title: Free mRNA in excess upon polysome dissociation is a scaffold for protein multimerization to form stress granules.
abstract: The sequence of events leading to stress granule assembly in stressed cells remains elusive. We show here, using isotope labeling and ion microprobe, that proportionally more RNA than proteins are present in stress granules than in surrounding cytoplasm. We further demonstrate that the delivery of single strand polynucleotides, mRNA and ssDNA, to the cytoplasm can trigger stress granule assembly. On the other hand, increasing the cytoplasmic level of mRNA-binding proteins like YB-1 can directly prevent the aggregation of mRNA by forming isolated mRNPs, as evidenced by atomic force microscopy. Interestingly, we also discovered that enucleated cells do form stress granules, demonstrating that the translocation to the cytoplasm of nuclear prion-like RNA-binding proteins like TIA-1 is dispensable for stress granule assembly. The results lead to an alternative view on stress granule formation based on the following sequence of events: after the massive dissociation of polysomes during stress, mRNA-stabilizing proteins like YB-1 are outnumbered by the burst of nonpolysomal mRNA. mRNA freed of ribosomes thus becomes accessible to mRNA-binding aggregation-prone proteins or misfolded proteins, which induces stress granule formation. Within the frame of this model, the shuttling of nuclear mRNA-stabilizing proteins to the cytoplasm could dissociate stress granules or prevent their assembly.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR829; Université Evry-Val d'Essonne, Evry 91025, France.
authors.forename: Ouissame
authors.initials: O
authors.lastname: Bounedjah
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR829; Université Evry-Val d'Essonne, Evry 91025, France.
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Desforges
authors.affiliation: Institut Curie, INSERM, U759, 91405 Orsay cedex, France.
authors.forename: Ting-Di
authors.initials: TD
authors.lastname: Wu
authors.affiliation: Centre National de la Recherche Scientifique (CNRS), UMR 8126; University of Paris Sud, 94805 Villejuif, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Pioche-Durieu
authors.affiliation: Institut Curie, INSERM, U759, 91405 Orsay cedex, France.
authors.forename: Sergio
authors.initials: S
authors.lastname: Marco
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR829; Université Evry-Val d'Essonne, Evry 91025, France.
authors.forename: Loic
authors.initials: L
authors.lastname: Hamon
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR829; Université Evry-Val d'Essonne, Evry 91025, France.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Curmi
authors.affiliation: Institut Curie, INSERM, U759, 91405 Orsay cedex, France.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Guerquin-Kern
authors.affiliation: Centre National de la Recherche Scientifique (CNRS), UMR 8126; University of Paris Sud, 94805 Villejuif, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Piétrement
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR829; Université Evry-Val d'Essonne, Evry 91025, France david.pastre@univ-evry.fr.
authors.forename: David
authors.initials: D
authors.lastname: Pastré
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003593:Cytoplasm / Q000737:chemistry; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000037:antagonists & inhibitors; D011132:Polyribosomes / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D055503:Protein Multimerization; D021381:Protein Transport; D011506:Proteins / Q000032:analysis; D011691:Puromycin / Q000494:pharmacology; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger / Q000378:metabolism* / Q000502:physiology; D016601:RNA-Binding Proteins / Q000378:metabolism*; D051381:Rats; D013312:Stress, Physiological
chemical_list: D004277:DNA, Single-Stranded; D018840:HSP70 Heat-Shock Proteins; D061988:Proteasome Inhibitors; D011506:Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011691:Puromycin; D012313:RNA