Base specificity for DNA interstrand cross-linking induced by anticancer agent bizelesin

Bizelesin is a promising novel anticancer agent which is known to alkylate N3 of adenine to induce DNA interstrand cross-links (ISC) within 5′-TAATTA and 5′-TAAAAAA. We have investigated the base specificity for DNA ISC induced by bizelesin using oligomers containing the cross-linkable sequence 5′-TAATTN, in which “N” was either A, C, G, or T. An analysis of denaturing polyacrylamide gel showed that bizelesin is able to induce DNA ISC in the duplex oligomer containing sequences 5′-TAATTA and 5′-TAATTG. The formation of interstrand cross-linking did not occur in the sequences 5′-TAATTC and 5′-TAATTT. DNA strand cleavage assay to determine the cross-linking site within 5′-TAATTG sequence showed that bizelesin alkylates guanine. These results demonstrate that bizelesin is able to induce DNA ISC at guanine but not at cytosine or thymine. In addition, guanine adducts have been found to be susceptible to DNA strand cleavage by exposure to hot piperidine. The extent of DNA strand cleavage, however, was not 100% efficient in either neutral pH buffer or hot piperidine.