DNA CURVATURE INFLUENCES THE INTERNAL MOTIONS OF SUPERCOILED DNA

We present evidence that short curved DNA segments can act as mediator s for the ordering of large domains in superhelical DNA. Using a non-i nvasive solution method (dynamic light scattering), we investigated th e effect of permanently curved inserts on the solution structure and o n the internal motions of superhelical plasmid DNA. We find that the d ynamics of superhelical DNA are strongly influenced by sequence- or pr otein-induced bending: in superhelical plasmids containing curved inse rts the amplitude of the internal motion is lower than that of non-cur ved controls. Furthermore, the relative arrangement of curved sequence s in the plasmids can influence the overall shape of the superhelical DNA. On linearized forms of the plasmids, these effects are not observ ed.