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. Author manuscript; available in PMC: 2009 Feb 26.
Published in final edited form as: J Cell Mol Med. 2008 Oct;12(5B):1811–1819. doi: 10.1111/j.1582-4934.2008.00483.x

Figure 1.

Figure 1

Biogenesis of miRNA and sites of regulation. miRNA is transcribed by RNA polymerase II to produce the primary precursor miRNA (I, pri-miRNA). The pri-miRNA is trimmed by Drosha/DGCR8 in the nucleus to produce the ~ 70 nt precursor miRNA (II, pre-miRNA). The pre-miRNA is transported to the cytoplasm by Exportin 5 where it interacts with the RNAse III Dicer and TRBP/Loquacious to produce the ~ 21nt miRNA: miRNA* duplex (III). The miRNA strand (IV) is loaded into RNA-induced silencing complex (RISC) and the miRNA* strand is typically degraded. Possible sites of regulation include: A, A-I editing; B, SNPs or mutations; C, regulation of processing by miRNA-specific factors; D, altered levels of Drosha; E, altered levels of Dicer; F, sequestration into subcellular organelles.