RNA interference (RNAi) is a natural biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. This process is triggered by specific types of RNA molecules, such as double-stranded RNA (dsRNA), rather than originating from a single "RNA interference gene" itself. The source of these triggering RNA molecules can vary.
### Primary Sources of RNA Triggers
The RNA molecules that initiate the RNA interference pathway can originate from different sources, including external invaders or elements within the cell's own genome. These sources provide the double-stranded or structured RNA precursors that the cell's machinery processes to guide gene silencing.
According to research, significant sources of these RNA triggers include:
- Viral Infections: Viruses, particularly those containing RNA as their genetic material, can introduce or produce RNA structures that trigger RNAi in the host organism. For example, the replication process of many RNA viruses involves creating double-stranded RNA intermediates, a potent trigger for the RNAi pathway.
- Mobile Genetic Elements (Transposons): Transposons are segments of DNA that can move to different positions within the genome of a single cell. Some types of transposons replicate through an RNA intermediate. This process can generate RNA structures, such as dsRNA, that are recognized by the cellular RNAi machinery, allowing the cell to control transposon activity.
As stated in the provided information: "The source of RNA gene could be from an infection by viruses having RNA genomes or mobile genetic elements transposons that replicate via an RNA intermediate." This clearly identifies viral RNA genomes and the RNA intermediates of transposons as key origins for the RNA molecules that activate RNA interference.
#### How These Sources Activate RNAi
The RNA structures originating from these sources serve as substrates for cellular enzymes like Dicer. Dicer cleaves these longer RNA molecules into smaller fragments, such as small interfering RNAs (siRNAs). These siRNAs are then incorporated into effector complexes, which guide them to complementary messenger RNA (mRNA) molecules, leading to their degradation or inhibition of translation, thus silencing the targeted gene expression.
| Source Type | Origin | Mechanism of RNA Generation | Result in RNAi |
|---|---|---|---|
| Viral Infection | Viruses with RNA Genomes | Replication intermediates, viral RNA structures | Antiviral defense |
| Mobile Genetic Element | Transposons replicating via RNA intermediate | Transcription into RNA, formation of RNA structures | Genome control |
These sources highlight the defensive and regulatory roles of RNA interference within organisms, providing mechanisms to combat foreign nucleic acids and control potentially harmful internal genetic elements.
