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Calcium requirements during mitotic cdc2 kinase activation and cyclin degradation in Xenopus egg extracts.

Lindsay, Howard D. and Whitaker, Michael J. and Ford, Christopher C. (1995) Calcium requirements during mitotic cdc2 kinase activation and cyclin degradation in Xenopus egg extracts. Journal of Cell Science, 108 (11). pp. 3557-3568. ISSN 0021-9533

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    Abstract

    Activation of p34cdc2 kinase is essential for entry into mitosis while subsequent deactivation and cyclin degradation are associated with exit. In Xenopus embryos, both of these phases are regulated by post-translational modifications and occur spontaneously on incubation of extracts prepared late in the first cell cycle. Even though high levels of calcium buffer were initially used to prepare these extracts, we found that free calcium levels in them remained in the observed physiological range (200-500nM). Further addition of calcium buffers only slightly reduced free calcium levels, but inhibited histone H1 (cdc2) kinase deactivation and cyclin degradation. Higher buffer concentrations slowed the kinase activation phase. Reducing the free buffer concentration by premixing with calcium reversed the effects of the buffer, indicating that the inhibitory effects arose from the calcium-chelating properties of the buffer rather than non-specific side effects. Furthermore, additions of calcium buffer at the end of the H1 kinase activation phase did not prevent deactivation. From these results, and the order of effectiveness of different calcium buffers in disrupting the H1 kinase cycle, we suggest that local transient increases in free calcium influence the rate of cdc2 kinase activation and are required to initiate the pathway leading to cyclin degradation and kinase inactivation in mitotic cell cycles.

    Item Type: Article
    Journal or Publication Title: Journal of Cell Science
    Uncontrolled Keywords: BAPTA ; calcium ; cell division cycle ; cyclin ; CaM kinase
    Subjects: Q Science > QH Natural history > QH301 Biology
    Departments: Faculty of Health and Medicine > Medicine
    ID Code: 28090
    Deposited By: Dr Howard Lindsay
    Deposited On: 09 Nov 2009 09:50
    Refereed?: Yes
    Published?: Published
    Last Modified: 26 Jul 2012 16:44
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/28090

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