Evolutionarily conserved IMPACT impairs various stress responses that require GCN1 for activating the eIF2 kinase GCN2
Evolutionarily conserved IMPACT impairs various stress responses that require GCN1 for activating the eIF2 kinase GCN2
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DOI：
10.1016/j.bbrc.2013.12.021
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发表时间：
2014-01-10
影响因子：
3.1
通讯作者：
Castilho, Beatriz A.
中科院分区：
文献类型：
--
作者：
Cambiaghi, Tavane D.;Pereira, Catia M.;Castilho, Beatriz A.
翻译起始因子2（eIF 2 alpha）的α亚基的磷酸化对一系列环境应激的反应抑制了一般蛋白质合成，同时增加了特定mRNA的翻译，例如编码转录激活因子GCN 4和ATF 4的mRNA。eIF 2 α激酶GCN 2通过氨基酸饥饿激活，其机制涉及GCN 2与激活蛋白GCN 1结合，沿着与营养缺乏期间积累的不带电荷的tRNA结合。我们先前表明哺乳动物IMPACT及其酵母直系同源物YIH 1与GCN 1结合，从而阻止GCN 1与GCN 2结合，并在氨基酸耗尽期间刺激该eIF 2 α激酶。GCN 2活性也通过其他应激增强，包括蛋白酶体抑制、UV照射和缺乏葡萄糖。在这里，我们提供的证据表明，在哺乳动物细胞中，IMPACT直接和特异性地影响GCN 2在这些应激条件下的激活。我们发现，哺乳动物GCN 2的激活需要其与GCN 1的相互作用，IMPACT促进GCN 2-GCN 1复合物的溶解。在与YIH 1过表达相似的程度上，酵母细胞中IMPACT的过表达在所有需要GCN 2和GCN 1用于细胞存活的应激条件下抑制生长，包括暴露于乙酸、高水平的NaCl、H2 O2或苯菌灵。这项研究扩展了我们对GCN 1在各种应激安排诱导的GCN 2激活中所起作用的理解，并表明IMPACT和YIH 1使用类似的机制来调节这种eIF 2 α激酶。(C)2013 Elsevier Inc. All rights reserved.
In response to a range of environmental stresses, phosphorylation of the alpha subunit of the translation initiation factor 2 (eIF2 alpha) represses general protein synthesis coincident with increased translation of specific mRNAs, such as those encoding the transcription activators GCN4 and ATF4. The eIF2 alpha kinase GCN2 is activated by amino acid starvation by a mechanism involving GCN2 binding to an activator protein GCN1, along with association with uncharged tRNA that accumulates during nutrient deprivation. We previously showed that mammalian IMPACT and its yeast ortholog YIH1 bind to GCN1, thereby preventing GCN1 association with GCN2 and stimulation of this eIF2 alpha, kinase during amino acid depletion. GCN2 activity is also enhanced by other stresses, including proteasome inhibition, UV irradiation and lack of glucose. Here, we provide evidence that IMPACT affects directly and specifically the activation of GCN2 under these stress conditions in mammalian cells. We show that activation of mammalian GCN2 requires its interaction with GCN1 and that IMPACT promotes the dissolution of the GCN2-GCN1 complex. To a similar extent as the overexpression of YIH1, overexpression of IMPACT in yeast cells inhibited growth under all stress conditions that require GCN2 and GCN1 for cell survival, including exposure to acetic acid, high levels of NaCl, H2O2 or benomyl. This study extends our understanding of the roles played by GCN1 in GCN2 activation induced by a variety of stress arrangements and suggests that IMPACT and YIH1 use similar mechanisms for regulating this eIF2 alpha kinase. (C) 2013 Elsevier Inc. All rights reserved.