Type
ArticleAuthors
Bosaeus, NiklasEl-Sagheer, Afaf H.
Brown, Tom
Smith, Steven B.
Akerman, Bjorn
Bustamante, Carlos
Norden, Bengt
Date
2012Permanent link to this record
http://hdl.handle.net/10754/671281
Metadata
Show full item recordAbstract
Mixed-sequence DNA molecules undergo mechanical overstretching by approximately 70% at 60 �pN. Since its initial discovery 15 �y ago, a debate has arisen as to whether the molecule adopts a new form [Cluzel P, et al. (1996) $^{Science} 271:792–794; Smith SB, Cui Y, Bustamante C (1996) $^{Science} 271:795 799], or simply denatures under tension [van Mameren J, et al. (2009) Proc Natl Acad Sci USA 106:18231–18236]. Here, we resolve this controversy by using optical tweezers to extend small 60�bp single DNA duplex molecules whose base content can be designed at will. We show that when AT content is high (70%), a force-induced denaturation of the DNA helix ensues at 62 �pN that is accompanied by an extension of the molecule of approximately 70%. By contrast, GC-rich sequences (60% GC) are found to undergo a reversible overstretching transition into a distinct form that is characterized by a 51% extension and that remains base-paired. For the first time, results proving the existence of a stretched basepaired form of DNA can be presented. The extension observed in the reversible transition coincides with that produced on DNA by binding of bacterial RecA and human Rad51, pointing to its possible relevance in homologous recombination.Citation
Bosaeus, N., El-Sagheer, A. H., Brown, T., Smith, S. B., Åkerman, B., Bustamante, C., & Nordén, B. (2012). Tension induces a base-paired overstretched DNA conformation. Proceedings of the National Academy of Sciences, 109(38), 15179–15184. doi:10.1073/pnas.1213172109Sponsors
This work was funded by grants to B.N. from the European Research Council and King Abdullah University of Science and Technology.Additional Links
http://www.pnas.org/lookup/doi/10.1073/pnas.1213172109ae974a485f413a2113503eed53cd6c53
10.1073/pnas.1213172109