NFX1-123 and poly(A) binding proteins synergistically augment activation of telomerase in human papillomavirus type 16 E6-expressing cells
NFX1-123 and poly(A) binding proteins synergistically augment activation of telomerase in human papillomavirus type 16 E6-expressing cells
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DOI：
10.1128/jvi.02007-06
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发表时间：
2007-04-01
影响因子：
5.4
通讯作者：
Galloway, Denise A.
中科院分区：
文献类型：
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作者：
Katzenellenbogen, Rachel A.;Egelkrout, Erin M.;Galloway, Denise A.
克服体细胞中的衰老信号对细胞永生和癌变至关重要。高危人乳头瘤病毒（HPV）可以通过HPV E7降解视网膜母细胞瘤蛋白，并通过异源二聚体HPV E6/E6相关蛋白（E6AP）激活端粒酶的催化亚基hTERT转录，使培养的上皮细胞永生。我们实验室最近的工作发现了一种新的hTERT转录抑制因子NFX1-91，它针对16型HPV (HPV16) E6/E6AP的泛素介导降解。相反，NFX1-123，一个剪接变体NFX1，增加了HPV16 E6/E6AP激活的hTERT启动子的表达。在没有E6AP的情况下，hpv16e6通过NFX1的共同中心结构域结合NFX1-91和NFX1-123。NFX1-123正调控hTERT表达，其敲低降低hTERT mRNA水平和端粒酶活性，过表达提高端粒酶活性。我们发现了NFX1-123的新蛋白伙伴，包括几个细胞质多聚(A)结合蛋白（PABPC），它们通过NFX1-123的n端PAM2基序（其他PABPC蛋白伙伴的蛋白质结构域特征）与NFX1-123相互作用。此外，NFX1-123和PABPCs共同对htert调控的报告基因检测具有协同刺激作用。这些数据表明，NFX1-123在表达HPV16 e6的上皮细胞中是hTERT调控不可或缺的一部分，NFX1-123和PABPCs之间的相互作用对hTERT活性至关重要。
Overcoming senescence signals in somatic cells is critical to cellular immortalization and carcinogenesis. High-risk human papillomavirus (HPV) can immortalize epithelial cells in culture through degradation of the retinoblastoma protein by HPV E7 and activation of hTERT transcription, the catalytic subunit of telomerase, by the heterodimer HPV E6/E6-associated protein (E6AP). Recent work in our laboratory identified a novel repressor of hTERT transcription, NFX1-91, which is targeted for ubiquitin-mediated degradation by HPV type 16 (HPV16) E6/E6AP. In contrast, NFX1-123, a splice variant NFX1, increased expression from an hTERT promoter that was activated by HPV16 E6/E6AP. Here, we show that HPV16 E6 bound both NFX1-91 and NFX1-123 through the common central domain of NFX1 in the absence of E6AP. NFX1-123 positively regulated hTERT expression, as its knockdown decreased hTERT mRNA levels and telomerase activity and its overexpression increased telomerase activity. We identified new protein partners of NFX1-123, including several cytoplasmic poly(A) binding proteins (PABPCs) that interacted with NFX1-123 through its N-terminal PAM2 motif, a protein domain characteristic of other PABPC protein partners. Furthermore, NFX1-123 and PABPCs together had a synergistic stimulatory effect on hTERT-regulated reporter assays. The data suggest that NFX1-123 is integral to hTERT regulation in HPV16 E6-expressing epithelial cells and that the interaction between NFX1-123 and PABPCs is critical to hTERT activity.