FIG 4.

DDX1 depletion has little effect on end resection. (A) Control and DDX1-depleted U2OS cells were microirradiated. Cells were immunostained with anti-γ-H2AX, anti-cyclin A, and anti-CtIP antibodies at 1 h postirradiation. Note that under these conditions, CtIP recruitment occurs in S/G₂-phase cells (indicated by positive nuclear staining of cyclin A, shown by arrows) but not in G₁-phase cells (negative nuclear cyclin A staining, shown by arrowheads). (B) Percentage of γ-H2AX stripes with CtIP recruitment in control and DDX1 knockdown cells treated as described for panel A. (C) Control and DDX1-depleted U2OS cells were treated with 2 Gy IR and immunostained with anti-γ-H2AX and anti-pEXO1 antibodies at 1 h post-IR. (D) Percentage of cells containing pEXO1 foci and number of foci per individual cell at 1 h (left) or 3 h (right) post-IR. P values were calculated using the two-sided Student t test for panel B and the chi-square test with Yates' correction for panel D. Scale bars, 20 μm; error bars, SEM; n = 3.