EBNA3C augments Pim-1 mediated phosphorylation and degradation of p21 to promote B-cell proliferation.
EBNA3C augments Pim-1 mediated phosphorylation and degradation of p21 to promote B-cell proliferation.
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DOI：
10.1371/journal.ppat.1004304
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发表时间：
2014-08
期刊：
影响因子：
6.7
通讯作者：
Robertson ES
中科院分区：
文献类型：
--
作者：
Banerjee S;Lu J;Cai Q;Sun Z;Jha HC;Robertson ES
EB病毒（Epstein-Barr virus，EBV）是一种广泛存在的人类疱疹病毒，可潜伏感染人类。EBV与几种类型的恶性肿瘤有关，这些恶性肿瘤起源于淋巴细胞和上皮细胞类型。EBV潜伏抗原3C（EBNA 3C）是EBV诱导的B细胞永生化所必需的。编码致癌丝氨酸/苏氨酸激酶的莫洛尼鼠白血病前病毒整合位点（PIM-1）与涉及细胞存活、增殖、分化和凋亡的几种细胞功能相关。值得注意的是，Pim-1激酶的表达增强与许多血液学和非血液学恶性肿瘤相关。Pim-1激酶的高表达水平与EBV感染相关，表明Pim-1在EBV诱导的肿瘤发生中起关键作用。我们现在证明了一种分子机制，揭示了EBNA 3C在增强EBV感染的原代B细胞中Pim-1表达中的直接作用。我们还发现EBNA 3C通过其氨基末端结构域与Pim-1物理相关，并且还在B细胞中形成分子复合物。EBNA 3C可以通过废除蛋白酶体/泛素途径来稳定Pim-1。我们的结果表明EBNA 3C增强Pim-1介导的p21在Thr 145残基的磷酸化。EBNA 3C还促进Pim-1的核定位，并通过改变Pim-1介导的细胞周期抑制剂p21/WAF 1的活性调节来促进EBV转化的细胞增殖。我们的研究表明，EBNA 3C显著诱导Pim-1介导的p21蛋白体降解。在稳定敲除Pim-1后，观察到EBV转化的LCL的细胞增殖显著降低。这项研究描述了癌蛋白Pim-1在EBV介导的肿瘤发生中的关键作用，并为EBV相关癌症的致癌激酶靶向治疗干预提供了新的见解。致癌丝氨酸/苏氨酸激酶Pim-1在许多人类癌症中上调，包括淋巴瘤、胃癌、结肠直肠癌和前列腺癌。EBV核抗原3C（EBNA 3C）是EBV诱导的人原代B淋巴细胞转化所必需的。我们目前的研究表明，EBNA 3C显着增强Pim-1激酶的表达在转录和蛋白质水平。EBNA 3C还与Pim-1相互作用，并可在EBV转化细胞中形成复合物。此外，EBNA 3C增加Pim-1的核定位，并通过抑制其多聚泛素化来稳定Pim-1蛋白水平。此外，EBNA 3C增强Pim-1介导的p21磷酸化及其蛋白体降解。使用si-RNA稳定敲除Pim-1显示EBV转化的淋巴母细胞样细胞系的增殖显著降低，随后通过触发内在凋亡途径诱导凋亡。因此，我们的研究证明了一种新的机制，通过这种机制，EBV潜伏抗原3C靶向的致癌Pim-1激酶可以抑制p21功能，因此是治疗EBV相关恶性肿瘤的潜在治疗靶点。
Epstein–Barr virus (EBV), a ubiquitous human herpesvirus, can latently infect the human population. EBV is associated with several types of malignancies originating from lymphoid and epithelial cell types. EBV latent antigen 3C (EBNA3C) is essential for EBV-induced immortalization of B-cells. The Moloney murine leukemia provirus integration site (PIM-1), which encodes an oncogenic serine/threonine kinase, is linked to several cellular functions involving cell survival, proliferation, differentiation, and apoptosis. Notably, enhanced expression of Pim-1 kinase is associated with numerous hematological and non-hematological malignancies. A higher expression level of Pim-1 kinase is associated with EBV infection, suggesting a crucial role for Pim-1 in EBV-induced tumorigenesis. We now demonstrate a molecular mechanism which reveals a direct role for EBNA3C in enhancing Pim-1 expression in EBV-infected primary B-cells. We also showed that EBNA3C is physically associated with Pim-1 through its amino-terminal domain, and also forms a molecular complex in B-cells. EBNA3C can stabilize Pim-1 through abrogation of the proteasome/Ubiquitin pathway. Our results demonstrate that EBNA3C enhances Pim-1 mediated phosphorylation of p21 at the Thr145 residue. EBNA3C also facilitated the nuclear localization of Pim-1, and promoted EBV transformed cell proliferation by altering Pim-1 mediated regulation of the activity of the cell-cycle inhibitor p21/WAF1. Our study demonstrated that EBNA3C significantly induces Pim-1 mediated proteosomal degradation of p21. A significant reduction in cell proliferation of EBV-transformed LCLs was observed upon stable knockdown of Pim-1. This study describes a critical role for the oncoprotein Pim-1 in EBV-mediated oncogenesis, as well as provides novel insights into oncogenic kinase-targeted therapeutic intervention of EBV-associated cancers. The oncogenic serine/threonine kinase Pim-1 is upregulated in a number of human cancers including lymphomas, gastric, colorectal and prostate carcinomas. EBV nuclear antigen 3C (EBNA3C) is essential for EBV-induced transformation of human primary B-lymphocytes. Our current study revealed that EBNA3C significantly enhances Pim-1 kinase expression at both the transcript and protein levels. EBNA3C also interacts with Pim-1 and can form a complex in EBV-transformed cells. Moreover, EBNA3C increases nuclear localization of Pim-1 and stabilizes Pim-1 protein levels by inhibiting its poly-ubiquitination. Additionally, EBNA3C augments Pim-1 mediated phosphorylation of p21 and its proteosomal degradation. Stable knockdown of Pim-1 using si-RNA showed a significant decrease in proliferation of EBV transformed lymphoblastoid cell lines and subsequent induction of apoptosis by triggering the intrinsic apoptotic pathway. Therefore, our study demonstrated a new mechanism by which the oncogenic Pim-1 kinase targeted by EBV latent antigen 3C can inhibit p21 function, and is therefore a potential therapeutic target for the treatment of EBV-associated malignancies.
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DOI：
10.1073/pnas.042035699
发表时间：
2002-02-19
影响因子：
11.1
作者：
Chen, XP;Losman, JA;Rothman, P
通讯作者：
Rothman, P
影响因子：
1.6
作者：
Bhattacharya, N;Wang, ZP;Magnuson, NS
通讯作者：
Magnuson, NS
影响因子：
4.8
作者：
Bullock, AN;Debreczeni, J;Turk, BE
通讯作者：
Turk, BE
影响因子：
5.4
作者：
Bajaj, Bharat G.;Murakami, Masanao;Robertson, Erle S.
通讯作者：
Robertson, Erle S.
影响因子：
4.8
作者：
Bachmann, M;Hennemann, H;Möröy, T
通讯作者：
Möröy, T