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.