(A) The repair of the I-PpoI sites is by NHEJ not HR. At the top is shown western-blotting of the RAD51 and KU80 knockdowns; below is shown the kinetics of generation and repair of the DSBs at SLCO5A1 I-PpoI sites in scramble shRNA knockdown (left), sh-hKU80 (center) and sh-hRAD51 (right) knockdown cells respectively. At the bottom is shown quantitation of the proportion of input DNA and H3 occupancy from ChIP analysis at 200 bps from the I-PpoI site within the SLCO5A1 gene in the scrambled shRNA knockdown (left panels), the KU80 knockdown (center panels) and RAD51 knockdown (right panels) knockdown cells. Shown is the average +/- SEM from three independent experiments. Asterisks indicate significant changes from the scramble shRNA knockdown, p = 0.005, as determined by the Student’s t-test. (B) Inhibition of MRE11 has no effect on repair or chromatin disassembly / reassembly around the I-PpoI site. The panels on the left are experiments performed with cells grown with the MRE11 exonuclease inhibitor PFM39, while those on the right were from experiments performed with cells grown with the MRE11 endonuclease inhibitor PFM03. At the top is shown the kinetics of generation and repair of the DBSs at SLCO5A1 I-PpoI sites; below is the quantitation of proportion of input DNA and H3 occupancy from ChIP analysis at 200 and 500 bps from the I-PpoI site within the SLCO5A1 gene.