The p53 tumor-suppressor gene integrates numerous signals that control cell life and death. Several novel molecules involved in the p53 network, including Chk2, p53R2, p53AIP1, Noxa, PIDD, PID/MTA2, MTBP and PERP, were identified and their genes were cloned recently. PERP, also termed PIGPC1 and THW, is a plasma membrane protein. p53 binds to the promoter of PERP and transcriptionally activates PERP gene then the translated PERP protein mediates the p53 induced apoptosis. The expression of PERP causes cell death. PERP is a mediator of p53 induced apoptosis. PERP has sequence similarity to PMP-22/gas3 and is a new member of the PMP-22/gas3 family.