Nucleic Acids Research Advance Access originally published online on February 26, 2009
Nucleic Acids Research 2009 37(7):2371-2380; doi:10.1093/nar/gkp104
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Nucleic Acids Research, 2009, Vol. 37, No. 7 2371-2380
© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
Asymmetric DNA requirements in Xer recombination activation by FtsK
1CNRS, Centre de Génétique Moléculaire, FRE 3144, 91198 Gif-sur-Yvette, 2Université Paris-Sud, 91405 Orsay, 3Université Pierre et Marie Curie, Paris 6, 4Laboratoire UMR8550 de Physique Statistique et Département de Biologie, Ecole Normale Supérieure and 5Institut Universitaire de France, 75005 Paris, France
*To whom correspondence should be addressed. Tel: +00 33 1 6982 3224; Fax: +00 33 1 6982 3160; Email: barre{at}cgm.cnrs-gif.fr
Received December 12, 2008. Revised February 4, 2009. Accepted February 4, 2009.
In bacteria with circular chromosomes, homologous recombination events can lead to the formation of chromosome dimers. In Escherichia coli, chromosome dimers are resolved by the addition of a crossover by two tyrosine recombinases, XerC and XerD, at a specific site on the chromosome, dif. Recombination depends on a direct contact between XerD and a cell division protein, FtsK, which functions as a hexameric double stranded DNA translocase. Here, we have investigated how the structure and composition of DNA interferes with Xer recombination activation by FtsK. XerC and XerD each cleave a specific strand on dif, the top and bottom strand, respectively. We found that the integrity and nature of eight bottom-strand nucleotides and three top-strand nucleotides immediately adjacent to the XerD-binding site of dif are crucial for recombination. These nucleotides are probably not implicated in FtsK translocation since FtsK could translocate on single stranded DNA in both the 5'–3' and 3'–5' orientation along a few nucleotides. We propose that they are required to stabilize FtsK in the vicinity of dif for recombination to occur because the FtsK–XerD interaction is too transient or too weak in itself to allow for XerD catalysis.