A unique developmental pattern of Oct-3/4 DNA methylation is controlled by a cis-demodification element
A unique developmental pattern of Oct-3/4 DNA methylation is controlled by a cis-demodification element
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DOI：
10.1074/jbc.m203338200
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发表时间：
2002-09-13
影响因子：
4.8
通讯作者：
Bergman, Y
中科院分区：
文献类型：
--
作者：
Gidekel, S;Bergman, Y
Oct-3/4是已知在小鼠着床前发育中起关键作用的最早表达的转录因子。在这份报告中，我们询问甲基化是否参与了控制Oct-3/4表达的变化，从而可能在控制正常胚胎发育中发挥重要作用。我们发现Oct-3/4基因在囊胚期未发生甲基化，但在胎盘后6.5天经历了去甲基化，并在所有被分析的成体组织中保持修改。当其他基因，如载脂蛋白AI进行从头甲基化时，OCT-3/4在6.25天后的外胚层细胞中保持非甲基化状态。我们发现，Oct-3/4启动子序列的甲基化严重损害了其指导有效转录的能力。此外，DNA甲基化抑制了体内内源性Oct-3/4基因的基础转录。我们发现Oct-3/4基因含有一个含有近端增强子序列的顺式特异变性元件。当该序列最初甲基化时，该元件会导致胚胎癌细胞去甲基化，并在植入后的胚胎中保护局部区域免受从头开始的甲基化。这些结果表明，在胚胎保护中，甲基化不是带有CpG岛的印迹基因或管家基因的独特特征，但也适用于胚胎发育早期表达的组织特异性基因。Oct-3/4的甲基化可能类似于不活跃的X染色体上CpG岛的甲基化，这也发生在发育的后期阶段。
Oct-3/4 is the earliest expressed transcription factor that is known to be crucial in murine pre-implantation development. In this report we asked whether methylation participates in controlling changes in Oct-3/4 expression and thus may play an important role in controlling normal embryogenesis. We show that the Oct-3/4 gene is unmethylated from the blastula stage but undergoes de novo methylation at 6.5 days post-coitum and remains modified in all adult somatic tissues analyzed. Oct-3/4 remains unmethylated in 6.25 days post-coitum epiblast cells when other genes, such as apoAI, undergo de novo methylation. We show that methylation of the Oct-3/4 promoter sequence strongly compromises its ability to direct efficient transcription. Moreover, DNA methylation inhibits basal transcription of the endogenous Oct-3/4 gene in vivo. We found that the Oct-3/4 gene harbors a cis-specific demodification element that includes the proximal enhancer sequence. This element leads to demethylation in embryonal carcinoma cells when the sequence is initially methylated and protects the local region from de novo methylation in post-implantation embryos. These results indicate that in the embryo protection from de novo methylation is not a unique feature of imprinted or housekeeping genes that carry a CpG island, but is also applicable to tissue-specific genes expressed during early stages of embryogenesis. Methylation of Oct-3/4 may be analogous to methylation of CpG islands on the inactive X chromosome that also occurs at later stages of development.