O. Heidenreich et al., RNASE H-INDEPENDENT ANTISENSE ACTIVITY OF OLIGONUCLEOTIDE N3'-]P5' PHOSPHORAMIDATES, Nucleic acids research, 25(4), 1997, pp. 776-780
Oligonucleotide N3'-->P5' phosphoramidates are a new and promising cla
ss of antisense agents. Here we report biological properties of phosph
oramidate oligonucleotides targeted against the human T cell leukemia
virus type-1 Tax protein, the major transcriptional transactivator of
this human retrovirus. Isosequential phosphorothioate oligodeoxynucleo
tides and uniformly modified and chimeric phosphoramidate oligodeoxynu
cleotides containing six central phosphodiester linkages are all quite
stable in cell nuclei, The uniformly modified anti-tax phosphoramidat
e oligodeoxynucleotide does not activate nuclear RNase H, as was shown
by RNase protection assay, In contrast, the chimeric phosphoramidate-
phosphodiester oligodeoxynucleotide is an efficient activator of RNase
H, The presence of one or two mismatched nucleotides in the phosphodi
ester portion of oligonucleotides affected this activation only neglig
ibly, When introduced into tax-transformed fibroblasts ex vivo, only t
he uniformly modified anti-tax phosphoramidate oligodeoxynucleotide ca
used a sequence-dependent reduction in the Tax protein level, Neither
the chimeric phosphoramidate nor the phosphorothioate oligodeoxynucleo
tides significantly reduced tax expression under similar experimental
conditions.