Department or Program

Biological Chemistry


Encephalomyocarditis virus (EMCV) is a member of the picornavirus family whose single-stranded RNA genome encodes for proteins including an enzyme known as 3C protease (3Cpro) which is crucial for virus replication. Since the concentration of the EMCV 3Cpro is important for efficient viral replication in infected cells, it has been suggested that cellular 3Cpro concentrations must be regulated to maintain an optimal concentration. The ubiquitin proteasome system (UPS) is known to target the picornavirus 3C protease for degradation so we believe it participates in the regulation of 3C protease concentrations. The UPS tags proteins for degradation by attaching a polyubiqtuitin chain which is recognized by the 26S proteasome. The conjugation of ubiquitin follows a complex pathway through an E1, an E2, and an E3 enzyme. Very little is known about the pathways through which the UPS participates in the regulation of 3Cpro concentrations, but because we have shown ubiquitin-protein ligases UBE3A and DTX3L tag 3C protease with polyubiquitin chains, we examined their roles in the absence of, and during, picornavirus infection. DTX3L ubiquitin-protein ligase knockdown cell lines transfected with purified 3Cpro showed slower ubiquitylation rates of the protease suggesting it is important for the normal degradation of 3C protease in vivo. UBE3A is exclusively located in the nucleus, but cellular fractionation of cells infected with encephalomyocarditis virus showed that during infection a portion of the UBE3A is translocated out of the nucleus into the cytoplasm. The virus infection must therefore produce a cellular signal which translocates a portion of UBE3A out of the nucleus. These results suggest that not only are DTX3L and UBE3A important for the targeted degradation of 3C protease in vivo, but they are used by the virus to control the 3C protease concentration to optimize the viral infection and replication.

Level of Access

Restricted: Embargoed [Bates Community After Expiration]

First Advisor

Lawson, T. Glen

Date of Graduation


Degree Name

Bachelor of Science

Number of Pages


Components of Thesis

1 pdf file