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19 (7): 1516-1524

Copyright © 2000 by the European Molecular Biology Organization.

The EMBO Journal Vol. 19,pp. 1516-1524, 2000, Copyright © European Molecular Biology Organization

Hsp90 is required for c-Mos activation and biphasic MAP kinase activation in Xenopus oocytes

D.L. Fisher, E. Mandart and M. Dorée

CNRS-CRBM, 1919 Route de Mende, 34293 Montpellier, Cedex 05, France
1   Present address: IGH, CNRS-UPR 1142, 141 rue de la Candonille, 34396 Montpellier, Cedex 05, France
2   Corresponding author
   e-mail doree{at}crbm.cnrs-mop.fr

During Xenopus oocyte maturation, the Mos protein kinase is synthesized and activates the MAP kinase cascade. In this report, we demonstrate that the synthesis and activation of Mos are two separable processes. We find that Hsp90 function is required for activation and phosphorylation of Mos and full activation of the MAP kinase cascade. Once Mos is activated, Hsp90 function is no longer required. We show that Mos interacts with both Hsp90 and Hsp70, and that there is an inverse relationship between association of Mos with these two chaperones. We propose that Mos protein kinase is activated by a novel mechanism involving sequential association with Hsp70 and Hsp90 as well as phosphorylation. We also present evidence for a two-phase activation of MAP kinase in Xenopus oocytes.

Keywords: Hsp90/MAP kinase/maturation/Mos/Xenopus oocyte

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