Center for Systems Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G1X5, Canada.
Cell. 2011 Jun 24;145(7):1075-87. doi: 10.1016/j.cell.2011.05.039. Epub 2011 Jun 16.
In the ubiquitin-proteasome system (UPS), E2 enzymes mediate the conjugation of ubiquitin to substrates and thereby control protein stability and interactions. The E2 enzyme hCdc34 catalyzes the ubiquitination of hundreds of proteins in conjunction with the cullin-RING (CRL) superfamily of E3 enzymes. We identified a small molecule termed CC0651 that selectively inhibits hCdc34. Structure determination revealed that CC0651 inserts into a cryptic binding pocket on hCdc34 distant from the catalytic site, causing subtle but wholesale displacement of E2 secondary structural elements. CC0651 analogs inhibited proliferation of human cancer cell lines and caused accumulation of the SCF(Skp2) substrate p27(Kip1). CC0651 does not affect hCdc34 interactions with E1 or E3 enzymes or the formation of the ubiquitin thioester but instead interferes with the discharge of ubiquitin to acceptor lysine residues. E2 enzymes are thus susceptible to noncatalytic site inhibition and may represent a viable class of drug target in the UPS.
在泛素-蛋白酶体系统（UPS）中，E2 酶介导泛素与底物的连接，从而控制蛋白质稳定性和相互作用。E2 酶 hCdc34 与 cullin-RING（CRL）E3 酶超家族一起催化数百种蛋白质的泛素化。我们鉴定了一种称为 CC0651 的小分子，它选择性地抑制 hCdc34。结构测定表明，CC0651 插入 hCdc34 远离催化位点的隐蔽结合口袋，导致 E2 二级结构元件的细微但整体位移。CC0651 类似物抑制人类癌细胞系的增殖，并导致 SCF（Skp2）底物 p27（Kip1）的积累。CC0651 不影响 hCdc34 与 E1 或 E3 酶的相互作用，也不影响泛素硫酯的形成，而是干扰泛素向受体赖氨酸残基的释放。因此，E2 酶易受非催化位点抑制，并且可能是 UPS 中可行的药物靶标类别。
