Expression of mutant NE induces XBP1 splicing in U937 cells. U937 cells were transiently transfected with vector alone (GFP), wild-type (WT), or mutant NE cDNAs, and 12 hours later GFP + cells were sorted by flow cytometry. As controls, parent U937 cells (P) and cells treated with tunicamycin (TM) also were analyzed. (A) Representative gel showing spliced (S) and unspliced (US) XBP1 bands. (B) The percentage of spliced XBP1 is shown. Data represent the mean (± SD) of 5 independent experiments. *P < .05 compared with WT-transfected cells.