Insulator function and CTCF

我们将重点放在鸡β -珠蛋白位点5端1.2 kb的绝缘子DNA序列及其上游元件上。这种绝缘体既能阻断外部增强子的影响，又能防止可能关闭整个区域表达的浓缩染色质的侵入。我们之前已经证明增强子阻断活性与单个蛋白CTCF与增强子内某个位点的结合有关。我们已经证明这种蛋白在几个印迹位点上负责调控印迹基因的表达。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分子与辅助因子相互作用。

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.