Present an overview of RNA interference (RNAi). How does the silencing process begin, and what major components participate?

Key Concepts

RNA Interference (RNAi)

RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, effectively silencing specific genes. This mechanism is crucial for regulating gene activity and defending against viral infections. RNAi is initiated by the presence of double-stranded RNA (dsRNA), which is processed into smaller fragments that guide the silencing process.

Dicer and siRNA

Dicer is an enzyme that plays a pivotal role in the RNAi pathway by cleaving long double-stranded RNA into short interfering RNA (siRNA) fragments, typically 20-25 nucleotides in length. These siRNAs are essential for the silencing process as they serve as guides for the RNA-induced silencing complex (RISC), which ultimately leads to the degradation of complementary mRNA.

RNA-Induced Silencing Complex (RISC)

The RNA-induced silencing complex (RISC) is a multi-protein complex that incorporates siRNA and is responsible for the gene silencing effect of RNAi. Once the siRNA is loaded into RISC, it pairs with its complementary mRNA target, leading to the cleavage and degradation of the mRNA. This process effectively prevents the translation of the target gene into protein, thereby silencing its expression.