Fig. 4.

ATRX-dependent HR leads to the formation of IR-induced MUS81-dependent HR intermediates. (A) HeLa and U2OS cells were transfected twice on consecutive days with siCtrl or siMUS81+siGEN1, irradiated, and RPA- and/or BLM-positive UFBs were enumerated in EdU-negative late anaphase cells. Representative images of UFBs in MUS81- and GEN1-depleted HeLa and U2OS cells are shown. Knockdown was confirmed by immunoblotting. (B) HeLa and U2OS cells were irradiated with 2 Gy, prophase cells positive for the mitotic marker pH3 and negative for EdU were selected, and Z-stack images were captured and analyzed for MUS81 foci numbers and colocalization with γH2AX foci. All data show mean ± SEM (n = 3) and results from individual experiments, each derived from 40 (A) or 20 (B) cells, are indicated. **P < 0.01; ***P < 0.001; ns: not significant (two-tailed t test); NIR: nonirradiated.