P53

p53 (or tp53) is a gene vital to many forms of life, including humans. It codes for a protein which suppresses cancer. It has been called "the guardian of the genome".^[1]

p53 pathway: In a normal cell, p53 is inactivated by its negative regulator, mdm2.
When DNA is damaged, the gene gets activated. Once activated, p53 stops the cell division cycle. Either repair of the cell or apoptosis occurs. How p53 makes this choice is not known

The p53 gene is the most frequently mutated gene (>50%) in human cancer.^[2] Its protein product binds to DNA and regulates gene expression to prevent mutations of the genome.^[3]

p53 protein (TP53) is at low levels in human embryonic stem cells (hESCs).^[4] This allows the most important cell division to proceed rapidly.