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MAP kinase links the fertilization signal transduction pathway to the G 1 /S‐phase transition in starfish eggs
Author(s) -
Tachibana Kazunori,
Machida Takumitsu,
Nomura Yoriko,
Kishimoto Takeo
Publication year - 1997
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/16.14.4333
Subject(s) - biology , cyclin dependent kinase 1 , mitogen activated protein kinase kinase , cyclin dependent kinase 2 , maturation promoting factor , microbiology and biotechnology , map kinase kinase kinase , human fertilization , kinase , cyclin dependent kinase 9 , ask1 , protein kinase a , mapk14 , map2k7 , biochemistry , cell cycle , genetics , cell
The mechanism by which fertilization initiates S‐phase in the zygote is examined by manipulating the activity of MAP kinase in mature starfish eggs. These unfertilized eggs, which are arrested at G 1 ‐phase after the completion of meiosis, have high MAP kinase activity but undetectable cdc2 kinase activity. Either fertilization or inhibition of protein synthesis causes a decrease in MAP kinase activity, which is followed by DNA synthesis. Inactivation of MAP kinase with its specific phosphatase, CL100, initiates DNA synthesis in the absence of fertilization, while constitutive activation of MAP kinase with MEK represses the initiation of DNA synthesis following fertilization. Thus, in unfertilized mature starfish eggs, a capacity for DNA replication is already acquired, but entry into S‐phase is negatively regulated by MAP kinase activity that is supported by a continuously synthesized protein(s) but not by cdc2 kinase. Upon fertilization, downregulation of MAP kinase activity is necessary and sufficient for triggering the G 1 /S‐phase transition.