Insulator function and CTCF

我们将注意力集中在鸡β-珠蛋白基因座5端的1.2kb绝缘子DNA序列及其上游元件上，该绝缘子既能够阻断外部增强子的影响，又能够防止可能关闭整个区域表达的浓缩染色质的侵入。我们以前已经表明，增强子阻断活性与单一蛋白质CTCF与增强子内的位点结合有关。我们已经表明，这种蛋白质是负责调节印迹基因的表达在几个印迹位点。为了了解CTCF的作用机制，我们继续扩展我们早期的研究，表明CTCF分子与辅因子相互作用。 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。 在其他工作中，我们正在扩展CTCF和DEAD盒解旋酶p68之间相互作用的研究。 我们在早期的出版物中报道了这种相互作用。 我们还发现，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。

We have focused attention on the 1.2 kb insulator DNA sequence at the 5 end of the chicken beta-globin locus, and elements upstream of it. This insulator is capable both of blocking the influence of outside enhancers and of preventing the encroachment of condensed chromatin that might shut down expression of the entire region. We have shown previously that enhancer blocking activity is associated with binding of a single protein, CTCF, to a site within the enhancer. We have shown that this protein is responsible for regulation of imprinted gene expression at several imprinted loci. In order to understand the mechanism of action of CTCF we have continued to extend our earlier studies showing that CTCF molecules interact with co-factors. 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. In other work, we are extending our studies of the interaction between CTCF and the DEAD box helicase, p68. We reported this interaction in an earlier publication. We also showed 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.