Section 32
Chapter 31,718

Homologous recombination in real time: DNA strand exchange by RecA

Van der Heijden, T.; Modesti, M.; Hage, S.; Kanaar, R.; Wyman, C.; Dekker, C.

Molecular Cell 30(4): 530-538


ISSN/ISBN: 1097-4164
PMID: 18498754
DOI: 10.1016/j.molcel.2008.03.010
Accession: 031717256

Homologous recombination, the exchange of strands between different DNA molecules, is essential for proper maintenance and accurate duplication of the genome. Using magnetic tweezers, we monitor RecA-driven homologous recombination of individual DNA molecules in real time. We resolve several key aspects of DNA structure during and after strand exchange. Changes in DNA length and twist yield helical parameters for the protein-bound three-stranded structure in conditions in which ATP was not hydrolyzed. When strand exchange was completed under ATP hydrolysis conditions that allow protein dissociation, a "D wrap" structure formed. During homologous recombination, strand invasion at one end and RecA dissociation at the other end occurred at the same rate, and our single-molecule analysis indicated that a region of only about 80 bp is actively involved in the synapsis at any time during the entire reaction involving a long ( approximately 1 kb) region of homology.

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