Transcriptional regulator that acts as a repressor or activator (By similarity). Binds to Maf recognition elements (MARE) (By similarity). Plays an important role in coordinating transcription activation and repression by MAFK (By similarity). Induces apoptosis in response to oxidative stress through repression of the antiapoptotic factor HMOX1 (PubMed:17018862). Positively regulates the nuclear import of actin (By similarity). Is a key regulator of adaptive immunity, crucial for the maintenance of regulatory T-cell function and B-cell maturation (PubMed:28530713).