Departamento de Química Inorgánica, Orgánica y Bioquímica, Facultad de Medicina/Centro Regional de Investigaciones Biomédicas (CRIB), Universidad de Castilla-La Mancha, 02006 Albacete, Spain.
J Mol Biol. 2012 Mar 16;417(1-2):36-50. doi: 10.1016/j.jmb.2012.01.035. Epub 2012 Jan 27.
The epidermal growth factor-like protein DLK2, highly homologous to DLK1, has been identified as a modulator of adipogenesis in vitro. Knocking down Dlk2 expression prevents adipogenesis of 3T3-L1 cells but enhances that of the mesenchymal cell line C3H10T1/2. The expression of Dlk2 shows two peaks along this differentiation process: the first one, in response to 3-isobutyl-1-methylxanthine (IBMX) and dexamethasone (Dex), and the second, shortly after exposure to insulin. Nothing is known about the transcriptional regulation of Dlk2 during adipogenesis. Here, we report that, during early adipogenesis of 3T3-L1 cells, Dlk2 expression is controlled independently by IBMX and Dex. We also show that KLF4, a transcription factor critical for the control of early adipogenesis, binds directly to the Dlk2 promoter and increases Dlk2 expression in response to IBMX. Overexpression of KLF4 leads to an increase in DLK2 expression levels, whereas KLF4 knockdown downregulates the transcriptional activity of the Dlk2 promoter. Finally, we demonstrate that KLF4 regulates the basal expression of Dlk2 in C3H10T1/2 cells, and it is required for the adipogenic differentiation of those cells. These results indicate that KLF4 mediates the transcriptional regulation of Dlk2 in response to IBMX during the early stages of adipogenesis.
表皮生长因子样蛋白 DLK2 与 DLK1 高度同源，已被鉴定为体外脂肪生成的调节剂。敲低 Dlk2 表达可阻止 3T3-L1 细胞的脂肪生成，但增强间充质细胞系 C3H10T1/2 的脂肪生成。DLK2 的表达在这个分化过程中呈现两个高峰：第一个高峰是对 3-异丁基-1-甲基黄嘌呤（IBMX）和地塞米松（Dex）的反应，第二个高峰是在暴露于胰岛素后不久。关于脂肪生成过程中 Dlk2 的转录调控还知之甚少。在这里，我们报告在 3T3-L1 细胞的早期脂肪生成过程中，DLK2 的表达受 IBMX 和 Dex 的独立控制。我们还表明，KLF4 是控制早期脂肪生成的关键转录因子，直接与 DLK2 启动子结合，并响应 IBMX 增加 DLK2 的表达。KLF4 的过表达导致 DLK2 表达水平的增加，而 KLF4 的敲低则下调 Dlk2 启动子的转录活性。最后，我们证明 KLF4 调节 C3H10T1/2 细胞中 Dlk2 的基础表达，并需要这些细胞的脂肪生成分化。这些结果表明，KLF4 介导了 KLF4 在脂肪生成早期对 IBMX 反应时 Dlk2 的转录调节。
