RNA interference

RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. Historically, it was known by other names, including co-suppression, post-transcriptional gene silencing (PTGS), and quelling. The discovery of RNAi was preceded by observations of transcriptional inhibition by antisense RNA expressed in transgenic plants and more directly by reports of unexpected outcomes in experiments performed by plant scientists in the late 1990s. The detailed study of these phenomena led to the discovery of RNAi in Caenorhabditis elegans (a type of nematode) by Andrew Fire and Craig Mello, who were awarded the Nobel Prize in Physiology or Medicine in 2006 for their work.

Mechanism

RNA interference involves several steps in the pathway. It begins with the enzyme Dicer, which chops long double-stranded RNA (dsRNA) molecules into smaller pieces called small interfering RNAs (siRNAs). These siRNAs are then incorporated into the RNA-induced silencing complex (RISC). Guided by the siRNA, the RISC complex identifies complementary mRNA molecules and cleaves them, thereby preventing the mRNA from being used as a template for protein synthesis. This process effectively silences the expression of specific genes.

Types of RNAi

There are two main types of RNA interference: microRNA (miRNA) and small interfering RNA (siRNA). miRNAs are endogenously produced in cells and regulate gene expression by binding to complementary sequences on target mRNAs, often resulting in gene silencing. siRNAs, on the other hand, are often introduced into the cell from the outside and have a similar mechanism of action but are generally used to silence specific genes.

Applications

RNA interference has been harnessed for various applications in research, medicine, and agriculture. In research, it is used to study gene function by silencing specific genes and observing the resulting phenotypic changes. In medicine, RNAi has potential therapeutic applications, such as in the treatment of viral infections, cancer, and genetic disorders. In agriculture, RNAi is used to develop crops that are resistant to pests and diseases.

Challenges and Future Directions

Despite its potential, the application of RNA interference in medicine faces several challenges, including delivery to target cells, off-target effects, and immune system activation. Researchers are actively working on developing more efficient and specific delivery methods to overcome these hurdles.

See Also

• Gene silencing
• Antisense RNA
• Biotechnology
• Genetic engineering