ABSTRACT
Since the advent of DNA sequencing and polymerase chain reaction (PCR), there has been rarely one emerging technology that has received as much attention as the use of RNA interference (RNAi). The reason for this enthusiasm is that the phenomenon of RNAi firstly enabled a simple and inexpensive way to rapidly ablate specific messenger RNA (mRNA) species by inducing their degradation via a cellular protein machinery collectively named the RNA-induced silencing complex or RISC (Ketting et al., 2001). The phenomenon of RNAi was well known as a mechanism of inducing post-transcription gene silencing in plants and bacteria, where anti-sense RNA is being used to artificially silence the translation of proteins in select species. However, it is the discovery that small RNA polymers of 19-23 nucleotides can post-transcriptionally interfere with gene expression, either by inhibiting translation or inducing the degradation of complementary mRNA strands, that opened up applications in post-genomic research. For the first time it is now possible to synthesize small RNA species, as singlestranded, double-stranded or small hairpin structures, and introduce these molecules through common transfection methods into cells, where they serve to guide the RNA degradation machinery to the select target species. The RISC complex then systematically degrades the complementary mRNA, effectively resulting in the ablation of a specific mRNA species. Depending on the efficiency of ablation and the stability of the corresponding protein, the RNAi will ultimately result in the loss or reduction of the gene product. One of the major attractions of this technology is that it enables functional genetic analyses in eukaryotic systems that have been previously resilient to rapid genetic study, as well as gene ablation screens.
