Different mechanisms contribute to the E2-mediated transcriptional repression of human papillomavirus type 18 viral oncogenes
Different mechanisms contribute to the E2-mediated transcriptional repression of human papillomavirus type 18 viral oncogenes
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DOI：
10.1128/jvi.71.12.9343-9349.1997
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发表时间：
1997-12-01
影响因子：
5.4
通讯作者：
Thierry, F
中科院分区：
文献类型：
--
作者：
Demeret, C;Desaintes, C;Thierry, F
人类乳头瘤病毒18型(HPV18)E6和E7癌基因的转录受到病毒E2蛋白的抑制。在C33细胞中，我们已经证明，在HPV18长控制区(LCR)中存在的四个E2结合位点(E2BS)中，只有邻近TATA盒的结合位点(E2BS 1)参与了E2介导的抑制。在目前的研究中，我们试图确定这种现象是否在其他细胞系中保守。我们首先证明了P-105启动子附近的所有三个E2 BS都是在HeLa和HaCaT细胞中完全抑制其活性所必需的。E2通过Sp1的移位抑制了E2BS2的表达。第二，缺少N-末端反式激活结构域的截短的E2产物比全长蛋白更有效地抑制转录。当E2的N末端结构域被VP16的激活结构域取代时，抑制作用被取消。VP16-E2嵌合蛋白可以激活TATA盒中突变的LCR的转录。DNA-蛋白质结合研究表明，E2与其在LCR中的四个结合部位具有相似的亲和力。然而，对这些具有过多结合位点的配合物的挑战表明，与E2 BS 4的相互作用最稳定，而与E2 BS 1的相互作用最不稳定。此外，与全长E2形成的复合体比与N末端截短的蛋白质形成的复合体更不稳定。
Transcription of the human papillomavirus type 18 (HPV18) E6 and E7 oncogenes is repressed by the viral E2 protein. In C33 cells, we have previously shown that of the four E2 binding sites (E2 BS) present in the HPV18 long control region (LCR), only the binding site adjacent to the TATA box (E2 BS 1) was involved in E2-mediated repression. In the present study, we sought to determine whether this phenomenon was conserved in other cell lines. We first showed that all three E2 BS proximal to the P-105 promoter were required for full repression of its activity in HeLa and HaCaT cells. Repression by E2 at E2 BS 2 occurred through the displacement of Sp1. Second, a truncated E2 product, lacking the N-terminal transactivation domain, repressed transcription more efficiently than the full-length protein. Repression was abolished when the N-terminal domain of E2 was replaced by the activation domain of VP16. The VP16-E2 chimeric protein could activate transcription from an LCR mutated in its TATA box. DNA-protein binding studies showed that E2 associates with its four binding sites in the LCR with similar affinities. However, challenge of such complexes with excess binding sites demonstrated that interaction with E2 BS 4 was the most stable while interaction with E2 BS 1 was the least stable. Furthermore, complexes with the full-length E2 were less stable than those formed with the N-terminally truncated protein.