Small interfering RNA (siRNA)

Definition

Small interfering RNA (siRNA) is a class of double-stranded RNA molecules, typically 20-25 base pairs in length, that play a critical role in the gene silencing process known as RNA interference (RNAi). siRNA functions by binding to complementary mRNA sequences, leading to mRNA degradation and preventing protein translation, which is essential for regulating gene expression and maintaining cellular homeostasis.

5 Must Know Facts For Your Next Test

1. siRNAs are produced from longer double-stranded RNA through the action of the Dicer enzyme, which cleaves the RNA into shorter fragments.
2. Once formed, siRNAs are incorporated into a complex called the RNA-induced silencing complex (RISC), where they guide the complex to target mRNA for degradation.
3. siRNA-mediated silencing can be used as a powerful tool in research and therapeutic applications, allowing for targeted gene knockdown in various organisms.
4. The specificity of siRNA is determined by its sequence, which must be complementary to the target mRNA to ensure effective binding and degradation.
5. siRNAs are essential for various cellular processes, including defense against viral infections and regulation of transposable elements within the genome.

Review Questions

• How does the structure of siRNA contribute to its function in gene silencing?
  • The double-stranded structure of siRNA, typically composed of 20-25 base pairs, is crucial for its role in gene silencing. This specific length allows siRNA to effectively bind to complementary mRNA sequences with high specificity. The binding initiates the RNA interference pathway, leading to mRNA degradation via the RISC complex, ultimately preventing protein synthesis and regulating gene expression.
• Discuss the mechanisms by which siRNA exerts its effects on target mRNA within cells.
  • siRNA exerts its effects on target mRNA primarily through the RNA-induced silencing complex (RISC). Once inside the RISC, the siRNA strand guides the complex to the complementary target mRNA. This binding triggers the endonucleolytic cleavage of the mRNA strand, resulting in degradation and preventing translation. This mechanism enables precise control over gene expression and is vital for cellular functions.
• Evaluate the potential applications of siRNA technology in biomedical research and therapy, considering both benefits and challenges.
  • siRNA technology holds significant potential in biomedical research and therapeutic applications by enabling targeted gene knockdown for studying gene function and disease mechanisms. This specificity can lead to innovative treatments for conditions such as cancer and viral infections. However, challenges include ensuring efficient delivery of siRNAs into cells, avoiding off-target effects, and developing stable formulations that can resist degradation in biological environments. Addressing these challenges is crucial for maximizing the therapeutic benefits of siRNA.

Related terms

RNA interference (RNAi): A biological process where RNA molecules inhibit gene expression by causing the degradation of specific mRNA molecules.

MicroRNA (miRNA): A small non-coding RNA molecule that regulates gene expression by binding to complementary sequences in mRNA, often resulting in translational repression.

Dicer: An RNase enzyme that processes long double-stranded RNA and precursor miRNAs into short double-stranded fragments, including siRNAs.