primary miRNA processing
Definition
Target type: biologicalprocess
A process involved in the conversion of a primary microRNA transcript into a pre-microRNA molecule. [GOC:sl, PMID:15211354, PMID:25799998]
Primary miRNA processing is a crucial step in the biogenesis of mature microRNAs (miRNAs), small non-coding RNA molecules that play critical roles in regulating gene expression. This process occurs within the nucleus and involves a series of enzymatic steps:
1. **Transcription:** The primary miRNA transcript (pri-miRNA) is transcribed from a gene by RNA polymerase II. Pri-miRNAs are typically long, hairpin-shaped RNA molecules with a 5’ cap and a 3’ poly-A tail.
2. **Recognition by DGCR8 and Drosha:** The pri-miRNA is recognized by a complex of two proteins: DGCR8 and Drosha. DGCR8, a double-stranded RNA-binding protein, binds to the stem region of the pri-miRNA hairpin. Drosha, a RNase III enzyme, then cleaves the pri-miRNA at the base of the stem, releasing a precursor miRNA (pre-miRNA) of approximately 70 nucleotides.
3. **Export to the cytoplasm:** The pre-miRNA is then exported from the nucleus to the cytoplasm by the nuclear export protein Exportin-5. This export is dependent on the presence of a 2-nucleotide 3’ overhang on the pre-miRNA.
4. **Processing by Dicer:** In the cytoplasm, the pre-miRNA is further processed by another RNase III enzyme called Dicer. Dicer removes the terminal loop of the pre-miRNA hairpin and cleaves it into a mature miRNA duplex of approximately 22 nucleotides.
5. **Unwinding and incorporation into RISC:** The miRNA duplex is then unwound by a helicase, and one of the strands (the guide strand) is incorporated into the RNA-induced silencing complex (RISC). The other strand (the passenger strand) is typically degraded.
The mature miRNA within RISC can then bind to complementary sequences in target mRNAs, leading to their degradation or translational repression. This intricate process ensures the precise regulation of gene expression by miRNAs, playing essential roles in various cellular processes, including development, differentiation, and disease pathogenesis.'
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Proteins (1)
| Protein | Definition | Taxonomy |
|---|---|---|
| N6-adenosine-methyltransferase catalytic subunit | An N6-adenosine-methyltransferase catalytic subunit that is encoded in the genome of human. [PRO:DNx, UniProtKB:Q86U44] | Homo sapiens (human) |
Compounds (1)
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| s-adenosylhomocysteine | S-adenosyl-L-homocysteine : An organic sulfide that is the S-adenosyl derivative of L-homocysteine. S-Adenosylhomocysteine: 5'-S-(3-Amino-3-carboxypropyl)-5'-thioadenosine. Formed from S-adenosylmethionine after transmethylation reactions. | adenosines; amino acid zwitterion; homocysteine derivative; homocysteines; organic sulfide | cofactor; EC 2.1.1.72 [site-specific DNA-methyltransferase (adenine-specific)] inhibitor; EC 2.1.1.79 (cyclopropane-fatty-acyl-phospholipid synthase) inhibitor; epitope; fundamental metabolite |