Fig. 3: P53: an informed stress responder.
The p53 and MDM-2 proteins form a module in the cell where p53 transcribes the MDM-2 gene and the MDM-2 protein promotes the degradation of the p53 protein. Stress signals, in this case, DNA damage is sensed by the ATM protein which phosphorylates a CHEK-2 mediator which in turn phosphorylate serine -15 in the p53 protein, and other sites in p53 and MDM-2, that disrupts the MDM-2-P53 protein complex. This increases p53 protein levels and along with other epigenetic modifications of p53 and MDM-2 the p53 transcription factor makes an informed choice between cell cycle arrest, DNA repair, and return to homeostasis or programed cell death by one of five possible methods [10].
