Properties of nicked and circular dumbbell RNA/DNA chimeric oligonucleotides containing antisense phosphodiester oligodeoxynucleotides.

We have designed a new class of oligonucleotides, 'dumbbell RNA/DNA chimeric phosphodiester oligonucleotides', consisting of a sense RNA sequence and its complementary antisense DNA sequence, with two hairpin loop structures. The reaction of the Nicked (NDRDON) and Circular (CDRNON) dumbbell DNA/RNA chimeric oligonucleotides with RNase H gave the corresponding antisense phosphodiester oligodeoxynucleotide together with the sense RNA cleavage products. The liberated antisense phosphodiester oligodeoxynucleotide was bound to the target 45 mer RNA, which gave 45 mer RNA cleavage products by treatment with RNase H. The circular dumbbell RNA/DNA chimeric oligonucleotide showed more nuclease resistance than the linear antisense phosphodiester oligodeoxynucleotide (anti-ODN) and the nicked dumbbell RNA/DNA chimeric oligodeoxynucleotide. The circularization, achieved by joining the 3' and the 5' ends of RNA/DNA chimeric oligonucleotides containing two hairpin loop structures, increases the oligonucleotide uptake into cells, as compared with the nicked dumbbell RNA/DNA chimeric oligonucleotide and the linear antisense phosphodiester oligodeoxynucleotides. When the circular dumbbell RNA/DNA chimeric oligonucleotide is directly delivered into retrovirus infected cells, its antisense phosphodiester oligodeoxynucleotide function appears.