Figure 4.

Activation of UPR by chimeric tRNAs. (a) Kinetics of BIP and CHOP with persistent ER stress in vitro. Semi-quantitative RT–PCR (SQ-RT–PCR) was performed to check BIP and CHOP mRNA levels at the indicated different time points. (b) Activation of Xbp-1 and ATF6, and phosphorylation of eIF2α in cells expressing chimeric tRNAs. The presence of full-length (u) and spliced (s) Xbp-1 forms was checked by PCR. (c) BiP transcription induction in vivo. The expression levels of BiP (black staining) induced by each chimeric tRNA in a chicken embryo are proportional to the decrease in wt GFP fluorescence caused by the same tRNAs. Images are representative of three independent experiments 6 h post-electroporation (PE). GFP signal indicates the co-electroporated cells.