The Barrett's antigen anterior gradient-2 silences the p53 transcriptional response to DNA damage

Elizabeth Pohler, Ashley L Craig, James Cotton, Laura Lawrie, John F Dillon, Pete Ross, Neil Kernohan, Ted R Hupp

Research output: Contribution to journalArticlepeer-review

Abstract

The esophageal epithelium is subject to damage from bile acid reflux that promotes normal tissue injury resulting in the development of Barrett's epithelium. There is a selection pressure for mutating p53 in this preneoplastic epithelium, thus identifying a physiologically relevant model for discovering novel regulators of the p53 pathway. Proteomic technologies were used to identify such p53 regulatory factors by identifying proteins that were overexpressed in Barrett's epithelium. A very abundant polypeptide selectively expressed in Barrett's epithelium was identified as anterior gradient-2. Immunochemical methods confirmed that anterior gradient-2 is universally up-regulated in Barrett's epithelium, relative to normal squamous tissue derived from the same patient. Transfection of the anterior gradient-2 gene into cells enhances colony formation, similar to mutant oncogenic p53 encoded by the HIS175 allele, suggesting that anterior gradient-2 can function as a survival factor. Deletion of the C-terminal 10 amino acids of anterior gradient-2 neutralizes the colony enhancing activity of the gene, suggesting a key role for this domain in enhancing cell survival. Constitutive overexpression of anterior gradient-2 does not alter cell-cycle parameters in unstressed cells, suggesting that this gene is not directly modifying the cell cycle. However, cells overexpressing anterior gradient-2 attenuate p53 phosphorylation at both Ser(15) and Ser(392) and silence p53 transactivation function in ultraviolet (UV)-damaged cells. Deletion of the C-terminal 10 amino acids of anterior gradient-2 permits phosphorylation at Ser(15) in UV-damaged cells, suggesting that the C-terminal motif promoting colony survival also contributes to suppression of the Ser(15) kinase pathway. These data identify anterior gradient-2 as a novel survival factor whose study may shed light on cellular pathways that attenuate the tumor suppressor p53.
Original languageEnglish
Pages (from-to)534-47
Number of pages14
JournalMolecular and Cellular Proteomics
Volume3
Issue number6
DOIs
Publication statusPublished - Jun 2004

Keywords

  • Amino Acid Sequence
  • Barrett Esophagus
  • Cell Cycle
  • Cell Survival
  • Colony-Forming Units Assay
  • DNA Damage
  • Electrophoresis, Gel, Two-Dimensional
  • Epithelial Cells
  • Gene Silencing
  • Humans
  • Intestinal Neoplasms
  • Mass Spectrometry
  • Metaplasia
  • Molecular Sequence Data
  • Phosphorylation
  • Protein Disulfide-Isomerases
  • Sequence Homology, Amino Acid
  • Transcription, Genetic
  • Tumor Suppressor Protein p53
  • Ultraviolet Rays
  • Xenopus Proteins

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