| 摘要 |
Entry into mitosis requires the activity of the Cdc25C phosphatase which functions to activate Cdc2/Cyclin B. In asynchronously growing cells, Cdc25C is stoichiometrically phosphorylated on serine 216. Levels of serine 216 phosphorylation remain constant throughout the G1-, S- and G2-phases of the cell cycle. A human kinase, denoted TcAK1 (for Twenty-five C Associated protein Kinase) that phosphorylates Cdc25C on serine 216 has been cloned and sequenced (see the figure). A method is also provided for measuring levels of TcAK1 in RNA or of TcAK1 protein in cells. Phosphorylation of Cdc25C on serine 216 with TcAK1 creates a 14-3-3 recognition motif. The interaction between Cdc25C and 14-3-3 proceeds in a phosphorylation-specific manner. TcAK1 functions to mediate interaction between 14-3-3 proteins and other cellular proteins associated with oncogenesis of key signalling events.
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