Sequence preferences of DNA interstrand cross-linking agents: dG-to-dG cross-linking at 5'-CG by structurally simplified analogues of mitomycin C.

The nucleotide sequence preferences of the DNA interstrand cross-linking agents dehydroretronecine diacetate (DHRA), 2,3-bis(acetoxymethyl)-1-methylpyrrole (BAMP), dehydromonocrotaline, and dehydroretrorsine were studied by using synthetic DNA duplex fragments and polyacrylamide gel electrophoresis (PAGE). These agents have structural features in common with the reductively activated aziridinomitosene of mitomycin C (MC). Like MC, they preferentially cross-linked DNA duplexes containing the duplex sequence 5'-CG. For DHRA and BAMP interstrand cross-linked DNA duplexes, PAGE analysis of iron(II)-EDTA fragmentation reactions revealed the interstrand cross-links to be deoxyguanosine to deoxyguanosine (dG-to-dG), again analogous to DNA cross-links caused by MC. Unlike MC, DHRA could be shown to dG-to-dG cross-link a 5'-GC sequence. Furthermore, the impact of flanking sequence on the efficiency of interstrand cross-linking at 5'-CG was reduced for BAMP, with 5'-TCGA and 5'-GCGC being equally efficiently cross-linked. Possible origins of the 5'-CG sequence recognition common to all of the agents are discussed. A model is presented in which the transition state for the conversion of monoadducts to cross-links more closely resembles ground-state DNA at 5'-CG sequences.