Figure 4.

H4K20me2 levels control DNA repair pathway choice between NHEJ and HR. a) Schematic representation of experimental design. U2OS cells were synchronized with a double thymidine block and SETD8ΔPIP overexpression was induced for 16 h before the release in S-phase by incubation with 0.1 µg/ml Doxycycline. Cells were irradiated after 3 h from the release and, after 4 h recovery, co-stained for 53BP1 and BRCA1. b) Quantification of 53BP1 and BRCA1 foci in the experiment described in a). A 2 tailed t-test was run to compare cells treated either with buffer or 0.1 µg/ml doxycycline for both 53BP1 and BRCA1 foci with resulting p values < 0.0001. c) 2 representative cells for each condition, i.e. no doxycycline and 16 h incubation with 0.1 µg/ml doxycycline. White arrows in Cell 2 incubated with doxycycline indicate co-localization between big 53BP1 foci and small BRCA1 foci.