Stability of stereoregular oligo(nucleoside phosphorothioate)s in human cells. Diastereoselectivity of cellular 3'-exonuclease

Stability of oligo(nucleoside phosphorothioate)s (PS-oligos) in HUVEC (human umbilical vein endothelial cells) has been studied. Cytosolic fraction of HUVEC possesses 3'-exonucleolytic activity which is responsible for degradation of natural oligomers and PS-oligos. The enzyme is R-P-specific, i.e. it cleaves internucleotide phosphorothioate function of R-P- and not S-P-configuration at phosphorus atom.