Several circular oligonucleotides were synthesized and characterized b
y electrospray ionization mass spectrometry. Experiments on terminatio
n of primer extension catalysed by DNA polymerases, Klenow fragment an
d Tth have demonstrated that a double helix forming circular 2'-deoxyr
ibooligomer containing a 25mer sequence complementary to the target si
ngle-stranded DNA along with a 34mer random mismatching stretch appear
s to be a potent inhibitor of replication in vitro. Studies on inhibit
ion of luciferase gene expression in a cell-free transcription-transla
tion system have shown that a duplex forming circular 2'-deoxyriboolig
onucleotide containing a 25mer sequence complementary to the target mR
NA and a 14mer random mismatching stretch can serve as an effective an
tisense compound as a standard linear complementary oligomer, Features
of double helix forming circular oligonucleotides composed of 2'-deox
yribonucleosides seem to be useful for the design of new antigene and
antisense agents.