MAFB

MafB, also known as v-maf musculoaponeurotic fibrosarcoma oncogene homolog B, is a transcription factor in mammals that belongs to the large Maf family of basic leucine zipper (bZIP) proteins. The MAFB gene encodes a protein of about 45 kDa that contains an N-terminal transactivation domain and a C-terminal basic region-leucine zipper necessary for DNA binding and dimerization. MafB binds to Maf recognition elements (MARE) in the regulatory regions of target genes and can form homodimers or heterodimers with other bZIP transcription factors to regulate gene expression.

MafB is expressed in various tissues, with prominent activity in myeloid lineages such as macrophages and dendritic cells, as well as in pancreatic islet cells. In the immune lineage, MafB contributes to macrophage differentiation and modulates inflammatory gene networks, and it participates in the development and maintenance of tissue-resident macrophage populations in certain contexts. In the pancreas, MafB plays a role in islet cell development and identity, notably influencing alpha-cell biology; species differences exist in the distribution of MafB between alpha and beta cells during development and maturation, reflecting distinct regulatory programs in humans and mice.

MafB operates as part of the broader Maf transcription factor family that governs diverse developmental and physiological processes. Its activity is modulated through interactions with other transcription factors and by cellular signaling pathways, enabling context-dependent regulation of target gene networks involved in differentiation, metabolism, and immune responses.

Research on MafB continues to clarify its tissue-specific roles and its involvement in normal development and disease contexts, including immune function and islet cell biology.