Heat shock response (HSR) is an ancient signaling pathway leading to thermoprotection of nearly all living organisms. Emerging evidence suggests that intracellular O-linked β-N-acetylglucosamine (O-GlcNAc) serves as a molecular ‘thermometer’ by reporting ambient temperature fluctuations. Whether and how O-GlcNAc modification regulates HSR remains unclear. Here we report that, upon heat shock stress, the key translation initiation factor eIF4GI undergoes dynamic O-GlcNAcylation at the N-terminal region. Without O-GlcNAc modification, the preferential translation of stress mRNAs is impaired. Unexpectedly, stress mRNAs are entrapped within stress granules (SGs) that are no longer dissolved during stress recovery. Mechanistically, we show that stress-induced eIF4GI O-GlcNAcylation repels poly(A)-binding protein 1 and promotes SG disassembly, thereby licensing stress mRNAs for selective translation. Using various eIF4GI mutants created by CRISPR/Cas9, we demonstrate that eIF4GI acts as a translational switch via reversible O-GlcNAcylation. Our study reveals a central mechanism linking heat stress sensing, protein remodeling, SG dynamics and translational reprogramming.

热休克反应（HSR）是古老的信号传导途径，几乎可以保护所有活生物体。新兴证据表明，细胞内O-连接的β- N-乙酰氨基葡萄糖（O- GlcNAc）通过报告环境温度波动而充当分子“温度计”。O- GlcNAc修饰是否以及如何调节HSR仍不清楚。在这里，我们报告说，在热激应力下，关键翻译起始因子eIF4GI在N端区域经历了动态O -GlcNAcylation。没有O-GlcNAc修饰，应力mRNA的优先翻译受到损害。出乎意料的是，应力mRNA被困在应力颗粒（SGs​​）中，而这些颗粒在应力恢复过程中不再溶解。从机理上讲，我们表明应激诱导的eIF4GI O -GlcNAcylation排斥poly（A）结合蛋白1并促进SG拆卸，从而许可应激mRNA用于选择性翻译。使用由CRISPR / Cas9创建的各种eIF4GI突变体，我们证明eIF4GI通过可逆的O -GlcNAcylation充当翻译开关。我们的研究揭示了连接热应激感测，蛋白质重塑，SG动力学和翻译重编程的中心机制。