Fig. 2.

Biogenesis and function of microRNA in controlling process relevant cellular properties.

Biogenesis: (1) canonically, microRNAs are transcribed by RNA polymerase II to generate primary transcript (pri-microRNAs), long capped and polyadenylated RNAs with hairpin structure. (2) First processing steps are mediated by the microprocessor complex, consisting of Drosha and DiGeorge syndrome critical region 8 (DGCR8) which produces a ~ 70 nt hairpin structured RNA known as a precursor-microRNA (pre-microRNA). (3) Pre-microRNA are exported from the nucleus by the Exportin-5–Ran–GTP complex. (4) In the cytosol further processing occurs by Dicer together with TRBP and Argonaut proteins 1–4 (AGO), resulting in the active microRNA-induced silencing complex (miRISC). (5) miRISC binds to its target mRNA, mediating translational inhibition or cleavage. Function of microRNA: selected examples of microRNA discussed in the text that influence process relevant cellular processing by post-transcriptionally controlling expression of genes, highlighting the complexity of the regulatory network and interactions between the different pathways.