ABSTRACT
The existence of RNA interference (RNAi) was fi rst reported more than 20 years ago in p. x hybrida fl owers (Napoli et al. 1990). It was shown that when the gene responsible for its pigmentation was overexpressed, the fl ower lost its endogenous color by suppressing both the transgene and the endogenous gene. Napoli and colleagues termed this process “cosuppression”. More importantly, they observed that both genes were synthesized by the cell, but were silenced post transcriptionally. Years later, Fire and colleagues described the process of RNAi in animal cells when they discovered the ability of double stranded RNA to silence gene expression in the nematode worm C. elegans (Fire et al. 1998). Based on the substantial amount of data generated following this discovery, it is now believed that RNAi exists in all animals (Tokatlian and Segura 2010). The natural function of RNAi appears to be protection of the genome against invasion by mobile genetic material elements, such as transposons and viruses that produce aberrant RNA or dsRNA when they become active. Recently, the use of siRNA has rapidly become a powerful tool in silencing gene expression. Because of its high specifi city and ability to silence genes that could not be targeted before, the process of RNA degradation has garnered a great deal of attention from the scientifi c community for its possible use as a therapeutic agent in various disease targets, including viral infections and cancer (Landen et al. 2005; Lu et al. 2010; Morrissey et al. 2005; Okumura et al. 2008).
