Evidence that ternary complex (eIF2-GTP-tRNAiMet)-deficient preinitiation complexes are core constituents of mammalian stress granules
Evidence that ternary complex (eIF2-GTP-tRNAiMet)-deficient preinitiation complexes are core constituents of mammalian stress granules
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DOI：
10.1091/mbc.01-05-0221
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发表时间：
2002-01-01
影响因子：
3.3
通讯作者：
Anderson, P
中科院分区：
文献类型：
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作者：
Kedersha, N;Chen, S;Anderson, P
环境应激诱导的eIF 2 α磷酸化通过减少eIF 2-GTP-tRNA（i）Met的可用性来抑制蛋白质翻译，eIF 2-GTP-tRNA（i）Met是将起始tRNA（Met）连接到43 S前起始复合物的三元复合物。产生的未翻译mRNA被动态地路由到称为应激颗粒（SG）的离散细胞质病灶，这一过程需要相关的RNA结合蛋白TIA-1和TIAR。SG似乎与多聚核糖体处于平衡状态，但这种关系的性质尚不清楚。我们现在表明，48 S前起始复合物的大多数组分（即，小而不是大的核糖体亚基eIF 3、eIF 4 E、eIF 4G）在亚砷酸盐应激的细胞中被协调地募集到SG。相反，eIF 2不是新组装的SG的组分。表达eIF 2 α的磷酸化模拟突变体（S51 D）的细胞组装具有相似组成的SG，证实这些因子的募集是翻译起始受阻的直接结果，而不是由于亚砷酸盐的其他作用。令人惊讶的是，磷酸化eIF 2 α被募集到SG中，这些SG在从亚砷酸盐诱导的应激中恢复的细胞中分解。我们讨论了这些结果的背景下，翻译检查点模型，其中TIA和eIF 2的翻译起始的功能拮抗剂，其中缺乏三元复合物驱动SG大会。
Environmental stress-induced phosphorylation of eIF2alpha inhibits protein translation by reducing the availability of eIF2-GTP-tRNA(i)Met, the ternary complex that joins initiator tRNA(Met) to the 43S preinitiation complex. The resulting untranslated mRNA is dynamically routed to discrete cytoplasmic foci known as stress granules (SGs), a process requiring the related RNA-binding proteins TIA-1 and TIAR. SGs appear to be in equilibrium with polysomes, but the nature of this relationship is obscure. We now show that most components of the 48S preinitiation complex (i.e., small, but not large, ribosomal subunits, eIF3, eIF4E, eIF4G) are coordinately recruited to SGs in arsenite-stressed cells. In contrast, eIF2 is not a component of newly assembled SGs. Cells expressing a phosphomimetic mutant (S51D) of eIF2alpha assemble SGs of similar composition, confirming that the recruitment of these factors is a direct consequence of blocked translational initiation and not due to other effects of arsenite. Surprisingly, phospho-eIF2alpha is recruited to SGs that are disassembling in cells recovering from arsenite-induced stress. We discuss these results in the context of a translational checkpoint model wherein TIA and eIF2 are functional antagonists of translational initiation, and in which lack of ternary complex drives SG assembly.