Transcriptional repression and heterochromatin formation by MBD1 and MCAF/AM family proteins
Transcriptional repression and heterochromatin formation by MBD1 and MCAF/AM family proteins
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DOI：
10.1074/jbc.m413654200
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发表时间：
2005-04-08
影响因子：
4.8
通讯作者：
Nakao, M
中科院分区：
文献类型：
--
作者：
Ichimura, T;Watanabe, S;Nakao, M
DNA甲基化与组蛋白H3（H3-K9）赖氨酸9的甲基化协同作用，形成转录沉默的染色质，H3-K9是一种被异染色质蛋白1靶向的修饰的组蛋白分子。甲基CpG结合蛋白MBD 1识别甲基化的CpG二核苷酸，并将H3-K9甲基转移酶如SETDB 1募集到基因组区域。在这里，我们表明，MBD 1含有染色质相关因子（MCAF）1，也被称为人类同源的小鼠ATFa相关的调制器（AM），是所需的转录抑制和异染色质形成MBD 1，连同参与SETDB 1。此外，MCAF 1的氨基酸序列显示出与MCAF/AM相关蛋白的许多序列的相似性，从而鉴定出该蛋白家族的新成员，称为MCAF 2。免疫沉淀和体外结合分析表明，这两个MCAF蛋白与MBD 1，SETDB 1和Sp1通过两个进化上保守的不同结构域相互作用。此外，MCAF 1增强MBD 1与SETDB 1一起的转录抑制，并且MCAF 2的外源表达部分补偿了MCAF 1敲低的HeLa细胞中的抑制活性。MBD 1突变体的表达，缺乏与MCAF蛋白的相互作用，干扰异染色质蛋白1富集的异染色质形成在MBD 1的染色体基因座。这些数据表明MBD1.MCAF1.SETDB1复合物促进异染色质结构域的形成，强调了MCAF/AM家族蛋白在表观遗传控制中的作用。
DNA methylation cooperates with methylation at lysine 9 of histone H3 (H3-K9), a modified histone molecule that is targeted by heterochromatin protein 1, to form a transcriptionally silent chromatin. Methyl CpG-binding protein MBD1 recognizes methylated CpG dinucleotide and recruits H3-K9 methyltransferases such as SETDB1 to genomic regions. Here we show that MBD1-containing chromatin-associated factor (MCAF) 1, also known as the human homologue of murine ATFa-associated modulator (AM), is required for transcriptional repression and heterochromatin formation by MBD1, together with the involvement of SETDB1. Moreover, the amino acid sequence of MCAF1 shows similarity to a number of sequences of the MCAF/AM-related proteins, resulting in the identification of a new member of the protein family, termed MCAF2. Immunoprecipitation and in vitro binding analyses reveal that both MCAF proteins interact with MBD1, SETDB1, and Sp1 via two evolutionarily conserved distinct domains. Furthermore, MCAF1 enhances transcriptional repression by MBD1 together with SETDB1, and exogenous expression of MCAF2 partly compensates for the repressive activity in MCAF1 knockdown HeLa cells. The expression of MBD1 mutant, which lacks interaction with MCAF proteins, perturbs heterochromatin protein 1-enriched heterochromatin formation at the MBD1-containing chromosomal loci. These data suggest that MBD1.MCAF1.SETDB1 complex facilitates the formation of heterochromatic domains, emphasizing the role of MCAF/AM family proteins in epigenetic control.