Function
Isoform 2: Functions as a stress-inducible potent transcriptional activator during endoplasmic reticulum (ER) stress by inducing unfolded protein response (UPR) target genes via binding to the UPR element (UPRE). Up-regulates target genes encoding ER chaperones and ER-associated degradation (ERAD) components to enhance the capacity of productive folding and degradation mechanism, respectively, in order to maintain the homeostasis of the ER under ER stress (PubMed:11850408, PubMed:14559994). Plays a role in the production of immunoglobulins and interleukin-6 in the presence of stimuli required for plasma cell differentiation, and promotes as well membrane phospholipid biosynthesis necessary for ER expansion (PubMed:12612580, PubMed:17213183). Contributes to the VEGF-induced endothelial cell (EC) growth and proliferation in a Akt/GSK-dependent and/or -independent signaling pathway, respectively, leading to beta-catenin nuclear translocation and E2F2 gene expression. Promotes umbilical vein EC apoptosis and atherosclerotisis development in a caspase-dependent signaling pathway, and contributes to VEGF-induced EC proliferation and angiogenesis in adult tissues under ischemic conditions. Involved in the regulation of endostatin-induced autophagy in EC through BECN1 transcriptional activation. Plays a role as an oncogene by promoting tumor progression: stimulates zinc finger protein SNAI1 transcription to induce epithelial-to-mesenchymal (EMT) transition, cell migration and invasion of breast cancer cells (By similarity). Involved in adipocyte differentiation by regulating lipogenic gene expression during lactation (PubMed:23623498, PubMed:25223794). Plays a role in the survival of both dopaminergic neurons of the substantia nigra pars compacta (SNpc), by maintaining protein homeostasis and of myeloma cells (PubMed:12902539, PubMed:24753614). Increases insulin sensitivity in the liver as a response to a high carbohydrate diet, resulting in improved glucose tolerance (PubMed:20348926). Improves also glucose homeostasis in an ER stress- and/or insulin-independent manner through both binding and proteasome-induced degradation of the transcription factor FOXO1, hence resulting in suppression of gluconeogenic genes expression and in a reduction of blood glucose levels (PubMed:21317886). Controls the induction of de novo fatty acid synthesis in hepatocytes by regulating the expression of a subset of lipogenic genes in an ER stress- and UPR-independent manner (PubMed:18556558). Binds to the 5'-CCACG-3' motif in the PPARG promoter (PubMed:25223794). Associates preferentially to the HDAC3 gene promoter region in a disturbed flow-dependent manner. Binds to the BECN1 gene promoter region. Binds to the CDH5/VE-cadherin gene promoter region. Binds to the ER stress response element (ERSE) upon ER stress (By similarity).