Mechanistic Studies on the Photooxidation of Methylated Cytosine in DNA and Its Application to Novel DNA Methylation Analysis

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Our interest focuses on the potential application of remarkable photooxidative reactivity of 5-methylcytosine (^mC) to methylation-mapping system and on further understanding the mechanism of photooxidation at ^mC in DNA. In the project, we revealed that (1) incorporation of an anthraquinone (AQ) sensitizer into a DNA strand enhanced one-electron photooxidation, leading to efficient strand cleavage at the ^mC site, (2) deprotonation at the C5-methyl group of an intermediate ^mC radical cation may occur as a key elementary reaction in the AQ-photooxidative strand cleavage at the ^mC, and (3) DNA strand cleavage at multiple ^mC residues was induced by AQ-photoinjected positive charge (hole) transfer through DNA duplex. The results obtained may provide a guide for the molecular design of highly sensitive and selective photochemical methods for the identification and analysis of ^mC in DNA.