MEK1 (also known as extracellular signal-regulated kinases, ERKs) plays important role in the MAP kinase cascade, which transduces multiple extracellular signals to control cell growth, proliferation and differentiation. Activated upon growth factors stimulation, MEK1 phosphorylates MAPK3/ERK1 and MAPK1/ERK2, thus activates the MAP pathway and regulates transcription. Abnormal of the MEK1 protein, including point mutations, are implicated in diseases such as cardiofaciocutaneous syndrome (CFC) and melanoma.