Dual-site regulation of MDM2 E3-ubiquitin ligase activity.
The control of p53 ubiquitination by MDM2 provides a model system to define how an E3-ligase functions on a conformationally flexible substrate. The mechanism of MDM2-mediated ubiquitination of p53 has been analyzed by deconstructing, in vitro, the MDM2-dependent ubiquitination reaction. Surprisingly, ligands binding to the hydrophobic cleft of MDM2 do not inhibit its E3-ligase function. However, peptides from within the DNA binding domain of p53 that bind the acid domain of MDM2 inhibit ubiquitination of p53, localizing a motif that harbors a key ubiquitination signal. The binding of ligands to the N-terminal hydrophobic cleft of MDM2 reactivates, in vitro and in vivo, MDM2-catalyzed ubiquitination of p53F19A, a mutant p53 normally refractory to MDM2-catalyzed ubiquitination. We propose a model in which the interaction between the p53-BOX-I domain and the N terminus of MDM2 promotes conformational changes in MDM2 that stabilize acid-domain interactions with a ubiquitination signal in the DNA binding domain of the p53 tetramer.
Wallace
Maura
M
CRUK Interferon and Cell Signalling Group, University of Edinburgh Cancer Research Centre, Crewe Road South, Edinburgh EH4 2XR, United Kingdom.
Worrall
Erin
E
Pettersson
Susanne
S
Hupp
Ted R
TR
Ball
Kathryn L
KL
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D008024:Ligands; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism* / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
D008024:Ligands; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D051736:Proto-Oncogene Proteins c-mdm2; D044767:Ubiquitin-Protein Ligases