Eukaryotic DNA topoisomerase I reaction is topology dependent.
The effects of supercoiling on the topoisomerization reaction by eukaryotic DNA topoisomerases I have been analyzed. The systems used were: DNA topoisomerase I from wheat germ, chicken erythrocyte and calf thymus on a 2.3 kb DNA fragment which encompasses the immunoglobulin kappa-light chain (L kappa) promoter of the mouse plasmacytoma MPC11; S. cerevisiae DNA topoisomerase I on a 2.2 kb DNA fragment from the same organism which encompasses the regulatory and the coding region of the ADH II gene; wheat germ DNA topoisomerase I on the plasmid pUC18. It was found in every system that lack of torsional stress prevents topoisomerization of the substrate. A simple regulatory model of DNA topoisomerase I function, based on topological considerations, is presented.
Camilloni
G
G
Centro di Studio per gli Acidi Nucleici, CNR, Rome, Italy.
Di Martino
E
E
Caserta
M
M
di Mauro
E
E
D000426:Alcohol Dehydrogenase / Q000235:genetics; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004270:DNA, Circular / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D005057:Eukaryotic Cells; D005803:Genes, Immunoglobulin; D007145:Immunoglobulin kappa-Chains; D066298:In Vitro Techniques; D007700:Kinetics; D009690:Nucleic Acid Conformation; D010957:Plasmids; D013329:Structure-Activity Relationship
D004270:DNA, Circular; D004278:DNA, Superhelical; D007145:Immunoglobulin kappa-Chains; D000426:Alcohol Dehydrogenase; D004264:DNA Topoisomerases, Type I