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. Author manuscript; available in PMC: 2017 Oct 1.
Published in final edited form as: Best Pract Res Clin Endocrinol Metab. 2016 Aug 1;30(5):577–590. doi: 10.1016/j.beem.2016.07.005

Figure 1. miRNA biogenesis, cellular release and paracrine cell-to-cell communication.

Figure 1

MiRNAs are typically transcribed by polymerase II (Pol II) as primary miRNA (pri-miRNA). Pri-miRNAs are cleaved by RNase III-type enzyme Drosha to produce hairpin-structured precursors (pre-miRNAs). Pre-miRNAs are transported to cytoplasm, the Dicer complex removes the loop region from pre-miRNAs to generate an imperfect duplex miRNA. Mature miRNA is bound by Argonaute to form a RNA-induced silencing complex (RISC). In the cytoplasm, pre-miRNAs or mature miRNAs can also incorporate into multivesicular bodies (MVBs). miRNA can be released from cells through release of exosomes derived from MVB’s, microvesicles derived from plasma membranes or within apoptotic bodies. They can also be associated and released with RNA-binding protein complexes (RBP) or high density lipoproteins (HDL). Extracellular miRNAs can be transferred to recipient cells and bind to their target messenger RNAs (mRNAs) to repress their translation or induce their degradation.