Roiuk Mykola, Neff Marilena, Teleman Aurelio A
German Cancer Research Center (DKFZ) Heidelberg, Heidelberg, Germany.
Faculty of Medicine, Heidelberg University, Heidelberg, Germany.
Elife. 2025 Jul 2;14:RP105311. doi: 10.7554/eLife.105311.
Translation initiation in eukaryotes requires a 40 S ribosome loaded with initiator tRNA which scans for an initiation codon. The initiator tRNA is usually recruited to the ribosome as part of a ternary complex composed of initiator tRNA, eIF2, and GTP. Although initiator tRNA recruitment was originally ascribed to another factor, eIF2A, it was later disproven and shown to occur via eIF2. Nonetheless, eIF2A is still considered a translation initiation factor because it binds the ribosome and shows genetic interactions with other initiation factors such as eIF4E. The exact function of eIF2A during translation initiation, however, remains unclear. Here, we use ribosome profiling and luciferase reporter assays to systematically test in HeLa cells the role of eIF2A in translation initiation, including translation of upstream ORFs. Since eIF2A is thought to take over the function of eIF2 when eIF2 is inhibited, we also test conditions where the integrated stress response is activated. In none of our assays, however, could we detect a role of eIF2A in translation initiation. It is possible that eIF2A plays a role in translation regulation in specific conditions that we have not tested here, or that it plays a role in a different aspect of RNA biology.
真核生物中的翻译起始需要一个装载有起始tRNA的40S核糖体，该核糖体扫描起始密码子。起始tRNA通常作为由起始tRNA、eIF2和GTP组成的三元复合物的一部分被招募到核糖体上。尽管起始tRNA的招募最初被归因于另一个因子eIF2A，但后来被证明是错误的，并且表明它是通过eIF2发生的。尽管如此，eIF2A仍被认为是一种翻译起始因子，因为它与核糖体结合，并与其他起始因子如eIF4E表现出遗传相互作用。然而，eIF2A在翻译起始过程中的具体功能仍不清楚。在这里，我们使用核糖体分析和荧光素酶报告基因检测来系统地测试HeLa细胞中eIF2A在翻译起始中的作用，包括上游开放阅读框的翻译。由于人们认为当eIF2受到抑制时，eIF2A会接管eIF2的功能，我们还测试了整合应激反应被激活的条件。然而，在我们所有的检测中，都未能检测到eIF2A在翻译起始中的作用。有可能eIF2A在我们这里未测试的特定条件下在翻译调控中发挥作用，或者它在RNA生物学的不同方面发挥作用。
