E Left: cartoon of pICL indicating the SapI site that is blocked by the ICL. Right: DNA samples from pICL replication (performed in parallel with those shown in C and D) were cut with SapI, and repair efficiency was calculated as described (Knipscheer
et al,
2012). The background level of SapI-cleavable products in the Rev1-depleted reaction is due to contamination of pICL by un-cross-linked plasmid (Knipscheer
et al,
2009). The amount of SapI-cleavable products can vary between experiments due to differences in the amount of un-cross-linked plasmid and in the repair capacity of individual batches of extract.