The topoisomerase poison Camptothecin causes DNA damage resulting in apoptosis when bound with topoisomerase I and DNA complex through hydrogen bonds.
Camptothecin (CPT) is a topoisomerase poison. This prevents DNA re-ligation and therefore causes DNA damage which results in apoptosis. CPT binds to the topoisomerase I and DNA complex (the covalent complex) resulting in a ternary complex, and thereby stabilizing it. CPT binds both to the enzyme and DNA with hydrogen bonds. 
