What does p53 do?
The p53 protein performs three critical functions that together prevent cancer. When any one fails — the consequences are severe.
Damage Sensor
When DNA sustains damage from radiation, chemicals, or replication errors, p53 levels spike rapidly — triggering a cellular emergency response that pauses normal operations.
Growth Arrest
p53 activates genes that halt cell division, buying time for DNA repair machinery to fix the damage before it gets copied into daughter cells and passed on.
Apoptosis
If damage cannot be repaired, p53 triggers programmed cell death — eliminating the compromised cell before it can accumulate further mutations and become malignant.
When It Fails
Cancer mutations disable all three functions. Some mutant p53 proteins additionally gain new cancer-promoting activities — a phenomenon called gain-of-function mutation.
The MDM2 Balance
In healthy cells, p53 is kept at low levels by MDM2 — a protein that p53 itself activates, creating a self-regulating feedback loop. When DNA damage strikes, this loop is broken and p53 levels surge. Many cancers exploit MDM2 overexpression to silence p53 without directly mutating the TP53 gene.