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. Author manuscript; available in PMC: 2016 Oct 1.
Published in final edited form as: Periodontol 2000. 2015 Oct;69(1):201–220. doi: 10.1111/prd.12095

Fig. 1. miRNA biogenesis and action.

Fig. 1

The figure shows the principal events of the canonical miRNA biogenesis pathway and their actions in human cells. First, primary-miRNA (pri-miRNA) is transcribed by RNA polymerases II or III from either intronic regions within protein-coding genes or intergenic regions. Second, pri-miRNA is cropped by the Microprocessor complex (MPC) unit comprising of Drosha and DGCR8 (Pasha) into precursor-miRNA (pre-miRNA). Third, pre-miRNAs are exported from the nucleus to the cytoplasm by Exportin-5, where pre-miRNA is further cleaved by Dicer into a short guide/passenger strand (miRNA/*miRNA) duplex. One of the strands is incorporated in the miRNA-induced silencing complex (miRISC) with GW182 and an Argonaute protein, most frequently Argonaute −2. The miRISC-attached miRNA binds to the 3’- untranslated region of a target mRNA, the CCR4-Not complex recruited by GW182 leads to translational inhibition of the mRNA and/or to deadenylation of the mRNA´s poly(A) tail and its subsequent degradation.