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Meiotic cell cycle in Xenopus oocytes is independent of cdk2 kinase
Author(s) -
Furuno Nobuaki,
Ogawa Yasuki,
Iwashita Jun,
Nakajo Nobushige,
Sagata Noriyuki
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/16.13.3860
Subject(s) - biology , xenopus , cyclin dependent kinase 2 , microbiology and biotechnology , meiosis , cell cycle , maturation promoting factor , genetics , kinase , protein kinase a , cell , cyclin dependent kinase 1 , gene
In vertebrates, M phase‐promoting factor (MPF), a universal G 2 /M regulator in eukaryotic cells, drives meiotic maturation of oocytes, while cytostatic factor (CSF) arrests mature oocytes at metaphase II until fertilization. Cdk2 kinase, a G 1 /S regulator in higher eukaryotic cells, is activated during meiotic maturation of Xenopus oocytes and, like Mos (an essential component of CSF), is proposed to be involved in metaphase II arrest in mature oocytes. In addition, cdk2 kinase has been shown recently to be essential for MPF activation in Xenopus embryonic mitosis. Here we report injection of Xenopus oocytes with the cdk2 kinase inhibitor p21 Cip in order to (re)evaluate the role of cdk2 kinase in oocyte meiosis. Immature oocytes injected with p21 Cip can enter both meiosis I and meiosis II normally, as evidenced by the typical fluctuations in MPF activity. Moreover, mature oocytes injected with p21 Cip are retained normally in metaphase II for a prolonged period, whereas those injected with neutralizing anti‐Mos antibody are released readily from metaphase II arrest. These results argue strongly against a role for cdk2 kinase in MPF activation and its proposed role in metaphase II arrest, in Xenopus oocyte meiosis. We discuss the possibility that cdk2 kinase stored in oocytes may function, as a maternal protein, solely for early embryonic cell cycles.