Molecular basis of eIF5A-dependent CAT tailing in eukaryotic ribosome-associated quality control
Molecular basis of eIF5A-dependent CAT tailing in eukaryotic ribosome-associated quality control
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DOI：
10.1016/j.molcel.2023.01.020
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发表时间：
2023-02-16
期刊：
影响因子：
16
通讯作者：
Beckmann，Roland
中科院分区：
文献类型：
--
作者：
Tesina，Petr;Ebine，Shuhei;Beckmann，Roland
核糖体相关质量控制（RQC）是一个保守的过程，降解潜在的毒性截短的新生肽，其功能障碍的神经退行性变和蛋白质稳态下降的老化。在RQC期间，停滞的核糖体的解离之后是具有丙氨酸和苏氨酸残基的新生肽的延伸，其由独立于mRNA、小核糖体亚基和鸟苷三磷酸（GTP）水解因子的Rqc 2驱动。由此产生的CAT尾巴（羧基末端尾巴）和泛素化的Ltn 1标记新生肽蛋白酶体降解。在这里，我们提出了10个低温电子显微镜（cryo-EM）的结构，揭示了CAT加尾周期的各个步骤的机制基础，包括启动，解码，肽基转移和tRNA易位。我们发现eIF 5A作为一个重要的真核RQC因子，使肽基转移。此外，我们观察到RQC因子和tRNA的动态行为，允许CAT加尾循环的持续合成能力，而无需额外的能量输入。总之，这些结果阐明了CAT拖尾和规范翻译之间的关键差异以及共同原则。
Ribosome-associated quality control (RQC) is a conserved process degrading potentially toxic truncated nascent peptides whose malfunction underlies neurodegeneration and proteostasis decline in aging. During RQC, dissociation of stalled ribosomes is followed by elongation of the nascent peptide with alanine and threonine residues, driven by Rqc2 independently of mRNA, the small ribosomal subunit and guanosine triphosphate (GTP)-hydrolyzing factors. The resulting CAT tails (carboxy-terminal tails) and ubiquitination by Ltn1 mark nascent peptides for proteasomal degradation. Here we present ten cryogenic electron microscopy (cryo-EM) structures, revealing the mechanistic basis of individual steps of the CAT tailing cycle covering initiation, decoding, peptidyl transfer, and tRNA translocation. We discovered eIF5A as a crucial eukaryotic RQC factor enabling peptidyl transfer. Moreover, we observed dynamic behavior of RQC factors and tRNAs allowing for processivity of the CAT tailing cycle without additional energy input. Together, these results elucidate key differences as well as common principles between CAT tailing and canonical translation.