Physicochemical properties of phospborothioate oligodeoxynucleotides

Abstract

We have recently shown that phosphorothioate (PS) oligodeoxynucleotide (ODN) analogs, unlike their normal congeners, exhibit significant anti-HIV activity (Matsukura et al., (1987) Proc. Natl. Acad. Sci. USA 84, 7706-7710). We now report the syntheses, melting temperatures (Tm), and nuclease susceptibilities of a series of phosphorothioate ODN analogs. These include all-PS duplexes, duplexes with one normal chain and the other chain either all-PS, or end-capped with several PS groups at both 3' and 5' ends. The DNase susceptibilities of the S-ODNs are much less than the normal phosphodiesters, but by contrast duplexes of poly-rA with S-dT40 are much more susceptible to RNase H digestion. The Tm's for AT base pairs of S-ODNs are significantly depressed relative to normals, while GC base pairs show much less Tm depression. The Tm's of S-dT oligomers with poly-rA are reduced relative to the duplexes with normal dA oligomers. These results have significance for the biological properties of these analogs as anti-message inhibitors of gene expression, and provide a rational basis for the S-dC/G sequences as potential effective anti-AIDS agents.

Effect of unmodified triple helix‐forming oligodeoxyribonucleotide targeted to human multidrug‐resistance gene mdr1 in MDR cancer cells

“…In fact, phosphorothioated ODNs are resistant to exo-endonuclease digestion and are thus suitable for antisense activity, retaining the ability to hybridize with mRNA [33,37]. However, phosphorothioate modification reduces the triplex stability and can completely impair triple helix formation [38,39].…”

TGF-β1 effects on proliferation of rat intestinal epithelial cells are due to inhibition of cyclin D1 expression

“…Nucleotide phosphorothioates were incorporated at both the 5' and 3' three terminal residues to inhibit exonucleolytic degradation (Stein et al, 1988). As control for nonspeci®c e ects, a complementary oligonucleotide that corresponds to the`sense' cyclin D1 sequence was also synthesized.…”

Inhibition of gene expression by anti-sense oligodeoxynucleotides

“…The site of nucleolytic attack is the phosphodiester link, and modifications to this bond have been introduced to reduce degradation. The most widely used methods involve substitution of methyl phosphonates [18] and phosphorothioates [19]. Methyl phosphonate ODN have methyl group, and phosphorothioates or sulphurized ODN, a sulphur, instead ofan oxygen on the phosphate of the diester bond.…”