MiRNA

Definition

miRNA, or microRNA, is a small non-coding RNA molecule approximately 20-24 nucleotides in length that plays a crucial role in regulating gene expression. By binding to complementary sequences in target messenger RNAs (mRNAs), miRNAs can either degrade the mRNA or inhibit its translation, thereby fine-tuning cellular processes such as development, differentiation, and response to stress.

5 Must Know Facts For Your Next Test

1. miRNAs are involved in various biological processes including cell proliferation, apoptosis, and development by regulating gene expression post-transcriptionally.
2. Each miRNA can target multiple mRNAs, which means a single miRNA can influence many genes and pathways, contributing to complex regulatory networks.
3. Aberrant expression of miRNAs has been linked to various diseases, including cancer, cardiovascular diseases, and neurological disorders, highlighting their importance in maintaining cellular homeostasis.
4. miRNAs are stable in biological fluids, making them potential biomarkers for disease diagnosis and prognosis in clinical applications.
5. The biogenesis of miRNAs involves transcription by RNA polymerase II into primary miRNAs (pri-miRNAs), which are then processed into mature miRNAs by Dicer.

Review Questions

• How do miRNAs regulate gene expression at the post-transcriptional level?
  • miRNAs regulate gene expression by binding to complementary sequences on target mRNAs. This binding can lead to two main outcomes: the degradation of the mRNA or the inhibition of its translation into protein. By controlling the availability of specific mRNAs for translation, miRNAs serve as important modulators of gene expression in various cellular processes.
• Discuss the role of Dicer in the miRNA biogenesis pathway and its significance in gene regulation.
  • Dicer plays a critical role in the miRNA biogenesis pathway by processing long double-stranded RNA and precursor miRNAs into mature functional miRNAs. This processing is essential because only mature miRNAs can effectively bind to their target mRNAs and exert their regulatory effects. The proper functioning of Dicer ensures that cells have the right levels of miRNAs available for regulating gene expression, which is vital for normal cellular functions.
• Evaluate the potential implications of dysregulated miRNA expression in human diseases and how this knowledge can influence therapeutic strategies.
  • Dysregulated expression of miRNAs has significant implications for human diseases, particularly cancer and other chronic conditions. When miRNAs that normally suppress oncogenes are downregulated or those that promote oncogenesis are upregulated, it can lead to uncontrolled cell growth and tumor progression. Understanding these mechanisms allows researchers to develop targeted therapeutic strategies that restore normal miRNA function or utilize synthetic miRNAs to correct dysregulation, offering promising avenues for treatment.

Related terms

mRNA:

Messenger RNA (mRNA) is a type of RNA that conveys genetic information from DNA to the ribosome, where it serves as a template for protein synthesis.

RNA interference: RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation by targeting specific mRNA molecules for degradation.

Dicer: Dicer is an enzyme that processes long double-stranded RNA and precursor miRNAs into functional miRNAs, essential for the RNA interference pathway.