Environmental influences on DNA curvature.

DNA curvature plays an important role in many biological processes. To study environmental influences on DNA curvature we compared the anomalous migration on polyacrylamide gels of ligation ladders of 11 specifically-designed oligonucleotides. At low temperatures (25 degrees C and below) most of the sequences exhibited a degree of anomalous migration. Increased temperature had a significant effect on the anomalous migration (curvature) of some sequences but limited effects on others; at 50 degrees C only 1 sequence migrated anomalously. Mg2+ had a strong influence on the migration of certain sequences, whilst spermine enhanced the anomalous migration of a different set of sequences. Sequences with a GGC motif exhibited greater curvature than predicted by the presently-used angles for the nearest-neighbour wedge model and are especially sensitive to Mg2+. The data have implications for models for DNA curvature and for environmentally-sensitive DNA conformations in the regulation of gene expression.