The sequence-specificity of antisense oligonucleotides (ODN) against c
-myc mRNA was tested by Northern blot analysis. Rat smooth muscle cell
s were treated with antisense or control ODN against c-myc modified by
the ''minimal protection strategy''.(8) At 0.3 mu M concentration the
ODN show a very specific reduction in c-myc mRNA levels. Use of the '
'minimal protection strategy'' minimizes nonspecific effects as observ
ed for all-phosphorothioate ODN containing four consecutive guanine re
sidues.