Reduced mitomycin C induces heat-labile sites in DNA at specific sequences

We have investigated the sequence specificity of DNA damage induced by mitomycin C reduced with NaBH4, by using 3'- or 5'-end labeled DNA fragments of defined sequence. Mitomycin C reduced with NaBH4 induced heat-labile sites in DNA preferentially at specific sequences. The most preferred trinucleotide sequence for induction of heat-labile sites was GGT, followed by GGG, AGT, GAG, GGC and AGG. Active oxygens such as hydroxyl radical and singlet oxygen, and metal ions were involved in the induction of heat-labile sites. DNA was broken at the 3' side of deoxyguanosines and some of deoxyadenosines by heat-treatment. The produced oligonucleotides contained phosphoryl groups at the 5' termini. The 3' termini seemed not to have simple structures.