Sequence-selectivity of 5,11-dimethyl-5H-indolo[2,3-b]quinoline binding to DNA. Footprinting and molecular modeling studies.

Indolo[2,3-b]quinolines are a new family of the DNA intercalators showing significant cytotoxic activity. The mechanism of their action is based on the inhibition of DNA topoisomerase II activity. It depends on their ability to induce and stabilize drug-topII-DNA cleavable complexes. Site-specific intercalation of 5,11-dimethyl-5H-indolo[2,3-b]quinoline (DiMIQ) was analyzed in vitro by DNaseI footprinting and by molecular modeling. To model the DNA-intercalator complex, use was made of the CVFF and ESFF force fields implemented in Insight 97.0 software. Experimental results were verified using a simple statistical model. The DiMIQ molecule was found to bind preferentially to the pBR322 DNA plasmid in the 5'-TGCTAACGC-3' region between adjacent adenine bases.