Department of Biochemistry, Center for Biomedical Genetics, Erasmus University Medical Center, Rotterdam, Netherlands.
Mol Cell Biol. 2010 Nov;30(21):5234-44. doi: 10.1128/MCB.00266-10. Epub 2010 Aug 23.
ATP-dependent chromatin-remodeling complexes (remodelers) are essential regulators of chromatin structure and gene transcription. How remodelers can act in a gene-selective manner has remained enigmatic. A yeast two-hybrid screen for proteins binding the Drosophila transcription factor Tramtrack69 (TTK69) identified MEP1. Proteomic characterization revealed that MEP1 is a tightly associated subunit of the NuRD remodeler, harboring the Mi2 enzymatic core ATPase. In addition, we identified the fly homolog of human Deleted in oral cancer 1 (DOC1), also known as CDK2-associated protein 1 (CDK2AP1), as a bona fide NuRD subunit. Biochemical and genetic assays supported the functional association between MEP1, Mi2, and TTK69. Genomewide expression analysis established that TTK69, MEP1, and Mi2 cooperate closely to control transcription. The TTK69 transcriptome profile correlates poorly with remodelers other than NuRD, emphasizing the selectivity of remodeler action. On the genes examined, TTK69 is able to bind chromatin in the absence of NuRD, but targeting of NuRD is dependent on TTK69. Thus, there appears to be a hierarchical relationship in which transcription factor binding precedes remodeler recruitment.
ATP 依赖的染色质重塑复合物（重塑酶）是染色质结构和基因转录的重要调节剂。重塑酶如何以基因选择性的方式发挥作用一直是个谜。一项用于筛选与果蝇转录因子 Tramtrack69（TTK69）结合的蛋白质的酵母双杂交筛选，鉴定出 MEP1。蛋白质组学分析表明，MEP1 是 NuRD 重塑酶的紧密相关亚基，含有 Mi2 酶核心 ATP 酶。此外，我们还鉴定出果蝇同源物人类口腔癌缺失蛋白 1（DOC1），也称为 CDK2 相关蛋白 1（CDK2AP1），作为真正的 NuRD 亚基。生化和遗传分析支持 MEP1、Mi2 和 TTK69 之间的功能关联。全基因组表达分析确立了 TTK69、MEP1 和 Mi2 密切合作以控制转录。TTK69 的转录组图谱与除 NuRD 以外的重塑酶相关性较差，强调了重塑酶作用的选择性。在所研究的基因上，TTK69 能够在没有 NuRD 的情况下结合染色质，但 NuRD 的靶向依赖于 TTK69。因此，似乎存在一种层次关系，其中转录因子结合先于重塑酶募集。
