Figure 1.

The p53 pathway. p53 is under normal conditions inactivated by murine double minute 2 (MDM2). When, e.g., DNA damage occurs, p53 dissociates from its regulatory MDM2 complex by various pathways. In this active state, phosphorylated p53 will induce a cell-cycle arrest to permit either repair and therefore survival of the cell or induce apoptosis to eliminate a damaged cell.