Fig. 4.

An increased number of fork fusion events caused by UV-induced origin-independent synthesis leads to uncontrolled DNA amplification. a UV-irradiation leads to a drastic and often unbalanced increase in origin (red) and terminus (green) foci in the absence of oriC firing (combined phase contrast and fluorescence images are shown). Cells were grown at permissive temperature prior to UV treatment and shifted to 42 °C directly after irradiation. The strain used was RCe198 (recG dnaA46). b, c Schematic for the pathological cascade triggered by converging replication forks in the absence of RecG. UV-induced damage is indicated by red triangles. Over-replication by fork fusion events (positions of fusion events indicated by grey arrows) is highlighted in red, synthesis from origin firing in blue