ALE-HSA21

MicroRNAs (miRNAs) are endogenously expressed small (20–25 nucleotides) single-stranded non-coding RNAs, that are involved in post-transcriptional regulation of gene expression binding a short region (seed) of mRNAs – a complementary sequence usually located in 3′ UTRs - affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II (RNAPlI) into capped and polyadenylated primary miRNA transcripts (pri-miRNAs) which are further processed into miRNA precursors (pre-miRNAs) in the nucleus by the Drosha ribonuclease III enzyme to produce an approximately 70-nt stem-loop precursor miRNA (pre-miRNA). Pre-miRNAs are then exported to the cytoplasm by Exportin 5 and cleaved by the cytoplasmic Dicer ribonuclease to generate the mature miRNA and antisense miRNA star (miRNA*) products. mature miRNA is incorporated into the Argonaute (Ago) protein, a key component of the RNA-induced silencing complex (RISC) complex, which recognizes target mRNAs through imperfect base pairing with the miRNA and most commonly results in translational inhibition or destabilization of the target mRNA.