DNA-remethylation around a STAT5-binding enhancer in the alphaS1-casein promoter is associated with abrupt shutdown of alphaS1-casein synthesis during acute mastitis.
DNA-remethylation around a STAT5-binding enhancer in the alphaS1-casein promoter is associated with abrupt shutdown of alphaS1-casein synthesis during acute mastitis.
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发表时间：
2006
影响因子：
3.5
通讯作者：
J. Vanselow;Wei Yang;J. Herrmann;H. Zerbe;H. Schuberth;W. Petzl;W. Tomek;H. Seyfert
中科院分区：
文献类型：
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作者：
J. Vanselow;Wei Yang;J. Herrmann;H. Zerbe;H. Schuberth;W. Petzl;W. Tomek;H. Seyfert
催乳素通过激活STAT5转录因子刺激泌乳过程中乳基因的表达，这些转录因子随后结合到启动子上的同源靶序列上。在发育过程中，5methylCpG二核苷酸的去甲基化允许转录因子结合位点的组织特异性可及性，但未显示再甲基化有助于基因表达的急性抑制。我们在牛alphas1酪蛋白编码基因的远上游启动子（约-10 kbp）中鉴定了一种新的stat5结合泌乳增强子。该启动子区域仅在哺乳期乳房中低甲基化。该区域的再甲基化伴随着实验引起的完全泌乳奶牛酪蛋白合成的急性关闭，这些奶牛的乳房已经实验感染了致病性大肠杆菌菌株。在感染后24小时内，相关启动子区域从未感染对照区10%的DNA分子重甲基化到感染区约50%的DNA分子重甲基化，分别是完全泌乳和未泌乳乳房的典型值。甲基化增加导致染色质堆积更紧密。同时，在感染区，alphas1 -酪蛋白mRNA浓度下降到约50%，而蛋白质合成被关闭到约2.5%。来自非泌乳调节基因的启动子的甲基化状态没有改变，并且在亚临床金黄色葡萄球菌感染中，远端alphas1 -酪蛋白启动子没有再甲基化，其特征是持续的酪蛋白合成。因此，感染相关的alphas1酪蛋白启动子的再甲基化和染色质重塑是一种急性的、空间受限的调节机制，这可能使启动子与系统不变的高水平循环催乳素隔绝。这为CpG甲基化的急性调控意义提供了一个罕见的例子。
Prolactin stimulates the expression of milk genes during lactation through the activation of STAT5 transcription factors, which subsequently bind to their cognate target sequence on the promoters. Demethylation of 5methylCpG dinucleotides permits the tissue-specific accessibility of transcription factor-binding sites during development, but remethylation has not been shown to contribute to acute suppression of gene expression. We characterize functionally a novel STAT5-binding lactational enhancer in the far upstream promoter (approximately -10 kbp) of the bovine alphaS1-casein-encoding gene. This promoter area is hypo-methylated in the lactating udder only. Remethylation of this area accompanies an experimentally elicited acute shutdown of casein synthesis in fully lactating cows, whose udder quarters have experimentally been infected with a pathogenic E. coli strain. Within 24 h after infection, the relevant promoter area was remethylated from 10% of the DNA molecules in the uninfected control quarters to approximately 50% in the infected quarters, the typical values for fully lactating and not lactating udders respectively. Increased methylation resulted in tighter chromatin packing. Concomitantly, the alphaS1-casein mRNA concentration dropped to approximately 50% while the protein synthesis was shut down to approximately 2.5% in the infected quarters, alone. The methylation status of the promoter from a not lactationally regulated gene was unaltered, and the distal alphaS1-casein promoter was not remethylated in udder quarters with subclinical Staphylococcus aureus infections featuring sustained casein synthesis. Hence, infection-related remethylation of the alphaS1-casein promoter and chromatin remodelling serves as an acute, spatially restricted regulatory mechanism, which might insulate the promoter against the systemically unchanged high levels of circulating prolactin. This provides a rare example for an acute regulatory significance of CpG methylation.