Functional Interrogation of the N-Terminal Lid of MDMX in p53 Binding <i>via</i> Native Chemical Ligation

Abstract

1) is a transcription factor that plays an important role in maintaining genetic stability and preventing the development of cancer.2) In response to numerous cellular stresses, p53 activation can mediate cell cycle arrest, senescence, apoptosis or DNA repair.3) P53 is negatively regulated by the E3 ubiquitin ligase MDM2 and its homolog MDMX.4-6) MDM2 can form homodimer with E3 ubiquitin ligase activity leading to p53 proteosomal degradation depending on a catalytically active RING domain.7-10) MDMX has no intrinsic E3 ubiquitin active RING domain but can efficiently inhibit the p53 activity by either independent manner or forming heterodimer with MDM2 through their RING domain becoming a more effective p53 E3 ubiquitin ligase complex. [11][12][13] There is a balanced turnover of MDM2, MDMX and p53, as revealed by mouse models that deletion of either gene of MDM2 or MDMX is lethal in a p53-denpent manner.14) Both MDM2 and MDMX bind to p53 via N-terminal p53-binding domains to control the level of p53.15) It is fundamentally important in cancer biology and therapy to study the molecular mechanisms of p53-MDM2/MDMX interaction.Ample evidence suggests that the MDMX lid (residues 1-24) is partially structured and occlude p53 binding cleft of apo-MDM2 that can significantly reduce its binding affinity with p53 for dozens of times. [16][17][18] However, the function of the N-terminal lid of MDMX still remains poorly understood.

Designing dual inhibitors of Mdm2/MdmX: Unexpected coupling of water with gatekeeper Y100/99

“…In our study, we did not model the lid of Mdm2 and MdmX. However, it is known that only the Mdm2 lid, not MdmX lid (residues 1–25) affects the binding affinity to p53 . A next step is to study the effect of the Mdm lid on the gatekeeper tyrosine 100/99, and their combined effect on p53 and dual inhibitors.…”