Figure 1. Schematic representation of the IRE1α-XBP1u pathway mediating UPR.

Interaction of the XBP1u nascent chain with the ribosomal exit tunnel leads to translational pausing, resulting in SRP recruitment to the RNC, followed by targeting to Sec61 on the ER membrane. IRE1α localized near Sec61 during ER stress can splice XBP1u mRNA to XBP1s mRNA, which acts as transcription factor in alleviating ER stress.