PERP expression stabilizes active p53 via modulation of p53-MDM2 interaction in uveal melanoma cells

Abstract

The activation and regulation of target genes by the tumour-suppressor p53 dictates the fate of a cell, with cell cycle arrest or apoptosis being two distinct outcomes. PERP (p53 apoptosis effector related to PMP-22), a p53 transcriptional target, is induced specifically during apoptosis but not cell cycle arrest. Downregulation of PERP is associated with the aggressive, monosomy 3-type of uveal melanoma (UM), the most common primary intraocular tumour in adults, and increased PERP expression has a pro-apoptotic effect in UM cells. Here, we identify a novel effect of PERP expression, as elevated PERP protein positively influences active levels of its own transcriptional regulator, p53. Using fluorescent fusion proteins of PERP, p53 and MDM2, we demonstrate in single living UM cells that PERP expression significantly enhances p53 activity and its nuclear localization, increases p53-dependent transcription (including that of MDM2) while allowing oscillatory nucleo-cytoplasmic shuttling of p53/MDM2 complexes. Phosphorylation of p53 serine residues that interfere with the interaction between p53 and its negative regulator MDM2 and enhance pro-apoptotic gene transcription also occurs subsequent to PERP expression. These results implicate a role for PERP in amplifying functional p53 levels that promote p53-dependent apoptosis, and reveal a potential target for exploitation in enhancing p53 activity.

Zebrafish Model for Functional Screening of Flow-Responsive Genes

“…PERP was previously identified as a p53 target gene by subtractive cloning of mouse embryonic fibroblasts and was shown to be expressed exclusively in apoptotic cells. 30 Interestingly, PERP can feed back to p53 to promote its activity 41 which is consistent with our observation that PERP and p53 cooperate to promote apoptosis in ECs. Our findings also resonate with previous studies that revealed post-translational modifications of p53 playing a role in disturbed flow-mediated EC apoptosis and contributing to atherosclerotic plaque formation.…”

Molecular dynamics of the full-length p53 monomer

“…147,148 The regulation of p53 protein half-life is crucial to his function 149,150 and, consequently, for cancer progression. [151][152][153] This proteosomal degradation is indeed a powerful therapeutic target. [154][155][156][157][158] The full-length p53 tetramer, bound to DNA, acquires different quaternary conformations 82 where the C-terminal and DBD directly interact; the N-terminal seems to only weakly associate with DBD, and no direct interactions between N-terminal and C-terminal are observed.…”

Lysine-specific modifications of p53: a matter of life and death?

“…As such an important regulator, the control of p53 protein status becomes crucial for cancer progression [15,16]. However, the question of how p53 defines which programs of cell cycle arrest, DNA repair pathways, or apoptosis to initiate is still debatable.…”