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. 2020 Sep 9;19:136. doi: 10.1186/s12933-020-01107-3

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© The Author(s) 2020

Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

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Fig. 1 — Summarized scheme of miRNAs biogenesis and mechanism of action: In the nucleus, Pol II and Pol III RNA polymerases transcribe the coding sequences of miRNAs. Drosha binds to DGCR8 cofactor to catalyze the formation of pre-miRNA. Pre-miRNA is then translocated by the exportins system from the nucleus to the cytoplasm, where it is then cleaved by the Dicer-TRBP complex to form a 22nt-dsRNA. Within the cytoplasm, the 22nt-dsRNA interacts with AGO proteins to form the RISC complex, while the passenger strand is degraded. The 22nt-RNA guide chain constitutes a mature miRNA that guides the RISC complex towards the 3-UTR regions of the mRNA targets. This interaction either represses their translation or induces their degradation. Pol: polymerase; Drosha: ribonuclease III double-stranded RNA-specific endoribonuclease; DGCR8: DiGeorge syndrome chromosomal region 8; Dicer: helicase with RNase motif; TRBP: TAR RNA binding protein; AGO: Argonaute protein; RISC: RNA-induced silencing complex; UTR: untranslated region