Strieder Verena, Lutz Werner
Institute of Molecular Biology and Tumor Research (IMT), Emil-Mannkopff-Strasse 2, 35033 Marburg, Germany.
J Biol Chem. 2003 Jan 31;278(5):2983-9. doi: 10.1074/jbc.M207596200. Epub 2002 Nov 15.
Amplification of the MYCN gene, resulting in overexpression of MYCN, distinguishes a subset of neuroblastomas with poor prognosis. The transcription factors driving MYCN expression in neuroblastomas are unknown. In transient-transfection assays, E2F-1, E2F-2, and E2F-3 activate a MYCN reporter construct dependent on the presence of several putative E2F-binding sites. Using chromatin immunoprecipitation, we show that E2F-1, E2F-2, and E2F-3 bind to the proximal MYCN promoter in vivo, specifically in neuroblastoma cell lines expressing MYCN. Inhibition of E2F activity in MYCN-amplified cells by the overexpression of p16(INK4A) reduced MYCN expression. In addition, we provide evidence that E2F proteins are involved in the negative regulation of MYCN by TGF-beta and retinoic acid. These data suggest that E2F transcription factors are critical for both the full activation and the repression of MYCN in neuroblastomas.
MYCN基因的扩增导致MYCN的过表达，这区分出了一部分预后不良的神经母细胞瘤。在神经母细胞瘤中驱动MYCN表达的转录因子尚不清楚。在瞬时转染实验中，E2F-1、E2F-2和E2F-3依赖于几个假定的E2F结合位点的存在来激活MYCN报告基因构建体。通过染色质免疫沉淀，我们表明E2F-1、E2F-2和E2F-3在体内与MYCN近端启动子结合，特别是在表达MYCN的神经母细胞瘤细胞系中。通过过表达p16(INK4A)抑制MYCN扩增细胞中的E2F活性可降低MYCN表达。此外，我们提供证据表明E2F蛋白参与了转化生长因子-β和视黄酸对MYCN的负调控。这些数据表明E2F转录因子对于神经母细胞瘤中MYCN的完全激活和抑制都至关重要。
