Institute of Microbiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic.
First Faculty of Medicine, Charles University, Katerinska 42, 12108 Prague, Czech Republic.
Int J Mol Sci. 2021 May 13;22(10):5164. doi: 10.3390/ijms22105164.
Stress granules (SGs) are membrane-less assemblies arising upon various stresses in eukaryotic cells. They sequester mRNAs and proteins from stressful conditions and modulate gene expression to enable cells to resume translation and growth after stress relief. SGs containing the translation initiation factor eIF3a/Rpg1 arise in yeast cells upon robust heat shock (HS) at 46 °C only. We demonstrate that the destabilization of Rpg1 within the PCI domain in the Rpg1-3 variant leads to SGs assembly already at moderate HS at 42 °C. These are bona fide SGs arising upon translation arrest containing mRNAs, which are components of the translation machinery, and associating with P-bodies. HS SGs associate with endoplasmatic reticulum and mitochondria and their contact sites ERMES. Although Rpg1-3-labeled SGs arise at a lower temperature, their disassembly is delayed after HS at 46 °C. Remarkably, the delayed disassembly of HS SGs after the robust HS is reversed by TDP-43, which is a human protein connected with amyotrophic lateral sclerosis. TDP-43 colocalizes with HS SGs in yeast cells and facilitates cell regrowth after the stress relief. Based on our results, we propose yeast HS SGs labeled by Rpg1 and its variants as a novel model system to study functions of TDP-43 in stress granules disassembly.
应激颗粒（SGs）是真核细胞在各种应激条件下形成的无膜结构。它们将 mRNA 和蛋白质从应激条件下隔离出来，并调节基因表达，以使细胞在应激缓解后能够恢复翻译和生长。只有在 46°C 的强烈热激（HS）下，酵母细胞中才会出现含有翻译起始因子 eIF3a/Rpg1 的 SGs。我们证明，在 Rpg1-3 变体中 PCI 结构域内的 Rpg1 不稳定会导致在温和的 42°C HS 下就开始组装 SGs。这些是真正的 SGs，在翻译受阻时形成，包含 mRNA，它们是翻译机制的组成部分，并与 P 体结合。HS SGs 与内质网和线粒体及其接触部位 ERMES 相关联。虽然 Rpg1-3 标记的 SGs 在较低温度下形成，但它们在 46°C 的强烈 HS 后解体的延迟。值得注意的是，强烈 HS 后 HS SGs 的延迟解体被 TDP-43 逆转，TDP-43 是一种与肌萎缩性侧索硬化症相关的人类蛋白。TDP-43 在酵母细胞中与 HS SGs 共定位，并促进应激缓解后的细胞再生。基于我们的结果，我们提出用 Rpg1 及其变体标记的酵母 HS SGs 作为研究 TDP-43 在 SGs 解体中的功能的新型模型系统。
