key term - Microrna (mirna)

Definition

Microrna (miRNA) is a class of small, non-coding RNA molecules, typically about 22 nucleotides in length, that play a crucial role in the regulation of gene expression at the translational level. They function by binding to complementary sequences on target messenger RNAs (mRNAs), leading to mRNA degradation or inhibition of translation. This regulation is essential for controlling various cellular processes, including development, differentiation, and response to stress.

5 Must Know Facts For Your Next Test

1. miRNAs are involved in the regulation of approximately 60% of all protein-coding genes in higher eukaryotes.
2. They are generated from longer primary transcripts called primary miRNAs (pri-miRNAs) through the action of the Drosha enzyme in the nucleus.
3. Once processed, miRNAs are exported to the cytoplasm, where they associate with RISC to guide silencing of target mRNAs.
4. The binding of miRNAs to mRNAs typically occurs at the 3' untranslated region (UTR), where they can inhibit translation or promote degradation.
5. Dysregulation of miRNA expression has been implicated in various diseases, including cancer, cardiovascular diseases, and neurological disorders.

Review Questions

• How do micrornas (miRNAs) contribute to the regulation of gene expression at the translational level?
  • miRNAs contribute to the regulation of gene expression by binding to specific target mRNAs and either leading to their degradation or inhibiting their translation into proteins. This process allows for fine-tuning of protein levels within cells and plays an essential role in various cellular functions, including differentiation and stress responses. By controlling how much protein is made from specific mRNAs, miRNAs ensure that cellular processes occur in a balanced and coordinated manner.
• Discuss the significance of the RNA-induced silencing complex (RISC) in the function of micrornas.
  • The RNA-induced silencing complex (RISC) is vital for the action of micrornas (miRNAs) as it is responsible for mediating their effects on target mRNAs. Once a miRNA is incorporated into RISC, it guides the complex to complementary sequences on mRNAs. This interaction can result in either degradation of the mRNA or inhibition of its translation, effectively silencing gene expression. RISC thus acts as a critical mediator in the pathway through which miRNAs exert their regulatory functions.
• Evaluate the impact of dysregulation of micrornas on human health and disease.
  • Dysregulation of micrornas can have significant implications for human health and disease as they play a critical role in regulating gene expression. Abnormal levels of specific miRNAs have been associated with various conditions such as cancer, where some miRNAs may act as oncogenes or tumor suppressors. Additionally, cardiovascular diseases and neurological disorders have also been linked to altered miRNA expression patterns. Understanding these changes can lead to potential therapeutic strategies that target miRNA pathways for disease treatment and prevention.

Related terms

Messenger RNA (mRNA): A type of RNA that carries genetic information from DNA to the ribosome, where proteins are synthesized.

RNA-induced silencing complex (RISC): A multi-protein complex that incorporates miRNAs and mediates the silencing of target mRNAs by promoting degradation or preventing translation.

Post-transcriptional regulation: The process by which gene expression is regulated after the transcription of mRNA, including mechanisms such as splicing, editing, and translation control.