Description_x000D_ Biochem/physiol Actions_x000D_ Human DNA topoisomerase I is the best studied of the DNA topoisomerase family. It catalyzes the relaxation of both positive and negative supercoils without the requirement of energy. In addition to DNA replication and transcriptional activation, DNA topoisomerase I also plays a major role in pre-mRNA splicing, cell cycle and other gene regulatory pathways during cell growth and development. The core domain spanning from amino acids 215 to 636 is highly conserved and retains DNA binding activity. Topo I has been found to nick the DNA with a preference of 5’-(A/T)(G/C)(A/T)T-3’. Camptothecin and its analogs have been tested as potent anticancer compounds by stabilizing topo I-DNA complex, thereby inhibiting both DNA and RNA synthesis._x000D_ Physical form_x000D_ Clear and colorless frozen liquid solution_x000D_ Preparation Note_x000D_ Use a manual defrost freezer and avoid repeated freeze-thaw cycles. While working, please keep sample on ice.