The p53 protein consists of 393 residues and can be divided into three functional regions: (i) an N-terminal domain (residues 1–93) containing a transcriptional activation domain and a proline-rich domain; (ii) a core DNA-binding globular domain (residues 102–292), which contains most of the mutations found in cancers; and (iii) a C-terminal domain (CTD) consisting of a tetramerization domain (residues 320–356) and a regulatory domain (residues 363–393). The gene discussed is TP53; the disease is cancer.