Description
Human DNA Topoisomerase I is the best studied of the DNA topoisomerase family. It catalyzes the relaxation of both positive and negative supercoiled DNAs 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 expanded from amino acids 215 to 636 is highly conserved and retains DNA binding activity. The substrate specificity of 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. The core domain of DNA Topoisomerase I protein (residues 197-651) was expressed in baculovirus system and purified by using an affinity column and FPLC chromatography. Purified core domain of Topo I can be used for DNA binding and protein-protein interaction assays. It can be also reconstituted with the C-terminal domain to restore the DNA relaxation activity in vitro