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Liang Y, Willey S, Chung YC, Lo YM, Miao S, Rundell S, Tu LC, Bong D. Intracellular RNA and DNA tracking by uridine-rich internal loop tagging with fluorogenic bPNA. Nat Commun 2023; 14:2987. [PMID: 37225690 DOI: 10.1038/s41467-023-38579-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 05/05/2023] [Indexed: 05/26/2023] Open
Abstract
The most widely used method for intracellular RNA fluorescence labeling is MS2 labeling, which generally relies on the use of multiple protein labels targeted to multiple RNA (MS2) hairpin structures installed on the RNA of interest (ROI). While effective and conveniently applied in cell biology labs, the protein labels add significant mass to the bound RNA, which potentially impacts steric accessibility and native RNA biology. We have previously demonstrated that internal, genetically encoded, uridine-rich internal loops (URILs) comprised of four contiguous UU pairs (8 nt) in RNA may be targeted with minimal structural perturbation by triplex hybridization with 1 kD bifacial peptide nucleic acids (bPNAs). A URIL-targeting strategy for RNA and DNA tracking would avoid the use of cumbersome protein fusion labels and minimize structural alterations to the RNA of interest. Here we show that URIL-targeting fluorogenic bPNA probes in cell media can penetrate cell membranes and effectively label RNAs and RNPs in fixed and live cells. This method, which we call fluorogenic U-rich internal loop (FLURIL) tagging, was internally validated through the use of RNAs bearing both URIL and MS2 labeling sites. Notably, a direct comparison of CRISPR-dCas labeled genomic loci in live U2OS cells revealed that FLURIL-tagged gRNA yielded loci with signal to background up to 7X greater than loci targeted by guide RNA modified with an array of eight MS2 hairpins. Together, these data show that FLURIL tagging provides a versatile scope of intracellular RNA and DNA tracking while maintaining a light molecular footprint and compatibility with existing methods.
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Affiliation(s)
- Yufeng Liang
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH, USA
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Sydney Willey
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA
| | - Yu-Chieh Chung
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA
| | - Yi-Meng Lo
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH, USA
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Shiqin Miao
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH, USA
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Sarah Rundell
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH, USA
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Li-Chun Tu
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA.
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA.
| | - Dennis Bong
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH, USA.
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
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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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Devari S, Bhunia D, Bong D. Synthesis of Bifacial Peptide Nucleic Acids with Diketopiperazine Backbones. Synlett 2022; 33:965-968. [PMID: 35874045 PMCID: PMC9306277 DOI: 10.1055/a-1802-6873] [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] [Indexed: 10/18/2022]
Abstract
We report a synthesis of bifacial peptide nucleic acids (bPNAs) with novel diketopiperazine (DKP) backbones that display unnatural melamine (M) bases, as well as native bases. To examine the structure-function scope of DKP bPNAs, we synthesized a set of bPNAs by using diaminopropionic acid, diaminobutyric acid, ornithine, and lysine derivatives to display the base-tripling motifs, which result in one, two, three, or four carbons linking the alpha carbon to the side-chain amine. Thermal denaturation of DNA hybrids with these bPNAs revealed that the optimal side-chain linkage was four carbons, corresponding to the lysine derivative. Accordingly, monomers displaying two bases per side-chain were prepared through double reductive alkylation of the ε-amine of Fmoc-lysine with acetaldehyde derivatives of adenine, cytidine, uridine, and melamine. With these building blocks in hand, DKP bPNAs were prepared to display a combination of native and synthetic (melamine) bases. Preliminary melting studies indicate binding signatures of cytidine- and melamine-displaying bPNAs to T-rich DNAs of noncanonical structure, though full characterization of this behavior is ongoing. The convenient and potentially scalable method described enables rapid access to DNA-binding scaffolds of low (<1 kD) molecular weight and previously established cell permeability. We expect that this straightforward and efficient approach to nucleic acid binders will enable studies on noncanonical nucleic acid hybridization.
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Affiliation(s)
- Shekaraiah Devari
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, USA
| | - Debmalya Bhunia
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, USA
| | - Dennis Bong
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, USA
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Munyaradzi O, Rundell S, Bong D. Impact of bPNA Backbone Structural Constraints and Composition on Triplex Hybridization with DNA. Chembiochem 2022; 23:e202100707. [PMID: 35167719 PMCID: PMC9136932 DOI: 10.1002/cbic.202100707] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/18/2022] [Indexed: 11/07/2022]
Abstract
We report herein a study on the impact of bifacial peptide nucleic acid (bPNA) amino acid composition and backbone modification on DNA binding. A series of bPNA backbone variants with identical net charge were synthesized to display either 4 or 6 melamine (M) bases. These bases form thymine-melamine-thymine (TMT) base-triples, resulting in triplex hybrid stem structures with T-rich DNAs. Analyses of 6 M bPNA-DNA hybrids suggested that hybrid stability was linked to amino acid secondary structure propensities, prompting a more detailed study in shorter 4 M bPNAs. We synthesized 4 M bPNAs predisposed to adopt helical secondary structure via helix-turn nucleation in 7-residue bPNAs using double-click covalent stapling. Generally, hybrid stability improved upon stapling, but amino acid composition had a more significant effect. We also pursued an alternative strategy for bPNA structural preorganization by incorporation of residues with strong backbone amide conformational preferences such as 4R- and 4S-fluoroprolines. Notably, these derivatives exhibited an additional improvement in hybrid stability beyond both unsubstituted proline bPNA analogues and the helically patterned bPNAs. Overall, these findings demonstrate the tunability of bPNA-DNA hybrid stability through bPNA backbone structural propensities and amino acid composition.
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Affiliation(s)
- Oliver Munyaradzi
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio, 43210, USA
| | - Sarah Rundell
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio, 43210, USA
| | - Dennis Bong
- Department of Chemistry & Biochemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio, 43210, USA
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