Mori Seiichiro, Takeuchi Takamasa, Ishii Yoshiyuki, Yugawa Takashi, Kiyono Tohru, Nishina Hiroshi, Kukimoto Iwao
Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan
Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan.
J Virol. 2017 Feb 28;91(6). doi: 10.1128/JVI.02413-16. Print 2017 Mar 15.
The cytidine deaminase APOBEC3B (A3B) underlies the genetic heterogeneity of several human cancers, including cervical cancer, which is caused by human papillomavirus (HPV) infection. We previously identified a region within the A3B promoter that is activated by the viral protein HPV16 E6 in human keratinocytes. Here, we discovered three sites recognized by the TEAD family of transcription factors within this region of the A3B promoter. Reporter assays in HEK293 cells showed that exogenously expressed TEAD4 induced A3B promoter activation through binding to these sites. Normal immortalized human keratinocytes expressing E6 (NIKS-E6) displayed increased levels of TEAD1/4 protein compared to parental NIKS. A series of E6 mutants revealed that E6-mediated degradation of p53 was important for increasing TEAD4 levels. Knockdown of TEADs in NIKS-E6 significantly reduced A3B mRNA levels, whereas ectopic expression of TEAD4 in NIKS increased A3B mRNA levels. Finally, chromatin immunoprecipitation assays demonstrated increased levels of TEAD4 binding to the A3B promoter in NIKS-E6 compared to NIKS. Collectively, these results indicate that E6 induces upregulation of A3B through increased levels of TEADs, highlighting the importance of the TEAD-A3B axis in carcinogenesis. The expression of APOBEC3B (A3B), a cellular DNA cytidine deaminase, is upregulated in various human cancers and leaves characteristic, signature mutations in cancer genomes, suggesting that it plays a prominent role in carcinogenesis. Viral oncoproteins encoded by human papillomavirus (HPV) and polyomavirus have been reported to induce A3B expression, implying the involvement of A3B upregulation in virus-associated carcinogenesis. However, the molecular mechanisms causing A3B upregulation remain unclear. Here, we demonstrate that exogenous expression of the cellular transcription factor TEAD activates the A3B promoter. Further, the HPV oncoprotein E6 increases the levels of endogenous TEAD1/4 protein, thereby leading to A3B upregulation. Since increased levels of TEAD4 are frequently observed in many cancers, an understanding of the direct link between TEAD and A3B upregulation is of broad oncological interest.
胞苷脱氨酶载脂蛋白B mRNA编辑酶催化多肽样3B（APOBEC3B，A3B）是包括宫颈癌在内的几种人类癌症基因异质性的基础，宫颈癌由人乳头瘤病毒（HPV）感染引起。我们之前在A3B启动子中鉴定出一个区域，该区域在人类角质形成细胞中被病毒蛋白HPV16 E6激活。在此，我们在A3B启动子的这个区域发现了转录因子TEAD家族识别的三个位点。在HEK293细胞中进行的报告基因检测表明，外源表达的TEAD4通过与这些位点结合诱导A3B启动子激活。与亲本NIKS相比，表达E6的正常永生化人类角质形成细胞（NIKS-E6）中TEAD1/4蛋白水平升高。一系列E6突变体表明，E6介导的p53降解对于提高TEAD4水平很重要。在NIKS-E6中敲低TEADs显著降低A3B mRNA水平，而在NIKS中异位表达TEAD4则增加A3B mRNA水平。最后，染色质免疫沉淀检测表明，与NIKS相比，NIKS-E6中TEAD4与A3B启动子的结合水平增加。总体而言，这些结果表明E6通过增加TEADs水平诱导A3B上调，突出了TEAD-A3B轴在致癌过程中的重要性。细胞DNA胞苷脱氨酶载脂蛋白B mRNA编辑酶催化多肽样3B（APOBEC3B，A3B）的表达在各种人类癌症中上调，并在癌症基因组中留下特征性的标志性突变，表明它在致癌过程中起重要作用。据报道，人乳头瘤病毒（HPV）和多瘤病毒编码的病毒癌蛋白可诱导A3B表达，这意味着A3B上调参与病毒相关的致癌作用。然而，导致A3B上调的分子机制仍不清楚。在此，我们证明细胞转录因子TEAD的外源表达激活A3B启动子。此外，HPV癌蛋白E6增加内源性TEAD1/4蛋白水平，从而导致A3B上调。由于在许多癌症中经常观察到TEAD4水平升高，了解TEAD与A3B上调之间的直接联系具有广泛的肿瘤学意义。
