Characterization of the 2,6-Diamino-4-hydroxy-N5-(methyl)-formamidopyrimidine DNA Lesion
Bamberger, Stephanie Nicole
Alkylating agents, once a weapon of war employed in World War I, are the oldest class of chemotherapeutic agents still used today, with applications in treating a wide array of cancers. Methylating agents, in particular, have been widely used in the treatment of brain tumors, increasing the average lifespan of patients. Methylating agents function by reacting with DNA, forming DNA adducts and triggering cell death. The most prevalent DNA adduct formed upon exposure to methylating agents, 7-methylguanine (7Me-dG), has long been thought of as being relatively innocuous. In recent years the 7Me-dG adduct has come to the attention of scientists due to its ability to react with hydroxide, forming the mutagenic and cytotoxic 2,6-diamino-4-hydroxy-N5-(methyl)-formamidopyrimidine (MeFapy-dG) adduct. Studies conducted on the MeFapy-dG adduct in multiple systems revealed it exists as a complex mixture of isomers in equilibrium, the populations of which are dependent on the system it is located in. A methodology was developed to rapidly identify discrete species of MeFapy-dG in solution, negating the need for arduous separations of isomers prior to experiments. Intriguingly, the isomeric population of MeFapy-dG appears to show a dependence on the identity of neighboring nucleotides when incorporated into duplex DNA, supporting the hypothesis that the diverse mutational spectra that occur upon bypass of this adduct, previously found to be sequence specific, arise from different isomeric distributions of MeFapy-dG, which are governed by interactions with neighboring nucleotides.