Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Pl, Memphis, TN, 38105, USA.
Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, 262 Danny Thomas Pl, Memphis, TN, 38105, USA.
Nat Commun. 2020 Oct 1;11(1):4931. doi: 10.1038/s41467-020-18708-x.
Testis-restricted melanoma antigen (MAGE) proteins are frequently hijacked in cancer and play a critical role in tumorigenesis. MAGEs assemble with E3 ubiquitin ligases and function as substrate adaptors that direct the ubiquitination of novel targets, including key tumor suppressors. However, how MAGEs recognize their targets is unknown and has impeded the development of MAGE-directed therapeutics. Here, we report the structural basis for substrate recognition by MAGE ubiquitin ligases. Biochemical analysis of the degron motif recognized by MAGE-A11 and the crystal structure of MAGE-A11 bound to the PCF11 substrate uncovered a conserved substrate binding cleft (SBC) in MAGEs. Mutation of the SBC disrupted substrate recognition by MAGEs and blocked MAGE-A11 oncogenic activity. A chemical screen for inhibitors of MAGE-A11:substrate interaction identified 4-Aminoquinolines as potent inhibitors of MAGE-A11 that show selective cytotoxicity. These findings provide important insights into the large family of MAGE ubiquitin ligases and identify approaches for developing cancer-specific therapeutics.
组织特异性黑素瘤抗原（MAGE）蛋白在癌症中经常被劫持，在肿瘤发生中起着关键作用。MAGE 与 E3 泛素连接酶组装，并作为底物衔接物发挥作用，可将新的靶标（包括关键的肿瘤抑制因子）泛素化。然而，MAGE 如何识别其靶标尚不清楚，这阻碍了 MAGE 导向治疗的发展。在这里，我们报告了 MAGE 泛素连接酶识别底物的结构基础。通过 MAGE-A11 识别的降解基序的生化分析和 MAGE-A11 与 PCF11 底物结合的晶体结构揭示了 MAGE 中的保守底物结合裂隙（SBC）。SBC 的突变破坏了 MAGE 对底物的识别，并阻断了 MAGE-A11 的致癌活性。对 MAGE-A11：底物相互作用的化学筛选鉴定出 4-氨基喹啉类化合物是 MAGE-A11 的有效抑制剂，对 MAGE-A11 具有选择性细胞毒性。这些发现为大量 MAGE 泛素连接酶提供了重要的见解，并确定了开发癌症特异性治疗方法的途径。
