MicroRNA (miRNA)

Definition

microRNA (miRNA) are small, non-coding RNA molecules that play a crucial role in regulating gene expression by targeting and binding to messenger RNA (mRNA) molecules, leading to their degradation or translational repression. These tiny RNA fragments are essential for various cellular processes and are closely linked to the structure and function of RNA in living organisms.

5 Must Know Facts For Your Next Test

1. microRNAs are typically 20-24 nucleotides in length and are processed from longer precursor molecules called pri-miRNAs and pre-miRNAs.
2. microRNAs regulate gene expression by binding to the 3\' untranslated region (UTR) of target mRNA molecules, leading to their degradation or translational repression.
3. The binding of microRNAs to their target mRNAs is based on sequence complementarity, with the 'seed region' (positions 2-8) of the microRNA being crucial for target recognition.
4. microRNAs play important roles in various cellular processes, including cell differentiation, proliferation, apoptosis, and metabolism.
5. Dysregulation of microRNA expression has been implicated in the pathogenesis of various diseases, such as cancer, cardiovascular diseases, and neurological disorders.

Review Questions

• Describe the biogenesis and processing of microRNAs.
  • microRNAs are transcribed from genomic DNA as longer precursor molecules called pri-miRNAs. These pri-miRNAs are then processed by the enzyme Drosha in the nucleus, resulting in the formation of pre-miRNAs. The pre-miRNAs are then exported to the cytoplasm, where they are further processed by the enzyme Dicer, yielding the mature, functional microRNA molecules. The mature microRNAs are then incorporated into the RNA-induced silencing complex (RISC), which guides them to their target mRNA molecules, leading to their degradation or translational repression.
• Explain the mechanism by which microRNAs regulate gene expression.
  • microRNAs regulate gene expression by binding to the 3\' untranslated region (UTR) of target mRNA molecules. This binding is based on sequence complementarity, with the 'seed region' (positions 2-8) of the microRNA being crucial for target recognition. When a microRNA binds to its target mRNA, it can lead to the degradation of the mRNA or the repression of its translation, effectively reducing the expression of the corresponding gene. This mechanism allows microRNAs to fine-tune the expression of a wide range of genes, playing a crucial role in various cellular processes.
• Discuss the potential implications of microRNA dysregulation in the context of human health and disease.
  • Dysregulation of microRNA expression has been implicated in the pathogenesis of various diseases, including cancer, cardiovascular diseases, and neurological disorders. In cancer, for example, certain microRNAs can act as tumor suppressors by targeting oncogenes, while others can function as oncogenes by targeting tumor suppressor genes. In cardiovascular diseases, microRNAs have been shown to regulate processes like angiogenesis, cardiac remodeling, and vascular function. Additionally, microRNAs have been linked to the development of neurological disorders, such as Alzheimer's disease, Parkinson's disease, and depression, due to their role in neuronal development, synaptic function, and neuroinflammation. Understanding the complex interplay between microRNAs and their target genes in health and disease has opened up new avenues for the development of microRNA-based diagnostic and therapeutic approaches.

Related terms

Non-coding RNA: RNA molecules that do not encode for proteins but instead have regulatory functions within the cell, including microRNAs, small interfering RNAs (siRNAs), and long non-coding RNAs (lncRNAs).

mRNA (Messenger RNA): A type of RNA that carries the genetic instructions from the nucleus to the ribosomes in the cytoplasm, where they are used as a template for protein synthesis.

Gene Expression:

The process by which the information encoded in a gene is used to direct the synthesis of a functional gene product, such as a protein or a functional RNA.