TFE3 transcription factor regulates the expression of MAFB during macrophage differentiation

Transcription Factor for Immunoglobulin Heavy-Chain Enhancer 3 (Tfe3) is a transactivator of metabolic genes that are regulated through an EBox located in their promoters. It is involved in physiological processes such as osteoclast and macrophage differentiation, as well as in pathological processes such as translocations underlying different cancer diseases. MAFB is a basic region/leucine zipper transcription factor that affects transcription by binding specific DNA regions known as MARE. It plays a pivotal role in regulating lineage-specific hematopoiesis by repressing transcription of erythroid specific genes in myeloid cells and enhancing expression of macrophage and megakaryocytic genes. Here we have shown MAFB to be highly induced in human hematopoietic cells undergoing macrophage differentiation following Tfe3 ectopic expression, and to be down regulated, compared to the controls, in the same cell population following Phorbol Esters (PMA) dependent differentiation coupled to Tfe3 gene silencing. Electrophoretic mobility shift assays identified a Tfe3-binding site (EBox) in the MAFB promoter region that is conserved in different mammalian species. MAFB promoter was transactivated by co-expression of Tfe3 in reporter gene assays while deletion or mutation of the MAFB EBox prevented transactivation by Tfe3. Both of these genes were previously included in the group of transcription factors able to drive macrophage differentiation. The observation that MAFB belongs to the Tfe3 regulon suggests the existence of a pathway where these two gene families act synergistically to determine differentiation.