miRNA metabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways involving miRNA, microRNA, a class of single-stranded RNA molecules of about 21-23 nucleotides in length, which regulates gene expression. [PMID:17993620]

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level. The miRNA metabolic process encompasses a series of intricate steps that govern the biogenesis, processing, and functional activity of these regulatory molecules.

The journey of miRNA begins with the transcription of primary miRNA (pri-miRNA) transcripts by RNA polymerase II. These long, hairpin-shaped transcripts are subsequently processed by the Drosha-DGCR8 complex, a nuclear ribonuclease. Drosha cleaves the pri-miRNA to produce a shorter precursor miRNA (pre-miRNA), which is transported out of the nucleus into the cytoplasm.

In the cytoplasm, the pre-miRNA encounters another key player, the RNase III enzyme Dicer. Dicer removes the terminal loop of the pre-miRNA, generating a mature miRNA duplex with a characteristic 2-nucleotide overhang at the 3’ end. The miRNA duplex is then unwound, with one strand becoming incorporated into the RNA-induced silencing complex (RISC), while the other strand is typically degraded.

The miRNA-loaded RISC complex then seeks out its target mRNA, guided by sequence complementarity between the miRNA and the 3’ untranslated region (UTR) of the target mRNA. Perfect complementarity often leads to target mRNA degradation, while partial complementarity typically results in translational repression, preventing the target protein from being synthesized.

The miRNA metabolic process is tightly regulated, ensuring precise control over gene expression. Several factors influence this process, including:

- Transcriptional regulation: The expression of miRNA genes is regulated at the transcriptional level by various transcription factors and signaling pathways.
- Post-transcriptional modifications: miRNA transcripts undergo a range of post-transcriptional modifications, such as methylation and adenylation, which can influence their stability and activity.
- Cellular context: The levels and activity of miRNA processing machinery and target mRNAs can vary significantly depending on the cell type and developmental stage.

The miRNA metabolic process is essential for a wide range of cellular functions, including development, differentiation, proliferation, and immunity. Dysregulation of this process can contribute to various diseases, including cancer, cardiovascular disease, and neurodegenerative disorders.

This complex interplay of molecular events ensures the precise and efficient regulation of gene expression by miRNAs, playing a vital role in maintaining cellular homeostasis and normal biological function.'
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Proteins (1)

Compounds (4)