MiRNA

Definition

miRNA, or microRNA, is a small, non-coding RNA molecule that plays a crucial role in the regulation of gene expression at the post-transcriptional level. By binding to complementary sequences on target messenger RNAs (mRNAs), miRNAs can inhibit translation or lead to mRNA degradation, effectively fine-tuning the protein output of genes and influencing various cellular processes.

5 Must Know Facts For Your Next Test

1. miRNAs are typically about 20-22 nucleotides long and are derived from longer RNA transcripts that fold into hairpin structures.
2. They play key roles in various biological processes such as development, differentiation, cell proliferation, and apoptosis.
3. miRNAs can regulate multiple target genes simultaneously, contributing to complex regulatory networks within the cell.
4. Abnormal expression of miRNAs has been implicated in various diseases, including cancer, cardiovascular diseases, and neurological disorders.
5. The interaction between miRNAs and their target mRNAs is often mediated through imperfect base pairing, allowing for extensive regulation of gene expression.

Review Questions

• How do miRNAs contribute to post-transcriptional regulation of gene expression?
  • miRNAs contribute to post-transcriptional regulation by binding to complementary sequences on target mRNAs. This binding can either block translation or lead to the degradation of the mRNA, effectively reducing the amount of protein produced from that gene. By fine-tuning gene expression, miRNAs play a crucial role in maintaining cellular homeostasis and influencing various biological processes.
• What is the role of Dicer in the maturation of miRNAs, and why is this process significant for cellular function?
  • Dicer is an essential enzyme that processes long double-stranded RNA and precursor miRNAs into functional miRNAs. This maturation process is significant because it generates the active forms of miRNAs that can effectively bind to target mRNAs and regulate their expression. Without Dicer's action, the biogenesis of miRNAs would be disrupted, leading to impaired regulation of gene expression and potential cellular dysfunction.
• Evaluate the impact of altered miRNA expression on disease development and progression, particularly in cancer.
  • Altered miRNA expression can significantly impact disease development and progression by disrupting the normal regulatory networks that control cell behavior. In cancer, specific miRNAs may be downregulated or upregulated, leading to the overexpression of oncogenes or the loss of tumor suppressor genes. This dysregulation contributes to uncontrolled cell proliferation, evasion of apoptosis, and metastasis. Understanding these changes in miRNA expression offers insights into potential therapeutic targets and biomarkers for cancer diagnosis and treatment.

Related terms

RNA interference (RNAi): A biological process where small RNA molecules, including siRNAs and miRNAs, inhibit gene expression by targeting mRNA for degradation or blocking its translation.

mRNA: Messenger RNA, a type of RNA that conveys genetic information from DNA to the ribosome, where proteins are synthesized.

Dicer: An enzyme that processes long double-stranded RNA and precursor miRNAs into functional miRNAs and siRNAs.