Estrogen-dependent transcriptional activation and vitellogenin gene memory
Estrogen-dependent transcriptional activation and vitellogenin gene memory
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DOI：
10.1210/me.11.13.1985
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发表时间：
1997-12-01
影响因子：
--
通讯作者：
Evans, MI
中科院分区：
文献类型：
--
作者：
Edinger, RS;Mambo, E;Evans, MI
肝脏记忆的概念表明，基因对诱导剂的第二次暴露的反应比初始激活时更快。为了确定雌激素依赖性DNA/蛋白质相互作用在初级应答期间发生的速度，使用通过连接介导的PCR扩增的基因组DNA进行体内硫酸二甲酯足迹法。当雌激素被添加到来自未处理过的肝脏的破坏细胞中时，雌激素反应元件内部和周围的变化在几秒钟内发生，这表明对这种以前从未被激活的雌激素反应启动子的直接和快速影响。由于这种效果是如此之快，相对于延迟发作的mRNA积累的主要响应期间，运行的转录测定被用来确定在初级和次级响应雌激素的蛋黄蛋白基因的转录谱。与mRNA的积累一样，在初次暴露于雌激素后，所有这些基因的转录开始延迟。有趣的是，在二次暴露于雌激素后，卵黄蛋白原I、卵黄蛋白原II和极低密度载脂蛋白II基因显示出更快的转录起始，而载脂蛋白B的初级和次级转录谱对雌激素的反应是相同的。因为apoB基因在没有雌激素的情况下组成型表达，并且卵黄原蛋白在给予激素之前是静止的，所以肝记忆最可能代表了在向致力于组织特异性表达的基因的活性状态的转变中的相对稳定的事件。
The concept of hepatic memory suggests that a gene responds more rapidly to a second exposure of an inducer than it does during the initial activation. To determine how soon estrogen-dependent DNA/protein interactions occur during the primary response, in vivo dimethylsulfate footprinting was carried out using genomic DNA amplified by ligation-mediated PCR. When estrogen was added to disrupted cells from a hormone-naive liver, changes within and around the estrogen response elements occurred within seconds, indicating a direct and rapid effect on this estrogen-responsive promoter that had never before been activated. Because this effect was so rapid relative to the delayed onset of mRNA accumulation during the primary response, run-on transcription assays were used to determine the transcription profiles for four of the yolk protein genes during the primary and secondary responses to estrogen. As with the accumulation of mRNA, the onset of transcription was delayed for all of these genes after a primary exposure to estrogen. Interestingly, after the secondary exposure to estrogen, the vitellogenin I, vitellogenin II, and very low density apolipoprotein II genes displayed a more rapid onset of transcription, whereas the primary and secondary profiles of apolipoprotein B transcription in response to estrogen were identical. Because the apoB gene is constitutively expressed in the absence of estrogen, and the vitellogenins are quiescent before the administration of the hormone, hepatic memory most likely represents a relatively stable event in the transition to an active state of a gene that is committed for tissue-specific expression.