Stereochemical bias introduced during RNA synthesis modulates the activity of phosphorothioate siRNAs.
An established means of improving the pharmacokinetics properties of oligoribonucleotides (ORNs) is to exchange their phosphodiester linkages for phosphorothioates (PSs). However, this strategy has not been pursued for small interfering RNAs (siRNAs), possibly because of sporadic reports that PS siRNAs show reduced inhibitory activity. The PS group is chiral at phosphorous (Rp/Sp centres), and conventional solid-phase synthesis of PS ORNs produces a population of diastereoisomers. Here we show that the choice of the activating agent for the synthesis of a PS ORN influences the Rp/Sp ratio of PS linkages throughout the strand. Furthermore, PS siRNAs composed of ORNs with a higher fraction of Rp centres show greater resistance to nucleases in serum and are more effective inhibitors in cells than their Sp counterparts. The finding that a stereochemically biased population of ORN diastereoisomers can be synthesized and exploited pharmacologically is important because uniform PS modification of siRNAs may provide a useful compromise of their pharmacokinetics and pharmacodynamics properties in RNAi therapeutics.
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg-4, CH-8093 Zürich, Switzerland.
Hartmut
H
Jahns
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg-4, CH-8093 Zürich, Switzerland.
Martina
M
Roos
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg-4, CH-8093 Zürich, Switzerland.
Jochen
J
Imig
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg-4, CH-8093 Zürich, Switzerland.
Fabienne
F
Baumann
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg-4, CH-8093 Zürich, Switzerland.
Yuluan
Y
Wang
Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
Ryan
R
Gilmour
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg-4, CH-8093 Zürich, Switzerland.
Jonathan
J
Hall
D015152:Blotting, Northern; D006367:HeLa Cells; D006801:Humans; D007536:Isomerism; D008156:Luciferases; D015394:Molecular Structure; D054735:Phosphorothioate Oligonucleotides / Q000378:metabolism* / Q000493:pharmacokinetics; D012313:RNA / Q000096:biosynthesis* / Q000737:chemistry*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism* / Q000493:pharmacokinetics
D054735:Phosphorothioate Oligonucleotides; D034741:RNA, Small Interfering; D012313:RNA; D008156:Luciferases