Describe the p53/MDM2/p14ARF pathway in cells with DNA damage

If DNA is damged, P53 is phosphorylated, it cannot bind to MDM2 to form P53/MDM2 complex. This means that teh amount of P53 in the cell increases, and halts the G1-S transition, co stimulating other protein transcription, necessary for DNA repair. Once the DNA is repaired, P53 becomes unphosphorylated and can be degraded by the MDM2 protein. In the occurance of extensive DNA damage, P14RAF encoded by the CDK4N2a protein, inhibits the breakdown of p 53 and triggers the start of cellular apoptosis.