Activation of Cdc25C

PLK1 phosphorylates CDC25C on serine residue S198. In addition to catalytically activating CDC25C, PLK1-mediated phosphorylation also results in the nuclear accumulation of CDC25C (Toyoshima-Morimoto et al. 2002). It has been shown that Xenopus polo homolog, Plx1, directly phosphorylates and activates Cdc25C, which in turn dephosphorylates and activates Cdc2. This step is critical for the onset of mitosis. Since Plx1-dependent Cdc25C phosphorylation occurs in the absence of Cdc2 activity, it is likely that Plx1 is a triggering kinase, which leads to the activation of Cdc2 and therefore the normal onset of mitosis (Kumagai and Dunphy 1996).

PLK1于丝氨酸残基S198处对CDC25C进行磷酸化。除了催化激活CDC25C外，PLK1介导的磷酸化还导致CDC25C在核内积累（Toyoshima-Morimoto等，2002年）。研究表明，非洲爪蟾的多洛同源物Plx1直接磷酸化和激活Cdc25C，而Cdc25C进而去磷酸化和激活Cdc2。此步骤对于有丝分裂的开始至关重要。鉴于Plx1依赖的Cdc25C磷酸化在没有Cdc2活性的情况下发生，Plx1很可能是一个触发激酶，它引发Cdc2的激活，从而促进有丝分裂的正常开始（Kumagai和Dunphy，1996年）。