RNA interference (RNAi) is a crucial biological process that regulates gene expression by targeting RNA transcripts to prevent their translation into proteins. This mechanism is a form of post-transcriptional regulation, meaning it occurs after the transcription of DNA into RNA, and it primarily involves RNA molecules rather than DNA.
There are two main types of RNA involved in RNA interference: microRNAs (miRNAs) and small interfering RNAs (siRNAs). MicroRNAs are typically single-stranded and can target multiple transcripts simultaneously, making them versatile regulators of gene expression. In contrast, siRNAs are double-stranded and are more specific, usually targeting a single transcript for degradation.
The production of microRNAs begins in non-coding regions of genes, such as introns or regions upstream or downstream of the start codon. These regions are transcribed into a longer RNA molecule known as pre-microRNA. The enzyme Dicer processes this pre-microRNA by trimming it down to approximately 22 nucleotides, resulting in the mature microRNA. This microRNA then associates with another enzyme called RISC (RNA-induced silencing complex), which helps the microRNA bind to complementary RNA transcripts, marking them for destruction.
On the other hand, siRNAs originate from double-stranded RNA that often forms a hairpin loop structure. Similar to microRNAs, Dicer processes the pre-siRNA to create the mature siRNA. However, RISC then converts the double-stranded siRNA into a single-stranded form, which can also bind to complementary RNA transcripts, leading to their degradation.
Both microRNAs and siRNAs play essential roles in regulating gene expression by ensuring that only the desired proteins are produced, thus maintaining cellular function and responding to environmental changes. The ability of these RNA molecules to bind specifically to their target transcripts highlights their importance in gene regulation and potential therapeutic applications in gene silencing.
