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Wang Z, Chen L, Bayly SF, Torrence PF. Convergent synthesis of ribonuclease L-active 2',5'-oligoadenylate-peptide nucleic acids. Bioorg Med Chem Lett 2000; 10:1357-60. [PMID: 10890163 DOI: 10.1016/s0960-894x(00)00240-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
2-5A was conjugated to N-(2-aminoethyl)-glycyl PNA by periodate oxidization, followed by coupling with amino-derivatized PNA and final cyanoborohydride reduction. An adduct of 2-5A pentamer with tetrameric thymine PNA activated RNase L with the same potency as earlier versions of 2-5A-PNA or 2-5A-DNA.
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Torrence PF. RSV infections: developments in the search for new drugs. DRUG NEWS & PERSPECTIVES 2000; 13:226-33. [PMID: 12937627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infection in infants and young children, and is also a significant threat to other populations including the immunosuppressed, the elderly and those with chronic chest or cardiac disease. To expand the scope of available antiviral drugs, presently limited to ribavirin, a variety of different structural formats have been explored in the past half-dozen years. Interesting leads for future discovery and lead development include a group of biphenyl relatives (represented by CL-387626) that bind the RSV fusion (F) protein; 2-5A-antisense oligonucleotides that target the RSV genomic RNA; Rho A-derived peptides that block Rho A GTPase interaction with RSV fusion (F) protein; and several compounds of presently unknown mechanisms of action, such as benzodithiins.
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Verheijen JC, van Roon AM, Meeuwenoord NJ, Stuivenberg HR, Bayly SF, Chen L, van der Marel GA, Torrence PF, van Boom JH. Incorporation of a 4-hydroxy-N-acetylprolinol nucleotide analogue improves the 3'-exonuclease stability of 2'-5'-oligoadenylate-antisense conjugates. Bioorg Med Chem Lett 2000; 10:801-4. [PMID: 10782690 DOI: 10.1016/s0960-894x(00)00100-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Incorporation of a 4-hydroxy-N-acetylprolinol nucleotide analogue at the 3'-terminus of DNA or 2-5A-DNA sequences resulted in a significantly enhanced 3'-exonuclease resistance while the affinity for complementary RNA was only slightly decreased. Furthermore, the binding to and activation of human RNase L by thus modified 2-5A-DNA conjugates was not altered as compared to the parent unmodified 2-5A-DNAs.
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29
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Kitade Y, Wakana M, Tsuboi T, Yatome C, Bayly SF, Player MR, Torrence PF. 2-Methyladenosine-Substituted 2',5'-oligoadenylates: conformations, 2-5A binding and catalytic activities with human ribonuclease L. Bioorg Med Chem Lett 2000; 10:329-31. [PMID: 10714492 DOI: 10.1016/s0960-894x(99)00703-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
2-Methyladenosine-substituted analogues of 2-5A, p5'A2'p5'A2'p5'(me2A), p5'(me2A)2'p5'A2'p5'A, and p5'(me2A) 2'p5'(me2A)2'pS'(me2A), were prepared via a modification of a lead ion-catalyzed ligation reaction. These 5'-monophosphates were subsequently converted into the corresponding 5'-triphosphates. Both binding and activation of human recombinant RNase L by various 2-methyladenosine-substituted 2-5A analogues were examined. Among the 2-5A analogues, p5'A2'p5'A2'p5'(me2A) showed the strongest binding affinity and was as effective as 2-5A itself as an activator of RNase L. The CD spectra of both p5'(me2A)2'p5'A2'p5'A and p5'A2'p5'A2'p5'(me2A) were superimposable on that of p5'A2'p5'A2'p5'A, indicative of an anti orientation about the base-glycoside bonds as in naturally occurring 2-5A.
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Geselowitz DA, Cramer H, Wondrak EM, Player MR, Torrence PF. Fluorescence resonance energy transfer analysis of RNase L-catalyzed oligonucleotide cleavage. ANTISENSE & NUCLEIC ACID DRUG DEVELOPMENT 2000; 10:45-51. [PMID: 10726660 DOI: 10.1089/oli.1.2000.10.45] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
A method is described for monitoring the cleavage of an oligoribonucleotide substrate by the 2-5A-dependent RNase L based on fluorescence resonance energy transfer (FRET). The oligoribonucleotide, rC11U2C7, was labeled covalently at its 5'-terminus with fluorescein and at its 3'-terminus with rhodamine to provide a substrate for RNase L. On cleavage, the fluorescence at 538 nm (with 485 nm excitation) increased by a factor of 2.8, allowing real-time quantitation of the reaction progress. The method was performed easily in a 96-well plate format and allowed quantitative high throughput analyses of RNase L activity with different activators.
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31
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Fettes KJ, Howard N, Hickman DT, Adah SA, Player MR, Torrence PF, Micklefield J. Replacement of the phosphodiester linkage in DNA with sulfamide and 3′-N-sulfamate groups. Chem Commun (Camb) 2000. [DOI: 10.1039/b001586p] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Silverman RH, Dong B, Maitra RK, Player MR, Torrence PF. Selective RNA cleavage by isolated RNase L activated with 2-5A antisense chimeric oligonucleotides. Methods Enzymol 1999; 313:522-33. [PMID: 10595377 DOI: 10.1016/s0076-6879(00)13033-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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33
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Verheijen JC, Bayly SF, Player MR, Torrence PF, van der Marel GA, van Boom JH. 2-5A-PNA complexes: a novel class of antisense compounds. NUCLEOSIDES & NUCLEOTIDES 1999; 18:1485-6. [PMID: 10474229 DOI: 10.1080/07328319908044761] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This paper presents the fully automated solid phase synthesis of 2-5A-PNA hybrids. These stable antisense probes cause RNase L mediated hydrolysis of target RNA sequences.
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Cramer H, Geselowitz DA, Torrence PF. Using fluorescence resonance energy transfer (FRET) for measuring 2-5A analogues ability to activate RNase L. NUCLEOSIDES & NUCLEOTIDES 1999; 18:1523-5. [PMID: 10474231 DOI: 10.1080/07328319908044776] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The development of a method for measuring the ability of 2-5A analogues to activate the cleavage of an oligoribonucleotide substrate by RNase L is described. This method is based on fluorescence resonance energy transfer. The method is easily performed with 96-well plates, allowing for quantitative high-throughput analyses of 2-5A analogues under different reaction conditions.
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35
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Torrence PF. 2-5A-antisense chimeras: inhibitors of respiratory syncytial virus infection. CURRENT OPINION IN MOLECULAR THERAPEUTICS 1999; 1:307-15. [PMID: 11713795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
A new approach to the chemical control of respiratory syncytial virus infection is reviewed in the context of the biology of the virus and previous treatment approaches. Conjugation of the interferon action mediator, 2',5'-oligoadenylate (2-5A), to antisense agents provides a strategy for the selective ablation of RNA. This application of this technology to respiratory syncytial virus has provided a potent selective inhibitor of virus replication.
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MESH Headings
- 2',5'-Oligoadenylate Synthetase/genetics
- 2',5'-Oligoadenylate Synthetase/metabolism
- Adenine Nucleotides/chemistry
- Adenine Nucleotides/pharmacology
- Adenosine Triphosphate/metabolism
- Antisense Elements (Genetics)/chemistry
- Antisense Elements (Genetics)/pharmacology
- Antiviral Agents/pharmacology
- Child
- Child, Preschool
- Computer Simulation
- Drug Design
- Endoribonucleases/metabolism
- Enzyme Induction
- Humans
- Infant
- Interferons/physiology
- Models, Molecular
- Oligoribonucleotides/chemistry
- Oligoribonucleotides/pharmacology
- RNA, Double-Stranded/antagonists & inhibitors
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/metabolism
- RNA, Viral/antagonists & inhibitors
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Respiratory Syncytial Virus Infections/drug therapy
- Respiratory Syncytial Viruses/drug effects
- Respiratory Syncytial Viruses/genetics
- Respiratory Syncytial Viruses/physiology
- Substrate Specificity
- Virus Replication/drug effects
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36
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Cramer H, Player MR, Torrence PF. Discrimination between ribonuclease H- and ribonuclease L-mediated RNA degradation by 2'-O-methylated 2-5A-antisense oligonucleotides. Bioorg Med Chem Lett 1999; 9:1049-54. [PMID: 10230638 DOI: 10.1016/s0960-894x(99)00134-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
2',5'-Oligoadenylate (2-5A) antisense chimeric oligonucleotides were synthesized containing varying 2'-O-methyl-ribonucleotide substitution patterns in the antisense domain. The ability of these composite oligonucleotides to mediate RNase H- and RNase L-catalyzed RNA degradation showed that these two enzymes have different activation requirements.
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Barnard DL, Sidwell RW, Xiao W, Player MR, Adah SA, Torrence PF. 2-5A-DNA conjugate inhibition of respiratory syncytial virus replication: effects of oligonucleotide structure modifications and RNA target site selection. Antiviral Res 1999; 41:119-34. [PMID: 10320045 DOI: 10.1016/s0166-3542(99)00005-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To define more fully the conditions for 2-5A-antisense inhibition of respiratory syncytial virus (RSV), relationships between 2-5A antisense oligonucleotide structure and the choice of RNA target sites to inhibition of RSV replication have been explored. The lead 2-5A-antisense chimera for this study was the previously reported NIH8281 that targets the RSV M2 RNA. We have confirmed and extended the earlier study by showing that NIH8281 inhibited RSV strain A2 replication in a variety of antiviral assays, including virus yield reduction assays performed in monkey (EC90 = 0.02 microM) and human cells (EC90 = microM). This 2-5A-antisense chimera also inhibited other A strains, B strains and bovine RSV in cytopathic effect inhibition and Neutral Red Assays (EC50 values = 0.1-1.6 microM). The 2'-O-methylation modification of NIH8281 to increase affinity for the complementary RNA and provide nuclease resistance, the introduction of phosphothioate groups in the antisense backbone to enhance resistance to exo- and endonucleases, and the addition of cholesterol to the 3'-terminus of the antisense oligonucleotide to increase cellular uptake, all resulted in loss of activity. Of the antisense chimeras targeting other RSV mRNAs (NS1, NS2, P, M. G, F, and L), only those complementary to L mRNA were inhibitory. These results suggest that lower abundance mRNAs may be the best targets for 2-5A-antisense; moreover, the active 2-5A antisense chimeras in this study may serve as useful guides for the development of compounds with improved stability, uptake and anti-RSV activity.
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Player MR, Torrence PF. Phosphorothioate oligodeoxyribonucleotides inhibit ribonuclease L thereby disabling a mechanism of interferon action. Bioorg Med Chem Lett 1999; 9:891-4. [PMID: 10206556 DOI: 10.1016/s0960-894x(99)00099-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Phosphorothioate oligodeoxyribonucleotides were found to be inhibitors of the 2-5A-dependent RNase L. Inhibitory potency depended upon the chain length of the phosphorothioate oligonucleotide and was dependent on the phosphorothioate substitution pattern, but was not substantially base-dependent.
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Verheijen JC, van der Marel GA, van Boom JH, Bayly SF, Player MR, Torrence PF. 2,5-oligoadenylate-peptide nucleic acids (2-5A-PNAs) activate RNase L. Bioorg Med Chem 1999; 7:449-55. [PMID: 10220031 DOI: 10.1016/s0968-0896(98)00258-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
To potentiate the 2-5A (2',5'-oligoadenylate)-antisense and peptide nucleic acid (PNA) approaches to regulation of gene expression, composite molecules were generated containing both 2-5A and PNA moieties. 2-5A-PNA adducts were synthesized using solid-phase techniques. Highly cross-linked polystyrene beads were functionalized with glycine tethered through a p-hydroxymethylbenzoic acid linker and the PNA domain of the chimeric oligonucleotide analogue was added by sequential elongation of the amino terminus with the monomethoxytrityl protected N-(2-aminoethyl)-N-(adenin-1-ylacetyl)glycinate. Transition to the 2-5A domain was accomplished by coupling of the PNA chain to dimethoxytrityl protected N-(2-hydroxyethyl)-N-(adenin-1-ylacetyl)glycinate. Finally, (2-cyanoethyl)-N,N-diisopropyl-4-O-(4,4-dimethoxytrityl)butylphosphor amidite and the corresponding (2-cyanoethyl)-N,N-diisopropylphosphoramidite of 5-O-(4,4'-dimethoxytrityl)-3-O-(tert-butyldimethylsilyl)-N6-benzoyladeno sine were the synthons employed to add the 2 butanediol phosphate linkers and the four 2',5'-linked riboadenylates. The 5'-phosphate moiety was introduced with 2-[[2-(4,4'-dimethoxytrityloxy)ethyl]sulfonyl]ethyl-(2-cyanoethyl) -N,N-diisopropylphosphoramidite. Deprotection with methanolic NH3 and tetraethylammonium fluoride afforded the desired products, 2-SA-pnaA4, 2-5A-pnaA8 and 2-5A-pnaA12. When evaluated for their ability to cause the degradation of two different RNA substrates by the 2-5A-dependent RNase L, these new 2-5A-PNA conjugates were found to be potent RNase L activators. The union of 2-5A and PNA presents fresh opportunities to explore the biological and therapeutic implications of these unique approaches to antisense.
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Kitade Y, Wakana M, Terai SI, Tsuboi T, Nakanishi M, Yatome C, Dong B, Silverman RH, Torrence PF. 2-Bromoadenosine-Substituted 2′,5′-Oligoadenylates Modulate Binding and Activation Abilities of Human Recombinant RNase L. ACTA ACUST UNITED AC 1998. [DOI: 10.1080/07328319808004320] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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41
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Maran A, Waller CF, Paranjape JM, Li G, Xiao W, Zhang K, Kalaycio ME, Maitra RK, Lichtin AE, Brugger W, Torrence PF, Silverman RH. 2',5'-Oligoadenylate-antisense chimeras cause RNase L to selectively degrade bcr/abl mRNA in chronic myelogenous leukemia cells. Blood 1998; 92:4336-43. [PMID: 9834240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
We report an RNA targeting strategy, which selectively degrades bcr/abl mRNA in chronic myelogenous leukemia (CML) cells. A 2', 5'-tetraadenylate activator (2-5A) of RNase L was chemically linked to oligonucleotide antisense directed against either the fusion site or against the translation start sequence in bcr/abl mRNA. Selective degradation of the targeted RNA sequences was demonstrated in assays with purified RNase L and decreases of p210(bcr/abl) kinase activity levels were obtained in the CML cell line, K562. Furthermore, the 2-5A-antisense chimeras suppressed growth of K562, while having substantially reduced effects on the promyelocytic leukemia cell line, HL60. Findings were extended to primary CML cells isolated from bone marrow of patients. The 2-5A-antisense treatments both suppressed proliferation of the leukemia cells and selectively depleted levels of bcr/abl mRNA without affecting levels of beta-actin mRNA, determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The specificity of this approach was further shown with control oligonucleotides, such as chimeras containing an inactive dimeric form of 2-5A, antisense lacking 2-5A, or chimeras with altered sequences including several mismatched nucleotides. The control oligonucleotides had either reduced or no effect on CML cell growth and bcr/abl mRNA levels. These findings show that CML cell growth can be selectively suppressed by targeting bcr/abl mRNA with 2-5A-antisense for decay by RNase L and suggest that these compounds should be further explored for their potential as ex vivo purging agents of autologous hematopoietic stem cell transplants from CML patients.
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MESH Headings
- Adenine Nucleotides/genetics
- Adenine Nucleotides/pharmacology
- Adenine Nucleotides/therapeutic use
- Endoribonucleases/genetics
- Endoribonucleases/pharmacology
- Enzyme Activation/genetics
- Fusion Proteins, bcr-abl/antagonists & inhibitors
- Fusion Proteins, bcr-abl/genetics
- Gene Expression Regulation, Neoplastic
- Humans
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Oligonucleotides, Antisense/genetics
- Oligonucleotides, Antisense/pharmacology
- Oligonucleotides, Antisense/therapeutic use
- Oligoribonucleotides/genetics
- Oligoribonucleotides/pharmacology
- Oligoribonucleotides/therapeutic use
- RNA, Messenger/antagonists & inhibitors
- RNA, Messenger/genetics
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/pharmacology
- Recombinant Fusion Proteins/therapeutic use
- Tumor Cells, Cultured
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Player MR, Barnard DL, Torrence PF. Potent inhibition of respiratory syncytial virus replication using a 2-5A-antisense chimera targeted to signals within the virus genomic RNA. Proc Natl Acad Sci U S A 1998; 95:8874-9. [PMID: 9671772 PMCID: PMC21170 DOI: 10.1073/pnas.95.15.8874] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The 2-5A system is a recognized mechanistic component of the antiviral action of interferon. Interferon-induced 2-5A synthetase generates 2-5A, which, in turn, activates the latent constitutive RNase L that degrades viral RNA. Chemical conjugation of 2-5A to an antisense oligonucleotide can target the 2-5A-dependent RNase L to the antisense-specified RNA and effect its selective destruction. Such a 2-5A-antisense chimera (NIH351) has been developed that targets a consensus sequence within the respiratory syncytial virus (RSV) genomic RNA. NIH351 was 50- to 90-fold more potent against RSV strain A2 than was ribavirin, the presently approved drug for clinical management of RSV infection. It was similarly active against a variety of RSV strains of both A and B subgroups and possessed a cell culture selectivity index comparable to ribavirin. In addition, the anti-RSV activity of NIH351 was shown to be virus-specific and a result of a true antisense effect, because a scrambled nucleotide sequence in the antisense domain of NIH351 caused a significant decrease in antiviral activity. The 2-5A system's RNase L was implicated in the mechanism of action of NIH351 because a congener with a disabled 2-5A moiety was of greatly reduced anti-RSV effectiveness. These findings represent an innovative approach to the control of RSV replication.
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Player MR, Wondrak EM, Bayly SF, Torrence PF. Ribonuclease L, a 2-5A-dependent enzyme: purification to homogeneity and assays for 2-5A binding and catalytic activity. Methods 1998; 15:243-53. [PMID: 9735309 DOI: 10.1006/meth.1998.0628] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
RNase L is a latent endonuclease found in reptiles, birds, and mammals. It is activated by the 2',5'-phosphodiester-linked oligoadenylates called 2-5A and has been implicated in the mechanism of action of interferon, as well as in a variety of other biological phenomena such as apoptosis. Covalent linkage of 2-5A to antisense oligonucleotides permits recruitment of RNase L for enhancement of antisense action. The purification of RNase L described herein and the assays for its detection and activation will help to provide further mechanistic details on how this unique nuclease functions and what its biochemical roles may be. In addition, such assays will facilitate the screening of 2-5A-antisense congeners for exploration of the potential therapeutic applications of RNase L.
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Player MR, Maitra RK, Silverman RH, Torrence PF. Targeting RNase L to human immunodeficiency virus RNA with 2-5A-antisense. Antivir Chem Chemother 1998; 9:225-31. [PMID: 9875401 DOI: 10.1177/095632029800900303] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In an attempt to develop a lead for the application of 2-5A-antisense to the targeted destruction of human immunodeficiency virus (HIV) RNA, specific target sequences within the HIV mRNAs were identified by analysis of the theoretical secondary structure. 2-5A-antisense chimeras were chosen against a total of 11 different sequences: three in the gag mRNA, three in the rev mRNA and five in the tat mRNA. 2-5A-antisense chimera synthesis was accomplished using solid-phase phosphoramidite chemistry. These chimeras were evaluated for their activity in a cell-free assay system using purified recombinant human RNase L to effect cleavage of 32P-labelled RNA transcripts of plasmids derived from HIV NL4-3. This screening revealed that of the three 2-5A-antisense chimeras targeted against gag mRNA, only one had significant HIV RNA cleavage activity, approximately 10-fold-reduced compared to the parent 2-5A tetramer and comparable to that reported for the prototypical 2-5A-anti-PKR chimera, targeted against PKR mRNA. The cleavage activity of this chimera was specific, since a scrambled antisense domain chimera and a chimera without the key 5'-monophosphate moiety were both inactive. The 10 other 2-5A-antisense chimeras against tat and rev had significantly less activity. These results imply that HIV gag RNA, like PKR RNA and a model HIV tat-oligoA-vif RNA, can be cleaved using the 2-5A-antisense approach. The results further imply that not all regions of a potential RNA target are accessible to the 2-5A-antisense approach.
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Player MR, Torrence PF. The 2-5A system: modulation of viral and cellular processes through acceleration of RNA degradation. Pharmacol Ther 1998; 78:55-113. [PMID: 9623881 PMCID: PMC7157933 DOI: 10.1016/s0163-7258(97)00167-8] [Citation(s) in RCA: 227] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The 2-5A system is an RNA degradation pathway that can be induced by the interferons (IFNs). Treatment of cells with IFN activates genes encoding several double-stranded RNA (dsRNA)-dependent synthetases. These enzymes generate 5'-triphosphorylated, 2',5'-phosphodiester-linked oligoadenylates (2-5A) from ATP. The effects of 2-5A in cells are transient since 2-5A is unstable in cells due to the activities of phosphodiesterase and phosphatase. 2-5A activates the endoribonuclease 2-5A-dependent RNase L, causing degradation of single-stranded RNA with moderate specificity. The human 2-5A-dependent RNase is an 83.5 kDa polypeptide that has little, if any, RNase activity, unless 2-5A is present. 2-5A binding to RNase L switches the enzyme from its off-state to its on-state. At least three 2',5'-linked oligoadenylates and a single 5'-phosphoryl group are required for maximal activation of the RNase. Even though the constitutive presence of 2-5A-dependent RNase is observed in nearly all mammalian cell types, cellular amounts of 2-5A-dependent mRNA and activity can increase after IFN treatment. One well-established role of the 2-5A system is as a host defense against some types of viruses. Since virus infection of cells results in the production and secretion of IFNs, and since dsRNA is both a frequent product of virus infection and an activator of 2-5A synthesis, the replication of encephalomyocarditis virus, which produces dsRNA during its life cycle, is greatly suppressed in IFN-treated cells as a direct result of RNA decay by the activated 2-5A-dependent RNase. This review covers the organic chemistry, enzymology, and molecular biology of 2-5A and its associated enzymes. Additional possible biological roles of the 2-5A system, such as in cell growth and differentiation, human immunodeficiency virus replication, heat shock, atherosclerotic plaque, pathogenesis of Type I diabetes, and apoptosis, are presented.
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Xiao W, Li G, Player MR, Maitra RK, Waller CF, Silverman RH, Torrence PF. Nuclease-resistant composite 2',5'-oligoadenylate-3', 5'-oligonucleotides for the targeted destruction of RNA: 2-5A-iso-antisense. J Med Chem 1998; 41:1531-9. [PMID: 9554886 DOI: 10.1021/jm970841p] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A new modification of 2-5A-antisense, 2-5A-iso-antisense, has been developed based on a reversal of the direction of the polarity of the antisense domain of a 2-5A-antisense composite nucleic acid. This modification was able to anneal with its target RNA as well as the parental 2-5A-antisense chimera. The 2-5A-iso-antisense oligonucleotide displayed enhanced resistance to degradation by 3'-exonuclease enzyme activity such as that represented by snake venom phosphodiesterase and by that found in human serum. 2-5A-Iso-antisense was able to effect the degradation of a synthetic nontargeted substrate, [5'-32P]pC11U2C7, and two targeted RNAs, PKR and BCR mRNAs, in a cell-free system containing purified recombinant human 2-5A-dependent RNase L. These results demonstrated that the novel structural modification represented by 2-5A-iso-antisense provided a stabilized biologically active formulation of the 2-5A-antisense strategy.
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47
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Player MR, Kalinichenko EN, Podkopaeva TL, Mikhailopulo IA, Seela F, Torrence PF. Dissection of the roles of adenine ring nitrogen (N-1) and exocyclic amino (N-6) moieties in the interaction of 2-5A with RNase L. Biochem Biophys Res Commun 1998; 245:430-4. [PMID: 9571169 DOI: 10.1006/bbrc.1998.8451] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To elucidate further the roles played by the adenine bases in the interaction of RNase L (EC 3.1.2.6) with the 2',5'-oligoadenylate 2-5A, p5'A2'(p5'A2')np5' A, a series of sequence-specific 1-deazaadenosine (c1A)-substituted analogues were synthesized and evaluated for their ability to bind to and activate human RNase L in comparison to earlier reported inosine-substituted congeners of 2-5A. Substitution of only the 5'-terminal adenosine of p5'A2'p5'A2 p5 A with c1A afforded an analogue with strongly diminished RNase L binding and activation ability, while replacement of the second or middle adenosine of p5 A2' p5'A2'p5' A had only a modest effect. In distinct contrast to p5'A2'p5'A2'p5'I, the c1A analogue with the third or 2'-terminal adenosine replacement approached parent p5' A2'p5'A2'p5' A in RNase L activation ability. These results permitted a further dissection of the role of various nucleotidic functional groups in the interaction of 2-5A with RNase L: specifically, that the 5'-terminal adenosine purine N-1 moiety is key for binding to RNase L, while the 2'-terminal adenosine N-6 exocyclic amino group is critical for RNase L activation.
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Player MR, Xiao W, Cramer H, Torrence PF. Methods for the characterization of phosphatase-stabilized 2-5A-antisense chimeras. Bioconjug Chem 1998; 9:137-42. [PMID: 9460557 DOI: 10.1021/bc970157p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We have developed chromatographic and spectrophotometric assays for determining the degree of thiolation in phosphatase-resistant 5'-monothiophosphate-capped 2-5A-antisense chimeras. Concomitantly, we have explored the reactivity of this 5'-monophosphorothioate moiety with reporter reagents such as 5-iodoacetomidofluorescein and 5,5'-dithiobis(2-nitrobenzoic acid). On the basis of these reactions, analyses for 5'-monothiophosphate-functionalized 2-5A-antisense chimeras were made possible. Kinetic experiments demonstrated that oligonucleotide backbone negative charge could retard mixed disulfide formation in the reaction of 5,5'-dithiobis(2-nitrobenzoic acid) with 5'-monothiophosphorylated 2-5A-antisense chimeras.
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Castelli JC, Hassel BA, Wood KA, Li XL, Amemiya K, Dalakas MC, Torrence PF, Youle RJ. A study of the interferon antiviral mechanism: apoptosis activation by the 2-5A system. J Exp Med 1997; 186:967-72. [PMID: 9294150 PMCID: PMC2199051 DOI: 10.1084/jem.186.6.967] [Citation(s) in RCA: 208] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The 2-5A system contributes to the antiviral effect of interferons through the synthesis of 2-5A and its activation of the ribonuclease, RNase L. RNase L degrades viral and cellular RNA after activation by unique, 2'-5' phosphodiester-linked, oligoadenylates [2-5A, (pp)p5' A2'(P5'A2')]n, n >=2. Because both the 2-5A system and apoptosis can serve as viral defense mechanisms and RNA degradation occurs during both processes, we investigated the potential role of RNase L in apoptosis. Overexpression of human RNase L by an inducible promoter in NIH3T3 fibroblasts decreased cell viability and triggered apoptosis. Activation of endogenous RNase L, specifically with 2-5A or with dsRNA, induced apoptosis. Inhibition of RNase L with a dominant negative mutant suppressed poly (I).poly (C)-induced apoptosis in interferon-primed fibroblasts. Moreover, inhibition of RNase L suppressed apoptosis induced by poliovirus. Thus, increased RNase L levels induced apoptosis and inhibition of RNase L activity blocked viral-induced apoptosis. Apoptosis may be one of the antiviral mechanisms regulated by the 2-5A system.
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Li G, Xiao W, Torrence PF. Synthesis and properties of second-generation 2-5A-antisense chimeras with enhanced resistance to exonucleases. J Med Chem 1997; 40:2959-66. [PMID: 9288179 DOI: 10.1021/jm970227d] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In order to stabilize 2-5A-antisense chimeras to exonucleases, we have synthesized chimeric oligonucleotides in which the last phosphodiester bond at the 3'-terminus of the antisense domain was inverted from the usual 3',5'-linkage to a 3',3'-linkage. The preparation of such analogues was accomplished through standard phosphoramidite chemistry with the use of a controlled pore glass solid support with a nucleoside attached through its 5'-hydroxyl, thereby permitting elongation at the 3'-hydroxyl. The structures of such terminally inverted linkage chimeras of the general formula pA4-[pBu]2-(pdNn3'-3'dN) were corroborated by a combination of snake venom phosphodiesterase digestion in the presence or absence of bacterial alkaline phosphatase. Most characteristically, the presence of the 3'-terminal-inverted phosphodiester linkage produced an unnatural dinucleotide of general composition dN3'p3'dM. These structures could be confirmed by independent synthesis and fast atom bombardment mass spectroscopy (FAB). 2-5A-Antisense chimeras of this structural class, pA4-[pBu]2-(pdNn'3-3'dN), were 5-6-fold more stable than their unmodified congeners, pA4-[pBu]2-(pdN)n, to degradation by a representative phosphodiesterase from snake venom. In 10% human serum, the new 2-5A-antisense chimeras, pA4-[pBu]2-(pdNn3'-3'dN), possessed a half-life that was 28-fold longer than that of the unmodified chimeras. These results provide entry to a second generation of 2-5A-antisense chimeras.
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