Department of Microbiology and Abramson Comprehensive Cancer Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America.
PLoS One. 2010 Sep 9;5(9):e12636. doi: 10.1371/journal.pone.0012636.
Functional inactivation of the von Hippel-Lindau (VHL) tumor suppressor protein is linked to the development of several forms of cancer as well as oncogenic progression like sporadic renal clear-cell carcinomas (RCC). Despite the critical role played by VHL in destruction of hypoxia-inducible factor α (HIFα) via ubiquitin-mediated proteolysis, very little is known about the post-translational modification which regulates VHL activity. Our previous study showed that the SUMO E3 ligase PIASy interacts with VHL and induces VHL SUMOylation on lysine residue 171 (Cai et al, PLoS ONE, 2010, 5(3):e9720). Here we further report that VHL also undergoes ubiquitylation on both lysine residues 171 and 196, which is blocked by PIASy. Moreover, using a VHL-SUMO1 or ubiquitin fusion protein, we found that ubiquitylated VHL is localized predominantly in the cytoplasm, while SUMOylated VHL results in increased VHL protein stability and nuclear redistribution. Interestingly, substitution of lysine 171 and 196 to arginine of VHL abrogates its inhibitory function on the transcriptional activity of HIFα, and tube formation in vitro. This demonstrates that post-translational modifications like ubiquitylation and SUMOylation contributes to VHL protein stability and nucleocytoplasmic shuttling, and that the overall function of VHL in tumor suppression may require a precise and dynamically regulated process which involves protein modification.
功能失活的 von Hippel-Lindau（VHL）肿瘤抑制蛋白与几种癌症的发展以及散发性肾透明细胞癌（RCC）等致癌进展有关。尽管 VHL 在通过泛素介导的蛋白水解破坏缺氧诱导因子α（HIFα）方面发挥着关键作用，但对于调节 VHL 活性的翻译后修饰知之甚少。我们之前的研究表明，SUMO E3 连接酶 PIASy 与 VHL 相互作用，并诱导 VHL 在赖氨酸残基 171 上的 SUMO 化（Cai 等人， PLoS ONE，2010 年，5（3）：e9720）。在这里，我们进一步报告 VHL 还在赖氨酸残基 171 和 196 上发生泛素化，PIASy 会阻止这种泛素化。此外，使用 VHL-SUMO1 或泛素融合蛋白，我们发现泛素化的 VHL 主要定位于细胞质中，而 SUMO 化的 VHL 导致 VHL 蛋白稳定性增加和核重新分布。有趣的是，VHL 的赖氨酸 171 和 196 突变为精氨酸会使其抑制 HIFα 转录活性和体外管形成的功能丧失。这表明翻译后修饰（如泛素化和 SUMO 化）有助于 VHL 蛋白稳定性和核质穿梭，而 VHL 在肿瘤抑制中的整体功能可能需要一个精确和动态调节的过程，其中涉及蛋白质修饰。
