Acts as a negative regulator of the endoplasmic reticulum stress response or unfolded protein response (UPR). Represses the transcriptional activity of CREB3 during the UPR. Recruits CREB3 into nuclear foci (By similarity). Interacts (via leucine-zipper domain) with CREB3 (via leucine-zipper domain); the interaction promotes CREB3 degradation. Colocalizes with CREB3 in nuclear foci. Highly expressed in intestin, testis, heart and kidney, weakly in brain adipose, colon, liver, lung and skeletal. Probably degraded by the proteasome. Belongs to the bZIP family. CREBRF subfamily.