Analysis of Papain-like Protease Mediated Processing and Roles of the Cleavage Products in Coronavirus Replication

Abstract

Coronaviruses belong to a family of enveloped, positive-strand RNA viruses that cause a multitude of devastating diseases in both animals and humans. Like other positive-strand RNA viruses, coronaviruses utilize several common mechanisms to support critical steps in their life cycle. Two of these mechanisms are inducing cellular membrane rearrangements to support viral RNA synthesis and utilizing polyprotein processing to regulate protein expression and function. A well-established model used to study virus replication and the life cycle of coronaviruses is murine hepatitis virus (MHV). For MHV, gene 1 nonstructural proteins (nsps), which are proteolytically processed from the replicase polyprotein into their mature form by three virus-encoded proteases, are hypothesized to mediate many aspects of the virus life cycle, including modification of intracellular membranes, formation of replication complexes, and viral RNA synthesis. Nevertheless, much is still unknown about the requirements of protein processing and the roles individual proteins play during the coronavirus life cycle. To aid in our understanding of coronavirus replication, the research presented in this dissertation addressed the requirements of virus papain-like protease (PLP) processing on nsps 1 through 4 and the roles that these individual proteins play in the virus life cycle. The results of these studies provide new information about how coronaviruses regulate protein processing, nsps’ functions, viral RNA synthesis, and virus-induced membrane modifications. These results are also expected to contribute to the rational design of therapeutics aimed at preventing and inhibiting coronavirus-induced diseases.