Rocaglates convert DEAD-box protein eIF4A into a sequence-selective translational repressor.
Rocaglates convert DEAD-box protein eIF4A into a sequence-selective translational repressor.
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DOI：
10.1038/nature17978
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发表时间：
2016-06-23
期刊：
影响因子：
64.8
通讯作者：
Ingolia NT
中科院分区：
文献类型：
--
作者：
Iwasaki S;Floor SN;Ingolia NT
Rocaglamide A (RocA) 是一类蛋白质合成抑制剂的典型代表，可选择性杀死非整倍体肿瘤细胞并抑制特定 mRNA 的翻译。 RocA 靶向真核起始因子 4A (eIF4A)，一种 ATP 依赖性 DEAD-box RNA 解旋酶；其 mRNA 选择性反映了强烈依赖于 eIF4A 介导的解旋的高度结构化 5'UTR。然而，rocaglate 治疗可能无法对 eIF4A 活性的丧失进行表型复制，因为这些药物实际上增加了 eIF4A 和 RNA 之间的亲和力。在这里，我们表明 5' UTR 中的二级结构只是 RocA 选择性的次要决定因素，并且 RocA 不会通过降低 eIF4A 可用性来抑制翻译。相反，在体外和细胞中，RocA 以不依赖于 ATP 的方式将 eIF4A 特异性夹在多聚嘌呤序列上。这种人为钳制的 eIF4A 会阻断 43S 扫描，导致过早的上游翻译起始，并减少带有 RocA-eIF4A 靶序列的转录本的蛋白质表达。在阐明这种主要抗癌化合物的选择性翻译抑制机制时，我们提供了药物稳定序列选择性 RNA-蛋白质相互作用的例子。
Rocaglamide A (RocA) typifies a class of protein synthesis inhibitors that selectively kill aneuploid tumor cells and repress translation of specific mRNAs. RocA targets eukaryotic initiation factor 4A (eIF4A), an ATP-dependent DEAD-box RNA helicase; its mRNA selectivity is proposed to reflect highly structured 5′ UTRs that depend strongly on eIF4A-mediated unwinding. However, rocaglate treatment may not phenocopy the loss of eIF4A activity, as these drugs actually increase the affinity between eIF4A and RNA. Here, we show that secondary structure in 5′ UTRs is only a minor determinant for RocA selectivity and RocA does not repress translation by reducing eIF4A availability. Rather, in vitro and in cells, RocA specifically clamps eIF4A onto polypurine sequences in an ATP-independent manner. This artificially clamped eIF4A blocks 43S scanning, leading to premature, upstream translation initiation and reducing protein expression from transcripts bearing the RocA-eIF4A target sequence. In elucidating the mechanism of selective translation repression by this lead anti-cancer compound, we provide an example of a drug stabilizing sequence-selective RNA-protein interactions.