RNAi

RNA interference (RNAi) is a process within living cells that moderates the activity of their genes. Two types of RNA molecules – microRNA (miRNA) & small interfering RNA (siRNA) – are central to RNA interference, by being able to  bind to other specific mRNA molecules in order to either increase or decrease their activity, (eg. by preventing an mRNA from producing a protein). Due to this action RNAi play a very  important role in defending cells against parasitic genes – viruses and transposons – as well as directing development as well as gene expression in general.

 

The RNAi pathway is found in many eukaryotes including animals and is initiated by the enzyme Dicer, which cleaves long double-stranded RNA (dsRNA) molecules into short fragments of ~20 nucleotides that are called siRNAs. Each siRNA is unwound into two single-stranded (ss) ssRNAs, namely the passenger strand and the guide strand. The passenger strand will be degraded, and the guide strand is incorporated into the RNA-induced silencing complex (RISC).

 

The selective and robust effect of RNAi on gene expression makes it a valuable research tool, both in cell culture and in living organisms because synthetic dsRNA introduced into cells can induce suppression of specific genes of interest. RNAi may also be used for large-scale screens that systematically shut down each gene in the cell, which can help identify the components necessary for a particular cellular process or an event such as cell division. Exploitation of the pathway is also a promising tool in biotechnology and medicine.

For an animated depiction of RNAi action follow this link