Desaintes C, Goyat S, Garbay S, Yaniv M, Thierry F
Unité des virus oncogènes, département des biotechnologies, URA 1644 du CNRS, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris, cedex 15, Paris, France.
Oncogene. 1999 Aug 12;18(32):4538-45. doi: 10.1038/sj.onc.1202818.
We have previously shown that expression of the papillomavirus E2 protein in HeLa cells induces p53 accumulation and causes both cell cycle arrest and apoptosis. In contrast to growth arrest, onset of apoptosis was not correlated with an increase of p53 transcriptional activity. In the present study, we conducted biochemical and genetic experiments in order to determine whether E2-induced apoptosis was independent of p53 induction. We showed that E2 did not alter the transcription of Bax, a known p53-activated cell death inducer. The time course of apoptotic cell death preceded p53 induction by several hours. Overexpression of the HPV18 E6 oncogene prevented E2-mediated p53 accumulation, but did not alter the rate of cell death. Finally, point mutants of the HPV18 E2 transactivation domain induced apoptosis, although they were unable to induce high p53 accumulation or cell cycle arrest. In addition, the results obtained with these mutants indicated that both transcriptional activation and replication functions of E2 were dispensable for the induction of cell death. These observations show that E2-induced apoptosis is an early event, independent of p53 accumulation and unrelated to downstream p53-dependent transcriptional events.
我们之前已经表明，乳头瘤病毒E2蛋白在HeLa细胞中的表达会诱导p53积累，并导致细胞周期停滞和凋亡。与生长停滞相反，凋亡的发生与p53转录活性的增加无关。在本研究中，我们进行了生化和遗传学实验，以确定E2诱导的凋亡是否独立于p53诱导。我们发现E2不会改变Bax的转录，Bax是一种已知的由p53激活的细胞死亡诱导因子。凋亡性细胞死亡的时间进程比p53诱导提前数小时。HPV18 E6癌基因的过表达可阻止E2介导的p53积累，但不会改变细胞死亡率。最后，HPV18 E2反式激活结构域的点突变体可诱导凋亡，尽管它们无法诱导高水平的p53积累或细胞周期停滞。此外，用这些突变体获得的结果表明，E2的转录激活和复制功能对于诱导细胞死亡都是不必要的。这些观察结果表明，E2诱导的凋亡是一个早期事件，独立于p53积累，且与下游p53依赖性转录事件无关。
