Heparin and Liver Heparan Sulfate Can Rescue Hepatoma Cells from Topotecan Action

Figure 6

Competition of heparin and DNA for topoisomerase I (representative image of three independent experiments). Effect of heparin on the DNA gel retardation produced by 10 U purified topoisomerase I protein. DNA fragment of 516 base pair size with 8 potential topo I-binding sequences was end-labeled with digoxigenin-UTP. Thirty-five ng DNA was incubated with 10 U topoisomerase I alone or in the presence of 10 and 100 ng heparin. Samples were run or 1% agarose, blotted to nylon membrane, and developed with antidigoxigenin alkaline phosphatase. 1: control DNA, without protein; 2 and 3: DNA with topoisomerase I; 4 and 5: DNA and topoisomerase I, with 10 and 100 ng heparin, respectively.