PDF(Pubmed)
Abstract：
Ecdysone signaling in Drosophila remains a popular model for investigating the mechanisms of steroid action in eukaryotes. The ecdysone receptor EcR can effectively bind ecdysone-response elements with or without the presence of a hormone. For years, EcR enhancers were thought to respond to ecdysone via recruiting coactivator complexes, which replace corepressors and stimulate transcription. However, the exact mechanism of transcription activation by ecdysone remains unclear. Here, we present experimental data on 11 various coregulators at ecdysone-responsive loci of Drosophila S2 cells. We describe the regulatory elements where coregulators reside within these loci and assess changes in their binding levels following 20-hydroxyecdysone treatment. In the current study, we detected the presence of some coregulators at the TSSs (active and inactive) and boundaries marked with CP190 rather than enhancers of the ecdysone-responsive loci where EcR binds. We observed minor changes in the coregulators\' binding level. Most were present at inducible loci before and after 20-hydroxyecdysone treatment. Our findings suggest that: (1) coregulators can activate a particular TSS operating from some distal region (which could be an enhancer, boundary regulatory region, or inactive TSS); (2) coregulators are not recruited after 20-hydroxyecdysone treatment to the responsive loci; rather, their functional activity changes (shown as an increase in H3K27 acetylation marks generated by CBP/p300/Nejire acetyltransferase). Taken together, our findings imply that the 20-hydroxyecdysone signal enhances the functional activity of coregulators rather than promoting their binding to regulatory regions during the ecdysone response.
摘要：
果蝇中的蜕皮激素信号仍然是研究真核生物中类固醇作用机制的流行模型。蜕皮激素受体EcR可以在存在或不存在激素的情况下有效地结合蜕皮激素反应元件。多年来,EcR增强剂被认为通过招募共激活复合物来响应蜕皮激素，取代辅抑制因子并刺激转录。然而,蜕皮激素转录激活的确切机制尚不清楚。这里,我们提供了果蝇S2细胞蜕皮激素反应基因座上11种不同共调节剂的实验数据。我们描述了共调节剂位于这些基因座内的调节元件，并评估了20-羟基蜕皮激素治疗后其结合水平的变化。在目前的研究中,我们检测到在TSS(活性和非活性)和用CP190标记的边界处存在一些共调节因子,而不是在EcR结合的蜕皮激素应答基因座的增强因子.我们观察到共调节剂结合水平的微小变化。在20-羟基蜕皮激素治疗之前和之后，大多数都存在于诱导型基因座。我们的发现表明：（1）共调节剂可以激活从某些远端区域起作用的特定TSS（可能是增强子，边界管理区，或非活性TSS）；（2）在20-羟基蜕皮激素治疗后，没有招募共调节因子到反应位点；相反，它们的功能活性改变(显示为CBP/p300/Nejire乙酰转移酶产生的H3K27乙酰化标记的增加)。一起来看,我们的研究结果表明,20-羟基蜕皮激素信号增强了共调节因子的功能活性,而不是促进它们在蜕皮激素反应过程中与调节区的结合.
