多细胞真核生物中的染色体被组织成一系列拓扑独立的环,称为TAD。在苍蝇中,TAD由相邻边界之间的物理相互作用形成。飞行边界表现出不同的伴侣偏好,边界之间的配对相互作用通常取决于方向。配对可以是头对尾或头对头。前者产生一个茎环TAD,而后者给出了一个圆形循环TAD。包含果蝇甚至跳过(eve)基因的TAD是由nhomie和homie边界的头对尾配对形成的。为了探索回路拓扑与物理和监管景观之间的关系,我们在nhomie边界区域的两侧有两个attP站点。然后使用attP位点生成四个边界替换:λDNA,nhomie向前(WT方向),nhomie反向(与WT方向相反),和homie向前(与WThomie相同的方向)。nhomie前向替换恢复了WT的物理和监管格局:在MicroC实验中,EveTAD是一个火山三角形,顶部是羽状,eve基因及其调控元件与邻居的相互作用隔离开来。λDNA替换缺少边界函数:nhomie一侧的\'new\'eveTAD的端点不确定,eve条纹增强子激活附近的基因,eIF3j.当nhomie反向和homie正向恢复eveTAD时,拓扑是一个圆形回路,这改变了当地的自然和监管环境。在MicroC实验中,EveTAD与邻居互动,和顶部的羽流的前夕三角峰被转换成一对“云”的接触与隔壁的TAD。与茎环拓扑结构提供的隔离损失一致,eve增强子弱激活相邻TAD中的基因。相反,eve功能部分中断。
The chromosomes in multicellular eukaryotes are organized into a series of topologically independent loops called TADs. In flies, TADs are formed by physical interactions between neighboring boundaries. Fly boundaries exhibit distinct partner preferences, and pairing interactions between boundaries are typically orientation-dependent. Pairing can be head-to-tail or head-to-head. The former generates a stem-loop TAD, while the latter gives a circle-loop TAD. The TAD that encompasses the Drosophila even skipped (eve) gene is formed by the head-to-tail pairing of the nhomie and homie boundaries. To explore the relationship between loop topology and the physical and regulatory landscape, we flanked the nhomie boundary region with two attP sites. The attP sites were then used to generate four boundary replacements: λ DNA, nhomie forward (WT orientation), nhomie reverse (opposite of WT orientation), and homie forward (same orientation as WT homie). The nhomie forward replacement restores the WT physical and regulatory landscape: in MicroC experiments, the eve TAD is a \'volcano\' triangle topped by a plume, and the eve gene and its regulatory elements are sequestered from interactions with neighbors. The λ DNA replacement lacks boundary function: the endpoint of the \'new\' eve TAD on the nhomie side is ill-defined, and eve stripe enhancers activate a nearby gene, eIF3j. While nhomie reverse and homie forward restore the eve TAD, the topology is a circle-loop, and this changes the local physical and regulatory landscape. In MicroC experiments, the eve TAD interacts with its neighbors, and the plume at the top of the eve triangle peak is converted to a pair of \'clouds\' of contacts with the next-door TADs. Consistent with the loss of isolation afforded by the stem-loop topology, the eve enhancers weakly activate genes in the neighboring TADs. Conversely, eve function is partially disrupted.