ABSTRACT

Protein synthesis rate and accuracy are tightly controlled by the cell and are essential for proteome homoeostasis (proteostasis); however, the full picture of how mRNA translational factors maintain protein synthesis accuracy and co-translational protein folding are far from being fully understood. To address this question, we evaluated the role of 70 yeast tRNA-modifying enzyme genes on protein aggregation and used mass spectrometry to identify the aggregated proteins. We show that modification of uridine at anticodon position 34 (U34) by the tRNA-modifying enzymes Elp1, Elp3, Sml3 and Trm9 is critical for proteostasis, the mitochondrial tRNA-modifying enzyme Slm3 plays a fundamental role in general proteostasis and that stress response proteins whose genes are enriched in codons decoded by tRNAs lacking mcm⁵U₃₄, mcm⁵s²U₃₄, ncm⁵U₃₄, ncm⁵Um₃₄, modifications are overrepresented in protein aggregates of the ELP1, SLM3 and TRM9 KO strains. Increased rates of amino acid misincorporation were also detected in these strains at protein sites that specifically mapped to the codons sites that are decoded by the hypomodified tRNAs, demonstrating that U₃₄ tRNA modifications safeguard the proteome from translational errors, protein misfolding and proteotoxic stress.

 抽象的

蛋白质合成速率和准确性受到细胞严格控制，对于蛋白质组稳态（蛋白质稳态）至关重要；然而，mRNA 翻译因子如何维持蛋白质合成准确性和共翻译蛋白质折叠的全貌还远未完全了解。为了解决这个问题，我们评估了 70 个酵母 tRNA 修饰酶基因对蛋白质聚集的作用，并使用质谱法来鉴定聚集的蛋白质。我们发现，tRNA 修饰酶 Elp1、Elp3、Sml3 和 Trm9 对反密码子 34 位 (U34) 处尿苷的修饰对于蛋白质稳态至关重要，线粒体 tRNA 修饰酶 Slm3 在一般蛋白质稳态中发挥着基础作用，并且应激反应蛋白其基因富含由缺乏 mcm ⁵ U ₃₄ 、 mcm ⁵ s ² U ₃₄ 、 ncm ⁵ U ₃₄ 、 ncm ⁵ Um ₃₄的 tRNA 解码的密码子，修饰在ELP1、SLM3和TRM9 KO 菌株的蛋白质聚集体中过多。在这些菌株中，在专门映射到低修饰 tRNA 解码的密码子位点的蛋白质位点上还检测到氨基酸错误掺入率增加，这表明 U ₃₄ tRNA 修饰可保护蛋白质组免受翻译错误、蛋白质错误折叠和蛋白质毒性应激的影响。