PDF(Pubmed)
Abstract：
Nonstructural protein 5 (Nsp5) is the main protease of SARS-CoV-2 that cleaves viral polyproteins into individual polypeptides necessary for viral replication. Here, we show that Nsp5 binds and cleaves human tRNA methyltransferase 1 (TRMT1), a host enzyme required for a prevalent post-transcriptional modification in tRNAs. Human cells infected with SARS-CoV-2 exhibit a decrease in TRMT1 protein levels and TRMT1-catalyzed tRNA modifications, consistent with TRMT1 cleavage and inactivation by Nsp5. Nsp5 cleaves TRMT1 at a specific position that matches the consensus sequence of SARS-CoV-2 polyprotein cleavage sites, and a single mutation within the sequence inhibits Nsp5-dependent proteolysis of TRMT1. The TRMT1 cleavage fragments exhibit altered RNA binding activity and are unable to rescue tRNA modification in TRMT1-deficient human cells. Compared to wildtype human cells, TRMT1-deficient human cells infected with SARS-CoV-2 exhibit reduced levels of intracellular viral RNA. These findings provide evidence that Nsp5-dependent cleavage of TRMT1 and perturbation of tRNA modification patterns contribute to the cellular pathogenesis of SARS-CoV-2 infection.
摘要：
非结构蛋白5(Nsp5)是SARS-CoV-2的主要蛋白酶,其将病毒多蛋白切割成病毒复制所必需的单个多肽。这里,我们显示Nsp5结合并切割人tRNA甲基转移酶1（TRMT1），tRNA中普遍的转录后修饰所需的宿主酶。感染SARS-CoV-2的人细胞表现出TRMT1蛋白水平降低和TRMT1催化的tRNA修饰，与TRMT1裂解和Nsp5失活一致。Nsp5在与SARS-CoV-2多蛋白切割位点的共有序列相匹配的特定位置切割TRMT1，序列内的单个突变抑制TRMT1的Nsp5依赖性蛋白水解。TRMT1裂解片段表现出改变的RNA结合活性,并且不能挽救TRMT1缺陷型人细胞中的tRNA修饰。与野生型人类细胞相比，用SARS-CoV-2感染的TRMT1缺陷的人细胞表现出降低的细胞内病毒RNA水平。这些发现提供了证据，证明Nsp5依赖性TRMT1的裂解和tRNA修饰模式的扰动有助于SARS-CoV-2感染的细胞发病机理。
