The accumulation of unfolded proteins within the endoplasmic recticulum (ER) of yeast and mammalian cells activates the unfolded protein response (UPR) pathway and leads to the transcription of ER-specific genes involved in protein folding. One of the players in UPR, IRE1, was first identified in Saccharomyces cerevisiae as a transmembrane serine/threonine kinase. Recently, IRE1α was shown to mediate the rapid degradation of certain mRNAs based on the ER-localization and primary sequences of their encoded proteins, suggesting a novel mechanism in UPR.
