Formation and properties of endogenous adducts and crosslinks generated by amine-catalyzed strand cleavage at an AP site in duplex DNA
Abstract
Abasic sites in DNA are a very common lesion. They are formed spontaneously and in the presence of biological amines, enzymes, and proteins. If unrepaired, abasic sites lead to DNA strand breaks and crosslinks. This thesis describes the development of nucleoside system that enabled chemical characterization of the sugar remnants generated by amine-catalyzed (beta)-elimination in the 2-deoxyribose system. The products generated by amine-catalyzed strand break at abasic sites in cellular DNA are more complex than commonly thought, with trans-(alpha), (beta)-unsaturated iminium ion intermediates residing at the hub of interconverting product mixtures. This leads to the generation of noncanonical cleavage products including cis-alkenal, 3-thio-2, 3-dideoxyribose, and 2-deoxyribose groups alongside the canonical trans-alkenal residue on the 3'-terminus of the strand break. In cellular environment, glutathione rapidly adds to the trans-alkenal residue on the 3'-terminus of an AP-derived strand break making 3'-glutathionylated sugar remnant the true strand cleavage product arising from (beta)-elimination at an abasic site in cellular DNA. This thesis also portrays the chemical characterization of interstrand crosslink arising from aza-Michael addition of the N2-amino group of a guanine residue to the electrophilic sugar remnant generated by spermine-mediated strand cleavage at an AP site in duplex DNA.
Degree
Ph. D.