4g0m
From Proteopedia
Crystal structure of Arabidopsis thaliana AGO2 MID domain
Structural highlights
Function[AGO2_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 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. Associates mainly with siRNAs of 21 nucleotide in length and preferentially recruits small RNAs with a 5' terminal adenosine. Probably involved in antiviral RNA silencing. Associates with siRNA derived from cucumber mosaic virus (CMV). Targeted by turnip yellows virus (TuYV) protein P0 (via F-box-like domain) for probable proteasome degradation and thereby inactivating AGO2 function in RNA silencing. Required to direct NERD-dependent DNA methylation and silencing.[1] [2] [3] [4] [5] Publication Abstract from PubMedThe 5'-nucleotide of small RNAs associates directly with the MID domain of Argonaute (AGO) proteins. In humans, the identity of the 5'-base is sensed by the MID domain nucleotide specificity loop and regulates the integrity of miRNAs. In Arabidopsis thaliana, the 5'-nucleotide also controls sorting of small RNAs into the appropriate member of the AGO family; however, the structural basis for this mechanism is unknown. Here, we present crystal structures of the MID domain from three Arabidopsis AGOs, AtAGO1, AtAGO2 and AtAGO5, and characterize their interactions with nucleoside monophosphates (NMPs). In AtAGOs, the nucleotide specificity loop also senses the identity of the 5'-nucleotide but uses more diverse modes of recognition owing to the greater complexity of small RNAs found in plants. Binding analyses of these interactions reveal a strong correlation between their affinities and evolutionary conservation. Arabidopsis Argonaute MID domains use their nucleotide specificity loop to sort small RNAs.,Frank F, Hauver J, Sonenberg N, Nagar B EMBO J. 2012 Jul 31. doi: 10.1038/emboj.2012.204. PMID:22850669[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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