ATF-6 (Activating transcription factor 6) is a transcription factor that activates target genes for the unfolded protein response (UPR) during endoplasmic reticulum (ER) stress. ATF-6 functions as an ER stress sensor/transducer, and following ER stress-induced proteolysis, it functions as a nuclear transcription factor via a cis-acting ER stress response element (ERSE) that is present in the promoters of genes encoding ER chaperones. ATF-6 protein has been identified as a survival factor for quiescent but not proliferative squamous carcinoma cells. There have been conflicting reports about the association of polymorphisms in ATF-6 with diabetes in different populations, but another polymorphism has been associated with increased plasma cholesterol levels. ATF-6 is also thought to be a potential therapeutic target for cystic fibrosis.