Heterologous-expression of dRif1 in HeLa cells interferes with the 53BP1- foci formation upon DNA damage. HeLa cells were transfected with full length dRif1 with a N-terminal 3XFLAG tag. Cells were either mock treated (row 1,3) or with 2 mM HU (row 2) or 50 μg/ml of bleomycin (row 4) for 4 hrs, fixed and stained for dRif1(red) and 53BP1 (green). DAPI (blue) was used to mark the nuclei. (Scale bar, 10 μm).