The human DEK proto-oncogene is a senescence inhibitor and an upregulated target of high-risk human papillomavirus E7

The human DEK proto-oncogene is a nucleic acid binding protein with suspected roles in human carcinogenesis, autoimmune disease, and viral infection. Intracellular DEK functions, however, are poorly understood. In papillomavirus-positive cervical cancer cells, downregulation of viral E6/E7 oncogene expression results in cellular senescence. We report here the specific repression of DEK message and protein levels in senescing human papillomavirus type 16- (HPV16-) and HPV18-positive cancer cell lines as well as in primary cells undergoing replicative senescence. Cervical cancer cell senescence was partially overcome by DEK overexpression, and DEK overexpression was sufficient for extending the life span of primary keratinocytes, supporting critical roles for this molecule as a senescence regulator. In order to determine whether DEK is a bona fide HPV oncogene target in primary cells, DEK expression was monitored in human keratinocytes transduced with HPV E6 and/or E7. The results identify high-risk HPV E7 as a positive DEK regulator, an activity that is not shared by low-risk HPV E7 protein. Experiments in mouse embryo fibroblasts recapitulated the observed E7-mediated DEK induction and demonstrated that both basal and E7-induced regulation of DEK expression are controlled by the retinoblastoma protein family. Taken together, our results suggest that DEK upregulation may be a common event in human carcinogenesis and may reflect its senescence inhibitory function.     

人乳头瘤病毒16型长控制区上YY1结合位点的破坏可增强病毒诱导细胞永生化能力

细胞转录调节因子 Ｙ Ｙ１ 可抑制人乳头瘤病毒１６ 型（ Ｈ Ｐ Ｖ １６） 癌基因启动子 Ｐ９７ 的活性, Ｙ Ｙ１ 位点的突变和缺失不仅可诱导 Ｐ９７ 活性增强而且可在全基因组内增强 Ｅ６ 癌基因转录,同时使病毒对啮齿类动物纤维细胞的转化能力增强。为了观测人乳头瘤病毒１６ 型长控制区（ Ｈ Ｐ Ｖ１６ Ｌ Ｃ Ｒ） 序列上 Ｙ Ｙ１ 蛋白特异性结合位点破坏在完整基因组范围内对人原代包皮角源细胞永生化能力的影响,将 Ｈ Ｐ Ｖ １６ Ｙ Ｙ１ 位点突变株和野毒株转染至人原代包皮角源细胞。筛选结果表明,突变株可诱导形成永生化细胞,永生化能力明显高于野毒株。对４ 株永生化细胞系 Ｄ Ｎ Ａ检测发现,均含有呈整合状态的 Ｈ Ｐ Ｖ １６ Ｄ Ｎ Ａ,其中３ 株的 Ｅ１／ Ｅ２ 区域有缺失。 Ｒ Ｎ Ａ 检测显示,４株细胞内均有 Ｅ６／ Ｅ７ ｍ Ｒ Ｎ Ａ 的转录。这表明, Ｈ Ｐ Ｖ １６ Ｌ Ｃ Ｒ 上 Ｙ Ｙ１ 蛋白特异性结合位点的破坏,可在完整基因组范围内增强病毒使人原代包皮角源细胞永生化的能力。     

The JAK-STAT Transcriptional Regulator,STAT-5, Activates the ATM DNA Damage Pathway to Induce HPV 31 Genome Amplification upon Epithelial Differentiation

High-risk human papillomavirus (HPV) must evade innate immune surveillance to establish persistent infections and to amplify viral genomes upon differentiation. Members of the JAK-STAT family are important regulators of the innate immune response and HPV proteins downregulate expression of STAT-1 to allow for stable maintenance of viral episomes. STAT-5 is another member of this pathway that modulates the inflammatory response and plays an important role in controlling cell cycle progression in response to cytokines and growth factors. Our studies show that HPV E7 activates STAT-5 phosphorylation without altering total protein levels. Inhibition of STAT-5 phosphorylation by the drug pimozide abolishes viral genome amplification and late gene expression in differentiating keratinocytes. In contrast, treatment of undifferentiated cells that stably maintain episomes has no effect on viral replication. Knockdown studies show that the STAT-5β isoform is mainly responsible for this activity and that this is mediated through the ATM DNA damage response. A downstream target of STAT-5, the peroxisome proliferator-activated receptor γ (PPARγ) contributes to the effects on members of the ATM pathway. Overall, these findings identify an important new regulatory mechanism by which the innate immune regulator, STAT-5, promotes HPV viral replication through activation of the ATM DNA damage response.