Figure 1: ARID1A regulates XBP1 expression.

(A) Experimental strategy used to identify ARID1A-regulated genes under 5μg/mL tunicamycin treatment for 4 hours in ARID1A wildtype control and ARID1A knockout RMG1 OCCC cells. Ingenuity Pathway Analysis revealed that the ER stress response is among the top 10 pathways enriched in ARID1A direct target genes upregulated by ARID1A knockout in response to tunicamycin treatment condition. (B) Control and ARID1A knockout RMG1 cells were treated with 5 μg/mL tunicamycin or vehicle controls for 4 hours. Expression of both unspliced XBP1 (XBP1u) and spliced XBP1 (XBP1s) was determined by RT-qPCR analysis. n = 3 biologically independent experiments. (C) Controls and ARID1A knockout RMG1 cells were treated with 5 μg/mL tunicamycin or vehicle controls for 4 hours. Expression of ARID1A, spliced XBP1 and a loading control β-actin was determined by immunoblot. (D) Control and ARID1A knockout RMG1 cells were treated with 20 μM MG-132 or vehicle controls for 4 hours. Expression of both unspliced and spliced XBP1 was determined by immunoblot and β-actin expression was used as a loading control. Please note that unspliced XBP1 is stabilized by MG-132 to make it detectable. (E) Relative expression of XBP1 in the ARID1A wildtype (n=283) and mutated (n=201) uterine corpus endometrial carcinoma cases in the TCGA database. P values were calculated using two-tailed Student’s t-test except by Fisher Exact test in A. Error bars represent mean with SD.