Journal Article

Dephosphorylation of p53 at Ser20 after cellular exposure to low levels of non-ionizing radiation

Burch, Lindsay R, Thompson, Alastair M, Craig, Ashley L, Blaydes, Jeremy P, Hupp, Ted R

1999

Overview

Induction of the transactivation function of p53 after cellular irradiation was studied under conditions in which upstream signaling events modulating p53 activation were uncoupled from those regulating stabilization. This investigation prompted the discovery of a novel radiation-responsive kinase pathway targeting Ser20 that results in the masking of the DO-1 epitope in undamaged cells. Unmasking of the DO-1 epitope via dephosphorylation occurs in response to low doses of non-ionizing radiation. Our data show that phosphorylation at Ser20 reduces binding of the mdm2 protein, suggesting that a function of the Ser20-kinase pathway may be to produce a stable pool of inactive p53 in undamaged cells which can be readily activated after cellular injury. Phospho-specific monoclonal antibodies were used to determine whether the Ser20 signaling pathway is coupled to the Ser15 and Ser392 radiation-responsive kinase pathways. These results demonstrated that: (1) dephosphorylation at Ser20 is co-ordinated with an increased steady-state phosphorylation at Ser392 after irradiation, without p53 protein stabilization, and (2) stabilization of p53 protein can occur without Ser15 phosphorylation at higher doses of radiation. These data show that the Ser20 and Ser392 phosphorylation sites are both targeted by an integrated network of signaling pathways which is acutely sensitive to radiation injury.

• Publisher: Nature Publishing,Nature Publishing Group
• Subject: Antibodies, Monoclonal - immunology / Biological and medical sciences / Breast Neoplasms - chemistry / Breast Neoplasms - immunology / Breast Neoplasms - pathology / Cell physiology / Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes / Dephosphorylation / Epitopes / Epitopes - metabolism / Female / Fundamental and applied biological sciences. Psychology / Humans / Ionizing radiation / Kinases / MDM2 protein / Molecular and cellular biology / Monoclonal antibodies / Nuclear Proteins / p53 Protein / Phosphorylation / Phosphorylation - radiation effects / Phosphoserine - chemistry / Phosphoserine - immunology / Protein Processing, Post-Translational - radiation effects / Protein Structure, Tertiary / Proteins / Proto-Oncogene Proteins - metabolism / Proto-Oncogene Proteins c-mdm2 / Radiation / serine / Serine - chemistry / Signal transduction / Signal Transduction - radiation effects / Transcriptional Activation - radiation effects / Tumor Cells, Cultured / Tumor Suppressor Protein p53 - immunology / Tumor Suppressor Protein p53 - metabolism / Ultraviolet Rays