Solid-Phase Synthesis of Modified RNAs Containing Amide-Linked Oligoribonucleosides at Their 3′-End and Their Application to siRNA

Abstract

siRNAs against luciferase mRNA were modified with amide-linked oligoribonucleosides (amide-linked RNA) at their 3 ′-overhangs. Tm values of the modified siRNAs increased compared with that of the unmodified siRNA. These results indicate that the modified overhangs increase the thermodynamic stability of the siRNAs. The modified overhangs improved stability of siRNAs against degradation by nuclease S1 and 50% mouse plasma. Furthermore the modified siRNAs reduced the target gene expression in a similar manner to the unmodified siRNA in cultured cells. These results suggest that the overhang modifications are tolerated for the siRNA activity.

Keywords:

• modified RNAs
• amide-linked RNA
• siRNA activity

We would like to thank Mr. H. Miyao (Otsuka Pharmaceutical Co. Ltd.) for biological assay of siRNA. This work was partly supported by “High-Tech Research Center” Project for Private Universities: matching fund subsidy from MEXT, 2003–2007. Support from formulation research institute, administrated by Otsuka Pharmaceutical Co. Ltd., is gratefully acknowledged.

Notes

^a A549 Cells were transfected with pGL3 and pRL luciferase vectors and 20 nM siRNA. Ratios of firefly luciferase activity (Luc.) to Renilla luciferase activity (RL.) were normalized to the vector control experiment without siRNA.