Figure 1.

RTA and ricin inhibit tunicamycin (Tm)-induced XBP1 splicing in MAC-T cells. (A) Cells were serum-starved for 2 h prior to treatment ± RTA (0.1 or 1.0 µg/mL) and ± Tm (2.5 µg/mL) for 4 h. Total RNA was analyzed by RT-PCR as described in Materials and Methods. U = unspliced XBP1, S = spliced XBP1; (B) qRT-PCR analysis of XBP1 expression. Data were corrected for cyclophilin and presented relative to levels in cells treated with Tm alone. Data were analyzed by one-way ANOVA with Bonferroni’s Multiple Comparison post-hoc test. ** P < 0.001 and * P < 0.01 indicates different from Tm-treated cells. Bars represent mean ± S.E. of four experiments; (C) Cells were treated with 0.1 µg/mL of RTA (A), 1 µg/mL of RTB (B) or 0.01 µg/mL of ricin holotoxin (R) ± 2.5 µg/mL Tm for 4 h and total RNA was analyze by RT-PCR; (D) Total protein synthesis was determined by [³⁵S]methionine incorporation. MAC-T cells were treated with 0.1 µg/mL RTA, 1 µg/mL RTB or 0.01 µg/mL ricin holotoxin for 4 h. Bars represent mean ± SE of 3 experiments.