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Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Wertheim cung cấp cho các bạn kiến thức về ngành y đề tài: MicroRNA processing without Dicer. | Dueck and Meister Genome Biology 2010 11 123 http genomebiology.eom 2010 11 6 123 w Genome Biology RESEARCH HIGHLIGHT L__ MicroRNA processing without Dicer Anne Dueck1 and Gunter Meister -2 Abstract The canonical processing of precursor microRNAs requires the endonuclease Dicer. A recent study shows that microRNAs can be processed independently of Dicer but instead require Argonaute 2. MicroRNAs miRNAs and their manifold functions in regulating gene expression have been the focus of intensive research over the past decade 1 . miRNAs are endogenously expressed small RNAs that undergo extensive processing and finally become part of an effector complex known as the RNA-induced silencing complex RISC or miRNA-containing ribonucleoprotein miRNP 2 3 . miRNAs are transcribed from RNA polymerase II or rarely RNA polymerase III promoters yielding primary transcripts pri-miRNAs that are processed by a microprocessor complex containing the RNase III enzyme Drosha. The resulting stem-loop structured miRNA precursor pre-miRNA is exported to the cytoplasm where another RNase III enzyme Dicer cleaves off the loop of the hairpin to produce a short double-stranded RNA 20 to 25 nucleotides with a two-nucleotide overhang at the 3 end and a 5 phosphate group. One of the two RNA strands is incorporated into a RISC and acts as the functional mature miRNA. The other strand known as the passenger strand or the star strand miRNA is destabilized and removed from the cell 4 . A member of the Argonaute Ago protein family serves as the direct interaction partner of the miRNA within the RISC. The miRNA acts to guide the RISC to its target mRNA while the Ago protein complex represses mRNA translation or induces deadenylation-dependent mRNA decay leading to silencing of gene expression. In a recent paper in Nature Gregory Hannon and colleagues Cheloufi et al. 5 describe a novel role for an Ago protein with endonuclease activity in the processing of the mouse miRNA miR-451 which
