RNA interference

History of discovery and scientific recognition

The phenomenon of RNA interference remained a mystery to molecular biology for a long time. The breakthrough occurred in 1997 thanks to the research of American scientists Andrew Fire and Craig Mello. While conducting classical biological experiments on model organisms—roundworms (nematodes)—they made a surprising observation. The scientists discovered that the introduction of artificially synthesized short double-stranded RNA molecules into cells is capable of completely and purposefully shutting down the activity of strictly defined genes.

The significance of this fundamental discovery for understanding the principles of genetic information regulation turned out to be enormous. The scientific community highly appreciated the researchers' work, and as early as 2006, Andrew Fire and Craig Mello were awarded the Nobel Prize in Physiology or Medicine for the discovery of RNA interference.

Mechanism of action of small interfering RNAs

The key agents of the process are small interfering RNAs (siRNAs, or in international nomenclature siRNA, small interfering RNA). These are specific short double-stranded RNA molecules whose size is strictly limited and ranges from 21 to 23 nucleotide base pairs. It is this compact structure that allows them to effectively control gene activity.

The process of RNA interference is a strict sequence of molecular events:

1. First, the siRNA molecule successfully penetrates the intracellular space.
2. Once in the cytoplasm, it signals specialized cellular enzymes. These enzyme complexes locate single-stranded messenger RNA (mRNA) that is strictly complementary to the siRNA sequence and physically cleave it into individual fragments.
3. Next, these cleaved mRNA regions are removed. Their selective degradation (complete destruction) or direct inhibition of the translation process is initiated.
4. As a result of the destruction of the template, genetic information is not transmitted to the cell's protein factories—ribosomes. Consequently, the synthesis of the target protein is completely blocked.

Biological functions in a living cell

RNA interference is not just a laboratory phenomenon, but a vital natural mechanism for cell survival and life support. There are four main biological functions of this process:

• Intracellular immunity: the system recognizes and purposefully induces the destruction of foreign genetic material that enters the cell during viral infection.
• Protection of genome stability: the mechanism ensures the suppression and physical destruction of mobile (transposable) elements of the genome, whose excessive activity can lead to dangerous mutations.
• Expression regulation: the cell is able to flexibly manage its own metabolism by blocking the work of functional genes when the proteins they produce are no longer required.
• Chromatin structure modification: siRNA molecules can not only destroy mRNA, but also bind to complementary regions of the DNA itself, leading to changes in the spatial packaging of chromatin.

Prospects for clinical application

Based on the experimental data obtained, modern medicine places great hope on therapies utilizing the RNA interference mechanism. This makes it possible to target the cause of a disease at the most fundamental molecular level.

• In ophthalmology, researchers are actively investigating the possibilities of targeted treatment for macular degeneration—a severe retinal vascular pathology leading to vision loss.
• In the field of infectious diseases, truly striking results have already been achieved. During experiments, the use of a specially developed siRNA-based drug allowed primates that had previously received an absolutely lethal dose of the Ebola virus to survive. This paves the way for the creation of fundamentally new, highly effective antiviral agents.

Class and exam questions

What else to study on this topic

• Structure and principles of operation of enzyme complexes that cleave mRNA
• Mechanisms of chromatin structure alteration involving siRNA
• Classification and role of mobile genetic elements in the cell
• Molecular pathogenesis of retinal macular degeneration
• Features of siRNA drug applications against the Ebola virus

Other topics in the "Variability and its forms" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.