Center for Gene Regulation in Health and Disease, Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH 44115, USA.
Nucleic Acids Res. 2019 Jan 25;47(2):806-823. doi: 10.1093/nar/gky1180.
The small ribosomal subunit protein uS9 (formerly called rpS16 in Saccharomyces cerevisiae), has a long protruding C-terminal tail (CTT) that extends towards the mRNA cleft of the ribosome. The last C-terminal residue of uS9 is an invariably conserved, positively charged Arg that is believed to enhance interaction of the negatively charged initiator tRNA with the ribosome when the tRNA is base-paired to the AUG codon in the P-site. In order to more fully characterize the role of the uS9 CTT in eukaryotic translation, we tested how truncations, extensions and substitutions within the CTT affect initiation and elongation processes in Saccharomyces cerevisiae. We found that uS9 C-terminal residues are critical for efficient recruitment of the eIF2•GTP•Met-tRNAiMet ternary complex to the ribosome and for its proper response to the presence of an AUG codon in the P-site during the scanning phase of initiation. These residues also regulate hydrolysis of the GTP in the eIF2•GTP•Met-tRNAiMet complex to GDP and Pi. In addition, our data show that uS9 CTT modulates elongation fidelity. Therefore, we propose that uS9 CTT is critical for proper control of the complex interplay of events surrounding accommodation of initiator and elongator tRNAs in the P- and A-sites of the ribosome.
小核糖体亚单位蛋白 uS9（在酿酒酵母中以前称为 rpS16），具有一个长的突出的 C 末端尾巴（CTT），伸向核糖体的 mRNA 裂隙。uS9 的最后一个 C 末端残基是一个不变的保守的、带正电荷的精氨酸，据信当 tRNA 与 P 位上的 AUG 密码子碱基配对时，该精氨酸增强了带负电荷的起始 tRNA 与核糖体的相互作用。为了更全面地描述 uS9 CTT 在真核翻译中的作用，我们测试了 CTT 内的截断、延伸和取代如何影响酿酒酵母中的起始和延伸过程。我们发现，uS9 C 末端残基对于有效地招募 eIF2•GTP•Met-tRNAiMet 三元复合物到核糖体以及对于其在起始扫描阶段正确响应 P 位上 AUG 密码子是至关重要的。这些残基还调节 eIF2•GTP•Met-tRNAiMet 复合物中 GTP 的水解为 GDP 和 Pi。此外，我们的数据表明，uS9 CTT 调节延伸保真度。因此，我们提出 uS9 CTT 对于适当控制围绕起始和延伸 tRNA 在核糖体的 P 和 A 位上的容纳的事件的复杂相互作用是至关重要的。
