Phosphorylation of Xenopus Cdc25C at Ser285 Interferes with Ability to Activate a DNA Damage Replication Checkpoint in Pre-Midblastula Embryos
Phosphorylation of Xenopus Cdc25C at Ser285 Interferes with Ability to Activate a DNA Damage Replication Checkpoint in Pre-Midblastula Embryos
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DOI：
10.4161/cc.2.3.396
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发表时间：
2003-01-01
期刊：
影响因子：
4.3
通讯作者：
Fornace, Albert J., Jr.
中科院分区：
文献类型：
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作者：
Bulavin, Dmitry V.;Demidenko, Zoya N.;Fornace, Albert J., Jr.
我们最近已经证明，通过在其14-3-3位点磷酸化的人Cdc 25蛋白磷酸酶的负调节可以通过在-2位置的相邻位点的磷酸化来拮抗。1基于不同Cdc 25磷酸酶的结构同源性，在非洲爪蟾胚胎中也可以保存类似的调控途径，其中细胞周期检查点在中囊胚转换（MBT）之前不起作用。在这里，我们证明，MBT之前，XeCdc 25 C是磷酸化的Ser 285，一个类似的网站Ser 214在人类Cdc 25 C或Ser 307在Cdc 25 B。(1)Ser 285的磷酸化阻止了随后XeCdc 25 C在Ser 287上的抑制性磷酸化，从而使XeCdc 25 C保持活性形式。Ser 285突变为丙氨酸允许DNA损伤复制检查点的重建。这种作用完全依赖于Ser 287磷酸化，因为Ser 287突变为丙氨酸完全逆转了Ser 285 A XeCdc 25 C的细胞周期抑制作用。我们建议，XeCdc 25 C Ser 285的磷酸化可能是导致在MBT之前切割非洲爪蟾胚胎时缺乏DNA复制检查点的原因。
We have recently demonstrated that negative regulation of human Cdc25 protein phosphatases by phosphorylation at their 14-3-3 site can be antagonized through phosphorylation at an adjacent site in the -2 position. 1 Based on structural homology for different Cdc25 phosphatases, a similar regulatory pathway also could be conserved in Xenopus embryos, where cell cycle checkpoints are not operational prior to the Midblastula Transition (MBT). Here, we demonstrate that before MBT, XeCdc25C is phosphorylated on Ser285, an analogous site to Ser214 in human Cdc25C or Ser307 in Cdc25B.(1) Phosphorylation of Ser285 prevents subsequent inhibitory phosphorylation of XeCdc25C on Ser287, thus maintaining XeCdc25C in an active form. Mutation of Ser285 to alanine allows the reconstitution of a DNA damage replication checkpoint. This effect is completely dependent on Ser287 phosphorylation as additional mutation of Ser287 to alanine fully reversed the cell cycle inhibitory effect of Ser285A XeCdc25C. We propose that phosphorylation of XeCdc25C Ser285 may account for the lack of a DNA replication checkpoint in cleaving Xenopus embryos prior to the MBT.