Mediator binds to boundaries of chromosomally interacting domains and to proteins involved in DNA looping

We have combined biochemical purification of Mediator from chromatin with ChIP-sequencing to reveal Mediator occupupancy to DNA globally and to identify proteins interacting specifically with Mediator in chromatin. We find that Mediator occupy strong chromosomally interacting domain (CID) boundaries and nearly all tRNA genes. Purification of Mediator from chromatin shows that it interacts with proteins and protein complexes that have been shown to interact with CID boundaries such as RSC, Ssu72 and histone H4. We also show specific interaction between Mediator and the Arp2/Arp3, CPF, CF 1A and LSm, complexes in chromatin. These factors are involved in mRNA 3'-end processing, gene looping, actin assembly and mRNA decay.我们将从染色质中纯化转录中介体（Mediator）的生物化学方法与染色质免疫共沉淀测序（ChIP-seq）相结合，以全局层面解析转录中介体在DNA上的结合分布，并鉴定染色质中与转录中介体特异性互作的蛋白质。我们发现，转录中介体富集于强染色体互作结构域（CID）边界以及几乎所有的tRNA基因区域。通过从染色质中纯化转录中介体，我们证实其与已被报道可与CID边界互作的蛋白质及蛋白质复合物存在相互作用，例如RSC、Ssu72以及组蛋白H4（histone H4）。此外，我们还发现染色质中转录中介体与Arp2/Arp3、CPF、CF 1A及LSm复合物存在特异性相互作用，上述因子分别参与mRNA 3'端加工、基因环化、肌动蛋白组装以及mRNA降解过程。