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. |