RNAi

RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. Historically, RNAi was known by other names, including co-suppression, post-transcriptional gene silencing (PTGS), and quelling. The detailed study of each of these seemingly different processes elucidated that the identity of these phenomena were all actually RNAi. Andrew Fire and Craig C. Mello shared the 2006 Nobel Prize in Physiology or Medicine for their work on RNA interference in the nematode worm Caenorhabditis elegans, which they published in 1998.

Mechanism

RNAi is an RNA-dependent gene silencing process that is controlled by the RNA-induced silencing complex (RISC) and is initiated by short double-stranded RNA molecules in a cell's cytoplasm, where they interact with the catalytic RISC component argonaute. When the dsRNA is exogenous (coming from infection by a virus with an RNA genome or laboratory manipulations), the RNA is cleaved into short siRNAs by the endonuclease Dicer. These siRNAs are then separated into two single-stranded RNAs (ssRNAs) – the passenger strand and the guide strand – by RISC. Using the guide strand, RISC targets the complementary mRNA, leading to mRNA degradation and gene silencing.

Applications

The RNAi pathway is used as a tool in molecular biology to study the function of genes in cell culture and in living organisms. RNAi has been used to genetically engineer plants to yield virus-resistant crops and is being investigated for treatments of HIV, cancers, and other conditions.

See also

• MicroRNA
• siRNA
• RNA-induced silencing complex
• Argonaute
• Dicer
• Post-transcriptional gene silencing
• Andrew Fire
• Craig C. Mello

References

RNAi Resources
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