Insulator function and CTCF

我们一直对CTCF蛋白感兴趣，几年前我们首次发现它具有绝缘体的特性，当置于增强子和启动子之间时，它会阻止它们之间的相互作用。 我们证明了这种活性在调节Igf 2/H19印迹位点的亲本来源等位基因特异性基因表达中起重要作用。 近年来的工作表明，CTCF的主要作用模式是稳定DNA上CTCF结合位点之间的相互作用，导致环结构域的形成。 根据相互作用的几何形状，这种环可以排除增强子，导致绝缘，或者使增强子和促进子更接近，导致激活。 在其他实验室的工作表明，cohesin复合物与CTCF在其许多结合位点，是必不可少的稳定远程接触和绝缘体活动涉及这些网站。 我们最近发现，与CTCF直接接触的唯一的粘附素亚基是SA 2，它位于粘附素环的外部。 我们还探讨了CTCF功能中各种生化修饰的作用。 我们最近扩展了CTCF功能的研究，确定了CTCF和DEAD盒解旋酶，p68之间的相互作用。 我们发现，与p68形成复合物的非编码RNA SRA对这种相互作用至关重要。我们现在正在研究p68-SRA相互作用的性质，以及RNA在CTCF绝缘子活性中的作用。 正在进行p68和SRA结合位点的全基因组调查。 我们还确定了其他蛋白质与SRA相互作用，可能是重要的早期发展和染色质结构的决定。

We have been interested in the protein CTCF, which we first identified some years ago as having properties of an insulator, blocking interaction between enhancers and promoters when placed between them. We demonstrated that this activity plays an important role in regulating parent of origin allele-specific gene expression at the Igf2/H19 imprinted locus. Work in recent years has shown that a principal mode of action of CTCF is to stabilize interactions between CTCF binding sites on DNA, leading to formation of loop domains. Depending on the geometry of the interactions such loops can either exclude an enhancer leading to insulation, or bring enhancer and promoter closer together, leading to activation. Work in other laboratories has shown that the cohesin complex is associated with CTCF at many of its binding sites, and is essential for stabilizing long range contacts and for insulator activity involving those sites. We have recently shown that the only cohesin subunit that makes direct contact with CTCF is SA2, which is external to the cohesin ring. We have also explored the role of various biochemical modifications in CTCF function. We have recently extended our studies of CTCF function by identifying an interaction between CTCF and the DEAD box helicase, p68. We found that a non-coding RNA, SRA, which forms a complex with p68, is essential for this interaction. We are now investigating the nature of the p68-SRA interaction, and the role of the RNA in insulator activity of CTCF. A genome-wide survey of p68 and SRA binding sites is being carried out. We have also identified other proteins that interact with SRA and may be important for early development and for chromatin structure determination.