UC Riverside

Endogenous metabolism and environmental exposure unavoidably give rise to the formation of DNA adducts, which may compromise cellular functions by blocking DNA replication and/or inducing mutations. Multiple lines of evidence support that mutations in relevant target genes, particularly oncogenes and tumor suppressor genes, are associated with carcinogenic process. Thus, the impact of DNA lesions on the fidelity and efficiency of replication are of great importance in cancer etiology. In this dissertation, I focus on two major types of DNA damage, alkylated and oxidized DNA lesions, and investigate how they compromise DNA replication.

Understanding the biological consequences of DNA lesions often necessitates the availability of oligodeoxyribonucleotide (ODN) substrates harboring these lesions, and sensitive and robust methods for validating the identities of these ODNs. Tandem mass spectrometry is well suited for meeting these latter analytical needs. In Chapter 2, I investigated the different fragmentation pattern exhibited by the position and size of alkyl groups on thymine as well as the oxidation of thymine 5-methyl carbon. In Chapters 3 and 4, I set out to assess the impact of O2- and O4- alkylated thymidines on DNA replication in Escherichia coli cells with the competitive replication and adducts bypass (CRAB) assay, and revealed the two distinct mutagenic properties of these regioisomeric alkylated thymidines. In Chapter 5, a unique group of oxidized DNA lesions was interrogated, and it was found that the C3' epimeric lesions of 2'-deoxyribonucleoside (i.e. 2'-deoxyxylonucleosides) do not profoundly compromise DNA replication.