Strongly activates transcription when bound to HCFC1. Suppresses the expression of HSV proteins in cells infected with the virus in a HCFC1-dependent manner. Also suppresses the HCFC1-dependent transcriptional activation by CREB3 and reduces the amount of CREB3 in the cell. Able to down-regulate expression of some cellular genes in CREBZF-expressing cells (By similarity). Interacts with HCFC1; the interaction inhibits CREB3 transcriptional activity. Interacts with CREB3; the interaction occurs only in combination with HCFC1. Colocalizes in promyelocytic leukemia protein nuclear bodies (PML-NB) with CREB3 and HCFC1. Belongs to the bZIP family. ATF subfamily. Contaminating sequence. Sequence derived from chromosome 13 in the N-terminal part.