The Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK.
Carcinogenesis. 2012 Apr;33(4):791-8. doi: 10.1093/carcin/bgs092. Epub 2012 Feb 2.
p53 is a tumor suppressor that responds to a variety of stresses such as oncogenes and DNA damage by activating its transcriptional targets to allow repair or elimination of damaged cells. In the absence of stress signals, p53 needs to be kept in check and this is achieved by the E3 ligase MDM2. For tumors that retain wild-type p53, therapeutic strategies aimed at removing the inhibitory activity of MDM2 on p53 are under development and to date have focused on drugs that prevent the binding of p53 to MDM2. Here, we report the analysis of a group of synthetic analogs derived from 5-deazaflavin compounds previously identified in a screen as inhibitors of MDM2 autoubiquitination. Using measurement of surface plasmon resonance, we demonstrated that active 5-deazaflavin analogs bind to the MDM2 RING, whereas inactive compounds show no binding. In cellular assays, these active MDM2 RING binding compounds inhibited the ubiquitination of p53, stabilized p53, led to increased expression of p53 targets and caused corresponding cell cycle effects. Deazaflavin analogs therefore function to activate p53 through a novel mechanism, by inhibiting the E3 ligase activity of MDM2 in a manner that involves binding to the MDM2 RING.
p53 是一种肿瘤抑制因子，它通过激活其转录靶标来应对各种应激，如癌基因和 DNA 损伤，从而允许受损细胞的修复或消除。在没有应激信号的情况下，p53 需要受到抑制，这是通过 E3 连接酶 MDM2 实现的。对于保留野生型 p53 的肿瘤，旨在消除 MDM2 对 p53 的抑制活性的治疗策略正在开发中，迄今为止，这些策略主要集中在防止 p53 与 MDM2 结合的药物上。在这里，我们报告了一组源自先前在筛选中被鉴定为 MDM2 自泛素化抑制剂的 5-脱氮黄素化合物的合成类似物的分析。通过表面等离子体共振测量，我们证明了活性 5-脱氮黄素类似物与 MDM2 RING 结合，而失活化合物则没有结合。在细胞测定中，这些活性的 MDM2 RING 结合化合物抑制了 p53 的泛素化，稳定了 p53，导致 p53 靶标表达增加，并引起相应的细胞周期效应。因此，脱氮黄素类似物通过一种新的机制激活 p53，通过抑制 MDM2 的 E3 连接酶活性，以涉及与 MDM2 RING 结合的方式。
