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。我们之前已经证明，增强子阻断活性与单个蛋白质CTCF与增强子内位点的结合有关。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，我们确定了能够以完全亲和力结合其靶DNA位点的最小CTCF片段。我们还扩展了我们早期的研究，表明CTCF分子相互作用。 这为设计能够调节细胞核内CTCF功能的蛋白质提供了重要信息。 在早期的研究中，我们也发现CTCF与核仁蛋白nucleophosmin相互作用。我们现在正在扩展这一点，以确定哪些其他蛋白质与CTCF相互作用，并可以调节其功能，特别是在稳定核内的长程相互作用方面。

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 determined the minimum CTCF fragment that can bind to its target DNA site with full affinity. We have also extended our earlier studies showing that CTCF molecules interact with one another. This provides important information for design of proteins that can modulate CTCF function within the nucleus. In earlier studies we also showed that CTCF interacts with the nucleolar protein nucleophosmin. We are now extending this to determine what other proteins interact with CTCF and could modulate its function, particularly in stabilizing long range interactions in the nucleu