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Varley AJ, Desaulniers JP. Chemical strategies for strand selection in short-interfering RNAs. RSC Adv 2021; 11:2415-2426. [PMID: 35424193 PMCID: PMC8693850 DOI: 10.1039/d0ra07747j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 12/24/2020] [Indexed: 12/13/2022] Open
Abstract
Therapeutic small interfering RNAs (siRNAs) are double stranded RNAs capable of potent and specific gene silencing through activation of the RNA interference (RNAi) pathway. The potential of siRNA drugs has recently been highlighted by the approval of multiple siRNA therapeutics. These successes relied heavily on chemically modified nucleic acids and their impact on stability, delivery, potency, and off-target effects. Despite remarkable progress, clinical trials still face failure due to off-target effects such as off-target gene dysregulation. Each siRNA strand can downregulate numerous gene targets while also contributing towards saturation of the RNAi machinery, leading to the upregulation of miRNA-repressed genes. Eliminating sense strand uptake effectively reduces off-target gene silencing and helps limit the disruption to endogenous regulatory mechanisms. Therefore, our understanding of strand selection has a direct impact on the success of future siRNA therapeutics. In this review, the approaches used to improve strand uptake are discussed and effective methods are summarized.
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Affiliation(s)
- Andrew J Varley
- Faculty of Science, University of Ontario Institute of Technology Oshawa Ontario L1G 0C5 Canada +1 905 721 3304 +1 905 721 8668 (ext. 3621)
| | - Jean-Paul Desaulniers
- Faculty of Science, University of Ontario Institute of Technology Oshawa Ontario L1G 0C5 Canada +1 905 721 3304 +1 905 721 8668 (ext. 3621)
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Seok H, Lee H, Jang ES, Chi SW. Evaluation and control of miRNA-like off-target repression for RNA interference. Cell Mol Life Sci 2018; 75:797-814. [PMID: 28905147 PMCID: PMC11105550 DOI: 10.1007/s00018-017-2656-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 09/06/2017] [Accepted: 09/07/2017] [Indexed: 01/08/2023]
Abstract
RNA interference (RNAi) has been widely adopted to repress specific gene expression and is easily achieved by designing small interfering RNAs (siRNAs) with perfect sequence complementarity to the intended target mRNAs. Although siRNAs direct Argonaute (Ago), a core component of the RNA-induced silencing complex (RISC), to recognize and silence target mRNAs, they also inevitably function as microRNAs (miRNAs) and suppress hundreds of off-targets. Such miRNA-like off-target repression is potentially detrimental, resulting in unwanted toxicity and phenotypes. Despite early recognition of the severity of miRNA-like off-target repression, this effect has often been overlooked because of difficulties in recognizing and avoiding off-targets. However, recent advances in genome-wide methods and knowledge of Ago-miRNA target interactions have set the stage for properly evaluating and controlling miRNA-like off-target repression. Here, we describe the intrinsic problems of miRNA-like off-target effects caused by canonical and noncanonical interactions. We particularly focus on various genome-wide approaches and chemical modifications for the evaluation and prevention of off-target repression to facilitate the use of RNAi with secured specificity.
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Affiliation(s)
- Heeyoung Seok
- Division of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, Korea
| | - Haejeong Lee
- Division of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, Korea
| | - Eun-Sook Jang
- Division of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, Korea
- EncodeGEN Co. Ltd, Seoul, 06329, Korea
| | - Sung Wook Chi
- Division of Life Sciences, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, Korea.
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Morihiro K, Kasahara Y, Obika S. Biological applications of xeno nucleic acids. MOLECULAR BIOSYSTEMS 2017; 13:235-245. [PMID: 27827481 DOI: 10.1039/c6mb00538a] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Xeno nucleic acids (XNAs) are a group of chemically modified nucleic acid analogues that have been applied to various biological technologies such as antisense oligonucleotides, siRNAs and aptamers.
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Affiliation(s)
- Kunihiko Morihiro
- National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), 7-6-8 Saito-Asagi, Ibaraki, Osaka 567-0085, Japan and Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Yuuya Kasahara
- National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), 7-6-8 Saito-Asagi, Ibaraki, Osaka 567-0085, Japan and Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Satoshi Obika
- National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN), 7-6-8 Saito-Asagi, Ibaraki, Osaka 567-0085, Japan and Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
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Martínez-Montero S, Deleavey GF, Martín-Pintado N, Fakhoury JF, González C, Damha MJ. Locked 2'-Deoxy-2',4'-Difluororibo Modified Nucleic Acids: Thermal Stability, Structural Studies, and siRNA Activity. ACS Chem Biol 2015; 10:2016-23. [PMID: 26053215 DOI: 10.1021/acschembio.5b00218] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
2'-Deoxy-2',4'-difluorouridine (2',4'-diF-rU) was readily incorporated into DNA and RNA oligonucleotides via standard solid phase synthesis protocols. NMR and thermal denaturation (Tm) data of duplexes was consistent with the 2',4'-diF-rU nucleotides adopting a rigid North (RNA-like) sugar conformation, as previously observed for the nucleoside monomer. The impact of this modification on Tm is neutral when incorporated within RNA:RNA duplexes, mildly destabilizing when located in the RNA strand of a DNA:RNA duplex, and highly destabilizing when inserted in the DNA strand of DNA:RNA and DNA:DNA duplexes. Molecular dynamics calculations suggest that the destabilization effect in DNA:DNA and DNA:RNA duplexes is the result of structural distortions created by A/B junctions within the helical structures. Quantum mechanics calculations suggest that the "neutral" effect imparted to A-form duplexes is caused by alterations in charge distribution that compensate the stabilizing effect expected for a pure North-puckered furanose sugar. 2',4'-diF-RNA modified siRNAs were able to trigger RNA interference with excellent efficiency. Of note, incorporation of a few 2',4'-diF-rU residues in the middle of the guide (antisense) strand afforded siRNAs that were more potent than the corresponding siRNAs containing LNA and 2'-F-ANA modifications, and as active as the 2'-F-RNA modified siRNAs.
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Affiliation(s)
- Saúl Martínez-Montero
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B8
| | - Glen F. Deleavey
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B8
| | - Nerea Martín-Pintado
- Instituto de Química Física Rocasolano, CSIC, C/. Serrano 119, 28006 Madrid, Spain
| | - Johans F. Fakhoury
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B8
| | - Carlos González
- Instituto de Química Física Rocasolano, CSIC, C/. Serrano 119, 28006 Madrid, Spain
| | - Masad J. Damha
- Department
of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B8
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5
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Unlocked nucleic acids: implications of increased conformational flexibility for RNA/DNA triplex formation. Biochem J 2015; 464:203-11. [PMID: 25226286 DOI: 10.1042/bj20141023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Unlocked nucleic acids (UNAs) have been introduced at specific positions in short model DNA hairpins and RNA/DNA triplexes for the first time. UNA residues destabilize the hairpins and decrease triplex thermodynamic stability or suppress triplex formation for most of the evaluated structures. Nevertheless, the incorporation of UNA residues at certain positions of dsDNA was found to be energetically favourable or at least did not affect triplex stability. Notably, the most thermodynamically stable UNA-modified triplexes exhibited improved stability at both acidic and physiological pH. The specificity of the interactions between the triplex-forming oligonucleotide and dsDNA was characterized using EMSA for the most thermodynamically stable structures, and triplex dissociation constants were determined. One of the modified triplexes exhibited an improved Kd in comparison with the unmodified triplex. CD and thermal difference spectra indicated that UNA residues do not alter the overall structure of the most thermodynamically stable triplexes. In addition, incubation of the modified oligonucleotides with human serum indicated that the UNAs demonstrate the potential to improve the biological stability of nucleic acids.
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Perlíková P, Karlsen KK, Pedersen EB, Wengel J. Unlocked nucleic acids with a pyrene-modified uracil: synthesis, hybridization studies, fluorescent properties and i-motif stability. Chembiochem 2014; 15:146-56. [PMID: 24501777 DOI: 10.1002/cbic.201300567] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The synthesis of two new phosphoramidite building blocks for the incorporation of 5-(pyren-1-yl)uracilyl unlocked nucleic acid (UNA) monomers into oligonucleotides has been developed. Monomers containing a pyrene-modified nucleobase component were found to destabilize an i-motif structure at pH 5.2, both under molecular crowding and noncrowding conditions. The presence of the pyrene-modified UNA monomers in DNA strands led to decreases in the thermal stabilities of DNA*/DNA and DNA*/RNA duplexes, but these duplexes' thermal stabilities were better than those of duplexes containing unmodified UNA monomers. Pyrene-modified UNA monomers incorporated in bulges were able to stabilize DNA*/DNA duplexes due to intercalation of the pyrene moiety into the duplexes. Steady-state fluorescence emission studies of oligonucleotides containing pyrene-modified UNA monomers revealed decreases in fluorescence intensities upon hybridization to DNA or RNA. Efficient quenching of fluorescence of pyrene-modified UNA monomers was observed after formation of i-motif structures at pH 5.2. The stabilizing/destabilizing effect of pyrene-modified nucleic acids might be useful for designing antisense oligonucleotides and hybridization probes.
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Perlíková P, Ejlersen M, Langkjaer N, Wengel J. Bis-pyrene-modified unlocked nucleic acids: synthesis, hybridization studies, and fluorescent properties. ChemMedChem 2014; 9:2120-7. [PMID: 25044312 DOI: 10.1002/cmdc.201402185] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Indexed: 11/08/2022]
Abstract
Efficient synthesis of a building block for the incorporation of a bis-pyrene-modified unlocked nucleic acid (UNA) into oligonucleotides (DNA*) was developed. The presence of bis-pyrene-modified UNA within a duplex leads to duplex destabilization that is more profound in DNA*/RNA and less distinct in DNA*/DNA duplexes. Nevertheless, the destabilization effect of bis-pyrene-modified UNA is weaker than that of unmodified UNA. Some oligonucleotides with bis-pyrene-modified UNA incorporations displayed superior mismatch discrimination capabilities. UV/Vis absorption and molecular modeling studies indicate that the pyrene groups of bis-pyrene-modified UNA are located in the major groove of a duplex. Oligonucleotides containing two bis-pyrene-modified UNA monomers showed low pyrene monomer emission in bulge-containing duplexes, high pyrene monomer emission in fully matched duplexes, and 5-(pyrenyl)uracil:pyrene exciplex emission in the single-stranded form. Such fluorescent properties enable the application of bis-pyrene-modified UNA in the development of fluorescence probes for DNA/RNA detection and for detection of deletions at specific positions.
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Affiliation(s)
- Pavla Perlíková
- Nucleic Acid Center, Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M (Denmark); Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6 (Czech Republic)
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Xu L, Plouffe SW, Chong J, Wengel J, Wang D. A chemical perspective on transcriptional fidelity: dominant contributions of sugar integrity revealed by unlocked nucleic acids. Angew Chem Int Ed Engl 2013; 52:12341-5. [PMID: 24167045 PMCID: PMC3866818 DOI: 10.1002/anie.201307661] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Indexed: 11/11/2022]
Abstract
Transcription unlocked: A synthetic chemical biology approach involving unlocked nucleic acids was used to dissect the contribution of sugar backbone integrity to the RNA Polymerase II (Pol II) transcription process. An unexpected dominant role for sugar-ring integrity in Pol II transcriptional efficiency and fidelity was revealed.
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Affiliation(s)
- Liang Xu
- Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California, San Diego, La Jolla, California, 92093-0625, USA
| | - Steven W. Plouffe
- Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California, San Diego, La Jolla, California, 92093-0625, USA
| | - Jenny Chong
- Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California, San Diego, La Jolla, California, 92093-0625, USA
| | - Jesper Wengel
- Nucleic Acid Center and Biomolecular Nanoscale Engineering Center, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
| | - Dong Wang
- Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of California, San Diego, La Jolla, California, 92093-0625, USA
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Xu L, Plouffe SW, Chong J, Wengel J, Wang D. A Chemical Perspective on Transcriptional Fidelity: Dominant Contributions of Sugar Integrity Revealed by Unlocked Nucleic Acids. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201307661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Lundin KE, Højland T, Hansen BR, Persson R, Bramsen JB, Kjems J, Koch T, Wengel J, Smith CIE. Biological activity and biotechnological aspects of locked nucleic acids. ADVANCES IN GENETICS 2013; 82:47-107. [PMID: 23721720 DOI: 10.1016/b978-0-12-407676-1.00002-0] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Locked nucleic acid (LNA) is one of the most promising new nucleic acid analogues that has been produced under the past two decades. In this chapter, we have tried to cover many of the different areas, where this molecule has been used to improve the function of synthetic oligonucleotides (ONs). The use of LNA in antisense ONs, including gapmers, splice-switching ONs, and siLNA, as well as antigene ONs, is reviewed. Pharmacokinetics as well as pharmacodynamics of LNA ONs and a description of selected compounds in, or close to, clinical testing are described. In addition, new LNA modifications and the adaptation of enzymes for LNA incorporation are reviewed. Such enzymes may become important for the development of stabilized LNA-containing aptamers.
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Affiliation(s)
- Karin E Lundin
- Clinical Research Center, Department of Laboratory Medicine, Karolinska Institutet, Novum, Huddinge, Stockholm, Sweden.
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Malhotra M, Nambiar S, Rengaswamy V, Prakash S. Small interfering ribonucleic acid design strategies for effective targeting and gene silencing. Expert Opin Drug Discov 2012; 6:269-89. [PMID: 22647204 DOI: 10.1517/17460441.2011.555394] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Gene silencing mediated by siRNAs is becoming a promising therapeutic approach. Although many strategies and technologies have been applied to siRNA design, a key issue lies in the selection of efficient design predictors. Furthermore, the development of systemic siRNA delivery strategies, which would enhance the therapeutic effect, remains a central issue. AREAS COVERED The review discusses the basic principles of the sequence-specific design criteria of functional siRNAs and possible chemical modifications. Some of the most recent advances in the development of siRNA design algorithms and delivery strategies are also presented. Emphasis is given to the important design rule sets and predictors which determine the functionality of an efficient siRNA. EXPERT OPINION The potential and limitations of efficient design predictors obtained from computational algorithms play a crucial role in the development of target-specific siRNAs. Furthermore, the future success of RNA interference therapeutics will depend on their ability to efficiently cross the physiological barriers, selectively target cells-of-interest and finally silence the gene-of-interest without any side effects.
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Affiliation(s)
- Meenakshi Malhotra
- McGill University, Artificial Cells and Organs Research Center, Departments of Biomedical Engineering and Physiology, Biomedical Technology and Cell Therapy Research Laboratory, Faculty of Medicine, 3775 University Street, Montreal, Quebec, H3A 2B4, Canada +1 514 398 3676 ; +1 514 398 7461 ;
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The highly conserved 5' untranslated region as an effective target towards the inhibition of Enterovirus 71 replication by unmodified and appropriate 2'-modified siRNAs. J Biomed Sci 2012; 19:73. [PMID: 22889374 PMCID: PMC3438048 DOI: 10.1186/1423-0127-19-73] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Accepted: 08/08/2012] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Enterovirus 71 (EV71) is a highly infectious agent that plays an etiological role in hand, foot, and mouth disease. It is associated with severe neurological complications and has caused significant mortalities in recent large-scale outbreaks. Currently, no effective vaccine or specific clinical therapy is available against EV71. METHODS Unmodified 21 nucleotide small interfering RNAs (siRNAs) and classic 2'-modified (2'-O-methylation or 2'-fluoro modification) siRNAs were designed to target highly conserved 5' untranslated region (UTR) of the EV71 genome and employed as anti-EV71 agents. Real-time TaqMan RT-PCR, western blot analysis and plaque assays were carried out to evaluate specific viral inhibition by the siRNAs. RESULTS Transfection of rhabdomyosarcoma (RD) cells with siRNAs targeting the EV71 genomic 5' UTR significantly delayed and alleviated the cytopathic effects of EV71 infection, increased cell viability in EV71-infected RD cells. The inhibitory effect on EV71 replication was sequence-specific and dosage-dependent, with significant corresponding decreases in viral RNA, VP1 protein and viral titer. Appropriate 2'-modified siRNAs exhibited similar RNA interference (RNAi) activity with dramatically increased serum stability in comparison with unmodified counterparts. CONCLUSION Sequences were identified within the highly conserved 5' UTR that can be targeted to effectively inhibit EV71 replication through RNAi strategies. Appropriate 2'-modified siRNAs provide a promising approach to optimizing siRNAs to overcome barriers on RNAi-based antiviral therapies for broader administration.
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Abstract
RNA interference (RNAi) has been extensively employed for in vivo research since its use was first demonstrated in mammalian cells 10 years ago. Design rules have improved, and it is now routinely possible to obtain reagents that suppress expression of any gene desired. At the same time, increased understanding of the molecular basis of unwanted side effects has led to the development of chemical modification strategies that mitigate these concerns. Delivery remains the single greatest hurdle to widespread adoption of in vivo RNAi methods. However, exciting advances have been made and new delivery systems under development may help to overcome these barriers. This review discusses advances in RNAi biochemistry and biology that impact in vivo use and provides an overview of select publications that demonstrate interesting applications of these principles. Emphasis is placed on work with synthetic, small interfering RNAs (siRNAs) published since the first installment of this review which appeared in 2006.
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Fechner H, Pinkert S, Geisler A, Poller W, Kurreck J. Pharmacological and biological antiviral therapeutics for cardiac coxsackievirus infections. Molecules 2011; 16:8475-503. [PMID: 21989310 PMCID: PMC6264230 DOI: 10.3390/molecules16108475] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 09/29/2011] [Accepted: 09/30/2011] [Indexed: 01/16/2023] Open
Abstract
Subtype B coxsackieviruses (CVB) represent the most commonly identified infectious agents associated with acute and chronic myocarditis, with CVB3 being the most common variant. Damage to the heart is induced both directly by virally mediated cell destruction and indirectly due to the immune and autoimmune processes reacting to virus infection. This review addresses antiviral therapeutics for cardiac coxsackievirus infections discovered over the last 25 years. One group represents pharmacologically active low molecular weight substances that inhibit virus uptake by binding to the virus capsid (e.g., pleconaril) or inactivate viral proteins (e.g., NO-metoprolol and ribavirin) or inhibit cellular proteins which are essential for viral replication (e.g., ubiquitination inhibitors). A second important group of substances are interferons. They have antiviral but also immunomodulating activities. The third and most recently discovered group includes biological and cellular therapeutics. Soluble receptor analogues (e.g., sCAR-Fc) bind to the virus capsid and block virus uptake. Small interfering RNAs, short hairpin RNAs and antisense oligonucleotides bind to and led to degradation of the viral RNA genome or cellular RNAs, thereby preventing their translation and viral replication. Most recently mesenchymal stem cell transplantation has been shown to possess antiviral activity in CVB3 infections. Taken together, a number of antiviral therapeutics has been developed for the treatment of myocardial CVB infection in recent years. In addition to low molecular weight inhibitors, biological therapeutics have become promising anti-viral agents.
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Affiliation(s)
- Henry Fechner
- Department of Applied Biochemistry, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany; (S.P.); (J.K.)
- Author to whom correspondence should be addressed; ; Tel.: +49-30-31472181; Fax: +49-30-31427502
| | - Sandra Pinkert
- Department of Applied Biochemistry, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany; (S.P.); (J.K.)
| | - Anja Geisler
- Department of Cardiology & Pneumology, Charité – Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany; (A.G.); wolfgang.poller@charite (W.P.)
| | - Wolfgang Poller
- Department of Cardiology & Pneumology, Charité – Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany; (A.G.); wolfgang.poller@charite (W.P.)
| | - Jens Kurreck
- Department of Applied Biochemistry, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany; (S.P.); (J.K.)
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Pasternak A, Wengel J. Unlocked nucleic acid--an RNA modification with broad potential. Org Biomol Chem 2011; 9:3591-7. [PMID: 21431171 DOI: 10.1039/c0ob01085e] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The first unlocked nucleic acid (UNA) monomer was described more than a decade ago, but only recent reports have revealed the true potential applications of this acyclic RNA mimic. UNA monomers enable the modulation of the thermodynamic stability of various nucleic acid structures such as RNA and DNA duplexes, quadruplexes or i-motifs. Moreover, UNA monomers were found to be compatible with RNase H activity, a property which is important for single stranded antisense constructs. Notably, UNA monomers can be applied in the design of superior siRNAs, combining potent gene silencing and dramatically reduced off-target effects.
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Affiliation(s)
- Anna Pasternak
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense M, Denmark
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Abstract
Chemically synthesized siRNAs are widely used for gene silencing. For in vitro applications, stability, delivery, and immunological issues are rarely problematic, but for in vivo applications the situation is different. Limited stability, undesirable pharmacokinetic behaviour, and unanticipated side effects from the immune system call for more careful structural siRNA design and inclusion of chemical modifications at selected positions. Also the notion that siRNA induces significant off-target silencing of many non-related genes has promted new effective measures to enhance specificity. The scope of this review is to provide a simple guide to successful chemical and structural modification of siRNAs with improved activity, stability, specificity, and low toxicity.
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Pasternak A, Wengel J. Modulation of i-motif thermodynamic stability by the introduction of UNA (unlocked nucleic acid) monomers. Bioorg Med Chem Lett 2010; 21:752-5. [PMID: 21185179 DOI: 10.1016/j.bmcl.2010.11.106] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 11/22/2010] [Accepted: 11/23/2010] [Indexed: 02/04/2023]
Abstract
The influence of acyclic RNA derivatives, UNA (unlocked nucleic acid) monomers, on i-DNA thermodynamic stability has been investigated. The 22nt human telomeric fragment was chosen as the model sequence for stability studies. UNA monomers modulate i-motif stability in a position-depending manner. The largest destabilization is observed for position C14, while UNA placed in position A12 causes significant increase of i-DNA thermodynamic stability. CD curves of UNA-modified variants imply no structural changes relative to the native i-motif.
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Affiliation(s)
- Anna Pasternak
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
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Pasternak A, Wengel J. Thermodynamics of RNA duplexes modified with unlocked nucleic acid nucleotides. Nucleic Acids Res 2010; 38:6697-706. [PMID: 20562222 PMCID: PMC2965255 DOI: 10.1093/nar/gkq561] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Thermodynamics provides insights into the influence of modified nucleotide residues on stability of nucleic acids and is crucial for designing duplexes with given properties. In this article, we introduce detailed thermodynamic analysis of RNA duplexes modified with unlocked nucleic acid (UNA) nucleotide residues. We investigate UNA single substitutions as well as model mismatch and dangling end effects. UNA residues placed in a central position makes RNA duplex structure less favourable by 4.0–6.6 kcal/mol. Slight destabilization, by ∼0.5–1.5 kcal/mol, is observed for 5′- or 3′-terminal UNA residues. Furthermore, thermodynamic effects caused by UNA residues are extremely additive with ΔG°37 conformity up to 98%. Direct mismatches involving UNA residues decrease the thermodynamic stability less than unmodified mismatches in RNA duplexes. Additionally, the presence of UNA residues adjacent to unpaired RNA residues reduces mismatch discrimination. Thermodynamic analysis of UNA 5′- and 3′-dangling ends revealed that stacking interactions of UNA residues are always less favourable than that of RNA residues. Finally, circular dichroism spectra imply no changes in overall A-form structure of UNA–RNA/RNA duplexes relative to the unmodified RNA duplexes.
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Affiliation(s)
- Anna Pasternak
- Department of Physics and Chemistry, Nucleic Acid Center, University of Southern Denmark, DK-5230 Odense M, Denmark
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Bramsen JB, Pakula MM, Hansen TB, Bus C, Langkjær N, Odadzic D, Smicius R, Wengel SL, Chattopadhyaya J, Engels JW, Herdewijn P, Wengel J, Kjems J. A screen of chemical modifications identifies position-specific modification by UNA to most potently reduce siRNA off-target effects. Nucleic Acids Res 2010; 38:5761-73. [PMID: 20453030 PMCID: PMC2943616 DOI: 10.1093/nar/gkq341] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Small interfering RNAs (siRNAs) are now established as the preferred tool to inhibit gene function in mammalian cells yet trigger unintended gene silencing due to their inherent miRNA-like behavior. Such off-target effects are primarily mediated by the sequence-specific interaction between the siRNA seed regions (position 2–8 of either siRNA strand counting from the 5′-end) and complementary sequences in the 3′UTR of (off-) targets. It was previously shown that chemical modification of siRNAs can reduce off-targeting but only very few modifications have been tested leaving more to be identified. Here we developed a luciferase reporter-based assay suitable to monitor siRNA off-targeting in a high throughput manner using stable cell lines. We investigated the impact of chemically modifying single nucleotide positions within the siRNA seed on siRNA function and off-targeting using 10 different types of chemical modifications, three different target sequences and three siRNA concentrations. We found several differently modified siRNAs to exercise reduced off-targeting yet incorporation of the strongly destabilizing unlocked nucleic acid (UNA) modification into position 7 of the siRNA most potently reduced off-targeting for all tested sequences. Notably, such position-specific destabilization of siRNA–target interactions did not significantly reduce siRNA potency and is therefore well suited for future siRNA designs especially for applications in vivo where siRNA concentrations, expectedly, will be low.
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Affiliation(s)
- Jesper B Bramsen
- Department of Molecular Biology, University of Aarhus, Arhus, Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark.
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