Uncoupling Stress Granule Assembly and Translation Initiation Inhibition
Uncoupling Stress Granule Assembly and Translation Initiation Inhibition
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DOI：
10.1091/mbc.e08-10-1061
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发表时间：
2009-06-01
影响因子：
3.3
通讯作者：
Mazroui, Rachid
中科院分区：
文献类型：
--
作者：
Mokas, Sophie;Mills, John R.;Mazroui, Rachid
细胞质应激颗粒（SG）是mRNA翻译的专门调控位点，在不同的应激条件下形成，已知抑制翻译起始。SG的形成通过两种途径发生：由应激介导的真核起始因子（eIF）2 α磷酸化依赖性途径和由翻译起始因子eIF 4A和eIF 4G失活介导的eIF 2 α磷酸化非依赖性途径。在这项研究中，我们研究了针对不同的翻译起始因子和步骤在HeLa细胞中SG形成的影响。通过消耗eIF 2 α，我们证明了eIF 2水平的降低。GTP Met-tRNAi（Met）三元翻译起始复合物足以诱导SGs。同样，eIF 4 B、eIF 4 H或polyA结合蛋白水平降低也会触发SG形成。相反，帽结合蛋白eIF 4 E的耗尽或阻止其组装成eIF 4F导致适度的SG形成。有趣的是，通过用2-（4-甲基-2，6-二硝基苯胺基）-N-甲基丙酰胺或通过耗尽大的核糖体亚基蛋白L28来阻断60 S核糖体的募集来干扰翻译起始的最后一步不会诱导SG组装。我们的研究确定了翻译起始步骤和参与SG形成的因素，以及那些可以靶向而不诱导SG的因素。
Cytoplasmic stress granules (SGs) are specialized regulatory sites of mRNA translation that form under different stress conditions known to inhibit translation initiation. The formation of SG occurs via two pathways; the eukaryotic initiation factor (eIF) 2 alpha phosphorylation-dependent pathway mediated by stress and the eIF2 alpha phosphorylation-independent pathway mediated by inactivation of the translation initiation factors eIF4A and eIF4G. In this study, we investigated the effects of targeting different translation initiation factors and steps in SG formation in HeLa cells. By depleting eIF2 alpha, we demonstrate that reduced levels of the eIF2. GTP. Met-tRNAi(Met) ternary translation initiation complexes is sufficient to induce SGs. Likewise, reduced levels of eIF4B, eIF4H, or polyA-binding protein, also trigger SG formation. In contrast, depletion of the cap-binding protein eIF4E or preventing its assembly into eIF4F results in modest SG formation. Intriguingly, interfering with the last step of translation initiation by blocking the recruitment of 60S ribosome either with 2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamideis or through depletion of the large ribosomal subunits protein L28 does not induce SG assembly. Our study identifies translation initiation steps and factors involved in SG formation as well as those that can be targeted without induction of SGs.