RNA-Interference

Andrew Fire and Craig Mello 2006 (Nobel Prize in Physiology or Medicine of the Year 2006)

RNA interference (RNAi) is the interruption of translation, i.e. the translation of messenger RNA (mRNA) into a protein. The organism regulates its gene expression via RNA interference and RNA silencing, e.g. in order to be able to defend itself against invading foreign nucleic acids (e.g. viruses). This "tool" is developed in all eukaryotic cells. RNA interference is therefore a form of gene regulation in which a gene that has already been transcribed is not converted into a protein, or only to a small extent (gene silencing). Since RNA interference usually begins after transcription, it is also referred to as "post-transcriptional gene silencing" (PTGS).

During gene silencing, double-stranded RNA molecules are formed in the cell, which are cleaved by dicers (dsRNA-specific endonucleases from the RNase III family), into small RNAs with a length of 18-25 nucleotides. These molecules are also known as siRNAs (small interfering RNAs) or micro RNA (miRNA). The siRNAs are then incorporated as a single strand by a Dicer-associated protein into the RNA-induced silencing complex(RISC), which contains so-called Argonaute proteins and can degrade RNA that is complementary to the siRNA - the siRNA thus formally corresponds to an antisense mRNA.

Remarkably, RNA silencing in plants following virus infection is not restricted to the single virus-affected cell; rather, the signal spreads from cell to cell locally or to an entire plant.

1. Agrawal N et al. (2003) RNA interference: biology, mechanism, and applications. Microbiol Mol Biol Rev 67:657-685.
2. Han H (2018) RNA interference to knock down gene expression. Methods Mol Biol 1706:293-302.