Transcriptional regulator that acts as 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). Homodimer; disulfide-linked (PubMed:22194330). Heterodimer of BACH2 and Maf-related transcription factors (By similarity). Nucleocytoplasmic shuttling is controlled by phosphorylation. B-cell specific. Phosphorylation at Ser-521 downstream of the PI-3K pathway promotes nuclear export. The reversible disulfide bond may provide a mechanism to regulate the activity in oxidative stress responses. The disease is caused by variants affecting the gene represented in this entry. Belongs to the bZIP family. CNC subfamily.