As described previously (Rutkevich et al., 2010 (link)), total RNA was isolated from cells using the RNeasy kit (Qiagen) and subjected to one-step reverse transcription PCR (Qiagen) using either human or mouse Xbp1 amplification primers: human, 5′-GGAGTTAAGACA­GCGCTTGG-3′ and 5′-GAGATGTTCTGGAGGGGTGA-3′; mouse, 5′-GGCCTTGTGGTTGAGAACCAGGAG-3′ and 5′-GAGT­CT­GA­TA­TCCTTTTGGGCATTC-3′. As a positive control, cells were incubated with 10 μg/ml tunicamycin overnight.