Abstract
We present a method of detecting sequence defects by supercoiling DNA with magnetic tweezers. The method is sensitive to a single mismatched base pair in a DNA sequence of several thousand base pairs. We systematically compare DNA molecules with 0 to 16 adjacent mismatches at 1 M monovalent salt and 3.6 pN force and show that under these conditions, a single plectoneme forms and is stably pinned at the defect. We use these measurements to estimate the energy and degree of end-loop kinking at defects. From this, we calculate the relative probability of plectoneme pinning at the mismatch under physiologically relevant conditions. Based on this estimate, we propose that DNA supercoiling could contribute to mismatch and damage sensing in vivo.
- Received 26 April 2017
DOI:https://doi.org/10.1103/PhysRevLett.119.147801
© 2017 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
Twisting DNA Locates its Defects
Published 3 October 2017
Single base-pair mismatches in DNA can be pinpointed by twisting the molecule until it buckles.
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