FIG 3.

XBP1(S) regulates the RelA protein expression level. (A) Representation of the XBP1 mutant constructs used in this study. (B) Antiestrogen-sensitive breast MCF-7 cells were transfected with various forms of XBP1 mutants together with pGL3-Basic or pGL3-NF-κB-luc luciferase constructs. At 24 h posttransfection, cells were lysed and luciferase activity was measured. (C) At 48 h after transfection, cell lysates were collected, and the levels of RelA and XBP1 (Flag tag) were examined by Western blot analysis; β-actin was used as the loading control. Data represent the means from at least three independent experiments. **, P < 0.01. For Western blots, representative images from three independent experiments are shown.