TRIM7 ubiquitinates SARS-CoV-2 membrane protein to limit apoptosis and viral replication

SARS-CoV-2 is a highly transmissible virus that causes COVID-19 disease. Mechanisms of viral pathogenesis include excessive inflammation and viral-induced cell death, resulting in tissue damage. We identified the host E3-ubiquitin ligase TRIM7 as an inhibitor of apoptosis and SARS-CoV-2 replication via ubiquitination of the viral membrane (M) protein. Trim7-/- mice exhibited increased pathology and virus titers associated with epithelial apoptosis and dysregulated immune responses. Mechanistically, TRIM7 ubiquitinates M on K14, which protects cells from cell death. Longitudinal SARS-CoV-2 sequence analysis from infected patients revealed that mutations on M-K14 appeared in circulating variants during the pandemic. The relevance of these mutations was tested in a mouse model. A recombinant M-K14/K15R virus showed reduced viral replication, consistent with the role of K15 in virus assembly, and increased levels of apoptosis associated with the loss of ubiquitination on K14. TRIM7 antiviral activity requires caspase-6 inhibition, linking apoptosis with viral replication and pathology. Overall design: Next generation sequencing of Lung from mice WT and TRIM7 knockout infected with SARS-CoV-2 CMA3p20 at day 3 post-infection

严重急性呼吸综合征冠状病毒2型（SARS-CoV-2）是一种传播能力极强的病毒，可引发新型冠状病毒肺炎（COVID-19）。病毒的致病机制包括过度炎症反应以及病毒诱导的细胞死亡，进而导致组织损伤。我们鉴定出宿主E3泛素连接酶（E3-ubiquitin ligase）TRIM7可通过对病毒膜（M）蛋白的泛素化修饰，抑制细胞凋亡以及SARS-CoV-2的复制。TRIM7基因敲除小鼠表现出更严重的病理损伤与病毒载量升高，这与上皮细胞凋亡以及免疫应答失调相关。从机制层面来看，TRIM7可在病毒膜（M）蛋白的K14位点发生泛素化修饰，从而保护细胞免受细胞死亡的影响。对感染患者的纵向SARS-CoV-2序列分析显示，M-K14位点的突变在大流行期间的流行变异株中被检测到。我们在小鼠模型中验证了这些突变的生物学意义。重组M-K14/K15R病毒的复制能力减弱，这与K15在病毒组装中的功能相符，同时该病毒引发的细胞凋亡水平升高，这与K14位点泛素化修饰的缺失密切相关。TRIM7的抗病毒活性需要半胱天冬酶-6（caspase-6）的抑制作用，这将细胞凋亡与病毒复制及病理损伤建立了关联。实验整体设计：对感染SARS-CoV-2 CMA3p20毒株后第3天的野生型（WT）与TRIM7基因敲除小鼠的肺部组织进行下一代测序（next generation sequencing）。