The p53 Protein, a Guardian of the Genome

The p53 protein (named after its molecular
weight of 53 kD), a nuclear phosphoprotein, is
indispensable for genomic integrity and cell
cycle control. It binds to specific DNA sequences
and regulates the expression of different regulatory
genes involved in growth. It interacts
with other proteins in response to DNA damage
and mediates apoptosis (cell death) of the cell
when the damage is beyond repair. Its basic
function is to control entry of the cell into the S
phase (see cell cycle control, p. 112). Somatic
mutations in the p53 gene occur in about half of
all tumors. Germline mutations lead to a familial
form of multiple different cancers