Figure 5

Analysis of sister replication-fork progression in SN38 sensitive and resistant HCT116 cells : A) HCT116-s (SN38 sensitive) and HCT116-SN6, -A2, -SN50, -C8 and -G7 (SN38 resistant) cells were pulse-labeled with IdU and CldU and processed for DNA combing. Replication forks progress bidirectionally from the origin and incorporate the analogues. A replication fork arrest is detected as an asymmetrical replication signal. Representative pairs of sister replication forks were assembled from different fields and were centered. Red: IdU and Green: CldU. B) Scatter plot of the distances covered by right-moving and left-moving sister forks during CldU pulse-labeling in HCT116-s treated or not with SN38 (each point represents one measurement). The central areas delimited with lines contain sister forks with less than 25% length difference. The difference of asymmetry is significant p < 0.0001 (Mann Whitney test). C) Box plot of fork asymmetry. Fork asymmetry is expressed as the ratio between the longest and the shortest distance covered by each pair of sister replication forks during CldU pulse-labeling.