Homologous recombination repair assay

GFP-Pem1 reporter and HA-I-Sce I expression vectors were kindly provided by Dr Vera Gorbunova (University of Rochester, Rochester, NY, USA). GFP-Pem1 cassettes were stably integrated into the desired cell lines. The resulting cell lines were transiently co-transfected with HA-I-Sce I expression and orange fluorescence protein expression vectors (Life Technologies, Carlsbad, CA, USA), cells were harvest at various time points post I-Sce I induction, GFP-positive cells were detected by fluorescence-assisted cell sorting (BD Biosciences, San Jose, CA, USA) and the percentage of GFP cells was normalized to orange fluorescence protein expression cells for transfection efficiency control. Expression of GFP was also monitored and recorded under fluorescence microscopy (Nikon, Eclipse Ti-S, Minato, Tokyo, Japan) at various time points.