Nucleocytoplasmic shuttling: a novel in vivo property of antisense phosphorothioate oligodeoxynucleotides

Phosphorothioate oligodeoxynucleotides (P=S ODNs) are frequently used as an tisense agents to specifically interfere with the expression of cellular ta rget genes, However, the cell biological properties of P=S ODNs are poorly understood. Here we show that P=S ODNs were able to continuously shuttle be tween the nucleus and the cytoplasm and that shuttling P=S ODNs retained th eir ability to act as antisense agents. The shuttling process shares charac teristics with active transport since it was inhibited by chilling and ATP depletion in vivo. Transport was carrier-mediated as it was saturable, and nuclear pore complex-mediated as it was sensitive to treatment with wheatge rm agglutinin, Oligonucleotides without a P=S backbone chemistry were only weakly restricted in their migration by chilling, ATP depletion and wheatge rm agglutinin and thus moved by diffusion. P=S ODN shuttling was only moder ately affected by disruption of the Ran/RCC1 system. We propose that P=S OD Ns shuttle through their binding to yet unidentified cellular molecules tha t undergo nucleocytoplasmic transport via a pathway that is not as strongly dependent on the Ran/RCC1 system as nuclear export signal-mediated protein export, U-snRNA, tRNA and mRNA export. The shuttling property of P=S ODNs must be taken into account when considering the mode and site of action of these antisense agents.