Figure 3.
Biogenesis of miRNA and gene expression. miRNAs are transcribed from miRNA genes to long primary transcripts (pri-miRNAs) characterized by a hairpin structure, and are then processed to pre-miRNAs (around 70-nucleotide long) in the nucleus. After being transported into the cytoplasm, pre-miRNAs are cleaved by Dicer and finally matured into miRNA of 22-24 nucleotides. A partial binding of miRNAs to their complementary mRNAs leads to translational repression; a complete binding of miRNAs to their complementary mRNAs results in the cleavage of the targeted mRNAs.