Figure 1.

miRNA biogenesis: miRNA gene transcription generates primary miRNA (pri-miRNA) in the nucleus which is then cleaved by the microprocessor complex (Drosha and DGCR8), liberating pre-miRNA which is exported from the nucleus to the cytoplasm by exportin-5. Pre-miRNA is finally processed by Dicer and TRBP to obtain a mature miRNA with the capacity to bind to target mRNAs. AGO2: argonaute 2, DGCR8: DiGeorge syndrome critical region 8, miRISC: miRNA bound to RNA-induced silencing complex, ORF: origin replication frame, Pol II: polymerase II, and TRBP: the human immunodeficiency virus transactivating.