Asymmetric lateral distribution of unshielded phosphate groups in nucleosomal DNA and its role in DNA bending.

We suggest that an asymmetric charge neutralization of DNA phosphate groups produces part of the driving force for nucleosome folding. In nucleosome core particle DNA, many of the phosphate groups are neutralized by histones, and a lateral alignment of these histones along the core DNA has been demonstrated [Mirzabekov A. D., Shick, V. V., Belyavsky, A. V. & Bavykin, S. G. (1978) Proc. Natl. Acad. Sci. USA 75, 4184--4189]. Histones appear to shield DNA phosphatases asymmetrically at one side of the surface of the DNA double helix along all its length inside the core. The external side of the DNA helix remains unneutralized. The electrostatic repulsion between negatively charged unneutralized phosphates may fold the nucleosomal DNA towards the side occupied by histones.