Evaluation of some properties of a phosphorodithioate oligodeoxyribonucleotide for antisense application

摘要

An all phosphorodithioate oligodeoxyribonucleotide (PS₂; 17-mer) complementary to the coding region of the rabbit β-globin mRNA was compared with the normal (PO₂) and phosphorothioate (POS) oligonucleotide of the same size and sequence with respect to physicochemical properties and antisense activity in cell-free systems. The melting temperature (Tm) of the PS₂-cDNA duplex was reduced by 17?C relative to the PO₂ - cDNA duplex, compared to 11?C for the POS-cDNA duplex, suggesting a decreased stability of the duplex with an increasing sulfur substitution.Like the POS-derivative, the PS₂ oligonucleotide is quite stable against exonucleases, but these modified oligonucleotides showed different stability towards endonucleases and also towards different sub-cellular fractions of MCF-7 cells. During in vitro protein binding studies, the PS₂ oligonucleotide showed similar binding (10-20%) to that of the PO₂ oligonucleotide, while the POS oligonucleotide bound 60%. In cell-free translation, the PS₂ oligonucleotide produced slightly higher specific translation inhibition of rabbit β-globin mRNA compared to that of the PO₂ oligonucleotide, and this was true only at concentration below 2 mM. The POS-derivative, except at 10 mM concentration, always showed higher translation arrest of the rabbit β-globin mRNA compared to that of the other two oligonucleotides. The present study suggests that the PS₂ oligonucleotide offers very little advantage over the POS oligonucleotide for use as an antisense analog.