National Research Laboratory for Metabolic Checkpoint, Departments of Biomedical Sciences and Biochemistry and Molecular Biology, Cancer Research Institute, Seoul National University College of Medicine, Republic of Korea.
Oncogene. 2011 Jul 14;30(28):3127-38. doi: 10.1038/onc.2011.40. Epub 2011 Feb 28.
Germline mutations in the von Hippel-Lindau (VHL) tumor suppressor gene cause VHL disease, a rare and autosomal-dominant genetic syndrome. Because VHL protein (pVHL) is the master regulator of hypoxia-inducible factor alpha (HIFα), the most prominent feature of VHL disease is the deregulation of HIFα proteins. However, the precise mechanism by which the loss of pVHL function contributes to tumorigenesis is not fully understood. Here, we show that pVHL destabilizes the F-box protein Skp2, a chief component of Skp, Cullin, F-box-containing complex that promotes DNA synthesis in the S phase. The β-domain of pVHL interacts with Skp2, stimulating proteasome-dependent Skp2 degradation, but the destabilization of Skp2 does not depend on the E3 ubiquitin ligase activity of pVHL. Notably, the generation of DNA damage induces Skp2 degradation, which is attenuated by the suppression of endogenous pVHL expression. One possible mechanism of pVHL-dependent Skp2 degradation entails the antagonizing of Akt-mediated Skp2 phosphorylation, which maintains Skp2 stability. Reintroduction of VHL into VHL-null renal cell carcinoma (RCC) cells decreased Skp2 levels and restored DNA damage-dependent Skp2 degradation. These results identify the tumor suppressor function of pVHL in delaying the S-phase progression to inhibit cell proliferation on DNA damage. Clinically, this report explains as to why Skp2 accumulates abnormally in RCC tissues.
胚系突变 von Hippel-Lindau（VHL）肿瘤抑制基因导致 VHL 病，这是一种罕见的常染色体显性遗传综合征。由于 VHL 蛋白（pVHL）是缺氧诱导因子α（HIFα）的主要调节因子，VHL 病的最显著特征是 HIFα 蛋白的失调。然而，pVHL 功能丧失如何促进肿瘤发生的精确机制尚不完全清楚。在这里，我们表明 pVHL 使 F-box 蛋白 Skp2 不稳定，Skp2 是 Skp、Cullin、F-box 含有复合物的主要成分，该复合物促进 S 期的 DNA 合成。pVHL 的β结构域与 Skp2 相互作用，刺激蛋白酶体依赖的 Skp2 降解，但 Skp2 的不稳定性不依赖于 pVHL 的 E3 泛素连接酶活性。值得注意的是，DNA 损伤的产生诱导 Skp2 降解，而内源性 pVHL 表达的抑制会减弱这种降解。pVHL 依赖性 Skp2 降解的一种可能机制涉及 Akt 介导的 Skp2 磷酸化的拮抗，该磷酸化维持 Skp2 的稳定性。将 VHL 重新引入 VHL 缺失的肾细胞癌（RCC）细胞中，降低了 Skp2 水平，并恢复了 DNA 损伤依赖性 Skp2 降解。这些结果确定了 pVHL 在延迟 S 期进展以抑制细胞增殖方面的肿瘤抑制功能。临床上，这一报告解释了为什么 Skp2 在 RCC 组织中异常积累。
