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Table 1 Common molecules in microRNA biogenesis and function

From: Sex differences in microRNA regulation of gene expression: no smoke, just miRs

Molecule Function Reference
Primary microRNA (pri-miR)‘ Initial transcription from independent (not intronic) miR gene results in a pri-miR, A pri-miR is often multiple kilobases in length and may encode more then one mature miRNA. [12]
Pre-microRNA (pre-miR) Processing of pri-miR by microprocessor results in pre-miR. PremiRs are 60–70 bp double stranded RNAs with intramolecular sequence complementarity, so that they form stem-loop structures. [20]
microRNA (miR) Mature single stranded RNA 20–22 bp in length. Exists in complex w ith Argonaute and accessory proteins as part of the RISC complex, providing target specificity. [20]
Mirtron miRs located within introns of protein coding genes, Transcribed as part of their host genes primary transcript, but are cleaved from this during mRNA splicing, resulting in a pre-miR. [15]
Microprocessor complex Multi-protein complex, containing the obligate members Drosha and DGCR8. Responsible for cleaving stem-loop structures from pn-miR, resulting in pre-miRNA. [52]
Drosha RNase III protein. One of two obligate members of the microprocessor complex. [73]
DGCR8 Double stranded RNA binding domain protein. One of two obligate members of the microprocessor complex. [73]
Dicer RNase Ill-like protein. Cleaves ‘loops of stem-loop from pre-miR, resulting in a 20–22 bp miRNA duplex. Assists in loading one strand of this duplex, the guide strand, into RISC complex. [12]
RISC RNA induced silencing complex (RISC) is a multi-protein complex containing Argo bound to a single stranded miR. Association of the RISC complex with a mRNA target leads to mRNAdestabilization/degradation, either through direct RNase actions of Argo II or the activity of other recruited accessory proteins. [74]
Argonaute (Argo) Component of the RISC complex, it acts at the interface between a miR and mRNA target. There are four mammalian Argonautes, though only Argo II has RNase activity. [16] [74]