Activates erythroid-specific, globin gene expression. Heterodimer with MAFG, MAFK and other small MAF proteins that binds to the MAF recognition elements (MARE). High level expression in brain, thymus, testis and placenta. Medium level expression in uterus, stomach and lung. Low level expression in kidney. No expression in heart, liver, spleen and ovary. Belongs to the bZIP family. CNC subfamily.