RAD18 regulates FANCD2 foci formation. (A) RAD18-deficient and wild-type cells were plated into chamber slides and treated over several time points with 500mM MMC. Staining for FANCD2, followed by analysis by immunofluorescence microscopy, shows a delay in FANCD2 foci formation for nearly 8 hours in RAD18-deficient cells compared with wild-type cells. (B) Approximately 200 cells from each condition in panel A were assessed for the presence of FANCD2 foci. Graph represents the percentage of cells positive for FANCD2 foci, with cells containing more than 5 foci considered positive.