Mirna

Definition

MicroRNA (miRNA) is a small, non-coding RNA molecule that plays a crucial role in the regulation of gene expression by binding to complementary sequences on target messenger RNA (mRNA) transcripts. This interaction typically leads to the silencing of genes, either by inhibiting translation or causing degradation of the mRNA, thereby influencing various biological processes and cellular functions in both prokaryotes and eukaryotes.

5 Must Know Facts For Your Next Test

1. miRNAs are typically 20-24 nucleotides long and are derived from longer precursor transcripts that are processed by enzymes like Dicer.
2. The binding of miRNAs to their target mRNAs often occurs in the 3' untranslated region (3' UTR), where they can block translation or promote degradation.
3. miRNAs are involved in regulating essential cellular processes such as development, differentiation, apoptosis, and responses to stress.
4. In eukaryotes, miRNAs are crucial for fine-tuning gene expression, allowing cells to respond rapidly to changes in their environment.
5. Dysregulation of miRNA expression has been linked to various diseases, including cancer, where certain miRNAs can act as oncogenes or tumor suppressors.

Review Questions

• How do miRNAs contribute to gene regulation in eukaryotic cells?
  • miRNAs contribute to gene regulation in eukaryotic cells by binding to complementary sequences on target mRNAs, primarily in their 3' UTRs. This binding inhibits translation and can lead to mRNA degradation, effectively silencing the gene. This mechanism allows for precise control over gene expression levels, enabling cells to adapt quickly to environmental changes and maintain homeostasis.
• What role does Dicer play in the maturation of miRNAs and how is this process significant for gene regulation?
  • Dicer is an essential enzyme that processes precursor miRNA (pri-miRNA) into mature miRNAs by cleaving them into shorter RNA fragments. This processing step is critical for producing functional miRNAs that can regulate target mRNAs. Without Dicer's action, miRNAs would not be generated, leading to impaired gene regulation and potential disruptions in cellular functions.
• Evaluate the implications of miRNA dysregulation in disease states, particularly cancer, and how this understanding could influence therapeutic strategies.
  • The dysregulation of miRNA expression can have profound implications in disease states such as cancer, where specific miRNAs may function as oncogenes or tumor suppressors. Understanding these roles allows researchers to identify potential biomarkers for early diagnosis or targets for novel therapies. For example, restoring the function of tumor-suppressive miRNAs or inhibiting oncogenic ones could form the basis for targeted treatments aimed at re-establishing normal gene regulatory networks in cancer cells.

Related terms

Gene Silencing: The process by which a gene's expression is inhibited or completely shut down, often through mechanisms involving miRNAs or other regulatory molecules.

Dicer: An enzyme that processes precursor miRNA (pri-miRNA) into functional miRNA by cutting them into smaller RNA fragments.

Transcriptional Regulation: The control of the amount and timing of mRNA production from a gene, which can be influenced by various factors, including miRNAs.