Characterization of oligonucleotide transport into living cells.

Addition of antisense oligonucleotides to cell cultures has been used to specifically inhibit gene expression. We have investigated the mechanism by which oligonucleotides enter living cells. These compounds are taken up by cells in a saturable, size-dependent manner compatible with receptor-mediated endocytosis. Polynucleotides of any length are competitive inhibitors of oligomer transport, providing they possess a 5'-phosphate moiety. Using oligo(dT)-cellulose for affinity purification, we have identified an 80-kDa surface protein that may mediate transport. Knowledge of the oligonucleotide transport mechanism should facilitate the design of more effective synthetic antisense oligomers as potential clinical agents.