Accumulation of unfolded proteins within the endoplasmic reticulum (ER) triggers a highly conserved stress response mechanism termed the unfolded protein response (UPR). The UPR is a complex series of signaling pathways controlled by ER localized transmembrane receptors, PERK, ATF6 and IRE1真. Following activation IRE1真 splices XBP-1 mRNA facilitating the formation of a potent transcription factor, spliced XBP-1. The BCL-2 family members, BAX and BAK, in addition to the mitochondrion also localize to the ER and have been demonstrated to directly interact with IRE1真 promoting its activity. In this study we show that in addition to BAX and BAK, the anti-apoptotic BCL-2 protein can regulate IRE1真 activity. Enhanced splicing of XBP-1 was observed in BCL-2 overexpressing cells implicating BCL-2 in the complex regulation of IRE1真 activity..