Acts as a transcriptional activator or repressor. Plays a pivotal role in regulating lineage-specific hematopoiesis by repressing ETS1-mediated transcription of erythroid-specific genes in myeloid cells. Required for monocytic, macrophage, osteoclast, podocyte and islet beta cell differentiation. Involved in renal tubule survival and F4/80 maturation. Activates the insulin and glucagon promoters. Together with PAX6, transactivates weakly the glucagon gene promoter through the G1 element. SUMO modification controls its transcriptional activity and ability to specify macrophage fate. Binds element G1 on the glucagon promoter. Involved either as an oncogene or as a tumor suppressor, depending on the cell context. Required for the transcriptional activation of HOXB3 in the rhombomere r5 in the hindbrain (PubMed:11823429). Homodimer or heterodimer with other bHLH-Zip transcription factors. Forms homodimers and heterodimers with FOS, FOSB and FOSL2, but not with JUN proteins (JUN, JUNB and JUND). Interacts with the intracellular cytoplasmic domain of LRP1 (LRPICD); the interaction results in a moderate reduction of MAFB transcriptional potential (By similarity). Binds DNA as a homodimer or a heterodimer. Interacts with PAX6; the interaction is direct. Interacts with ETS1 and LRP1. Expressed in pancreatic alpha-cells (glucagon-positive cells), in podocytes of the kidney and macrophages (at protein level). Most abundant in kidney, gut, lung and brain. Expressed in pancreatic alpha-cells at 10.5 dpc (PubMed:17901057). Expressed in insulin and glucagon islet progenitor cells at 12 dpc onwards (at protein level) (PubMed:16443760). Detectable at 8.0 dpc (one somite) as a band in the caudal hindbrain and by 8.5 dpc (six to eight somites) as a sharp rostral edge coincident with the rhombomeres (r) 4 and 5 boundary and a diffuse caudal edge located midway through r6 (PubMed:8001130). Expressed in the lens epithelial cells at 10.5 to 14.5 dpc (PubMed:10383433). Expressed in the cochlear nucleus at 15.5 dpc (PubMed:17977745). The leucine-zipper domain is involved in the interaction with LRPICD. Sumoylated. Sumoylation on Lys-32 and Lys-297 stimulates its transcriptional repression activity and promotes macrophage differentiation from myeloid progenitors. Mice show a defect in frequency of respiratory rhythm with a fatal apnea at birth due to lack of neurons from the preBoetC region. They displayed renal dysgenesis with abnormal podocyte differentiation as well as tubular apoptosis. They show altered actin-dependent macrophage morphology. They show a reduced number of cells expressing insulin and glucagon. Embryos also lack the abducens nerve which normaly innervates the lateral rectus muscle that is involved in eye movement (PubMed:27181683). Belongs to the bZIP family. Maf subfamily.