title: ATM activates p53 by regulating MDM2 oligomerization and E3 processivity.
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.
authors.affiliation: Department of Molecular Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Cheng
authors.forename: Lihong
authors.initials: L
authors.lastname: Chen
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Li
authors.forename: William S
authors.initials: WS
authors.lastname: Lane
authors.forename: Jiandong
authors.initials: J
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D002850:Chromatography, Gel; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism*; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D025801:Ubiquitin / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D044767:Ubiquitin-Protein Ligases; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex