Control of gene expression by RNAi: A revolution in functional genomics

Abstract

RNA interference is an evolutionarily preserved gene-silencing phenomenon in eukaryotic organisms, which is triggered by double-stranded RNA (dsRNA) derived from viral replication intermediates or transposable elements or an introduced synthetic oligonucleotide. Dicer, an endonuclease, processes dsRNA into 21- to 23-base-pair (bp) small interfering RNA (siRNA) with 2-nucleotide 3' overhangs, which are further linked with the RNA-induced silencing complex (RISC). Argonaute, an active (AGO)-family protein of RISC remove the sense strand of siRNA, guided by the antisense strand, mediates the destruction of cognate target RNA with exquisite potency and selectivity. RNAi is employed to downregulate the activity of a gene with hereditability, and other significant advantages have revolutionized functional genomics to discover genes involved in disease progression and validate gene function, holding promise for the expansion of new therapeutics to treat several diseases. RNAi has enormous exciting applications in plant biotechnology, generating new hopes to produce flowers with desired colors, and to enhance crop yield and shelf life, while in humans it is used to treat various forms of cancer, infectious diseases, and neurodegenerative disorders, though the stability, off-target activity, and in vivo delivery of small interfering RNAs remain significant obstacles. This chapter reviews the mechanism of RNA interference, its applications, and challenges encountered while using this technology for research purposes.