Mbd1 is recruited to both methylated and nonmethylated CpGs via distinct DNA binding domains
Mbd1 is recruited to both methylated and nonmethylated CpGs via distinct DNA binding domains
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DOI：
10.1128/mcb.24.8.3387-3395.2004
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发表时间：
2004-04-01
影响因子：
5.3
通讯作者：
Bird, AP
中科院分区：
文献类型：
--
作者：
Jorgensen, HF;Ben-Porath, I;Bird, AP
MBD1 是一种脊椎动物甲基 CpG 结合域蛋白 (MBD)，可以抑制甲基化启动子 DNA 序列。与其他 MBD 蛋白一样，MBD1 定位于小鼠体内富含甲基 CpG 的核灶。然而，在甲基 CpG 缺陷的小鼠细胞中，Mbd1 仍然定位于异染色质灶，而其他 MBD 蛋白则分散在细胞核中。我们发现 Mbd1a（一种主要的小鼠亚型）包含一个与非甲基化 CpG 特异性结合的 CXXC 结构域 (CXXC-3)，这为甲基化无关的定位提供了解释。转染研究表明，CXXC-3 结构域确实靶向体内非甲基化 CpG 位点。非甲基化报告基因的抑制取决于 CXXC-3 结构域，而甲基化报告基因的抑制则需要 MBD。我们的研究结果表明，MBD1 可以将 CpG 二核苷酸解释为体内抑制信号，无论其甲基化状态如何。
MBD1 is a vertebrate methyl-CpG binding domain protein (MBD) that can bring about repression of methylated promoter DNA sequences. Like other MBD proteins, MBD1 localizes to nuclear foci that in mice are rich in methyl-CpG. In methyl-CpG-deficient mouse cells, however, Mbd1 remains localized to heterochromatic foci whereas other MBD proteins become dispersed in the nucleus. We find that Mbd1a, a major mouse isoform, contains a CXXC domain (CXXC-3) that binds specifically to nonmethylated CpG, suggesting an explanation for methylation-independent localization. Transfection studies demonstrate that the CXXC-3 domain indeed targets nonmethylated CpG sites in vivo. Repression of nonmethylated reporter genes depends on the CXXC-3 domain, whereas repression of methylated reporters requires the MBD. Our findings indicate that MBD1 can interpret the CpG dinucleotide as a repressive signal in vivo regardless of its methylation status.