FIG. 6.

Biogenesis of microRNA and its role in the regulation of gene expression. The biogenesis of mature (functional) miRNA from its miRNA gene involves both the nucleus and cytoplasm in mammalian cells. A single-stranded mature (functional) miRNA with approximately 22 nucleotides (nt) binds the 3’-untranslated region of the target mRNA. This usually results in decreased protein synthesis through induction of mRNA deadenylation, reduction of translation initiation, and inhibition of translation elongation. DGCR8, associated protein DGCR8 of Drosha (also known as Pasha); TRBP (transacting RNA-binding protein); miRNA*, passenger strand miRNA for degradation; RISC, RNA-induced silencing complex (RISC) containing several components, including Argonaute proteins, PW182 protein, and fragile X mental retardation protein.