RNAi screening toward therapeutic drug repurposing

As a result of large-scale genome-wide screens, thousands of genes have been discovered, but many of their functions remain unknown. Initially, functional analysis relied on the characterization of mutant phenotypes, a generally slow and tedious practice. At present, reverse genetics approaches are considered the most effective way to characterize gene function. Loss-of-function reverse genetics methods involve targeting genes via homologous recombination, utilize antisense oligonucleotides, ribozyme technologies, or a combination of these and related technologies, but their implementation is a cumbersome and costly procedure. In contrast, RNA interference (RNAi), specifically using short interfering RNAs (siRNAs), have revolutionized the field providing multifaceted, relatively quick, and cost-effective methods to characterize traditional gene function, as well as their function under certain conditions, such as viral infection. siRNAs, when used to exploit the cells machinery, have the ability to systematically uncover the function and interactions of most vertebrate genes (Elbashir 2002).