Ubiquitin Isopeptidase Inhibitor I, G5 (NSC 144303)是凋亡不依赖的半胱天冬酶和细胞凋亡的激活剂，对E1A和E1A/C9DN细胞的IC50值分别为1.76和1.6 μM A cell-permeable cross-conjugated α,β-unsaturated dienone compound that induces caspase activation and apoptosis (IC50 = 1.76 and 1.6 µM in E1A and E1A/C9DN cells, respectively) via the apoptosome-independent mitochondrial pathway by selectively inhibiting ubiquitin isopeptidase activity (IC50 ~30 µM). The cellular expression of Bax and Bak is essential for G5-activated apoptosis, while Bcl-2 appears to protect cells against the effect of G5. G5 is more potent than, but otherwise exhibits similar pharmacological effects as, Ubiquitin Isopeptidase Inhibitor II, F6. At higher concentrations (5-10 µM), shown to induce necrosis in apoptosis-resistant MEFs-DKO. A cell-permeable cross-conjugated α,β-unsaturated dienone compound that induces caspase activation and apoptosis (IC50 = 1.76 and 1.6 µM in E1A and E1A/C9DN cells, respectively) via the apoptosome-independent mitochondrial pathway by selectively inhibiting ubiquitin isopeptidase activity (IC50 = ~ 30 µM). The cellular expression of Bax and Bak is essential for G5-activated apoptosis, while Bcl-2 appears to protect cells against the effect of G5. G5 is more potent than, but otherwise exhibits similar pharmacological effects as, Ubiquitin Isopeptidase Inhibitor II, F6 . At higher concentrations (5-10 µM), shown to induce necrosis in apoptosis-resistant MEFs-DKO.