Author ORCID Identifier

https://orcid.org/0000-0003-1525-791X

Year of Publication

2021

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department/School/Program

Plant Pathology

First Advisor

Dr. Peter D. Nagy

Abstract

Although host cells are a rather rich source for co-opted host factors, lipids and metabolites, positive stranded RNA viruses vastly rewire cellular pathways and remodel cellular membranes to support viral replication. To accomplish such major changes, these viruses depend on the availability of different host factors and the ability to readily assemble viral replication organelles (VROs). Genome-wide screens and proteomics approaches with Tomato Bushy Stunt Virus (TBSV) in a yeast model host indicated that tombusviruses rely on the cellular cytoskeleton to reorganize the cellular environment of their hosts. Using temperature-sensitive (ts) mutants of beta and gamma-tubulin proteins and pharmacological inhibitors, I demonstrated that the dynamic microtubular network restricts TBSV replication.

Moreover, changes in the structure of microtubules greatly interfere with the actin structure as well, leading to problems in the subversion of selected host factors into replicase complexes and the enrichment of sterols at replication sites. In addition to the efficient recruitment of co-opted host factors, lipids and metabolites to the sites of viral replication, tombusviruses promote the biogenesis and accumulation of host factors that facilitate the production of energy required to fuel replication.

I discovered that Centromeric Histone H3 (CENH3), an essential chromatin-associated protein, has a non-canonical role during virus replication, as a regulator of the biosynthesis of several glycolytic enzymes that are necessary to generate ATP within the viral replication compartment. This function is achieved by the binding of this protein with components of the viral replication machinery such as the RNA chaperone p33 and the viral repRNA, a function that is initially inhibitory but that is circumvented by the virus to reach optimal replication.

Altogether, the studies with the microtubule cytoskeleton and CENH3 revealed an emerging picture for (+)RNA tombusviruses, suggesting that the extensive rewiring of metabolic pathways and remodeling of cellular membranes that support viral replication, requires the activities of particular kinds of cell-intrinsic restriction factors (CIRFs). These types of factors, which I called negative regulatory CIRFs, have an intrinsic inhibitory function but are exploited by the virus to achieve robust replication at the expense of certain viral resources.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.080

Available for download on Thursday, November 11, 2021

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