A novel Dnmt3a isoform produced from an alternative promoter localizes to euchromatin and its expression correlates with active de novo methylation
A novel Dnmt3a isoform produced from an alternative promoter localizes to euchromatin and its expression correlates with active de novo methylation
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DOI：
10.1074/jbc.m205312200
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发表时间：
2002-10-11
影响因子：
4.8
通讯作者：
Li, E
中科院分区：
文献类型：
--
作者：
Chen, TP;Ueda, Y;Li, E
先前的研究表明，Dnmt3b 基因通过选择性剪接编码多种变体。然而，迄今为止仅发现了 Dnmt3a 的一种形式。我们在此报告从人类和小鼠中发现了一种小形式的 Dnmt3a，称为 Dnmt3a2。编码 Dnmt3a2 的转录本从下游内含子启动子起始。因此，Dnmt3a2 蛋白缺少全长 Dnmt3a 的 N 端 223（人）或 219（小鼠）氨基酸残基。重组Dnmt3a2蛋白在体外表现出与Dnmt3a相似的胞嘧啶甲基转移酶活性。然而，Dnmt3a 和 Dnmt3a2 表现出显着不同的亚细胞定位模式。与集中于异染色质的 Dnmt3a 不同，Dnmt3a2 显示出暗示常染色质关联的定位模式。 Dnmt3a2 是胚胎干细胞和胚胎癌细胞中的主要形式，也可从睾丸、卵巢、胸腺和脾脏中检测到，而 Dnmt3a 普遍以低水平表达。人胚胎癌细胞系与乳腺癌/卵巢癌细胞系的比较表明 DNMT3A2 表达与高从头甲基化活性相关。这些发现表明 Dnmt3a 和 Dnmt3a2 在发育过程中可能具有不同的 DNA 靶标和不同的功能。
Previous studies have shown that the Dnmt3b gene encodes multiple variants via alternative splicing. However, only one form of Dnmt3a has been identified to date. We report here the discovery of a small form of Dnmt3a, denoted Dnmt3a2, from both human and mouse. The transcript encoding Dnmt3a2 is initiated from a downstream intronic promoter. As a result, the Dnmt3a2 protein lacks the N-terminal 223 (human) or 219 (mouse) amino acid residues of the full-length Dnmt3a. Recombinant Dnmt3a2 protein displayed similar cytosine methyltransferase activity as Dnmt3a in vitro. However, Dnmt3a and Dnmt3a2 exhibited strikingly different subcellular localization patterns. Unlike Dnmt3a, which was concentrated on heterochromatin, Dnmt3a2 displayed a localization pattern suggestive of euchromatin association. Dnmt3a2 is the predominant form in embryonic stem cells and embryonal carcinoma cells and can also be detected from testis, ovary, thymus, and spleen, whereas Dnmt3a is expressed at low levels ubiquitously. Comparison of human embryonal carcinoma cell lines with breast/ovarian cancer cell lines indicates that DNMT3A2 expression correlates with high de novo methylation activity. These findings suggest that Dnmt3a and Dnmt3a2 may have distinct DNA targets and different functions in development.