Epstein-Barr virus latent antigen 3C can mediate the degradation of the retinoblastoma protein through an SCF cellular ubiquitin ligase
Epstein-Barr virus latent antigen 3C can mediate the degradation of the retinoblastoma protein through an SCF cellular ubiquitin ligase
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DOI：
10.1073/pnas.0503886102
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发表时间：
2005-12-20
影响因子：
11.1
通讯作者：
Robertson, ES
中科院分区：
文献类型：
--
作者：
Knight, JS;Sharma, N;Robertson, ES
EB病毒（EBV）刺激潜伏感染的B细胞的增殖并促进人类淋巴恶性肿瘤。为了阐明EB病毒潜伏蛋白EB核抗原3C（EBNA 3C）在视网膜母细胞瘤蛋白（Rb）调节中的作用，我们将EBNA 3C转染到293、BJAB和SAOS-2细胞中。在这种情况下，EBNA 3C的主要作用是降低Rb蛋白水平。EBNA 3C还拯救Rb-included扁平细胞表型和目标Rb蛋白酶体和泛素依赖性降解。此外，当蛋白酶体机制被抑制时，EBNA 3C在细胞中与Rb形成稳定的复合物，并在体外与Rb相互作用，映射到EBNA 3C末端的保守结构域。EBNA 3C的缺失分析鉴定了对Rb的结合和调节都重要的氨基酸140-149内的基序。这个基序特别令人感兴趣，因为它也与Skp 1/Cul 1/F-box复合物SCFSkp 2的调节有关。事实上，用显性负性分子抑制Skp 2功能会降低EBNA 3C降解Rb的能力。在EBNA 3C不存在的情况下，Skp 2对Rb水平没有可检测的影响，这表明SCFSkp 2被EBNA 3C特异性地篡夺以增强Rb降解。EBNA 3C已经利用了这种关联，这表明其他人类恶性肿瘤可能使用类似的策略来调节Rb蛋白。
Epstein-Barr virus (EBV) stimulates the proliferation of latently infected B cells and promotes lymphoid malignancies in humans. To address the role of EBV latency protein Epstein-Barr nuclear antigen 3C [EBNA3C) in regulation of the retinoblastoma protein (Rb), we transfected EBNA3C into 293, BJAB, and SAOS-2 cells. In this context, a dominant effect of EBNA3C is to decrease Rb protein levels. EBNA3C also rescues an Rb-incluced flat cell phenotype and targets Rb for proteasome- and ubiquitin-dependent degradation. Further, EBNA3C forms a stable complex with Rb in cells when the proteasome machinery is inhibited and interacts with Rb in vitro, mapping to a conserved domain at the terminus of EBNA3C. Deletion analysis of EBNA3C identified a motif within amino acids 140-149 important for both the binding and regulation of Rb. This motif is of particular interest, because it has also been linked to regulation of the Skp1/Cul1/F-box complex, SCFSkp2. Indeed, inhibition of Skp2 function with a dominant-negative molecule reduces the ability of EBNA3C to degrade Rb. Skp2 has no detectable effect on Rb levels in the absence of EBNA3C, suggesting that SCFSkp2 is specifically usurped by EBNA3C for the enhancement of Rb degradation. That EBNA3C has exploited this association suggests that other human malignancies might use a similar strategy to regulate the Rb protein.