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Mitogen‐activated protein kinase (MAP kinase) activation in Xenopus oocytes: Roles of MPF and protein synthesis
Author(s) -
Haccard Olivier,
Jessus Catherine,
Rime Helene,
Goris Jozef,
Merlevede Wilfried,
Ozon Rene
Publication year - 1993
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.1080360114
Subject(s) - map kinase kinase kinase , mitogen activated protein kinase kinase , ask1 , biology , map2k7 , cyclin dependent kinase 9 , cyclin dependent kinase 2 , mapk14 , microbiology and biotechnology , c raf , mitogen activated protein kinase , protein kinase a , cyclin dependent kinase 1 , kinase , biochemistry , cell cycle , cell
Mitogen‐activated protein kinase (MAP kinase) is a serine/threonine kinase whose enzymatic activity is thought to play a crucial role in mitogenic signal transduction and also in the progesterone‐induced meiotic maturation of Xenopus oocytes. We have purified MAP kinase from Xenopus oocytes and have shown that the protein is present in metaphase ll oocytes under two different forms: an inactive 41‐kD protein able to autoactivate and to autophosphorylate in vitro, and an active 42‐kD kinase resolved into two tyrosine phosphorylated isoforms on 2D gels. During meiotic maturation, MAP kinase becomes tyrosine phosphorylated and activated following the activation of the M‐phase promoting factor (MPF), a complex between the p34 cdc2 kinase and cyclin B. In vivo, MAP kinase activity displays a different stability in metaphase l and in metaphase II: protein synthesis is required to maintain MAP kinase activity in metaphase I but not in metaphase II oocytes. Injection of either MPF or cyclin B into prophase oocytes promotes tyrosine phosphorylation of MAP kinase, indicating that its activation is a downstream event of MPF activation. In contrast, injection of okadaic acid, which induces in vivo MPF activation, promotes only a very weak tyrosine phosphorylation of MAP kinase, suggesting that effectors other than MPF are required for the MAP kinase activation. Moreover, in the absence of protein synthesis, cyclin B and MPF are unable to promote in vivo activation of MAP kinase, indicating that this activation requires the synthesis of new protein(s). © 1993 Wiley‐Liss, Inc.