PML links aberrant cytokine signaling and oncogenic stress to cellular senescence

Abstract

Senescence is a tumor suppressor mechanism triggered by oncogenic stimuli and characterized by a permanent cell cycle arrest mediated by tumor suppressors such as p53, Rb and PML. PML itself is critical for the formation of nuclear bodies (PML bodies) that accumulate in senescent cells rendering them suitable markers for the senescence phenotype. The mechanism of PML-induction during senescence is complex and includes increased PML gene transcription by p53 or transcription factors of the interferon/Jak/Stat pathway. In turn, PML engages both p53 and Rb, although the precise molecular processes are unknown. PML interacts with the DNA-binding domain of p53 facilitating p53 modifications. PML can also interact with Rb and may play a role in Rb-dependent gene silencing during senescence. Recent studies suggest an additional connection between PML and the senescence program. Senescence involves a constitutive activation of the DNA damage response. Intriguingly, proteins that signal DNA damage or help repairing it localize to PML bodies, suggesting that PML may play a role in the DNA damage response during senescence. We think that the discovery of factors acting upstream or downstream PML may help to understand how cells bypass senescence on their way to tumorigenesis. More importantly the PML pathway may eventually lead to novel anti-cancer therapies.