Allosteric Regulation of MDMX by Protein Disorder

MDMX和MDM2是通过不同的方式调节p53肿瘤抑制因子的同系物 机械装置。MDM2负责控制P53的降解，而MDMX则调节P53 DNA 结合和转录活动。MDMX过表达发生在人类肿瘤的一个亚群中 与P53的失活有关。P53对应激和DNA损伤的有效反应涉及磷酸化 MDMX后释放P53。成功靶向p53通路用于癌症治疗需要 了解MDMX如何调节P53功能。MDMX含有有序的P53结合域和 环状结构域和两个长的无序区域，它们在磷酸化过程中调节P53和CK1α的结合- 依赖的态度。我们的工作确定了MDMX所必需的分子内和分子间相互作用 功能：(1)MDMX/P53相互作用抑制P53 DNA结合。(2)MDMX/MDM2互动促进 MDMX降级。(3)MDMX/14-3-3相互作用促进MDMX核转位。(4) Mdmx/CK1α相互作用促进mdmx/P53结合，抑制P53。(5)MDMX分子内 相互作用调节P53的结合。重要的是，这些相互作用由两个磷酸化来调节 位于MDMX固有无序区(IDR)的位点(S289、S367)。我们假设 协调控制是由有序和无序区域之间的分子内相互作用所介导的 MDMX。IDRs调节依赖于磷酸化的分子内/分子间接触的切换 举止。我们提出了分子生物学和生物物理学相结合的方法来阐明这一机制。 MDMX调节：(1)确定MDMX IDR1的长度和灵活性如何调节自动- 抑制P53结合。(2)研究ck1α磷酸化如何将mdmx转换为开放。 抑制P53 DNA结合的构象。(3)确定IDR2的Chk2如何磷酸化 S367调节多个MDMX相互作用。这些实验将大大推进 了解应激信号如何通过靶向MDMX的无序区域激活P53，这是 对于开发用于癌症治疗的MDMX抑制剂至关重要。

MDMX and MDM2 are homologues that regulate the p53 tumor suppressor using different mechanisms. While MDM2 is responsible for controlling p53 degradation, MDMX regulates p53 DNA binding and transcriptional activities. MDMX overexpression occurs in a subset of human tumors leading to inactivation of p53. Efficient p53 response to stress and DNA damage involves phosphorylation of MDMX followed by release of p53. Successful targeting of the p53 pathway for cancer therapy requires understanding how MDMX regulates p53 function. MDMX contains an ordered p53 binding domain and RING domain, and two long disordered regions that regulate p53 and CK1α binding in a phosphorylation- dependent manner. Our work identified intra- and intermolecular interactions essential for MDMX functions: (1) MDMX/p53 interaction inhibits p53 DNA binding. (2) MDMX/MDM2 interaction promotes MDMX degradation. (3) MDMX/14-3-3 interaction promotes MDMX nuclear translocation. (4) MDMX/CK1α interaction promotes MDMX/p53 binding and inhibition of p53. (5) MDMX intramolecular interaction regulates p53 binding. Importantly, these interactions are regulated by two phosphorylation sites (S289, S367) located in intrinsically disordered regions (IDR) of MDMX. We hypothesize that the coordinated control is mediated by intramolecular interactions between ordered and disordered regions of MDMX. The IDRs regulate the switching of intra/inter-molecular contacts in a phosphorylation-dependent manner. We propose integrated molecular biology and biophysics approach to elucidate the mechanism of MDMX regulation: (1) Determine how the length and flexibility of MDMX IDR1 regulates auto- inhibition of p53 binding. (2) Investigate how CK1α phosphorylation switches MDMX to an open conformation that inhibits p53 DNA binding. (3) Determine how Chk2 phosphorylation of IDR2 S367 regulates multiple MDMX interactions. These experiments will significantly advance the understanding of how stress signals activate p53 by targeting disordered regions of MDMX, which is essential to develop MDMX inhibitors for cancer therapy.