PMID:16081530

Citation	Baumberger, N and Baulcombe, DC (2005) Arabidopsis ARGONAUTE1 is an RNA Slicer that selectively recruits microRNAs and short interfering RNAs. Proc. Natl. Acad. Sci. U.S.A. 102:11928-33
Abstract	ARGONAUTE (AGO) RNA-binding proteins are involved in RNA silencing. They bind to short interfering RNAs (siRNAs) and microRNAs (miRNAs) through a conserved PAZ domain, and, in animals, they assemble into a multisubunit RNA-induced silencing complex (RISC). The mammalian AGO2, termed Slicer, directs siRNA- and miRNA-mediated cleavage of a target RNA. In Arabidopsis, there are 10 members of the AGO family, and the AGO1 protein is potentially the Slicer component in different RNA-silencing pathways. Here, we show that AGO1 selectively recruits certain classes of short silencing-related RNA. AGO1 is physically associated with miRNAs, transacting siRNAs, and transgene-derived siRNAs but excludes virus-derived siRNAs and 24-nt siRNAs involved in chromatin silencing. We also show that AGO1 has Slicer activity. It mediates the in vitro cleavage of a mir165 target RNA in a manner that depends on the sequence identity of amino acid residues in the PIWI domain that are predicted by homology with animal Slicer-competent AGO proteins to constitute the RNase catalytic center. However, unlike animals, we find no evidence that AGO1 Slicer is in a high molecular weight RNA-induced silencing complex. The Slicer activity fractionates as a complex of approximately 150 kDa that likely constitutes the AGO1 protein and associated RNA without any other proteins. Based on sequence similarity, we predict that other Arabidopsis AGOs might have a similar catalytic activity but recruit different subsets of siRNAs or miRNAs.
Links	PubMed PMC1182554 Online version:10.1073/pnas.0505461102
Keywords	Amino Acid Sequence; Arabidopsis/chemistry; Arabidopsis/genetics; Arabidopsis/growth & development; Arabidopsis/metabolism; Arabidopsis Proteins/chemistry; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Argonaute Proteins; Epitopes/genetics; Epitopes/metabolism; Genes, Reporter/genetics; MicroRNAs/genetics; MicroRNAs/metabolism; Molecular Sequence Data; Molecular Weight; Plants, Genetically Modified; Protein Binding; RNA, Small Interfering/genetics; RNA, Small Interfering/metabolism; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Sequence Alignment; Substrate Specificity
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