ERE-luciferase Assays

ERE-luciferase assay was carried as described (Cui et al., 2012). Briefly, MMTV-HER2, MMTV-HER2/MMTV-MED1 and BT474 cells were infected with scramble control, sh-Jab1 or ShMED1 lentivirus that specifically knockdown Jab1 or MED1. Cells were then cultured in 24-well plates containing phenol-red-free DMEM medium supplemented with 5% charcoal-stripped FBS for 48 hours. ERE-TK-Luc reporter vector and pRL-CMV control plasmid were transfected using Lipofectamine 2000 (Invitrogen). Following the transfection, the cells were treated with estrogen or vehicle for 24 hours before harvest. A dual luciferase reporter assay system (Promega) was used to measure the luciferase activity.