Microparticles and microRNAs of endothelial progenitor cells ameliorate acute kidney injury  Markus Bitzer, Iddo Z. Ben-Dov, Thomas Thum  Kidney International  Volume 82, Issue 4, Pages 375-377 (August 2012) DOI: 10.1038/ki.2012.152 Copyright © 2012 International Society of Nephrology Terms and Conditions

Figure 1 MicroRNA biogenesis and transport. MicroRNAs (miRNAs) are transcribed from miRNA genes that are similar to protein-coding genes into primary miRNAs (pri-miRNAs; several hundreds of nucleotides long, harboring 5′ cap and 3′ poly-A tail), further processed into pre-miRNAs (∼70 nucleotides long with a characteristic hairpin loop) by the RNase III enzyme Drosha in the nucleus, and shuttled into the cytoplasm through Exportin 5, where the RNase III enzyme Dicer generates mature miRNAs and passenger strand. Mature miRNAs are then incorporated into the RNA-induced silencing complex (RISC), where target mRNAs are either degraded or translationally repressed through partial sequence complementation. In the extracellular space, miRNAs have been detected in microvesicles and exosomes, and bound to extracellular particles and proteins. The RISC has been found to be associated with the membranes of multivesicular bodies (MVBs) derived from the endosome and in microvesicles; it is probably also in exosomes. The mechanisms underlying uptake of miRNAs into vesicles and the release from the vesicles in target cells are largely unknown. Kidney International 2012 82, 375-377DOI: (10.1038/ki.2012.152) Copyright © 2012 International Society of Nephrology Terms and Conditions