Multiple mechanisms and functions of Maf transcription factors in the regulation of tissue-specific genes

Maf family transcription factors are regulators of tissue-specific gene expression and cell-differentiation in a wide variety of tissues and are also involved in human diseases and oncogenic transformation. To establish tissue-specific expression, Maf binds to Maf-recognition elements (MAREs) in the regulatory regions of target genes, and functionally interacts with other transcription factors. For example, L-Maf and c-Maf, which are specifically expressed in developing lens cells, act synergistically with Sox proteins to induce lens-specific crystalline genes. MafA, a beta-cell-specific member of the Maf family, activates the insulin gene promoter synergistically with Pdx1 and Beta2 to establish beta-cell specific expression. Furthermore, in beta-cells, MafA activity is regulated at both the transcriptional and post-translational levels by glucose and oxidative stress. This review summarizes the functions and roles of Maf in various biological processes and recent progress in elucidating the mechanisms whereby Maf proteins regulate transcription.