Camilloni G, Di Martino E, Caserta M, di Mauro E
Centro di Studio per gli Acidi Nucleici, CNR, Rome, Italy.
Nucleic Acids Res. 1988 Jul 25;16(14B):7071-85. doi: 10.1093/nar/16.14.7071.
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.
