Effects of localized bending on DNA supercoiling.

The DNA double helix is straight only in the idealized case. In reality, it bends, twists and stretches in response to local base sequence and to specific interactions with proteins and other bound ligands. Naturally occurring bends appear to promote the assembly of nucleosomes, and in some cases can effectively replace regulatory DNA-binding proteins in vivo. Recently, a computational method known as 'finite element analysis', which is used routinely by engineers to analyse the stability of buildings and bridges, has been applied to the quantitative assessment of natural curvature in supercoiled DNA structures, providing new insight into the relationship between local, sequence-dependent features and the overall topology of these chains.