Multiple mechanisms control phosphorylation of PHAS-I in five (S/T)P sites that govern translational repression
Multiple mechanisms control phosphorylation of PHAS-I in five (S/T)P sites that govern translational repression
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DOI：
10.1128/mcb.20.10.3558-3567.2000
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发表时间：
2000-05-01
影响因子：
5.3
通讯作者：
Lawrence, JC
中科院分区：
文献类型：
--
作者：
Mothe-Satney, I;Yang, DQ;Lawrence, JC
通过表达在5个（S/T）P磷酸化位点中具有Ser/Thr-> Ala突变的蛋白质来研究翻译阻遏物PHAS-I的控制。HEK293细胞的实验结果显示了至少三个水平的对照。在一个极端是不受调节的磷酸化，例如Ser82的组成性磷酸化。在中间水平，氨基酸和胰岛素通过mTOR依赖性过程刺激Thr36、Thr45和Thr69的磷酸化，所述mTOR依赖性过程独立于PHAS-I中的其他位点发挥作用。在第三个水平，一个位点的磷酸化程度调节另一个位点的磷酸化。这种控制由Ser64磷酸化表示，其依赖于所有三个TP位点的磷酸化。这5个位点对PHAS-I的电泳特性和PHAS-I对真核起始因子4E（eIF4E）的亲和力有不同的影响。Thr45或Ser64的磷酸化导致体外eIF4E结合的最显著降低。然而，每个位点都直接通过调节PHAS-I和eIF4E的结合亲和力或间接通过影响其他位点的磷酸化来影响mRNA翻译。
Control of the translational repressor, PHAS-I, was investigated by expressing proteins with Ser/Thr--> Ala mutations in the five (S/T)P phosphorylation sites. Results of experiments with HEK293 cells reveal at least three levels of control. At one extreme is nonregulated phosphorylation, exemplified by constitutive phosphorylation of Ser82. At an intermediate level, amino acids and insulin stimulate the phosphorylation of Thr36, Thr45, and Thr69 via mTOR-dependent processes that function independently of other sites in PHAS-I. At the third level, the extent of phosphorylation of one site modulates the phosphorylation of another. This control is represented by Ser64 phosphorylation, which depends on the phosphorylation of all three TP sites. The five sites have different influences on the electrophoretic properties of PHAS-I and on the affinity of PHAS-I for eukaryotic initiation factor 4E (eIF4E). Phosphorylation of Thr45 or Ser64 results in the most dramatic decreases in eIF4E binding in vitro. However, each of the sites influences mRNA translation, either directly by modulating the binding affinity of PHAS-I and eIF4E or indirectly by affecting the phosphorylation of other sites.