Insights Into Sequence Dependent Effects on DNA Elasticity Using Single Molecule Techniques

The mechanical properties of DNA play an important role in regulating gene expression within a cell. Sequence does not only code, but also affects structural properties of the DNA. These variations can change the intrinsic curvature and the stiffness of the DNA. To study the effect of sequence on elasticity, it must be decoupled from curvature effects. For this aim, we designed two DNA constructs with similar curvature but different sequences and measured their elasticity in single-molecule stretching experiments with optical tweezers. We report substantial differences in their persistence length. We complement these experiments with studies on the effect of these differences in elasticity on protein-mediated DNA looping as a means of transcriptional control, using the Lac repressor as a model system.