The human p53 gene is located on chromosome 17.
The p53 protein is a phosphoprotein made of ~390 amino acids. It consists of three units (or domains):
p53 protein has been voted molecule of the year.
- A domain that activates transcription factors.
- A domain that recognizes specific DNA sequences.
- A domain that recognized damaged DNA, such as misaligned base pairs or single-stranded DNA.
The p53 protein can regulate the cell in several ways:
- It can activate DNA repair proteins when it recognizes damaged DNA.
- It can also hold the cell cycle at the G1/S regulation point on DNA damage recognition.
- It can initiate apoptosis, the programmed cell death, if the DNA damage proves to be irrepairable.
If the p53 gene is damaged, tumor suppression is severely reduced. People who inherit only one functional copy of p53 will most likely develop tumors in early adulthood, a disease known as Li-Fraumeni syndrome. p53 can also be damaged in cells by mutagens (chemicals, radiation or viruses), increasing the likelihood that the cell will begin uncontrolled division. More than 50 percent of human tumors contain a mutation or deletion of the p53 gene.