Synthesis and hybridization studies of oligonucleotides containing 1-(2-deoxy-2-α-C-hydroxymethyl-β-d-ribofuranosyl)thymine (2′-α-hm-dT)

Abstract

We report the first investigation of oligoribonucleotides containing a few 1-(2-deoxy-2-α-C-hydroxymethyl-β-d-ribofuranosyl)thymine units (or 2′-hm-dT, abbreviated in this work 'H'). Both the 2′-CH2O-phosphoramidite and 3′-O-phosphoramidite derivatives of H were synthesized and incorporated into both 2′,5′-RNA and RNA chains. The hybridization properties of the modified oligonucleotides have been studied via thermal denaturation and circular dichroism studies. While 3′,5′-linked H was shown previously to significantly destabilize DNA:RNA hybrids and DNA:DNA duplexes (modification in the DNA strand; ΔTm ∼ -3°C/insert), we find that 2′,5′-linked H have a smaller effect on 2′,5′-RNA:RNA and RNA:RNA duplexes (ΔTm = -0.3°C and -1.2°C, respectively). The incorporation of 3′,5′-linked H into 2′,5′RNA:RNA and RNA:RNA duplexes was found to be more destabilizing (-0.7°C and -3.6°C, respectively). Significantly, however, the 2′,5′-linked H units confer marked stability to RNA hairpins when they are incorporated into a 2′,5′-linked tetraloop structure (ΔTm = +1.5°C/insert). These results are rationalized in terms of the compact and extended conformations of nucleotides. © The Author 2005. Published by Oxford University Press. All rights reserved.