Figure 6
Analysis of the symmetry of progressing bidirectional replication forks.
(A) Presentation of the concept of long fork/short fork ratios. The long fork/short fork ratio corresponds to the ratio of the longer IdU + CldU signal over the shorter IdU + CldU signal of bidirectional replication forks. A ratio >1 indicates fork asymmetry, while a ratio =1 indicates symmetry (see Materials & Methods). (B) Distribution of long fork/short fork ratios in MEF cells, T. brucei and three Leishmania species. Median (black bar) values are indicated below the distribution clouds. Statistically significant differences are indicated; p values were calculated using the two-tailed Mann-Whitney test. (C) Representative pairs of asymmetric replication forks from T. brucei. The forks were assembled from different microscope fields. Arrows indicates the lengths of the bidirectional forks analysed. Red tracks: IdU, green tracks: CldU, blue tracks: DNA. DNA counterstaining is not shown in the bottom panel. Scale bar: 50 kb. (D) Schematic presentation of the unidirectional replication forks that were analysed. Forks indicated by asterisks are counted as unidirectional forks and used in the calculation of percentage of unidirectional forks. In the top fibre, the left fork was not included for calculation as one cannot distinguish between a unidirectional fork and a fibre broken between the bidirectional forks. (E) Histograms showing the percentage of unidirectional replication forks over the total number of analysed forks in MEF cells, T. brucei and three Leishmania species. (F) Representative DNA fibres from T. brucei showing unidirectional forks. The fibres were assembled from different fields. Arrows indicate the direction of replication forks. Unidirectional forks indicated by asterisks were used for this analysis. Same color code and legend as in (C).
