Mehta Abhishek Kumar, Majumdar Subeer S, Alam Parwez, Gulati Neerja, Brahmachari Vani
Dr. B. R. Ambedkar Center for Biomedical Research, University of Delhi, North Campus, Delhi, India.
Gene. 2009 Jan 1;428(1-2):20-4. doi: 10.1016/j.gene.2008.09.033. Epub 2008 Oct 10.
The expression of genes in transgenic mice is known to be influenced by the site of integration even when they carry their own promoter elements and transcription factor binding sites. The cytomegalovirus (CMV) promoter, a strong promoter often used for transgene expression in mammalian cells in culture, is known to be silenced by DNA methylation and histone deacetylation but there is no report on the role of histone methylations in its regulation. We generated two transgenic lines carrying green fluorescence protein coding gene as reporter driven by cytomegalovirus major immediate-early promoter/enhancer. We observe that silencing of CMV promoter is dependent on the site of transgene integration, except in testis, and the nature of DNA and histone methylations strongly correlate with the expression status of the reporter. We find that silenced CMV promoter interacts in vivo, with Methyl CpG binding protein 2 (MeCP2), a recruiter of histone deacetylases (HDACs) and histone (H3K9) methyl transferase. Histone H3K4methylation, the active chromatin mark, is also associated with silenced promoter, suggesting bivalent marking of the promoter and its susceptibility to reactivation on induction.
已知即使转基因小鼠携带自身的启动子元件和转录因子结合位点，其基因表达仍会受到整合位点的影响。巨细胞病毒（CMV）启动子是一种常用于培养的哺乳动物细胞中转基因表达的强启动子，已知会因DNA甲基化和组蛋白去乙酰化而沉默，但尚无关于组蛋白甲基化在其调控中作用的报道。我们构建了两个转基因品系，携带由巨细胞病毒主要立即早期启动子/增强子驱动的绿色荧光蛋白编码基因作为报告基因。我们观察到，除了在睾丸中，CMV启动子的沉默依赖于转基因整合位点，并且DNA和组蛋白甲基化的性质与报告基因的表达状态密切相关。我们发现沉默的CMV启动子在体内与甲基化CpG结合蛋白2（MeCP2）相互作用，MeCP2是组蛋白去乙酰化酶（HDACs）和组蛋白（H3K9）甲基转移酶的招募因子。组蛋白H3K4甲基化，即活性染色质标记，也与沉默的启动子相关，表明启动子的双价标记及其在诱导时重新激活的易感性。
