Date of Completion

7-29-2015

Embargo Period

7-25-2025

Keywords

DNA damage, mutation, translesion synthesis, polymerase, cancer, DNA repair

Major Advisor

Dr. Ashis K. Basu

Associate Advisor

Dr. Christian Brückner

Associate Advisor

Dr. Challa V. Kumar

Field of Study

Chemistry

Degree

Doctor of Philosophy

Open Access

Campus Access

Abstract

DNA is constantly exposed to various genotoxic stresses either from the environmental toxins or via cellular metabolism, which lead to DNA damages. The generation of a plethora of lesions in DNA perturbs DNA replication and may lead to a number of diseases or disorders. Genetic changes due to the exposure to various DNA damaging agents activate specialized safeguard mechanisms to save cells from the deleterious effects and to maintain genomic integrity. In the absence of these repair mechanisms, some of these lesions confer cellular toxicity and mutagenesis, which may contribute to neoplastic transformation. We have appraised the biological consequences of two very different DNA damaging agents: dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinolone-derived 2′-deoxyguanosine (dG) adducts (dG-C8-IQ and dG-N2-IQ) and a chemotherapeutic agent mitomycin c-derived dG adducts (MC-N2-dG and 2,7-DAM-N2-dG).

IQ is one of the heterocyclic amines found in cooked meat, presumably formed by the Maillard reaction when reducing sugars and amino acids are heated. In the research described in this thesis I have shown that the two dG adducts formed by IQ are mutagenic in human cells. I have also identified the specialized polymerases responsible for bypassing it. The mutagenic characteristics and replication blocking nature of the two IQ adducts were different and dependent on the DNA sequence context. My research provided the mechanistic basis of both the error-prone and error-free bypass of these two DNA lesions.

Mitomycin C is well known for its broad-spectrum antibiotic activity against a variety of tumors and is used extensively for several late-stage malignancies in humans. Mitomycin C forms many different DNA adducts, although its antitumor activity is believed to be due to its DNA cross linking ability which selectively kills cancer cells. However, I determined that the two dG adducts formed by mitomycin C and its major metabolite 2,7-diaminomitosene, the MC-N2-dG and 2,7-DAM-N2-dG, are mutagenic and cause significant replication blocks towards the bypass polymerases in human cells.

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Available for download on Friday, July 25, 2025

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