The capacity of DON to induce rRNA cleavage in RAW 264.7 macrophages was assessed by denaturing gel electrophoresis (Fig. 1A) and capillary electrophoresis (Figs. 1B and 1C). Distinct 18S and 28S rRNA bands were evident in both control and DON-treated RAW 264.7 cells, whereas over five additional rRNA fragment bands were detected in DON-treated cells. Based on its high resolution and reproducibility as compared with conventional electrophoresis, capillary electrophoresis was employed to monitor cleavage in subsequent experiments. When the kinetics of the response were measured, DON at 1000 ng/ml was found to cause rRNA cleavage as early as 2 h that was very robust by 6 h (Figure 2A ). Cleavage at 6 h was concentration dependent with 200 ng/ml of DON evoking modest rRNA cleavage as compared with more marked rRNA cleavage induced by 1000 ng/ml ( Figure 2B ). Based on these findings, incubation with DON at 1000 ng/ml for 6 h was uniformly employed for subsequent mechanistic studies.