Myocyte Enhancer Factor

In the field of molecular biology, myocyte enhancer factor-2 (Mef2) proteins are a family of transcription factors which through control of gene expression are important regulators of cellular differentiation and consequently play a critical role in embryonic development. In adult organisms, Mef2 proteins mediate the stress response in some tissues. Mef2 proteins contain both MADS-box and Mef2 DNA-binding domains.

Mef2 was originally identified as a transcription factor complex through promoter analysis of the muscle creatine kinase (mck) gene to identify nuclear factors interacting with the mck enhancer region during muscle differentiation. Three human mRNA coding sequences designated RSRF (Related to Serum Response Factor) were cloned and shown to dimerize, bind a consensus sequence similar to the one present in the MCK enhancer region, and drive transcription. RSRFs were subsequently demonstrated to encode human genes now named Mef2A, Mef2B and Mef2D.

The Mef2 gene is widely expressed in all branches of eukaryotes from yeast to humans. While Drosophila has a single Mef2 gene, vertebrates have at least four versions of the Mef2 gene (human versions are denoted as MEF2A, MEF2B, MEF2C, and MEF2D), all expressed in distinct but overlapping patterns during embryogenesis through adulthood.

All of the mammalian Mef2 genes share approximately 50% overall amino acid identity and about 95% similarity throughout the highly conserved N-terminal MADS-box and Mef2 domains, however their sequences diverge in their C-terminal transactivation domain (see figure to the right).

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