eIF2B conformation and assembly state regulate the integrated stress response.
eIF2B conformation and assembly state regulate the integrated stress response.
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DOI：
10.7554/elife.65703
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发表时间：
2021-03-10
期刊：
影响因子：
7.7
通讯作者：
Walter P
中科院分区：
文献类型：
--
作者：
Schoof M;Boone M;Wang L;Lawrence R;Frost A;Walter P
整合应激反应 (ISR) 通过翻译起始因子 eIF2 的磷酸化来响应各种应激条件而激活。磷酸化 eIF2 (eIF2-P) 抑制 eIF2 的核苷酸交换因子 eIF2B，这是一种由子复合物组装而成的双重对称异十聚体。在这里，我们在体外和体内监测和操纵 eIF2B 组装。在缺乏 eIF2B 的 α 亚基的情况下，由于未组装的 eIF2B 四聚体亚复合物在细胞中积累，ISR 被诱导。添加小分子 ISR 抑制剂 ISRIB 后，eIF2B 四聚体组装成活性八聚体。令人惊讶的是，即使在完全组装的 eIF2B 十聚体的情况下，ISRIB 也会抑制 ISR，揭示了物理上相距较远的 eIF2、eIF2-P 和 ISRIB 结合位点之间的变构通信。冷冻电子显微镜结构表明 eIF2B 中的摇摆运动耦合了这些结合位点。 eIF2-P 结合将 eIF2B 十聚体转化为“联合四聚体”，底物结合和酶活性降低。由于 eIF2B 构象状态的这种变化，出现了典型的 eIF2-P 驱动的 ISR 激活。
The integrated stress response (ISR) is activated by phosphorylation of the translation initiation factor eIF2 in response to various stress conditions. Phosphorylated eIF2 (eIF2-P) inhibits eIF2’s nucleotide exchange factor eIF2B, a twofold symmetric heterodecamer assembled from subcomplexes. Here, we monitor and manipulate eIF2B assembly in vitro and in vivo. In the absence of eIF2B’s α-subunit, the ISR is induced because unassembled eIF2B tetramer subcomplexes accumulate in cells. Upon addition of the small-molecule ISR inhibitor ISRIB, eIF2B tetramers assemble into active octamers. Surprisingly, ISRIB inhibits the ISR even in the context of fully assembled eIF2B decamers, revealing allosteric communication between the physically distant eIF2, eIF2-P, and ISRIB binding sites. Cryo-electron microscopy structures suggest a rocking motion in eIF2B that couples these binding sites. eIF2-P binding converts eIF2B decamers into ‘conjoined tetramers’ with diminished substrate binding and enzymatic activity. Canonical eIF2-P-driven ISR activation thus arises due to this change in eIF2B’s conformational state.