Mechanistic analysis of the enhanced RNAi activity by 6-mCEPh-purine at the 5′ end of the siRNA guide strand
- 1Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- 2Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- 3Research Function Unit, R&D Division, Kyowa Kirin Co. Ltd., Chiyoda-ku, Tokyo 100-0004, Japan
- 4Institut de Génétique Humaine, UMR 9002 CNRS and Université de Montpellier, 34396 Montpellier, France
- Corresponding author: tomari{at}IQB.u-tokyo.ac.jp
Abstract
A key approach for improving siRNA efficacy is chemical modifications. Through an in silico screening of modifications at the 5′-end nucleobase of the guide strand, an adenine-derived compound called 6-(3-(2-carboxyethyl)phenyl)-purine (6-mCEPh-purine) was identified to improve the RNAi activity in cultured human cells and in vivo mouse models. Nevertheless, it remains unclear how this chemical modification enhances the siRNA potency. Here, we used a series of biochemical approaches to quantitatively evaluate the effect of the 6-mCEPh-purine modification at each step in the assembly of the RNAi effector complex called RISC. We found that the modification improves the formation of mature RISC at least in two different ways, by fixing the loading orientation of siRNA duplexes and increasing the stability of mature RISC after passenger strand ejection. Our data will provide a molecular platform for further development of chemically modified siRNA drugs.
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Article is online at http://www.rnajournal.org/cgi/doi/10.1261/rna.073775.119.
- Received October 25, 2019.
- Accepted October 15, 2020.
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