Stubenrauch Frank, Straub Elke, Klein Katrin, Kramer Daniela, Iftner Thomas, Wong Margaret, Roden Richard B S
University Hospital Tuebingen, Institute for Medical Virology and Epidemiology of Viral Diseases, Tuebingen, Germany
University Hospital Tuebingen, Institute for Medical Virology and Epidemiology of Viral Diseases, Tuebingen, Germany.
J Virol. 2021 Mar 25;95(8). doi: 10.1128/JVI.01930-20. Epub 2021 Jan 20.
Human papillomavirus (HPV) E1 and E2 proteins activate genome replication. E2 also modulates viral gene expression and is involved in the segregation of viral genomes. In addition to full length E2, almost all PV share the ability to encode an E8^E2 protein, that is a fusion of E8 with the C-terminal half of E2 which mediates specific DNA-binding and dimerization. HPV E8^E2 acts as a repressor of viral gene expression and genome replication. To analyze the function of E8^E2 in vivo, we used the Mus musculus PV1 (MmuPV1)-mouse model system. Characterization of the MmuPV1 E8^E2 protein revealed that it inhibits transcription from viral promoters in the absence and presence of E1 and E2 proteins and that this is partially dependent upon the E8 domain. MmuPV1 genomes, in which the ATG start codon was disrupted (-), displayed a 10- to 25-fold increase in viral gene expression compared to wt genomes in cultured normal mouse tail keratinocytes in short-term experiments. This suggests that the function and mechanism of E8^E2 is conserved between MmuPV1 and HPVs. Surprisingly, challenge of athymic nude Foxn1 mice with MmuPV1 - genomes did not induce warts on the tail in contrast to wt MmuPV1. Furthermore, viral gene expression was completely absent at - MmuPV1 sites 20 - 22 weeks after DNA challenge on the tail or quasivirus challenge in the vaginal vault. This reveals that expression of E8^E2 is necessary to form tumors in vivo and that this is independent from the presence of T-cells. HPV encode an E8^E2 protein which acts as repressors of viral gene expression and genome replication. In cultured normal keratinocytes, E8^E2 is essential for long-term episomal maintenance of HPV31 genomes, but not for HPV16. To understand E8^E2's role in vivo, the Mus musculus PV1 (MmuPV1)-mouse model system was used. This revealed that E8^E2's function as a repressor of viral gene expression is conserved. Surprisingly, MmuPV1 E8^E2 knock out genomes did not induce warts in T-cell deficient mice. This shows for the first time that expression of E8^E2 is necessary for tumor formation in vivo independently of T cell immunity. This indicates that E8^E2 could be an interesting target for anti-viral therapy in vivo.
人乳头瘤病毒（HPV）的E1和E2蛋白可激活基因组复制。E2还可调节病毒基因表达，并参与病毒基因组的分离。除全长E2外，几乎所有乳头瘤病毒（PV）都具备编码E8^E2蛋白的能力，该蛋白是E8与E2蛋白C端一半区域的融合体，可介导特异性DNA结合和二聚化。HPV E8^E2作为病毒基因表达和基因组复制的抑制因子发挥作用。为在体内分析E8^E2的功能，我们使用了小家鼠乳头瘤病毒1型（MmuPV1）-小鼠模型系统。对MmuPV1 E8^E2蛋白的特性分析表明，在E1和E2蛋白存在及不存在的情况下，它均可抑制病毒启动子的转录，且这部分依赖于E8结构域。在短期实验中，与野生型基因组相比，在培养的正常小鼠尾部角质形成细胞中，MmuPV1基因组中ATG起始密码子被破坏（-）的情况下，病毒基因表达增加了10至25倍。这表明E8^E2的功能和机制在MmuPV1和HPV之间是保守的。令人惊讶的是，与野生型MmuPV1相比，用MmuPV1 -基因组攻击无胸腺裸鼠Foxn1后，尾巴上并未诱导出疣。此外，在尾巴上进行DNA攻击或在阴道穹窿进行准病毒攻击20 - 22周后，在-MmuPV1位点完全没有病毒基因表达。这表明E8^E2的表达是体内形成肿瘤所必需的，且这与T细胞的存在无关。HPV编码一种E8^E2蛋白，其作为病毒基因表达和基因组复制的抑制因子发挥作用。在培养的正常角质形成细胞中，E8^E2对于HPV31基因组的长期游离型维持至关重要，但对HPV16并非如此。为了解E8^E2在体内的作用，使用了小家鼠乳头瘤病毒1型（MmuPV1）-小鼠模型系统。这表明E8^E2作为病毒基因表达抑制因子的功能是保守的。令人惊讶的是，MmuPV1 E8^E2基因敲除基因组在T细胞缺陷小鼠中并未诱导出疣。这首次表明E8^E2的表达是体内肿瘤形成所必需的，与T细胞免疫无关。这表明E8^E2可能是体内抗病毒治疗的一个有趣靶点。
