Schema of miRNA biogenesis. Primary miRNA (pri-miRNA) is transcribed by RNA polymerase II. Drosha-DGCR8 complex cleaves pri-miRNA into hairpin-loop structural pre-miRNA. Pre-miRNA is exported to cytoplasm by exportin-5 and RanGTP, then Dicer processes into miRNA duplex. One of the single strands (mature miRNA) is incorporated into RISC and binds to 3′UTR of target mRNA, following translational repression or mRNA degradation.
