Fig. 1
From: Comparison and contrast of plant, yeast, and mammalian ER stress and UPR
A schematic illustration of the unfolded protein response in yeast. Under normal conditions, ER membrane-localized yeast IRE1 is bound to BiP at the N-terminal region located in the ER lumen, with the C-terminus facing into the cytosol. Upon the accumulation of unfolded proteins in the ER lumen, IRE1 is released from BiP and activated by autophosphorylation and dimerization. Activated IRE1 splices HAC1 mRNA and removes 253 nucleotides including stop codon. HAC1s ligated by tRNA ligase possesses a longer ORF than unspliced HAC1 mRNA (HAC1u). HAC1p is exported to the nucleus and binds with the UPRE region of UPR-responsive genes