Versatile functions of LANA in KSHV pathogenesis

 描述（由申请人提供）：本申请由中国科学院上海巴斯德研究所的研究者提交。中国，是为了响应PAR-14-080“国际传染病研究，包括艾滋病（R 01）”而提交的。沿着HIV感染，KSHV和KS已成为世界范围内的重要健康问题。KSHV相关肿瘤在HIV人群中的发病率增加引起了国际关注，特别是在欠发达国家，如中国。对KSHV诱导肿瘤发生机制的研究将提供新的治疗靶点。在KS病变中，大多数肿瘤细胞被KSHV潜伏感染，并表达病毒表达。 潜伏相关核抗原（拉娜）等蛋白质，提示病毒潜伏感染在肿瘤发生中的重要作用。利用串联亲和纯化（TAP）技术，我们鉴定了一种新的LANA结合蛋白Krüppel相关盒结构域相关蛋白1（KAP 1）。KAP 1是一种转录抑制因子，可以通过募集组蛋白脱乙酰酶和甲基转移酶复合物来改变表观遗传状态。我们以前发现，拉娜招募KAP 1的RTA启动子区域的KSHV基因组，这是参与转录抑制RTA的拉娜。由于KAP 1是一个重要的转录辅阻遏物，我们假设拉娜是能够通过与KAP 1的相互作用来调节全球宿主基因的表达。在这个项目中，我们将确定拉娜是否以及如何通过下调细胞肿瘤抑制基因的表达来促进KSHV感染细胞的促增殖基因签名。另一方面，我们前期的研究表明，拉娜通过持续BMP激活的p-Smad 1在核内上调BMP-Smad 1-Id信号传导，并增强其对BMP靶基因Id启动子的负载。我们发现Id蛋白在KSHV转化的KMM细胞中显著上调，并在人KS病变中大量表达。引人注目的是，BMP-Smad 1-Id通路的遗传抑制在体外和体内显著阻断了KSHV转化细胞的致癌表型。有趣的是，Id蛋白在胚胎发生和肿瘤形成期间的血管生成中也起关键作用。因此，我们建议确定拉娜是否调节BMP-Smad 1-Id信号通路以促进肿瘤血管生成，因为丰富的血管生成是KS的特征，并且是KS进展的关键因素。此外，我们还将确定拉娜如何调节BMP诱导的p-Smad 1激活的终止过程以及Id蛋白促进KMM细胞血管生成表型的机制。最后，我们将使用各种BMP信号传导抑制剂来评估它们对肿瘤发生和促血管生成的抑制效果。 KMM细胞的表型。通过我们的研究，我们希望揭示有关拉娜在KSHV相关恶性肿瘤中的多功能的新见解。

 DESCRIPTION (provided by applicant): This application by investigators at the Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, P.R. China, is submitted in response to PAR-14-080 'International Research in Infectious Diseases, including AIDS (R01)'. Along with HIV infection, KSHV and KS have emerged as an important health problem worldwide. The increase in incidence of KSHV-associated tumors in the HIV population is of international concern especially in under-developed countries, such as China. Studies towards the elucidation of the mechanism for KSHV-induced tumorigenesis will provide new therapeutic targets. In KS lesions, the majority of tumor cells are latently infected by KSHV and express viral proteins such as latency associated nuclear antigen (LANA), suggesting an essential role for viral latent infection in tumorigenesis. Using tandem affinity purification (TAP) technology, we identified Krüppel associated box domain associated protein-1 (KAP1) as a novel LANA-binding protein. KAP1 functions as a transcriptional repressor and can change epigenetic state by recruiting histone deacetylase and methyltransferase complex. We previously showed that LANA recruited KAP1 to the RTA promoter region of the KSHV genome, which was involved in transcriptional repression of RTA by LANA. Since KAP1 is an important transcription corepressor, we hypothesize that LANA is capable of regulating global host gene expression through interaction with KAP1. In this project, we will determine whether and how LANA contributes to the pro-proliferative gene signature of KSHV infected cell by down-regulating expression of cellular tumor repressor genes. On the other hand, our previous studies showed that LANA up-regulated BMP-Smad1-Id signaling through sustained BMP-activated p-Smad1 in the nucleus and enhanced its loading on the promoter of BMP target gene Id. We showed that Id proteins were significantly up-regulated in KSHV transformed KMM cells and abundantly expressed in human KS lesions. Strikingly, genetic inhibition of the BMP-Smad1-Id pathway significantly blocked the oncogenic phenotype of KSHV-transformed cells in vitro and in vivo. Interestingly, Id proteins also play critical roles in angiogenesis both during embryogenesis and tumor formation. Thus, we proposed to determine whether LANA modulates BMP-Smad1-Id signaling to facilitate tumor angiogenesis, since abundant angiogenesis is the feature of KS and is the key factor for KS progress. Moreover, we will also determine how LANA regulates the termination process of BMP-induced p-Smad1 activation and the mechanisms by which of Id proteins contribute to angiogenic phenotype of KMM cells. Finally, we will use various BMP signaling inhibitors to evaluate their inhibition efficacy on the tumorigenicity and pro-angiogenic phenotype of KMM cells. Through our studies, we expect to reveal novel insights onto the versatile functions of LANA in KSHV-related malignancies.