Department of Integrated Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch Cedex, France.
Université de Strasbourg, Illkirch Cedex, France.
Science. 2024 Nov 29;386(6725):eado8476. doi: 10.1126/science.ado8476.
Protein synthesis begins with the formation of a ribosome-messenger RNA (mRNA) complex. In bacteria, the small ribosomal subunit (30) is recruited to many mRNAs through base pairing with the Shine-Dalgarno (SD) sequence and RNA binding by ribosomal protein bS1. Translation can initiate on nascent mRNAs, and RNA polymerase (RNAP) can promote the recruitment of the pioneering 30. Here, we examined 30 recruitment to nascent mRNAs using cryo-electron microscopy, single-molecule fluorescence colocalization, and in-cell cross-linking mass spectrometry. We show that bS1 delivers the mRNA to the ribosome for SD duplex formation and 30 activation. Additionally, bS1 and RNAP stimulate translation initiation. Our work provides a mechanistic framework for how the SD duplex, ribosomal proteins, and RNAP cooperate in 30 recruitment to mRNAs and establish transcription-translation coupling.
蛋白质合成始于核糖体-信使 RNA（mRNA）复合物的形成。在细菌中，小核糖体亚基（30）通过与 Shine-Dalgarno（SD）序列碱基配对以及与核糖体蛋白 bS1 的 RNA 结合，被招募到许多 mRNA 上。新生 mRNA 上可以起始翻译，RNA 聚合酶（RNAP）可以促进先驱 30 的招募。在这里，我们使用冷冻电子显微镜、单分子荧光共定位和细胞内交联质谱法研究了新生 mRNA 上的 30 招募情况。我们表明，bS1 将 mRNA 递送至核糖体以形成 SD 双链体并激活 30。此外，bS1 和 RNAP 还刺激翻译起始。我们的工作为 SD 双链体、核糖体蛋白和 RNAP 如何协同作用将 30 招募到 mRNA 并建立转录-翻译偶联提供了一个机制框架。
