title: Direct binding of the Alu binding protein dimer SRP9/14 to 40S ribosomal subunits promotes stress granule formation and is regulated by Alu RNA.
abstract: Stress granules (SGs) are formed in response to stress, contain mRNAs, 40S ribosomal subunits, initiation factors, RNA-binding and signaling proteins, and promote cell survival. Our study describes a novel function of the protein heterodimer SRP9/14 and Alu RNA in SG formation and disassembly. In human cells, SRP9/14 exists assembled into SRP, bound to Alu RNA and as a free protein. SRP9/14, but not SRP, localizes to SGs following arsenite or hippuristanol treatment. Depletion of the protein decreases SG size and the number of SG-positive cells. Localization and function of SRP9/14 in SGs depend primarily on its ability to bind directly to the 40S subunit. Binding of SRP9/14 to 40S and Alu RNA is mutually exclusive indicating that the protein alone is bound to 40S in SGs and that Alu RNA might competitively regulate 40S binding. Indeed, by changing the effective Alu RNA concentration in the cell or by expressing an Alu RNA binding-defective protein we were able to influence SG formation and disassembly. Our findings suggest a model in which SRP9/14 binding to 40S promotes SG formation whereas the increase in cytoplasmic Alu RNA following stress promotes disassembly of SGs by disengaging SRP9/14 from 40S.
authors.affiliation: Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Berger
authors.affiliation: Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Ivanova
authors.affiliation: Département de biologie moléculaire, biochimie médicale et pathologie Université Laval, 4 Québec G1V0A6, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Gareau
authors.affiliation: Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Scherrer
authors.affiliation: Département de biologie moléculaire, biochimie médicale et pathologie Université Laval, 4 Québec G1V0A6, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Mazroui
authors.affiliation: Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland Katharina.Strub@unige.ch.
authors.forename: K
authors.initials: K
authors.lastname: Strub
mesh_terms: D020087:Alu Elements; D000818:Animals; D018053:Arsenites / Q000494:pharmacology; D001667:Binding, Competitive; D003594:Cytoplasmic Granules / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D054682:Ribosome Subunits, Small, Eukaryotic / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000737:chemistry / Q000378:metabolism*; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D018053:Arsenites; C490326:SRP14 protein, human; C117074:SRP19 protein, human; D018271:Signal Recognition Particle; D012313:RNA; C015001:arsenite