Transcriptional regulator that acts as repressor or activator (PubMed:8887638). Binds to Maf recognition elements (MARE) (PubMed:8887638). Plays an important role in coordinating transcription activation and repression by MAFK (PubMed:8887638). Induces apoptosis in response to oxidative stress through repression of the antiapoptotic factor HMOX1 (By similarity). Positively regulates the nuclear import of actin (PubMed:26021350). Is a key regulator of adaptive immunity, crucial for the maintenance of regulatory T-cell function and B-cell maturation (PubMed:28530713). Homodimer; disulfide-linked (By similarity). Heterodimer of BACH2 and Maf-related transcription factors (PubMed:8887638). Nucleocytoplasmic shuttling is controlled by phosphorylation. Detected in brain and spleen. In brain, expression is lower in the adult than in the neonate. The reversible disulfide bond may provide a mechanism to regulate the activity in oxidative stress responses. Phosphorylation at Ser-520 downstream of the PI-3K pathway promotes nuclear export. Belongs to the bZIP family. CNC subfamily.