Baymiller Max, Helton Noah S, Dodd Benjamin, Moon Stephanie L
Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA.
Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI 48109, USA.
bioRxiv. 2025 Mar 13:2025.03.10.642431. doi: 10.1101/2025.03.10.642431.
In response to stress, translation initiation is suppressed and ribosome runoff via translation elongation drives mRNA assembly into ribonucleoprotein (RNP) granules including stress granules and P-bodies. Defects in translation elongation activate the integrated stress response. If and how stalled ribosomes are removed from mRNAs during translation elongation stress to drive RNP granule assembly is not clear. We demonstrate the integrated stress response is induced upon tRNA synthetase inhibition in part via ribosome collision sensing. However, saturating levels of tRNA synthetase inhibitors do not induce stress granules or P-bodies and prevent RNP granule assembly upon exogenous stress. The loss of tRNA synthetase activity causes persistent ribosome stalls that can be released with puromycin but are not rescued by ribosome-associated quality control pathways. Therefore, tRNA synthetase activity is required for ribosomes to run off mRNAs during stress to scaffold cytoplasmic RNP granules. Our findings suggest ribosome stalls can persist in human cells and uniquely uncouple ribonucleoprotein condensate assembly from the integrated stress response.
作为对压力的响应，翻译起始受到抑制，而通过翻译延伸的核糖体流失驱动mRNA组装成核糖核蛋白（RNP）颗粒，包括应激颗粒和P小体。翻译延伸缺陷会激活综合应激反应。在翻译延伸应激期间，停滞的核糖体如何以及是否从mRNA上移除从而驱动RNP颗粒组装尚不清楚。我们证明，在部分程度上，通过核糖体碰撞感应，tRNA合成酶抑制会诱导综合应激反应。然而，tRNA合成酶抑制剂的饱和水平不会诱导应激颗粒或P小体，并且在受到外源压力时会阻止RNP颗粒组装。tRNA合成酶活性的丧失会导致核糖体持续停滞，这种停滞可用嘌呤霉素释放，但不能通过核糖体相关的质量控制途径挽救。因此，在应激期间，核糖体从mRNA上流失以构建细胞质RNP颗粒需要tRNA合成酶活性。我们的研究结果表明，核糖体停滞可在人类细胞中持续存在，并使核糖核蛋白凝聚物组装与综合应激反应独特地解偶联。
