Fig. 5.

Degradation of the DNA synthesized before UV irradiation in Rad51-depleted cells is prevented by Mre11 but not by PARP inhibition. (A) Schematic of the DNA fiber-labeling experiment shown in B and C. Samples were collected at the indicated time after UV irradiation (2.5–60 min). CldU track length quantification in bicolored fibers of untreated (B) and UV (20 J/m²)-irradiated (C) U2OS cells depleted from Rad51 (siRNA sequence 1). The dotted lines correspond to the average CldU track length of untreated samples. The black line represents the average shortening of the CldU track in UV-irradiated, Rad51-depleted samples. (D) Schematic of the DNA fiber-labeling experiment with mirin pretreatment. Distribution frequency of the CldU track length in unirradiated (E) or UV (20 J/m²)-irradiated (F) samples transfected with control or Rad51 siRNA (sequence 1) and treated with mirin or DMSO when indicated. In F, the difference in CldU track length between Rad51-depleted samples with or without mirin treatment is indicated. (G) Extent of Mre11 down-regulation by siRNA. (H) CldU track length frequency distribution of control, Rad51 (sequence 1)-depleted, and Mre11 (sequence 1)-depleted samples. (I) Distribution frequency of CldU track length of Rad51-depleted samples treated with mirin and Mre11 siRNA. (J) Schematic of the DNA fiber-labeling experiment performed in K. (K) CldU track length frequency distribution of Rad51-depleted (sequence 1) samples treated with mirin and olaparib. In D–K, the solid and dotted lines represent the Gaussian distribution of the mean and SD for each condition. Two (B, C, and G–K) or three (E and F) independent experiments were analyzed, obtaining similar results.