Williams J F, Zhang Y, Williams M A, Hou S, Kushner D, Ricciardi R P
Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA.
Curr Top Microbiol Immunol. 2004;273:245-88. doi: 10.1007/978-3-662-05599-1_8.
A broad spectrum of genetic and molecular investigations carried out with group C, Ad2 and Ad5, and with group A, Ad12, have shown that early region1 (E1) gene products are sufficient for complete transformation of rodent cells in vitro by these viruses. During the past quarter century, the processes by which E1A proteins, in cooperation with E1B proteins, perturb the cell cycle and induce the transformed phenotype, have become well defined. Somewhat less understood is the basis for the differential oncogenicity of these two groups of viruses, and the processes by which the E1A proteins of Ad12 induce a tumorigenic phenotype in transformants resulting from infection of cells in vivo and in vitro. In this chapter we review previous findings and present new evidence which demonstrates that Ad12 E1A possesses two or more independent functions enabling it to induce tumors. One of these functions lies in its capacity to repress transcription of MHC class I genes, allowing the tumor cells to avoid lysis by cytotoxic T lymphocytes. We have shown that class I repression is mediated through increased binding of repressor COUP-TF and decreased binding of NF-kB to the class I enhancer. In addition to mediating immune escape, E1A also determines the susceptibility of transformants to Natural Killer (NK) cell lysis, and in this case, also, Ad12 transformants are not susceptible. By using Ad12 mutants containing chimeric E1A Ad12-Ad5 genes, point mutations, or a specific deletion, we have shown that the unique spacer region of Ad12 E1A is an oncogenic determinant, but is not required for transformation in vitro. Given that the E1A regions responsible for class I repression are first exon encoded, we have examined a set of cell lines transformed by these altered viruses, and have found that while they display greatly reduced tumorigenicity, they maintain a wildtype capacity to repress class I transcription. Whether the spacer contributes to NK evasion remains unresolved. Lastly, we discuss the properties of the Ad2/Ad5 E1A C-terminal negative modulator of tumorigenicity, and examine the effects on transformation, tumor induction and transformant tumorigenicity, when the Ad5 negative modulator is placed by chimeric construction in Ad12 E1A.
对C组腺病毒2型和5型以及A组腺病毒12型进行的广泛遗传和分子研究表明，早期区域1（E1）基因产物足以使这些病毒在体外完全转化啮齿动物细胞。在过去的四分之一个世纪里，E1A蛋白与E1B蛋白协同作用扰乱细胞周期并诱导转化表型的过程已得到明确界定。对于这两组病毒致癌性差异的基础以及腺病毒12型的E1A蛋白在体内和体外感染细胞产生的转化体中诱导致瘤表型的过程，人们了解得相对较少。在本章中，我们回顾了以前的研究结果并提供了新的证据，这些证据表明腺病毒12型的E1A具有两种或更多独立功能，使其能够诱导肿瘤。其中一个功能在于它能够抑制MHC I类基因的转录，使肿瘤细胞避免被细胞毒性T淋巴细胞裂解。我们已经表明，I类抑制是通过增加抑制因子COUP - TF的结合以及减少NF - kB与I类增强子的结合来介导的。除了介导免疫逃逸外，E1A还决定了转化体对自然杀伤（NK）细胞裂解的敏感性，在这种情况下，腺病毒12型转化体也不敏感。通过使用含有嵌合E1A腺病毒12 - 腺病毒5基因、点突变或特定缺失的腺病毒12型突变体，我们已经表明腺病毒12型E1A独特的间隔区是一个致癌决定因素，但在体外转化过程中并非必需。鉴于负责I类抑制的E1A区域是由第一个外显子编码的，我们研究了一组由这些改变的病毒转化的细胞系，发现虽然它们的致瘤性大大降低，但它们保持了抑制I类转录的野生型能力。间隔区是否有助于逃避NK细胞仍未解决。最后，我们讨论了腺病毒2型/腺病毒5型E1A的C末端致瘤性负调节因子的特性，并研究了通过嵌合构建将腺病毒5型负调节因子置于腺病毒12型E1A中时对转化、肿瘤诱导和转化体致瘤性的影响。
