Chair of Biochemistry III, Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany.
PLoS One. 2023 Mar 30;18(3):e0283698. doi: 10.1371/journal.pone.0283698. eCollection 2023.
RpS0/uS2, rpS2/uS5, and rpS21/eS21 form a cluster of ribosomal proteins (S0-cluster) at the head-body junction near the central pseudoknot of eukaryotic small ribosomal subunits (SSU). Previous work in yeast indicated that S0-cluster assembly is required for the stabilisation and maturation of SSU precursors at specific post-nucleolar stages. Here, we analysed the role of S0-cluster formation for rRNA folding. Structures of SSU precursors isolated from yeast S0-cluster expression mutants or control strains were analysed by cryogenic electron microscopy. The obtained resolution was sufficient to detect individual 2'-O-methyl RNA modifications using an unbiased scoring approach. The data show how S0-cluster formation enables the initial recruitment of the pre-rRNA processing factor Nob1 in yeast. Furthermore, they reveal hierarchical effects on the pre-rRNA folding pathway, including the final maturation of the central pseudoknot. Based on these structural insights we discuss how formation of the S0-cluster determines at this early cytoplasmic assembly checkpoint if SSU precursors further mature or are degraded.
RpS0/uS2、rpS2/uS5 和 rpS21/eS21 在真核小核糖体亚基（SSU）中央假结附近的头-体连接处形成核糖体蛋白（S0 簇）。先前在酵母中的研究表明，S0 簇的组装对于特定核仁后阶段 SSU 前体的稳定和成熟是必需的。在这里，我们分析了 S0 簇形成对 rRNA 折叠的作用。通过低温电子显微镜分析了从酵母 S0 簇表达突变体或对照菌株中分离的 SSU 前体的结构。获得的分辨率足以使用无偏评分方法检测单个 2'-O-甲基 RNA 修饰。这些数据展示了 S0 簇的形成如何使 pre-rRNA 加工因子 Nob1 在酵母中的初始招募成为可能。此外，它们还揭示了对 pre-rRNA 折叠途径的分层影响，包括中央假结的最终成熟。基于这些结构上的见解，我们讨论了 S0 簇的形成如何在这个早期的细胞质组装检查点决定 SSU 前体是否进一步成熟或被降解。
