FtsK-dependent Xer recombination at <i>dif</i> as a tool to monitor sister chromatid contacts.

<p><b>A.</b> Scheme of the different site-specific recombination products that can be obtained when intramolecular recombination is impeded. <b>B.</b> Schematic representation of the 55 bp <i>dif</i>-recombination cassettes and the Xer recombination control set up. The orange arrow represents the <i>lacZ</i> gene disrupted by the two <i>dif</i> sites (red triangle). Expression of the <i>xerC</i> gene (green arrow) is under the positive control of the arabinose promoter, P_BAD, and the negative control of the <i>E. coli lacZ</i> promoter, P_Lac. <b>C.</b><i>dif1</i> and <i>dif2</i> sequence divergence. The DNA binding arms of XerC and XerD are shown. Bases that differ in <i>dif1</i> and <i>dif2</i> are shown in red and blue, respectively. <b>D.</b> Reconstitution of a functional <i>lacZ</i> gene depends on XerC and FtsK. Results from at least three independent experiments. <b>E.</b> Recombination between <i>dif</i> sites harboured on different chromosomes does not perturb the SCC detection. Schematic representation of the genome of a strain harbouring <i>lac2dif1</i> on chrII. No intrachromosomal recombination can occur between <i>lac2dif1</i> and <i>dif2</i> because of sequence divergence. The influence of chrI <i>dif1</i> on chrII <i>lac2dif1</i> recombination was tested by comparing results obtained in a strain in which <i>dif1</i> was deleted. Results from at least three independent experiments. Legends as in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004557#pgen-1004557-g001" target="_blank">Figure 1A</a>. Red triangle: <i>dif1</i>; blue triangle: <i>dif2</i>.