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Bad things come in pairs When DNA is subjected to -radiation—a common treatment for cancer—most of the DNA damage is clustered at pairs of nucleotides, a new study shows. Unlike other types of DNA damaging agents, -radiation of DNA initially yields mostly nucleobase radicals. Chemistry professor Marc M. Greenberg and graduate student K. Nolan Carter of Johns Hopkins University have generated a pyrimidine nucleobase radical in a stretch of duplex DNA. They show that the products of this reactive intermediate are mostly pairs of DNA lesions, side-by-side in a single strand of DNA [J. Am. Chem. Soc., 125, 13376 (2003)]. To date, most studies have focused on the transformation of nucleobase radicals into breaks in DNA or isolated modified nucleotides, not such “tandem lesions.” But Greenberg and Carter find that tandem lesions outnumber any other type of damage, accounting for about two-thirds of the total amount of damage. Although the biological role of tandem lesions is uncertain, Greenberg tells C&EN that their results suggest that tandem lesions deserve more attention. |
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