Fast dynamics of supercoiled DNA revealed by single-molecule experiments

• DOI: 10.1073/pnas.0700333104
• Publication Date: 2007-07-11T02:18:23Z
• Authors: Aurélien Crut; Daniel A. Koster; Ralf Seidel; Chris H. Wiggins; Nynke H. Dekker
• Keywords: 0301 basic medicine; 0303 health sciences; 03 medical and health sciences; Rotation; DNA, Superhelical; Biophysics; [SDV.BBM.BP] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics; Deoxyribonuclease I; Nucleic Acid Conformation; Biomechanics; 530

The dynamics of supercoiled DNA play an important role in various cellular processes such as transcription and replication that involve DNA supercoiling. We present experiments that enhance our understanding of these dynamics by measuring the intrinsic response of single DNA molecules to sudden changes in tension or torsion. The observed dynamics can be accurately described by quasistatic models, independent of the degree of supercoiling initially present in the molecules. In particular, the dynamics are not affected by the continuous removal of the plectonemes. These results set an upper bound on the hydrodynamic drag opposing plectoneme removal, and thus provide a quantitative baseline for the dynamics of bare DNA.