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Targets of the cyclin-dependent kinase Cdk1


The events of cell reproduction are governed by oscillations in the activities of cyclin-dependent kinases (Cdks)1. Cdks control the cell cycle by catalysing the transfer of phosphate from ATP to specific protein substrates. Despite their importance in cell-cycle control, few Cdk substrates have been identified2. Here, we screened a budding yeast proteomic library for proteins that are directly phosphorylated by Cdk1 in whole-cell extracts. We identified about 200 Cdk1 substrates, several of which are phosphorylated in vivo in a Cdk1-dependent manner. The identities of these substrates reveal that Cdk1 employs a global regulatory strategy involving phosphorylation of other regulatory molecules as well as phosphorylation of the molecular machines that drive cell-cycle events. Detailed analysis of these substrates is likely to yield important insights into cell-cycle regulation.

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Figure 1: Addition of Cdk1-as1 and radiolabelled N6-(benzyl) ATP to a cell extract results in the appearance of many specific phosphoproteins.
Figure 2: 181 proteins are efficiently phosphorylated by Cdk1-as1·Clb2.
Figure 3: Validation of yeast Cdk1 substrates in vivo.


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We thank E. Phizicky for the GST-ORF library; the many laboratories at UCSF who helped duplicate and distribute the GST-ORF library; E. K. O'Shea and J. S. Weissman for TAP-tagged strains; D. Kellogg for sharing unpublished results; E. K. O'Shea and R. Deshaies for expression plasmids; N. Dephoure and M. Verzi for strain construction; S. Biggins, D. Kellogg, A. Goga, S. Steggerda, C. Carroll, D. Randle, M. Enquist-Newman and M. Loog for advice and critical reading of the manuscript. This work was supported by funding from the National Institute of General Medical Sciences (D.O.M.), the National Institutes of Health (K.M.S.), and by a predoctoral fellowship from the National Science Foundation (J.A.U.).

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Correspondence to David O. Morgan.

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Ubersax, J., Woodbury, E., Quang, P. et al. Targets of the cyclin-dependent kinase Cdk1. Nature 425, 859–864 (2003).

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