The Mina & Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel.
Nucleic Acids Res. 2024 May 22;52(9):5356-5375. doi: 10.1093/nar/gkae119.
Stress granules (SGs) are cytoplasmic assemblies formed under various stress conditions as a consequence of translation arrest. SGs contain RNA-binding proteins, ribosomal subunits and messenger RNAs (mRNAs). It is well known that mRNAs contribute to SG formation; however, the connection between SG assembly and nuclear processes that involve mRNAs is not well established. Here, we examine the effects of inhibiting mRNA transcription, splicing and export on the assembly of SGs and the related cytoplasmic P body (PB). We demonstrate that inhibition of mRNA transcription, splicing and export reduces the formation of canonical SGs in a eukaryotic initiation factor 2α phosphorylation-independent manner, and alters PB size and quantity. We find that the splicing inhibitor madrasin promotes the assembly of stress-like granules. We show that the addition of synthetic mRNAs directly to the cytoplasm is sufficient for SG assembly, and that the assembly of these SGs requires the activation of stress-associated protein synthesis pathways. Moreover, we show that adding an excess of mRNA to cells that do not have active splicing, and therefore have low levels of cytoplasmic mRNAs, promotes SG formation under stress conditions. These findings emphasize the importance of the cytoplasmic abundance of newly transcribed mRNAs in the assembly of SGs.
应激颗粒（SGs）是在各种应激条件下形成的细胞质聚集体，是翻译暂停的结果。SGs 包含 RNA 结合蛋白、核糖体亚基和信使 RNA（mRNAs）。众所周知，mRNA 有助于 SG 的形成；然而，SG 组装与涉及 mRNA 的核过程之间的联系尚未得到很好的建立。在这里，我们研究了抑制 mRNA 转录、剪接和输出对 SG 组装和相关细胞质 P 体（PB）的影响。我们证明，抑制 mRNA 转录、剪接和输出以真核起始因子 2α磷酸化非依赖性的方式减少了典型 SG 的形成，并改变了 PB 的大小和数量。我们发现剪接抑制剂 madrasin 促进应激样颗粒的组装。我们表明，将合成的 mRNAs 直接添加到细胞质中足以进行 SG 组装，并且这些 SG 的组装需要应激相关蛋白合成途径的激活。此外，我们表明，在应激条件下，向不具有活性剪接（因此细胞质中 mRNA 水平较低）的细胞中添加过量的 mRNA，可促进 SG 的形成。这些发现强调了新转录的 mRNAs 在 SG 组装中的细胞质丰度的重要性。
