1
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Lee ETT, Sato Y, Ujuagu AF, Nishizawa S. Forced intercalation-induced light-up peptides as fluorogenic indicators for the HIV-1 TAR RNA-ligand assay. Analyst 2024; 149:4179-4186. [PMID: 38860915 DOI: 10.1039/d4an00530a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2024]
Abstract
Fluorescence indicators capable of binding to human immunodeficiency virus-1 (HIV-1) trans-activation responsive (TAR) RNA are powerful tools for the exploratory studies of the identification of anti-HIV drug candidates. This work presents a new design strategy for fluorogenic indicators with a transactivator of transcription (Tat)-derived peptide based on the forced intercalation of thiazole orange (TO) dyes (FIT). The developed 9-mer FIT peptide (RKKRR-TO-RRR: named FiLuP) features the TO unit integrated onto a Dap (2,3-diaminopropionic acid) residue in the middle of the Tat peptide sequence; the Q (glutamic acid) residue in the Tat peptide (RKKRR-Q-RRR) is replaced with TO as if it were an amino acid surrogate. This facilitates a significant light-up response (450-fold at λem = 541 nm, Φfree = 0.0057, and Φbound = 0.61) upon binding to TAR RNA. The response of FiLuP is highly selective to TAR RNA over other non-cognate RNAs, and FiLuP maintains strong binding affinity (Kd = 1.0 ± 0.6 nM). Significantly, in contrast to previously developed Tat peptide-based FRET probes, FiLuP is able to discriminate between "competitive" and "noncompetitive" inhibitors when used in the fluorescence indicator displacement (FID) assay. The FID assay under stringent screening conditions is also possible, enabling super-strong competitive binders toward TAR RNA to be sieved out.
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Affiliation(s)
- En Ting Tabitha Lee
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
| | - Yusuke Sato
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
| | - Akunna F Ujuagu
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
| | - Seiichi Nishizawa
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
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2
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Rahman MM, Ryan CA, Tessier BR, Rozners E. Peptide nucleic acids (PNAs) control function of SARS-CoV-2 frameshifting stimulatory element trough PNA-RNA-PNA triplex formation. Heliyon 2024; 10:e33914. [PMID: 39071573 PMCID: PMC11282987 DOI: 10.1016/j.heliyon.2024.e33914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Revised: 05/30/2024] [Accepted: 06/28/2024] [Indexed: 07/30/2024] Open
Abstract
The highly structured nature of the SARS-CoV-2 genome provides many promising antiviral drug targets. One particularly promising target is a cis-acting RNA pseudoknot found within a critical region called the frameshifting stimulatory element (FSE). In this study, peptide nucleic acids (PNAs) binding to stem 2 of FSE RNA inhibited protein translation and frameshifting, as measured by a cell-free dual luciferase assay, more effectively than PNAs binding to stem 1, stem 3, or the slippery site. Surprisingly, simple antisense PNAs were stronger disruptors of frameshifting than PNA tail-clamps, despite higher thermal stability of the PNA-RNA-PNA triplexes formed by the latter. Another unexpected result was a strong and sequence non-specific enhancement of frameshifting inhibition when using a cationic triplex-forming PNA in conjunction with an antisense PNA targeting key regions of the frameshifting element. Our results illustrate both the potential and the challenges of using antisense PNAs to target highly structured RNAs, such as SARS-CoV-2 pseudoknots. While triplex forming PNAs, including PNA tail-clamps, are emerging as promising ligands for RNA recognition, the binding affinity enhancements when using cationic modifications in triplex-forming PNAs must be carefully balanced to avoid loss of sequence specificity in complex biological systems.
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Affiliation(s)
| | | | - Brandon R. Tessier
- Department of Chemistry, Binghamton University, The State University of New York, Binghamton, NY, 13902, United States
| | - Eriks Rozners
- Department of Chemistry, Binghamton University, The State University of New York, Binghamton, NY, 13902, United States
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3
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Katkevics M, MacKay JA, Rozners E. Triplex-forming peptide nucleic acids as emerging ligands to modulate structure and function of complex RNAs. Chem Commun (Camb) 2024; 60:1999-2008. [PMID: 38259187 PMCID: PMC10922694 DOI: 10.1039/d3cc05409h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Over the last three decades, our view of RNA has changed from a simple intermediate supporting protein synthesis to a major regulator of biological processes. In the expanding area of RNA research, peptide nucleic acid (PNA) is emerging as a promising ligand for triple-helical recognition of complex RNAs. As discussed in this feature article, the key advantages of PNAs are high sequence specificity and affinity for RNA (>10 fold higher than for DNA) that are difficult to achieve with small molecule ligands. Emerging studies demonstrate that triple-helical binding of PNAs can modulate biological function and control dynamic conformational equilibria of complex folded RNAs. These results suggest that PNA has a unique potential as a research tool and therapeutic compound targeting RNA. The remaining problems hampering advances in these directions are limitations of sequences that can be recognized by Hoogsteen triplexes (typically purine rich tracts), poor cellular uptake and bioavailability of PNA, and potential off-target effects in biological systems. Recent exciting studies are discussed that illustrate how synthetic nucleic acid chemistry provides innovative solutions for these problems.
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Affiliation(s)
- Martins Katkevics
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, LV-1006, Latvia
| | - James A MacKay
- Department of Chemistry and Biochemistry, Elizabethtown College, Elizabethtown, PA 17022, USA
| | - Eriks Rozners
- Department of Chemistry, Binghamton University, Binghamton, NY 13902, USA.
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4
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Kumpina I, Loubidi M, Rozners E. Comparison of 2-Aminopyridine and 4-Thiopseudisocytosine PNA Nucleobases for Hoogsteen Recognition of Guanosine in RNA. ACS OMEGA 2024; 9:7249-7254. [PMID: 38371848 PMCID: PMC10870399 DOI: 10.1021/acsomega.3c09775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 01/17/2024] [Accepted: 01/23/2024] [Indexed: 02/20/2024]
Abstract
Peptide nucleic acid (PNA) is emerging as a promising ligand for triple-helical recognition of folded biologically relevant RNA. Chemical modifications are actively being developed to achieve high affinity and sequence specificity under physiological conditions. In this study, we compared two modified PNA nucleobases, 2-aminopyridine (M) and 4-thiopseudisocytosine (L), as alternatives to protonated cytosine (unfavorable under physiological conditions), to form more stable triplets than C+·G-C. Both nucleobases formed M+·G-C and L·G-C triplets of similar stability; however, the L-modified PNAs showed somewhat reduced sequence specificity. In conclusion, M and L represent two alternative solutions to the problem of cytosine protonation in triple-helical recognition of RNA. In M, the pKa is increased to favor partial protonation, which improves solubility and cellular uptake of M-modified PNAs. In L, the sulfur substitution enhances favorable hydrophobic interactions, which may have advantages in avoiding off-target effects that may be caused by cationic modifications. However, our results showed that substituting Ms with Ls did not restore the sequence specificity of a PNA containing cationic groups.
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Affiliation(s)
- Ilze Kumpina
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Mohammed Loubidi
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Eriks Rozners
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
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5
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Talbott JM, Tessier BR, Harding EE, Walby GD, Hess KJ, Baskevics V, Katkevics M, Rozners E, MacKay JA. Improved Triplex-Forming Isoorotamide PNA Nucleobases for A-U Recognition of RNA Duplexes. Chemistry 2023; 29:e202302390. [PMID: 37647091 DOI: 10.1002/chem.202302390] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/24/2023] [Accepted: 08/30/2023] [Indexed: 09/01/2023]
Abstract
Four new isoorotamide (Io)-containing PNA nucleobases have been designed for A-U recognition of double helical RNA. New PNA monomers were prepared efficiently and incorporated into PNA nonamers for binding A-U in a PNA:RNA2 triplex. Isothermal titration calorimetry and UV thermal melting experiments revealed slightly improved binding affinity for singly modified PNA compared to known A-binding nucleobases. Molecular dynamics simulations provided further insights into binding of Io bases in the triple helix. Together, the data revealed interesting insights into binding modes including the notion that three Hoogsteen hydrogen bonds are unnecessary for strong selective binding of an extended nucleobase. Cationic monomer Io8 additionally gave the highest affinity observed for an A-binding nucleobase to date. These results will help inform future nucleobase design toward the goal of recognizing any sequence of double helical RNA.
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Affiliation(s)
- John M Talbott
- Department of Chemistry and Biochemistry, Elizabethtown College, Elizabethtown, PA 17022, USA
| | - Brandon R Tessier
- Department of Chemistry, Binghamton University, Binghamton, NY 13902, USA
| | - Emily E Harding
- Department of Chemistry and Biochemistry, Elizabethtown College, Elizabethtown, PA 17022, USA
| | - Grant D Walby
- Department of Chemistry and Biochemistry, Elizabethtown College, Elizabethtown, PA 17022, USA
| | - Kyle J Hess
- Department of Chemistry and Biochemistry, Elizabethtown College, Elizabethtown, PA 17022, USA
| | | | - Martins Katkevics
- Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, LV-1006, Latvia
| | - Eriks Rozners
- Department of Chemistry, Binghamton University, Binghamton, NY 13902, USA
| | - James A MacKay
- Department of Chemistry and Biochemistry, Elizabethtown College, Elizabethtown, PA 17022, USA
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Alavijeh NS, Serrano A, Peters MS, Wölper C, Schrader T. Design and Synthesis of Artificial Nucleobases for Sequence-Selective DNA Recognition within the Major Groove. Chem Asian J 2023; 18:e202300637. [PMID: 37616375 DOI: 10.1002/asia.202300637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 08/23/2023] [Indexed: 08/26/2023]
Abstract
We present the design and synthesis of artificial specific nucleobases, each one recognizing a single base pair within the major groove of duplex DNA. Computational calculations indicate that PNAs modified with these nucleobases enable the formation of highly stable triple helices with no sequence restrictions through multiple hydrogen bonding and π⋅⋅⋅π stacking interactions, without significantly widening the DNA double helix. New synthetic routes were developed to the structures of these fused heterocycles which have rarely been described in the literature. NMR titration experiments indicate specific hydrogen bonding at the Hoogsteen sites. The new building blocks allow the construction of four PNA monomers for each canonic base pair and their covalent connection to PNA oligomers. These can be designed complementary to any given DNA sequence. With high efficiency and relative simplicity of operation, the described methodologies and strategies hence form the basis for a new supramolecular ligand system targeting double-stranded DNA without strand invasion.
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Affiliation(s)
- Nahid S Alavijeh
- Department of Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany
| | - Alvaro Serrano
- Department of Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany
| | - Max S Peters
- Department of Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany
| | - Christoph Wölper
- Department of Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany
| | - Thomas Schrader
- Department of Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117, Essen, Germany
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7
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López-Tena M, Chen SK, Winssinger N. Supernatural: Artificial Nucleobases and Backbones to Program Hybridization-Based Assemblies and Circuits. Bioconjug Chem 2023; 34:111-123. [PMID: 35856656 DOI: 10.1021/acs.bioconjchem.2c00292] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The specificity and predictability of hybridization make oligonucleotides a powerful platform to program assemblies and networks with logic-gated responses, an area of research which has grown into a field of its own. While the field has capitalized on the commercial availability of DNA oligomers with its four canonical nucleobases, there are opportunities to extend the capabilities of the hardware with unnatural nucleobases and other backbones. This Topical Review highlights nucleobases that favor hybridizations that are empowering for assemblies and networks as well as two chiral XNAs than enable orthogonal hybridization networks.
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Affiliation(s)
- Miguel López-Tena
- University of Geneva, Department of Organic Chemistry, Faculty of Science, NCCR Chemical Biology, 30 Quai Ernest Ansermet, CH-1205 Geneva, Switzerland
| | - Si-Kai Chen
- University of Geneva, Department of Organic Chemistry, Faculty of Science, NCCR Chemical Biology, 30 Quai Ernest Ansermet, CH-1205 Geneva, Switzerland
| | - Nicolas Winssinger
- University of Geneva, Department of Organic Chemistry, Faculty of Science, NCCR Chemical Biology, 30 Quai Ernest Ansermet, CH-1205 Geneva, Switzerland
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