Kaposi's Sarcoma-Associated Herpesvirus RTA Promotes Degradation of the Hey1 Repressor Protein through the Ubiquitin Proteasome Pathway
Kaposi's Sarcoma-Associated Herpesvirus RTA Promotes Degradation of the Hey1 Repressor Protein through the Ubiquitin Proteasome Pathway
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DOI：
10.1128/jvi.00351-09
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发表时间：
2009-07-01
影响因子：
5.4
通讯作者：
Whitehouse, Adrian
中科院分区：
文献类型：
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作者：
Gould, Faye;Harrison, Sally M.;Whitehouse, Adrian
卡波西肉瘤相关疱疹病毒（KSHV）复制和转录激活因子（RTA）蛋白通过反式激活多种KSHV裂解和细胞启动子来调节潜伏裂解开关。RTA是一种新型的E3泛素连接酶，其通过泛素蛋白酶体途径靶向许多转录抑制蛋白进行降解。在这里，我们表明，RTA与细胞转录抑制蛋白Hey1相互作用。我们证明，Hey1是RTA介导的泛素化的目标，随后被蛋白酶体降解。此外，RTA内富含Cys + His的区域对于RTA介导的Hey1降解是重要的。我们证实，Hey1抑制RTA启动子，而且，表明Hey1结合RTA启动子。Hey1和辅阻遏物mSin3A之间观察到相互作用，并且这种相互作用在RTA的存在下被消除。此外，mSin3A与RTA启动子在nonreactivated，但不重新激活，BCBL1细胞。在HEK 293T细胞中，用重组病毒rKSHV.219潜伏感染的Hey1的小干扰RNA敲低导致再活化后RTA表达水平增加，但不足以诱导完全裂解性再活化。这些结果表明，其他额外的转录抑制因子在维持KSHV潜伏期也很重要。两者合计，我们的研究结果表明，Hey1在维持KSHV潜伏期中起着重要作用，并且通过RTA靶向降解破坏Hey1阻遏体可能是调节裂解再激活机制的一个步骤。
The Kaposi's sarcoma-associated herpesvirus (KSHV) replication and transcription activator (RTA) protein regulates the latent-lytic switch by transactivating a variety of KSHV lytic and cellular promoters. RTA is a novel E3 ubiquitin ligase that targets a number of transcriptional repressor proteins for degradation by the ubiquitin proteasome pathway. Herein, we show that RTA interacts with the cellular transcriptional repressor protein Hey1. We demonstrate that Hey1 is a target for RTA-mediated ubiquitination and is subsequently degraded by the proteasome. Moreover, a Cys-plus-His-rich region within RTA is important for RTA-mediated degradation of Hey1. We confirm that Hey1 represses the RTA promoter and, furthermore, show that Hey1 binds to the RTA promoter. An interaction was observed between Hey1 and the corepressor mSin3A, and this interaction was abolished in the presence of RTA. Additionally, mSin3A associated with the RTA promoter in nonreactivated, but not reactivated, BCBL1 cells. Small interfering RNA knockdown of Hey1 in HEK 293T cells latently infected with the recombinant virus rKSHV.219 led to increased levels of RTA expression upon reactivation but was insufficient to induce complete lytic reactivation. These results suggest that other additional transcriptional repressors are also important in maintenance of KSHV latency. Taken together, our results suggest that Hey1 has a contributory role in the maintenance of KSHV latency and that disruption of the Hey1 repressosome by RTA-targeted degradation may be one step in the mechanism to regulate lytic reactivation.