Small interfering RNA or siRNA initially come from longer stands of exogenous RNA. They are small, double-stranded pieces of RNA that interfere with the process of translation. As they are only around 21 nucleotides long they bind to the mRNA during translation at specific sequences during a process called RNA interference. This assists the degradation/breakdown of mRNA. The siRNA is mimicking the mechanism of action of the miRNA, which cells are producing on their own to silence or knock down genes.
siRNA are often used in biomedical research. With the use of these small interfering RNA strands it is possible to knock out specific genes or translation products very easily. Instead of knocking out the gene constantly through genetic engineering on a genomic area, siRNA enables the researcher to stop the translation of the genes mRNA, while the gene is still transcribed. Additionally, the knock out of the gene is not constant and only for a certain amount of time as the siRNA is getting degraded by RISC and Dicer over time.
Mechanism of action
The already synthesized siRNA is given to the cells. In the cell the siRNA is interfering with the targeted mRNA through complement base pairing and forming partially double-stranded RNA. The RISC complex and Dicer complex are recognising these double-stranded RNA strands and are degrading the RNA. As the mRNA is degraded now, the information of the transcribed gene is not resolving in a protein and the gene is knocked out.