The expression of a structural gene is, in general, a two-step process: transcription of DNA into messenger RNA(mRNA); and, translation of mRNA into a protein. Thus, any therapeutic strategy aimed at any one or both of these steps will effectively block gene expression. One such strategy currently under investigation is a process called RNA Interference (RNAi).

RNAi, first described in petunias by R.A. Jorgensen et al. (Plant Molecular Biology 31, 957-973, 1996), acts post-transcriptionally by degrading the target mRNA transcript. Double-stranded RNA, homologous to the target gene (a disease causing gene or a viral gene) is introduced into cells where the RNA is converted into small interfering molecules of RNA (siRNA). These siRNA molecules anneal to the mRNA sequences to which they are homologous and enzymatically degrade the mRNA at this site. The expression of the abnormal gene is blocked.

The potential for treating diseases such as AIDS and Cancer are exciting...but as with any Gene Therapy strategy the risks of the treatment may be considerable.........more information on this topic