Translational control by TOR and TAP42 through dephosphorylation of eIF2α kinase GCN2
Translational control by TOR and TAP42 through dephosphorylation of eIF2α kinase GCN2
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DOI：
10.1101/gad.1069003
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发表时间：
2003-04-01
影响因子：
10.5
通讯作者：
Hinnebusch, AG
中科院分区：
文献类型：
--
作者：
Cherkasova, VA;Hinnebusch, AG
酵母蛋白激酶GCN2通过磷酸化eIF2α来刺激转录激活因子Gcn4的翻译，以响应氨基酸饥饿。激酶激活需要将未带电的tRNA与GCN2中的组氨酸tRNA合成酶相关结构域结合。GCN2中的丝氨酸577(Ser577)在体内被另一种激酶磷酸化，在富含介质中通过降低tRNA结合活性来抑制GCN2的功能。我们发现，在非饥饿细胞中，雷帕霉素刺激eIF2α被GCN2磷酸化，同时诱导Gcn4翻译，同时减少Ser577的磷酸化。GCN2(S577A)的丙氨酸577(Ala 577)突变减弱了雷帕霉素对eIF2α磷酸化和Gcn4翻译的影响，提示雷帕霉素激活GCN2涉及丝氨酸577去磷酸化。雷帕霉素通过抑制TOR途径调节丝氨酸577和eIF2α的磷酸化。雷帕霉素诱导的Ser 577去磷酸化、eIF2α磷酸化以及Gcn4的诱导都与TAP42有关，TAP42是2A型相关蛋白磷酸酶的调节因子。我们的结果为TOR蛋白对蛋白质合成的调控增加了一个新的维度，并证明了酵母中基因表达的营养调控的两个主要途径之间的相互作用。
Yeast protein kinase GCN2 stimulates the translation of transcriptional activator GCN4 by phosphorylating eIF2alpha in response to amino acid starvation. Kinase activation requires binding of uncharged tRNA to a histidyl tRNA synthetase-related domain in GCN2. Phosphorylation of serine 577 (Ser 577) in GCN2 by another kinase in vivo inhibits GCN2 function in rich medium by reducing tRNA binding activity. We show that rapamycin stimulates eIF2alpha phosphorylation by GCN2, with attendant induction of GCN4 translation, while reducing Ser 577 phosphorylation in nonstarved cells. The alanine 577 (Ala 577) mutation in GCN2 (S577A) dampened the effects of rapamycin on eIF2alpha phosphorylation and GCN4 translation, suggesting that GCN2 activation by rapamycin involves Ser 577 dephosphorylation. Rapamycin regulates the phosphorylation of Ser 577 and eIF2alpha by inhibiting the TOR pathway. Rapamycin-induced dephosphorylation of Ser 577, eIF2alpha phosphorylation, and induction of GCN4 all involve TAP42, a regulator of type 2A-related protein phosphatases. Our results add a new dimension to the regulation of protein synthesis by TOR proteins and demonstrate cross-talk between two major pathways for nutrient control of gene expression in yeast.