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Lookup NU author(s): Emeritus Professor Michael Whitaker
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During the early mitotic cell cycles of the sea urchin embryo, the cell oscillates between S-phase and M-phase. In the presence of aphidicolin, a DNA synthesis inhibitor, a checkpoint control blocks the activation of the p34cdc2 protein kinase, by keeping it in the inactive, tyrosine phosphorylated form, and the embryos do not enter mitosis. Caffeine has been shown to bypass the G2/M-phase checkpoint in mammalian cells and in cycling Xenopus extracts and to induce mitosis despite the presence of damaged or unreplicated DNA. In this study we show that caffeine also induces mitosis and cell division in sea urchin embryos, in the presence of unreplicated DNA, by stimulating the tyrosine dephosphorylation of p34cdc2 and switching on its protein kinase activity. We also show that the caffeine-induced activation of the p34cdc2 protein kinase is not mediated by either of the two second messengers, calcium and cAMP, or by inhibition of the p34cdc2 tyrosine kinase. Thus, none of the mechanisms proposed for caffeine's action can explain how it overrides the S-phase checkpoint in the early cell cycles of the sea urchin embryo.
Author(s): Patel R, Wright EM, Whitaker M
Publication type: Article
Publication status: Published
Journal: Zygote
Year: 1997
Volume: 5
Issue: 2
Pages: 127-138
Print publication date: 01/05/1997
ISSN (print): 0967-1994
ISSN (electronic): 1469-8730
Publisher: Cambridge University Press
URL: http://dx.doi.org/10.1017/S0967199400003804
DOI: 10.1017/S0967199400003804
PubMed id: 9276510
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