The notch receptor consists of an extracellular domain that is non-covalently linked to a protein with a transmembrane and an intracellular domain. Notch signaling is initiated by the binding of a membrane-bound ligand to the extracellular domain of the Notch receptor of a neighboring cell. The transmembrane domain is cleaved from the intracellular domain. As a result, the intracellular domain diffuses into the cytosol and can enter the nucleus, where it prevents the suppression of gene expression. Mutations in the Notch coding genes are found in several human tumors like T-cell leukemia.