7swq
Cryo-EM structure of Arabidopsis Ago10-guide-target RNA complex in a bent duplex conformation
Structural highlights
FunctionAGO10_ARATH Involved in RNA-mediated post-transcriptional gene silencing (PTGS). Main component of the RNA-induced silencing complex (RISC) that binds to a short guide RNA such as a microRNA (miRNA) or small interfering RNA (siRNA). RISC uses the mature miRNA or siRNA as a guide for slicer-directed cleavage of homologous mRNAs to repress gene expression. Required for reliable formation of primary and axillary shoot apical meristems. Specifies leaf adaxial identity by repressing the miR165 and miR166 microRNAs in the embryonic shoot apex, in the shoot apical meristem (SAM) and leaf. Represses the microRNA miR398 which targets CCS1 chaperone mRNAs for translational inhibition. Acts as a negative regulator of AGO1 protein level. Like AGO1, is required for stem cell function and organ polarity. Unlike AGO1, is not subjected to small RNA-mediated repression itself. Essential for multiple processes in development. Coregulates, with GATA18/HAN, the shoot apical meristem (SAM) organization (PubMed:26390296).[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedArgonaute (AGO) proteins use small RNAs to recognize transcripts targeted for silencing in plants and animals. Many AGOs cleave target RNAs using an endoribonuclease activity termed 'slicing'. Slicing by DNA-guided prokaryotic AGOs has been studied in detail, but structural insights into RNA-guided slicing by eukaryotic AGOs are lacking. Here we present cryogenic electron microscopy structures of the Arabidopsis thaliana Argonaute10 (AtAgo10)-guide RNA complex with and without a target RNA representing a slicing substrate. The AtAgo10-guide-target complex adopts slicing-competent and slicing-incompetent conformations that are unlike known prokaryotic AGO structures. AtAgo10 slicing activity is licensed by docking target (t) nucleotides t9-t13 into a surface channel containing the AGO endoribonuclease active site. A beta-hairpin in the L1 domain secures the t9-t13 segment and coordinates t9-t13 docking with extended guide-target pairing. Results show that prokaryotic and eukaryotic AGOs use distinct mechanisms for achieving target slicing and provide insights into small interfering RNA potency. Structural basis for RNA slicing by a plant Argonaute.,Xiao Y, Maeda S, Otomo T, MacRae IJ Nat Struct Mol Biol. 2023 Jun;30(6):778-784. doi: 10.1038/s41594-023-00989-7. , Epub 2023 May 1. PMID:37127820[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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