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. Author manuscript; available in PMC: 2014 Jul 17.
Published in final edited form as: Cold Spring Harb Protoc. 2013 Nov 1;2013(11):10.1101/pdb.top069856 pdb.top069856. doi: 10.1101/pdb.top069856

FIGURE 1.

FIGURE 1

MicroRNA biogenesis and introduction of exogenous RNAi triggers. Endogenous miRNAs are usually transcribed by RNA Pol II to produce primary miRNA transcripts (pri-miRNA). Pri-miRNAs are processed in the nucleus by the Drosha/DGCR8 complex to produce precursor miRNAs (pre-miRNAs) that are subsequently exported to the cytoplasm (left panel). Cytoplasmic pre-miRNAs undergo further cleavage by Dicer, yielding a 22-nucleotide double-stranded RNA duplex that is incorporated into the RISC complex to mediate mRNA silencing. Exogenous RNAi triggers (right panel, in red) can mimic each of these stages: miR30-based shRNAs are incorporated into the pathway at the Drosha/DGCR8 processing step, stem loop shRNAs resemble pre-miRNAs and are exported to the cytoplasm, and synthetic siRNA duplexes mimic Dicer cleavage products.