title: Ribosomal S6 kinase is activated as an early event in preemergence development of encysted embryos of Artemia salina.
abstract: Dormant Artemia salina cysts contain desiccated gastrulae that are metabolically inactive, and physiologically arrested. Following rehydration, embryos resume development via alterations in protein expression, in the complete absence of cell division. In mammals, activation of p70 ribosomal S6 kinase (p70S6k) has been implicated in translational control, in particular the selective up-regulation of translation of mRNAs with polypyrimidine tracts at their 5' start sites. We therefore investigated ribosomal S6 kinase activity in preemergence development. We demonstrate that an S6 kinase activity is rapidly stimulated (within < 15 min) following rehydration and coincides with the onset of ribosomal S6 subunit phosphorylation. This S6 kinase activity displays chromatographic and biochemical characteristics that are similar to those of mammalian p70S6k. Partially purified Artemia S6 kinase was inactivated by treatment with protein phosphatase 2A. Activation of S6 kinase activity was shown to be due to an enzymatic step(s), and not simply rehydration of stored, active enzyme. The temporal profile of activation of S6 kinase activity is compatible with a regulatory function for p70S6k in early preemergence development of encysted Artemia. These studies identify activated Artemia cysts as a system for biochemical studies of p70S6k regulation.
authors.affiliation: Howard Hughes Medical Institute, Department of Medicine, University of Virginia, Charlottesville 22908-0001, USA.
authors.forename: K
authors.initials: K
authors.lastname: Malarkey
authors.forename: K J
authors.initials: KJ
authors.lastname: Coker
authors.forename: T W
authors.initials: TW
authors.lastname: Sturgill
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001156:Artemia / Q000196:embryology*; D015153:Blotting, Western; D002853:Chromatography, Liquid / Q000379:methods; D003600:Cytosol / Q000201:enzymology; D003681:Dehydration; D004625:Embryo, Nonmammalian / Q000201:enzymology / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000494:pharmacology; D054648:Protein Phosphatase 2; D019893:Ribosomal Protein S6 Kinases / Q000187:drug effects / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D009842:Oligopeptides; C037642:kemptide; D019893:Ribosomal Protein S6 Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2