
| | - Olga Eguaogie
- School of Chemistry and Chemical Engineering , Queen's University Belfast , David Keir Building, Stranmillis Road , Belfast , BT9 5AG , UK .
| | - Jordan J Wilson
- School of Chemistry and Chemical Engineering , Queen's University Belfast , David Keir Building, Stranmillis Road , Belfast , BT9 5AG , UK .
| | - Jamie S T Sweet
- School of Chemistry and Chemical Engineering , Queen's University Belfast , David Keir Building, Stranmillis Road , Belfast , BT9 5AG , UK .
| | - Julian Steinhoegl
- Reading School of Pharmacy , University of Reading , Whiteknights , Reading RG6 6AP , UK .
| | - Klaudia Englert
- School of Chemistry , University of Birmingham , Edgbaston , Birmingham B15 2TT , UK
| | - Oliver G A Hancox
- Reading School of Pharmacy , University of Reading , Whiteknights , Reading RG6 6AP , UK .
| | - Christopher J Law
- School of Biological Sciences , Queen's University Belfast , 15 Chlorine Gardens , Belfast BT9 5AH , UK
| | - Sarah A Allman
- Reading School of Pharmacy , University of Reading , Whiteknights , Reading RG6 6AP , UK .
| | - James H R Tucker
- School of Chemistry , University of Birmingham , Edgbaston , Birmingham B15 2TT , UK
| | - James P Hall
- Reading School of Pharmacy , University of Reading , Whiteknights , Reading RG6 6AP , UK .
- Diamond Light Source , Chilton , Didcot , Oxfordshire OX11 0DE , UK
| | - Joseph S Vyle
- School of Chemistry and Chemical Engineering , Queen's University Belfast , David Keir Building, Stranmillis Road , Belfast , BT9 5AG , UK .
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4
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Phosphorus SAD Phasing for Nucleic Acid Structures: Limitations and Potential. CRYSTALS 2016. [DOI: 10.3390/cryst6100125] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Generating Crystallographic Models of DNA Dodecamers from Structures of RNase H:DNA Complexes. Methods Mol Biol 2016; 1320:111-26. [PMID: 26227040 DOI: 10.1007/978-1-4939-2763-0_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The DNA dodecamer 5'-d(CGCGAATTCGCG)-3' is arguably the best studied oligonucleotide and crystal structures of duplexes with this sequence account for a considerable portion of the total number of oligo-2'-deoxynucleotide structures determined over the last 30 years. The dodecamer has commonly served as a template to analyze the effects of sequence on DNA conformation, the conformational properties of chemically modified nucleotides, DNA-ligand interactions as well as water structure and DNA-cation binding. Although molecular replacement is the phasing method of choice given the large number of available models of the dodecamer, this strategy often fails as a result of conformational changes caused by chemical modification, mismatch pairs, or differing packing modes. Here, we describe an alternative approach to determine crystal structures of the dodecamer in cases where molecular replacement does not produce a solution or when crystals of the DNA alone cannot be grown. It is based on the discovery that many dodecamers of the above sequence can be readily co-crystallized with Bacillus halodurans RNase H, whereby the enzyme is unable to cleave the DNA. Determination of the structure of the complex using the protein portion as the search model yields a structural model of the DNA. Provided crystals of the DNA alone are also available, the DNA model from the complex then enables phasing their structures by molecular replacement.
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Anderson BA, Hrdlicka PJ. Synthesis and characterization of oligodeoxyribonucleotides modified with 2'-thio-2'-deoxy-2'-S-(pyren-1-yl)methyluridine. Bioorg Med Chem Lett 2015; 25:3999-4004. [PMID: 26254942 PMCID: PMC4540677 DOI: 10.1016/j.bmcl.2015.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 06/30/2015] [Accepted: 07/02/2015] [Indexed: 01/11/2023]
Abstract
Pyrene-functionalized oligonucleotides are intensively explored for applications in materials science and diagnostics. Here, we describe a short synthetic route to 2'-S-(pyren-1-yl)methyl-2'-thiouridine monomer S, its incorporation into oligodeoxyribonucleotides (ONs), and biophysical characterization thereof. Pseudorotational analysis reveals that the furanose ring of this monomer has a slight preference for South-type conformations. ONs modified with monomer S display high cDNA affinity but decreased binding specificity. Hybridization is associated with bathochromic shifts of pyrene absorption bands and quenching of pyrene fluorescence consistent with an intercalative binding mode of the pyrene moiety. Monomer S was also evaluated as a building block for mixed-sequence recognition of double-stranded DNA via the Invader strategy. However, probes with +1 interstrand arrangements of monomer S were found to be less efficient than Invader probes based on 2'-O-(pyren-1-yl)methyluridine or 2'-N-(pyren-1-yl)methyl-2'-N-methyl-2'-aminouridine.
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Affiliation(s)
- Brooke A Anderson
- Department of Chemistry, University of Idaho, Moscow, ID 83844-2343, United States
| | - Patrick J Hrdlicka
- Department of Chemistry, University of Idaho, Moscow, ID 83844-2343, United States.
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7
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Košutić M, Jud L, Da Veiga C, Frener M, Fauster K, Kreutz C, Ennifar E, Micura R. Surprising base pairing and structural properties of 2'-trifluoromethylthio-modified ribonucleic acids. J Am Chem Soc 2014; 136:6656-63. [PMID: 24766131 PMCID: PMC4021565 DOI: 10.1021/ja5005637] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
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The chemical synthesis of ribonucleic
acids (RNA) with novel chemical
modifications is largely driven by the motivation to identify eligible
functional probes for the various applications in life sciences. To
this end, we have a strong focus on the development of novel fluorinated
RNA derivatives that are powerful in NMR spectroscopic analysis of
RNA folding and RNA ligand interactions. Here, we report on the synthesis
of 2′-SCF3 pyrimidine nucleoside containing oligoribonucleotides
and the comprehensive investigation of their structure and base pairing
properties. While this modification has a modest impact on thermodynamic
stability when it resides in single-stranded regions, it was found
to be destabilizing to a surprisingly high extent when located in
double helical regions. Our NMR spectroscopic investigations on short
single-stranded RNA revealed a strong preference for C2′-endo
conformation of the 2′-SCF3 ribose unit. Together
with a recent computational study (L. Li, J. W. Szostak, J.
Am. Chem. Soc. 2014, 136, 2858–2865)
that estimated the extent of destabilization caused by a single C2′-endo
nucleotide within a native RNA duplex to amount to 6 kcal mol−1 because of disruption of the planar base pair structure,
these findings support the notion that the intrinsic preference for
C2′-endo conformation of 2′-SCF3 nucleosides
is most likely responsible for the pronounced destabilization of double
helices. Importantly, we were able to crystallize 2′-SCF3 modified RNAs and solved their X-ray structures at atomic
resolution. Interestingly, the 2′-SCF3 containing
nucleosides that were engaged in distinct mismatch arrangements, but
also in a standard Watson–Crick base pair, adopted the same
C3′-endo ribose conformations as observed in the structure
of the unmodified RNA. Likely, strong crystal packing interactions
account for this observation. In all structures, the fluorine atoms
made surprisingly close contacts to the oxygen atoms of the corresponding
pyrimidine nucleobase (O2), and the 2′-SCF3 moieties
participated in defined water-bridged hydrogen-bonding networks in
the minor groove. All these features allow a rationalization of the
structural determinants of the 2′-SCF3 nucleoside
modification and correlate them to base pairing properties.
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Affiliation(s)
- Marija Košutić
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck , 6020 Innsbruck, Austria
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8
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Mathis G, Bourg S, Aci-Sèche S, Truffert JC, Asseline U. Synthesis and properties of 2'-O-neopentyl modified oligonucleotides. Org Biomol Chem 2013; 11:1345-57. [PMID: 23318410 DOI: 10.1039/c2ob26871j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
2'-O-Neopentyldeoxyuridine (Un) was synthesized and incorporated into a series of oligodeoxyribonucleotides. Single and triple incorporations in various arrangements were performed. The Watson and Crick pairing properties with complementary DNA and RNA were investigated by UV melting curves, CD spectroscopy, and molecular dynamic simulations. The results were compared to those obtained with DNA-DNA and DNA-RNA duplexes involving dU at the same positions. Oligonucleotides containing Un clearly demonstrated their ability to form duplexes with both complementary DNA and RNA but with higher stabilities for the DNA-RNA duplexes similar to the one of the parent DNA-RNA duplex. Investigations into the thermodynamic properties of these 17-base-pair duplexes revealed ΔG values (37 °C) that are in line with the measured T(m) values for both the DNA-DNA and DNA-RNA duplexes. CD spectroscopic structural investigations indicated that the conformations of the DNA-DNA and DNA-RNA duplexes involving Un are similar to those of the dT-rA and dU-rA containing duplexes. Only small changes in intensities and weak blue shifts were observed when three Uns were incorporated into the duplexes. The results of the molecular dynamic simulations showed, for the six duplexes involving the modified nucleoside Un, calculated curvatures similar to those of the corresponding unmodified duplexes without base-pair disruption. The neopentyl group is able to be accommodated in the minor grooves of both the DNA-DNA and RNA-DNA duplexes. However, molecular dynamic simulations indicated that the Uns adopt a C2'-exo sugar pucker conformation close to an A-helix type without perturbing the C2'-endo sugar pucker conformations of their 2'-deoxynucleoside neighbours. These results confirm the potential of 2'-O-neopentyldeoxyuridine as a nucleoside surrogate for oligonucleotide based therapeutic strategies.
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Affiliation(s)
- Gérald Mathis
- Centre de Biophysique Moléculaire UPR 4301 CNRS, Conventionnée avec l'Université d'Orléans, Rue Charles Sadron, 45071 Orléans Cedex 02, France
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9
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Patra A, Harp J, Pallan PS, Zhao L, Abramov M, Herdewijn P, Egli M. Structure, stability and function of 5-chlorouracil modified A:U and G:U base pairs. Nucleic Acids Res 2012; 41:2689-97. [PMID: 23275540 PMCID: PMC3575798 DOI: 10.1093/nar/gks1316] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The thymine analog 5-chlorouridine, first reported in the 1950s as anti-tumor agent, is known as an effective mutagen, clastogen and toxicant as well as an effective inducer of sister-chromatid exchange. Recently, the first microorganism with a chemically different genome was reported; the selected Escherichia coli strain relies on the four building blocks 5-chloro-2'-deoxyuridine (ClU), A, C and G instead of the standard T, A, C, G alphabet [Marlière,P., Patrouix,J., Döring,V., Herdewijn,P., Tricot,S., Cruveiller,S., Bouzon,M. and Mutzel,R. (2011) Chemical evolution of a bacterium's genome. Angew. Chem. Int. Ed., 50, 7109-7114]. The residual fraction of T in the DNA of adapted bacteria was <2% and the switch from T to ClU was accompanied by a massive number of mutations, including >1500 A to G or G to A transitions in a culture. The former is most likely due to wobble base pairing between ClU and G, which may be more common for ClU than T. To identify potential changes in the geometries of base pairs and duplexes as a result of replacement of T by ClU, we determined four crystal structures of a B-form DNA dodecamer duplex containing ClU:A or ClU:G base pairs. The structures reveal nearly identical geometries of these pairs compared with T:A or T:G, respectively, and no consequences for stability and cleavage by an endonuclease (EcoRI). The lack of significant changes in the geometry of ClU:A and ClU:G base pairs relative to the corresponding native pairs is consistent with the sustained unlimited self-reproduction of E. coli strains with virtually complete T→ClU genome substitution.
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Affiliation(s)
- Amritraj Patra
- Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, TN 37232, USA
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Fauster K, Kreutz C, Micura R. 2'-SCF3 uridine-a powerful label for probing structure and function of RNA by 19F NMR spectroscopy. Angew Chem Int Ed Engl 2012; 51:13080-4. [PMID: 23161779 PMCID: PMC3555429 DOI: 10.1002/anie.201207128] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Indexed: 12/20/2022]
Abstract
Fluorishing: the Togni reagent allows efficient synthetic access to fluorine-labeled RNA molecules. These are in turn highly useful for NMR spectroscopic analyses of secondary and tertiary structures, RNA-protein interactions, and functionality of riboswitch modules.
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Affiliation(s)
- Katja Fauster
- Institute of Organic Chemistry (IOC) and Center for Molecular Biosciences (CMBI), University of Innsbruck, Center for Chemistry and Biomedicine (CCB)020 Innsbruck (Austria)
| | - Christoph Kreutz
- Institute of Organic Chemistry (IOC) and Center for Molecular Biosciences (CMBI), University of Innsbruck, Center for Chemistry and Biomedicine (CCB)020 Innsbruck (Austria)
| | - Ronald Micura
- Institute of Organic Chemistry (IOC) and Center for Molecular Biosciences (CMBI), University of Innsbruck, Center for Chemistry and Biomedicine (CCB)020 Innsbruck (Austria)
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Fauster K, Kreutz C, Micura R. 2′-SCF3Uridine-A Powerful Label for Probing Structure and Function of RNA by19F NMR Spectroscopy. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201207128] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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12
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Pallan PS, Marquez VE, Egli M. The conformationally constrained N-methanocarba-dT analogue adopts an unexpected C4'-exo sugar pucker in the structure of a DNA hairpin. Biochemistry 2012; 51:2639-41. [PMID: 22409313 DOI: 10.1021/bi300215k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Incorporation of a bicyclo[3.1.0]hexane scaffold into the nucleoside sugar was devised to lock the embedded cyclopentane ring in conformations that mimic the furanose North and South sugar puckers. To analyze the effects of North-methanocarba-2'-deoxythymidine (N-MCdT) on the B-form DNA, we crystallized d(CGCGAA[mcTmcT]CGCG) with two N-MCdTs. Instead of a duplex, the 12mer forms a tetraloop hairpin, whereby loop N-MCdTs adopt the C4'-exo pucker (NE; P = 50°). Thus, the bicyclic framework does not limit the pucker to the anticipated C2'-exo range (NNW; P = -18°).
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Affiliation(s)
- Pradeep S Pallan
- Department of Biochemistry, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232, United States
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Gore KR, Nawale GN, Harikrishna S, Chittoor VG, Pandey SK, Höbartner C, Patankar S, Pradeepkumar PI. Synthesis, gene silencing, and molecular modeling studies of 4'-C-aminomethyl-2'-O-methyl modified small interfering RNAs. J Org Chem 2012; 77:3233-45. [PMID: 22372696 DOI: 10.1021/jo202666m] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The linear syntheses of 4'-C-aminomethyl-2'-O-methyl uridine and cytidine nucleoside phosphoramidites were achieved using glucose as the starting material. The modified RNA building blocks were incorporated into small interfering RNAs (siRNAs) by employing solid phase RNA synthesis. Thermal melting studies showed that the modified siRNA duplexes exhibited slightly lower T(m) (∼1 °C/modification) compared to the unmodified duplex. Molecular dynamics simulations revealed that the 4'-C-aminomethyl-2'-O-methyl modified nucleotides adopt South-type conformation in a siRNA duplex, thereby altering the stacking and hydrogen-bonding interactions. These modified siRNAs were also evaluated for their gene silencing efficiency in HeLa cells using a luciferase-based reporter assay. The results indicate that the modifications are well tolerated in various positions of the passenger strand and at the 3' end of the guide strand but are less tolerated in the seed region of the guide strand. The modified siRNAs exhibited prolonged stability in human serum compared to unmodified siRNA. This work has implications for the use of 4'-C-aminomethyl-2'-O-methyl modified nucleotides to overcome some of the challenges associated with the therapeutic utilities of siRNAs.
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Affiliation(s)
- Kiran R Gore
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
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14
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Erande N, Gunjal AD, Fernandes M, Kumar VA. Probing the furanose conformation in the 2′–5′strand of isoDNA : RNA duplexes by freezing the nucleoside conformations. Chem Commun (Camb) 2011; 47:4007-9. [DOI: 10.1039/c0cc05402j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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15
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Egli M, Pallan PS. The many twists and turns of DNA: template, telomere, tool, and target. Curr Opin Struct Biol 2010; 20:262-75. [PMID: 20381338 DOI: 10.1016/j.sbi.2010.03.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 03/15/2010] [Indexed: 11/16/2022]
Abstract
If any proof were needed of DNA's versatile roles and use, it is certainly provided by the numerous depositions of new three-dimensional (3D) structures to the coordinate databanks (PDB, NDB) over the last two years. Quadruplex motifs involving G-repeats, adducted sequences and oligo-2'-deoxynucleotides (ODNs) with bound ligands are particularly well represented. In addition, structures of chemically modified DNAs (CNAs) and artificial analogs are yielding insight into stability, pairing properties, and dynamics, including those of the native nucleic acids. Besides being of significance for establishing diagnostic tools and in the analysis of protein-DNA interactions, chemical modification in conjunction with investigations of the structural consequences may yield novel nucleic acid-based therapeutics. DNA's predictable and highly specific pairing behavior makes it the material of choice for constructing 3D-nanostructures of defined architecture. Recently the first examples of DNA nanoparticle and self-assembled 3D-crystals were reported. Although the structures discussed in this review are all based either on X-ray crystallography or solution NMR, small angle X-ray scattering (SAXS), and cryoEM are proving to be useful approaches for the characterization of nanoscale DNA architecture.
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Affiliation(s)
- Martin Egli
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37232-0146, USA.
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16
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Egli M, Pallan PS. Crystallographic studies of chemically modified nucleic acids: a backward glance. Chem Biodivers 2010; 7:60-89. [PMID: 20087997 PMCID: PMC2905155 DOI: 10.1002/cbdv.200900177] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Chemically modified nucleic acids (CNAs) are widely explored as antisense oligonucleotide or small interfering RNA (siRNA) candidates for therapeutic applications. CNAs are also of interest in diagnostics, high-throughput genomics and target validation, nanotechnology and as model systems in investigations directed at a better understanding of the etiology of nucleic acid structure, as well as the physicochemical and pairing properties of DNA and RNA, and for probing protein-nucleic acid interactions. In this article, we review research conducted in our laboratory over the past two decades with a focus on crystal-structure analyses of CNAs and artificial pairing systems. We highlight key insights into issues ranging from conformational distortions as a consequence of modification to the modulation of pairing strength, and RNA affinity by stereoelectronic effects and hydration. Although crystal structures have only been determined for a subset of the large number of modifications that were synthesized and analyzed in the oligonucleotide context to date, they have yielded guiding principles for the design of new analogs with tailor-made properties, including pairing specificity, nuclease resistance, and cellular uptake. And, perhaps less obviously, crystallographic studies of CNAs and synthetic pairing systems have shed light on fundamental aspects of DNA and RNA structure and function that would not have been disclosed by investigations solely focused on the natural nucleic acids.
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Affiliation(s)
- Martin Egli
- Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-0146, USA.
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