Date of Award

Spring 5-2022

Document Type

Honors Thesis

Degree Name

Bachelor of Science

Department

Biological Science

Advisor/Committee Chair

Thomas Begley, Ph.D.

Committee Member

Jason Herschkowitz, Ph.D.

Abstract

Transfer RNAs decode messenger RNA using anticodon – codon interactions to deliver specific amino acids to a growing peptide chain. Enzyme-catalyzed modifications on specific nucleotides on tRNAs increase their stability and help mediate the speed and fidelity of translation, giving these modifications regulatory potential. RNA modifications are catalyzed by writer enzymes, and I predicted that writers are important in the cellular responses to stress. I have evaluated the following E. coli modification enzyme mutants: miaA, mnmE, dtd, tmcA, lysU, yeaK, and iscS, from the corresponding Keio E. coli gene deletion library. Writer mutants were exposed to hydrogen peroxide to induce an oxidative stress response. The knockouts of iscS (which transfers sulfur to tRNA), miaA (which transfers dimethylallyl to tRNATyr and tRNAPhe), and tmcA (which aceylates the wobble base on tRNAMet) showed growth sensitivity to hydrogen peroxide. Additional gene deletion mutants were also sensitive including those encoded by tusA/tusC/tusD (sulfur mediators), mnmA (catalyzes 2-thiouridine modification), and iscU (scaffold protein, works with iscS). Sulfur transfer to tRNA was highlighted to be important in the response to hydrogen peroxide, as several gene deletions in this pathway exhibit sensitivity to oxidative stress, and it is possible that the sulfurtransferase pathway is critical to the oxidative stress response. Existing literature shows that sulfurtransfer is also critical in the oxidative stress response in mice and humans (Nakajima, 2015). Computational work was also performed using the Basic Local Alignment Search Tool (BLAST) and the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING), which were used to discover connections between bacterial genes and to human orthologs. A connection to disease was found for tmcA and miaA and iscS, as their human orthologs are linked to oxidative phosphorylation deficiency disorders. Ultimately, my project has provided insight into the role of writers in the response to oxidative stress.

Available for download on Thursday, December 01, 2022

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