Supercoil-accelerated DNA threading intercalation.

The effect of DNA supercoiling on a sterically very demanding threading intercalation process is investigated here. We find that the threading rate of a dimeric ruthenium complex into a negatively supercoiled plasmid at low binding density is 2 orders of magnitude higher than into the cleaved linear form. Further saturation is on the other hand kinetically hampered in comparison to the relaxed DNA. We also observe that threading kinetics correlates with the inhibition of luciferase expression from the plasmid construct. The results show how the target torsional strain can function as a control of DNA threading kinetics and gene expression efficiency.