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MicroRNAs (miRNAs) are short (~22 nucleotides) single-stranded RNA molecules that primarily function to negatively regulate gene expression at the post-transcriptional level. miRNAs have thus been implicated in the regulation of a wide variety of normal cell functions and pathophysiological conditions. The miRNA machinery consists of a series of protein complexes which act to: (1) cleave the precursor-miRNA hairpin from its primary transcript (i.e. DROSHA and DGCR8); (2) traffic the miRNA hairpin between nucleus and cytoplasm (i.e. XPO5); (3) remove the loop sequence of the hairpin by a second nucleolytic cleavage reaction (i.e. DICER1); (4) facilitate loading of the mature miRNA sequence into an Argonaute protein (typically AGO2) as part of the RNA-Induced Silencing Complex (RISC); (5) guide the loaded RISC complex to complementary, or semi-complementary, target transcripts and (6) facilitate gene silencing via one of several possible mechanisms.

Original publication




Journal article


Adv Exp Med Biol

Publication Date





15 - 30


AGO2, Argonaute, DGCR8, DICER1, Dicer, Drosha, Exportin-5, XPO5, microRNA, Animals, Argonaute Proteins, Carboxypeptidases, DEAD-box RNA Helicases, Gene Expression Regulation, Humans, Karyopherins, MicroRNAs, Models, Molecular, Nucleic Acid Conformation, Protein Conformation, RNA Cleavage, RNA Transport, Ribonuclease III