UMMS Affiliation

RNA Therapeutics Institute; Program in Molecular Medicine; Department of Medicine

Publication Date


Document Type



Biochemistry | Enzymes and Coenzymes | Nucleic Acids, Nucleotides, and Nucleosides | Organic Chemicals | Structural Biology


5-Vinylphosphonate modification of siRNAs protects them from phosphatases, and improves silencing activity. Here, we show that 5-vinylphosphonate confers novel properties to siRNAs. Specifically, 5-vinylphosphonate (i) increases siRNA accumulation in tissues, (ii) extends duration of silencing in multiple organs and (iii) protects siRNAs from 5-to-3 exonucleases. Delivery of conjugated siRNAs requires extensive chemical modifications to achieve stability in vivo. Because chemically modified siRNAs are poor substrates for phosphorylation by kinases, and 5-phosphate is required for loading into RNA-induced silencing complex, the synthetic addition of a 5-phosphate on a fully modified siRNA guide strand is expected to be beneficial. Here, we show that synthetic phosphorylation of fully modified cholesterol-conjugated siRNAs increases their potency and efficacy in vitro, but when delivered systemically to mice, the 5-phosphate is removed within 2 hours. The 5-phosphate mimic 5-(E)-vinylphosphonate stabilizes the 5 end of the guide strand by protecting it from phosphatases and 5-to-3 exonucleases. The improved stability increases guide strand accumulation and retention in tissues, which significantly enhances the efficacy of cholesterol-conjugated siRNAs and the duration of silencing in vivo. Moreover, we show that 5-(E)-vinylphosphonate stabilizes 5 phosphate, thereby enabling systemic delivery to and silencing in kidney and heart.

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Copyright The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited.

DOI of Published Version



Nucleic Acids Res. 2017 Jul 27;45(13):7581-7592. doi: 10.1093/nar/gkx507. Link to article on publisher's site

Journal/Book/Conference Title

Nucleic acids research

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PubMed ID


Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License