HIV-I Vpr activates the G2 checkpoint through manipulation of the ubiquitin proteasome system
HIV-I Vpr activates the G2 checkpoint through manipulation of the ubiquitin proteasome system
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DOI：
10.1186/1743-422x-4-57
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发表时间：
2007-06-08
期刊：
影响因子：
4.8
通讯作者：
Planelles, Vicente
中科院分区：
文献类型：
--
作者：
DeHart, Jason L.;Zimmerman, Erik S.;Planelles, Vicente
HIV- 1 Vpr是一种通过诱导DNA复制应激激活ATR的病毒辅助蛋白。ATR激活导致G(2)细胞周期阻滞和诱导凋亡。在本研究中，我们研究了泛素/蛋白酶体系统（UPS）在上述Vpr活性中的作用。我们报道了UPS的一般功能是Vpr诱导G2检查点激活所必需的，因为用蛋白酶体抑制剂孵育表达Vpr的细胞可以消除这种作用。我们进一步详细研究了Vpr操纵的特定E3泛素连接酶亚基。我们发现Vpr与cullin 4a/ DDB1 E3泛素连接酶的DCAF1亚基结合。羧基末端结构域Vpr（R80A）突变体能够结合DCAF1，在检查点激活中不活跃，具有显性阴性特征。相比之下，突变Q65R，在Vpr的亮氨酸富集区域介导DCAF1结合，导致无活性Vpr缺乏显性负性行为。因此，Vpr与DCAF1的相互作用是导致G2阻滞的必要条件，但不是充分条件。我们认为Vpr通过其羧基末端结构域，招募了一种未知的细胞因子，这是G(2)-到- M转变所必需的。
HIV- 1 Vpr is a viral accessory protein that activates ATR through the induction of DNA replication stress. ATR activation results in cell cycle arrest in G(2) and induction of apoptosis. In the present study, we investigate the role of the ubiquitin/ proteasome system ( UPS) in the above activity of Vpr. We report that the general function of the UPS is required for Vpr to induce G2 checkpoint activation, as incubation of Vpr- expressing cells with proteasome inhibitors abolishes this effect. We further investigated in detail the specific E3 ubiquitin ligase subunits that Vpr manipulates. We found that Vpr binds to the DCAF1 subunit of a cullin 4a/ DDB1 E3 ubiquitin ligase. The carboxyterminal domain Vpr( R80A) mutant, which is able to bind DCAF1, is inactive in checkpoint activation and has dominant- negative character. In contrast, the mutation Q65R, in the leucine- rich domain of Vpr that mediates DCAF1 binding, results in an inactive Vpr devoid of dominant negative behavior. Thus, the interaction of Vpr with DCAF1 is required, but not sufficient, for Vpr to cause G2 arrest. We propose that Vpr recruits, through its carboxy terminal domain, an unknown cellular factor that is required for G(2)- to- M transition.