Insulator function and CTCF

我们一直对CTCF蛋白感兴趣，几年前我们首次发现它具有绝缘体的特性，当置于增强子和启动子之间时，它会阻止它们之间的相互作用。我们证明了这种活性在调节Igf 2/H19印迹位点的亲本来源等位基因特异性基因表达中起重要作用。近年来在其他实验室的工作表明，CTCF的主要作用模式是募集粘附素，这反过来又稳定了DNA上CTCF结合位点之间的相互作用，导致形成环结构域。根据相互作用的几何形状，这种环可以排除增强子，导致绝缘，或者使增强子和促进子更接近，导致激活。 细胞核内的DNA被包装成染色质，并进一步组织成拓扑相关结构域（TADs），将活性和非活性基因组区域分开。TADs的建立和维持需要蛋白质CTCF，我们有兴趣鉴定和研究CTCF与蛋白质和核酸伴侣的相互作用，这些蛋白质和核酸伴侣被招募用于绝缘子功能。我们已经表明，侧面的DNA结合CTCF的11个锌指的N-和C-末端结构域似乎是本质上无序的，部分解释了大量的CTCF结合伙伴在其他研究中确定。目前的工作重点是进一步表征这些结构域的物理性质，确定高亲和力结合的伴侣，并研究形成的复合物。 我们已经确定了其他蛋白质，似乎有助于染色质组织和CTCF合作。在一种情况下，蛋白质似乎有助于稳定CTCF结合并补充其其他特性。 我们参与了一项合作研究，研究影响CTCF结合强度的SNP在与主要精神疾病相关的基因表达中的可能作用。 我们还开始了一项研究，非核糖体基因在核仁内的组织，这是解决两个基因组的内容和组织的核仁基因组。 所有这些结果都与染色质结构、组蛋白修饰和基因组在细胞功能中的长距离组织的作用有关，并且反过来与正常和异常细胞代谢和细胞分裂的问题有关。

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 other laboratories in recent years has shown that a principal mode of action of CTCF is to recruit cohesin which in turn stabilizes 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. DNA within the cell nucleus is packaged into chromatin, and further organized into topologically associated domains (TADs) separating active and inactive genomic regions. The establishment and maintenance of TADs requires the protein CTCF, and we are interested in identifying and studying the interactions of CTCF with the protein and nucleic acid partners recruited for insulator function. We have shown that the N- and C-terminal domains that flank the DNA binding 11 zinc fingers of CTCF appear to be intrinsically disordered explaining, in part, the large number of CTCF binding partners identified in other studies. Current work focuses on further characterizing the physical nature of these domains, identifying partners that bind with high affinity, and studying the complexes formed. We have identified other proteins that appear to contribute to chromatin organization and to collaborate with CTCF. In one case the protein appears to help stabilize CTCF binding and complement its other properties. We have participated in a collaboration investigating a possible role for SNPs affecting CTCF binding strength in expression of a gene associated with major mental illnesses. We have also begun a study of the organization of non-ribosomal genes within the nucleolus which is addressing both the genomic content and organization of the nucleolar genome. All of these results relate to the role of chromatin structure, histone modifications, and long range organization of the genome in cell function, and are in turn related to questions of normal and abnormal cell metabolism and cell division.