Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Microbiology and Immunology

Supervisor

Mymryk, Joe S

Abstract

As an obligate intracellular parasite, human adenovirus (HAdV) must utilize host factors for survival and replication. Early during infection, its multifunctional E1A protein interacts with an impressive range of cellular target proteins to exert control over the cellular environment. Through these virus-host interactions, E1A massively reprograms both viral and cellular transcription to activate the other HAdV genes, downregulate the host’s immune response, and induce the cell cycle. Consequently, E1A converts the infected cell into a compliant state more amenable for HAdV replication, resulting from its numerous protein-protein interactions. I sought to examine E1A’s interaction with cellular protein kinase A (PKA), a well-studied component of host cAMP signaling that plays a critical role in cellular transcription. While characterizing the molecular determinants of the E1A-PKA interaction, I showed that E1A uses mimicry of cellular A-kinase anchoring proteins (AKAPs) to usurp PKA for the benefit of HAdV. This mechanism allowed E1A to outcompete endogenous AKAPs and induce an E1A-mediated relocalization of PKA into the nucleus of infected cells. Here, PKA was recruited to viral gene promoters. This ultimately resulted in increased viral transcription from these loci as well as enhanced protein synthesis and higher levels of viral replication. This mechanism of mimicry was conserved in E1A proteins across various, distinct species of HAdV, indicating its evolutionary importance. Interestingly, different E1A proteins displayed a preference for manipulating one type of PKA isoform over another. Despite mechanistic differences, all species of HAdV that commandeered PKA via their E1A proteins required this action for wild-type levels of both viral genome replication and infectious progeny production. Additionally, these E1A proteins could induce transcription from a cAMP- and PKA-regulated reporter gene suggesting that this interaction may modulate host genes in a manner similar to viral ones. Together, these studies show that manipulation of PKA by E1A is a conserved feature of diverse HAdVs. This allows these viruses to subvert cellular cAMP signaling and use a host factor to enhance multiple aspects of their replication cycles. Furthermore, this mechanistically demonstrates HAdV E1A as the first known viral AKAP – a unique form of viral mimicry.

Download

Share

COinS