Transcription factor that acts during endoplasmic reticulum stress by activating unfolded protein response target genes. Specifically involved in ER-stress response in astrocytes in the central nervous system (By similartity). May play a role in gliosis. In vitro, binds to box-B element, cAMP response element (CRE) and CRE-like sequences, and activates transcription through box-B element but not through CRE (By similarity).