Rate of degradation of [α]- and [β]-oligodeoxynucleotides inXenopusoocytes. Implications for anti-messenger strategies

Abstract

End-labelled oligodeoxynucleotides were injected into Xenopus laevis oocytes and their degradation products were analysed by high-performance ion-exchange liquid chromatography after various times of incubation. The oligonucleotides were synthesised with either the natural [ß] anomers or the synthetic [α] anomers of deoxynucleotide units. Oligo-[ß]deoxynucleotides are short-lived inside oocytes (half-life = 10 min). Covalent attachment of an intercalating agent to the 3′-phosphate and of a methylthiophosphate group at the 5′-end protects oligodeoxynucleotides against 3′- and 5′-exonucleases, respectively. The half-life of such substituted oligodeoxynucleotides is increased to 40 minutes. Oligo-[α]-deoxynucleotides are quite resistant to both endo and exonucleases inside Xenopus oocytes. After 8 hours only 40 % of a 16-mer oligo-[α]-deoxynucleotide were hydrolysed. The rapid degradation of oligo-[ß]-deoxynucleotides suggests that efficient inhibition of translation in Xenopus oocytes involves an RNase H-induced hydrolysis of mRNAs hybridized to oligo-[ß]-deoxynucleotides.