作者: X Chen , N Gohain , C Zhan , W-Y Lu , M Pazgier
DOI: 10.1038/ONC.2015.255
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摘要: The tumor-suppressor protein p53 is tightly controlled in normal cells by its two negative regulators—the E3 ubiquitin ligase MDM2 and homolog MDMX. Under stressed conditions such as DNA damage, escapes MDM2- MDMX-mediated functional inhibition degradation, acting to prevent damaged from proliferating through induction of cell cycle arrest, repair, senescence or apoptosis. Ample evidence suggests that stress signals induce phosphorylation MDMX, leading activation. However, the structural basis stress-induced activation remains poorly understood because paucity technical means produce site-specifically phosphorylated MDMX proteins for biochemical biophysical studies. Herein, we report total chemical synthesis, via native ligation, characterization (24–108)MDMX Tyr99-phosphorylated analog with respect their ability interact a panel p53-derived peptide ligands PMI, p53-mimicking but more potent antagonist using FP surface plasmon resonance techniques. Phosphorylation at Tyr99 weakens binding approximately orders magnitude. Comparative X-ray crystallographic analyses pTyr99 complex PMI well modeling studies reveal phosphate group imposes extensive steric clashes C-terminus induces significant lateral shift ligand, contributing dramatic decrease affinity p53. Because damage activates c-Abl tyrosine kinase phosphorylates Tyr99, our findings afford rare glimpse level how dislodges inhibitory it response damage.