Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Cell Cycle. 2013 Mar 15;12(6):953-60. doi: 10.4161/cc.23945. Epub 2013 Feb 26.
The synthesis and degradation of hBora is important for the regulation of mitotic entry and exist. In G 2 phase, hBora can complex with Aurora A to activate Plk1 and control mitotic entry. However, whether the post-translational modification of hBora is relevant to the mitotic entry still unclear. Here, we used the LC-MS/MS phosphopeptide mapping assay to identify 13 in vivo hBora phosphorylation sites and characterized that GSK3β can interact with hBora and phosphorylate hBora at Ser274 and Ser278. Pharmacological inhibitors of GSK3β reduced the retarded migrating band of hBora in cells and diminished the phosphorylation of hBora by in vitro kinase assay. Moreover, as well as in GSK3β activity-inhibited cells, specific knockdown of GSK3β by shRNA and S274A/S278 hBora mutant-expressing cells also exhibited the reduced Plk1 activation and a delay in mitotic entry. It suggests that GSK3β activity is required for hBora-mediated mitotic entry through Ser274 and Ser278 phosphorylation.
hBora 的合成和降解对于有丝分裂的进入和存在的调节很重要。在 G2 期，hBora 可以与 Aurora A 形成复合物，激活 Plk1，从而控制有丝分裂的进入。然而，hBora 的翻译后修饰是否与有丝分裂的进入有关还不清楚。在这里，我们使用 LC-MS/MS 磷酸肽图谱分析鉴定了 13 个体内 hBora 磷酸化位点，并证实 GSK3β 可以与 hBora 相互作用，并在 Ser274 和 Ser278 位点磷酸化 hBora。GSK3β 的药理学抑制剂减少了细胞中 hBora 迁移缓慢的条带，并减少了体外激酶实验中 hBora 的磷酸化。此外，在 GSK3β 活性被抑制的细胞中，shRNA 特异性敲低 GSK3β 和表达 S274A/S278 hBora 突变体的细胞也表现出 Plk1 激活减少和有丝分裂进入延迟。这表明 GSK3β 活性是 hBora 通过 Ser274 和 Ser278 磷酸化介导有丝分裂进入所必需的。
