title: Regulation of MDM2 E3 ligase activity by phosphorylation after DNA damage.
abstract: MDM2 is a major regulator of p53 by acting as a ubiquitin E3 ligase. The central acidic domain and C-terminal RING domain of MDM2 are both indispensable for ubiquitination of p53. Our previous study suggested that ATM phosphorylation of MDM2 near the C terminus inhibits RING domain oligomerization, resulting in p53 stabilization after DNA damage. We present here evidence that these modifications allosterically regulate the functions of both acidic domain and RING domain of MDM2. Using chemical cross-linking, we show that the MDM2 RING domain forms oligomers including dimer and higher-order complexes in vivo. RING domain dimerization efficiency is negatively regulated by upstream sequence. ATM-mediated phosphorylation of the upstream sequence further inhibits RING dimerization. Forced oligomerization of MDM2 partially overcomes the inhibitory effect of phosphorylation and stimulates p53 ubiquitination. Furthermore, the ability of MDM2 acidic domain to bind p53 core domain and induce p53 misfolding are also suppressed by the same C-terminal ATM sites after DNA damage. These results suggest that the acidic domain and RING domain of MDM2 are both allosterically coupled to the intervening ATM sites, which enables the same modification to regulate multiple MDM2 functions critical for p53 ubiquitination.
authors: Molecular Oncology Department, Moffitt Cancer Center, Tampa, Florida 33612, USA.
authors: Qian
authors: Q
authors: Cheng
authors: Brittany
authors: B
authors: Cross
authors: Baozong
authors: B
authors: Li
authors: Lihong
authors: L
authors: Chen
authors: Zhenyu
authors: Z
authors: Li
authors: Jiandong
authors: J
authors: Chen
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D004249:DNA Damage / Q000187:drug effects*; D005786:Gene Expression Regulation; D006801:Humans; D010766:Phosphorylation; D010957:Plasmids; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism
chemical_list: C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D044767:Ubiquitin-Protein Ligases