Role of CIZ1 in maintenance of epigenetic landscape in primary differentiated cells

发育中的胚胎中的细胞有能力成为成人体内所有不同类型的细胞。随着它们的专门化，它们逐渐关闭不需要的基因，直到它们只产生对其功能至关重要的产物。限制他们选择的方法之一是修改与要关闭的基因密切相关的特定蛋白质。一旦建立，这些修饰或标记必须在每次细胞分裂时复制，以便子细胞具有与其父母相同的标记，从而获得与其父母相同的基因库。我们正在研究确保标记被忠实复制的机制，即阻止细胞偏离其选择路径的“质量控制”过程。具体而言，我们感兴趣的是选择的基因和添加标记（因子）的蛋白质如何在细胞核中的大量DNA中找到彼此。这些因子是在细胞核周围扩散，直到它们碰巧遇到正确的基因，还是有一个传递系统，确保“信件”及时到达正确的“地址”？我们的实验将研究在正常细胞中，这些因子是否局限于工厂场所，限制了它们四处扩散的能力。这就意味着基因必须经过工厂才能被标记，这就可以对整个过程进行严格的控制。到目前为止，对此的研究很少，因为（我们的数据表明）对工厂的限制似乎在研究人员常用的大多数细胞类型（干细胞，癌细胞，培养细胞）中不存在或被推翻。为了了解对工厂的限制是否是体内非病变细胞的规范，有必要对新分离的细胞进行研究，这些细胞尚未适应实验室中的长期生长。通常情况下，适应细胞经历了与癌细胞相似的变化，似乎已经失去了将关键因素限制在工厂的能力。只有通过研究新分离的细胞，我们才能理解正常细胞如何维持它们对基因的选择，然后才能理解这种选择在癌症早期是如何被侵蚀的。最近，我们发现，在正常细胞中，一条测试染色体需要一种名为CIZ 1的蛋白质来i）获得关键标记，ii）短暂地从细胞核的一个位置重新定位到另一个位置。我们认为这两个观察结果是相关的，并且通过研究CIZ1的功能，我们可以确定基因向空间限制因子的靶向递送是否在体内正常细胞的细胞核内正常运作。我们的目标是利用这些结果来了解CIZ1对保持适当标记的重要性，从而防止疾病的失控和出现。我们特别关注CIZ1改变的影响（常见于几种不同类型的早期癌症），因为实验性去除CIZ1会促进培养细胞的明显趋势，使基因和因子的空间分离变得松散。

Cells in a developing embryo have the capability to become all of the different types of cell in the adult body. As they specialize they gradually turn off genes that are not required, until they only produce products that are essential to their function. One of the ways that their choice is restricted is by modification of specific proteins that are closely associated with the genes to be shut down. Once established, these modifications, or marks, must be copied each time a cell divides so that daughter cells have the same marks as their parents, and therefore access the same repertoire of genes as their parents. We are studying the mechanism that ensures marks are faithfully copied; the 'quality control' process that stops a cell from drifting away from its chosen path.Specifically, we are interested in how the chosen genes and the proteins that add the marks (factors) find each other among the mass of DNA packed into the cell nucleus. Do the factors diffuse around the nucleus until they happen to come across the correct genes, or is there a delivery system that ensures 'letters' reach the right 'address' in good time? Our experiments will look at whether, in normal cells, the factors are confined to factory sites, restricting their ability to diffuse around. This would mean that genes must visit factories to be marked, which could afford tight control over the process. So far, there has been very little investigation of this because (our data suggest) restriction to factories appears to be absent or overridden in most of the cell types that are commonly used by researchers (stem cells, cancer cells, cultured cells). In order to understand whether restriction to factories is the norm for non-diseased cells in the body, it is necessary to work with newly isolated cells that have not been adapted to long-term growth in a laboratory. Typically, adapted cells have undergone changes that are similar to changes that take place in cancer cells, and appear to have lost the ability to restrict key factors to factories. Only by studying newly isolated cells will we understand how normal cells maintain their choice of genes, and then be able to understand how this is eroded during the early stages of cancer.Recently we showed that a protein called CIZ1 is required, in normal cells, for a test chromosome to i) acquire key marks and ii) briefly relocate from one position in the nucleus to another position. We think that these two observations are linked and that, by studying the function of CIZ1 we can establish whether targeted delivery of gene to spatially restricted factor normally operates inside the nucleus of normal cells in the body. We aim to use the results to understand how important CIZ1 is to maintain appropriate marks, and so guard against loss of control and emergence of disease. We are specifically concerned with the effect of alterations in CIZ1 (common in early stage cancers of several different types), as experimental removal of CIZ1 promotes the apparent tendency of cultured cells to loosen spatial separation of gene and factor.