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，我们确定了CTCF能与靶DNA位点完全结合的最小片段。我们还扩展了我们早期的研究，表明CTCF分子之间相互作用。这为设计可以调节细胞核内CTCF功能的蛋白质提供了重要信息。在早期的研究中，我们还发现CTCF与核仁蛋白核磷蛋白相互作用。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，并可能调节其功能，特别是在稳定细胞核中的远程相互作用方面

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