Mitotic regulation of ribosomal S6 kinase 1 involves Ser/Thr, Pro phosphorylation of consensus and non-consensus sites by Cdc2
Mitotic regulation of ribosomal S6 kinase 1 involves Ser/Thr, Pro phosphorylation of consensus and non-consensus sites by Cdc2
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DOI：
10.1074/jbc.m300435200
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发表时间：
2003-05-02
影响因子：
4.8
通讯作者：
Hunter, T
中科院分区：
文献类型：
--
作者：
Shah, OJ;Ghosh, S;Hunter, T
在有丝分裂期间，细胞周期蛋白依赖性激酶 Cdc2 发出主要合成代谢过程（例如转录、mRNA 加工、翻译和核糖体生物合成）失活的信号，从而为细胞的激进且耗能的结构重组提供所需的能量。这是通过几个关键合成代谢元件的磷酸化和失活来实现的，包括 TFIIIB、TFIID、RNA 聚合酶 11、poly(A) 聚合酶和翻译延伸因子 1gamma。我们在此报告，核糖体 S6 激酶 I (S6K1) 是一种与核糖体蛋白 mRNA 翻译相关的蛋白激酶，在有丝分裂中也受到 Cdc2 的调节。在有丝分裂的 HeLa 细胞中，当 Cdc2 活性较高时，S6K1 在多个 Ser/Thr、Pro (S/TP) 位点被磷酸化，包括 Ser(371)、Ser(411)、Thr(421) 和 Ser(424)。与此同时，疏水基序位点 Thr(389) 的磷酸化减少，导致 S6K1 的比活性降低。有丝分裂 S/TP 磷酸化位点在体外很容易被 Cdc2-cyclin B 磷酸化。这些脯氨酸定向磷酸化对 Cdc2 的化学抑制剂敏感，但对雷帕霉素、磷脂酰肌醇 3-激酶、MEK1/2 或 p38 的哺乳动物靶点抑制剂不敏感。在有丝分裂停滞的小鼠 FT210 细胞中，Cdc2 的条件失活会减少 S/TP 位点上 S6K1 的磷酸化，同时增加 Thr(389) 的磷酸化。以及S6K1底物RPS6。 Cdc2 和 S6K1 之间存在物理相互作用，并且这种相互作用在有丝分裂细胞中增强。这些结果表明，Cdc2 提供了触发有丝分裂中 S6K1 失活的信号，可能是为了以牺牲核糖体蛋白质合成为代价，为昂贵的有丝分裂过程节省能量。
During mitosis, the cyclin-dependent kinase, Cdc2, signals the inactivation of major anabolic processes such as transcription, mRNA processing, translation, and ribosome biogenesis, thereby providing energy needed for the radical and energetically costly structural reorganization of the cell. This is accomplished by phosphorylation and inactivation of several key anabolic elements, including TFIIIB, TFIID, RNA polymerase 11, poly(A) polymerase, and translation elongation factor 1gamma. We report here that ribosomal S6 kinase I (S6K1), a protein kinase linked to the translation of ribosomal protein mRNAs, is also subject to regulation by Cdc2 in mitosis. In mitotic HeLa cells, when the activity of Cdc2 is high, S6K1 is phosphorylated at multiple Ser/Thr, Pro (S/TP) sites, including Ser(371), Ser(411), Thr(421), and Ser(424). Concomitant with this, the phosphorylation of the hydrophobic motif site, Thr(389), is reduced resulting in a decrease in the specific activity of S6K1. The mitotic S/TP phosphorylation sites are readily phosphorylated by Cdc2-cyclin B in vitro. These proline-directed phosphorylations are sensitive to chemical inhibitors of Cdc2 but not to inhibitors of mammalian target of rapamycin, phosphatidylinositol 3-kinase, MEK1/2, or p38. In murine FT210 cells arrested in mitosis, conditional inactivation of Cdc2 reduces phosphorylation of S6K1 at S/TP sites while simultaneously increasing phosphorylation of Thr(389). and of the S6K1 substrate, RPS6. A physical interaction exists between Cdc2 and S6K1, and this interaction is enhanced in mitotic cells. These results suggest that Cdc2 provides a signal that triggers inactivation of S6K1 in mitosis, presumably serving to spare energy for costly mitotic processes at the expense of ribosomal protein synthesis.