Mos stimulates MAP kinase in Xenopus oocytes and activates a MAP kinase kinase in vitro - PubMed (original) (raw)

Mos stimulates MAP kinase in Xenopus oocytes and activates a MAP kinase kinase in vitro

J Posada et al. Mol Cell Biol. 1993 Apr.

Abstract

Several protein kinases, including Mos, maturation-promoting factor (MPF), mitogen-activated protein (MAP) kinase, and MAP kinase kinase (MAPKK), are activated when Xenopus oocytes enter meiosis. De novo synthesis of the Mos protein is required for progesterone-induced meiotic maturation. Recently, bacterially synthesized maltose-binding protein (MBP)-Mos fusion protein was shown to be sufficient to initiate meiosis I and MPF activation in fully grown oocytes in the absence of protein synthesis. Here we show that MAP kinase is rapidly phosphorylated and activated following injection of wild-type, but not kinase-inactive mutant, MBP-Mos into fully grown oocytes. MAP kinase activation by MBP-Mos occurs within 20 min, much more rapidly than in progesterone-treated oocytes. The MBP-Mos fusion protein also activates MPF, but MPF activation does not occur until approximately 2 h after injection. Extracts from oocytes injected with wild-type but not kinase-inactive MBP-Mos contain an activity that can phosphorylate MAP kinase, suggesting that Mos directly or indirectly activates a MAPKK. Furthermore, activated MBP-Mos fusion protein is able to phosphorylate and activate a purified, phosphatase-treated, rabbit muscle MAPKK in vitro. Thus, in oocytes, Mos is an upstream activator of MAP kinase which may function through direct phosphorylation of MAPKK.

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References

    1. Cell. 1985 Dec;43(3 Pt 2):615-21 - PubMed
    1. Curr Opin Cell Biol. 1992 Dec;4(6):992-9 - PubMed
    1. Cell. 1988 Jul 1;54(1):17-26 - PubMed
    1. Cell. 1988 Jul 29;54(3):423-31 - PubMed
    1. Cell. 1988 Jul 29;54(3):433-9 - PubMed

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