Evdokimova Aleksandra A, Kolesnikova Tatyana D, Mazina Marina Yu, Krasnov Aleksey N, Erokhin Maksim, Chetverina Darya, Vorobyeva Nadezhda E
Institute of Gene Biology, Russian Academy of Sciences, 119334, Moscow, Russia.
Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, 630090, Novosibirsk, Russia.
Nucleic Acids Res. 2025 Apr 10;53(7). doi: 10.1093/nar/gkaf284.
Transcriptional activation by 20-hydroxyecdysone (20E) in Drosophila provides an excellent model for studying tissue-specific responses to steroids. An increase in the 20E concentration regulates the degradation of larval and the proliferation of adult tissues during metamorphosis. To study 20E-dependent transcription, we used the natural system for controlling the 20E concentration-the E23 membrane transporter-which exports 20E from the cell. We artificially expressed E23 in tissues to suppress the first wave of 20E-inducible transcription at metamorphosis. E23 expression revealed a plethora of 20E-dependent genes in salivary glands, while mildly affecting transcription in brain. We described the mechanisms controlling transcriptional activation by 20E in salivary glands. 20E depletion decreased the binding of Pol II and the TFIID subunit, TBP, to the promoters of primary targets, demonstrating the role of 20E in transcription initiation. At target loci, 20E depletion resulted in the malfunctioning of sites co-bound with EcR and CBP/Nejire and enriched for the H3K27Ac mark inherent to active enhancers. At these sites, the 20E concentration was found to control chromatin accessibility and acetylation. We suggest that the activity of these 'active' ecdysone-sensitive elements was responsible for the active status of 20E targets in the salivary glands of wandering larvae.
20-羟基蜕皮酮（20E）在果蝇中的转录激活为研究组织对类固醇的特异性反应提供了一个绝佳模型。20E浓度的增加在变态过程中调节幼虫组织的降解和成虫组织的增殖。为了研究20E依赖性转录，我们利用了控制20E浓度的天然系统——E23膜转运蛋白，它将20E从细胞中输出。我们在组织中人工表达E23，以抑制变态过程中第一波20E诱导的转录。E23的表达揭示了唾液腺中大量的20E依赖性基因，同时对大脑中的转录影响较小。我们描述了唾液腺中控制20E转录激活的机制。20E的耗竭降低了RNA聚合酶II（Pol II）和TFIID亚基TBP与主要靶标启动子的结合，证明了20E在转录起始中的作用。在靶基因座上，20E的耗竭导致与蜕皮激素受体（EcR）和CBP/Nejire共同结合且富含活性增强子固有H3K27Ac标记的位点功能异常。在这些位点，发现20E浓度控制染色质可及性和乙酰化。我们认为这些“活性”蜕皮激素敏感元件的活性导致了漫游幼虫唾液腺中20E靶标的活性状态。
