Generation of superhelical torsion by ATP-dependent chromatin remodeling activities

ATP-dependent chromatin remodeling activities participate in the alteration of chromatin structure during gene regulation. Ail have DNA- or chromatin- stimulated ATPase activity and many can alter the structure of chromatin; h owever, the means by which they do this have remained unclear. Here we desc ribe a novel activity for ATP-dependent chromatin remodeling activities, th e ability to generate unconstrained negative superhelical torsion in DNA an d chromatin. We find that the ability to distort DNA is shared by the yeast SWI/SNF complex, Xenopus Mi-2 complex, recombinant ISWI, and recombinant B RG1, suggesting that the generation of superhelical torsion represents a pr imary biomechanical activity shared by all Snf2-prelated ATPase motors. The generation of superhelical torque provides a potent means by which ATP-dep endent chromatin remodeling activities can manipulate chromatin structure.