Insulator function and CTCF

我们一直对蛋白质CTCF感兴趣，几年前我们首次确定它具有绝缘体的特性，当放在增强剂和启动子之间时，它可以阻止增强剂和启动子之间的作用。我们证明了这种活性在调节原发源亲本的等位基因特异性基因在Igf2/H19印迹基因座上的表达中起着重要作用。近年来的工作表明，CTCF的一个主要作用模式是稳定DNA上CTCF结合位点之间的相互作用，导致环状结构域的形成。根据相互作用的几何形状，这种环可以排除导致绝缘的增强子，或者使增强子和启动子更紧密地结合在一起，导致激活。 其他实验室的工作表明，粘附素复合体在其许多结合部位与CTCF相关，对于稳定长距离接触和涉及这些部位的绝缘子活动是必不可少的。我们最近发现，唯一与CTCF直接接触的粘附素亚基是SA2，它位于粘附素环的外部。我们还探讨了各种生化修饰在CTCF功能中的作用。 最近，我们通过确定CTCF与死盒解旋酶p68之间的相互作用，扩展了我们对CTCF功能的研究。我们发现，一个非编码的RNA，SRA，它与p68形成一个复合体，是这种相互作用所必需的。我们现在正在研究p68-SRA相互作用的性质，以及RNA在CTCF绝缘体活性中的作用。目前正在对p68和SRA结合位点进行全基因组调查。我们还鉴定了与SRA相互作用的其他蛋白质，这些蛋白质对早期发育和染色质结构确定可能是重要的。

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.