Homologous Pairing in Stretched Supercoiled DNA

By using elastic measurements on single DNA molecules, we show that stretching a negatively supercoiled DNA activates homologous pairing in physiological conditions. These experiments indicate that a stretched unwound DNA locally denatures to alleviate the force-driven increase in torsional stress....

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1998-09, Vol.95 (18), p.10579-10583
Main Authors: Strick, T. R., Croquette, V., Bensimon, D.
Format: Article
Language:English
Subjects:
Base Composition
Biochemistry
Biological Sciences
Chemical bases
Datasets
Deoxyribonucleic acid
DNA
DNA Probes
DNA, Superhelical - genetics
Molecular probes
Molecular structure
Molecules
Nucleic Acid Hybridization
Single stranded DNA
Topology
Torque
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Summary:By using elastic measurements on single DNA molecules, we show that stretching a negatively supercoiled DNA activates homologous pairing in physiological conditions. These experiments indicate that a stretched unwound DNA locally denatures to alleviate the force-driven increase in torsional stress. This is detected by hybridization with 1 kb of homologous single-stranded DNA probes. The stretching force involved (≈ 2 pN) is small compared with those typically developed by molecular motors, suggesting that this process may be relevant to DNA processing in vivo. We used this technique to monitor the progressive denaturation of DNA as it is unwound and found that distinct, stable denaturation bubbles formed, beginning in A+T-rich regions.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.95.18.10579