Cited by 165Cancer-related Molecular PathwaysUbiquitin and proteasome pathwaysDNA Repair Mechanisms

The DOI matches its Crossref record; 45 of the 47 references it cites were found in a registry or an index; none of the 25 sources its claims cite is checked for support yet.

ATM activates p53 by regulating MDM2 oligomerization and E3 processivity

Open access

Abstract

Rapid activation of p53 by ionizing irradiation is a classic DNA damage response mediated by the ATM kinase. However, the major signalling target and mechanism that lead to p53 stabilization are unknown. We show in this report that ATM induces p53 accumulation by phosphorylating the ubiquitin E3 ligase MDM2. Multiple ATM target sites near the MDM2 RING domain function in a redundant manner to provide robust DNA damage signalling. In the absence of DNA damage, the MDM2 RING domain forms oligomers that mediate p53 poly ubiquitination and proteasomal degradation. Phosphorylation by ATM inhibits RING domain oligomerization, specifically suppressing p53 poly ubiquitination. Blocking MDM2 phosphorylation by alanine substitution of all six phosphorylation sites results in constitutive degradation of p53 after DNA damage. These observations show that ATM controls p53 stability by regulating MDM2 RING domain oligomerization and E3 ligase processivity. Promoting or disrupting E3 oligomerization may be a general mechanism by which signalling kinases regulate ubiquitination reactions, and a potential target for therapeutic intervention.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

ATM phosphorylates multiple C-terminal sites on MDM2, inhibiting MDM2 RING-domain oligomerization and thereby blocking p53 polyubiquitination and degradation. This provides a mechanism for rapid p53 stabilization after DNA damage and suggests E3 oligomerization as a regulatory target.

Key findings

  • Mass spectrometry identified six MDM2 phosphorylation sites near the RING domain—S386, S395, S407, T419, S425, and S429—with S386 and S429 induced by IR and other DNA-damaging agents; ATM was required for their phosphorylation, and ATM directly phosphorylated S386/S429 in vitro.
  • Phospho-mimic MDM2 mutants were partially defective in p53 degradation, while MDM2-6A (all six sites mutated to alanine) increased p53 degradation; MDM2-6A blocked p53 accumulation for up to 8 h after IR and impaired p21 induction, but did not affect MDMX degradation.
  • MDM2 phosphorylation specifically reduced p53 polyubiquitination while retaining substantial p53 mono/oligo-ubiquitination; in vitro, MDM2-6D mainly induced p53 mono-ubiquitination, whereas MDM2-6A was more active in p53 polyubiquitination.
  • In nonirradiated cells, about 50% of the MDM2 RING domain migrated as oligomers (~200 kDa) and 50% as monomers (~15 kDa); IR inhibited RING oligomerization, and the ATM inhibitor KU55933 restored it. Non-phosphorylated RING bound MDM2 with much higher affinity than phosphorylated RING.

Methods

  • Cell-based assays used 293T, SJSA, ATM-deficient Hs235, normal human foreskin fibroblast, H1299, and U2OS cells; MDM2 point mutants were generated by site-directed mutagenesis, and U2OS lines stably expressing MDM2 mutants were selected with G418.
  • MDM2 phosphorylation sites were mapped by mass spectrometry after 10 Gy IR and MG132; phospho-specific antibodies, in vitro kinase reactions with FLAG-ATM/Chk1/Chk2, in vivo and in vitro ubiquitination assays, caspase-3 cleavage, and gel filtration chromatography were used.
  • Functional consequences were assessed by western blot, immunoprecipitation, autoradiography, densitometry, 3H-thymidine incorporation after 10 Gy IR, and colony formation after 0–7.5 Gy IR over 15 days.

Limitations

  • The paper does not state limitations.
  • Evident from the text: all experiments are in cultured human cell lines, with no in vivo animal models or primary tumor data.
  • Evident from the text: conclusions rely heavily on overexpression and phospho-mimic/alanine MDM2 mutants, and the proposed conformational/steric mechanism in Figure 9 is a model rather than a direct structural demonstration.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/emboj.2009.294

Cites

45 of 45 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

24 Own result · 15 Not checked yet · 13 Own interpretation · 5 Own method · 1 No basis given

Verify all 25 references — free account

Show all 36 claims

  • It may state two separate claims as one. 14
  • Probably not a substantial claim. 10
  • The quote only partly states this claim. 2
22 of 22
  • The paper relies on this without support.

    Phosphomimic substitutions with aspartate or glutamate at ATM target sites functionally mimic phosphorylation of MDM2.

    “However, S386E and S429D phospho-mimic mutants were partially defective in p53 degradation (Figure 3A).”
  • The paper relies on this without support.

    Alanine substitution at the six MDM2 phosphorylation sites prevents their phosphorylation.

    “Interestingly, substitution of all six phosphorylation sites with alanine (MDM2-6A) significantly increased p53 degradation (Figure 3B and C).”
  • The paper relies on this without support.

    The MDM2 RING domain oligomers observed in vitro correspond to the functional E3 complex that mediates p53 polyubiquitination in cells.

    “In the absence of DNA damage, the MDM2 RING domain forms oligomers that mediate p53 poly ubiquitination and proteasomal degradation.”
  • The paper relies on this without support.

    High-order E3 structures help expose multiple E2 active sites to the substrate and speed up the reaction.

    “Mechanistically, formation of high-order structures by E3 helps to present multiple E2 active sites to the substrate and increase the reaction rate.”
4 of 4

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

1 of 1

Citations

Cites

Cited by

Sorted by citations

See all 165

Metadata

Authors
Cheng, Q., Chen, L., Li, Z., Lane, W. S., & Chen, J.
Affiliations
  • Moffitt Cancer Center (US)
  • Harvard University (US)
Corresponding author
Chen, Jiandong
Venue
The EMBO Journal
Published
2009-10-08
Volume
28
Issue
24
Pages
3857-3867
ISSN
  • 0261-4189 (ISSN-L)
  • 1460-2075
OpenAlex
W2052556036
Cited by
165
References
47
Citations by year
2026: 11 · 2025: 3 · 2024: 4 · 2023: 6 · 2022: 10 · 2021: 7 · 2020: 9 · 2019: 4 · 2018: 6 · 2017: 11 · 2016: 8 · 2015: 14 · 2014: 11 · 2013: 12 · 2012: 23
FWCI
8.15
Type
journal article
Language
en
Open access
Locations
  • The EMBO Journal (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institutes of Health
  • National Cancer Institute (R01CA109636, CA 109636, CA118219)
Topics
  • Health Sciences › Medicine › Oncology › Cancer-related Molecular Pathways
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Ubiquitin and proteasome pathways
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › DNA Repair Mechanisms
Keywords
ATM kinase, p53 stabilization, MDM2, proteasomal degradation, DNA damage response, ionizing radiation, kinase phosphorylation
MeSH terms
Amino Acid Sequence, Cell Line, Chromatography, Gel, DNA Damage, DNA-Binding Proteins, Humans, Molecular Sequence Data, Phosphorylation, Signal Transduction, Tumor Suppressor Protein p53, Protein Serine-Threonine Kinases, Cell Cycle Proteins, Tumor Suppressor Proteins, Ubiquitin, Ubiquitin-Protein Ligases, Cell Line, Tumor, Proteasome Endopeptidase Complex, Proto-Oncogene Proteins c-mdm2, Ataxia Telangiectasia Mutated Proteins

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-08, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-08 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review