Prospects of chimeric RNA-DNA oligonucleotides in gene therapy

A strategy called targeted gene repair was developed to facilitate the proc ess of gene therapy using a chimeric RNA-DNA oligonucleotide. Experiments d emonstrated the feasibility of using the chimeric oligonucleotide to introd uce point conversion in genes in vitro and in vivo. However, barriers exist in the low and/or inconstant frequency of gene repair. To overcome this di fficulty, three main aspects should be considered. One is designing a more effective structure of the oligonucleoticle. Trials have included lengtheni ng the homologous region, displacing the mismatch on the chimeric strand an d inventing a novel thioate-modified single-stranded DNA, which was demonst rated to be more active than the primary chimera in cell-free extracts. The second aspect is optimizing the delivery system. Producing synthetic carri ers for efficient and specific transfection is demanding, especially for tr eatment in vivo where targeting is difficult. The third and most important aspect lies in the elucidation of the mechanism of the strategy. Investigat ion of the mechanism of strand exchange between the oligonucleotide molecul e and double-stranded DNA in prokaryotes may greatly help to understand the mechanism of gene repair in eukaryotes. The development of this strategy h olds great potential for the treatment of genetic defects and other purpose s. Copyright (C) 2001 National Science Council, ROC and S. Karger AG, Basel .