Figure 4.

Heat stability of the top1 cleavage complexes trapped by the trans-10R- and 10S-N⁶-BaP DE-2 dA adducts in the upper strand. The oligonucleotides indicated at the top of the figure were reacted as follows: for the control oligonucleotide, lane C, no treatment (control); lane T, top1 without camptothecin; lanes 0, 1, 3, 10, and 20, top1 + camptothecin (10 μM) for 30 min at 25°C followed by the indicated times (min) at 65°C. For the trans-R and -S adducted oligonucleotides (without camptothecin): lanes C, no treatment (control); lanes 0, 1, 3, 10, and 20, top1 for 30 min at 25°C followed by the indicated times (min) at 65°C. Size of the fragments generated by top1 with the 3′-end labeled oligonucleotide (including the cordycepin label) is indicated to the left of the gel.