p21Cip1（p21）是一种通用的细胞周期蛋白依赖性激酶（CDK）抑制剂，通过多种机制阻止细胞增殖和肿瘤生长。p21的表达在癌细胞中经常由于转录激活剂（如p53）的失去功能或蛋白质降解速率的增加而下调。为了寻找通过阻止p21泛素介导降解的小分子作为癌症药物研发的未来途径，我们使用细胞报告者试验筛选了一个化合物库，以检测p21的降解。这导致发现了苯二氮平系列的分子，这些分子可以在细胞中诱导p21的积累。使用一种化学蛋白质策略，我们确定了这种苯二氮平系列的化合物的细胞靶标为泛素结合酶UBCH10。我们展示了一种经过优化的苯二氮平类似物可以抑制UBCH10的泛素结合活性和前期促进复合物对底物的蛋白质降解。

p21Cip1 (p21) is a universal cyclin-dependent kinase (CDK) inhibitor that halts cell proliferation and tumor growth by multiple mechanisms. The expression of p21 is often downregulated in cancer cells as a result of the loss of function of transcriptional activators, such as p53, or the increased degradation rate of the protein. To identify small molecules that block the ubiquitin-mediated degradation of p21 as a future avenue for cancer drug discovery, we have screened a compound library using a cell-based reporter assay of p21 degradation. This led to the identification of a benzodiazepine series of molecules that induce the accumulation of p21 in cells. Using a chemical proteomic strategy, we identified the ubiquitin-conjugating enzyme UBCH10 as a cellular target of this benzodiazepine series. We show that an optimized benzodiazepine analogue inhibits UBCH10 ubiquitin-conjugating activity and substrate proteolysis by the anaphase-promoting complex.