FIG 9.

Toxin-induced CHOP mRNA induction. U937 cells, HBMECs, or HCT-8 cells were treated with 1 μg/ml SubAB, SubA_A272B, or Stx2 or were left untreated (control) for 4 h or 24 h. Total RNA was extracted from the cells, and CHOP mRNA was quantitated by real-time RT-PCR using primers specific for CHOP (Table 1), as described in Materials and Methods. The results are expressed as fold increases in concentrations of mRNA relative to levels in control cells. The data are means and SEM from 3 samples. ***, P < 0.001; **, P < 0.01; *, P < 0.05 relative to control cells (Student's unpaired, two-tailed t test).