Binding of ER stress sensors XBP1 and ATF-6α to the TGFB1 promoter regulates its expression. DNA-binding affinity of ATF6α (Panel A) and XBP1 (Panel B) for the TGFB1 promoter was increased in SEMF isolated from the affected fibrostenotic ileum compared with normal ileum in the same patient. Chromatin immunoprecipitation using genomic DNA extracted from SEMF was isolated from the normal and affected ileum in 5 patients with fibrostenotic Crohn’s disease. C, The transcriptional regulation of TGFB1 gene expression by ATF-6α or XBP1 was measured by TGFB1 luciferase reporter assay. Normal SEMFs were cotransfected with siRNA ATF-6α or XBP1 or control scramble siRNA and TGFB1 luciferase reporter for 24 hours, then further incubated with tunicamycin (5 µg/mL) for 16 hours (n = 3). Results are expressed as mean ± SEM of 5 experiments using different patient samples.*Denotes P < 0.05 for normal vs affected ileum, or vehicle vs tunicamycin (TM) treatment.