Ablating ARID1A leads to accumulation of DNA double-strand breaks (DSBs). In MDA-MB-231 cells transfected with ARID1A siRNA, followed by irradiation, the levels of DNA damage were evaluated with two approaches: Measurement of ɤH2AX levels by (A) Western blot analysis and (B) neutral comet assay. After MDA-MB-231 cells transfected with an empty vector or one that overexpresses ARID1A were irradiated, the levels of DNA damage were evaluated with two approaches: Measurement of ɤH2AX levels by Western blot analysis (C) and neutral comet assay (D). (E,F) MDA-MB-231 cells previously treated with HuR siRNA were transfected with an empty vector or a vector that expressed ARID1A to test the ability of ARID1A to reduce DNA DSBs in cells where HuR was downregulated. Error bars represent SEM (standard error of the mean), ** p ≤ 0.05; *** p ≤ 0.0001.