Enables DNA-binding transcription activator activity, RNA polymerase II-specific; RNA polymerase II cis-regulatory region sequence-specific DNA binding activity; and identical protein binding activity. Involved in circadian regulation of gene expression; negative regulation of transcription, DNA-templated; and positive regulation of transcription by RNA polymerase II. Acts upstream of or within several processes, including NIK/NF-kappaB signaling; antigen processing and presentation; and mononuclear cell differentiation. Located in cytosol and nucleus. Is expressed in axial skeleton; eye; heart; and ureter. Used to study atopic dermatitis. Human ortholog(s) of this gene implicated in breast cancer and immunodeficiency 53. Orthologous to human RELB (RELB proto-oncogene, NF-kB subunit). [provided by Alliance of Genome Resources, Apr 2022]