Comparative analysis of SV40 17kT and LT function in vivo demonstrates that LT's C-terminus re-programs hepatic gene expression and is necessary for tumorigenesis in the liver
Comparative analysis of SV40 17kT and LT function in vivo demonstrates that LT's C-terminus re-programs hepatic gene expression and is necessary for tumorigenesis in the liver
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DOI：
10.1038/oncsis.2012.27
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发表时间：
2012-09-01
期刊：
影响因子：
6.2
通讯作者：
Hammer, R. E.
中科院分区：
文献类型：
--
作者：
Comerford, S. A.;Schultz, N.;Hammer, R. E.
猴病毒40（SV 40）大T抗原（LT）的转化在很大程度上是通过其与LT内不同结合域的各种细胞蛋白的相互作用介导的。虽然LT的N-末端与肿瘤抑制因子Rb的相互作用是LT依赖性转化所必需的，但LT的C-末端与p53的相互作用的要求不太清楚，并且依赖于细胞和环境。在这里，我们报告了一系列表达强力霉素诱导的肝脏特异性病毒转录本的转基因小鼠，该转录本产生丰富的17 kT，这是一种天然存在的SV 40早期产物，其前131个氨基酸与LT共线性，并结合到Rb，但不结合p53。对表达17 kT或全长LT的转基因小鼠肝脏的比较分析表明，17 kT刺激细胞增殖并诱导肝脏增生，但不能诱导肝脏发育不良或促进肝癌发生。基因表达谱分析表明，17 kT和LT调用一组共享的分子特征与LT的N-末端对Rb-E2 F介导的肝细胞转录控制的作用一致。然而，17 kT也诱导一组独特的基因，其中许多是已知的p53转录靶点，而LT积极抑制它们。LT还独特地使印记网络内的基因子集的表达失调，并迅速将肝细胞基因表达重新编程为更类似胎儿的状态。最后，我们提供的证据表明，LT/p53复合物提供了一个增益的功能LT依赖性转化在肝脏中，并确认LT的C-末端的肝肿瘤的发展的绝对要求，证明磷酸酶和张力蛋白同源物（PTEN）的缺陷很容易与LT，但不是17 kT，肿瘤的发生。这些结果证实了LT的N-和C-末端的独立和相互依赖的功能，并强调了在细胞类型依赖性转化中对LT的C-末端的要求的差异。
Transformation by Simian Virus 40 (SV40) large T antigen (LT) is mediated in large part by its interaction with a variety of cellular proteins at distinct binding domains within LT. While the interaction of LT's N-terminus with the tumor suppressor Rb is absolutely required for LT-dependent transformation, the requirement for the interaction of LT's C-terminus with p53 is less clear and cell- and context-dependent. Here, we report a line of transgenic mice expressing a doxycycline-inducible liver-specific viral transcript that produces abundant 17kT, a naturally occurring SV40 early product that is co-linear with LT for the first 131 amino acids and that binds to Rb, but not p53. Comparative analysis of livers of transgenic mice expressing either 17kT or full length LT demonstrates that 17kT stimulates cell proliferation and induces hepatic hyperplasia but is incapable of inducing hepatic dysplasia or promoting hepatocarcinogenesis. Gene expression profiling demonstrates that 17kT and LT invoke a set of shared molecular signatures consistent with the action of LT's N-terminus on Rb-E2F-mediated control of hepatocyte transcription. However, 17kT also induces a unique set of genes, many of which are known transcriptional targets of p53, while LT actively suppresses them. LT also uniquely deregulates the expression of a subset of genes within the imprinted network and rapidly re-programs hepatocyte gene expression to a more fetal-like state. Finally, we provide evidence that the LT/p53 complex provides a gain-of-function for LT-dependent transformation in the liver, and confirm the absolute requirement for LT's C-terminus for liver tumor development by demonstrating that phosphatase and tensin homolog (PTEN)-deficiency readily cooperates with LT, but not 17kT, for tumorigenesis. These results confirm independent and inter-dependent functions for LT's N- and C-terminus and emphasize differences in the requirements for LT's C-terminus in cell-type dependent transformation.