| 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 beta] anomers or the synthetic alpha] anomers of deoxynucleotide units. Oligo-beta] deoxynucleotides are short-lived inside oocytes (half-life approximately equal to 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-alpha]-deoxynucleotides are quite resistant to both endo and exonucleases inside Xenopus oocytes. After 8 hours only 40% of a 16-mer oligo-alpha]-deoxynucleotide were hydrolysed. The rapid degradation of oligo-beta]-deoxynucleotides suggests that efficient inhibition of translation in Xenopus oocytes involves an RNase H-induced hydrolysis of mRNAs hybridized to oligo-beta]-deoxynucleotides. |
