Author ORCID Identifier

https://orcid.org/0000-0002-4690-510X

Semester

Summer

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Biology

Committee Chair

Jennifer Gallagher

Committee Member

Jennifer Hawkins

Committee Member

John Woolford

Committee Member

Vagner Benedito

Abstract

This study focuses on ribosome-inactivating proteins (RIPs), a class of potent toxins that includes ricin, α-sarcin, and shiga toxin, which irreversibly damage large subunit rRNA. Although the catalytic activity of ricin toxin A chain (RTA) is well characterized, the precise mechanisms linking ribosome damage to altered cellular morphology remain poorly understood. In this study, we engineered a tetracycline-regulatable expression system to express RTA in Saccharomyces cerevisiae. We characterized the effects of RTA expression on yeast growth, viability, and reproductive potential. We demonstrated that our expression system produced rapid and robust RTA expression and ribosome depurination within less than one hour of induction, establishing this system as an improvement over previous methods. High-throughput genetic screens were conducted using the full yeast knockout collection to identify elements that increase or decrease sensitivity to RTA intoxication. Our findings indicate that the RTA’s phenotype is strongly influenced by deletions to cytosolic and mitochondrial ribosomal proteins, as well as broader stress response pathways such as autophagy.

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