ALPHA-BETA CHIMERIC ANTISENSE OLIGONUCLEOTIDES - SYNTHESIS AND NUCLEASE RESISTANCE IN BIOLOGICAL MEDIA

A new type of chimeric oligonucleotides composed of alpha- and beta-se ctions is described. The sequence of eight beta-nucleotides flanked at 3'- or/and 5'-ends by nuclease-resistant alpha-oligonucleotides has b een chosen as an effector domain to form a substrate for RNase H. The synthesized oligonucleotides are complementary to the translation init iation site of the pim protooncogene mRNA. We used the chemical ligati on method to prepare the chimeric oligonucleotides. The thermal stabil ity of heteroduplexes formed by the alpha beta oligonucleotides with a complementary strand is not significantly altered compared to that of their beta-analogs. These oligonucleotides promote efficient RNase H- mediated cleavage of pim mRNA. Among the alpha beta oligonucleotides s tudied, one with an alpha-fragment bound by its 3'-end to the 3'-end o f the beta-octanucleotide proved to be the most resistant to nucleolyt ic digestion in human plasma, calf serum, and murine fibroblast lysate . This alpha beta oligonucleotide directs more specific RNA cleavage b y RNase H than its beta beta counterpart.