Fig. 2.

Biogenesis of miRNA. First, the HCMV miRNA gene is transcribed to generate RNA transcript called primary (pri)-miRNA by RNA polymerase (Pol) II or III. Second, pri-miRNA is processed to precursor (pre)-miRNA by DGCR8 and RNase III Drosha. Third, pre-miRNA is exported to the cytoplasm by Exportin-5, then cropped to the miRNA/miRNA* duplex by the RNase III enzyme Dicer. Finally, one strand of the duplex, miRNA*, is unwound while the other strand is further processed, giving rise to a mature RISC (RNA-induced silencing complex).to bind mRNA, causing mRNA degradation or inhibiting translation