Lyons Tarrah E, Salih Maysoon, Tuana Balwant S
Dept. of Cellular and Molecular Medicine, Faculty of Medicine, Univ. of Ottawa, 451 Smyth Rd., Ottawa, ON, Canada K1H 8M5.
Am J Physiol Cell Physiol. 2006 Jan;290(1):C189-99. doi: 10.1152/ajpcell.00630.2004. Epub 2005 Aug 17.
E2F6 is believed to repress E2F-responsive genes and therefore serve a role in cell cycle regulation. Analysis of the human E2F6 promoter region revealed the presence of two putative E2F binding sites, both of which were found to be functionally critical because deletion or mutations of these sites abolished promoter activity. Ectopic expression of E2F1 protein was found to increase E2F6 mRNA levels and significantly upregulate E2F6 promoter activity. Deletion or mutation of the putative E2F binding sites nullified the effects of E2F1 on the E2F6 promoter activity. Studies on the temporal induction of E2F family members demonstrated that the activating E2Fs, and most notably E2F1, were upregulated before E2F6 during cell cycle progression at the G1/S phase, and this coincided with the time course of induction experienced by the E2F6 promoter during the course of the cell cycle. EMSAs indicated the specific binding of nuclear complexes to the E2F6 promoter that contained E2F1-related species whose binding was specifically competed by the consensus E2F binding site. Chromatin immunoprecipitation assays with anti-E2Fs demonstrated the association of E2F family members with the E2F6 promoter in vivo. These data indicate that the expression of the E2F6 repressor is influenced at the transcriptional level by E2F family members and suggest that interplay among these transcriptional regulators, especially E2F1, may be critical for cell cycle regulation.
E2F6被认为可抑制E2F反应性基因，因此在细胞周期调控中发挥作用。对人类E2F6启动子区域的分析揭示了两个假定的E2F结合位点的存在，发现这两个位点在功能上都至关重要，因为这些位点的缺失或突变会消除启动子活性。发现E2F1蛋白的异位表达可增加E2F6 mRNA水平并显著上调E2F6启动子活性。假定的E2F结合位点的缺失或突变使E2F1对E2F6启动子活性的影响无效。对E2F家族成员的时间诱导研究表明，在细胞周期G1/S期进展过程中，激活型E2F，尤其是E2F1，在E2F6之前上调，这与细胞周期过程中E2F6启动子所经历的诱导时间进程一致。电泳迁移率变动分析表明核复合物与包含E2F1相关物种的E2F6启动子特异性结合，其结合可被共有E2F结合位点特异性竞争。用抗E2F进行的染色质免疫沉淀分析证明了E2F家族成员在体内与E2F6启动子的关联。这些数据表明E2F6阻遏物的表达在转录水平上受E2F家族成员影响，并表明这些转录调节因子之间的相互作用，尤其是E2F1，可能对细胞周期调控至关重要。
