Identification of a novel telomerase repressor that interacts with the human papillomavirus type-16 E6/E6-AP complex
Identification of a novel telomerase repressor that interacts with the human papillomavirus type-16 E6/E6-AP complex
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DOI：
10.1101/gad.1214704
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发表时间：
2004-09-15
影响因子：
10.5
通讯作者：
Galloway, DA
中科院分区：
文献类型：
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作者：
Gewin, L;Myers, H;Galloway, DA
人乳头瘤病毒(HPV)16型E6癌蛋白的关键永生化活性是诱导端粒酶催化限速亚基hTERT的表达。此外，E6与一种名为E6相关蛋白(E6-AP)的细胞蛋白结合，形成一种E3泛素连接酶，该连接酶针对P53进行蛋白酶体依赖的降解。虽然端粒酶诱导和P53降解是E6各自独立的功能，但E6与E6-AP的结合与hTERT的诱导密切相关。在这里，我们证明了使用shRNAs来减少E6-AP的表达，E6-AP是E6介导的端粒酶诱导所必需的。酵母双杂交筛选新靶点的E6/E6-AP E3泛素连接酶复合体鉴定为NFX1。NFX1有两种亚型：在hTERT启动子与c-Myc共激活的NFX1-123和抑制hTERT启动子的NFX1-91。NFX1-91在表达E6的上皮细胞中高度泛素化和不稳定。此外，通过shRNA敲除NFX1-91导致内源性hTERT启动子的下调和端粒酶活性的升高。我们认为，HPV-16E6/E6-AP复合体诱导端粒酶的作用涉及靶向NFX1-91，NFX1-91是一种新发现的端粒酶抑制因子，用于泛素化和降解。
The critical immortalizing activity of the human papillomavirus (HPV) type-16 E6 oncoprotein is to induce expression of hTERT, the catalytic and rate-limiting subunit of telomerase. Additionally, E6 binds to a cellular protein called E6-associated protein (E6-AP) to form an E3 ubiquitin ligase that targets p53 for proteasome-dependent degradation. Although telomerase induction and p53 degradation are separable and distinct functions of E6, binding of E6 to E6-AP strongly correlated with the induction of hTERT. Here, we demonstrate using shRNAs to reduce E6-AP expression that E6-AP is required for E6-mediated telomerase induction. A yeast two-hybrid screen to find new targets of the E6/E6-AP E3 ubiquitin ligase complex identified NFX1. Two isoforms of NFX1 were found: NFX1-123, which coactivated with c-Myc at the hTERT promoter, and NFX1-91, which repressed the hTERT promoter. NFX1-91 was highly ubiquitinated and destabilized in epithelial cells expressing E6. Furthermore, knockdown of NFX1-91 by shRNA resulted in derepression of the endogenous hTERT promoter and elevated levels of telomerase activity. We propose that the induction of telomerase by the HPV-16 E6/E6-AP complex involves targeting of NFX1-91, a newly identified repressor of telomerase, for ubiquitination and degradation.