51
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Inhibition of multidrug resistance by SV40 pseudovirion delivery of an antigene peptide nucleic acid (PNA) in cultured cells. PLoS One 2011; 6:e17981. [PMID: 21445346 PMCID: PMC3062552 DOI: 10.1371/journal.pone.0017981] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 02/17/2011] [Indexed: 11/19/2022] Open
Abstract
Peptide nucleic acid (PNA) is known to bind with extraordinarily high affinity and sequence-specificity to complementary nucleic acid sequences and can be used to suppress gene expression. However, effective delivery into cells is a major obstacle to the development of PNA for gene therapy applications. Here, we present a novel method for the in vitro delivery of antigene PNA to cells. By using a nucleocapsid protein derived from Simian virus 40, we have been able to package PNA into pseudovirions, facilitating the delivery of the packaged PNA into cells. We demonstrate that this system can be used effectively to suppress gene expression associated with multidrug resistance in cancer cells, as shown by RT-PCR, flow cytometry, Western blotting, and cell viability under chemotherapy. The combination of PNA with the SV40-based delivery system is a method for suppressing a gene of interest that could be broadly applied to numerous targets.
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Hu J, Gagnon KT, Liu J, Watts JK, Syeda-Nawaz J, Bennett CF, Swayze EE, Randolph J, Chattopadhyaya J, Corey DR. Allele-selective inhibition of ataxin-3 (ATX3) expression by antisense oligomers and duplex RNAs. Biol Chem 2011; 392:315-25. [PMID: 21294677 DOI: 10.1515/bc.2011.045] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Spinocerebellar ataxia-3 (also known as Machado-Joseph disease) is an incurable neurodegenerative disorder caused by expression of a mutant variant of ataxin-3 (ATX3) protein. Inhibiting expression of ATX3 would provide a therapeutic strategy, but indiscriminant inhibition of both wild-type and mutant ATX3 might lead to undesirable side effects. An ideal silencing agent would block expression of mutant ATX3 while leaving expression of wild-type ATX3 intact. We have previously observed that peptide nucleic acid (PNA) conjugates targeting the expanded CAG repeat within ATX3 mRNA block expression of both alleles. We have now identified additional PNAs capable of inhibiting ATX3 expression that vary in length and in the nature of the conjugated cation chain. We can also achieve potent and selective inhibition using duplex RNAs containing one or more mismatches relative to the CAG repeat. Anti-CAG antisense bridged nucleic acid oligonucleotides that lack a cationic domain are potent inhibitors but are not allele-selective. Allele-selective inhibitors of ATX3 expression provide insights into the mechanism of selectivity and promising lead compounds for further development and in vivo investigation.
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Affiliation(s)
- Jiaxin Hu
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390-9041, USA
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53
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Pensato S, Saviano M, Bianchi N, Borgatti M, Fabbri E, Gambari R, Romanelli A. gamma-Hydroxymethyl PNAs: Synthesis, interaction with DNA and inhibition of protein/DNA interactions. Bioorg Chem 2010; 38:196-201. [PMID: 20643471 DOI: 10.1016/j.bioorg.2010.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 06/22/2010] [Accepted: 06/25/2010] [Indexed: 10/19/2022]
Abstract
The ability of PNA to interact with DNA double stranded has been recently investigated. In a decoy approach these interactions are of great importance as may lead to inhibition of interactions of DNA sequences to specific transcription factors and may be employed as a strategy for the inhibition of gene transcription alternative to the antisense strategy (targeting transcription factors mRNAs) and the transcription factor decoy approach (targeting transcription factors). We explored the ability of PNA and PNAs with modified monomers to bind to DNA and to interfere in the formation of DNA/transcription factor complex. We report a procedure for the synthesis of Fmoc-gamma-hydroxymetyl PNA, the synthesis and CD analysis of PNA oligomers containing the modified monomer in different positions and EMSA assays to test the: (a) binding to double stranded DNA and (b) inhibition of DNA-protein interactions.
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54
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Lewis HD, Husain A, Donnelly RJ, Barlos D, Riaz S, Ginjupalli K, Shodeinde A, Barton BE. Creation of a novel peptide with enhanced nuclear localization in prostate and pancreatic cancer cell lines. BMC Biotechnol 2010; 10:79. [PMID: 21029412 PMCID: PMC2987774 DOI: 10.1186/1472-6750-10-79] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 10/28/2010] [Indexed: 11/10/2022] Open
Abstract
Background For improved uptake of oligonucleotide-based therapy, the oligonucleotides often are coupled to peptides that facilitate entry into cells. To this end, novel cell-penetrating peptides (CPPs) were designed for mediating intracellular uptake of oligonucleotide-based therapeutics. The novel peptides were based on taking advantage of the nuclear localization properties of transcription factors in combination with a peptide that would bind putatively to cell surfaces. It was observed that adding a glutamate peptide to the N-terminus of the nuclear localization signal (NLS) of the Oct6 transcription factor resulted in a novel CPP with better uptake and better nuclear colocalization than any other peptide tested. Results Uptake of the novel peptide Glu-Oct6 by cancer cell lines was rapid (in less than 1 hr, more than 60% of DU-145 cells were positive for FITC), complete (by 4 hr, 99% of cells were positive for FITC), concentration-dependent, temperature-dependent, and inhibited by sodium azide (NaN3). Substitution of Phe, Tyr, or Asn moieties for the glutamate portion of the novel peptide resulted in abrogation of novel CPP uptake; however none of the substituted peptides inhibited uptake of the novel CPP when coincubated with cells. Live-cell imaging and analysis by imaging flow cytometry revealed that the novel CPP accumulated in nuclei. Finally, the novel CPP was coupled to a carboxyfluorescein-labeled synthetic oligonucleotide, to see if the peptide could ferry a therapeutic payload into cells. Conclusions These studies document the creation of a novel CPP consisting of a glutamate peptide coupled to the N-terminus of the Oct6 NLS; the novel CPP exhibited nuclear colocalization as well as uptake by prostate and pancreatic cancer cell lines.
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Affiliation(s)
- H Dan Lewis
- Department of Surgery, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, 185 S, Orange Avenue, Newark, NJ 07103, USA
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55
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Loew M, Springer R, Scolari S, Altenbrunn F, Seitz O, Liebscher J, Huster D, Herrmann A, Arbuzova A. Lipid domain specific recruitment of lipophilic nucleic acids: a key for switchable functionalization of membranes. J Am Chem Soc 2010; 132:16066-72. [PMID: 20964327 DOI: 10.1021/ja105714r] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Lipid domains in mammalian plasma membranes serve as platforms for specific recruitment or separation of proteins involved in various functions. Here, we have applied this natural strategy of lateral separation to functionalize lipid membranes at micrometer scale in a switchable and reversible manner. Membrane-anchored peptide nucleic acid and DNA, differing in their lipophilic moieties, partition into different lipid domains in model and biological membranes. Separation was visualized by hybridization with the respective complementary fluorescently labeled DNA strands. Upon heating, domains vanished, and both lipophilic nucleic acid structures intermixed with each other. Reformation of the lipid domains by cooling led again to separation of membrane-anchored nucleic acids. By linking appropriate structures/functions to complementary strands, this approach offers a reversible tool for triggering interactions among the structures and for the arrangement of reactions and signaling cascades on biomimetic surfaces.
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Affiliation(s)
- Martin Loew
- Institute of Biology/Biophysics, Humboldt-University Berlin, Invalidenstrasse 42, 10115 Berlin, Germany
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56
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Fraternale A, Paoletti MF, Casabianca A, Orlandi C, Millo E, Balestra E, Damonte G, Perno CF, Magnani M. Erythrocytes as carriers of antisense PNA addressed against HIV-1 gag-pol transframe domain. J Drug Target 2010; 17:278-85. [PMID: 19255894 DOI: 10.1080/10611860902737474] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
PNA(PR2) is a peptide nucleic acid (PNA) complementary to a sequence of the viral protease-encoding gene, effective in blocking HIV release, when used at high doses. Erythrocytes (RBC) were used to target PNA(PR2) to the macrophage compartment. The antiviral activity was assessed in human HIV-infected macrophages both as inhibition of p24 production and reduction of HIV DNA content. PNA(PR2), either added to the medium at a concentration of 100 microM or loaded into RBC at about 40 microM, inhibited p24 production approximately 80% compared with infected samples and reduced HIV DNA content by 83% and 90%, respectively. The results show that (1) a stronger anti-HIV effect is achievable with higher doses of PNA(PR2), both when given free and encapsulated into RBC; (2) the antiviral effect obtained by free PNA(PR2) at a concentration of 100 microM is achievable by encapsulating it into RBC at a concentration of 40 microM, suggesting that RBC can be used as a delivery system to increase the antisense effect of PNA(PR2).
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Affiliation(s)
- Alessandra Fraternale
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, PU, Italy.
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57
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Chu Y, Yue X, Younger ST, Janowski BA, Corey DR. Involvement of argonaute proteins in gene silencing and activation by RNAs complementary to a non-coding transcript at the progesterone receptor promoter. Nucleic Acids Res 2010; 38:7736-48. [PMID: 20675357 PMCID: PMC2995069 DOI: 10.1093/nar/gkq648] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Double-stranded RNAs that are complementary to non-coding transcripts at gene promoters can activate or inhibit gene expression in mammalian cells. Understanding the mechanism for modulating gene expression by promoter-targeted antigene RNAs (agRNAs) will require identification of the proteins involved in recognition. Previous reports have implicated argonaute (AGO) proteins, but identifications have differed with involvement of AGO1, AGO2, or both AGO1 and AGO2 being reported by different studies. The roles of AGO3 and AGO4 have not been investigated. Here, we examine the role of AGO 1–4 in gene silencing and activation of the progesterone receptor (PR) gene. Expression of AGO2 is necessary for efficient gene silencing or activation and AGO2 is recruited to the non-coding transcript that overlaps the promoter during both gene silencing and activation. Expression of AGO1, AGO3 and AGO4 are not necessary for gene silencing or activation nor are AGO1, AGO3, or AGO4 recruited to the target non-coding transcript during gene activation. These data indicate that AGO2 is the primary AGO variant involved in modulating expression of PR by agRNAs.
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Affiliation(s)
- Yongjun Chu
- Department of Pharmacology and Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA
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58
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Affiliation(s)
- Peter E Nielsen
- Department of Cellular and Molecular Medicine, Faculty of Health Sciences, The Panum Institute, University of Copenhagen, Blegdamsvej 3c, DK-2200, Copenhagen.
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59
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Watts JK, Yu D, Charisse K, Montaillier C, Potier P, Manoharan M, Corey DR. Effect of chemical modifications on modulation of gene expression by duplex antigene RNAs that are complementary to non-coding transcripts at gene promoters. Nucleic Acids Res 2010; 38:5242-59. [PMID: 20403811 PMCID: PMC2926613 DOI: 10.1093/nar/gkq258] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Antigene RNAs (agRNAs) are small RNA duplexes that target non-coding transcripts rather than mRNA and specifically suppress or activate gene expression in a sequence-dependent manner. For many applications in vivo, it is likely that agRNAs will require chemical modification. We have synthesized agRNAs that contain different classes of chemical modification and have tested their ability to modulate expression of the human progesterone receptor gene. We find that both silencing and activating agRNAs can retain activity after modification. Both guide and passenger strands can be modified and functional agRNAs can contain 2'F-RNA, 2'OMe-RNA, and locked nucleic acid substitutions, or combinations of multiple modifications. The mechanism of agRNA activity appears to be maintained after chemical modification: both native and modified agRNAs modulate recruitment of RNA polymerase II, have the same effect on promoter-derived antisense transcripts, and must be double-stranded. These data demonstrate that agRNA activity is compatible with a wide range of chemical modifications and may facilitate in vivo applications.
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Affiliation(s)
- Jonathan K Watts
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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60
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Sharma S, Sonavane UB, Joshi RR. Molecular dynamics simulations of cyclohexyl modified peptide nucleic acids (PNA). J Biomol Struct Dyn 2010; 27:663-76. [PMID: 20085383 DOI: 10.1080/07391102.2010.10508580] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Peptide Nucleic Acids (PNA) that bind sequence specifically to DNA/RNA are of major interest in the field of molecular biology and could form the basis for gene-targeted drugs. Molecular dynamics simulations are aimed to characterize the structural and dynamical features to understand the effect of backbone modification on the structure and dynamics along with the stability of the resulting 10mer complexes of PNA with DNA/RNA. Twelve Molecular Dynamics (MD) simulations of duplexes and triplexes with and without cyclohexyl modification were carried out for 10ns each. The simulations indicate that the cyclohexyl modification with different stereoisomers has influenced all the PNA-DNA/RNA complexes. Modification has added rigidity to backbone by restricting beta to +60 in case of (1R,2S) cyclohexyl PNA and to -60 in case of (1S,2R) cyclohexyl PNA. The results of MD simulations were able to show the backbone rigidification and preference for RNA complexes over DNA due to presence of cyclohexyl ring in the PNA backbone.
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Affiliation(s)
- Smriti Sharma
- Bioinformatics Team, Centre for Development of Advanced Computing, Ganesh Khind, Pune University Campus, Pune - 411007
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61
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Sau SP, Kumar TS, Hrdlicka PJ. Invader LNA: efficient targeting of short double stranded DNA. Org Biomol Chem 2010; 8:2028-36. [PMID: 20401378 DOI: 10.1039/b923465a] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Despite progress with triplex-forming oligonucleotides or helix-invading peptide nucleic acids (PNAs), there remains a need for probes facilitating sequence-unrestricted targeting of double stranded DNA (dsDNA) at physiologically relevant conditions. Invader LNA probes, i.e., DNA duplexes with "+1 interstrand zipper arrangements" of intercalator-functionalized 2'-amino-alpha-l-LNA monomers, are demonstrated herein to recognize short mixed sequence dsDNA targets. This approach, like pseudo-complementary PNA (pcPNA), relies on relative differences in stability between probe duplexes and the corresponding probe:target duplexes for generation of a favourable thermodynamic gradient. Unlike pcPNA, Invader LNA probes take advantage of the "nearest neighbour exclusion principle", i.e., intercalating units of Invader LNA monomers are poorly accommodated in probe duplexes but extraordinarily well tolerated in probe-target duplexes (DeltaT(m)/modification up to +11.5 degrees C). Recognition of isosequential dsDNA-targets occurs: a) at experimental temperatures much lower than the thermal denaturation temperatures (T(m)'s) of Invader LNAs or dsDNA-targets, b) at a wide range of ionic strengths, and c) with good mismatch discrimination. Recognition of dsDNA is monitored in real-time using inherent pyrene-pyrene excimer signals of Invader LNA probes, which provides insights into reaction kinetics and enables rational design of probes. These properties render Invader LNAs as promising probes for biomedical applications entailing sequence-unrestricted recognition of dsDNA.
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Affiliation(s)
- Sujay P Sau
- Department of Chemistry, University of Idaho, Moscow, ID 83844-2343, USA
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62
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Shen G, Fang H, Song Y, Bielska AA, Wang Z, Taylor JSA. Phospholipid conjugate for intracellular delivery of peptide nucleic acids. Bioconjug Chem 2009; 20:1729-36. [PMID: 19678628 DOI: 10.1021/bc900048y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Peptide nucleic acids (PNAs) have a number of attractive features that have made them an ideal choice for antisense and antigene-based tools, probes, and drugs, but their poor membrane permeability has limited their application as therapeutic or diagnostic agents. Herein, we report a general method for the synthesis of phospholipid-PNAs (LP-PNAs) and compare the effect of noncleavable lipids and bioreductively cleavable lipids (L and LSS) and phospholipid (LP) on the splice-correcting bioactivity of a PNA bearing the cell penetrating Arg9 group (PNA-R9). While the three constructs show similar and increasing bioactivity at 1-3 microM, the activity of LP-PNA-R9 continues to increase from 4-6 microM, while the activity of L-PNA-R9 remains constant and that of LSS-PNA-R9 decreases rapidly in parallel with their relative cytotoxicity. The activity of both LP-PNA-R9 and L-PNA-R9 dramatically increased in the presence of chloroquine, as expected for an endocytotic entry mechanism. The constructs were also found to have CMC values of 1.0 and 4.5 microM, respectively, in 150 mM NaCl, pH 7 water, suggesting that micelle formation may play a hitherto unrecognized role in modulating toxicity and/or facilitating endocytosis.
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Affiliation(s)
- Gang Shen
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, USA
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63
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Hu J, Dodd DW, Hudson RHE, Corey DR. Cellular localization and allele-selective inhibition of mutant huntingtin protein by peptide nucleic acid oligomers containing the fluorescent nucleobase [bis-o-(aminoethoxy)phenyl]pyrrolocytosine. Bioorg Med Chem Lett 2009; 19:6181-4. [PMID: 19783436 PMCID: PMC2770837 DOI: 10.1016/j.bmcl.2009.09.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 08/31/2009] [Accepted: 09/02/2009] [Indexed: 12/16/2022]
Abstract
Peptide nucleic acid (PNA) is a successful DNA/RNA mimic. A major challenge for research is to invent chemically modified PNAs that retain the favorable properties of the parent compound while improving biological recognition. Here, we test modified PNAs containing [bis-o-(aminoethoxy)phenyl]pyrrolocytosine bases designed to engage guanine with an additional hydrogen bond. We observe elevated melting temperatures, localization to cellular compartments, and allele-selective inhibition of mutant huntingtin protein expression.
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Affiliation(s)
- Jiaxin Hu
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center at Dallas, Dallas, 6001 Forest Park Road TX 75390, USA
| | - David W. Dodd
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada, N6A 5B7
| | - Robert H. E. Hudson
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada, N6A 5B7
| | - David R. Corey
- Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center at Dallas, Dallas, 6001 Forest Park Road TX 75390, USA
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64
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Hu J, Matsui M, Corey DR. Allele-selective inhibition of mutant huntingtin by peptide nucleic acid-peptide conjugates, locked nucleic acid, and small interfering RNA. Ann N Y Acad Sci 2009; 1175:24-31. [PMID: 19796074 DOI: 10.1111/j.1749-6632.2009.04975.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability to inhibit expression of a mutant allele while retaining expression of a wild-type protein might provide a useful approach to treating Huntington's Disease (HD) and other inherited pathologies. The mutant form of huntingtin (HTT), the protein responsible for HD, is encoded by an mRNA containing an expanded CAG repeat. We demonstrate that peptide nucleic acid conjugates and locked nucleic acids complementary to the CAG repeat selectively block expression of mutant HTT. The selectivity of inhibition is at least as good as that shown by a small interfering RNA targeted to a deletion polymorphism. Our data suggest that antisense oligomers are promising subjects for further development as an anti-HD therapeutic strategy.
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Affiliation(s)
- Jiaxin Hu
- Department of Pharmacology and Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041, USA
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65
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Fang H, Zhang K, Shen G, Wooley KL, Taylor JSA. Cationic shell-cross-linked knedel-like (cSCK) nanoparticles for highly efficient PNA delivery. Mol Pharm 2009; 6:615-26. [PMID: 19231840 DOI: 10.1021/mp800199w] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Peptide nucleic acids have a number of features that make them an ideal platform for the development of in vitro biological probes and tools. Unfortunately, their inability to pass through membranes has limited their in vivo application as diagnostic and therapeutic agents. Herein, we describe the development of cationic shell-cross-linked knedel-like (cSCK) nanoparticles as highly efficient vehicles for the delivery of PNAs into cells, either through electrostatic complexation with a PNA * ODN hybrid, or through a bioreductively cleavable disulfide linkage to a PNA. These delivery systems are better than the standard Lipofectamine/ODN-mediated method and much better than the Arg(g)-mediated method for PNA delivery in HeLa cells, showing lower toxicity and higher bioactivity. The cSCKs were also found to facilitate both endocytosis and endosomal release of the PNAs, while themselves remaining trapped in the endosomes.
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Affiliation(s)
- Huafeng Fang
- Department of Chemistry, Washington University, One Brookings Drive, St. Louis, Missouri 63130, USA
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66
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Gantchev TG, Girouard S, Dodd DW, Wojciechowski F, Hudson RHE, Hunting DJ. Gamma-radiation induced interstrand cross-links in PNA:DNA heteroduplexes. Biochemistry 2009; 48:7032-44. [PMID: 19469551 DOI: 10.1021/bi9002474] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Peptide nucleic acids (PNAs) efficiently hybridize with DNA and are promoted as versatile gene-targeting analytical tools and pharmaceuticals. However, PNAs have never been exploited as radiopharmaceuticals, and radiation-induced physicochemical modifications of PNA:DNA heteroduplexes have not been studied. Drug- and radiation-induced creation of covalent cross-links in DNA obstruct crucial cell survival processes such as transcription and replication and are thus considered genotoxic events with a high impact in anticancer therapies. Here we report that gamma-irradiation of complementary PNA:DNA heteroduplexes, wherein the PNA contains l-lysine, free amino, or N-methylmorpholinium N- and C-capping groups, results in the formation of irreversible interstrand cross-links (ICL). The number of detected ICL corresponds to the number of available amino functional groups on the PNA. The effect of DNA sequence on the formation of ICL was studied by modifying the terminal nucleotides of the DNA oligonucleotide to create deletions and overhangs. The involvement of abasic sites (ABS) on the DNA strand in the cross-linking reaction was confirmed by independent experiments with synthetic ABS-containing oligonucleotides. Molecular modeling and molecular dynamics (MD) simulations were applied to elucidate the conformation of the N- and C-capping groups of the PNA oligomer and their interactions with the proximal terminus of the DNA. Good agreement between experimental and modeling results was achieved. Modeling indicated that the presence of positively charged capping groups on the PNA increases the conformational flexibility of the PNA:DNA terminal base pairs and often leads to their melting. This disordered orientation of the duplex ends provides conditions for multiple encounters of the short (amino) and bulky (Lys) side chains with nucleobases and the DNA backbone up to the third base pair along the duplex stem. Dangling duplex ends offer favorable conditions for increased accessibility of the radiation-induced free radicals to terminal nucleotides and their damage. It is suggested that the ICL are produced by initial formation of Schiff base adducts between the PNA amino functions and the opposed DNA oxidation-damaged bases or abasic 2'-deoxyribose-derived aldehydic groups. The subsequent reduction by solvated electrons (e(-)(aq)) or other radiation-produced reducing species results in irreversible covalent interstrand cross-links. The simultaneous involvement of oxidizing, (*)OH, and reducing, e(-)(aq), radicals presents a case in which multiple ionization events along a gamma-particle path lead to DNA injuries that also encompass ICL as part of the multiply damaged sites (MDS). The obtained results may find applications in the development of a new generation of gene-targeted radiosensitizers based on PNA vectors.
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Affiliation(s)
- Tsvetan G Gantchev
- Department of Nuclear Medicine and Radiobiology, Faculté de Medecine, Université de Sherbrooke, Sherbrooke, Québec, J1H 5N4 Canada
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67
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Lundin KE, Simonson OE, Moreno PMD, Zaghloul EM, Oprea II, Svahn MG, Smith CIE. Nanotechnology approaches for gene transfer. Genetica 2009; 137:47-56. [PMID: 19488829 DOI: 10.1007/s10709-009-9372-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 05/14/2009] [Indexed: 01/07/2023]
Abstract
In both basic research as well as experimental gene therapy the need to transfer genetic material into a cell is of vital importance. The cellular compartment, which is the target for the genetic material, depends upon application. An siRNA that mediates silencing is preferably delivered to the cytosol while a transgene would need to end up in the nucleus for successful transcription to occur. Furthermore the ability to regulate gene expression has grown substantially since the discovery of RNA interference. In such diverse fields as medical research and agricultural pest control, the capability to alter the genetic output has been a useful tool for pushing the scientific frontiers. This review is focused on nanotechnological approaches to assemble optimised structures of nucleic acid derivatives to facilitate gene delivery as well as promoting down regulation of endogenous genes.
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Affiliation(s)
- Karin E Lundin
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, Karolinska University Hospital, 141 86 Huddinge, Sweden.
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68
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Hu J, Matsui M, Gagnon KT, Schwartz JC, Gabillet S, Arar K, Wu J, Bezprozvanny I, Corey DR. Allele-specific silencing of mutant huntingtin and ataxin-3 genes by targeting expanded CAG repeats in mRNAs. Nat Biotechnol 2009; 27:478-84. [PMID: 19412185 PMCID: PMC2765218 DOI: 10.1038/nbt.1539] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 04/03/2009] [Indexed: 11/09/2022]
Abstract
Expanded trinucleotide repeats cause many neurological diseases. These include Machado-Joseph disease (MJD) and Huntington's disease (HD), which are caused by expanded CAG repeats within an allele of the ataxin-3 (ATXN3) and huntingtin (HTT) genes, respectively. Silencing expression of these genes is a promising therapeutic strategy, but indiscriminate inhibition of both the mutant and wild-type alleles may lead to toxicity, and allele-specific approaches have required polymorphisms that differ among individuals. We report that peptide nucleic acid and locked nucleic acid antisense oligomers that target CAG repeats can preferentially inhibit mutant ataxin-3 and HTT protein expression in cultured cells. Duplex RNAs were less selective than single-stranded oligomers. The activity of the peptide nucleic acids does not involve inhibition of transcription, and differences in mRNA secondary structure or the number of oligomer binding sites may be important. Antisense oligomers that discriminate between wild-type and mutant genes on the basis of repeat length may offer new options for developing treatments for MJD, HD and related hereditary diseases.
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Affiliation(s)
- Jiaxin Hu
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
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Masotti A, Ortaggi G. Peptide nucleic acid-polyethylenimine conjugates promising multifunctional therapeutic tools for the future. Oligonucleotides 2009; 18:301-3. [PMID: 18752376 DOI: 10.1089/oli.2008.0147] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Andrea Masotti
- Chemistry Department, Sapienza Universita di Roma, Rome, Italy.
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70
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Nickita N, Gasser G, Bond AM, Spiccia L. Synthesis, Spectroscopic Properties and Electrochemical Oxidation of RuII-Polypyridyl Complexes Attached to a Peptide Nucleic Acid Monomer Backbone. Eur J Inorg Chem 2009. [DOI: 10.1002/ejic.200801259] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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71
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Chu Y, Hoffman DW, Iverson BL. A pseudocatenane structure formed between DNA and A cyclic bisintercalator. J Am Chem Soc 2009; 131:3499-508. [PMID: 19236098 PMCID: PMC2733282 DOI: 10.1021/ja805676w] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Targeting double-stranded DNA with small molecules remains an active area of basic research. Herein is described a cyclic DNA bisintercalator that is based on two naphthalene diimide (NDI) intercalating units tethered by one linking element specific for binding in the minor groove and the other linking element specific for binding in the major groove. DNase I footprinting revealed a strong preference for binding the sequence 5'-GGTACC-3'. NMR structural studies of the complex with d(CGGTACCG)(2) verified a pseudocatenane structure in which the NDI units reside four base pairs apart, with one linker segment located in the minor groove and the other in the major groove consistent with the linker designs. To the best of our knowledge, this is the first structurally well-characterized pseudocatenane complex between a sequence specific cyclic bisintercalator and intact DNA.
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Affiliation(s)
- Yongjun Chu
- Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - David W. Hoffman
- Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Brent L. Iverson
- Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA
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72
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Juliano R, Alam MR, Dixit V, Kang H. Mechanisms and strategies for effective delivery of antisense and siRNA oligonucleotides. Nucleic Acids Res 2008; 36:4158-71. [PMID: 18558618 PMCID: PMC2475625 DOI: 10.1093/nar/gkn342] [Citation(s) in RCA: 292] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The potential use of antisense and siRNA oligonucleotides as therapeutic agents has elicited a great deal of interest. However, a major issue for oligonucleotide-based therapeutics involves effective intracellular delivery of the active molecules. In this Survey and Summary, we review recent reports on delivery strategies, including conjugates of oligonucleotides with various ligands, as well as use of nanocarrier approaches. These are discussed in the context of intracellular trafficking pathways and issues regarding in vivo biodistribution of molecules and nanoparticles. Molecular-sized chemical conjugates and supramolecular nanocarriers each display advantages and disadvantages in terms of effective and nontoxic delivery. Thus, choice of an optimal delivery modality will likely depend on the therapeutic context.
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Affiliation(s)
- Rudy Juliano
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599, USA.
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73
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Simon P, Cannata F, Concordet JP, Giovannangeli C. Targeting DNA with triplex-forming oligonucleotides to modify gene sequence. Biochimie 2008; 90:1109-16. [PMID: 18460344 DOI: 10.1016/j.biochi.2008.04.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2007] [Accepted: 04/14/2008] [Indexed: 12/19/2022]
Abstract
Molecules that interact with DNA in a sequence-specific manner are attractive tools for manipulating gene sequence and expression. For example, triplex-forming oligonucleotides (TFOs), which bind to oligopyrimidine.oligopurine sequences via Hoogsteen hydrogen bonds, have been used to inhibit gene expression at the DNA level as well as to induce targeted mutagenesis in model systems. Recent advances in using oligonucleotides and analogs to target DNA in a sequence-specific manner will be discussed. In particular, chemical modification of TFOs has been used to improve binding to chromosomal target sequences in living cells. Various oligonucleotide analogs have also been found to expand the range of sequences amenable to manipulation, including so-called "Zorro" locked nucleic acids (LNAs) and pseudo-complementary peptide nucleic acids (pcPNAs). Finally, we will examine the potential of TFOs for directing targeted gene sequence modification and propose that synthetic nucleases, based on conjugation of sequence-specific DNA ligands to DNA damaging molecules, are a promising alternative to protein-based endonucleases for targeted gene sequence modification.
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Affiliation(s)
- Philippe Simon
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, USM 503, 43 rue Cuvier, 75005 Paris, France
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74
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Jain A, Wang G, Vasquez KM. DNA triple helices: biological consequences and therapeutic potential. Biochimie 2008; 90:1117-30. [PMID: 18331847 DOI: 10.1016/j.biochi.2008.02.011] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Accepted: 02/08/2008] [Indexed: 01/25/2023]
Abstract
DNA structure is a critical element in determining its function. The DNA molecule is capable of adopting a variety of non-canonical structures, including three-stranded (i.e. triplex) structures, which will be the focus of this review. The ability to selectively modulate the activity of genes is a long-standing goal in molecular medicine. DNA triplex structures, either intermolecular triplexes formed by binding of an exogenously applied oligonucleotide to a target duplex sequence, or naturally occurring intramolecular triplexes (H-DNA) formed at endogenous mirror repeat sequences, present exploitable features that permit site-specific alteration of the genome. These structures can induce transcriptional repression and site-specific mutagenesis or recombination. Triplex-forming oligonucleotides (TFOs) can bind to duplex DNA in a sequence-specific fashion with high affinity, and can be used to direct DNA-modifying agents to selected sequences. H-DNA plays important roles in vivo and is inherently mutagenic and recombinogenic, such that elements of the H-DNA structure may be pharmacologically exploitable. In this review we discuss the biological consequences and therapeutic potential of triple helical DNA structures. We anticipate that the information provided will stimulate further investigations aimed toward improving DNA triplex-related gene targeting strategies for biotechnological and potential clinical applications.
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Affiliation(s)
- Aklank Jain
- Department of Carcinogenesis, University of Texas, M.D. Anderson Cancer Center, Science Park--Research Division, 1808 Park Road 1-C, P.O. Box 389, Smithville, TX 78957, USA
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75
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Biron E, Voyer N. Towards sequence selective DNA binding: design, synthesis and DNA binding studies of novel bis-porphyrin peptidic nanostructures. Org Biomol Chem 2008; 6:2507-15. [DOI: 10.1039/b803281e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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76
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Beane RL, Ram R, Gabillet S, Arar K, Monia BP, Corey DR. Inhibiting gene expression with locked nucleic acids (LNAs) that target chromosomal DNA. Biochemistry 2007; 46:7572-80. [PMID: 17536839 PMCID: PMC2527755 DOI: 10.1021/bi700227g] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Oligonucleotides containing locked nucleic acid bases (LNAs) have increased affinity for complementary DNA sequences. We hypothesized that enhanced affinity might allow LNAs to recognize chromosomal DNA inside human cells and inhibit gene expression. To test this hypothesis, we synthesized antigene LNAs (agLNAs) complementary to sequences within the promoters of progesterone receptor (PR) and androgen receptor (AR). We observed inhibition of AR and PR expression by agLNAs but not by analogous oligomers containing 2'-methoxyethyl bases or noncomplementary LNAs. Inhibition was dose dependent and exhibited IC50 values of <10 nM. Efficient inhibition depended on the length of the agLNA, the location of LNA bases, the number of LNA substitutions, and the location of the target sequence within the targeted promoter. LNAs targeting sequences at or near transcription start sites yielded better inhibition than LNAs targeting transcription factor binding sites or an inverted repeat. These results demonstrate that agLNAs can recognize chromosomal target sequences and efficiently block gene expression. agLNAs could be used for gene silencing, as cellular probes for chromosome structure, and therapeutic applications.
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Affiliation(s)
- Randall L. Beane
- The Departments of Pharmacology and Biochemistry, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, TX, 75390-9041
| | - Rosalyn Ram
- The Departments of Pharmacology and Biochemistry, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, TX, 75390-9041
| | - Sylvie Gabillet
- SIGMA-Proligo Genopole Campus 1 5, rue Desbruères, 91030 Evry Cedex, France
| | - Khalil Arar
- SIGMA-Proligo Genopole Campus 1 5, rue Desbruères, 91030 Evry Cedex, France
| | | | - David R. Corey
- The Departments of Pharmacology and Biochemistry, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, TX, 75390-9041
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