Selective degradation of targeted mRNAs using partially modified oligonucleotides

Abstract

At a theoretical level, the utilization of an oligonucleotide complementary to a target message to prevent translation sounds extraordinarily simple. There are, however, significant hurdles to the use of antisense oligonucleotides in vivo. Issues of nuclease stability and RNase H activity, which are presented in this chapter, must be considered in any discussion involving antisense oligonucleotides. A third important issue, cellular uptake of oligonucleotides, has not been discussed. This chapter has circumvented this complex and poorly understood area by directly microinjecting chimeric oligonucleotides into single cells. The ability to microinject oligonucleotides into Xenopus oocytes and embryos has made this an ideal system to ask important mechanistic questions involving oligonucleotide metabolism and mode of action. It is not possible, for example, to determine the rate of intracellular oligonucleotide degradation in cell or tissue culture because the rate of internalization is generally unknown. Additionally, it is not possible to compare the efficacy of two oligonucleotides adequately if they have different rates of internalization.