The fact that 53BP1 accumulates adjacently to FANCD2 foci during S phase led us to speculate that its deficiency might exacerbate replication stress particularly in these cancer cells, mimicking the effect of DNA polymerase inhibition induced by aphidicolin treatments, which causes the accumulation of late replication intermediates (LRIs) and the formation of UFBs positive for FANCD2 foci10,11 (Supplementary Fig. 7a). Here, FANCD2 is linked to cancer.