Description General description Recombinant, human topoisomerase I fused to a His•Tag sequence and expressed in S. frugiperda insect cells. 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. Since Topo I can cause large amounts of single-strand DNA breaks it is an important target for antitumor agents. One unit= 1 ng protein. Recombinant, human topoisomerase I fused to a His•Tag sequence and expressed in S. frugiperda insect cells. 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 role in pre-mRNA splicing, cell cycle and other gene regulatory pathways during cell growth and development. DNA Topo I is an important target for ant-tumor agents as a result of the fact that is causes single-strand DNA breaks of the type that are present in most cancers. Packaging 1 set in Glass bottle Biochem/physiol Actions 0.1-1 unit (ng) is sufficient for relaxing 0.5 µg of pBR322 supercoiled DNA in a 20 µl reaction. Packaging Please refer to vial label for lot-specific concentration. Warning Toxicity: Standard Handling (A) Physical form 5000 U enzyme in 100 mM KCl, 20 mM Tris-HCl, 1 mM DTT, 200 µM EDTA, 20% glycerol, pH 7.9 and 1 vial dilution buffer (100 mM KCl, 20 mM Tris-HCl, 1 mM DTT, 0.2 mM EDTA, 20% glycerol, pH 8.0). Reconstitution Following initial thaw aliquot and freeze (-70°C). For storage of diluted protein, dilute in storage buffer with 500µg/ml molecular biology grade BSA, aliquot, and freeze (-70°C). Other Notes Pommier, Y., et al. 1998. Biochim. Biophys. Acta1400, 83. Pourquier, P., et al. 1997. J. Biol. Chem.272, 26441. Rossi, F., et al. 1996. Nature381, 80. Sekiguchi, J., et al. 1996. Proc. Natl. Acad. Sci. USA93, 785. Giovanella, B.C., et al. 1989. Science246, 1046. Wang, J,C. 1985. Annu. Rev. Biochem.54, 665.