Monitoring Double-Strand Break Repair of Trinucleotide Repeats Using a Yeast Fluorescent Reporter Assay.

Cells can repair a double-strand break (DSB) by homologous recombination if a homologous sequence is provided as a template. This can be achieved by classical gene conversion (with or without crossover) or by single-strand annealing (SSA) between two direct repeat sequences flanking the DSB. To initiate SSA, single-stranded regions are needed adjacent to the break, extending up to the direct repeats in such a way that complementary strands can anneal to each other to repair the DSB. In the present protocol, we describe a GFP reporter assay in Saccharomyces cerevisiae allowing for the quantification of nuclease efficacy at inducing a DSB, by monitoring the reconstitution of a functional GFP gene whose expression can be rapidly quantified by flow cytometry.