title: Quantitative analysis of Argonaute protein reveals microRNA-dependent localization to stress granules.
abstract: Argonaute proteins associate with microRNAs (miRNAs) that bind mRNAs through partial base-pairings to primarily repress translation in animals. A fraction of Argonaute proteins and miRNAs biochemically cosediment with polyribosomes, yet another fraction paradoxically accumulates in ribosome-free processing bodies (PBs) in the cytoplasm. In this report, we give a quantitative account of the Argonaute protein localization and dynamics in living cells in different cellular states. We find that the majority of Argonaute is distributed diffusely in the cytoplasm, and, when cells are subjected to stress, Argonaute proteins accumulate to newly assembled structures known as stress granules (SGs) in addition to PBs. Argonaute proteins displayed distinct kinetics at different structures: exchange faster at SGs and much slower at PBs. Further, miRNAs are required for the Argonaute protein localization to SGs but not PBs. These quantitative kinetic data provide insights into miRNA-mediated repression.
authors.affiliation: Center for Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Anthony K L
authors.initials: AK
authors.lastname: Leung
authors.forename: J Mauro
authors.initials: JM
authors.lastname: Calabrese
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Sharp
mesh_terms: D060565:Argonaute Proteins; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000378:metabolism*; D015852:Eukaryotic Initiation Factor-2; D006801:Humans; D007700:Kinetics; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D010448:Peptide Initiation Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: C466422:AGO2 protein, human; D060565:Argonaute Proteins; D015852:Eukaryotic Initiation Factor-2; D035683:MicroRNAs; D010448:Peptide Initiation Factors