FIGURE 2.

BCL6 attenuates DNA damage response in fibroblasts in an ATR-dependent manner. A, WI-38 fibroblasts were transduced as indicated, harvested before and after 5 Gy γ-radiation, and submitted to FACS to detect the percentage of cells staining for Ser¹³⁹ phosphorylation of H2A.X. B, immunoblots were performed in BCL6-transduced WI-38 cells transfected with either pCDNA or pCDNA-FLAG-ATR. The top immunoblot was performed with FLAG antibody (because ATR is FLAG tagged) and the bottom, a Western blot with ATR antibody. The data confirm that ATR was expressed in ATR-transfected cells. C, repair of DSBs was detected in transduced WI-38 cells at the indicated time points before and after 5 Gy γ-radiation. Quantitative Comet assays were performed in quadruplicate and the mean ± S.D. calculated. The y axis represents the abundance of DNA double strand breaks in arbitrary (Olive tail moment) units. D, representative photomicrographs of single cells, stained with ethidium bromide from the Comet assay experiment of panel B. E, WI-38 cells were transduced as indicated and ATR transfected 24 h later. The percentage of dead cells were evaluated by acridine orange/ethidium bromide staining 24 h after 5 Gyγ-radiation (γ-RT; +) or after no radiation (-). Ctrl refers to untransduced WI-38 cells.