Mature miRNA duplexes

Definition

Mature miRNA duplexes are the final, functional forms of microRNAs that result from the processing of primary miRNA transcripts. These duplexes consist of two strands: a guide strand that is incorporated into the RNA-induced silencing complex (RISC) and a passenger strand that is typically degraded. These duplexes play a crucial role in post-transcriptional regulation by targeting messenger RNAs (mRNAs) for degradation or translational repression, thereby influencing gene expression.

5 Must Know Facts For Your Next Test

1. Mature miRNA duplexes are generated from longer primary miRNAs through a series of processing steps involving the enzymes Drosha and Dicer.
2. The guide strand of the mature miRNA duplex is the one that gets incorporated into RISC, where it guides the complex to its target mRNAs.
3. Passenger strands are often degraded shortly after formation of the mature miRNA duplex and do not typically have regulatory functions.
4. Mature miRNAs can target multiple mRNAs, allowing for extensive regulation of gene expression within a cell.
5. The interaction between mature miRNA duplexes and their target mRNAs can lead to translational repression or degradation, significantly influencing cellular functions and developmental processes.

Review Questions

• How are mature miRNA duplexes formed, and what roles do the enzymes Drosha and Dicer play in this process?
  • Mature miRNA duplexes are formed through the processing of primary miRNA transcripts. The enzyme Drosha cleaves the primary transcript in the nucleus, producing precursor miRNAs, which are then transported to the cytoplasm. In the cytoplasm, Dicer further processes these precursors into shorter double-stranded RNA molecules, resulting in mature miRNA duplexes. These processed duplexes consist of a guide strand that will be incorporated into RISC and a passenger strand that is usually degraded.
• Discuss the significance of mature miRNA duplexes in post-transcriptional gene regulation and how they impact cellular functions.
  • Mature miRNA duplexes play a vital role in post-transcriptional gene regulation by binding to complementary sequences on target mRNAs. This interaction can lead to either degradation of the mRNA or inhibition of its translation. By regulating multiple mRNAs simultaneously, mature miRNA duplexes can significantly influence various cellular functions, including development, differentiation, and responses to environmental stress. Their ability to fine-tune gene expression makes them critical players in maintaining cellular homeostasis.
• Evaluate how dysfunction in mature miRNA duplex formation or activity might contribute to disease states.
  • Dysfunction in the formation or activity of mature miRNA duplexes can lead to dysregulation of gene expression, which is linked to various disease states such as cancer, neurodegenerative disorders, and cardiovascular diseases. For example, if a specific miRNA that normally suppresses oncogenes is not produced correctly, it may lead to unchecked cell proliferation and tumorigenesis. Similarly, improper regulation by mature miRNAs can affect neuronal function and contribute to neurodegeneration. Understanding these connections highlights the importance of proper miRNA functioning for overall health.

Related terms

MicroRNA (miRNA): Short, non-coding RNA molecules that regulate gene expression by binding to target mRNAs and inhibiting their translation or promoting their degradation.

RNA-induced silencing complex (RISC): A multi-protein complex that incorporates the guide strand of the mature miRNA duplex and mediates the silencing of target mRNAs.

Dicer: An enzyme that processes primary miRNA transcripts into shorter double-stranded RNA fragments, including mature miRNA duplexes.