Date of Award
1-17-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Microbiology and Immunology
First Advisor
Susan Baker
Abstract
Identifying conserved mechanisms used by viruses to delay host innate responses can reveal potential targets for antiviral therapeutics. Here, we investigated coronavirus nonstructural protein 15 (nsp15), which encodes a highly conserved endoribonuclease (EndoU). EndoU functions as an immune antagonist by limiting the accumulation of viral replication intermediates that would otherwise be sensed by the host. Despite being a promising antiviral target, it has been difficult to develop small molecule inhibitors that target the EndoU active site. We generated nsp15 mutants of SARS-CoV-2 and mouse coronavirus MHV-A59 and identified conserved residues within the amino-terminal domain that are required for EndoU activity. Loss of EndoU activity caused the activation of host sensors, which limited viral replication in interferon responsive cells and attenuated disease in MHV-infected mice. Using transcriptional profiling, we found that MHV EndoU mutant viruses upregulate multiple host sensors, including Z-form nucleic acid-binding protein 1 (ZBP1). We found that nsp15 mutants induced early, robust ZBP1-mediated necroptosis. EndoU mutant viruses also induced ZBP1-independent apoptosis and pyroptosis pathways, causing early, robust cell death that limits virus replication and pathogenesis. Overall, we document the importance of the amino-terminal domain for EndoU function. We also highlight the importance of nsp15/EndoU activity for evading host sensors, delaying cell death, and promoting pathogenesis.
Recommended Citation
Evdokimova, Monika, "Investigating the Role of the NSP15 Amino-Terminal Domain in NSP15 Function, Viral Replication, and Pathogenesis" (2025). Dissertations. 4163.
https://ecommons.luc.edu/luc_diss/4163
