To investigate the RIDD pathway, we took an unbiased, microarray-based approach. We induced ER stress in the Ire1 / and hIre1 R cells with DTT, purified total RNA from treated and untreated cells, amplified and labeled these samples, and hybridized them to whole-genome MEEBOChip arrays. As expected, treatment of our hIre1 R cells with DTT led to the induction of classical UPR targets to levels comparable with that seen by others in wild-type cells ( Fig. S1 ; Lee et al., 2003) .