Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Microbiology and Immunology


Coronaviruses (CoVs) are positive-sense RNa viruses that can emerge from endemic reservoirs and infect zoonotically, causing significant morbidity and mortality. CoVs encode an endoribonuclease (EndoU) that cleaves RNa in biochemical assays, but the target and function of EndoU activity during viral replication was not known. My work focused on characterizing the functions of EndoU during infection. I report that EndoU is an innate immune antagonist. to function as an immune antagonist, EndoU cleaves the 5'-Poly-Uridines from Negative-sense viral RNA, termed PUN RNA, which is the product of polyA-templated RNa synthesis. Using a virus containing an EndoU catalytic-inactive mutation, I detected a higher abundance of PUN RNa in the cytoplasm of infected cells compared to wild type CoV-infected cells. Furthermore, we found that transfecting PUN RNa into cells stimulates a robust, MDA5-dependent interferon response, and that removal of the polyU-extension on the RNa dampens the response. Overall, the results of this study reveal the PUN RNa to be a novel CoV MDA5-dependent pathogen associated molecular pattern (PAMP). We also establish a mechanism for EndoU activity to cleave and limit the accumulation of this novel PAMP. Since EndoU activity is highly conserved in all coronaviruses, inhibiting this activity may serve as an approach for therapeutic interventions against existing and emerging CoV infections.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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