Figure 2.

ATR binds DNA. HEK293T cells were transfected with vector expressing full-length ATR (ATR-F), its N-terminal (ATR-N), middle region (ATR-M), and C-terminal (ATR-C) fragments or the nontransfected (Mock) cells were lysed and the tagged proteins were purified by binding to FLAG-agarose beads. The beads were then incubated with radiolabeled DNA substrate as described in Materials and Methods. After exhaustive washing, the beads were loaded onto a 10% SDS/PAGE, and the bound proteins were visualized by silver staining (Top), and the levels of ATR-bound substrates were visualized by autoradiography (Middle). Bottom shows the quantitative analysis of data from Middle.