2007 Volume 81 Issue 7 Pages 297-302
Direct attack to genomic DNA by reactive oxygen species causes various types of lesions. The most significant lesion is considered to be an unrepaired double-strand break that can lead to fatal cell damage. Using fluorescence microscopy, we directly observed double-strand breaks of DNA in reconstituted chromatin stained by a fluorescent cyanine dye, YOYO, in solution. YOYO is known to have the ability to photo-cleave DNAs by generating reactive oxygen species. We also investigated the effect of an antioxidant vitamin, vitamin C, on preventing double-strand breaks in a quantitative manner. We showed that doublestrand breaks can be monitored at the level of individual DNA molecules, and that the kinetics of the breakage reaction can be deduced from such single-molecule observation. We found that DNA is protected against double-strand breaks by the addition of vitamin C.
