Date of Award

2025

Document Type

Open Access Thesis

Department

College of Pharmacy

First Advisor

Douglas Pittman

Abstract

Ribosomal proteins have been demonstrated to perform extra-ribosomal functions beyond protein synthesis, including roles in cell signaling, transcription regulation, apoptosis, and DNA repair. Ribosomal protein S3 (RPS3), in particular, has been implicated in DNA repair and apoptosis pathways, suggesting a critical role in maintaining genomic stability. However, the specific mechanisms involving RPS3 are still unknown, particularly in the context of double-stranded break (DSB) repair. DSBs are among the most severe types of DNA damage, often resulting in chromosomal instability or cell death if not properly repaired. Nonhomologous End Joining (NHEJ) and Homologous Recombination (HR) are the two primary DNA repair pathways of DSB repair. RPS3 has been shown to interact with RNF138, an E3 ligase involved in the RAD51 HR pathway. Based on these findings, I hypothesize that RPS3 facilitates homologous recombination mediated DNA repair during cellular stress by interacting with components of HR. To investigate this hypothesis, AlphaFold, an AI-based predictive modeling software, was utilized to predict possible direct interactions and structures of HR components with RPS3. Computational data suggests that RPS3 forms a ternary protein complex with RNF138 and RAD51D, two proteins directly involved in HR. To experimentally test for direct interactions, a Yeast-2-Hybrid assay was performed. However, Under the most stringent selection conditions, no direct interaction was detected between RPS3 and the tested HR proteins. Based on this data, I speculate that RPS3 may need additional cofactors to assist it in binding to HR proteins and assist in DSB repair. Future investigations should test RPS3 expression levels, folding configuration, and other binding factors. These findings will contribute to a more thorough understanding of RPS3’s role in Homologous Recombination and possible cellular stress response sensed during protein translation, potentially guiding the development of targeted therapies related to DSB repair deficient cancers.

Rights

© 2025, Jerome Robert Dorsey

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