Nucleic Acids Research Advance Access published online on January 16, 2009
Nucleic Acids Research, doi:10.1093/nar/gkn1088
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Chemistry and Synthetic Biology |
Synthesis and characterization of 2'-modified-4'-thioRNA: a comprehensive comparison of nuclease stability
Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan
*To whom correspondence should be addressed. Tel: +81 11 706 3228; Fax: +81 11 706 4980; Email: matuda{at}pharm.hokudai.ac.jp
Correspondence may also be addressed to Noriaki Minakawa. Tel: +81 11 706 3230; Fax: +81 11 706 4980; Email: noriaki@pharm.hokudai.ac.jp
Received December 17, 2008. Revised December 26, 2008. Accepted December 30, 2008.
We report herein the synthesis and physical and physiological characterization of fully modified 2'-modified-4'-thioRNAs, i.e. 2'-fluoro-4'-thioRNA (F-SRNA) and 2'-O-Me-4'-thioRNA (Me-SRNA), which can be considered as a hybrid chemical modification based on 2'-modified oligonucleotides (ONs) and 4'-thioRNA (SRNA). In its hybridization with a complementary RNA, F-SRNA (15mer) showed the highest Tm value (+16°C relative to the natural RNA duplex). In addition, both F-SRNA and Me-SRNA preferred RNA as a complementary partner rather than DNA in duplex formation. The results of a comprehensive comparison of nuclease stability of single-stranded F-SRNA and Me-SRNA along with 2'-fluoroRNA (FRNA), 2'-O-MeRNA (MeRNA), SRNA, and natural RNA and DNA, revealed that Me-SRNA had the highest stability with t1/2 values of > 24 h against S1 nuclease (an endonuclease) and 79.2 min against SVPD (a 3'-exonuclease). Moreover, the stability of Me-SRNA was significantly improved in 50% human plasma (t1/2 = 1631 min) compared with FRNA (t1/2 = 53.2 min) and MeRNA (t1/2 = 187 min), whose modifications are currently used as components of therapeutic aptamers. The results presented in this article will, it is hoped, contribute to the development of 2'-modified-4'-thioRNAs, especially Me-SRNA, as a new RNA molecule for therapeutic applications.