Small ribosomal protein RPS0 stimulates translation initiation by mediating 40S-binding of eIF3 via its direct contact with the eIF3a/TIF32 subunit.
Small ribosomal protein RPS0 stimulates translation initiation by mediating 40S-binding of eIF3 via its direct contact with the eIF3a/TIF32 subunit.
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DOI：
10.1371/journal.pone.0040464
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Valášek LS
中科院分区：
文献类型：
--
作者：
Kouba T;Dányi I;Gunišová S;Munzarová V;Vlčková V;Cuchalová L;Neueder A;Milkereit P;Valášek LS
核糖体将mRNA编码的信息翻译成所有活细胞中的蛋白质。在真核生物中，它的小亚基与许多真核起始因子（eIFs）一起负责定位mRNA的翻译起点，以正确解码其携带的遗传信息。这个多步骤的过程需要及时和空间协调的eIFs在核糖体表面上的位置。在我们长期的追求映射的40 S结合位点的功能最复杂的eIFs，酵母多亚基eIF 3，我们确定了几个相互作用，将其主体的头部，喙和肩部区域的溶剂暴露侧的40 S亚基。其中之一是eIF 3的a/TIF 32亚基的N-末端结构域（NTD）与位于mRNA出口通道附近的小核糖体蛋白RPS 0A之间的相互作用。之前，我们证明了tif 32-Δ8中200个残基的N端截短显著降低了eIF 3和其他eIFs与体内40 S核糖体的结合，并严重损害了eIF 3确保的翻译重新启动。在这里，我们表明，不是第一个，但接下来的200个残基的a/TIF 32特异性相互作用与RPS 0A通过其极端的C-末端尾（CTT）。RPS 0A条件性耗竭突变体的详细分析揭示了多核糖体与单核糖体比率的显著下降，表明在非允许条件下生长的细胞的起始速率显著受损。事实上，发现在RPS 0A耗尽的细胞中与前起始复合物中的40 S亚基相关的eIF 3和其他eIF的量减少;一致地，与tif 32-Δ8细胞中的程度相似。用RPS 0A的活的CTT较少的突变体也观察到类似但不太明显的效果。总之，我们得出结论，柔性RPS 0A-CTT和a/TIF 32-NTD的残基200-400之间的相互作用显著刺激eIF 3及其相关eIF在体内与小核糖体亚基的附着。
The ribosome translates information encoded by mRNAs into proteins in all living cells. In eukaryotes, its small subunit together with a number of eukaryotic initiation factors (eIFs) is responsible for locating the mRNA's translational start to properly decode the genetic message that it carries. This multistep process requires timely and spatially coordinated placement of eIFs on the ribosomal surface. In our long-standing pursuit to map the 40S-binding site of one of the functionally most complex eIFs, yeast multisubunit eIF3, we identified several interactions that placed its major body to the head, beak and shoulder regions of the solvent-exposed side of the 40S subunit. Among them is the interaction between the N-terminal domain (NTD) of the a/TIF32 subunit of eIF3 and the small ribosomal protein RPS0A, residing near the mRNA exit channel. Previously, we demonstrated that the N-terminal truncation of 200 residues in tif32-Δ8 significantly reduced association of eIF3 and other eIFs with 40S ribosomes in vivo and severely impaired translation reinitiation that eIF3 ensures. Here we show that not the first but the next 200 residues of a/TIF32 specifically interact with RPS0A via its extreme C-terminal tail (CTT). Detailed analysis of the RPS0A conditional depletion mutant revealed a marked drop in the polysome to monosome ratio suggesting that the initiation rates of cells grown under non-permissive conditions were significantly impaired. Indeed, amounts of eIF3 and other eIFs associated with 40S subunits in the pre-initiation complexes in the RPS0A-depleted cells were found reduced; consistently, to the similar extent as in the tif32-Δ8 cells. Similar but less pronounced effects were also observed with the viable CTT-less mutant of RPS0A. Together we conclude that the interaction between the flexible RPS0A-CTT and the residues 200–400 of the a/TIF32-NTD significantly stimulates attachment of eIF3 and its associated eIFs to small ribosomal subunits in vivo.
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