Revealing Sister Chromatid Interactions with the loxP/Cre Recombination Assay.

Sister chromatid cohesion is a transient state during replication in bacteria. It has been recently demonstrated that the extent of contact between cohesive sisters during the cell cycle is dependent on topoisomerase IV activity, suggesting that topological links hold sister chromatids together. In the present protocol, we describe a simple method to quantify the frequency of the contacts between two cohesive sister chromatids. This method relies on a site specific recombination assay between loxP sites upon Cre induction.