Figure 1.

miRNA biogenesis. Red arrows indicate steps altered in prostate cancer (PC). The standard steps of the biogenesis are indicated with the black arrows. miRNAs are transcribed by RNA Polymerase (Pol) II or III to generate initially a sequence, called pri-miRNA, of approximately 200 bp. Afterwards, Drosha RNase III cleaves the pri-miRNA into a 100 nt sequence, called pre-miRNA, which is then exported out of the nucleus by exportin 5/6 (XPO5/6) and RanGTP. Another RNAse III, Dicer, generates a double stranded miRNA containing a miRNA/miRNA* duplex. The mature miRNA is loaded into the RNA-induced silencing complex (RISC) complex. The complementarity of the sequence between the miRNA and the mRNA leads either to translational repression if matching is imperfect, mRNA degradation if the seed is completely recognized, or translational activation, which occurs less frequently.