Human tumour protein p63. Molecular model of the tetramerization domain of the human tumour protein p63, encoded by the TP63 gene. It is a transcription factor that has been identified as being responsible for a range of developmental defects. Examples include skin defects such as cleft palates and cleft lips. The presence of this protein is also a diagnostic aid for conditions such as prostate cancer. This domain has four protein chains (orange, pink, green, blue).