Figure 2.

miRNA pathways in mammalian cells. RNAs are transcribed in the nucleus in the form of a precursor (pri‐miRNA), which is processed by the RNase III Drosha to pre‐miRNA. In this process, the Drosha complexes with the DGCR8 protein. The pre‐miRNA is exported out of the nucleus and into the cytoplasm by Exportin‐5 and cleaved there by Dicer (complexed with TRBP) to form the functional miRNA, which in turn combines with an Argonaut protein (Ago) to form an miRNA–ribonucleoprotein (miRNP) complex. The miRNA can either cause endonucleolytic cleavage of the target mRNA through Ago2 or block translation in the case of partial complementarity. (Figure adapted from Ref. 27.)