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Book of Abstracts: Albany 2005

category image Volume 22
No. 6
June 2005

DNA Flexibility

Classic experimental and theoretical analyses led to a unified view of DNA as a stiff polymer, characterized by a bending persistence length (a lengthscale for resistance to bending), P, ∼150 bp. However, in vivo, sharply bent DNA occurs ubiquitously and plays important roles in prokaryotic gene regulatory complexes, eukaryotic nucleosomes, and viruses. We used the method of ligase catalyzed DNA cyclization to investigate the ability of DNA to sharply bend. Remarkably, DNAs of length only 94 bp or less spontaneously bend into circles, and they do so with a probability that exceeds the predictions of classic theories by orders of magnitude (1). Subsequent studies establish that the twistability of sharply looped DNAs also greatly exceeds the predictions of classic theories (2). These results can only be understood by greatly enhanced DNA flexibility, not by permanent bends. Our results provide striking support for new theories of DNA mechanics (3, 4), and they establish DNA as an active participant in the formation and function of looped regulatory complexes in vivo.

References and Footnotes
  1. Cloutier, T. E. and Widom, J. Mol. Cell 14, 355?362 (2004).
  2. Cloutier, T. E. and Widom, J. Proc. Natl. Acad. Sci. (USA) Epub Feb. 17 (2005).
  3. Yan, J. and Marko, J. F. Phys. Rev. Lett. 93, 108108 (2004).
  4. Wiggins, P. A., Phillips, R., and Nelson, P. C. Phys. Rev. E 71, 021909 (2005).

J. Widom

Department of Biochemistry
Molecular Biology and Cell Biology
Northwestern University
Evanston, IL

Phone: 1-847-467-1887
Fax: 1-847-467-6489
Email: j-widom@northwestern.edu