Question

RECALL What is RNA interference?

Short answer

RNA interference is a process where RNA molecules inhibit gene expression by neutralizing targeted mRNA.

Step-by-step solution

Understand RNA Interference

RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules.

Mechanism of RNA Interference

The mechanism involves small RNA molecules, such as small interfering RNAs (siRNAs) and microRNAs (miRNAs), that bind to mRNA and trigger its degradation or inhibit its translation.

Function of RNA Interference

RNAi serves as a crucial regulatory mechanism in cells, controlling the levels of various proteins and providing a defense against viruses and transposable elements.

Key concepts

Gene Expression Regulation

Gene expression regulation is vital for cellular function. It allows a cell to control which genes are turned on or off, ensuring that proteins are produced at the right times and in the right amounts.
Genes in the DNA are transcribed into RNA. This RNA is then translated into proteins, which perform various functions in the cell.
However, not all RNA gets translated into proteins. Certain mechanisms ensure that some RNA molecules are degraded or their translation is inhibited, thus controlling the protein levels. RNA interference is one of these key regulatory mechanisms.

Small Interfering RNAs (siRNAs)

Small interfering RNAs (siRNAs) are short double-stranded RNA molecules. They play a critical role in RNA interference.
When an siRNA binds to a target mRNA molecule, it guides the RNA-induced silencing complex (RISC) to this mRNA.
The RISC then cuts the mRNA, leading to its degradation and preventing it from being translated into a protein.
This process helps control the amount of specific proteins in the cell, aiding in the regulation of gene expression and the defense against viral infections.

microRNAs (miRNAs)

MicroRNAs (miRNAs) are another type of small RNA involved in RNA interference. They are slightly different from siRNAs but share a similar function.
miRNAs are single-stranded RNA molecules that bind to complementary sequences on target mRNAs, usually resulting in translation inhibition.
Sometimes, miRNAs can also lead to mRNA degradation if the binding is perfect.
These molecules are crucial for fine-tuning gene expression, as they help regulate the stability and translation of mRNAs, ensuring proper cellular responses and development.

mRNA Degradation

mRNA degradation is a process where mRNA molecules are enzymatically broken down. This step is essential for regulating the number of proteins synthesized within a cell.
In the context of RNA interference, siRNAs and miRNAs facilitate mRNA degradation. When these small RNAs bind to their target mRNAs, they signal cellular machinery to degrade the mRNA.
This process prevents the mRNA from being translated into proteins, thus controlling protein levels and maintaining cellular homeostasis.

Translation Inhibition

Translation inhibition is another way cells control gene expression. It occurs when the translation of mRNA into protein is blocked.
MicroRNAs often induce translation inhibition by binding to the mRNA, preventing ribosomes from translating it.
This action ensures that the protein specified by the mRNA is not produced, helping the cell manage its protein inventory precisely.

• By inhibiting translation, miRNAs can respond quickly to environmental changes, adjusting protein levels as needed.
• This regulatory mechanism is crucial for adapting to stress and maintaining normal cellular functions.