Figure 10.

Model for ER stress-induced processing of ATF6. ATF6 is constitutively synthesized as a precursor protein (p90ATF6) that anchors in the ER membrane through the single transmembrane domain near the center of the molecule. ER stress-induced proteolysis of p90ATF6 releases the N-terminal fragment (p50ATF6) containing bZIP, although the precise cleavage site is unknown. p50ATF6 translocates into the nucleus and interacts with the general transcription factor NF-Y to form a complex designated here as ER stress response factor (ERSF). ERSF activates transcription through ERSE (CCAAT-N9-CCACG) present in the promoter regions of mammalian UPR target genes.