Unravelling the ultrastructure of stress granules and associated P-bodies in human cells.
Stress granules are cytoplasmic ribonucleoprotein granules formed following various stresses that inhibit translation. They are thought to help protecting untranslated mRNAs until stress relief. Stress granules are frequently seen adjacent to P-bodies, which are involved in mRNA degradation and storage. We have previously shown in live cells that stress granule assembly often takes place in the vicinity of pre-existing P-bodies, suggesting that these two compartments are structurally related. Here we provide the first ultrastructural characterization of stress granules in eukaryotic cells by electron microscopy. Stress granules resulting from oxidative stress, heat-shock or protein overexpression are loosely organised fibrillo-granular aggregates of a moderate electron density, whereas P-bodies are denser and fibrillar. By in situ hybridization at the electron microscopic level, we show that stress granules are enriched in poly(A)(+) mRNAs, although these represent a minor fraction of the cellular mRNAs. Finally, we show that, despite close contact with P-bodies, both domains remain structurally distinct and do not interdigitate.
Souquere
Sylvie
S
CNRS FRE2937, Institut André Lwoff, 94800 Villejuif, France.
Mollet
Stéphanie
S
Kress
Michel
M
Dautry
François
F
Pierron
Gérard
G
Weil
Dominique
D
D018053:Arsenites / Q000633:toxicity; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D018869:Heat-Shock Response / Q000187:drug effects; D006801:Humans; D017403:In Situ Hybridization; D039102:Poly(A)-Binding Proteins / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D012313:RNA / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects; D000074019:T-Cell Intracellular Antigen-1
D018053:Arsenites; D039102:Poly(A)-Binding Proteins; D011993:Recombinant Fusion Proteins; D000074019:T-Cell Intracellular Antigen-1; C071558:TIA1 protein, human; D049452:Green Fluorescent Proteins; D012313:RNA; C015001:arsenite