IRE1 functions by detecting misfolded proteins through its luminal domain, leading to its oligomerization and activation. This activation triggers its kinase and endoribonuclease activities. The endoribonuclease activity of IRE1 is particularly important for splicing X-box binding protein 1 (XBP1) mRNA, which is a key transcription factor in the UPR. The spliced XBP1 mRNA is then translated into a potent transcription factor that induces the expression of genes involved in protein folding, ER-associated degradation (ERAD), and lipid biosynthesis.
