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 wild-type 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.
The virus responsible for COVID-19 infections is known as SARS-CoV-2. Like all viruses, SARS-CoV-2 carries instructions to make proteins and other molecules that play essential roles in enabling the virus to multiply and spread. Viruses are unable to make these molecules themselves, so they infect cells and trick them into making the molecules and assembling new virus particles on their behalf instead. When SARS-CoV2 infects cells, the host cells are reprogrammed to make chains containing several virus proteins that need to be severed from each other by a virus enzyme, known as Nsp5, to enable the proteins to work properly. Previous studies suggested that Nsp5 may also interact with a human protein known as TRMT1, which helps with the production of new proteins in cells. However, it was not clear how Nsp5 may bind to TRMT1 or how this interaction may affect the host cell. Zhang et al. used biochemical and molecular techniques in human cells to study how Nsp5 interacts with TRMT1. The experiments found that the virus enzyme cuts TRMT1 into fragments that are inactive and are subsequently destroyed by the cells. Moreover, Nsp5 cuts TRMT1 at exactly the same position corresponding to the cleavage sites of the viral proteins. Mutation of the sequence in TRMT1 renders Nsp5 ineffective at cutting the protein. SARS-CoV-2 infection caused TRMT1 levels to decrease inside the cells, in turn, leading to a drop in TRMT1 activity. The virus multiplied less in cells that were unable to produce TRMT1 compared to normal human cells, suggesting that the virus benefits from TRMT1 early during infection, before inactivating it at a later point. These findings suggest that one way SARS-CoV-2 causes disease is by decreasing the levels of a human protein that regulates protein production. In the future, the work of Zhang et al. may provide new markers for detecting infections of SARS-CoV-2 and other similar viruses and guide efforts to make more effective therapies against them.
The virus responsible for COVID-19 infections is known as SARS-CoV-2. Like all viruses, SARS-CoV-2 carries instructions to make proteins and other molecules that play essential roles in enabling the virus to multiply and spread. Viruses are unable to make these molecules themselves, so they infect cells and trick them into making the molecules and assembling new virus particles on their behalf instead. When SARS-CoV2 infects cells, the host cells are reprogrammed to make chains containing several virus proteins that need to be severed from each other by a virus enzyme, known as Nsp5, to enable the proteins to work properly. Previous studies suggested that Nsp5 may also interact with a human protein known as TRMT1, which helps with the production of new proteins in cells. However, it was not clear how Nsp5 may bind to TRMT1 or how this interaction may affect the host cell. Zhang et al. used biochemical and molecular techniques in human cells to study how Nsp5 interacts with TRMT1. The experiments found that the virus enzyme cuts TRMT1 into fragments that are inactive and are subsequently destroyed by the cells. Moreover, Nsp5 cuts TRMT1 at exactly the same position corresponding to the cleavage sites of the viral proteins. Mutation of the sequence in TRMT1 renders Nsp5 ineffective at cutting the protein. SARS-CoV-2 infection caused TRMT1 levels to decrease inside the cells, in turn, leading to a drop in TRMT1 activity. The virus multiplied less in cells that were unable to produce TRMT1 compared to normal human cells, suggesting that the virus benefits from TRMT1 early during infection, before inactivating it at a later point. These findings suggest that one way SARS-CoV-2 causes disease is by decreasing the levels of a human protein that regulates protein production. In the future, the work of Zhang et al. may provide new markers for detecting infections of SARS-CoV-2 and other similar viruses and guide efforts to make more effective therapies against them.
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。
导致COVID-19感染的病毒被称为SARS-CoV-2。像所有的病毒一样，SARS-CoV-2带有制造蛋白质和其他分子的指令，这些分子在使病毒繁殖和传播中起着至关重要的作用。病毒无法自己制造这些分子，所以它们感染细胞，诱使它们制造分子并代表它们组装新的病毒颗粒。当SARS-CoV2感染细胞时，宿主细胞被重新编程，以制造含有几种病毒蛋白的链，这些蛋白需要通过病毒酶彼此切断，称为Nsp5，以使蛋白质正常工作。先前的研究表明，Nsp5也可能与称为TRMT1的人类蛋白质相互作用，这有助于在细胞中产生新的蛋白质。然而,尚不清楚Nsp5如何与TRMT1结合或这种相互作用如何影响宿主细胞。张等人。在人体细胞中使用生化和分子技术来研究Nsp5如何与TRMT1相互作用。实验发现，病毒酶将TRMT1切割成无活性的片段，随后被细胞破坏。此外，Nsp5在对应于病毒蛋白切割位点的完全相同的位置切割TRMT1。TRMT1中序列的突变使得Nsp5在切割蛋白质时无效。SARS-CoV-2感染导致细胞内TRMT1水平降低，反过来,导致TRMT1活性下降。与正常人细胞相比，该病毒在无法产生TRMT1的细胞中繁殖较少，表明该病毒在感染早期受益于TRMT1，在稍后将其停用之前。这些发现表明，SARS-CoV-2导致疾病的一种方式是通过降低调节蛋白质产生的人类蛋白质的水平。在未来,张等人的工作。可以为检测SARS-CoV-2和其他类似病毒的感染提供新的标记，并指导对它们进行更有效的治疗。
导致COVID-19感染的病毒被称为SARS-CoV-2。像所有的病毒一样，SARS-CoV-2带有制造蛋白质和其他分子的指令，这些分子在使病毒繁殖和传播中起着至关重要的作用。病毒无法自己制造这些分子，所以它们感染细胞，诱使它们制造分子并代表它们组装新的病毒颗粒。当SARS-CoV2感染细胞时，宿主细胞被重新编程，以制造含有几种病毒蛋白的链，这些蛋白需要通过病毒酶彼此切断，称为Nsp5，以使蛋白质正常工作。先前的研究表明，Nsp5也可能与称为TRMT1的人类蛋白质相互作用，这有助于在细胞中产生新的蛋白质。然而,尚不清楚Nsp5如何与TRMT1结合或这种相互作用如何影响宿主细胞。张等人。在人体细胞中使用生化和分子技术来研究Nsp5如何与TRMT1相互作用。实验发现，病毒酶将TRMT1切割成无活性的片段，随后被细胞破坏。此外，Nsp5在对应于病毒蛋白切割位点的完全相同的位置切割TRMT1。TRMT1中序列的突变使得Nsp5在切割蛋白质时无效。SARS-CoV-2感染导致细胞内TRMT1水平降低，反过来,导致TRMT1活性下降。与正常人细胞相比，该病毒在无法产生TRMT1的细胞中繁殖较少，表明该病毒在感染早期受益于TRMT1，在稍后将其停用之前。这些发现表明，SARS-CoV-2导致疾病的一种方式是通过降低调节蛋白质产生的人类蛋白质的水平。在未来,张等人的工作。可以为检测SARS-CoV-2和其他类似病毒的感染提供新的标记，并指导对它们进行更有效的治疗。
