Putting the brakes on p53-driven apoptosis

Cell Cycle. 2012 Nov 15;11(22):4122-8. doi: 10.4161/cc.21997. Epub 2012 Sep 14.

Abstract

Following genotoxic stress, cells activate a complex, kinase-based signaling network to arrest the cell cycle and initiate DNA repair or apoptosis. The tumor suppressor p53 lies at the heart of this DNA damage response. p53 mediates the transactivation of both cell cycle-regulating and pro-apoptotic clusters of target genes. However, it remains incompletely understood which signaling molecules dictate the choice between these two opposing p53-dependent cellular outcomes. Over recent years, numerous regulatory mechanisms impacting on the cellular outcome of p53 signaling have been described. However, no single dominant mechanism has thus far been identified to regulate the cellular choice between p53-driven apoptosis or senescence. The transcriptional regulator AATF has recently emerged as a novel factor impacting on the cellular outcome of the p53 response. Upon genotoxic stress, cytoplasmic pools of MRLC-bound AATF are phosphorylated through the p38MAPK/MK2 checkpoint kinase complex. This AATF phosphorylation results in the disruption of cytoplasmic MRLC3:AATF complexes followed by rapid nuclear localization of AATF. Once in the nucleus, AATF binds to the PUMA, BAX and BAK promoters to repress the DNA damage-induced expression of these pro-apoptotic p53 target genes. Depletion of AATF in tumor cells results in a dramatically enhanced response to DNA-damaging chemotherapeutics, both in vitro and in vivo. Furthermore, focal copy number gains at the AATF locus in neuroblastoma correlate with adverse prognosis and reduced overall survival in this typically p53-proficient malignancy. These data identify the p38/MK2/AATF signaling pathway as a critical repressor of p53-driven apoptosis in tumor cells and implicate this signaling cascade as a novel target for chemotherapy-sensitizing therapeutic efforts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Apoptosis*
  • DNA Damage
  • HCT116 Cells
  • HEK293 Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Mice
  • NIH 3T3 Cells
  • Phosphorylation
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism
  • Repressor Proteins / metabolism
  • Signal Transduction
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*
  • bcl-2 Homologous Antagonist-Killer Protein / genetics
  • bcl-2 Homologous Antagonist-Killer Protein / metabolism
  • bcl-2-Associated X Protein / genetics
  • bcl-2-Associated X Protein / metabolism
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • AATF protein, human
  • Apoptosis Regulatory Proteins
  • BBC3 protein, human
  • Intracellular Signaling Peptides and Proteins
  • Proto-Oncogene Proteins
  • Repressor Proteins
  • Tumor Suppressor Protein p53
  • bcl-2 Homologous Antagonist-Killer Protein
  • bcl-2-Associated X Protein
  • MAP-kinase-activated kinase 2
  • Protein-Serine-Threonine Kinases
  • p38 Mitogen-Activated Protein Kinases