Department of Dermatology and Skin Science, Jack Bell Research Centre, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V6H 3Z6.
Oncogene. 2010 Mar 11;29(10):1498-508. doi: 10.1038/onc.2009.424. Epub 2009 Nov 23.
The inhibitor of growth family member 3 (ING3) has been shown to modulate transcription, cell cycle control and apoptosis. We previously reported that nuclear ING3 expression was remarkably reduced in melanomas, which correlated with a poorer patient survival, suggesting that decreased ING3 expression may be associated with melanoma progression. However, the mechanism of diminished ING3 expression in melanoma is not clear. Here we show that ING3 level was decreased in metastatic melanoma cells because of a rapid degradation. Furthermore, we showed that ING3 undergoes degradation through the ubiquitin-proteasome pathway. ING3 physically interacts with subunits of E3 ligase Skp1-Cullin-F-box protein complex (SCF complex). Knockdown of F-box protein S-phase kinase-associated protein 2 (Skp2) reduces the ubiquitination of ING3 and significantly stabilizes ING3 in melanoma cells. In addition, lysine 96 residue is essential for ING3 ubiquitination as its mutation to arginine dramatically abrogated ING3 degradation. Disruption of ING3 degradation stimulated ING3-induced G1 cell-cycle arrest and enhanced ultraviolet-induced apoptosis. Taken together, our data show that ING3 is degraded by the ubiquitin-proteasome pathway through the SCF(Skp2) complex and interruption of ING3 degradation enhances the tumor-suppressive function of ING3, which provides a potential cancer therapeutic approach by interfering ING3 degradation.
生长抑制因子家族成员 3（ING3）已被证明可以调节转录、细胞周期控制和细胞凋亡。我们之前的研究报告显示，核 ING3 表达在黑色素瘤中显著降低，这与患者生存预后较差相关，表明 ING3 表达的降低可能与黑色素瘤的进展有关。然而，黑色素瘤中 ING3 表达减少的机制尚不清楚。在这里，我们发现由于快速降解，转移性黑色素瘤细胞中的 ING3 水平降低。此外，我们发现 ING3 通过泛素蛋白酶体途径进行降解。ING3 与 E3 连接酶 Skp1-Cullin-F-box 蛋白复合物（SCF 复合物）的亚基相互作用。F-box 蛋白 S 期激酶相关蛋白 2（Skp2）的敲低减少了 ING3 的泛素化，并显著稳定了黑色素瘤细胞中的 ING3。此外，赖氨酸 96 残基对于 ING3 的泛素化是必需的，因为将其突变为精氨酸可显著阻止 ING3 的降解。ING3 降解的破坏刺激了 ING3 诱导的 G1 细胞周期停滞，并增强了紫外线诱导的细胞凋亡。总之，我们的数据表明，ING3 通过 SCF（Skp2）复合物被泛素蛋白酶体途径降解，而 ING3 降解的中断增强了 ING3 的肿瘤抑制功能，通过干扰 ING3 降解为癌症治疗提供了一种潜在的方法。
